Cell Metabolism
Volume 20, Issue 5, 4 November 2014, Pages 799-812
Journal home page for Cell Metabolism

Article
γ-Butyrobetaine Is a Proatherogenic Intermediate in Gut Microbial Metabolism of L-Carnitine to TMAO

https://doi.org/10.1016/j.cmet.2014.10.006Get rights and content
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Highlights

  • γ-butyrobetaine (γBB) is a major gut microbial metabolite of L-carnitine in mice

  • γBB is an intermediate in gut microbe-dependent formation of TMAO from L-carnitine

  • Gut microbiota-generated γBB is atherogenic in the C57BL/6J Apoe−/− mouse model

  • Distinct microbes are associated with γBB or TMA/TMAO production from carnitine

Summary

L-carnitine, a nutrient in red meat, was recently reported to accelerate atherosclerosis via a metaorganismal pathway involving gut microbial trimethylamine (TMA) formation and host hepatic conversion into trimethylamine-N-oxide (TMAO). Herein, we show that following L-carnitine ingestion, γ-butyrobetaine (γBB) is produced as an intermediary metabolite by gut microbes at a site anatomically proximal to and at a rate ∼1,000-fold higher than the formation of TMA. Moreover, we show that γBB is the major gut microbial metabolite formed from dietary L-carnitine in mice, is converted into TMA and TMAO in a gut microbiota-dependent manner (like dietary L-carnitine), and accelerates atherosclerosis. Gut microbial composition and functional metabolic studies reveal that distinct taxa are associated with the production of γBB or TMA/TMAO from dietary L-carnitine. Moreover, despite their close structural similarity, chronic dietary exposure to L-carnitine or γBB promotes development of functionally distinct microbial communities optimized for the metabolism of L-carnitine or γBB, respectively.

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