Voluntary Running Attenuates Metabolic Dysfunction in Ovariectomized Low-Fit Rats.

INTRODUCTION: Ovariectomy and high-fat diet (HFD) worsen obesity and metabolic dysfunction associated with low aerobic fitness. Exercise training mitigates metabolic abnormalities induced by low aerobic fitness, but whether the protective effect is maintained after ovariectomy and HFD is unknown.

PURPOSE: This study determined whether, after ovariectomy and HFD, exercise training improves metabolic function in rats bred for low intrinsic aerobic capacity.

METHODS: Female rats selectively bred for low (LCR) and high (HCR) intrinsic aerobic capacity (n = 30) were ovariectomized, fed HFD, and randomized to either a sedentary (SED) or voluntary wheel running (EX) group. Resting energy expenditure, glucose tolerance, and spontaneous physical activity were determined midway through the experiment, whereas body weight, wheel running volume, and food intake were assessed throughout the study. Body composition, circulating metabolic markers, and skeletal muscle gene and protein expression were measured at sacrifice.

RESULTS: EX reduced body weight and adiposity in LCR rats (-10% and -50%, respectively; P < 0.05) and, unexpectedly, increased these variables in HCR rats (+7% and +37%, respectively; P < 0.05) compared with their respective SED controls, likely because of dietary overcompensation. Wheel running volume was approximately fivefold greater in HCR than LCR rats, yet EX enhanced insulin sensitivity equally in LCR and HCR rats (P < 0.05). This EX-mediated improvement in metabolic function was associated with thee gene upregulation of skeletal muscle interleukin-6 and interleukin-10. EX also increased resting energy expenditure, skeletal muscle mitochondrial content (oxidative phosphorylation complexes and citrate synthase activity), and adenosine monophosphate-activated protein kinase activation similarly in both lines (all P <0.05).

CONCLUSION: Despite a fivefold difference in running volume between rat lines, EX similarly improved systemic insulin sensitivity, resting energy expenditure, and skeletal muscle mitochondrial content and adenosine monophosphate-activated protein kinase activation in ovariectomized LCR and HCR rats fed HFD compared with their respective SED controls.