Beneficial effects of a red wine polyphenol extract on high-fat diet-induced metabolic syndrome in rats

Individuals with metabolic syndrome (MS) show several metabolic abnormalities including insulin resistance, dyslipidaemia, and oxidative stress (OS). Diet is one of the factors influencing the development of MS, and current nutritional advice emphasises the benefits of fruit and vegetable consumption. Here, we assessed the effects of naturally occurring antioxidants, red wine polyphenols (RWPs), on MS and OS. Wistar rats (n = 20) weighing 200-220 g received a high-fat diet (HFD) for 2 months before they were divided into two groups that received either HFD only or HFD plus 50 mg/kg RWPs in their drinking water for an additional 2 months. A control group (n = 10) received a normal diet (ND) for 4 months. Rats receiving HFD increased body weight over 20 % throughout the duration of the study. They also showed increased blood levels of C-peptide, glucose, lipid peroxides, and oxidised proteins. In addition, the HFD increased OS in hepatic, pancreatic, and vascular tissues, as well as induced pancreatic islet cell hyperplasia and hepatic steatosis. Addition of RWPs to the HFD attenuated these effects on plasma and tissue OS and on islet cell hyperplasia. However, RWPs had no effect on blood glucose levels or hepatic steatosis. RWPs showed an antioxidant mechanism of action against MS. This result will inform future animal studies exploring the metabolic effects of RWPs in more detail. In addition, these findings support the use of antioxidants as adjunctive nutritional treatments for patients with diabetes.