Impact of 4 weeks of western diet and aerobic exercise training on whole‐body phenotype and skeletal muscle mitochondrial respiration in male and female mice

Abstract High dietary fat intake induces significant whole‐body and skeletal muscle adaptations in mice, including increased capacity for fat oxidation and mitochondrial biogenesis. The impact of a diet that is high in fat and simple sugars (i.e., western diet [WD]), particularly on regulation of skeletal muscle mitochondrial function, is less understood. The purpose of the current study was to determine physiologic adaptations in mitochondrial respiratory capacity in skeletal muscle during short‐term consumption of WD, including if adaptive responses to WD‐feeding are modified by concurrent exercise training or may be sex‐specific. Male and female C57BL/6J mice were randomized to consume low‐fat diet (LFD) or WD for 4 weeks, with some WD‐fed mice also performing concurrent treadmill training (WD + Ex). Group sizes were n = 4–7. Whole‐body metabolism was measured using in‐cage assessment of food intake and energy expenditure, DXA body composition analysis and insulin tolerance testing. High‐resolution respirometry of mitochondria isolated from quadriceps muscle was used to determine skeletal muscle mitochondrial respiratory function. Male mice fed WD gained mass (p