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

Abstract

Abnormalities in endothelial function may be associated with increased cardiovascular risk in diabetic patients. We examined the effect of an oleic‐acid‐rich diet on insulin resistance and endothelium‐dependent vasoreactivity in type 2 diabetes. Eleven type 2 diabetic patients were changed from their usual linoleic‐acid‐rich diet and treated for 2 months with an oleic‐acid‐rich diet. Insulin‐mediated glucose transport was measured in isolated adipocytes. Fatty acid composition of the adipocyte membranes was determined by gas‐liquid chromatography and flow‐mediated endothelium‐dependent and ‐independent 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<0.0001). Diabetic control was not different between the diets, but there was a small 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/10⁵ cells/3 min, p<0.0001). Endothelium‐dependent flow‐mediated vasodilatation (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 glucose transport (p<0.001) but no relationship between insulin‐stimulated glucose transport and change in endothelium‐dependent FMD. There was a significant positive correlation between adipocyte membrane oleic/linoleic acid and endothelium‐dependent FMD (r=0.61, p<0.001). Change from polyunsaturated to monounsaturated diet in type 2 diabetes reduced insulin resistance and restored endothelium‐dependent vasodilatation, suggesting an explanation for the anti‐atherogenic benefits of a Mediterranean‐type diet.