Targeting mitochondrial ROS production does not avert lipid-induced insulin resistance in muscle

Abstract

[eng] Aims/hypothesis High-fat, high-sucrose diet (HF)-induced reactive oxygen species (ROS) levels are implicated in skeletal muscle insulin resistance and mitochondrial dysfunction. Here we investigated whether mitochondrial ROS sequestering can circumvent HF-induced oxidative stress; we also determined the impact of any reduced oxidative stress on muscle insulin sensitivity and mitochondrial function. Methods The Skulachev ion (plastoquinonyl decyltriphe nylphosphonium) (SkQ), a mitochondria-specific antioxidant, was used to target ROS production in C2C12 muscle cells as well as in HF-fed (16 weeks old) male C57Bl/6 mice, compared with mice on low-fat chow diet (LF) or HF alone. Oxidative stress was measured as protein carbonylation levels. Glucose tolerance tests, glucose uptake assays and insulin-stimulated signalling were determined to assess muscle insulin sensitivity. Mitochondrial function was determined by high-resolution respirometry. Results SkQ treatment reduced oxidative stress in muscle cells (−23% p<0.05), but did not improve insulin sensi tivity and glucose uptake under insulin-resistant condi tions. In HF mice, oxidative stress was elevated (56% vs LF p<0.05), an effect completely blunted by SkQ. How ever, HF and HF+SkQ mice displayed impaired glucose tolerance (AUC HF up 33%, p<0.001; HF+SkQ up 22%; p<0.01 vs LF) and disrupted skeletal muscle insulin signalling. ROS sequestering did not improve mitochondrial function. Conclusions/interpretation SkQ treatment reduced muscle mitochondrial ROS production and prevented HF-induced oxidative stress. Nonetheless, whole-body glucose toler ance, insulin-stimulated glucose uptake, muscle insulin signalling and mitochondrial function were not improved. These results suggest that HF-induced oxidative stress is not a prerequisite for the development of muscle insulin resistance.