Cell cholesterol levels determine glucose uptake and insulin resistance in skeletal muscle

Abstract

In skeletal muscle, cholesterol is enriched in the transverse tubule membranes (TT), where insulin‐promoted GLUT4 translocation occurs. To test the role of TT cholesterol content, we fed mice a high fat diet (HFD) and measured insulin triggered glucose uptake. Cholesterol levels were measured in TT‐enriched triad fractions isolated from skeletal muscle of male C57BL/6J mice fed either a normal or a HFD (60% fat) for 8 weeks. Isolated muscle fibers from flexor digitorum brevis were used for fluorescence glucose uptake determinations. Akt activity in myotubes was determined by Western blot analysis. Relative to controls, body weight, body fat content and metabolic variables including insulin resistance were higher in HFD fed mice. Cholesterol levels in triads from HFD‐fed mice were 30% higher than in controls. Preincubation of myotubes with Methyl‐β‐cyclodextrin to remove cholesterol partially inhibited Akt phosphorylation in controls, and increased both basal and insulin‐induced glucose uptake in muscle fibers from controls or HFD‐fed mice. Cholesterol removal restored insulin sensitivity in HFD‐fed mice, independently of Akt and CaMKII inhibition. Our findings indicate that cholesterol removal from muscle fibers may be a strategy for improving insulin resistance in HFD‐fed mice and suggest that TT cholesterol has a physiological role in glucose transport.FONDECYT 3110105, FONDAP 15010006.