Syrah Grape Polyphenol Extracts Protect Human Skeletal Muscle Cells from Oxidative and Metabolic Stress Induced by Excess of Palmitic Acid: Effect of Skin/Seed Ripening Stage.

Metabolic skeletal muscle (SM) dysfunction, triggered by increased oxidative stress and mitochondrial impairment, is a pivotal contributor to obesity-associated insulin resistance (IR). Addressing obesity and SM IR demands substantial lifestyle changes including regular exercise and dietary adjustments that are difficult to follow over time. This prompted exploration of alternative approaches. Grape polyphenols (GPPs) have demonstrated a positive impact on metabolism, although few studies have focused on SM. Since grape polyphenolic content and composition depend on tissue and ripening, we explored the antioxidant potential of GPPs from skin (Sk) and seeds (Sd) extracted before veraison (Bv) and at mature (M) stages, on palmitate-induced IR in primary human SM cells. Despite their important difference in polyphenol (PP) content: Sd-BvPP > Sd-MPP/Sk-BvPP > Sk-MPP, all extracts reduced lipid peroxidation by 44-60%, up-regulated the heme-oxygenase 1 protein level by 75-132% and mitochondrial activity by 47-68%. Contrary to the other extracts, which improved insulin response by 50%, Sd-BvPP did not. Our findings suggest that compounds other than stilbenoids or anthocyanin-type molecules, present only in grape Sk, could play an active role in regulating SM oxidative and metabolic stress and insulin sensitivity, paving the way for further exploration of novel bioactive compounds.

Grape Polyphenols in the Treatment of Human Skeletal Muscle Damage Due to Inflammation and Oxidative Stress during Obesity and Aging: Early Outcomes and Promises.

Today, inactivity and high-calorie diets contribute to the development of obesity and premature aging. In addition, the population of elderly people is growing due to improvements in healthcare management. Obesity and aging are together key risk factors for non-communicable diseases associated with several co-morbidities and increased mortality, with a major impact on skeletal muscle defect and/or poor muscle mass quality. Skeletal muscles contribute to multiple body functions and play a vital role throughout the day, in all our activities. In our society, limiting skeletal muscle deterioration, frailty and dependence is not only a major public health challenge but also a major socio-economic issue. Specific diet supplementation with natural chemical compounds such as grape polyphenols had shown to play a relevant and direct role in regulating metabolic and molecular pathways involved in the prevention and treatment of obesity and aging and their related muscle comorbidities in cell culture and animal studies. However, clinical studies aiming to restore skeletal muscle mass and function with nutritional grape polyphenols supplementation are still very scarce. There is an urgent need for clinical studies to validate the very encouraging results observed in animal models.