Fish oil feeding improves muscle glucose uptake in tumor necrosis factor-treated rats

This study was conducted to characterize the effects of fish oil and sunflower oil on hepatic glucose production and peripheral glucose utilization during infusion of saline or tumor necrosis factor (TNF), using the euglycemic-hyperinsulinemic clamp technique combined with a primed-constant tracer infusion of high-performance liquid chromatography-purified 3H-3-glucose for estimation of whole-body glucose appearance and utilization rates. Insulin 10 mU/kg.min was infused to reach a plasma insulin level of 200 microU/mL. 14C-1-deoxyglucose (14C-DG) uptake was also measured in specific tissues following intravenous bolus administration. The results showed that during a hyperinsulinemic-euglycemic clamp, infusion of TNF 20 micrograms/kg for 3 hours resulted in a significant reduction of glucose infusion and a significant increase of hepatic glucose production in both dietary groups as compared with saline infusion, indicating a state of insulin resistance induced by TNF. The results also showed that TNF infusion significantly decreased the rate of 14C-DG uptake in muscle in the sunflower oil group but not in the fish oil group, suggesting that fish oil is able to restore to normal the glucose utilization impaired by TNF. These observations suggest that in hyperinsulinemic and euglycemic conditions, prefeeding with fish oil significantly improves glucose uptake in muscle tissue, but does not alter the increase in hepatic glucose production during TNF infusion.