The Associations between Circulating Bile Acids and the Muscle Volume in Patients with Non-alcoholic Fatty Liver Disease (NAFLD)

Objective Non-alcoholic fatty liver disease (NAFLD) is frequently associated with obesity, dyslipidemia and type-2 diabetes mellitus. Bile acids (BAs) bind to the farnesoid X receptor (FXR) and G protein-coupled receptor 5 (TGR5), which are involved in lipid and glucose metabolism and energy expenditure. The present study aimed to determine associations between the circulating BAs and the skeletal muscle volume (SMV), and lipid and glucose metabolism in patients with NAFLD. Methods Serum BAs and metabolic parameters were measured in 55 patients with NAFLD (median age, 55 years). The changes (Δ) in serum BA (ΔBA) and metabolic parameters were determined in 17 patients (male, n=10; female, n=7) who received nutritional counseling for 12 months. Results Spearman's test revealed that the levels of 12α-hydroxysterol (12α-OH) BAs, including deoxycholic acid (DCA), were inversely correlated with the SMV of the upper and lower limbs and the total SMV. A multivariate analysis revealed that the level of DCA was correlated with a reduced total SMV, whereas non-12α-OH BAs, including chenodeoxycholic acid (CDCA), were correlated with an increased SMV of the lower limbs. Changes in CDCA were positively correlated with the ΔSMV of the lower limbs, and inversely correlated with the Δwaist-hip ratio and Δtotal cholesterol. Changes in the total non-12α-OH BA level were positively correlated with the ΔSMV of the lower limbs. Conclusion Circulating BAs were associated with SMV. The 12α-OH BAs, including DCA were associated with reduced SMV levels, whereas non-12α-OH BAs including CDCA were associated with increased SMV levels. The molecular mechanisms underlying the association between the BA levels and the SMV remain to be explored.