Exercise stimulates hepatic mitochondrial adaptations; however, the mechanisms remain largely unknown. Here we tested if FGF21 plays an obligatory role in exercise induced hepatic mitochondrial adaptations by testing exercise responses in FGF21 knockout mice. FGF21 knockout (FGF21-KO) and wild-type (WT) mice (11-12 weeks of age) had access to voluntary running wheels for exercise (EX) or remained sedentary for 8 weeks. FGF21 deficiency resulted in greater body weight, adiposity, serum cholesterol, insulin, and glucose concentrations compared with WT mice (p<0.05). In addition, hepatic mitochondrial complete palmitate oxidation, β-hydroxyacyl-CoA dehydrogenase (β-HAD) activity, and nuclear content of PGC-1α were 30-50% lower in FGF21-KO mice compared with WT mice (p<0.01). EX effectively lowered body weight, adiposity, serum triglycerides, free fatty acids, and insulin, and normalized mitochondrial complete palmitate oxidation in the FGF21-KO mice. While the reduced hepatic β-HAD activity and lowered nuclear content of PGC-1α in FGF21-KO mice was not restored by EX. In addition, EX increased hepatic CPT-1α mRNA expression and ACC phosphorylation (a marker of increased AMPK activity) and reduced hepatic TAG content in both genotypes. However, FGF21-KO mice displayed a lower EX-induced increase in the mRNA expression of the hepatic gluconeogenic gene, PEPCK, compared to WT. In conclusion, FGF21 does not appear necessary for exercise-induced systemic and hepatic mitochondrial adaptations, but the increased adiposity, hyperinsulinemia and impairments in hepatic mitochondrial function induced by FGF21 deficiency can be partially rescued by daily wheel running exercise.
- Copyright © 2015, American Journal of Physiology- Gastrointestinal and Liver Physiology