Exercise is an important lifestyle intervention for the prevention and treatment of NAFLD. Importantly, exercise can reduce hepatic steatosis independent of changes in body mass, which may stem from increased oxidative demand in liver during exercise. Increased hepatic gluconeogenesis (GNG) and tricarboxylic acid (TCA) cycle flux have been observed during exercise in rodents, but it is unclear whether this adaptation is chronically maintained outside of the exercise window. Liver metabolism is also altered by nutritional status. Fasting promotes hepatic fat oxidation, ketogenesis and GNG, while feeding promotes glycogen storage and fat synthesis. Hence, fasting and exercise may have a positive interaction, whereas exogenous nutrient intake or glucose infusion is known to reduce the induction of GNG during exercise. Here, we tested whether nutritional status impacts exercise induced hepatic metabolic adaptations. Sprague-Dawley rats were kept sedentary or provided voluntary wheel running (VWR) for 4 weeks in the presence or absence of food restriction during the dark phase when rats spontaneously run. Experiments were conducted one day following the last exercise bout. Hepatic metabolic flux was examined by in vivo stable isotope infusions of [U-13C3]propionate, [3,4-13C2]glucose and 2H2O in rats using mass spectrometry and computational analysis. Chronic VWR in the fed state had no effect on basal hepatic fluxes outside of the exercise window. However, exercise during food restriction chronically induced a 2-fold induction of TCA cycle turnover, increase in GNG from glycerol and lowered ketogenesis outside of the exercise window. Thus, VWR during food restriction triggered an increase in hepatic energy demand that was sustained for at least 24 hours, while the effects of exercise in the fed state dissipated by 24 hours. These data suggest that acute nutritional state may be an important factor in the long-term programming of liver metabolism by exercise.
S.Deja: None. B.Kucejova: None. A.Maurer: None. M.N.Mizerska: None. X.Fu: None. J.P.Thyfault: None. S.C.Burgess: n/a.
National Institutes of Health (R01DK121497, R01DK078184, P41EB015908)