Comprehensive Clinical and Genetic Analyses of Circulating Bile Acids and Their Associations With Diabetes and Its Indices.

Bile acids (BAs) are cholesterol-derived compounds that regulate glucose, lipid, and energy metabolism. Despite their significance in glucose homeostasis, the association between specific BA molecular species and their synthetic pathways with diabetes is unclear. Here, we used a recently validated, stable-isotope dilution, high-performance liquid chromatography with tandem mass spectrometry method to quantify a panel of BAs in fasting plasma from 2,145 study participants and explored structural and genetic determinants of BAs linked to diabetes, insulin resistance, and obesity. Multiple 12α-hydroxylated BAs were associated with diabetes (adjusted odds ratio [aOR] range, 1.3–1.9; P < 0.05 for all) and insulin resistance (aOR range, 1.3–2.2; P < 0.05 for all). Conversely, multiple 6α-hydroxylated BAs and isolithocholic acid (iso-LCA) were inversely associated with diabetes and obesity (aOR range, 0.3–0.9; P < 0.05 for all). Genome-wide association studies revealed multiple genome-wide significant loci linked with 9 of the 14 diabetes-associated BAs, including a locus for iso-LCA (rs11866815). Mendelian randomization analyses showed genetically elevated deoxycholic acid levels were causally associated with higher BMI, and iso-LCA levels were causally associated with reduced BMI and diabetes risk. In conclusion, comprehensive, large-scale, quantitative mass spectrometry and genetics analyses show circulating levels of multiple structurally specific BAs, especially DCA and iso-LCA, are clinically associated with and genetically linked to obesity and diabetes. Article Highlights: The association between specific circulating bile acid (BA) molecular species and diabetes in humans is not extensively studied. In the present study, we found that multiple 12α-hydroxylated BAs are positively associated with diabetes and insulin resistance, whereas multiple 6α-hydroxylated BAs are inversely associated with diabetes and obesity. Mendelian randomization analyses show isolithocholic acid levels are causally associated with reduced risk for diabetes and obesity, and deoxycholic acid levels are causally associated with obesity risk. The findings of this study provide new avenues for investigating the role of BAs in metabolic diseases and may have substantial therapeutic implications. [ABSTRACT FROM AUTHOR]