Targeting of mitochondrial reactive oxygen species production does not avert lipid-induced insulin resistance in muscle tissue from mice

Abstract

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 decyltriphenylphosphonium) (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 sensitivity and glucose uptake under insulin-resistant conditions. In HF mice, oxidative stress was elevated (56% vs LF p<0.05), an effect completely blunted by SkQ. However, 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 tolerance, 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.

High-Fat Diet–Induced Mitochondrial Biogenesis Is Regulated by Mitochondrial-Derived Reactive Oxygen Species Activation of CaMKII

“…We show that high-fat feeding increased the expression of the subunits of complex I and II ;50% (Fig. 4A and B, respectively), whereas trends for increases in complexes III and IV (P = 0.10; data not shown) were seen, supporting our previous work showing that SkQ prevents high-fat diet-induced increases in citrate synthase activity (12). These increases in markers of mitochondrial content were once again accompanied by increased CaMKII phosphorylation (Fig.…”

“…In support of this hypothesis, it has been previously shown that skeletal muscle with the lowest mitochondrial content has the highest propensity to emit mitochondrialderived H 2 O 2 (25). Although in the current study and in others (11,12) mitochondrial H 2 O 2 emission is increased following a high-fat diet, in theory, this could be exacerbated if mitochondrial biogenesis did not occur, but this remains to be determined. In addition, increasing the sensitivity of mitochondria to ADP, as proposed to occur following the induction of mitochondrial biogenesis (24), would increase the ability of ADP to dissipate protonmotive force and decrease mitochondrial ROS emission rates in vivo.…”

“…These data suggest that sarcoplasmic reticulum (SR) calcium release from the RyR is a primary mediator of mitochondrial biogenesis in conditions without large energy turnover. Calcium release from the RyR is also regulated by reactive oxygen species (ROS) (8)(9)(10), which coincides with high-fat feeding (11,12). Whether ROS-activated CaMKII signaling is a key mechanism inducing mitochondrial biogenesis in insulin resistant muscle remains to be determined.…”

In adipose tissue, increased mitochondrial emission of reactive oxygen species is important for short-term high-fat diet-induced insulin resistance in mice

“…This is in line with other studies showing that short-term HFD induces inflammatory response signals [6,30,31]. As chronic HFD is associated with increased oxidative stress from excessive mitochondrial ROS emissions in muscle [18,32], we sought to evaluate the induction of oxidative stress from mitochondrial ROS emissions in WAT after 1 week on an HFD. Unlike JNK phosphorylation, increased lipid-supported mitochondrial H 2 O 2 emission was associated with the development of insulin resistance in both WAT depots studied, suggesting mitochondrial ROS may contribute directly to the establishment of insulin resistance within WAT.…”

Mitochondrial Metabolism and Insulin Action

“…Studies from a number of different groups have shown that in genetic or diet-induced obese rodents, there is increase ROS production [4,5,174,175]. Importantly, most [4,5,175,176], but not all studies [177] show that insulin action is improved by genetic or pharmacological attenuatation of mitochondrial ROS production, indicating an especially important role for generation of reactive species in this organelle. Since mitochondria are particularly susceptible to oxidative attack [178,179], it is possible that overactive ROS generation in response to obesity or high dietary lipid supply, may lead to defects in mitochondrial function.…”