Superoxide Production by Rat Skeletal Muscle Mitochondria: Influence of High Fat Diet

Abstract

Chronic positive energy and fat balances increase the risk for the development of skeletal muscle insulin resistance. Reactive oxygen species may be a consequence and/or a contributing factor to this pathology. The purpose of this study was to evaluate superoxide (O2.) production by mitochondria (MITO) isolated from gastrocnemius muscle of rats fed standard chow (C) or a high fat (HF) diet. MITO were respired under either a static condition (oligomycin, OLIGO) or at an experimentally established ATP free energy corresponding to about 50% of maximal respiration (flow condition). Respiratory substrates were provided at saturating concentrations and O2. production was followed. Under the OLIGO condition MITO oxidizing pyruvate + malate (P+M) generated very low rates of O2. production irrespective of diet. In contrast, P+M supplemented with the cytosolic-mitochondrial electron shuttle substrates glycerol-3-phosphate and glutamate elicited O2. generation rates severalfold greater than P+M alone. Moreover, MITO from HF animals produced much higher O2. production than C rats when these products of the glycolytic pathway were available as respiratory fuels. For both C and HF MITO, the flow condition drastically reduced O2. production for all fuels and combinations. These findings suggest that excessive fuel and carbohydrate availability under sedentary conditions may promote the generation of reactive oxygen species. Supported by NSF IBN-0116997