Anti-Diabetic Potential of Grape Polyphenols Studied
Lee Swanson Research Update
Researchers from the University of Montpelier in the south of France report that rats fed a high-fat and high-sugar diet but supplemented with grape polyphenols displayed a lower accumulation of fat in muscle tissues.
Diets high in saturated fats are reported to worsen insulin resistance, whereby cells do not respond adequately to the normal levels of insulin produced by the body—a marker of the onset of diabetes, explained the researchers in the British Journal of Nutrition.
The effect of fat on insulin sensitivity is said to occur via changes to the compositions of cell membranes, and particularly the phospholipids in the membrane. The new study sought to identify if consumption of a polyphenol-rich extract from grapes could change the composition of fat in muscle cell membranes, with a particular focus on phospholipids and triglycerides.
Lab rats were divided into three groups: The first group was fed a standard lab rat diet, while the other two groups received a diet containing high levels of fat and sugar. One of the high-fat, high-sugar groups received an additional extract of grape polyphenols.
Results showed that animals receiving the grape extract had lower triglyceride levels in the cell membranes of their muscles, compared to the high-fat, high-sugar-fed animals. An addition, levels of omega-3 polyunsaturated fatty acids in the phospholipid portion of the membranes were found to increase in the grape-fed animals.
The high-fat, high-sugar diet was found to alter gene expression in muscle cells, but these changes were reversed in the animals given the grape extract, said the researchers.
"In conclusion, the grape polyphenol extract modulated membrane phospholipid fatty acid composition and decreased muscle triglyceride content in high-fat, high-sugar-diet-fed rats," the researchers reported.
"The PPE (polyphenol extract) lowered…gene and protein expression, probably decreasing fatty acid transport and lipid accumulation within skeletal muscle," they added. "These effects of the PPE are in favor of a better insulin sensibility."
British Journal of Nutrition; Published online ahead of print.
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May, 2011