Valorization of Winemaking By-Products: White and Red Grape Seed Oils Improve Glucose Consumption and Uptake In Vitro

Abstract

: The rising demand for alternative solutions to diabetes mellitus has prompted significant interest in the exploration of plant-derived anti-diabetic compounds, especially within a circular economy framework that seeks sustainable and profitable reuse options. In this context, red (RSGO) and white (WGSO) grape seed oils, by-products of Sicilian vineyards, were prepared, analyzed for their fatty acid, polyphenol, carotenoid, and chlorophyll content, and evaluated for their glucose-lowering ability on HepG2 cells. Utilizing cytochemical techniques, flow cytometry, and protein blotting, we explored the effects of non-toxic oil dilutions on (i) glycogen storage, (ii) glucose consumption/uptake, (iii) GLUT-2, GLUT-4, and hepatocyte nuclear factor-1α (HNF1α) expression levels, and (iv) AMP-activated protein kinase (AMPK), insulin receptor substrate-1 (IRS-1), AKT, and PKCζ phosphorylation states, which are involved in insulin-mediated and -independent regulation of GLUT-4 membrane exposure. RGSO and WGSO, despite adopting slightly varying molecular strategies, were both proven to be effective stimulators of glucose absorption and glycogenesis. Specifically, RSGO promoted GLUT-2 and GLUT-4 up-regulation, whereas the WGSO-induced effect was associated with an increase in GLUT-4 levels alone. Moreover, the oils activated both pathways responsible for GLUT-4 translocation. Therefore, these wine-making residues have substantial potential as anti-diabetic solutions, holding promise for integration into the biomedical and food sectors.