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

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d129662e198">INTRODUCTION</h5> <p id="P1">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 following ovariectomy and HFD is unknown. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d129662e203">PURPOSE</h5> <p id="P2">This study determined whether, following ovariectomy and HFD, exercise training improves metabolic function in rats bred for low intrinsic aerobic capacity. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d129662e208">METHODS</h5> <p id="P3">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, while 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 was measured at sacrifice. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d129662e213">RESULTS</h5> <p id="P4">EX reduced body weight and adiposity in LCR rats (−10% and −50%, respectively; <i>P</i>&lt;0.05) and, unexpectedly, increased these variables in HCR rats (+7% and +37%, respectively; <i>P</i>&lt;0.05) compared to their respective SED controls, likely due to dietary overcompensation. Wheel running volume was ~5-fold greater in HCR than LCR rats, yet EX enhanced insulin sensitivity equally in LCR and HCR rats ( <i>P</i>&lt;0.05). This EX-mediated improvement in metabolic function was associated with gene up-regulation of skeletal muscle IL-6&amp;-10. EX also increased resting energy expenditure, skeletal muscle mitochondrial content (oxidative phosphorylation complexes and citrate synthase activity), and AMPK activation similarly in both lines (all <i>P</i> &lt;0.05). </p> </div><div class="section"> <a class="named-anchor" id="S5"> <!-- named anchor --> </a> <h5 class="section-title" id="d129662e230">CONCLUSION</h5> <p id="P5">Despite a 5-fold difference in running volume between rat lines, EX similarly improved systemic insulin sensitivity, resting energy expenditure, and skeletal muscle mitochondrial content and AMPK activation in ovariectomized LCR and HCR rats fed HFD compared to their respective SED controls. </p> </div>