Exercise and weight loss are cornerstones in the treatment and prevention of type 2 diabetes, and both interventions function to increase insulin sensitivity and increase glucose uptake into skeletal muscle. Studies in rodents demonstrate that glucose uptake in muscle involves site-specific phosphorylation of the Rab-GTPase-activating-proteins AS160(TBC1D4) and TBC1D1. Multiple kinases, including Akt and AMPK, phosphorylate TBC1D1 and AS160 on distinct residues, regulating their activity and allowing for GLUT4-translocation. In contrast to extensive rodent-based studies, the regulation of AS160 and TBC1D1 in humans is not well understood. In this study, we determined the effects of dietary intervention and an exercise bout on TBC1D1 and AS160 site-specific phosphorylation. Ten obese subjects were studied at baseline and after a two-week dietary intervention. Muscle biopsies were obtained at rest and following a 30min exercise bout(70%VO2max). Muscles were analyzed for AMPK-activity and Akt-phosphorylation, and for TBC1D1 and AS160-phosphorylation on known or putative AMPK and Akt sites:AS160-Ser711(AMPK),TBC1D1-Ser231(AMPK),TBC1D1-Ser660(AMPK),TBC1D1-Ser700(AMPK), and TBC1D1-Thr590(Akt). The diet intervention, that consisted of a major shift in the macronutrient composition of the diet resulted in a 4.2±0.4kg weight-loss(P<0.001) and a significant increase in insulin sensitivity, but surprisingly, there was no effect on expression or phosphorylation of the muscle signaling proteins. Exercise increased AMPKα2-activity, but did not increase Akt phosphorylation. Exercise increased phosphorylation on AS160-Ser711, TBC1D1-Ser231, and TBC1D1-Ser660 but not TBC1D1-Ser700. Exercise did not increase TBC1D1-Thr590-phosphorylation or TBC1D1/AS160-PAS-phosphorylation, consistent with the lack of Akt-activation. These data demonstrate that a single bout of exercise regulates TBC1D1 and AS160 phosphorylation on multiple sites in human skeletal muscle.
- Skeletal muscle
- Glucose transport
- Copyright © 2011, American Journal of Physiology - Endocrinology and Metabolism