Bile acid metabolism (microbial)
DEMikrobieller Gallensäuren-Metabolismus
Bile acids begin as digestion helpers. But they double as powerful signals, and your gut bacteria reshape them. Your liver makes the 'primary' ones from cholesterol. There are two: cholic acid and chenodeoxycholic acid. The liver attaches glycine or taurine, then sends them to your small intestine. There, gut microbes rework them step by step. The steps include deconjugation and 7α-dehydroxylation. The result is a varied set of 'secondary' bile acids. Examples are deoxycholic acid (DCA) and lithocholic acid (LCA). Two more are ursodeoxycholic acid (UDCA) and isoallo-lithocholic acid (isoallo-LCA). The secondary forms do more than break up fat. They act on two receptors, FXR and TGR5. Through them, they tune your blood sugar, fat handling, energy burn, and immune tone. Isoallo-LCA is a longevity standout. It strongly nudges immune cells to become calming regulatory T cells (Tregs). And it is enriched in centenarians (Sato et al. 2021). A cousin, 3-oxoLCA, holds back inflammatory Th17 cells. Which secondary bile acids you carry depends on your microbes. Key players are species in the Lachnospiraceae and Ruminococcaceae families. And the mix shifts a lot in aging, obesity, and bowel disease.
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