Hepatic AMP-Activated Protein Kinase Governs Adaptations in Liver Glucose Fluxes and Lipid Homeostasis in Response to Exercise Training in Mice

During acute exercise the liver increases glycogenolysis and the energetically costly process of gluconeogenesis to supply glucose to the working muscle. In response to exercise training, the liver undergoes adaptations in glucose and lipid metabolic pathways to more effectively meet the ATP demand of the next exercise bout. We tested the hypothesis that the energy sensor and master regulator of ATP provision, AMP-activated protein kinase (AMPK), is necessary for liver glucose and lipid adaptations to exercise training. This was accomplished by studying mice with liver-specific deletion of AMPK α1 and α2 subunits (KO) and wild type (WT) littermates undergoing sedentary and exercise training protocols. In vivo isotope infusions combined with 2H/13C metabolic flux analysis quantified liver nutrient fluxes at rest and during treadmill running. Liver metabolite concentrations and the expression of molecular regulators of liver nutrient metabolism were evaluated. The results of this study showed that liver glycogen deposition in response to exercise training was impaired in KO compared to WT mice and that this lower glycogen availability resulted in diminished glycogenolysis, glucose production, and circulating glucose during acute exercise. Exercise training decreased liver diacylglycerides (DAGs) in both genotypes, however, the response was less pronounced in KO mice. Moreover, exercise training led to higher liver triacylglycerides (TAGs) in KO mice. A lack of AMPK action prevented exercise training from promoting the desaturation of DAG fatty acyl chains as evidenced by higher 16:1/16:0 and 18:1/18:0 ratios in KO mice. Unexpectedly, the differences in DAG fatty acyl chain composition between genotypes were not observed in TAGs. Together, these results suggest that AMPK is a critical regulator of the liver glycogen and lipid availability and selectively remodels DAG fatty acyl chain composition in response to exercise training. Disclosure C.C.Hughey: None. D.Bracy: None. L.Lantier: None. M.Foretz: None. B.Viollet: None. D.Wasserman: None. Funding National Institutes of Health (DK050277, DK054902, DK059637, DK020593)