NMN (nicotinamide mononucleotide) - NutraHacker Journal Club

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Mitochondrial Dysfunction and Therapeutic Perspectives in Cardiovascular Diseases

High mortality rates due to cardiovascular diseases (CVDs) have attracted worldwide attention. It has been reported that mitochondrial dysfunction is one of the most important mechanisms affecting the pathogenesis of CVDs. Mitochondrial DNA (mtDNA) mutations may result in impaired oxidative phosphorylation (OXPHOS), abnormal respiratory chains, and ATP production. In dysfunctional mitochondria, the electron transport chain (ETC) is uncoupled and the energy supply is reduced, while reactive oxygen species (ROS) production is increased. Here, we discussed and analyzed the relationship between mtDNA mutations, impaired mitophagy, decreased OXPHOS, elevated ROS, and CVDs from the perspective of mitochondrial dysfunction. Furthermore, we explored current potential therapeutic strategies for CVDs by eliminating mtDNA mutations (e.g., mtDNA editing and mitochondrial replacement), enhancing mitophagy, improving OXPHOS capacity (e.g., supplement with NAD+, nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), and nano-drug delivery), and reducing ROS (e.g., supplement with Coenzyme Q10 and other antioxidants), and dissected their respective advantages and limitations. In fact, some therapeutic strategies are still a long way from achieving safe and effective clinical treatment. Although establishing effective and safe therapeutic strategies for CVDs remains challenging, starting from a mitochondrial perspective holds bright prospects.

Importance of NAD+ Anabolism in Metabolic, Cardiovascular and Neurodegenerative Disorders

The role of nicotinamide adenine dinucleotide (NAD+) in ageing has emerged as a critical factor in understanding links to a wide range of chronic diseases. Depletion of NAD+, a central redox cofactor and substrate of numerous metabolic enzymes, has been detected in many major age-related diseases. However, the mechanisms behind age-associated NAD+ decline remains poorly understood. Despite limited conclusive evidence, supplements aimed at increasing NAD+ levels are becoming increasingly popular. This review provides renewed insights regarding the clinical utility and benefits of NAD+ precursors, namely nicotinamide (NAM), nicotinic acid (NA), nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), in attenuating NAD+ decline and phenotypic characterization of age-related disorders, including metabolic, cardiovascular and neurodegenerative diseases. While it is anticipated that NAD+ precursors can play beneficial protective roles in several conditions, they vary in their ability to promote NAD+ anabolism with differing adverse effects. Careful evaluation of the role of NAD+, whether friend or foe in ageing, should be considered.

NMN alleviates radiation-induced intestinal fibrosis by modulating gut microbiota

Aim: Radiation-induced intestinal fibrosis, a common complication of long-term survivors after receiving abdominal and pelvic radiotherapy, has no effective clinical drugs at present. Nicotinamide mononucleotide (NMN) has been reported to alleviate a variety of age-related diseases and has potential of regulating gut microbiota. The current study focuses on the role of gut microbiota in chronic radiation induced intestinal fibrosis, and investigates whether NMN plays a protective role in radiation-induced intestinal fibrosis as well as the impact of NMN on radiation-induced dysbiosis of gut microbiota. Materials and methods: C57BL/6J mice received 15 Gy abdominal irradiation and NMN (300 mg/kg/day) supplement in drinking water. Feces were collected at 4- and 8-months post-irradiation and performed 16S rRNA sequencing to detect the gut microbiota. Colon tissues were isolated at 12 months after irradiation with or without NMN supplementation for histological analysis. Results: We found that irradiation caused intestinal fibrosis, and altered the β diversity and composition of gut microbiota, while the gut microbiota was observed to be affected by time post-irradiation and age of mice. Long-term NMN supplementation alleviated intestinal fibrosis, and reshaped the composition and function of gut microbiota dysregulated by ionizing radiation (IR). In addition, Akkermansia muciniphila, a promising probiotic, and metabolism-related pathways, such as Biosynthesis of other secondary metabolites and Amino acid metabolism, were more abundant after NMN treatment in irradiated mice. Conclusion: IR has a long-term effect on the gut microbiota and NMN supplementation can alleviate radiation induced intestinal fibrosis by reshaping the composition of gut microbiota and regulating the metabolic function of the microorganism.

NMN Maintains Intestinal Homeostasis by Regulating the Gut Microbiota

The aim of this study was to determine the effects of long-term Nicotinamide mononucleotide (NMN) treatment on modulating gut microbiota diversity and composition, as well as its association with intestinal barrier function. In this study, C57BL/6J mice were fed different concentrations of NMN, and their feces were collected for detection of 16S rDNA and non-targeted metabolites to explore the effects of NMN on intestinal microbiota and metabolites. The results revealed that NMN increased the abundance of butyric acid-producing bacteria (Ruminococcae_UCG-014 and Prevotellaceae_NK3B31_group) and other probiotics (Akkermansia muciniphila), while the abundance of several harmful bacteria (Bilophila and Oscillibacter) were decreased after NMN treatment. Meanwhile, the level of bile acid-related metabolites in feces from the G1 group (0.1 mg/ml) was significantly increased compared to the control group, including cholic acid, taurodeoxycholic acid, taurocholic acid, glycocholic acid, and tauro-β-muricholic acid. In addition, long-term NMN treatment affected the permeability of the intestinal mucosa. The number of goblet cells and mucus thickness increased, as well as expression of tight junction protein. These results demonstrate that NMN reduced intestinal mucosal permeability and exerts a protective effect on the intestinal tract. This study lays the foundation for exploring NMN's utility in clinical research.

Treatment of inflammatory bowel disease: Potential effect of NMN on intestinal barrier and gut microbiota

Nicotinamide mononucleotide (NMN) exerts physiological effects in mammals through its conversion to nicotinamide adenine dinucleotide (NAD+). In this study, we established experimental models of colitis by mixing drinking water of C57BL/6J mice with dextran sodium sulphate (DSS), and then fed them with the same concentration of NMN or at the same time. After NMN treatment, we observed improved morphology of inflamed intestines, slightly restored length of colon, improved barrier function and reduced proinflammatory factors expression in serum. Also, significant alterations in the composition and abundance of intestinal flora in IBD mice were found. The abundance of Firmicutes, Verrucomicrobia, Akkermansia and Lactobacillus, considered as beneficial bacteria, increased, while Bacteroidetes and Muribaculaceae unclassifiably decreased. Taken together, these results suggest that NMN may improve intestinal inflammation, reduce intestinal mucosal permeability and repair gut flora dysbiosis in IBD.

NMN ameliorated radiation induced damage in NRF2-deficient cell and mice via regulating SIRT6 and SIRT7

Risk of cancer often increases with aging, and radiotherapy is an essential component of treatment. As for abdominal and pelvic cancer, radiotherapy always inevitably causes injury to intestines through direct DNA damage or overload of reactive oxygen species (ROS). Nuclear factor erythroid 2-related factor 2 (NRF2) has been identified as a key protective factor against ionizing-radiation induced damage through promoting DNA damage repair and antioxidant modulation. However, the level of NRF2 always decreases with aging. Here, we demonstrated that NRF2 deficiency aggravated cellular DNA damage and the intestinal pathological lesion. Overexpression of SIRT6 or SIRT7 could improve cell proliferation and protect against radiation injury in NRF2 knock-out (KO) cells by modulating oxidative-stress and DNA damage repair. Consistently, supplement of nicotinamide mononucleotide (NMN), the agonist of sirtuins, increased the level of SIRT6 and SIRT7 in NRF2 KO cells, concomitant with reduced cellular ROS level and ameliorated DNA damage. In vivo, long-term oral administration of NMN attenuated the radiation-induced injury of jejunum, increased the number of intestinal stem cells, and promoted the ability of intestinal proliferation in NRF2-/- mice. Together, our results indicated that SIRT6 and SIRT7 had involved in scavenging ROS and repairing DNA damage, and NMN could be a promising candidate for preventing radiation damage when NRF2 is lacking.

Safety evaluation of β-nicotinamide mononucleotide oral administration in healthy adult men and women

A decrease in the intracellular level of nicotinamide adenine dinucleotide (NAD+), an essential coenzyme for metabolic activity, causes various age-related diseases and metabolic abnormalities. Both in-vivo and in-vitro studies have shown that increasing certain NAD+ levels in cell or tissue by supplementing nicotinamide mononucleotide (NMN), a precursor of NAD+, alleviates age-related diseases and metabolic disorders. In recent years, several clinical trials have been performed to elucidate NMN efficacy in humans. However, previous clinical studies with NMN have not reported on the safety of repeated daily oral administration of ≥ 1000 mg/shot in healthy adult men and women, and human clinical trials on NMN safety are limited. Therefore, we conducted a randomized, double-blind, placebo-controlled, parallel-group study to evaluate the safety of 1250 mg of β-NMN administered orally once daily for up to 4 weeks in 31 healthy adult men and women aged 20-65 years. Oral administration of β-NMN did not result in changes exceeding physiological variations in multiple clinical trials, including anthropometry, hematological, biochemical, urine, and body composition analyses. Moreover, no severe adverse events were observed during the study period. Our results indicate that β-NMN is safe and well-tolerated in healthy adult men and women an oral dose of 1250 mg once daily for up to 4 weeks.Trial registration Clinicaltrials.gov Identifier: UMIN000043084. Registered 21/01/2021. https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000049188 .

Oral Administration of Nicotinamide Mononucleotide Is Safe and Efficiently Increases Blood Nicotinamide Adenine Dinucleotide Levels in Healthy Subjects

Nicotinamide mononucleotide (NNM) is an orally bioavailable NAD+ precursor that has demonstrated beneficial effects against aging and aging-associated diseases in animal models. NMN is ultimately converted to NAD+, a redox cofactor that mediates many metabolic enzymes. NAD+ also serves as the substrate for poly(ADP-ribose) polymerase (PARP) and sirtuins, and regulates various biological processes, such as metabolism, DNA repair, gene expression, and stress responses. Previous mouse models showed that NMN administration can increase NAD+ in various organs and ameliorate aging-related diseases, such as obesity, diabetes, heart failure, stroke, kidney failure, and Alzheimer's disease through NAD+-mediated pathways. However, evidence of its effect on humans is still scarce. In this study, we conducted a placebo-controlled, randomized, double blind, parallel-group trial to investigate the safety of orally administered NMN and its efficacy to increase NAD+ levels in thirty healthy subjects. Healthy volunteers received 250 mg/day of NMN (n = 15) or placebo (n = 15) for 12 weeks, and physiological and laboratory tests were performed during this period. In addition, NAD+ and its related metabolites in whole blood were examined. Oral supplementation of NMN for 12 weeks caused no abnormalities in physiological and laboratory tests, and no obvious adverse effects were observed. NAD+ levels in whole blood were significantly increased after NMN administration. We also observed the significant rise in nicotinic acid mononucleotide (NAMN) levels, but not in NMN. We also found that the increased amount of NAD+ was strongly correlated with pulse rate before the administration of NMN. These results suggest that oral administration of NMN is a safe and practical strategy to boost NAD+ levels in humans. Clinical Trial Registration: JRCT [https://jrct.niph.go.jp/], identifier: [jRCTs041200034].

Nicotinamide Mononucleotide: A Promising Molecule for Therapy of Diverse Diseases by Targeting NAD+ Metabolism

NAD+, a co-enzyme involved in a great deal of biochemical reactions, has been found to be a network node of diverse biological processes. In mammalian cells, NAD+ is synthetized, predominantly through NMN, to replenish the consumption by NADase participating in physiologic processes including DNA repair, metabolism, and cell death. Correspondingly, aberrant NAD+ metabolism is observed in many diseases. In this review, we discuss how the homeostasis of NAD+ is maintained in healthy condition and provide several age-related pathological examples related with NAD+ unbalance. The sirtuins family, whose functions are NAD-dependent, is also reviewed. Administration of NMN surprisingly demonstrated amelioration of the pathological conditions in some age-related disease mouse models. Further clinical trials have been launched to investigate the safety and benefits of NMN. The NAD+ production and consumption pathways including NMN are essential for more precise understanding and therapy of age-related pathological processes such as diabetes, ischemia-reperfusion injury, heart failure, Alzheimer's disease, and retinal degeneration.

Nicotinamide Mononucleotide: Exploration of Diverse Therapeutic Applications of a Potential Molecule

Nicotinamide mononucleotide (NMN) is a nucleotide that is most recognized for its role as an intermediate of nicotinamide adenine dinucleotide (NAD+) biosynthesis. Although the biosynthetic pathway of NMN varies between eukaryote and prokaryote, two pathways are mainly followed in case of eukaryotic human-one is through the salvage pathway using nicotinamide while the other follows phosphorylation of nicotinamide riboside. Due to the unavailability of a suitable transporter, NMN enters inside the mammalian cell in the form of nicotinamide riboside followed by its subsequent conversion to NMN and NAD+. This particular molecule has demonstrated several beneficial pharmacological activities in preclinical studies, which suggest its potential therapeutic use. Mostly mediated by its involvement in NAD+ biosynthesis, the pharmacological activities of NMN include its role in cellular biochemical functions, cardioprotection, diabetes, Alzheimer's disease, and complications associated with obesity. The recent groundbreaking discovery of anti-ageing activities of this chemical moiety has added a valuable essence in the research involving this molecule. This review focuses on the biosynthesis of NMN in mammalian and prokaryotic cells and mechanism of absorption along with the reported pharmacological activities in murine model.

Reversal of endothelial dysfunction by nicotinamide mononucleotide via extracellular conversion to nicotinamide riboside

Background: Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are effective substrates for NAD synthesis, which may act as vasoprotective agents. Here, we characterize the effects of NMN and NR on endothelial inflammation and dysfunction and test the involvement of CD73 in these effects. Materials and methods: The effect of NMN and NR on IL1β- or TNFα-induced endothelial inflammation (ICAM1 and vWF expression), intracellular NAD concentration and NAD-related enzyme expression (NAMPT, CD38, CD73), were studied in HAECs. The effect of NMN and NR on angiotensin II-induced impairment of endothelium-dependent vasodilation was analyzed in murine aortic rings. The involvement of CD73 in NMN and NR effects was tested using CD73 inhibitor-AOPCP, or CD73-/- mice. Results: 24 h-incubation with NMN and NR induced anti-inflammatory effects in HAEC stimulated by IL1β or TNFα, as evidenced by a reduction in ICAM1 and vWF expression. Effects of exogenous NMN but not NR was abrogated in the presence of AOPCP, that efficiently inhibited extracellular endothelial conversion of NMN to NR, without a significant effect on the metabolism of NMN to NA. Surprisingly, intracellular NAD concentration increased in HAEC stimulated by IL1β or TNFα and this effect was associated with upregulation of NAMPT and CD73, whereas changes in CD38 expression were less pronounced. NMN and NR further increased NAD in IL1β-stimulated HAECs and AOPCP diminished NMN-induced increase in NAD, without an effect on NR-induced response. In ex vivo aortic rings stimulated with angiotensin II for 24 h, NO-dependent vasorelaxation induced by acetylcholine was impaired. NMN and NR, both prevented Ang II-induced endothelial dysfunction in the aorta. In aortic rings taken from CD73-/- mice NMN effect was lost, whereas NR effect was preserved. Conclusion: NMN and NR modulate intracellular NAD content in endothelium, inhibit endothelial inflammation and improve NO-dependent function by CD73-dependent and independent pathways, respectively. Extracellular conversion of NMN to NR by CD73 localized in the luminal surface of endothelial cells represent important vasoprotective mechanisms to maintain intracellular NAD.

Long-Term Administration of Nicotinamide Mononucleotide Mitigates Age-Associated Physiological Decline in Mice

NAD+ availability decreases with age and in certain disease conditions. Nicotinamide mononucleotide (NMN), a key NAD+ intermediate, has been shown to enhance NAD+ biosynthesis and ameliorate various pathologies in mouse disease models. In this study, we conducted a 12-month-long NMN administration to regular chow-fed wild-type C57BL/6N mice during their normal aging. Orally administered NMN was quickly utilized to synthesize NAD+ in tissues. Remarkably, NMN effectively mitigates age-associated physiological decline in mice. Without any obvious toxicity or deleterious effects, NMN suppressed age-associated body weight gain, enhanced energy metabolism, promoted physical activity, improved insulin sensitivity and plasma lipid profile, and ameliorated eye function and other pathophysiologies. Consistent with these phenotypes, NMN prevented age-associated gene expression changes in key metabolic organs and enhanced mitochondrial oxidative metabolism and mitonuclear protein imbalance in skeletal muscle. These effects of NMN highlight the preventive and therapeutic potential of NAD+ intermediates as effective anti-aging interventions in humans.

Nicotinamide mononucleotide protects against β-amyloid oligomer-induced cognitive impairment and neuronal death

Amyloid-β (Aβ) oligomers are recognized as the primary neurotoxic agents in Alzheimer's disease (AD). Impaired brain energy metabolism and oxidative stress are implicated in cognitive decline in AD. Nicotinamide adenine dinucleotide (NAD(+)), a coenzyme involved in redox activities in the mitochondrial electron transport chain, has been identified as a key regulator of the lifespan-extending effects, and the activation of NAD(+) expression has been linked with a decrease in Aβ toxicity in AD. One of the key precursors of NAD(+) is nicotinamide mononucleotide (NMN), a product of the nicotinamide phosphoribosyltransferase reaction. To determine whether improving brain energy metabolism will forestall disease progress in AD, the impact of the NAD(+) precursor NMN on Aβ oligomer-induced neuronal death and cognitive impairment were studied in organotypic hippocampal slice cultures (OHCs) and in a rat model of AD. Treatment of intracerebroventricular Aβ oligomer infusion AD model rats with NMN (500mg/kg, intraperitoneally) sustained improvement in cognitive function as assessed by the Morris water maze. In OHCs, Aβ oligomer-treated culture media with NMN attenuated neuronal cell death. NMN treatment also significantly prevented the Aβ oligomer-induced inhibition of LTP. Furthermore, NMN restored levels of NAD(+) and ATP, eliminated accumulation of reactive oxygen species (ROS) in the Aβ oligomer-treated hippocampal slices. All these protective effects were reversed by 3-acetylpyridine, which generates inactive NAD(+). The present study indicates that NMN could restore cognition in AD model rats. The beneficial effect of NMN is produced by ameliorating neuron survival, improving energy metabolism and reducing ROS accumulation. These results suggest that NMN may become a promising therapeutic drug for AD.

Nicotinamide Mononucleotide Administration Prevents Experimental Diabetes-Induced Cognitive Impairment and Loss of Hippocampal Neurons

Diabetes predisposes to cognitive decline leading to dementia and is associated with decreased brain NAD+ levels. This has triggered an intense interest in boosting nicotinamide adenine dinucleotide (NAD+) levels to prevent dementia. We tested if the administration of the precursor of NAD+, nicotinamide mononucleotide (NMN), can prevent diabetes-induced memory deficits. Diabetes was induced in Sprague-Dawley rats by the administration of streptozotocin (STZ). After 3 months of diabetes, hippocampal NAD+ levels were decreased (p = 0.011). In vivo localized high-resolution proton magnetic resonance spectroscopy (MRS) of the hippocampus showed an increase in the levels of glucose (p < 0.001), glutamate (p < 0.001), gamma aminobutyric acid (p = 0.018), myo-inositol (p = 0.018), and taurine (p < 0.001) and decreased levels of N-acetyl aspartate (p = 0.002) and glutathione (p < 0.001). There was a significant decrease in hippocampal CA1 neuronal volume (p < 0.001) and neuronal number (p < 0.001) in the Diabetic rats. Diabetic rats showed hippocampal related memory deficits. Intraperitoneal NMN (100 mg/kg) was given after induction and confirmation of diabetes and was provided on alternate days for 3 months. NMN increased brain NAD+ levels, normalized the levels of glutamate, taurine, N-acetyl aspartate (NAA), and glutathione. NMN-treatment prevented the loss of CA1 neurons and rescued the memory deficits despite having no significant effect on hyperglycemic or lipidemic control. In hippocampal protein extracts from Diabetic rats, SIRT1 and PGC-1α protein levels were decreased, and acetylation of proteins increased. NMN treatment prevented the diabetes-induced decrease in both SIRT1 and PGC-1α and promoted deacetylation of proteins. Our results indicate that NMN increased brain NAD+, activated the SIRT1 pathway, preserved mitochondrial oxidative phosphorylation (OXPHOS) function, prevented neuronal loss, and preserved cognition in Diabetic rats.

Role of mitochondria in diabetic peripheral neuropathy: Influencing the NAD+-dependent SIRT1-PGC-1α-TFAM pathway

Survival of human peripheral nervous system neurons and associated distal axons is highly dependent on energy. Diabetes invokes a maladaptation in glucose and lipid energy metabolism in adult sensory neurons, axons and Schwann cells. Mitochondrial (Mt) dysfunction has been implicated as an etiological factor in failure of energy homeostasis that results in a low intrinsic aerobic capacity within the neuron. Over time, this energy failure can lead to neuronal and axonal degeneration and results in increased oxidative injury in the neuron and axon. One of the key pathways that is impaired in diabetic peripheral neuropathy (DPN) is the energy sensing pathway comprising the nicotinamide-adenine dinucleotide (NAD+)-dependent Sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor-γ coactivator α (PGC-1α)/Mt transcription factor A (TFAM or mtTFA) signaling pathway. Knockout of PGC-1α exacerbates DPN, whereas overexpression of human TFAM is protective. LY379268, a selective metabolomic glutamate receptor 2/3 (mGluR2/3) receptor agonist, also upregulates the SIRT1/PGC-1α/TFAM signaling pathway and prevents DPN through glutamate recycling in Schwann/satellite glial (SG) cells and by improving dorsal root ganglion (DRG) neuronal Mt function. Furthermore, administration of nicotinamide riboside (NR), a precursor of NAD+, prevents and reverses DPN, in part by increasing NAD+ levels and SIRT1 activity. In summary, we review the role of NAD+, mitochondria and the SIRT1-PGC-1α-TFAM pathway both from the perspective of pathogenesis and therapy in DPN.

NAD+ Precursors Repair Mitochondrial Function in Diabetes and Prevent Experimental Diabetic Neuropathy

Axon degeneration in diabetic peripheral neuropathy (DPN) is associated with impaired NAD+ metabolism. We tested whether the administration of NAD+ precursors, nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), prevents DPN in models of Type 1 and Type 2 diabetes. NMN was administered to streptozotocin (STZ)-induced diabetic rats and STZ-induced diabetic mice by intraperitoneal injection at 50 or 100 mg/kg on alternate days for 2 months. mice The were fed with a high fat diet (HFD) for 2 months with or without added NR at 150 or 300 mg/kg for 2 months. The administration of NMN to STZ-induced diabetic rats or mice or dietary addition of NR to HFD-fed mice improved sensory function, normalized sciatic and tail nerve conduction velocities, and prevented loss of intraepidermal nerve fibers in skin samples from the hind-paw. In adult dorsal root ganglion (DRG) neurons isolated from HFD-fed mice, there was a decrease in NAD+ levels and mitochondrial maximum reserve capacity. These impairments were normalized in isolated DRG neurons from NR-treated mice. The results indicate that the correction of NAD+ depletion in DRG may be sufficient to prevent DPN but does not significantly affect glucose tolerance, insulin levels, or insulin resistance.

NAD+ improves cognitive function and reduces neuroinflammation by ameliorating mitochondrial damage and decreasing ROS production in chronic cerebral hypoperfusion models through Sirt1/PGC-1α pathway

Background: Microglial-mediated neuroinflammation plays an important role in vascular dementia, and modulating neuroinflammation has emerged as a promising treatment target. Nicotinamide adenine dinucleotide (NAD+) shows anti-inflammatory and anti-oxidant effects in many neurodegenerative disease models, but its role in the chronic cerebral hypoperfusion (CCH) is still unclear. Methods: The bilateral common carotid artery occlusion (BCCAO) was performed to establish CCH models in Sprague-Dawley rats. The rats were given daily intraperitoneal injection of NAD+ for 8 weeks. The behavioral test and markers for neuronal death and neuroinflammation were analyzed. Mitochondrial damage and ROS production in microglia were also assessed. RNA-seq was performed to investigate the mechanistic pathway changes. For in vitro studies, Sirt1 was overexpressed in BV2 microglial cells to compare with NAD+ treatment effects on mitochondrial injury and neuroinflammation. Results: NAD+ administration rescued cognitive deficits and inhibited neuroinflammation by protecting mitochondria and decreasing ROS production in CCH rats. Results of mechanistic pathway analysis indicated that the detrimental effects of CCH might be associated with decreased gene expression of PPAR-γ co-activator1α (PGC-1α) and its upstream transcription factor Sirt1, while NAD+ treatment markedly reversed their decrease. In vitro study confirmed that NAD+ administration had protective effects on hypoxia-induced neuroinflammation and mitochondrial damage, as well as ROS production in BV2 microglia via Sirt1/PGC-1α pathway. Sirt1 overexpression mimicked the protective effects of NAD+ treatment in BV2 microglia. Conclusions: NAD+ ameliorated cognitive impairment and dampened neuroinflammation in CCH models in vivo and in vitro, and these beneficial effects were associated with mitochondrial protection and ROS inhibition via activating Sirt1/PGC-1α pathway.

Pre-emptive Short-term Nicotinamide Mononucleotide Treatment in a Mouse Model of Diabetic Nephropathy

Background: The activation of NAD+-dependent deacetylase, Sirt1, by the administration of nicotinamide mononucleotide (NMN) ameliorates various aging-related diseases. Methods: Diabetic db/db mice were treated with NMN transiently for 2 weeks and observed for effects on diabetic nephropathy (DN). Results: At 14 weeks after the treatment period, NMN attenuated the increases in urinary albumin excretion in db/db mice without ameliorating hemoglobin A1c levels. Short-term NMN treatment mitigated mesangium expansion and foot process effacement, while ameliorating decreased Sirt1 expression and increased claudin-1 expression in the kidneys of db/db mice. This treatment also improved the decrease in the expression of H3K9me2 and DNMT1. Short-term NMN treatment also increased kidney concentrations of NAD+ and the expression of Sirt1 and nicotinamide phosphoribosyltransferase (Nampt), and it maintained nicotinamide mononucleotide adenyltransferase1 (Nmnat1) expression in the kidneys. In addition, survival rates improved after NMN treatment. Conclusions: Short-term NMN treatment in early-stage DN has remote renal protective effects through the upregulation of Sirt1 and activation of the NAD+ salvage pathway, both of which indicate NMN legacy effects on DN.

Nicotinamide mononucleotide, an intermediate of NAD+ synthesis, protects the heart from ischemia and reperfusion

Nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme for nicotinamide adenine dinucleotide (NAD+) synthesis, and Sirt1, an NAD+-dependent histone deacetylase, protect the heart against ischemia/reperfusion (I/R). It remains unknown whether Nampt mediates the protective effect of ischemic preconditioning (IPC), whether nicotinamide mononucleotide (NMN, 500 mg/kg), a product of Nampt in the NAD+ salvage pathway, mimics the effect of IPC, or whether caloric restriction (CR) upregulates Nampt and protects the heart through a Sirt1-dependent mechanism. IPC upregulated Nampt protein, and the protective effect of IPC against ischemia (30 minutes) and reperfusion (24 hours) was attenuated at both early and late phases in Nampt +/- mice, suggesting that Nampt plays an essential role in mediating the protective effect of IPC. In order to mimic the effect of Nampt, NMN was administered by intraperitoneal injection. NMN significantly increased the level of NAD+ in the heart at baseline and prevented a decrease in NAD+ during ischemia. NMN protected the heart from I/R injury when it was applied once 30 minutes before ischemia or 4 times just before and during reperfusion, suggesting that exogenous NMN protects the heart from I/R injury in both ischemic and reperfusion phases. The protective effect of NMN was accompanied by decreases in acetylation of FoxO1, but it was not obvious in Sirt1 KO mice, suggesting that the effect of NMN is mediated through activation of Sirt1. Compared to control diet (90% calories), CR (60% calories for 6 weeks) in mice led to a significant reduction in I/R injury, accompanied by upregulation of Nampt. The protective effect of CR against I/R injury was not significant in cardiac-specific Sirt1 KO mice, suggesting that the protective effect of CR is in part mediated through the Nampt-Sirt1 pathway. In conclusion, exogenous application of NMN and CR protects the heart by both mimicking IPC and activating Sirt1.

Targeting Nicotinamide Phosphoribosyltransferase as a Potential Therapeutic Strategy to Restore Adult Neurogenesis

Adult neurogenesis is the process of generating new neurons throughout life in the olfactory bulb and hippocampus of most mammalian species, which is closely related to aging and disease. Nicotinamide phosphoribosyltransferase (NAMPT), also an adipokine known as visfatin, is the rate-limiting enzyme for mammalian nicotinamide adenine dinucleotide (NAD) salvage synthesis by generating nicotinamide mononucleotide (NMN) from nicotinamide. Recent findings from our laboratory and other laboratories have provided much evidence that NAMPT might serve as a therapeutic target to restore adult neurogenesis. NAMPT-mediated NAD biosynthesis in neural stem/progenitor cells is important for their proliferation, self-renewal, and formation of oligodendrocytes in vivo and in vitro. Therapeutic interventions by the administration of NMN, NAD, or recombinant NAMPT are effective for restoring adult neurogenesis in several neurological diseases. We summarize adult neurogenesis in aging, ischemic stroke, traumatic brain injury, and neurodegenerative disease and review the advances of targeting NAMPT in restoring neurogenesis. Specifically, we provide emphasis on the P7C3 family, a class of proneurogenic compounds that are potential NAMPT activators, which might shed light on future drug development in neurogenesis restoration.

Nicotinamide mononucleotide administration after sever hypoglycemia improves neuronal survival and cognitive function in rats

Hypoglycemia-induced brain injury is a potential complication of insulin therapy in diabetic patients. Severe hypoglycemia triggers a cascade of events in vulnerable neurons that may lead to neuronal death and cognitive impairment even after glucose normalization. Oxidative stress and the activation of poly (ADP-ribose) polymerase-1 (PARP-1) are key events in this cascade. The production of reactive oxygen species (ROS) induces DNA damage and the consequent PARP-1 activation, which depletes NAD+ and ATP, resulting in brain injury. One of the key precursors of NAD+ is nicotinamide mononucleotide (NMN), which is converted to NAD+ and reduces production of ROS. Here we investigated whether NMN could reduce brain injury after severe hypoglycemia. We used a rat model of insulin-induced severe hypoglycemia and injected NMN (500 mmg/kg, i.p., one week) following 30 min of severe hypoglycemia, at the time of glucose administration. One week after severe hypoglycemia, hippocampal long-term potentiation (LTP), an electrophysiogic assay of synaptic plasticity, was examined and neuronal damage was assessed by Hematoxylin-Eosin staining. ROS accumulation, PARP-1 activation, NAD+ and ATP levels in hippocampus were also measured. Cognitive function was assessed using the Morris water maze 6 weeks after severe hypoglycemia. The addition of NMN reduced neuron death by 83 ± 3% (P < 0.05) after severe hypoglycemia. The hippocampal LTP was significantly reduced by severe hypoglycemia but showed recovery in the NMN addition group. NMN treatment also attenuated the severe hypoglycemia-induced spatial learning and memory impairment. Mechanically, we showed that NMN administration decreased ROS accumulation, suppressed PARP-1 activation, and restored levels of NAD+ and ATP in hippocampus. All these protective effects were reversed by 3-acetylpyridine (3-AP), which generates inactive NAD+. In summary, NMN administration following severe hypoglycemia could ameliorate neuronal damage and cognitive impairment caused by severe hypoglycemia. These results suggest that NMN may be a promising therapeutic drug to prevent hypoglycemia-induced brain injury.

Recent Neurotherapeutic Strategies to Promote Healthy Brain Aging: Are we there yet?

Owing to the global exponential increase in population ageing, there is an urgent unmet need to develop reliable strategies to slow down and delay the ageing process. Age-related neurodegenerative diseases are among the main causes of morbidity and mortality in our contemporary society and represent a major socio-economic burden. There are several controversial factors that are thought to play a causal role in brain ageing which are continuously being examined in experimental models. Among them are oxidative stress and brain inflammation which are empirical to brain ageing. Although some candidate drugs have been developed which reduce the ageing phenotype, their clinical translation is limited. There are several strategies currently in development to improve brain ageing. These include strategies such as caloric restriction, ketogenic diet, promotion of cellular nicotinamide adenine dinucleotide (NAD+) levels, removal of senescent cells, 'young blood' transfusions, enhancement of adult neurogenesis, stem cell therapy, vascular risk reduction, and non-pharmacological lifestyle strategies. Several studies have shown that these strategies can not only improve brain ageing by attenuating age-related neurodegenerative disease mechanisms, but also maintain cognitive function in a variety of pre-clinical experimental murine models. However, clinical evidence is limited and many of these strategies are awaiting findings from large-scale clinical trials which are nascent in the current literature. Further studies are needed to determine their long-term efficacy and lack of adverse effects in various tissues and organs to gain a greater understanding of their potential beneficial effects on brain ageing and health span in humans.

Resolving Geroplasticity to the Balance of Rejuvenins and Geriatrins

According to the cell centric hypotheses, the deficits that drive aging occur within cells by age dependent progressive damage to organelles, telomeres, biologic signaling pathways, bioinformational molecules, and by exhaustion of stem cells. Here, we amend these hypotheses and propose an eco-centric model for geroplasticity (aging plasticity including aging reversal). According to this model, youth and aging are plastic and require constant maintenance, and, respectively, engage a host of endogenous rejuvenating (rejuvenins) and gero-inducing [geriatrin] factors. Aging in this model is akin to atrophy that occurs as a result of damage or withdrawal of trophic factors. Rejuvenins maintain and geriatrins adversely impact cellular homeostasis, cell fitness, and proliferation, stem cell pools, damage response and repair. Rejuvenins reduce and geriatrins increase the age-related disorders, inflammatory signaling, and senescence and adjust the epigenetic clock. When viewed through this perspective, aging can be successfully reversed by supplementation with rejuvenins and by reducing the levels of geriatrins.

NAD+ Therapeutics and Skeletal Muscle Adaptation to Exercise in Humans

Nicotinamide adenine dinucleotide (NAD+) is a vital energy intermediate in skeletal muscle. The discovery of dietary-derived NAD+ precursors has led to the rapid development of NAD+ therapeutics designed to manipulate NAD+ content in target tissues. Of those developed, nicotinamide riboside and nicotinamide mononucleotide have been reported to display health benefit in humans under clinical scenarios of NAD+ deficiency. In contrast, relatively little is known regarding the potential benefit of nicotinamide riboside and nicotinamide mononucleotide supplementation in healthy individuals, with questions remaining as to whether NAD+ therapeutics can be used to support training adaptation or improve performance in athletic populations. Examining animal and human nicotinamide riboside supplementation studies, this review discusses current evidence suggesting that NAD+ therapeutics do not alter skeletal muscle metabolism or improve athletic performance in healthy humans. Further, we will highlight potential reasons why nicotinamide riboside supplementation studies do not translate to healthy populations and discuss the futility of testing NAD+ therapeutics outside of the clinical populations where NAD+ deficiency is present.

Precursor comparisons for the upregulation of nicotinamide adenine dinucleotide. Novel approaches for better aging

Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in every human cell and regulates a number of systems across multiple cellular compartments and tissue types via an endogenous and exogenous influence. NAD levels are demonstrated to decline with age and therefore measures to counteract the waning of NAD have been devised. A number of NAD precursor candidates such as nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), the reduced form of nicotinamide mononucleotide (NMNH), nicotinic acid (NA) nicotinamide (NAM), and dihydronicotinamide riboside (DNR) increase NAD levels in vitro and in vivo. This discussion will focus on the precursors NR, NMN, NMNH, and DNR in the upregulation of NAD. There are many publications on NAD precursors as it has become popular for human consumption in recent years due to its vital importance to the general consumer. However, there is no consensus between researchers and this was the aim of this review, to determine and discuss their areas of agreement versus disagreement, to highlight the gaps in research, and to give recommendations for future work. Bioavailability and potency of NR, NMNH, NMN, and DNR is also examined on the light of the most recent literature.

Diet and Nutraceuticals for Mental and Physical Performance in Athletes

Neuroprotective Role of Nutritional Supplementation in Athletes

Background: Neurodegenerative disorders belong to different classes of progressive/ chronic conditions that affect the peripheral/central nervous system. It has been shown through studies that athletes who play sports involving repeated head trauma and sub-concussive impacts are more likely to experience neurological impairments and neurodegenerative disorders in the long run Aims: The aim of the current narrative review article is to provide a summary of various nutraceuticals that offer promise in the prevention or management of sports-related injuries, especially concussions and mild traumatic brain injuries. Methods: This article reviews the various potential nutraceutical agents and their possible mechanisms in providing a beneficial effect in the injury recovery process. A thorough survey of the literature was carried out in the relevant databases to identify studies published in recent years. In the present article, we have also highlighted the major neurological disorders along with the associated nutraceutical(s) therapy in the management of disorders. Results: The exact pathological mechanism behind neurodegenerative conditions is complex as well as idiopathic. However, mitochondrial dysfunction, oxidative stress as well as intracellular calcium overload are some common reasons responsible for the progression of these neurodegenerative disorders. Owing to the multifaceted effects of nutraceuticals (complementary medicine), these supplements have gained importance as neuroprotective. These diet-based approaches inhibit different pathways in a physiological manner without eliciting adverse effects. Food habits and lifestyle of an individual also affect neurodegeneration. Conclusion: Studies have shown nutraceuticals (such as resveratrol, omega-3-fatty acids) to be efficacious in terms of their neuroprotection against several neurodegenerative disorders and to be used as supplements in the management of traumatic brain injuries. Protection prior to injuries is needed since concussions or sub-concussive impacts may trigger several pathophysiological responses or cascades that can lead to long-term complications associated with CNS. Thus, the use of nutraceuticals as prophylactic treatment for neurological interventions has been proposed.

Protection Before Impact: the Potential Neuroprotective Role of Nutritional Supplementation in Sports-Related Head Trauma

Even in the presence of underreporting, sports-related concussions/mild traumatic brain injuries (mTBI) are on the rise. In the absence of proper diagnosis, an athlete may return to play prior to full recovery, increasing the risk of second-impact syndrome or protracted symptoms. Recent evidence has demonstrated that sub-concussive impacts, those sustained routinely in practice and competition, result in a quantifiable pathophysiological response and the accumulation of both concussive and sub-concussive impacts sustained over a lifetime of sports participation may lead to long-term neurological impairments and an increased risk of developing neurodegenerative diseases. The pathophysiological, neurometabolic, and neurochemical cascade that initiates subsequent to the injury is complex and involves multiple mechanisms. While pharmaceutical treatments may target one mechanism, specific nutrients and nutraceuticals have been discovered to impact several pathways, presenting a broader approach. Several studies have demonstrated the neuroprotective effect of nutritional supplementation in the treatment of mTBI. However, given that many concussions go unreported and sub-concussive impacts result in a pathophysiological response that, too, may contribute to long-term brain health, protection prior to impact is warranted. This review discusses the current literature regarding the role of nutritional supplements that, when provided before mTBI and traumatic brain injury, may provide neurological protection.

Elucidating the Multi-Targeted Role of Nutraceuticals: A Complementary Therapy to Starve Neurodegenerative Diseases

The mechanisms underlying multifactorial diseases are always complex and challenging. Neurodegenerative disorders (NDs) are common around the globe, posing a critical healthcare issue and financial burden to the country. However, integrative evidence implies some common shared mechanisms and pathways in NDs, which include mitochondrial dysfunction, neuroinflammation, oxidative stress, intracellular calcium overload, protein aggregates, oxidative stress (OS), and neuronal destruction in specific regions of the brain, owing to multifaceted pathologies. The co-existence of these multiple pathways often limits the advantages of available therapies. The nutraceutical-based approach has opened the doors to target these common multifaceted pathways in a slow and more physiological manner to starve the NDs. Peer-reviewed articles were searched via MEDLINE and PubMed published to date for in-depth research and database collection. Considered to be complementary therapy with current clinical management and common drug therapy, the intake of nutraceuticals is considered safe to target multiple mechanisms of action in NDs. The current review summarizes the popular nutraceuticals showing different effects (anti-inflammatory, antioxidant, neuro-protectant, mitochondrial homeostasis, neurogenesis promotion, and autophagy regulation) on vital molecular mechanisms involved in NDs, which can be considered as complementary therapy to first-line treatment. Moreover, owing to its natural source, lower toxicity, therapeutic interventions, biocompatibility, potential nutritional effects, and presence of various anti-oxidative and neuroprotective constituents, the nutraceuticals serve as an attractive option to tackle NDs.

Nutraceuticals against Neurodegeneration: A Mechanistic Insight

The mechanisms underlying neurodegenerative disorders are complex and multifactorial; however, accumulating evidences suggest few common shared pathways. These common pathways include mitochondrial dysfunction, intracellular Ca2+ overload, oxidative stress and inflammation. Often multiple pathways co-exist, and therefore limit the benefits of therapeutic interventions. Nutraceuticals have recently gained importance owing to their multifaceted effects. These food-based approaches are believed to target multiple pathways in a slow but more physiological manner without causing severe adverse effects. Available information strongly supports the notion that apart from preventing the onset of neuronal damage, nutraceuticals can potentially attenuate the continued progression of neuronal destruction. In this article, we i) review the common pathways involved in the pathogenesis of the toxicants-induced neurotoxicity and neurodegenerative disorders with special emphasis on Alzheimer`s disease (AD), Parkinson`s disease (PD), Huntington`s disease (HD), Multiple sclerosis (MS) and Amyotrophic lateral sclerosis (ALS), and ii) summarize current research advancements on the effects of nutraceuticals against these detrimental pathways.

A review of specific dietary antioxidants and the effects on biochemical mechanisms related to neurodegenerative processes

Aging is a major risk factor for neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). An unbalanced overproduction of reactive oxygen species (ROS) may give rise to oxidative stress which can induce neuronal damage, ultimately leading to neuronal death by apoptosis or necrosis. A large body of evidence indicates that oxidative stress is involved in the pathogenesis of AD, PD, and ALS. An increasing number of studies show that nutritional antioxidants (especially Vitamin E and polyphenols) can block neuronal death in vitro, and may have therapeutic properties in animal models of neurodegenerative diseases including AD, PD, and ALS. Moreover, clinical data suggest that nutritional antioxidants might exert some protective effect against AD, PD, and ALS. In this paper, the biochemical mechanisms by which nutritional antioxidants can reduce or block neuronal death occurring in neurodegenerative disorders are reviewed. Particular emphasis will be given to the role played by the nuclear transcription factor-kappaB (NF-kappaB) in apoptosis, and in the pathogenesis of neurodegenerative disorders, such as AD, PD, and ALS. The effects of ROS and antioxidants on NF-kappaB function and their relevance in the pathophysiology of neurodegenerative diseases will also be examined.

Natural Antioxidant Anthocyanins-A Hidden Therapeutic Candidate in Metabolic Disorders with Major Focus in Neurodegeneration

All over the world, metabolic syndrome constitutes severe health problems. Multiple factors have been reported in the pathogenesis of metabolic syndrome. Metabolic disorders result in reactive oxygen species (ROS) induced oxidative stress, playing a vital role in the development and pathogenesis of major health issues, including neurological disorders Alzheimer's disease (AD) Parkinson's disease (PD). Considerable increasing evidence indicates the substantial contribution of ROS-induced oxidative stress in neurodegenerative diseases. An imbalanced metabolism results in a defective antioxidant defense system, free radicals causing inflammation, cellular apoptosis, and tissue damage. Due to the annual increase in financial and social burdens, in addition to the adverse effects associated with available synthetic agents, treatment diversion from synthetic to natural approaches has occurred. Antioxidants are now being considered as convincing therapeutic agents against various neurodegenerative disorders. Therefore, medicinal herbs and fruits currently receive substantially more attention as commercial sources of antioxidants. In this review, we argue that ROS-targeted therapeutic interventions with naturally occurring antioxidant flavonoid, anthocyanin, and anthocyanin-loaded nanoparticles might be the ultimate treatment against devastating illnesses. Furthermore, we elucidate the hidden potential of the neuroprotective role of anthocyanins and anthocyanin-loaded nanoparticles in AD and PD neuropathies, which lack sufficient attention compared with other polyphenols, despite their strong antioxidant potential. Moreover, we address the need for future research studies of native anthocyanins and nano-based-anthocyanins, which will be helpful in developing anthocyanin treatments as therapeutic mitochondrial antioxidant drug-like regimens to delay or prevent the progression of neurodegenerative diseases, such as AD and PD.

An Overview and Therapeutic Promise of Nutraceuticals Against Sports-Related Brain Injury

Sports-related traumatic brain injury (TBI) is one of the common neurological maladies experienced by athletes. Earlier, the term 'punch drunk syndrome' was used in the case TBI of boxers and now this term is replaced by chronic traumatic encephalopathy (CTE). Sports-related brain injury can either be short-term or long-term. A common instance of brain injury encompasses subdural hematoma, concussion, cognitive dysfunction, amnesia, headache, vision issue, axonopathy, or even death, if it remains undiagnosed or untreated. Further, chronic TBI may lead to pathogenesis of neuroinflammation and neurodegeneration via tauopathy, the formation of neurofibrillary tangles, and damage to the blood-brain barrier, microglial, and astrocyte activation. Thus, altered pathological, neurochemical, and neurometabolic attributes lead to the modulation of multiple signaling pathways and cause neurological dysfunction. Available pharmaceutical interventions are based on one drug one target hypothesis and are thereby unable to cover altered multiple signaling pathways. However, in recent times, pharmacological intervention of nutrients and nutraceuticals have been explored as they exert a multifactorial mode of action and maintain over homeostasis of the body. There are various reports available showing the positive therapeutic effect of nutraceuticals in sport-related brain injury. Therefore, in the current article, we have discussed the pathology, neurological consequence, sequelae, and perpetuation of sports-related brain injury. Further, we have discussed various nutraceutical supplements as well as available animal models to explore the neuroprotective effect/ upshots of these nutraceuticals in sports-related brain injury.

Nicotinamide mononucleotide inhibits post-ischemic NAD(+) degradation and dramatically ameliorates brain damage following global cerebral ischemia

Nicotinamide adenine dinucleotide (NAD(+)) is an essential cofactor for multiple cellular metabolic reactions and has a central role in energy production. Brain ischemia depletes NAD(+) pools leading to bioenergetics failure and cell death. Nicotinamide mononucleotide (NMN) is utilized by the NAD(+) salvage pathway enzyme, nicotinamide adenylyltransferase (Nmnat) to generate NAD(+). Therefore, we examined whether NMN could protect against ischemic brain damage. Mice were subjected to transient forebrain ischemia and treated with NMN or vehicle at the start of reperfusion or 30min after the ischemic insult. At 2, 4, and 24h of recovery, the proteins poly-ADP-ribosylation (PAR), hippocampal NAD(+) levels, and expression levels of NAD(+) salvage pathway enzymes were determined. Furthermore, animal's neurologic outcome and hippocampal CA1 neuronal death was assessed after six days of reperfusion. NMN (62.5mg/kg) dramatically ameliorated the hippocampal CA1 injury and significantly improved the neurological outcome. Additionally, the post-ischemic NMN treatment prevented the increase in PAR formation and NAD(+) catabolism. Since the NMN administration did not affect animal's temperature, blood gases or regional cerebral blood flow during recovery, the protective effect was not a result of altered reperfusion conditions. These data suggest that administration of NMN at a proper dosage has a strong protective effect against ischemic brain injury.

Nicotinamide mononucleotide inhibits post-ischemic NAD(+) degradation and dramatically ameliorates brain damage following global cerebral ischemia

Nicotinamide adenine dinucleotide (NAD(+)) is an essential cofactor for multiple cellular metabolic reactions and has a central role in energy production. Brain ischemia depletes NAD(+) pools leading to bioenergetics failure and cell death. Nicotinamide mononucleotide (NMN) is utilized by the NAD(+) salvage pathway enzyme, nicotinamide adenylyltransferase (Nmnat) to generate NAD(+). Therefore, we examined whether NMN could protect against ischemic brain damage. Mice were subjected to transient forebrain ischemia and treated with NMN or vehicle at the start of reperfusion or 30min after the ischemic insult. At 2, 4, and 24h of recovery, the proteins poly-ADP-ribosylation (PAR), hippocampal NAD(+) levels, and expression levels of NAD(+) salvage pathway enzymes were determined. Furthermore, animal's neurologic outcome and hippocampal CA1 neuronal death was assessed after six days of reperfusion. NMN (62.5mg/kg) dramatically ameliorated the hippocampal CA1 injury and significantly improved the neurological outcome. Additionally, the post-ischemic NMN treatment prevented the increase in PAR formation and NAD(+) catabolism. Since the NMN administration did not affect animal's temperature, blood gases or regional cerebral blood flow during recovery, the protective effect was not a result of altered reperfusion conditions. These data suggest that administration of NMN at a proper dosage has a strong protective effect against ischemic brain injury.

Nicotinamide mononucleotide attenuates brain injury after intracerebral hemorrhage by activating Nrf2/HO-1 signaling pathway

Replenishment of NAD+ has been shown to protect against brain disorders such as amyotrophic lateral sclerosis and ischemic stroke. However, whether this intervention has therapeutic effects in intracerebral hemorrhage (ICH) is unknown. In this study, we sought to determine the potential therapeutic value of replenishment of NAD+ in ICH. In a collagenase-induced ICH (cICH) mouse model, nicotinamide mononucleotide (NMN), a key intermediate of nicotinamide adenine dinucleotide (NAD+) biosynthesis, was administrated at 30 minutes post cICH from tail vein to replenish NAD+. NMN treatment did not decrease hematoma volume and hemoglobin content. However, NMN treatment significantly reduced brain edema, brain cell death, oxidative stress, neuroinflammation, intercellular adhesion molecule-1 expression, microglia activation and neutrophil infiltration in brain hemorrhagic area. Mechanistically, NMN enhanced the expression of two cytoprotective proteins: heme oxygenase 1 (HO-1) and nuclear factor-like 2 (Nrf2). Moreover, NMN increased the nuclear translocation of Nrf2 for its activation. Finally, a prolonged NMN treatment for 7 days markedly promoted the recovery of body weight and neurological function. These results demonstrate that NMN treats brain injury in ICH by suppressing neuroinflammation/oxidative stress. The activation of Nrf2/HO-1 signaling pathway may contribute to the neuroprotection of NMN in ICH.

Oral Administration of Nicotinamide Mononucleotide Increases Nicotinamide Adenine Dinucleotide Level in an Animal Brain

As a redox-sensitive coenzyme, nicotinamide adenine dinucleotide (NAD+) plays a central role in cellular energy metabolism and homeostasis. Low NAD+ levels are linked to multiple disease states, including age-related diseases, such as metabolic and neurodegenerative diseases. Consequently, restoring/increasing NAD+ levels in vivo has emerged as an important intervention targeting age-related neurodegenerative diseases. One of the widely studied approaches to increase NAD+ levels in vivo is accomplished by using NAD+ precursors, such as nicotinamide mononucleotide (NMN). Oral administration of NMN has been shown to successfully increase NAD+ levels in a variety of tissues; however, it remains unclear whether NMN can cross the blood-brain barrier to increase brain NAD+ levels. This study evaluated the effects of oral NMN administration on NAD+ levels in C57/B6J mice brain tissues. Our results demonstrate that oral gavage of 400 mg/kg NMN successfully increases brain NAD+ levels in mice after 45 min. These findings provide evidence that NMN may be used as an intervention to increase NAD+ levels in the brain.

The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial

In animal studies, β-nicotinamide mononucleotide (NMN) supplementation increases nicotinamide adenine dinucleotide (NAD) concentrations and improves healthspan and lifespan with great safety. However, it is unclear if these effects can be transferred to humans. This randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial included 80 middle-aged healthy adults being randomized for a 60-day clinical trial with once daily oral dosing of placebo, 300 mg, 600 mg, or 900 mg NMN. The primary objective was to evaluate blood NAD concentration with dose-dependent regimens. The secondary objectives were to assess the safety and tolerability of NMN supplementation, next to the evaluation of clinical efficacy by measuring physical performance (six-minute walking test), blood biological age (Aging.Ai 3.0 calculator), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and subjective general health assessment [36-Item Short Form Survey Instrument (SF-36)]. Statistical analysis was performed using the Per Protocol analysis with significant level set at p = 0.05. All 80 participants completed the trial without trial protocol violation. Blood NAD concentrations were statistically significantly increased among all NMN-treated groups at day 30 and day 60 when compared to both placebo and baseline (all p ≤ 0.001). Blood NAD concentrations were highest in the groups taking 600 mg and 900 mg NMN. No safety issues, based on monitoring adverse events (AEs), laboratory and clinical measures, were found, and NMN supplementation was well tolerated. Walking distance increase during the six-minute walking test was statistically significantly higher in the 300 mg, 600 mg, and 900 mg groups compared to placebo at both days 30 and 60 (all p < 0.01), with longest walking distances measured in the 600 mg and 900 mg groups. The blood biological age increased significantly in the placebo group and stayed unchanged in all NMN-treated groups at day 60, which resulted in a significant difference between the treated groups and placebo (all p < 0.05). The HOMA-IR showed no statistically significant differences for all NMN-treated groups as compared to placebo at day 60. The change of SF-36 scores at day 30 and day 60 indicated statistically significantly better health of all three treated groups when compared to the placebo group (p < 0.05), except for the SF-36 score change in the 300 mg group at day 30. NMN supplementation increases blood NAD concentrations and is safe and well tolerated with oral dosing up to 900 mg NMN daily. Clinical efficacy expressed by blood NAD concentration and physical performance reaches highest at a dose of 600 mg daily oral intake. This trial was registered with ClinicalTrials.gov, NCT04823260, and Clinical Trial Registry - India, CTRI/2021/03/032421.

Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence

Nicotinamide adenine dinucleotide (NAD), the cell's hydrogen carrier for redox enzymes, is well known for its role in redox reactions. More recently, it has emerged as a signaling molecule. By modulating NAD+-sensing enzymes, NAD+ controls hundreds of key processes from energy metabolism to cell survival, rising and falling depending on food intake, exercise, and the time of day. NAD+ levels steadily decline with age, resulting in altered metabolism and increased disease susceptibility. Restoration of NAD+ levels in old or diseased animals can promote health and extend lifespan, prompting a search for safe and efficacious NAD-boosting molecules that hold the promise of increasing the body's resilience, not just to one disease, but to many, thereby extending healthy human lifespan.

NAD+ and sirtuins in aging and disease

Nicotinamide adenine dinucleotide (NAD(+)) is a classical coenzyme mediating many redox reactions. NAD(+) also plays an important role in the regulation of NAD(+)-consuming enzymes, including sirtuins, poly-ADP-ribose polymerases (PARPs), and CD38/157 ectoenzymes. NAD(+) biosynthesis, particularly mediated by nicotinamide phosphoribosyltransferase (NAMPT), and SIRT1 function together to regulate metabolism and circadian rhythm. NAD(+) levels decline during the aging process and may be an Achilles' heel, causing defects in nuclear and mitochondrial functions and resulting in many age-associated pathologies. Restoring NAD(+) by supplementing NAD(+) intermediates can dramatically ameliorate these age-associated functional defects, counteracting many diseases of aging, including neurodegenerative diseases. Thus, the combination of sirtuin activation and NAD(+) intermediate supplementation may be an effective antiaging intervention, providing hope to aging societies worldwide.

NAMPT and NAMPT-controlled NAD Metabolism in Vascular Repair

Vascular repair plays important roles in postischemic remodeling and rehabilitation in cardiovascular and cerebrovascular disease, such as stroke and myocardial infarction. Nicotinamide adenine dinucleotide (NAD), a well-known coenzyme involved in electron transport chain for generation of adenosine triphosphate, has emerged as an important controller regulating various biological signaling pathways. Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme for NAD biosynthesis in mammals. NAMPT may also act in a nonenzymatic manner, presumably mediated by unknown receptor(s). Rapidly accumulating data in the past decade show that NAMPT and NAMPT-controlled NAD metabolism regulate fundamental biological functions in endothelial cells, vascular smooth muscle cells, and endothelial progenitor cells. The NAD-consuming proteins, including sirtuins, poly-ADP-ribose polymerases (PARPs), and CD38, may contribute to the regulatory effects of NAMPT-NAD axis in these cells and vascular repair. This review discusses the current data regarding NAMPT and NAMPT-controlled NAD metabolism in vascular repair and the clinical potential translational application of NAMPT-related products in treatment of cardiovascular and cerebrovascular disease.

Intracellular NAMPT-NAD+-SIRT1 cascade improves post-ischaemic vascular repair by modulating Notch signalling in endothelial progenitors

Aims: Intracellular nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme for nicotinamide adenine dinucleotide (NAD(+)) biosynthesis. This study investigated the role of NAMPT-mediated NAD(+) signalling in post-ischaemic vascular repair. Methods and results: Mouse hind-limb ischaemia up-regulated NAMPT expression and NAD(+) level in bone marrow (BM). Pharmacological inhibition of NAMPT by a chemical inhibitor FK866 impaired the mobilization of endothelial progenitor cells (EPCs) from BM upon ischaemic stress. Transgenic mice overexpressing NAMPT (Tg mice), but not H247A-mutant dominant-negative NAMPT (DN-Tg mice), exhibited enhanced capillary density, increased number of proliferating endothelial cells, improved blood flow recovery, and augmented collateral arterioles in the ischaemic limb. In cultured BM-derived EPCs, inhibition of NAMPT suppressed proliferation, migration, and tube formation, whereas overexpression of NAMPT induced opposite effects. The promoting effects of NAMPT on EPCs were abolished by silencing of sirtuin 1 (SIRT1), rather than silencing of SIRT2-7. Overexpression of NAMPT led to a SIRT1-depedent enhancement of Notch-1 intracellular domain deacetylation, which inhibited Delta-like ligand-4 (DLL4)-Notch signalling and thereby up-regulated of VEGFR-2 and VEGFR-3. Injection of recombinant VEGF induced a more pronounced EPC mobilization in Tg, but not in DN-Tg, mice. Furthermore, overexpression of NAMPT down-regulated Fringe family glycosyltransferases in a SIRT1-dependent manner, which rendered Notch more sensitive to the pro-angiogenic ligand Jagged1 rather than the anti-angiogenic ligand DLL4. Conclusions: These results demonstrate that intracellular NAMPT-NAD(+)-SIRT1 cascade improves post-ischaemic neovascularization. The modulation of Notch signalling may contribute to the enhanced post-ischaemic neovascularization.

Nicotinamide Riboside Enhances Endothelial Precursor Cell Function to Promote Refractory Wound Healing Through Mediating the Sirt1/AMPK Pathway

Lack of vascularization is directly associated with refractory wound healing in diabetes mellitus (DM). Enrichment of endothelial precursor cells (EPCs) is a promising but challenging approach for the treatment of diabetic wounds. Herein, we investigate the action of nicotinamide riboside (NR) on EPC function for improved healing of diabetic wounds. Db/db mice that were treated with NR-supplemented food (400 mg/kg/d) for 12 weeks exhibited higher wound healing rates and angiogenesis than untreated db/db mice. In agreement with this phenotype, NR supplementation significantly increased the number of blood EPCs and bone marrow (BM)-derived EPCs of db/db mice, as well as the tube formation and adhesion functions of BM-EPCs. Furthermore, NR-supplemented BM-EPCs showed higher expression of sirtuin 1 (Sirt1), phosphorylated adenosine monophosphate-activated protein kinase (p-AMPK), and lower expression of acetylated peroxisome proliferator-activated receptor γ coactivator (PGC-1α) than BM-EPCs isolated from untreated db/db mice. Knockdown of Sirt1 in BM-EPCs significantly abolished the tube formation and adhesion function of NR as well as the expression of p-AMPK and deacetylated PGC-1a. Inhibition of AMPK abolished the NR-regulated EPC function but had no effect on Sirt1 expression, demonstrating that NR enhances EPC function through the Sirt1-AMPK pathway. Overall, this study demonstrates that the oral uptake of NR enhances the EPC function to promote diabetic wound healing, indicating that NR supplementation might be a promising strategy to prevent the progression of diabetic complications.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

NAD(+) metabolism: Bioenergetics, signaling and manipulation for therapy

We survey the historical development of scientific knowledge surrounding Vitamin B3, and describe the active metabolite forms of Vitamin B3, the pyridine dinucleotides NAD+ and NADP+ which are essential to cellular processes of energy metabolism, cell protection and biosynthesis. The study of NAD+ has become reinvigorated by new understandings that dynamics within NAD+ metabolism trigger major signaling processes coupled to effectors (sirtuins, PARPs, and CD38) that reprogram cellular metabolism using NAD+ as an effector substrate. Cellular adaptations include stimulation of mitochondrial biogenesis, a process fundamental to adjusting cellular and tissue physiology to reduced nutrient availability and/or increased energy demand. Several mammalian metabolic pathways converge to NAD+, including tryptophan-derived de novo pathways, nicotinamide salvage pathways, nicotinic acid salvage and nucleoside salvage pathways incorporating nicotinamide riboside and nicotinic acid riboside. Key discoveries highlight a therapeutic potential for targeting NAD+ biosynthetic pathways for treatment of human diseases. A recent emergence of understanding that NAD+ homeostasis is vulnerable to aging and disease processes has stimulated testing to determine if replenishment or augmentation of cellular or tissue NAD+ can have ameliorative effects on aging or disease phenotypes. This experimental approach has provided several proofs of concept successes demonstrating that replenishment or augmentation of NAD+ concentrations can provide ameliorative or curative benefits. Thus NAD+ metabolic pathways can provide key biomarkers and parameters for assessing and modulating organism health.

Nicotinamide Adenine Dinucleotide in the Development and Treatment of Cardiac Remodeling and Aging

Background: Recently, the beneficial effects of nicotinamide adenine dinucleotide (NAD+) as an antiaging and antioxidant molecule have become a focus of research. However, the mechanisms by which NAD+ supplementation affects the associated metabolites under physiological conditions remain unclear. Specifically, although NAD+ is involved in several processes that are dysregulated in cardiovascular diseases, some effects of NAD+ precursors and NAD+ on cardiac diseases have started to gain recognition only recently. Objective: To discuss the influence of NAD+ supplementation on adverse cardiac remodeling and aging. Results: Supplementation with NAD+ precursors or nicotinamide riboside, which enhances or supplements the NAD+metabolome, might have a protective effect on the heart. NAD+ can alleviate chronic heart failure via mitochondrial oxidation-reduction (redox) state mechanism. Furthermore, NAD+ replenishment can improve the life span of mice. Conclusion: NAD+ exerts considerable antiaging and antioxidant effects with promising therapeutic effects. However, its effect on humans and its use as a dietary supplement need to be studied further.

Nicotinamide adenine dinucleotide emerges as a therapeutic target in aging and ischemic conditions

Nicotinamide adenine dinucleotide (NAD+) has been described as central coenzyme of redox reactions and is a key regulator of stress resistance and longevity. Aging is a multifactorial and irreversible process that is characterized by a gradual diminution in physiological functions in an organism over time, leading to development of age-associated pathologies and eventually increasing the probability of death. Ischemia is the lack of nutritive blood flow that causes damage and mortality that mostly occurs in various organs during aging. During the process of aging and related ischemic conditions, NAD+ levels decline and lead to nuclear and mitochondrial dysfunctions, resulting in age-related pathologies. The majority of studies have shown that restoring of NAD+ using supplementation with intermediates such as nicotinamide mononucleotide and nicotinamide riboside can be a valuable strategy for recovery of ischemic injury and age-associated defects. This review summarizes the molecular mechanisms responsible for the reduction in NAD+ levels during ischemic disorders and aging, as well as a particular focus is given to the recent progress in the understanding of NAD+ precursor's effects on aging and ischemia.

Nicotinamide riboside, a trace nutrient in foods, is a vitamin B3 with effects on energy metabolism and neuroprotection

Purpose of review: This review focuses upon the biology and metabolism of a trace component in foods called nicotinamide riboside. Nicotinamide riboside is a precursor of nicotinamide adenine dinucleotide (NAD), and is a source of Vitamin B3. Evidence indicates that nicotinamide riboside has unique properties as a Vitamin B3. We review knowledge of the metabolism of this substance, as well as recent work suggesting novel health benefits that might be associated with nicotinamide riboside taken in larger quantities than is found naturally in foods. Recent findings: Recent work investigating the effects of nicotinamide riboside in yeast and mammals established that it is metabolized by at least two types of metabolic pathways. The first of these is degradative and produces nicotinamide. The second pathway involves kinases called nicotinamide riboside kinases (Nrk1 and Nrk2, in humans). The likely involvement of the kinase pathway is implicated in the unique effects of nicotinamide riboside in raising tissue NAD concentrations in rodents and for potent effects in eliciting insulin sensitivity, mitochondrial biogenesis, and enhancement of sirtuin functions. Additional studies with nicotinamide riboside in models of Alzheimer's disease indicate bioavailability to brain and protective effects, likely by stimulation of brain NAD synthesis. Summary: Initial studies have clarified the potential for a lesser-known Vitamin B3 called nicotinamide riboside that is available in selected foods, and possibly available to humans by supplements. It has properties that are insulin sensitizing, enhancing to exercise, resisting to negative effects of high-fat diet, and neuroprotecting.

Nicotinamide riboside promotes Sir2 silencing and extends lifespan via Nrk and Urh1/Pnp1/Meu1 pathways to NAD+

Although NAD(+) biosynthesis is required for Sir2 functions and replicative lifespan in yeast, alterations in NAD(+) precursors have been reported to accelerate aging but not to extend lifespan. In eukaryotes, nicotinamide riboside is a newly discovered NAD(+) precursor that is converted to nicotinamide mononucleotide by specific nicotinamide riboside kinases, Nrk1 and Nrk2. In this study, we discovered that exogenous nicotinamide riboside promotes Sir2-dependent repression of recombination, improves gene silencing, and extends lifespan without calorie restriction. The mechanism of action of nicotinamide riboside is totally dependent on increased net NAD(+) synthesis through two pathways, the Nrk1 pathway and the Urh1/Pnp1/Meu1 pathway, which is Nrk1 independent. Additionally, the two nicotinamide riboside salvage pathways contribute to NAD(+) metabolism in the absence of nicotinamide-riboside supplementation. Thus, like calorie restriction in the mouse, nicotinamide riboside elevates NAD(+) and increases Sir2 function.

Vitamins and aging: pathways to NAD+ synthesis

Recent genetic evidence reveals additional salvage pathways for NAD(+) synthesis. In this issue, Belenky et al. (2007) report that nicotinamide riboside, a new NAD(+) precursor, regulates Sir2 deacetylase activity and life span in yeast. The ability of nicotinamide riboside to enhance life span does not depend on calorie restriction.

Nicotinamide Mononucleotide Supplementation Improves Mitochondrial Dysfunction and Rescues Cellular Senescence by NAD+/Sirt3 Pathway in Mesenchymal Stem Cells

In vitro expansion-mediated replicative senescence has severely limited the clinical applications of mesenchymal stem cells (MSCs). Accumulating studies manifested that nicotinamide adenine dinucleotide (NAD+) depletion is closely related to stem cell senescence and mitochondrial metabolism disorder. Promoting NAD+ level is considered as an effective way to delay aging. Previously, we have confirmed that nicotinamide mononucleotide (NMN), a precursor of NAD+, can alleviate NAD+ deficiency-induced MSC senescence. However, whether NMN can attenuate MSC senescence and its underlying mechanisms are still incompletely clear. The present study herein showed that late passage (LP) MSCs displayed lower NAD+ content, reduced Sirt3 expression and mitochondrial dysfunction. NMN supplementation leads to significant increase in intracellular NAD+ level, NAD+/ NADH ratio, Sirt3 expression, as well as ameliorated mitochondrial function and rescued senescent MSCs. Additionally, Sirt3 over-expression relieved mitochondrial dysfunction, and retrieved senescence-associated phenotypic features in LP MSCs. Conversely, inhibition of Sirt3 activity via a selective Sirt3 inhibitor 3-TYP in early passage (EP) MSCs resulted in aggravated cellular senescence and abnormal mitochondrial function. Furthermore, NMN administration also improves 3-TYP-induced disordered mitochondrial function and cellular senescence in EP MSCs. Collectively, NMN replenishment alleviates mitochondrial dysfunction and rescues MSC senescence through mediating NAD+/Sirt3 pathway, possibly providing a novel mechanism for MSC senescence and a promising strategy for anti-aging pharmaceuticals.

Nicotinamide riboside restores cognition through an upregulation of proliferator-activated receptor-γ coactivator 1α regulated β-secretase 1 degradation and mitochondrial gene expression in Alzheimer's mouse models

Nicotinamide adenine dinucleotide (NAD)(+), a coenzyme involved in redox activities in the mitochondrial electron transport chain, has been identified as a key regulator of the lifespan-extending effects, and the activation of NAD(+) expression has been linked with a decrease in beta-amyloid (Aβ) toxicity in Alzheimer's disease (AD). Nicotinamide riboside (NR) is a NAD(+) precursor, it promotes peroxisome proliferator-activated receptor-γ coactivator 1 (PGC)-1α expression in the brain. Evidence has shown that PGC-1α is a crucial regulator of Aβ generation because it affects β-secretase (BACE1) degradation. In this study we tested the hypothesis that NR treatment in an AD mouse model could attenuate Aβ toxicity through the activation of PGC-1α-mediated BACE1 degradation. Using the Tg2576 AD mouse model, using in vivo behavioral analyses, biochemistry assays, small hairpin RNA (shRNA) gene silencing and electrophysiological recording, we found (1) dietary treatment of Tg2576 mice with 250 mg/kg/day of NR for 3 months significantly attenuates cognitive deterioration in Tg2576 mice and coincides with an increase in the steady-state levels of NAD(+) in the cerebral cortex; (2) application of NR to hippocampal slices (10 μM) for 4 hours abolishes the deficits in long-term potentiation recorded in the CA1 region of Tg2576 mice; (3) NR treatment promotes PGC-1α expression in the brain coinciding with enhanced degradation of BACE1 and the reduction of Aβ production in Tg2576 mice. Further in vitro studies confirmed that BACE1 protein content is decreased by NR treatment in primary neuronal cultures derived from Tg2576 embryos, in which BACE1 degradation was prevented by PGC-1α-shRNA gene silencing; and (4) NR treatment and PGC-1α overexpression enhance BACE1 ubiquitination and proteasomal degradation. Our studies suggest that dietary treatment with NR might benefit AD cognitive function and synaptic plasticity, in part by promoting PGC-1α-mediated BACE1 ubiquitination and degradation, thus preventing Aβ production in the brain.

Nicotinamide Riboside Preserves Cardiac Function in a Mouse Model of Dilated Cardiomyopathy

Background: Myocardial metabolic impairment is a major feature in chronic heart failure. As the major coenzyme in fuel oxidation and oxidative phosphorylation and a substrate for enzymes signaling energy stress and oxidative stress response, nicotinamide adenine dinucleotide (NAD+) is emerging as a metabolic target in a number of diseases including heart failure. Little is known on the mechanisms regulating homeostasis of NAD+ in the failing heart. Methods: To explore possible alterations of NAD+ homeostasis in the failing heart, we quantified the expression of NAD+ biosynthetic enzymes in the human failing heart and in the heart of a mouse model of dilated cardiomyopathy (DCM) triggered by Serum Response Factor transcription factor depletion in the heart (SRFHKO) or of cardiac hypertrophy triggered by transverse aorta constriction. We studied the impact of NAD+ precursor supplementation on cardiac function in both mouse models. Results: We observed a 30% loss in levels of NAD+ in the murine failing heart of both DCM and transverse aorta constriction mice that was accompanied by a decrease in expression of the nicotinamide phosphoribosyltransferase enzyme that recycles the nicotinamide precursor, whereas the nicotinamide riboside kinase 2 (NMRK2) that phosphorylates the nicotinamide riboside precursor is increased, to a higher level in the DCM (40-fold) than in transverse aorta constriction (4-fold). This shift was also observed in human failing heart biopsies in comparison with nonfailing controls. We show that the Nmrk2 gene is an AMP-activated protein kinase and peroxisome proliferator-activated receptor α responsive gene that is activated by energy stress and NAD+ depletion in isolated rat cardiomyocytes. Nicotinamide riboside efficiently rescues NAD+ synthesis in response to FK866-mediated inhibition of nicotinamide phosphoribosyltransferase and stimulates glycolysis in cardiomyocytes. Accordingly, we show that nicotinamide riboside supplementation in food attenuates the development of heart failure in mice, more robustly in DCM, and partially after transverse aorta constriction, by stabilizing myocardial NAD+ levels in the failing heart. Nicotinamide riboside treatment also robustly increases the myocardial levels of 3 metabolites, nicotinic acid adenine dinucleotide, methylnicotinamide, and N1-methyl-4-pyridone-5-carboxamide, that can be used as validation biomarkers for the treatment. Conclusions: The data show that nicotinamide riboside, the most energy-efficient among NAD precursors, could be useful for treatment of heart failure, notably in the context of DCM, a disease with few therapeutic options.

Can nicotinamide riboside protect against cognitive impairment?

Purpose of review: The present review aims to address the clinical benefits of using nicotinamide riboside, a precursor to the essential pyridine nucleotide, nicotinamide adenine dinucleotide (NAD+) as a therapeutic agent to attenuate age-related cognitive decline. Recent findings: Oral supplementation with nicotinamide riboside can inhibit the accumulation of pathological hallmarks of Alzheimer's disease and improve learning and memory in various murine models for dementia. Nicotinamide riboside can also reduce DNA damage, neuroinflammation, apoptosis, and improved hippocampal synaptic plasticity in diabetic mice, and another Alzheimer's disease mouse model. The cognitive benefits of nicotinamide riboside in Alzheimer's disease models may be modulated in part by upregulation of proliferator-activated-γ coactivator 1α-mediated β-secretase 1(BACE-1) ubiquitination and degradation, preventing Aβ production in the brain. Nicotinamide riboside also maintained blood-brain barrier integrity and maintained the gut microbiota in a mouse model for cerebral small vessel disease and alcohol-induced depression, respectively. Oral nicotinamide riboside has been shown to be bioavailable and well tolerated in humans with limited adverse effects compared to other NAD+ precursors. Summary: Oral nicotinamide riboside may represent a promising stratagem to improve cognitive decline during 'normal' ageing, Alzheimer's disease and other diseases. Results from recent clinical trials are needed to enumerate the preclinical benefits in humans.

Acute Treatment with Nicotinamide Riboside Chloride Reduces Hippocampal Damage and Preserves the Cognitive Function of Mice with Ischemic Injury

Nicotinamide adenine dinucleotide (NAD) is a critical cosubstrate for enzymes involved in supplying energy to the brain. Nicotinamide riboside (NR), an NAD+ precursor, emerges as a neuroprotective factor after chronic brain insults. However, researchers have not determined whether it improves cognition after acute ischemia. In the present study, mice with middle cerebral artery occlusion were treated with NR chloride (NRC, 300 mg/kg, IP., 20 min after reperfusion). The results of the Morris water maze test revealed better recovery of learning and memory function in the NRC-treated group. Acute NRC treatment decreased hippocampal infarct volume, reduced neuronal loss and apoptosis in the hippocampus. Western blot and high-performance liquid chromatography assays of hippocampal tissues revealed that the activation of Sirtin-1 and adenosine 5' monophosphate-activated protein kinase was increased, the NAD content was elevated, and the production of adenosine triphosphate was strengthened by NRC. Collectively, acute NRC treatment increased the energy supply, reduced the neuronal loss and apoptosis, protected the hippocampus and ultimately promoted the recovery of cognitive function after brain ischemia.

Balancing NAD+ deficits with nicotinamide riboside: therapeutic possibilities and limitations

Alterations in cellular nicotinamide adenine dinucleotide (NAD+) levels have been observed in multiple lifestyle and age-related medical conditions. This has led to the hypothesis that dietary supplementation with NAD+ precursors, or vitamin B3s, could exert health benefits. Among the different molecules that can act as NAD+ precursors, Nicotinamide Riboside (NR) has gained most attention due to its success in alleviating and treating disease conditions at the pre-clinical level. However, the clinical outcomes for NR supplementation strategies have not yet met the expectations generated in mouse models. In this review we aim to provide a comprehensive view on NAD+ biology, what causes NAD+ deficits and the journey of NR from its discovery to its clinical development. We also discuss what are the current limitations in NR-based therapies and potential ways to overcome them. Overall, this review will not only provide tools to understand NAD+ biology and assess its changes in disease situations, but also to decide which NAD+ precursor could have the best therapeutic potential.

Circadian cardiac NAD+ metabolism, from transcriptional regulation to healthy aging

Nicotinamide adenine dinucleotide (NAD+) is a critical redox factor and coenzyme with rhythmic availability, and reduced NAD+ levels are a common factor in many disease states, including risk factors associated with aging. Recent studies have expanded on the role of circadian rhythms and the core clock factors that maintain them in the regulation of NAD+ levels in the heart. This has revealed that NAD+ pools and their use are tightly linked to cardiac function, but also heart failure. The convergence of these fields, namely, clock regulation, heart disease, and NAD+ metabolism present a complex network ripe with potential scientific and clinical discoveries, given the growing number of animal models, recently developed technology, and opportunity for safe and accessible precursor supplementation. This review seeks to briefly present known information on circadian rhythms in the heart, connect that research to our understanding of cardiac NAD+ metabolism, and finally discuss potential future experiments to better understand interventional opportunities in cardiovascular health regarding these subjects.

A reduced form of nicotinamide riboside defines a new path for NAD+ biosynthesis and acts as an orally bioavailable NAD+ precursor

Objective: A decay in intracellular NAD+ levels is one of the hallmarks of physiological decline in normal tissue functions. Accordingly, dietary supplementation with NAD+ precursors can prevent, alleviate, or even reverse multiple metabolic complications and age-related disorders in diverse model organisms. Within the constellation of NAD+ precursors, nicotinamide riboside (NR) has gained attention due to its potent NAD+ biosynthetic effects in vivo while lacking adverse clinical effects. Nevertheless, NR is not stable in circulation, and its utilization is rate-limited by the expression of nicotinamide riboside kinases (NRKs). Therefore, there is a strong interest in identifying new effective NAD+ precursors that can overcome these limitations. Methods: Through a combination of metabolomics and pharmacological approaches, we describe how NRH, a reduced form of NR, serves as a potent NAD+ precursor in mammalian cells and mice. Results: NRH acts as a more potent and faster NAD+ precursor than NR in mammalian cells and tissues. Despite the minor structural difference, we found that NRH uses different steps and enzymes to synthesize NAD+, thus revealing a new NRK1-independent pathway for NAD+ synthesis. Finally, we provide evidence that NRH is orally bioavailable in mice and prevents cisplatin-induced acute kidney injury. Conclusions: Our data identify a new pathway for NAD+ synthesis and classify NRH as a promising new therapeutic strategy to enhance NAD+ levels.

NAD+ Metabolism in Cardiac Health, Aging, and Disease

Nicotinamide adenine dinucleotide (NAD+) is a central metabolite involved in energy and redox homeostasis as well as in DNA repair and protein deacetylation reactions. Pharmacological or genetic inhibition of NAD+-degrading enzymes, external supplementation of NAD+ precursors, and transgenic overexpression of NAD+-generating enzymes have wide positive effects on metabolic health and age-associated diseases. NAD+ pools tend to decline with normal aging, obesity, and hypertension, which are all major risk factors for cardiovascular disease, and NAD+ replenishment extends healthspan, avoids metabolic syndrome, and reduces blood pressure in preclinical models. In addition, experimental elevation of NAD+ improves atherosclerosis, ischemic, diabetic, arrhythmogenic, hypertrophic, or dilated cardiomyopathies, as well as different modalities of heart failure. Here, we critically discuss cardiomyocyte-specific circuitries of NAD+ metabolism, comparatively evaluate distinct NAD+ precursors for their preclinical efficacy, and raise outstanding questions on the optimal design of clinical trials in which NAD+ replenishment or supraphysiological NAD+ elevations are assessed for the prevention or treatment of major cardiac diseases. We surmise that patients with hitherto intractable cardiac diseases such as heart failure with preserved ejection fraction may profit from the administration of NAD+ precursors. The development of such NAD+-centered treatments will rely on technological and conceptual progress on the fine regulation of NAD+ metabolism.

Potential Therapeutic Effects of NAMPT-Mediated NAD Biosynthesis in Depression In Vivo

This study aimed to investigate the potential therapeutic effects of nicotinamide phosphoribosyltransferase (NAMPT)-mediated adenine dinucleotide (NAD) biosynthesis in depression models in vivo. Namptflox/flox mice were used to evaluate the role of NAMPT in depression. NAMPT and NAD levels in the prefrontal cortex (PFC) were measured, and depression-associated behavior, cognitive function, and social interaction were evaluated. The expression levels of BDNF, pCREB, CREB, monoamine neurotransmitters, and corticosterone (CORT) were also detected in the PFC. The contents of NAMPT and NAD decreased in the PFC in Namptflox/flox mice. Namptflox/flox mice showed depression-like behaviors, cognitive function deterioration, decreased social ability, and decreased dominance. Meanwhile, there were decreased expression levels of the pCREB/CREB ratio, but not BDNF, in the PFC. Levels of DA, 5-HT, and NE were decreased, and CORT was activated in the PFC of Namptflox/flox mice. Additionally, the role of NAMPT-NAD was examined in rats treated with nicotinamide riboside (NR) after being exposed to chronic unexpected mild stress (CUMS). NR reversed the decreased NAMPT expression in the PFC and HIP, and the NAD content in the PFC, but not HIP in rats with CUMS-induced depression. NR also improved depressive- and anxiolytic-like behaviors, locomotor activity, and cognitive function. BDNF expression and the pCREB/CREB ratio were significantly increased in both the PFC and HIP after NR treatment. The activation of CORT and decreased content of DA were reversed after NR treatment in the PFC. There was no difference in the 5-HT content among groups in both the PFC and HIP. Taken together, NAD synthesis induced by NAMPT could be associated with depression-like behaviors in mice, and the elevated NAD level by NR improved depression in rats.

The Science Behind NMN-A Stable, Reliable NAD+Activator and Anti-Aging Molecule

Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men

Preclinical studies have revealed that the elevation of nicotinamide adenine dinucleotide (NAD + ) upon the administration of nicotinamide mononucleotide (NMN), an NAD + precursor, can mitigate aging-related disorders; however, human data on this are limited. We investigated whether the chronic oral supplementation of NMN can elevate blood NAD + levels and alter physiological dysfunctions in healthy older participants. We administered 250 mg NMN per day to aged men for 6 or 12 weeks in a placebo-controlled, randomized, double-blind, parallel-group trial. Chronic NMN supplementation was well tolerated and caused no significant deleterious effect. Metabolomic analysis of whole blood samples demonstrated that oral NMN supplementation significantly increased the NAD + and NAD + metabolite concentrations. There were nominally significant improvements in gait speed and performance in the left grip test, which should be validated in larger studies; however, NMN exerted no significant effect on body composition. Therefore, chronic oral NMN supplementation can be an efficient NAD + booster for preventing aging-related muscle dysfunctions in humans.

Improvement of tissue-specific distribution and biotransformation potential of nicotinamide mononucleotide in combination with ginsenosides or resveratrol

Decreased Nicotinamide adenine dinucleotide (NAD+ ) level has received increasing attention in recent years since it plays a critical role in many diseases and aging. Although some research has proved that supplementing nicotinamide mononucleotide (NMN) could improve the level of NAD+ , it is still uncertain whether the NAD+ level in specific tissues could be improved in combination with other nutrients. So far, a variety of nutritional supplements have flooded the market, which contains the compositions of NMN coupled with natural products. However, the synergy and transformation process of NMN has not been fully elucidated. In this study, oral administration of NMN (500 mg/kg) combined with resveratrol (50 mg/kg) or ginsenoside Rh2&Rg3 (50 mg/kg) was used to validate the efficacy of appropriate drug combinations in mice. Compared with NMN alone, NMN combined with resveratrol could increase the levels of NAD+ in the heart and muscle by about 1.6 times and 1.7 times, respectively, whereas NMN coupled with ginsenoside Rh2&Rg3 could effectively improve the level of NAD+ in lung tissue for approximately 2.0 times. Our study may provide new treatment ideas for aging or diseases in cardiopulmonary caused by decreased NAD+ levels.

The role of nicotinamide mononucleotide (NMN) in anti-aging, longevity, and its potential for treating chronic conditions

Biosynthesis and regulation of nicotinamide adenine dinucleotide (NAD+) has recently gained a lot of attention. A systemic decline in NAD+ across many tissues is associated with all the hallmarks of aging. NAD+ can affect a variety of cellular processes, including metabolic pathways, DNA repair, and immune cell activity, both directly and indirectly. These cellular processes play a vital role in maintaining homeostasis, but as people get older, their tissue and cellular NAD+ levels decrease, and this drop in NAD+ levels has been connected to a number of age-related disorders. By restoring NAD+ levels, several of these age-related disorders can be delayed or even reversed. Some of the new studies conducted in mice and humans have targeted the NAD+ metabolism with NAD+ intermediates. Of these, nicotinamide mononucleotide (NMN) has been shown to offer great therapeutic potential with promising results in age-related chronic conditions such as diabetes, cardiovascular issues, cognitive impairment, and many others. Further, human interventions are required to study the long-term effects of supplementing NMN with varying doses. The paper focuses on reviewing the importance of NAD+ on human aging and survival, biosynthesis of NAD+ from its precursors, key clinical trial findings, and the role of NMN on various health conditions.

A Combination of Nicotinamide and D-Ribose (RiaGev) Is Safe and Effective to Increase NAD+ Metabolome in Healthy Middle-Aged Adults: A Randomized, Triple-Blind, Placebo-Controlled, Cross-Over Pilot Clinical Trial

Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor required for proper functioning of all cells and its decline is correlated with advancing age and disease. This randomized, triple-blind, placebo-controlled, crossover pilot study assessed the efficacy and safety of a combination of nicotinamide with D-ribose (RiaGev) for NAD metabolome enhancement and related benefits in healthy middle-aged adults. Supplementing with 1520 mg RiaGev twice daily for 7 days significantly increased the NAD+ metabolome in blood, especially NADP+ by 27% compared to the placebo group (p = 0.033) and over the baseline (p = 0.007). Increases in glutathione and high energy phosphates were also observed in the blood. Seven-day supplementation with RiaGev significantly (p = 0.013) reduced overall blood glucose without significant changes in insulin secretion (p = 0.796), suggesting an improved insulin sensitivity and glucose tolerance. The waking salivary cortisol of the subjects steadily and significantly decreased (p = 0.026) in the RiaGev group in contrast to the placebo. Subjects in the RiaGev group showed less fatigue, improved mental concentration and motivation over the baseline (p = 0.015, 0.018, and 0.012, respectively) as observed through the Checklist Individual Strength (CIS) questionnaire. There were no clinically relevant adverse events, or alterations in hematology, electrolytes, liver, and kidney markers pre- and post-supplementation. RiaGev appears to be safe and efficacious in increasing NAD+ metabolome in healthy middle-aged adults, as shown by this study.

Investigating RNA expression profiles altered by nicotinamide mononucleotide therapy in a chronic model of alcoholic liver disease

Background: Chronic alcohol consumption is a significant cause of liver disease worldwide. Several biochemical mechanisms have been linked to the initiation and progression of alcoholic liver disease (ALD) such as oxidative stress, inflammation, and metabolic dysregulation, including the disruption of NAD+/NADH. Indeed, an ethanol-mediated reduction in hepatic NAD+ levels is thought to be one factor underlying ethanol-induced steatosis, oxidative stress, steatohepatitis, insulin resistance, and inhibition of gluconeogenesis. Therefore, we applied a NAD+ boosting supplement to investigate alterations in the pathogenesis of early-stage ALD. Methods: To examine the impact of NAD+ therapy on the early stages of ALD, we utilized nicotinamide mononucleotide (NMN) at 500 mg/kg intraperitoneal injection every other day, for the duration of a Lieber-DeCarli 6-week chronic ethanol model in mice. Numerous strategies were employed to characterize the effect of NMN therapy, including the integration of RNA-seq, immunoblotting, and metabolomics analysis. Results: Our findings reveal that NMN therapy increased hepatic NAD+ levels, prevented an ethanol-induced increase in plasma ALT and AST, and changed the expression of 25% of the genes that were modulated by ethanol metabolism. These genes were associated with a number of pathways including the MAPK pathway. Interestingly, our analysis revealed that NMN treatment normalized Erk1/2 signaling and prevented an induction of Atf3 overexpression. Conclusions: These findings reveal previously unreported mechanisms by which NMN supplementation alters hepatic gene expression and protein pathways to impact ethanol hepatotoxicity in an early-stage murine model of ALD. Overall, our data suggest further research is needed to fully characterize treatment paradigms and biochemical implications of NAD+-based interventions.

Nicotinamide mononucleotide (NMN) supplementation promotes anti-aging miRNA expression profile in the aorta of aged mice, predicting epigenetic rejuvenation and anti-atherogenic effects

Understanding molecular mechanisms involved in vascular aging is essential to develop novel interventional strategies for treatment and prevention of age-related vascular pathologies. Recent studies provide critical evidence that vascular aging is characterized by NAD+ depletion. Importantly, in aged mice, restoration of cellular NAD+ levels by treatment with the NAD+ booster nicotinamide mononucleotide (NMN) exerts significant vasoprotective effects, improving endothelium-dependent vasodilation, attenuating oxidative stress, and rescuing age-related changes in gene expression. Strong experimental evidence shows that dysregulation of microRNAs (miRNAs) has a role in vascular aging. The present study was designed to test the hypothesis that age-related NAD+ depletion is causally linked to dysregulation of vascular miRNA expression. A corollary hypothesis is that functional vascular rejuvenation in NMN-treated aged mice is also associated with restoration of a youthful vascular miRNA expression profile. To test these hypotheses, aged (24-month-old) mice were treated with NMN for 2 weeks and miRNA signatures in the aortas were compared to those in aortas obtained from untreated young and aged control mice. We found that protective effects of NMN treatment on vascular function are associated with anti-aging changes in the miRNA expression profile in the aged mouse aorta. The predicted regulatory effects of NMN-induced differentially expressed miRNAs in aged vessels include anti-atherogenic effects and epigenetic rejuvenation. Future studies will uncover the mechanistic role of miRNA gene expression regulatory networks in the anti-aging effects of NAD+ booster treatments and determine the links between miRNAs regulated by NMN and sirtuin activators and miRNAs known to act in the conserved pathways of aging and major aging-related vascular diseases.

Modulation of NAD+ biosynthesis activates SIRT1 and resists cisplatin-induced ototoxicity

Cisplatin, the most widely used platinum-based anticancer drug, often causes progressive and irreversible sensorineural hearing loss in cancer patients. However, the precise mechanism underlying cisplatin-associated ototoxicity is still unclear. Nicotinamide adenine dinucleotide (NAD+), a co-substrate for the sirtuin family and PARPs, has emerged as a potent therapeutic molecular target in various diseases. In our investigates, we observed that NAD+ level was changed in the cochlear explants of mice treated with cisplatin. Supplementation of a specific inhibitor (TES-1025) of α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), a rate-limiting enzyme of NAD+de novo synthesis pathway, promoted SIRT1 activity, increased mtDNA contents and enhanced AMPK expression, thus significantly reducing hair cells loss and deformation. The protection was blocked by EX527, a specific SIRT1 inhibitor. Meanwhile, the use of NMN, a precursor of NAD+ salvage synthesis pathway, had shown beneficial effect on hair cell under cisplatin administration, effectively suppressing PARP1. In vivo experiments confirmed the hair cell protection of NAD+ modulators in cisplatin treated mice and zebrafish. In conclusion, we demonstrated that modulation of NAD+ biosynthesis via the de novo synthesis pathway and the salvage synthesis pathway could both prevent ototoxicity of cisplatin. These results suggested that direct modulation of cellular NAD+ levels could be a promising therapeutic approach for protection of hearing from cisplatin-induced ototoxicity.

Fueling genome maintenance: On the versatile roles of NAD+ in preserving DNA integrity

NAD+ is a versatile biomolecule acting as a master regulator and substrate in various cellular processes, including redox regulation, metabolism, and various signaling pathways. In this article, we concisely and critically review the role of NAD+ in mechanisms promoting genome maintenance. Numerous NAD+-dependent reactions are involved in the preservation of genome stability, the cellular DNA damage response, and other pathways regulating nucleic acid metabolism, such as gene expression and cell proliferation pathways. Of note, NAD+ serves as a substrate to ADP-ribosyltransferases, sirtuins, and potentially also eukaryotic DNA ligases, all of which regulate various aspects of DNA integrity, damage repair, and gene expression. Finally, we critically analyze recent developments in the field as well as discuss challenges associated with therapeutic actions intended to raise NAD+ levels.

Nicotinamide mononucleotide (NMN) supplementation promotes anti-aging miRNA expression profile in the aorta of aged mice, predicting epigenetic rejuvenation and anti-atherogenic effects

Understanding molecular mechanisms involved in vascular aging is essential to develop novel interventional strategies for treatment and prevention of age-related vascular pathologies. Recent studies provide critical evidence that vascular aging is characterized by NAD+ depletion. Importantly, in aged mice, restoration of cellular NAD+ levels by treatment with the NAD+ booster nicotinamide mononucleotide (NMN) exerts significant vasoprotective effects, improving endothelium-dependent vasodilation, attenuating oxidative stress, and rescuing age-related changes in gene expression. Strong experimental evidence shows that dysregulation of microRNAs (miRNAs) has a role in vascular aging. The present study was designed to test the hypothesis that age-related NAD+ depletion is causally linked to dysregulation of vascular miRNA expression. A corollary hypothesis is that functional vascular rejuvenation in NMN-treated aged mice is also associated with restoration of a youthful vascular miRNA expression profile. To test these hypotheses, aged (24-month-old) mice were treated with NMN for 2 weeks and miRNA signatures in the aortas were compared to those in aortas obtained from untreated young and aged control mice. We found that protective effects of NMN treatment on vascular function are associated with anti-aging changes in the miRNA expression profile in the aged mouse aorta. The predicted regulatory effects of NMN-induced differentially expressed miRNAs in aged vessels include anti-atherogenic effects and epigenetic rejuvenation. Future studies will uncover the mechanistic role of miRNA gene expression regulatory networks in the anti-aging effects of NAD+ booster treatments and determine the links between miRNAs regulated by NMN and sirtuin activators and miRNAs known to act in the conserved pathways of aging and major aging-related vascular diseases.

Nicotinamide mononucleotide (NMN) supplementation rescues cerebromicrovascular endothelial function and neurovascular coupling responses and improves cognitive function in aged mice

Adjustment of cerebral blood flow (CBF) to neuronal activity via neurovascular coupling (NVC) has an essential role in maintenance of healthy cognitive function. In aging increased oxidative stress and cerebromicrovascular endothelial dysfunction impair NVC, contributing to cognitive decline. There is increasing evidence showing that a decrease in NAD+ availability with age plays a critical role in a range of age-related cellular impairments but its role in impaired NVC responses remains unexplored. The present study was designed to test the hypothesis that restoring NAD+ concentration may exert beneficial effects on NVC responses in aging. To test this hypothesis 24-month-old C57BL/6 mice were treated with nicotinamide mononucleotide (NMN), a key NAD+ intermediate, for 2 weeks. NVC was assessed by measuring CBF responses (laser Doppler flowmetry) evoked by contralateral whisker stimulation. We found that NVC responses were significantly impaired in aged mice. NMN supplementation rescued NVC responses by increasing endothelial NO-mediated vasodilation, which was associated with significantly improved spatial working memory and gait coordination. These findings are paralleled by the sirtuin-dependent protective effects of NMN on mitochondrial production of reactive oxygen species and mitochondrial bioenergetics in cultured cerebromicrovascular endothelial cells derived from aged animals. Thus, a decrease in NAD+ availability contributes to age-related cerebromicrovascular dysfunction, exacerbating cognitive decline. The cerebromicrovascular protective effects of NMN highlight the preventive and therapeutic potential of NAD+ intermediates as effective interventions in patients at risk for vascular cognitive impairment (VCI).

Multi-targeted Effect of Nicotinamide Mononucleotide on Brain Bioenergetic Metabolism

Dysfunctions in NAD+ metabolism are associated with neurodegenerative diseases, acute brain injury, diabetes, and aging. Loss of NAD+ levels results in impairment of mitochondria function, which leads to failure of essential metabolic processes. Strategies to replenish depleted NAD+ pools can offer significant improvements of pathologic states. NAD+ levels are maintained by two opposing enzymatic reactions, one is the consumption of NAD+ while the other is the re-synthesis of NAD+. Inhibition of NAD+ degrading enzymes, poly-ADP-ribose polymerase 1 (PARP1) and ectoenzyme CD38, following brain ischemic insult can provide neuroprotection. Preservation of NAD+ pools by administration of NAD+ precursors, such as nicotinamide (Nam) or nicotinamide mononucleotide (NMN), also offers neuroprotection. However, NMN treatment demonstrates to be a promising candidate as a therapeutic approach due to its multi-targeted effect acting as PARP1 and CD38 inhibitor, sirtuins activator, mitochondrial fission inhibitor, and NAD+ supplement. Many neurodegenerative diseases or acute brain injury activate several cellular death pathways requiring a treatment strategy that will target these mechanisms. Since NMN demonstrated the ability to exert its effect on several cellular metabolic pathways involved in brain pathophysiology it seems to be one of the most promising candidates to be used for successful neuroprotection.

Nicotinamide mononucleotide ameliorates the depression-like behaviors and is associated with attenuating the disruption of mitochondrial bioenergetics in depressed mice

Background: Nicotinamide mononucleotide (NMN) has been shown to stimulate oxidative phosphorylation in mitochondria and to improve various pathologies in patients and mouse disease models. However, whether NMN mediates mitochondrial energy production and its mechanism of action in depressed animals remain unclear. Methods: Mice were subcutaneously injected with corticosterone (CORT; 20 mg/kg) each day for 6 weeks, while another group was given an additional dose of NMN (300 mg/kg) by oral gavage in the last 2 weeks. Then, transcriptome analyses, metabolome analyses and transient gene knockdown in primary mouse cells were performed. Results: NMN administration alleviated depression-like behavior and the liver weight to body weight ratio in a mouse model of CORT-induced depression. Transcriptome and metabolome analyses revealed that in depressed mice, NMN reduced the mRNA expression of genes involved in fatty acid synthesis, stimulation of β-oxidation and glycolysis, and increased production of acetyl-coenzyme A for the tricarboxylic acid cycle. Importantly, NMN supplementation increased NAD+ levels to enhance sirtuin (SIRT)3 activity, thereby improving mitochondrial energy metabolism in the hippocampus and liver of CORT-treated mice. Sirt3knockdown in primary mouse astrocytes reversed the effect of NMN by inhibiting energy production, although it did not affect NAD+ synthesis LIMITATIONS: Group sample sizes were small, and only one type of primary mouse cell was used CONCLUSION: These results provide evidence for the beneficial role of NMN in energy production and suggest that therapeutic strategies that increase the level of NMN can be an effective treatment for depression.

Nicotinamide mononucleotide ameliorates senescence in alveolar epithelial cells

Alveolar epithelial cells (ACEs) gradually senescent as aging, which is one of the main causes of respiratory defense and function decline. Investigating the mechanisms of ACE senescence is important for understanding how the human respiratory system works. NAD+ is reported to reduce during the aging process. Supplementing NAD+ intermediates can activate sirtuin deacylases (SIRT1-SIRT7), which regulates the benefits of exercise and dietary restriction, reduce the level of intracellular oxidative stress, and improve mitochondrial function, thereby reversing cell senescence. We showed that nicotinamide mononucleotide (NMN) could effectively mitigate age-associated physiological decline in the lung of 8-10 months old C57BL/6 mice and bleomycin-induced pulmonary fibrosis in young mice of 6-8 weeks. Besides, the treatment of primary ACEs with NMN can markedly ameliorate cell senescence phenotype in vitro. These findings to improve the respiratory system function and reduce the incidence and mortality from respiratory diseases in the elderly are of great significance.

NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation induced skin injury

Oxidative stress and lipid peroxidation are major causes of skin injury induced by ultraviolet (UV) irradiation. Ferroptosis is a form of regulated necrosis driven by iron-dependent peroxidation of phospholipids and contributes to kinds of tissue injuries. However, it remains unclear whether the accumulation of lipid peroxides in UV irradiation-induced skin injury could lead to ferroptosis. We generated UV irradiation-induced skin injury mice model to examine the accumulation of the lipid peroxides and iron. Lipid peroxides 4-HNE, the oxidative enzyme COX2, the oxidative DNA damage biomarker 8-OHdG, and the iron level were increased in UV irradiation-induced skin. The accumulation of iron and lipid peroxidation was also observed in UVB-irradiated epidermal keratinocytes without actual ongoing ferroptotic cell death. Ferroptosis was triggered in UV-irradiated keratinocytes stimulated with ferric ammonium citrate (FAC) to mimic the iron overload. Although GPX4 protected UVB-injured keratinocytes against ferroptotic cell death resulted from dysregulation of iron metabolism and the subsequent increase of lipid ROS, keratinocytes enduring constant UVB treatment were markedly sensitized to ferroptosis. Nicotinamide mononucleotide (NMN) which is a direct and potent NAD+ precursor supplement, rescued the imbalanced NAD+/NADH ratio, recruited the production of GSH and promoted resistance to lipid peroxidation in a GPX4-dependent manner. Taken together, our data suggest that NMN recruits GSH to enhance GPX4-mediated ferroptosis defense in UV irradiation-induced skin injury and inhibits oxidative skin damage. NMN or ferroptosis inhibitor might become promising therapeutic approaches for treating oxidative stress-induced skin diseases or disorders.

Nicotinamide mononucleotide: An emerging nutraceutical against cardiac aging?

Nicotinamide adenine dinucleotide (NAD) is essential for cellular physiological processes, directly or indirectly affecting metabolism and gene expression. The decline of NAD+ levels in the heart is accompanied by aging, causing cardiac pathological remodeling and dysfunction. Niacinamide mononucleotide (NMN) has emerged as a precursor to alleviate age-related cardiac pathophysiological changes by improving cardiac NAD+ homeostasis. Preclinical trials on the efficacy and safety of intaking NMN have shown encouraging results, revealing a cardioprotective effect without significant side effects. Strategies for improving the effectiveness of NMN are also evolving. The present review aimed to summarize the potentials of NMN as a nutraceutical against cardiac aging and highlight the relationship between NMN supplementation and cardiac protection.

Nicotinamide mononucleotide supplementation enhances aerobic capacity in amateur runners: a randomized, double-blind study

Background: Recent studies in rodents indicate that a combination of exercise training and supplementation with nicotinamide adenine dinucleotide (NAD+) precursors has synergistic effects. However, there are currently no human clinical trials analyzing this. Objective: This study investigates the effects of a combination of exercise training and supplementation with nicotinamide mononucleotide (NMN), the immediate precursor of NAD+, on cardiovascular fitness in healthy amateur runners. Methods: A six-week randomized, double-blind, placebo-controlled, four-arm clinical trial including 48 young and middle-aged recreationally trained runners of the Guangzhou Pearl River running team was conducted. The participants were randomized into four groups: the low dosage group (300 mg/day NMN), the medium dosage group (600 mg/day NMN), the high dosage group (1200 mg/day NMN), and the control group (placebo). Each group consisted of ten male participants and two female participants. Each training session was 40-60 min, and the runners trained 5-6 times each week. Cardiopulmonary exercise testing was performed at baseline and after the intervention, at 6 weeks, to assess the aerobic capacity of the runners. Results: Analysis of covariance of the change from baseline over the 6 week treatment showed that the oxygen uptake (VO2), percentages of maximum oxygen uptake (VO2max), power at first ventilatory threshold, and power at second ventilatory threshold increased to a higher degree in the medium and high dosage groups compared with the control group. However, there was no difference in VO2max, O2-pulse, VO2 related to work rate, and peak power after the 6 week treatment from baseline in any of these groups. Conclusion: NMN increases the aerobic capacity of humans during exercise training, and the improvement is likely the result of enhanced O2 utilization of the skeletal muscle. Trial registration number: ChiCTR2000035138 .

Nicotinamide Phosphoribosyltransferase as a Key Molecule of the Aging/Senescence Process

Aging is a phenomenon underlined by complex molecular and biochemical changes that occur over time. One of the metabolites that is gaining strong research interest is nicotinamide adenine dinucleotide, NAD+, whose cellular level has been shown to decrease with age in various tissues of model animals and humans. Administration of NAD+ precursors, nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), to supplement NAD+ production through the NAD+ salvage pathway has been demonstrated to slow down aging processes in mice. Therefore, NAD+ is a critical metabolite now understood to mitigate age-related tissue function decline and prevent age-related diseases in aging animals. In human clinical trials, administration of NAD+ precursors to the elderly is being used to address systemic age-associated physiological decline. Among NAD+ biosynthesis pathways in mammals, the NAD+ salvage pathway is the dominant pathway in most of tissues, and NAMPT is the rate limiting enzyme of this pathway. However, only a few activators of NAMPT, which are supposed to increase NAD+, have been developed so far. In this review, we will focus on the importance of NAD+ and the possible application of an activator of NAMPT to promote successive aging.

Nicotinamide Mononucleotide Supplementation Reverses the Declining Quality of Maternally Aged Oocytes

Advanced maternal age is highly associated with a decline in oocyte quality, but effective approaches to improve it have still not been fully determined. Here, we report that in vivo supplementation of nicotinamide mononucleotide (NMN) efficaciously improves the quality of oocytes from naturally aged mice by recovering nicotinamide adenine dinucleotide (NAD+) levels. NMN supplementation not only increases ovulation of aged oocytes but also enhances their meiotic competency and fertilization ability by maintaining the normal spindle/chromosome structure and the dynamics of the cortical granule component ovastacin. Moreover, single-cell transcriptome analysis shows that the beneficial effect of NMN on aged oocytes is mediated by restoration of mitochondrial function, eliminating the accumulated ROS to suppress apoptosis. Collectively, our data reveal that NMN supplementation is a feasible approach to protect oocytes from advanced maternal age-related deterioration, contributing to the improvement of reproductive outcome of aged women and assisted reproductive technology.

Nicotinamide mononucleotide (NMN) supplementation promotes neurovascular rejuvenation in aged mice: transcriptional footprint of SIRT1 activation, mitochondrial protection, anti-inflammatory, and anti-apoptotic effects

Aging-induced structural and functional alterations of the neurovascular unit lead to impairment of neurovascular coupling responses, dysregulation of cerebral blood flow, and increased neuroinflammation, all of which contribute importantly to the pathogenesis of age-related vascular cognitive impairment (VCI). There is increasing evidence showing that a decrease in NAD+ availability with age plays a critical role in age-related neurovascular and cerebromicrovascular dysfunction. Our recent studies demonstrate that restoring cellular NAD+ levels in aged mice rescues neurovascular function, increases cerebral blood flow, and improves performance on cognitive tasks. To determine the effects of restoring cellular NAD+ levels on neurovascular gene expression profiles, 24-month-old C57BL/6 mice were treated with nicotinamide mononucleotide (NMN), a key NAD+ intermediate, for 2 weeks. Transcriptome analysis of preparations enriched for cells of the neurovascular unit was performed by RNA-seq. Neurovascular gene expression signatures in NMN-treated aged mice were compared with those in untreated young and aged control mice. We identified 590 genes differentially expressed in the aged neurovascular unit, 204 of which are restored toward youthful expression levels by NMN treatment. The transcriptional footprint of NMN treatment indicates that increased NAD+ levels promote SIRT1 activation in the neurovascular unit, as demonstrated by analysis of upstream regulators of differentially expressed genes as well as analysis of the expression of known SIRT1-dependent genes. Pathway analysis predicts that neurovascular protective effects of NMN are mediated by the induction of genes involved in mitochondrial rejuvenation, anti-inflammatory, and anti-apoptotic pathways. In conclusion, the recently demonstrated protective effects of NMN treatment on neurovascular function can be attributed to multifaceted sirtuin-mediated anti-aging changes in the neurovascular transcriptome. Our present findings taken together with the results of recent studies using mitochondria-targeted interventions suggest that mitochondrial rejuvenation is a critical mechanism to restore neurovascular health and improve cerebral blood flow in aging.

Nicotinamide mononucleotide supplementation reverses vascular dysfunction and oxidative stress with aging in mice

We tested the hypothesis that supplementation of nicotinamide mononucleotide (NMN), a key NAD(+) intermediate, increases arterial SIRT1 activity and reverses age-associated arterial dysfunction and oxidative stress. Old control mice (OC) had impaired carotid artery endothelium-dependent dilation (EDD) (60 ± 5% vs. 84 ± 2%), a measure of endothelial function, and nitric oxide (NO)-mediated EDD (37 ± 4% vs. 66 ± 6%), compared with young mice (YC). This age-associated impairment in EDD was restored in OC by the superoxide (O2-) scavenger TEMPOL (82 ± 7%). OC also had increased aortic pulse wave velocity (aPWV, 464 ± 31 cm s(-1) vs. 337 ± 3 cm s(-1) ) and elastic modulus (EM, 6407 ± 876 kPa vs. 3119 ± 471 kPa), measures of large elastic artery stiffness, compared with YC. OC had greater aortic O2- production (2.0 ± 0.1 vs. 1.0 ± 0.1 AU), nitrotyrosine abundance (a marker of oxidative stress), and collagen-I, and reduced elastin and vascular SIRT1 activity, measured by the acetylation status of the p65 subunit of NFκB, compared with YC. Supplementation with NMN in old mice restored EDD (86 ± 2%) and NO-mediated EDD (61 ± 5%), reduced aPWV (359 ± 14 cm s(-1) ) and EM (3694 ± 315 kPa), normalized O2- production (0.9 ± 0.1 AU), decreased nitrotyrosine, reversed collagen-I, increased elastin, and restored vascular SIRT1 activity. Acute NMN incubation in isolated aortas increased NAD(+) threefold and manganese superoxide dismutase (MnSOD) by 50%. NMN supplementation may represent a novel therapy to restore SIRT1 activity and reverse age-related arterial dysfunction by decreasing oxidative stress.

Restoring nuclear entry of Sirtuin 2 in oligodendrocyte progenitor cells promotes remyelination during ageing

The age-dependent decline in remyelination potential of the central nervous system during ageing is associated with a declined differentiation capacity of oligodendrocyte progenitor cells (OPCs). The molecular players that can enhance OPC differentiation or rejuvenate OPCs are unclear. Here we show that, in mouse OPCs, nuclear entry of SIRT2 is impaired and NAD+ levels are reduced during ageing. When we supplement β-nicotinamide mononucleotide (β-NMN), an NAD+ precursor, nuclear entry of SIRT2 in OPCs, OPC differentiation, and remyelination were rescued in aged animals. We show that the effects on myelination are mediated via the NAD+-SIRT2-H3K18Ac-ID4 axis, and SIRT2 is required for rejuvenating OPCs. Our results show that SIRT2 and NAD+ levels rescue the aged OPC differentiation potential to levels comparable to young age, providing potential targets to enhance remyelination during ageing.

The Plasma NAD+ Metabolome Is Dysregulated in "Normal" Aging

Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide that serves as an electron carrier in cellular metabolism and plays a crucial role in the maintenance of balanced redox homeostasis. Quantification of NAD+:NADH and NADP+:NADPH ratios are pivotal to a wide variety of cellular processes, including intracellular secondary messenger signaling by CD38 glycohydrolases, DNA repair by poly(adenosine diphosphate ribose) polymerase (PARP), epigenetic regulation of gene expression by NAD-dependent histone deacetylase enzymes known as sirtuins, and regulation of the oxidative pentose phosphate pathway. We quantified changes in the NAD+ metabolome in plasma samples collected from consenting healthy human subjects across a wide age range (20-87 years) using liquid chromatography coupled to tandem mass spectrometry. Our data show a significant decline in the plasma levels of NAD+, NADP+, and other important metabolites such as nicotinic acid adenine dinucleotide (NAAD) with age. However, an age-related increase in the reduced form of NAD+ and NADP+-NADH and NADPH-and nicotinamide (NAM), N-methyl-nicotinamide (MeNAM), and the products of adenosine diphosphoribosylation, including adenosine diphosphate ribose (ADPR) was also reported. Whereas, plasma levels of nicotinic acid (NA), nicotinamide mononucleotide (NMN), and nicotinic acid mononucleotide (NAMN) showed no statistically significant changes across age groups. Taken together, our data cumulatively suggest that age-related impairments are associated with corresponding alterations in the extracellular plasma NAD+ metabolome. Our future research will seek to elucidate the role of modulating NAD+ metabolites in the treatment and prevention of age-related diseases.

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