Cited by 327Gut microbiota and healthNutritional Studies and DietPolyamine Metabolism and Applications

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l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans

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Abstract

BACKGROUND: l-Carnitine, an abundant nutrient in red meat, accelerates atherosclerosis in mice via gut microbiota-dependent formation of trimethylamine (TMA) and trimethylamine N-oxide (TMAO) via a multistep pathway involving an atherogenic intermediate, γ-butyrobetaine (γBB). The contribution of γBB in gut microbiota-dependent l-carnitine metabolism in humans is unknown. METHODS: Omnivores and vegans/vegetarians ingested deuterium-labeled l-carnitine (d3-l-carnitine) or γBB (d9-γBB), and both plasma metabolites and fecal polymicrobial transformations were examined at baseline, following oral antibiotics, or following chronic (≥2 months) l-carnitine supplementation. Human fecal commensals capable of performing each step of the l-carnitine→γBB→TMA transformation were identified. RESULTS: Studies with oral d3-l-carnitine or d9-γBB before versus after antibiotic exposure revealed gut microbiota contribution to the initial 2 steps in a metaorganismal l-carnitine→γBB→TMA→TMAO pathway in subjects. Moreover, a striking increase in d3-TMAO generation was observed in omnivores over vegans/vegetarians (>20-fold; P = 0.001) following oral d3-l-carnitine ingestion, whereas fasting endogenous plasma l-carnitine and γBB levels were similar in vegans/vegetarians (n = 32) versus omnivores (n = 40). Fecal metabolic transformation studies, and oral isotope tracer studies before versus after chronic l-carnitine supplementation, revealed that omnivores and vegans/vegetarians alike rapidly converted carnitine to γBB, whereas the second gut microbial transformation, γBB→TMA, was diet inducible (l-carnitine, omnivorous). Extensive anaerobic subculturing of human feces identified no single commensal capable of l-carnitine→TMA transformation, multiple community members that converted l-carnitine to γBB, and only 1 Clostridiales bacterium, Emergencia timonensis, that converted γBB to TMA. In coculture, E. timonensis promoted the complete l-carnitine→TMA transformation. CONCLUSION: In humans, dietary l-carnitine is converted into the atherosclerosis- and thrombosis-promoting metabolite TMAO via 2 sequential gut microbiota-dependent transformations: (a) initial rapid generation of the atherogenic intermediate γBB, followed by (b) transformation into TMA via low-abundance microbiota in omnivores, and to a markedly lower extent, in vegans/vegetarians. Gut microbiota γBB→TMA/TMAO transformation is induced by omnivorous dietary patterns and chronic l-carnitine exposure. TRIAL REGISTRATION: ClinicalTrials.gov NCT01731236. FUNDING: NIH and Office of Dietary Supplements grants HL103866, HL126827, and DK106000, and the Leducq Foundation.

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Metadata

Authors
Koeth, R. A., Lam-Galvez, B. R., Kirsop, J., Wang, Z., Levison, B. S., Gu, X., Copeland, M. F., Bartlett, D., Cody, D. B., Dai, H. J., Culley, M. K., Li, X. S., Fu, X., Wu, Y., Li, L., DiDonato, J. A., Tang, W. H. W., Garcia-Garcia, J. C., & Hazen, S. L.
Affiliations
  • Cleveland Clinic (US)
  • Cleveland Clinic Lerner College of Medicine (US)
  • Procter & Gamble (United States) (US)
  • Cleveland State University (US)
Venue
Journal of Clinical Investigation
Published
2018-12-10
Volume
129
Issue
1
Pages
373-387
ISSN
  • 0021-9738 (ISSN-L)
  • 1558-8238
OpenAlex
W2903641122
Cited by
327
References
65
Citations by year
2026: 25 · 2025: 44 · 2024: 37 · 2023: 48 · 2022: 47 · 2021: 51 · 2020: 51 · 2019: 23 · 2018: 1
FWCI
11.21
Type
journal article
Language
en
Open access
Locations
  • Journal of Clinical Investigation (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
NIH and Office of Dietary Supplements (HL103866, HL126827, DK106000)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Gut microbiota and health
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Polyamine Metabolism and Applications
Keywords
L-carnitine, trimethylamine N-oxide, trimethylamine, gamma-butyrobetaine, gut microbiota, atherosclerosis, omnivorous diet, vegan diet, Clostridiales, antibiotic exposure, plasma carnitine
MeSH terms
Vegans, Eubacteriales, Clostridiales, Gastrointestinal Microbiome, Animals, Betaine, Carnitine, Female, Humans, Male, Methylamines, Pilot Projects, Atherosclerosis, Mice

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