Microbial Bile Acid Metabolism

In all mammals, bile acids are derived from cholesterol in the liver. Cholic acid and chenodeoxycholic acid are common, but many other primary bile acids may be found. The primary bile acids are conjugated, usually with taurine or glycine, sometimes also with sulphate or glucuronate, and excreted into the bile. In the intestinal tract, the conjugated primary bile acids are attacked by microbial enzymes and converted into a variety of metabolites. The so-called secondary bile acids thus formed may then either be excreted with the feces, or reabsorbed, and sometimes further metabolized by hepatic enzymes to so-called tertiary bile acids before re-excretion in the bile. When present in the intestine, the bile acids (primary, secondary or tertiary) are subject to a number of microbial transformations such as deconjugation, desulfatation, deglucuronidation, dehydroxylation, and other oxidation-reduction reactions at the hydroxyl groups (8). In general, the metabolites formed are less water-soluble, less active in forming micelles, and sometimes more toxic to the host.

Over the years, many hypotheses have been brought forward regarding the influence(s) of various bile acids on several host-related signs and symptoms (intestinal motility, cell-turnover, bacterial over-growth, effects similar as pheromones, development of cancer etc). Obviously, further works on these areas are needed.

Pregnancy And Childbirth

Pregnancy And Childbirth

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