Insulin access to skeletal muscle is preserved in obesity induced by polyunsaturated diet

OBJECTIVE: Diets high in saturated fat induce obesity and insulin resistance, and impair insulin access to skeletal muscle, leading to reduced insulin levels at the muscle cell surface available to bind insulin receptors and induce glucose uptake. In contrast, diets supplemented with polyunsaturated fat improve insulin sensitivity and reduce the risk for type 2 diabetes. We hypothesized that a polyunsaturated high fat diet would preserve insulin sensitivity and insulin access to muscle as compared to a saturated high fat diet. METHODS: After 12 weeks of control, saturated (LARD) or polyunsaturated (salmon oil; SO) high fat diet, we measured muscle insulin sensitivity and insulin access to skeletal muscle using lymph, a surrogate of skeletal muscle interstitial fluid. RESULTS: Fat diets induced similar weight gain, yet only LARD impaired insulin sensitivity. Hyperinsulinemia in the LARD group did not induce an increase in basal interstitial insulin, suggesting reduced insulin access to muscle after LARD, but not SO. CONCLUSIONS: A diet high in polyunsaturated fat does not impair insulin access to muscle interstitium or induce insulin resistance as observed with a saturated fat diet, despite similar weight gain. Future studies should determine whether dietary SO supplementation improves impairments in insulin access to skeletal muscle.