Abstract
Beyond adipose and muscle, excerise has profound effects in other metabolically‐important tissues including the liver. Bile acids (BAs) are synthesized from cholesterol via the rate‐limiting enzyme cholesterol 7 alpha‐hydroxylase (CYP7A1) and contribute to the solubilization and absorption of lipid soluble nutrients, and serve as important signaling molecules capable of systemic endocrine function. Circulating BA are known to be higher in obesity and insulin resistance, but effects following exercise and diet‐induced weight loss are unknown. To test if improved fitness and weight loss influence bile acid metabolism and homeostasis, we measured fasting serum concentrations of total BAs (conjugated and free forms of primary and secondary BAs) in sedentary, obese insulin‐resistant women (N=12) before and after a ~14 wk weight loss and exercise intervention [Campell et al. 2014, PLoS One, 9: e84260]. In addition, serum FGF19 (a regulator of BA synthesis) and 7‐alpha‐hydroxy‐cholesten‐3‐one (C4, a verified marker of CYP7A1 enzymatic acitivity) were measured by ELISA and LC‐MS, respectively. Using mixed‐model analyses and the change in relative VO2peak (mL/min/kg) as a covariate, we observed a significant decrease (~30%) in total serum BAs post‐intervention relative to pre‐intervention samples. Corresponding to the decrease in total BAs, fasting serum concentrations of C4 were 55% higher post‐intervention relative to the matched pre‐intervention samples (P=0.004). Interestingly, we observed no changes in serum FGF19. These data suggest that weight loss and/or improved fitness altered BA metabolism marked by increased hepatic BA synthesis and reduced serum BA. The underlying mechanisms remain to be determined, but work from our preclinical rodent models supports the idea that increased BA metabolic flux is linked to enhanced hepatic mitochondrial function.
Support or Funding Information
This work was supported by USDA Projects 6026‐51000‐010‐05S and 2032‐51530‐022‐00D, and NIH‐NIDDK R01DK078328 and NIDDK U24 DK097154.
This is from the Experimental Biology 2019 Meeting. There is no full text article associated with this published in The FASEB Journal.