Dietary ω3 fatty acid alters prostaglandin synthesis, glucose transport and protein turnover in skeletal muscle of healthy and diabetic rats

Abstract

The present study was designed to determine if dietary-fat-induced alterations in the fatty acid composition of skeletal-muscle lipid alters insulin-dependent and basal muscle metabolism, including glucose and amino acid transport, prostaglandin (PG) synthesis and protein turnover. Rats were fed on high-fat semi-purified diets providing 19% or 1% ω3 fatty acids in the form of fish oil, for 6 weeks. After 3 weeks, half of the rats were made diabetic by a single injection of streptozotocin (50 mg/kg body wt.) After a further 3 weeks, contralateral epitrochlearis and extensor digitorum longus (EDL) muscles from each rat were incubated in vitro. High levels of dietary ω3 fatty acids decreased PGE2 and PGF(2α) synthesis in EDL and epitrochlearis muscle (P < 0.0001). Diabetes and insulin had no effect on PG synthesis. Diet did not alter basal glucose or amino acid transport in EDL muscle from healthy or diabetic rats. Insulin increased glucose and amino acid transport (P < 0.0001); the increase in glucose transport by insulin was significantly greater in muscles of rats fed on high levels of ω3 fatty acids (P < 0.05). Epitrochlearis from rats fed on high levels of ω3 fatty acids showed decreased net protein degradation in the presence and absence of insulin, owing to decreased rates of protein degradation and synthesis. The data suggest that high levels of dietary ω3 fatty acids that alter muscle membrane composition also result in alterations in glucose transport and the metabolism of muscle protein.