Electrical stimulation improves insulin responses in a human skeletal muscle cell model of hyperglycemia

Myoblasts from human skeletal muscle were isolated from needle biopsy samples of the vastus lateralis of young and healthy volunteers. Contaminating fibroblasts were removed, and myoblasts were fused into differentiated multinucleated myotubes. These myotubes manifested both basal and insulin-stimulated (1-100 nM) glucose transport and glycogen synthesis. Insulin increased 2-deoxyglucose uptake by 1.4-fold and glycogen synthesis by 2.1-fold. Measurements of impedance of cell-covered gold electrodes (ECIS system) showed increased micromotion of caffeine-stimulated cells, showing their ability to contract. Acute electrical stimulation of the myotubes increased 2-deoxyglucose uptake by about 30%. Treatment with high glucose concentrations (10-20 mM) for 2-8 days reduced both basal and insulin-stimulated glucose uptake. Maximal effect was seen after 2 days of treatment with 20 mM glucose. Baseline glucose uptake and glycogen synthesis were reduced by 35%, insulin-stimulated glucose uptake by 25%, and insulin-stimulated glycogen synthesis by 39%. Total cell content of glycogen was not changed by hyperglycemia. The insulin-stimulated glucose uptake in hyperglycemia-treated cells was improved by electrical stimulation of the cells. In conclusion, a model of hyperglycemia has been established, and electrical stimulation improved insulin responses.