Negative regulation of glucose metabolism in human myotubes by supraphysiological doses of 17 beta-estradiol or testosterone

• Objective. Exposure of skeletal muscle to high levels of testosterone or estrogen induces insulin resistance, but evidence regarding the direct role of either sex hormone on metabolism is limited. Therefore, the aim of this study was to investigate the direct effect of acute sex hormone exposure on glucose metabolism in skeletal muscle. Materials/Methods. Differentiated human skeletal myotubes were exposed to either 17 beta-estradiol or testosterone and metabolic characteristics were assessed. Glucose incorporation into glycogen, glucose oxidation, palmitate oxidation, and phosphorylation of key signaling proteins were determined. Results. Treatment of myotubes with either 17 beta-estradiol or testosterone decreased glucose incorporation into glycogen. Exposure of myotubes to 17 beta-estradiol reduced glucose oxidation under basal and insulin-stimulated conditions. However, testosterone treatment enhanced basal palmitate oxidation and prevented insulin action on glucose and palmitate oxidation. Acute stimulation of myotubes with testosterone reduced phosphorylation of S6K1 and p38 MAPK. Exposure of myotubes to either 17 beta-estradiol or testosterone augmented phosphorylation GSK3 beta(ser9) and PKC delta(Thr505), two negative regulators of glycogen synthesis. Treatment of myotubes with a PKC specific inhibitor (GFX) restored the effect of either sex hormone on glycogen synthesis. PKC delta silencing restored glucose incorporation into glycogen to baseline in response to 17 beta-estradiol, but not testosterone treatment. Conclusion. An acute exposure to supraphysiological doses of either 17 beta-estradiol or testosterone regulates glucose metabolism, possibly via PKC signaling pathways. Furthermore, testosterone treatment elicits additional alterations in serine/threonine kinase signaling, including the ribosomal protein S6K1 and p38 MAPK.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinsk bioteknologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Medical Biotechnology (hsv//eng)

Nyckelord

Sex hormones

Glucose oxidation

Insulin signaling

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