L. rhamnosus

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Research Overview

Across the provided abstracts, Lactobacillus rhamnosus research is most developed in three areas: (1) gut–brain axis and neurobehavioral outcomes (primarily preclinical work, including strain JB-1 effects on central GABA receptor expression and stress-related behaviors via vagal signaling), (2) prevention or mitigation of intestinal inflammation and barrier dysfunction (e.g., ulcerative colitis/IBD-oriented discussions and mechanistic mouse studies under stressors such as hypobaric hypoxia), and (3) clinical outcomes in high-risk hospitalized populations (notably a large multicenter randomized controlled trial of L. rhamnosus GG in mechanically ventilated ICU patients). Additional strain-screening studies emphasize that functional properties (antioxidant, immunomodulatory, metabolic enzyme inhibition) are highly strain-specific, supported by in vitro macrophage assays and genomic characterization of candidate strains.

The strongest evidence in these abstracts comes from the large ICU randomized placebo-controlled trial: enteral L. rhamnosus GG did not reduce ventilator-associated pneumonia or other prespecified clinical outcomes, and it was associated with a higher rate of detection of L. rhamnosus in sterile sites or as a predominant organism—supporting a conclusion of no clinical benefit for VAP prevention in this population and raising safety considerations in critically ill patients. In contrast, preclinical evidence supports biologically plausible mechanisms whereby specific strains can modulate host physiology: JB-1 altered region-specific brain GABA receptor mRNA expression, reduced stress-induced corticosterone, and improved anxiety-/depression-like behaviors in mice in a vagus-dependent manner; and synbiotic administration (stachyose + LGG) improved hypoxia-associated intestinal barrier outcomes in mice, correlating with increased short-chain fatty acids (notably butyrate), reduced inflammatory markers, and microbiome shifts. Rodent work combining L. rhamnosus with sesamol also suggests potential neuroprotective and hepatoprotective effects in an aluminum-toxicity model, but these findings remain preclinical and model-specific.

Key gaps include the need for more well-powered, strain-defined human trials outside the ICU setting to test whether mechanistic benefits observed in animals (stress responsivity, neurochemical signaling, barrier integrity, inflammatory modulation) translate into clinically meaningful outcomes in target populations (e.g., anxiety/depression comorbid with functional bowel disorders, inflammatory bowel disease, or altitude-related gastrointestinal dysfunction). Further research is also needed to clarify dose, duration, host factors (baseline microbiome, immune status), and safety—particularly the risk of probiotic translocation or infection in vulnerable patients. Finally, comparative, strain-resolved studies linking genomic features to specific immunometabolic and neuroactive effects would help explain heterogeneity across L. rhamnosus strains (e.g., JB-1 vs GG vs newly identified isolates) and improve reproducibility and clinical translation.

1. What conditions has L. rhamnosus been studied for?

  • Stress-related and mood-related outcomes (preclinical): Anxiety- and depression-like behavior, stress physiology (corticosterone), and brain GABA receptor expression in healthy mice (strain: L. rhamnosus JB-1).

  • Ventilator-associated pneumonia (VAP) prevention in critical illness (clinical): Mechanically ventilated ICU patients (strain: L. rhamnosus GG; LGG).

  • Acute gastroenteritis in children (clinical): Treatment to reduce diarrhea duration and hospitalization (strain: LGG; evidence summarized in a review of RCTs).

  • Ulcerative colitis / inflammatory bowel disease (IBD) (general clinical context): Abstracts state probiotics have potential benefit for prevention of UC onset/relapse; specific efficacy of L. rhamnosus is not detailed in the provided UC/IBD snippets.

  • High-altitude / hypobaric hypoxia–associated intestinal injury (preclinical): Intestinal barrier dysfunction, inflammation, oxidative stress, microbiota imbalance in mice; tested LGG alone and combined with stachyose (synbiotic).

  • Aluminum-induced neurotoxicity and hepatotoxicity (preclinical): Rat model of AlCl3-induced neurotoxicity; tested L. rhamnosus alone and in combination with sesamol.

  • Metabolic/immune-related in vitro screening (preclinical/in vitro): Antioxidant activity, α-glucosidase inhibition (a diabetes-relevant target), cholesterol-lowering potential, and anti-inflammatory cytokine modulation in macrophages (novel strain: L. rhamnosus 4B15).

  • Cancer-related adjunct concepts (indirect): One abstract discusses “postbiotics derived from probiotic bacteria” for colorectal cancer, but the provided text is incomplete and does not clearly specify L. rhamnosus as the tested organism.

2. Does it work in treating those conditions? Summarize the evidence.

  • Anxiety/depression-like behavior and stress response (mice; JB-1): In healthy mice, chronic JB-1 altered brain GABA receptor subunit mRNA in a region-dependent manner and reduced stress-induced corticosterone and reduced anxiety- and depression-related behavior. Effects were absent in vagotomized mice, implicating the vagus nerve as necessary for the observed effects. This is promising but preclinical and strain-specific.

  • VAP prevention in ICU patients (LGG; large RCT): In a multicenter randomized placebo-controlled trial (n=2653), LGG did not reduce VAP (21.9% vs 21.3%; HR 1.03, 95% CI 0.87–1.22; P=.73) and none of 20 prespecified secondary outcomes (other infections, diarrhea, antimicrobial use, mortality, length of stay) differed significantly. This is strong evidence of no benefit in this setting.

  • Acute gastroenteritis in children (LGG; RCT review): A review of 18 RCTs (n=4208) found LGG had no effect on stool volume but was associated with a shorter duration of diarrhea (15 RCTs, n=3820; mean difference −0.85 day, 95% CI −1.15 to −0.56). The review notes a recent large RCT negated efficacy and emphasizes high heterogeneity and methodological limitations. Overall: mixed evidence, with a modest average reduction in diarrhea duration across trials, but inconsistent results.

  • High-altitude intestinal dysfunction (mice; LGG + stachyose): The combination (STA + LGG) was reported to more effectively improve microbiota disruption, increase SCFAs (especially butyrate), improve tight junction/barrier-related outcomes, increase anti-inflammatory/antioxidant markers (e.g., TGF-β, SOD, CAT, GSH-Px), and reduce pro-inflammatory cytokines and HIF-1α compared with STA or LGG alone. This supports potential benefit, but it is animal data and the strongest effects were for the synbiotic, not LGG alone.

  • Aluminum-induced neurotoxicity/hepatotoxicity (rats): In AlCl3-intoxicated rats, combined sesamol + L. rhamnosus reduced amyloid-β, p-tau, GSK-3β, inflammatory/apoptotic biomarkers and improved Wnt/β-catenin-related markers, with supportive behavioral and histopathology findings; also improved multiple liver inflammatory/fibrotic/apoptotic markers. This suggests potential as an add-on in this model, but it is preclinical and uses a toxin-induced model rather than human disease.

  • UC/IBD: The provided UC/IBD abstracts state probiotics may help prevent onset/relapse, but they do not provide specific trial results for L. rhamnosus in UC/IBD. From the provided text alone, efficacy for UC/IBD cannot be concluded.

  • Metabolic/immune in vitro findings (strain 4B15): L. rhamnosus 4B15 showed comparatively higher antioxidant activity, α-glucosidase inhibition, cholesterol-lowering potential, and reduced nitric oxide and inflammatory mediators in LPS-stimulated macrophages. These are mechanistic/in vitro signals and do not establish clinical efficacy.

3. What health benefits does it have?

  • Potential gut–brain axis effects (strain-specific; preclinical): JB-1 altered GABA receptor subunit mRNA in multiple brain regions and reduced stress-induced corticosterone and anxiety-/depression-like behavior in mice; effects required an intact vagus nerve.

  • Possible modest benefit in pediatric acute gastroenteritis (LGG; mixed clinical evidence): Across multiple RCTs in a review, LGG was associated with ~0.85 day shorter diarrhea duration on average, though results are heterogeneous and at least one large RCT found no benefit.

  • Intestinal barrier and anti-inflammatory/antioxidant effects (preclinical; strongest as synbiotic): In hypobaric hypoxia mice, STA + LGG increased SCFAs (notably butyrate), improved markers consistent with tighter barrier function, increased antioxidant enzymes, and reduced inflammatory cytokines and hypoxia-related signaling (HIF-1α).

  • Immunomodulatory signals (in vitro; strain 4B15): Reduced nitric oxide and inflammatory mediators (e.g., TNF-α, IL-6, IL-1β) in LPS-stimulated macrophages, suggesting anti-inflammatory potential (requires confirmation in humans).

  • Neuroprotective/hepatoprotective signals in toxin model (rats; combination therapy): In AlCl3 exposure, L. rhamnosus with sesamol improved multiple neurodegeneration-associated and liver injury biomarkers and histopathology/behavioral outcomes (preclinical, combination-dependent).

4. Does it have any downsides or side effects?

  • Risk of probiotic-associated infection in critically ill patients (LGG; strong clinical signal): In the large ICU RCT, 15 patients (1.1%) receiving LGG vs 1 (0.1%) receiving placebo had an adverse event where L. rhamnosus was found in a sterile site or as the sole/predominant organism in a nonsterile site (odds ratio 14.02; 95% CI 1.79–109.58; P<.001). This indicates a clinically important safety concern in this high-risk population.

  • Lack of benefit in some settings may shift risk–benefit negative: In mechanically ventilated ICU patients, LGG provided no efficacy for VAP or other outcomes, making any infection risk more consequential.

  • General limitations from the provided evidence: Many claimed benefits are from animal or in vitro studies; safety and side-effect profiles in the general population cannot be fully inferred from these abstracts alone.

5. Is it beneficial or harmful for any genetic variations (pharmacogenomics)?

The provided abstracts do not report pharmacogenomic analyses (e.g., outcomes stratified by human genetic variants) for L. rhamnosus strains (JB-1, GG/LGG, 4B15) or for synbiotic combinations.

  • No direct evidence here that specific human genetic variants make L. rhamnosus more beneficial or harmful.

  • The closest mechanistic hints are pathway-level findings in animals (e.g., vagus-nerve dependence for JB-1’s behavioral effects; Wnt/β-catenin-related markers in an AlCl3 rat model), but these are not genotype-stratified and cannot be translated into pharmacogenomic recommendations.

References

  1. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve.
    Javier A Bravo, Paul Forsythe, Marianne V Chew, Emily Escaravage, Hélène M Savignac, Timothy G Dinan, John Bienenstock, John F Cryan (2011) - Proceedings of the National Academy of Sciences of the United States of America
  2. Effect of Probiotics on Incident Ventilator-Associated Pneumonia in Critically Ill Patients: A Randomized Clinical Trial.
    Jennie Johnstone, Maureen Meade, François Lauzier, John Marshall, Erick Duan, Joanna Dionne, Yaseen M Arabi, Diane Heels-Ansdell, Lehana Thabane, Daphnee Lamarche, Michael Surette, Nicole Zytaruk, Sangeeta Mehta, Peter Dodek, Lauralyn McIntyre, Shane English, Bram Rochwerg, Tim Karachi, William Henderson, Gordon Wood, Daniel Ovakim, Margaret Herridge, John Granton, M Elizabeth Wilcox, Alberto Goffi, Henry T Stelfox, Daniel Niven, John Muscedere, François Lamontagne, Frédérick D'Aragon, Charles St-Arnaud, Ian Ball, Dave Nagpal, Martin Girard, Pierre Aslanian, Emmanuel Charbonney, David Williamson, Wendy Sligl, Jan Friedrich, Neill K Adhikari, François Marquis, Patrick Archambault, Kosar Khwaja, Arnold Kristof, James Kutsogiannis, Ryan Zarychanski, Bojan Paunovic, Brenda Reeve, François Lellouche, Paul Hosek, Jennifer Tsang, Alexandra Binnie, Sébastien Trop, Osama Loubani, Richard Hall, Robert Cirone, Steve Reynolds, Paul Lysecki, Eyal Golan, Rodrigo Cartin-Ceba, Robert Taylor, Deborah Cook (2021) - JAMA
  3. Lactobacillus rhamnosus GG Derived Extracellular Vesicles Modulate Gut Microbiota and Attenuate Inflammatory in DSS-Induced Colitis Mice.
    Lingjun Tong, Xinyi Zhang, Haining Hao, Qiqi Liu, Zihan Zhou, Xi Liang, Tongjie Liu, Pimin Gong, Lanwei Zhang, Zhengyuan Zhai, Yanling Hao, Huaxi Yi (2021) - Nutrients
  4. Stachyose in combination with L. rhamnosus GG ameliorates acute hypobaric hypoxia-induced intestinal barrier dysfunction through alleviating inflammatory response and oxidative stress.
    Dingxin Ren, Mengying Ding, Junqing Su, Jianzhou Ye, Xiaoqin He, Yafeng Zhang, Xiaoya Shang (2024) - Free radical biology & medicine
  5. Probiotic and anti-inflammatory potential of Lactobacillus rhamnosus 4B15 and Lactobacillus gasseri 4M13 isolated from infant feces.
    Nam Su Oh, Jae Yeon Joung, Ji Young Lee, Younghoon Kim (2018) - PloS one
  6. The Potential Therapeutic Role of
    Hang Guo, Leilei Yu, Fengwei Tian, Wei Chen, Qixiao Zhai (2023) - Foods (Basel, Switzerland)
  7. Lacticaseibacillus rhamnosus alleviates intestinal inflammation and promotes microbiota-mediated protection against Salmonella fatal infections.
    Xianqi Peng, Abdelaziz Ed-Dra, Yan Song, Mohammed Elbediwi, Reshma B Nambiar, Xiao Zhou, Min Yue (2022) - Frontiers in immunology
  8. The protective effects of sesamol and/or the probiotic,Lactobacillus rhamnosus, against aluminum chloride-induced neurotoxicity and hepatotoxicity in rats: Modulation of Wnt/β-catenin/GSK-3β, JAK-2/STAT-3, PPAR-γ, inflammatory, and apoptotic pathways
    Karema Abu-Elfotuh, Heba Mohammed Refat M Selim, Omnia Karem M Riad, Ahmed M E Hamdan, Soha Osama Hassanin (2023)
  9. Investigating the therapeutic potential of
    Nafiseh Erfanian, Hossein Safarpour, Tahmineh Tavakoli, Mohammad Ali Mahdiabadi, Saeed Nasseri, Mohammad Hassan Namaei (2024) - Iranian journal of microbiology
  10. Systematic review with meta-analysis: Lactobacillus rhamnosus GG for treating acute gastroenteritis in children - a 2019 update.
    Hania Szajewska, Maciej Kołodziej, Dorota Gieruszczak-Białek, Agata Skórka, Marek Ruszczyński, Raanan Shamir (2019) - Alimentary pharmacology & therapeutics
  11. Effect of
    Marco Toscano, Roberta De Grandi, Laura Stronati, Elena De Vecchi, Lorenzo Drago (2017) - World journal of gastroenterology
  12. Inhibitory effect of lactobacilli supernatants on biofilm and filamentation of
    Yeuklan Poon, Mamie Hui (2023) - Frontiers in microbiology
  13. Antimicrobial Effect of Copper Nanoparticles on Relevant Supragingival Oral Bacteria.
    Nia Oetiker, Daniela Salinas, Joaquín Lucero-Mora, Rocío Orellana, Mariana Quiroz-Muñoz, Denisse Bravo, José M Pérez-Donoso (2024) - Microorganisms
  14. Effect of Probiotics
    Silvia D'Agostino, Giulia Valentini, Francesca Iarussi, Marco Dolci (2024) - Dentistry journal
  15. Probiotic, Postbiotic, and Paraprobiotic Effects of
    Gabriela López-Almada, María Esther Mejía-León, Norma Julieta Salazar-López (2024) - Foods (Basel, Switzerland)
  16. Lactobacillus paracasei HII01 enhances lifespan and promotes neuroprotection in Caenorhabditis elegans.
    Kishoree K Kumaree, Mani Iyer Prasanth, Bhagavathi Sundaram Sivamaruthi, Periyanaina Kesika, Tewin Tencomnao, Chaiyavat Chaiyasut, Anchalee Prasansuklab (2023) - Scientific reports
  17. Antibacterial and antibiofilm potential of Lacticaseibacillus rhamnosus YT and its cell-surface extract.
    Chengran Guan, Wenjuan Zhang, Jianbo Su, Feng Li, Dawei Chen, Xia Chen, Yujun Huang, Ruixia Gu, Chenchen Zhang (2023) - BMC microbiology
  18. Selection of New Probiotics for Endometrial Health.
    Empar Chenoll, Inmaculada Moreno, María Sánchez, Iolanda Garcia-Grau, Ángela Silva, Marta González-Monfort, Salvador Genovés, Felipe Vilella, Cristina Seco-Durban, Carlos Simón, Daniel Ramón (2019) - Frontiers in cellular and infection microbiology
  19. The effect of synbiotic-fluoride therapy on multi-species biofilm.
    Mohammed Nadeem Bijle, Mohamed Mahmoud Abdalla, Ivan Fan Ngai Hung, Cynthia Kar Yung Yiu (2023) - Journal of dentistry
  20. Antimicrobial Substances and Mechanisms of Lactobacillus rhamnosus against Gardnerella vaginalis.
    Yu-Ping Huang, Jie-Yan Shi, Si-Chen Luo, Shao-Yan Xu, Jia-Dong Zhang, István Molnár, Qiong-Qiong Yang, Bo-Bo Zhang (2023) - Probiotics and antimicrobial proteins


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