Impaired enhancement of insulin action in cultured skeletal muscle cells from insulin resistant type 2 diabetic patients in response to contraction using electrical pulse stimulation

Abstract

Aims: Skeletal muscle insulin resistance is a characteristic feature of type 2 diabetes. The aim of this study was to examine the effect of contraction on insulin action using electrical pulse stimulation (EPS) in cultured skeletal muscle cells from insulin resistant type 2 diabetic patients.

Methods: Skeletal muscle cell cultures were established from 6 insulin resistant type 2 diabetic subjects and age and BMI matched non-diabetic control subjects. Day 7 differentiated myotubes were treated with or without EPS for 16 h, after which glucose uptake and AS160 phosphorylation were measured in the presence or absence of insulin.

Results: In control myotubes, EPS resulted in increased phosphorylation of AMPKThr¹⁷² (vs no EPS; p < 0.01), and this was associated with increased glucose uptake (p < 0.05). Insulin in the absence of EPS increased glucose uptake and AS160Thr⁶⁴² phosphorylation, and both effects were significantly enhanced by prior EPS. In the absence of EPS, AMPK activation was significantly increased (p < 0.01) in the diabetic vs control myotubes. Despite a comparable degree of AMPK activation following EPS, the action of insulin on glucose uptake (p < 0.05) and AS160Thr⁶⁴² phosphorylation (p < 0.001) was decreased in the diabetic vs control myotubes.

Conclusion: EPS mediated AMPK activation enhances the effect of insulin on glucose uptake and AS160Thr⁶⁴² phosphorylation in control myotubes replicating key metabolic benefits of exercise on insulin action in man. Conversely, insulin mediated glucose uptake and AS160Thr⁶⁴² phosphorylation remain significantly decreased in diabetic vs control myotubes despite a comparable degree of AMPK activation following EPS.

Keywords: AMPK; AS160; Exercise; Insulin sensitization; Myotube; Skeletal muscle.