Diabetes and the Mediterranean diet: a beneficial effect of oleic acid on insulin sensitivity, adipocyte glucose transport and endothelium-dependent vasoreactivity

Abnormalities in endothelial function may be associated with increased card iovascular risk in diabetic patients. We examined the effect of an oleic-ac id-rich diet on insulin resistance and endothelium-dependent vasoreactivity in type 2 diabetes. Eleven type 2 diabetic patients were changed from thei r usual linoleic-acid-rich diet and treated for 2 months with an oleic-acid -rich diet. Insulin-mediated glucose transport was measured in isolated adi pocytes. Fatty acid composition of the adipocyte membranes was determined b y gas-liquid chromatography and flow-mediated endothelium-dependent and -in dependent vasodilatation were measured in the superficial femoral artery at the end of each dietary period. There was a significant increase in oleic acid and a decrease in linoleic acid on the oleic-acid-rich diet (p < 0.000 1). Diabetic control was not different between the diets, but there was a s mall but significant decrease in fasting glucose/insulin on the oleic-acid- rich diet. Insulin-stimulated (1 ng/ml) glucose transport was significantly greater on the oleic-acid-rich diet (0.56 +/- 0.17 vs. 0.29 +/- 0.14 nmol/ 10(5) cells/3min, p < 0.0001). Endothelium-dependent flow-mediated vasodila tation (FMD) was significantly greater on the oleic-acid-rich diet (3.90 +/ - 0.97% vs. 6.12 +/- 1.36% p < 0.0001). There was a significant correlation between adipocyte membrane oleic/linoleic acid and insulin-mediated glucos e transport (p < 0.001) but no relationship between insulin-stimulated gluc ose transport and change in endothelium-dependent FMD. There was a signific ant positive correlation between adipocyte membrane oleic/linoleic acid and endothelium-dependent FMD (r = 0.61, p < 0.001). Change from polyunsaturat ed to monounsaturated diet in type 2 diabetes reduced insulin resistance an d restored endothelium-dependent vasodilatation, suggesting an explanation for the anti-atherogenic benefits of a Mediterranean-type diet.