Skeletal muscle integrin expression in non-obese men with varying degrees of insulin sensitivity

The remodeling of skeletal muscle extracellular matrix (ECM) components is related to the degree of insulin resistance (IR). Membrane receptors such as integrins provide two-way signaling ("inside-out" and "outside-in" signaling) between ECM components of skeletal muscle (e.g., collagen, laminin, fibronectin) and intracellular signaling pathways. The aim of the study was to analyze the relationship between the expression of integrins in skeletal muscle and insulin sensitivity (IS) in young, healthy, non-obese volunteers. We studied 36 healthy non-obese male participants. Subjects were divided into three subgroups on the basis of the hyperinsulinemic-euglycemic clamp: upper IS tertile, medium IS tertile, and lower IS tertile. Vastus lateralis muscle biopsies were performed before each clamp. Next, analysis of integrin mRNA expression was performed. Waist circumference, percent body fat, fasting serum insulin, total cholesterol, triglycerides and LDL-cholesterol were higher in the lower IS tertile subgroup compared to the other two subgroups (p < 0.05). The lower IS tertile showed increased expression of ITGA5, ITGA6, ITGA7, SPARC (p < 0.05) in comparison with the upper IS tertile and ITGA6 (p < 0.05) compared to the medium IS tertile. ITGA2, ITGA3, ITGA5, ITGA6, ITGA7, SPARC correlated inversely with IS (p < 0.05). Skeletal muscle integrin are associated with low IS in healthy nonobese men. Our data suggest that factors associated with ECM in muscle may be involved in modulation of insulin action even at the early stages of the development of IR.