Researchers from the University of Montpellier 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 affect 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, whil 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 (Provinolse, Societe Francaise de Distillerie).
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. In 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,” report the researchers.
“The PPE 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.”
Diabetes affects an estimated 24 million Americans, equal to 8 percent of the population. The total costs are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.
Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi:10.1017/S0007114511000602
“A grape polyphenol extract modulates muscle membrane fatty acid composition and lipid metabolism in high-fat–high-sucrose diet-fed rats”
Authors: M. Aoun, F. Michel, G. Fouret, A. Schlernitzauer, V. Ollendorff, C. Wrutniak-Cabello, J-P. Cristol, M-A. Carbonneau, C. Coudray, C. Feillet-Coudray