Enhanced skeletal muscle lipid oxidative efficiency in insulin-resistant vs insulin-sensitive nondiabetic, nonobese humans

Abstract

Context: Skeletal muscle insulin resistance is proposed to result from impaired skeletal muscle lipid oxidative capacity. However, there is no evidence indicating that muscle lipid oxidative capacity is impaired in healthy otherwise insulin-resistant individuals. Objective: The objective of the study was to assess muscle lipid oxidative capacity in young, nonobese, glucose-tolerant, insulin-resistant vs insulin-sensitive individuals. Design and Volunteers: In 13 insulin-sensitive [by Matsuda index (MI) (22.6 ± 0.6 [SE] kg/m2); 23 ± 1 years; MI 5.9 ± 0.1] and 13 insulin-resistant (23.2 ± 0.6 kg/m2;23 ± 3 years; MI 2.2 ± 0.1) volunteers, skeletal muscle biopsy, blood extraction before and after an oral glucose load, and dual-energy x-ray absorptiometry were performed. Main Outcome Measures: Skeletal muscle mitochondrial to nuclear DNA ratio, oxidative phosphorylation protein content, and citrate synthase and β-hydroxyacyl-CoA dehydrogenase activities were assessed. Muscle lipids and palm