Effect of grape seed extract on postprandial oxidative status and metabolic responses in men and women with the metabolic syndrome - randomized, cross-over, placebo-controlled study

Abstract

Objective: This investigation was undertaken to determine whether a grape seed extract (GSE) that is rich in mono-, oligo- and poly- meric polyphenols would modify postprandial oxidative stress and inflammation in individuals with the metabolic syndrome (MetS).

Background: MetS is known to be associated with impaired glucose tolerance and poor glycemic control. Consumption of a meal high in readily available carbohydrates and fat causes postprandial increases in glycemia and lipidemia and markers of oxidative stress, inflammation and insulin resistance.

Materials/methods: After an overnight fast, twelve subjects with MetS (5 men and 7 women) consumed a breakfast meal high in fat and carbohydrate in a cross-over design. A GSE (300 mg) or placebo capsule was administrated 1 hr before the meal (-1 hr). Changes in plasma insulin, glucose, oxidative stress and inflammatory markers were measured hourly for 6 hr.

Results: Plasma hydrophilic oxygen radical absorbance capacity (ORAC) measured as the positive incremental area under the curve (-1 to 5 hr) was significantly increased when the meal was preceded by GSE compared with placebo (P<0.05). Meal-induced increases in oxidized LDL were attenuated with GSE (P<0.05). Plasma glucose concentrations (area under the curve from -1 to 5 hr) were also significantly lower when the meal was preceded by GSE (P<0.05) while the insulin concentrations remained unchanged (P>0.05). No changes in inflammatory markers were evident.

Conclusion: These data suggest that GSE enhances postprandial plasma antioxidant status and reduces the glycemic response to a meal, high in fat and carbohydrate in subjects with the MetS.

Key words: Polyphenols, Oxidative stress, Inflammation, ORAC, Oxidized LDL