Effect of resveratrol on insulin action in primary myotubes from lean individuals and individuals with severe obesity

Abstract

Resveratrol, a natural polyphenol compound contained in numerous plants, has been proposed as a treatment for obesity-related disease processes such as insulin resistance. However, in humans there are conflicting results concerning the efficacy of resveratrol in improving insulin action; the purpose of the present study was to determine whether obesity status (lean, severely obese) affects the response to resveratrol in human skeletal muscle. Primary skeletal muscle cells were derived from biopsies obtained from age-matched lean and insulin-resistant women with severe obesity and incubated with resveratrol (1 µM) for 24 h. Insulin-stimulated glucose oxidation and incorporation into glycogen, insulin signal transduction, and energy-sensitive protein targets [AMP-activated protein kinase (AMPK), Sirt1, and PGC1α] were analyzed. Insulin-stimulated glycogen synthesis, glucose oxidation, and AMPK phosphorylation increased with resveratrol incubation compared with the nonresveratrol conditions (main treatment effect for resveratrol). Resveratrol further increased IRS1, Akt, and TBC1D4 insulin-stimulated phosphorylation and SIRT1 content in myotubes from lean women, but not in women with severe obesity. Resveratrol improves insulin action in primary human skeletal myotubes derived from lean women and women with severe obesity. In women with obesity, these improvements may be associated with enhanced AMPK phosphorylation with resveratrol treatment.NEW & NOTEWORTHY A physiologically relevant dose of resveratrol increases insulin-stimulated glucose oxidation and glycogen synthesis in myotubes from individuals with severe obesity. Furthermore, resveratrol improved insulin signal transduction in myotubes from lean individuals but not from individuals with obesity. Activation of AMPK plays a role in resveratrol-induced improvements in glucose metabolism in individuals with severe obesity.

Keywords: glucose metabolism; human skeletal muscle; insulin signaling; obesity; resveratrol.

Graphical abstract

Figure 1.

Insulin action in the absence or presence of 100 nM insulin in myotubes from lean and individuals with severe obesity in response to 24 h of resveratrol treatment (Resv). A: absolute rates of glycogen synthesis. B: fold change in glycogen synthesis over noninsulin, non-Resv condition. C: absolute rates of glucose oxidation. D: fold change in glucose oxidation over noninsulin, non-Resv condition. Following detecting significance for either group, treatment and/or interaction effect using three-way ANOVA, distinguishing meaningful differences were performed using a two-tailed Student’s t test. There were main effects (P < 0.05) for insulin and resveratrol for both glycogen synthesis and glucose oxidation. There was a group effect (P < 0.05) for insulin-stimulated glycogen synthesis and glucose oxidation. This indicates that resveratrol treatment enhances insulin action in severely obese subjects; however, that did not mitigate the difference between groups. Data are presented as means ± SE. n = 8 per group (all females); *P < 0.05 for selected comparison; #P < 0.05 for resveratrol. CTR, control.

Figure 2.

Insulin signal transduction in the absence or presence of 100 nM insulin in myotubes from lean and subjects with severe obesity in response to 24 h of resveratrol treatment (Resv). A: IRS1 (Tyr632) phosphorylation. B: Akt (Ser473) phosphorylation. C: Akt (Thr308) phosphorylation. Following detecting significance for either group, treatment and/or interaction effect using three-way ANOVA, distinguishing meaningful differences were performed using a two-tailed Student’s t test. There were main effects (P < 0.05) for insulin and resveratrol for all the proteins and for subject group for pIRS1 and pAkt (Ser473). There were interaction effects (P < 0.05) for subject group with resveratrol for pIRS1 and pAkt (Ser473) and for subject group with insulin for pIRS1. Data are presented as means ± SE. n = 8 per group (all females); *P < 0.05 for selected comparison. CTR, control.

Figure 3.

Signatures on TBC1D4 phosphorylation in the absence or presence of 100 nM insulin in myotubes from lean and subjects with severe obesity in response to 24 h of resveratrol treatment (Resv). A: Thr642 phosphorylation. B: Ser704 phosphorylation. C: Ser341 phosphorylation. D: Ser588 phosphorylation. E: Ser318 phosphorylation. Following detecting significance for either group, treatment, and/or interaction effect using three-way ANOVA, distinguishing meaningful differences were performed using a two-tailed Student’s t test. There were main effects (P < 0.05) for insulin for all measured sites of pTBC1D4s and for resveratrol for pThr642. There was a group effect with resveratrol for pThr642 and pSer704. Data are presented as means ± SE. n = 8/group (all females); *P < 0.05 for selected comparison. CTR, control.

Figure 4.

AMPK(Thr172) phosphorylation, SIRT1, PGC1α, citrate synthase protein content in myotubes from lean and severely obese subjects in response to 24 h of resveratrol treatment (Resv). A: AMPK (Thr172) phosphorylation. B–D: SIRT1, PGC1α, and citrate synthase protein content. Following detecting significance for either group, treatment, and/or interaction effect using three-way ANOVA, distinguishing meaningful differences were performed using a two-tailed Student’s t test. There were main effects (P < 0.05) for resveratrol for pAMPK(Thr172) for both groups. There was a significant interaction effect (P < 0.05) for subject group with resveratrol for SIRT1. Data are presented as means ± SE. n = 8 per group (all females); *P < 0.05 for selected comparison. CTR, control.