Background: Supplementation of a high-fat obesogenic diet (HFD) with cholic acid (CA) suppresses the development of obesity, insulin resistance, and hepatic steatosis in mice.
Objective: We investigated the role of fibroblast growth factor 21 (FGF21) in mediating the beneficial actions of CA on metabolic syndrome.
Methods: Male 7-wk-old wild-type (WT) mice and FGF21 knockout (FGF21KO) mice were fed an HFD for 12 wk followed by a 4-wk period in which the mice were fed the HFD alone or supplemented with 0.5% CA. Body composition, gross energy efficiency, glucose tolerance, homeostasis model assessment of insulin resistance (HOMA-IR), and hepatic triacylglycerol (TG) concentrations were measured.
Results: CA administration improved glucose tolerance and decreased total body fat accretion, gross energy efficiency, fasting blood glucose concentrations, and HOMA-IR in both WT mice and FGF21KO mice. The extent of the effect of CA on glucose tolerance, fasting blood glucose concentrations, and HOMA-IR was similar in both mouse strains, whereas the extent of the effect of CA on total body fat accretion and gross energy efficiency was 4.2- to 4.4-fold greater in FGF21KO mice than in WT mice. Further analyses showed that CA decreased hepatic TG concentrations in WT mice (49%) but had no effect on hepatic TG concentrations in FGF21KO mice. CA decreased the activation state of hepatic acetyl-CoA carboxylase 1 (ACC1) and adipose tissue hormone-sensitive lipase (HSL) in WT mice but was not effective in decreasing the activation of ACC1 and HSL in FGF21KO mice.
Conclusions: FGF21 signaling is required for the beneficial effect of CA on hepatic TG accumulation in mice fed an HFD. We propose that FGF21 signaling potentiates the ability of CA to decrease the activation of ACC1 and HSL, key enzymes controlling the supply of long-chain fatty acid precursors for hepatic TG synthesis.