April 2009

Antioxidant-rich supplements containing polyphenols from grape seed may protect against oxidative stress linked to obesity, suggests a new study with hamsters.

Researchers from the University of Montpellier report that animals fed a high-fat diet but supplemented with the grape seed extract had adiponectin levels 61% higher than animals only fed the high-fat diet. Adiponectin is a protein hormone linked to various metabolic processes and levels are inversely related to body fat levels.

"This is the first time that chronic consumption of grape phenolics is shown to reduce obesity development and related metabolic pathways including adipokine secretion and oxidative stress," wrote the researchers, led by Jean-Max Rouanet, in the journal Molecular Nutrition and Food Research.

Dr. Rouanet and his co-workers divided hamsters into three groups: One group received a standard diet, one group was fed a high-fat diet and the third received the high-fat diet and the grape seed extract.

After 12 weeks, the researchers found that animals on the high-fat diet only had increased abdominal fat, compared to the hamsters on the standard diet. On the other hand, the hamsters in the grape seed extract group did not have increased abdominal fat, they said.

Furthermore, increases in blood sugar, triglycerides, insulin and insulin resistance were observed in the high-fat diet only group, but supplementation with the grape seed extract was found to prevent "in part these effects," wrote the researchers.

Indeed, insulinemia and leptinemia were decreased by 16.5% and 45%, respectively. The researchers also noted lowered glycemia and insulin resistance values. Measure of oxidative stress, attained using measures of cardiac production of superoxide anion and NAD(P)H oxidase expression, were reduced by 74% and 30%, respectively.

"These results suggest that grape seed extract acted by mechanisms operating—at least in part—inside an antioxidant effect and the possibility that adiponectin might modulate oxidative stress, leading to anti-obesity effects," wrote the researchers.

"Thus, we provided insights into one mechanism, increased oxidant stress, that probably contributes to the pathological after-effects of obesity and that may have important public health implications, being a target for interventions to decrease the pathology," they added.

Molecular Nutrition and Food Research Published online ahead of print.