Effect of a Grape Seed Extract (GSE) on Insulin Resistance

In people with the metabolic syndrome, the investigators hypothesize that administration of a single 300 mg dose of a grape seed extract (GSE) will reduce insulin resistance (how well cells in the body can take up and use glucose), oxidative stress, and the amount of oxidized LDL in the blood during a 24 hour period. Each of these can be elevated after eating high fat meals, which are commonly found in the average Western diet. To better assess the impact of these high fat eating patterns, three standardized high fat meals will be served during the study day: breakfast, lunch, and dinner. Measurements in the blood will be assessed at hourly intervals during the 24 hour study day protocol. Additionally, the investigators hypothesize that daily administration of 300 mg of GSE for 30 days will decrease baseline insulin resistance, oxidative stress, and the level of oxidized LDL in the blood when this 24 hour study day protocol is repeated and breakfast, lunch, and dinner are again served.

Insulin resistance will be measured using a comparison of insulin and glucose levels in the blood. Oxidative stress, a measure of inflammation, will be measured by cytokines levels in the blood. The level of oxidized LDL will be measured in the blood. The investigators also plan to undertake a subsidiary pharmacokinetic study on the various polymers which are known to be present in grape seed extracts to determine their bio-availability and their relationship to the biological effects observed.

Inclusion criteria

• Metabolic Syndrome, based on subject meeting at least 3 of the following criteria:
• Abdominal obesity with waist circumference > 40 inches in men or > 35 inches in women,
• Pre-hypertension with blood pressure > 135/85,
• Fasting blood glucose levels above 110 mg/dl,
• Plasma triglyceride levels in excess of 150 mg/dl,
• HDL levels below 40 mg/dl in men or 50 mg/dl in women.

Exclusion criteria

• Any known systemic disease,
• Diabetes,
• Alcohol consumption > 1-2 drinks/week,
• Taking any medications or supplements that will affect metabolism, their ability to exercise or oxidative status,
• Smokers,
• Female subjects having abnormal menstrual cycles, taking oral contraceptives, pregnant or lactating.