Bile acids and the gut microbiome : Current Opinion in Gastroenterology (original) (raw)
BILIARY TRACT: Edited by Gregory J. Gores
Ridlon, Jason M.a,b; Kang, Dae J.a; Hylemon, Phillip B.a,b; Bajaj, Jasmohan S.b,c
aDepartment of Microbiology and Immunology, Virginia Commonwealth University
bMcGuire VA Medical Center
cDivision of Gastroenterology, Hepatology and Nutrition, Virginia Commonwealth University, Richmond, Virginia, USA.
Correspondence to Jasmohan S. Bajaj, MD, MS, MBBS, Division of Gastroenterology, Hepatology and Nutrition, Virginia Commonwealth University and McGuire VA Medical Center, 1201 Broad Rock Boulevard, Richmond, Virginia 23249, USA. Tel: +1 (804) 675 5802; fax: +1 (804) 675 5816; e-mail: [email protected]
Abstract
Purpose of review
We examine the latest research on the emerging bile acid-gut microbiome axis and its role in health and disease. Our focus revolves around two key microbial pathways for degrading bile salts, and the impact of bile acid composition in the gut on the gut microbiome and host physiology.
Recent findings
Bile acid pool size has recently been shown to be a function of microbial metabolism of bile acids in the intestines. Recent studies have shown potential mechanisms explaining how perturbations in the microbiome affect bile acid pool size and composition. Bile acids are emerging as regulators of the gut microbiome at the highest taxonomic levels. The role of bile acids as hormones and potentiators of liver cancer is also emerging.
Summary
The host and microbiome appear to regulate bile acid pool size. The host produces a large, conjugated hydrophilic bile acid pool, maintained through positive-feedback antagonism of farnesoid X receptor (FXR) in intestine and liver. Members of the microbiome utilize bile acids and their conjugates resulting in agonism of FXR in intestine and liver resulting in a smaller, unconjugated hydrophobic bile acid pool. Hydrophilicity of the bile acid pool is associated with disease states. Reduced bile acid levels in the gut are associated with bacterial overgrowth and inflammation. Diet, antibiotic therapy, and disease states affect the balance of the microbiome-bile acid pool.
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