Effect of Extra Virgin Olive Oil on Glycemic Control ,Insulin Resistance and Insulin Secretion in Patients With Type 2 Diabetes

Diabetes is a major health problem and one of the leading causes of morbidity and mortality worldwide. Lifestyle and particularly dietary habits are considered key issues in both the prevention and management of the disease aimed at achieving an adequate glycemic control or at delaying the onset of diabetic chronic complications .

Olive oil (OO) has been recognized for centuries for its nutritional properties and considered as the "elixir of youth and health" by antique Greeks. Extra virgin olive oil is the main source of dietary fat in the Mediterranean diet . Consumption of extra virgin olive oil might exert beneficial effects in the prevention, development and progression of T2D compared with refined olive oil .

Several bioactive ingredients within OO have been repeatedly linked with anti-oxidant and anti-inflammatory preventative functions, particularly those from monounsaturated fatty acids (MUFA), and key biophenols such as oleuropein and hydroxytyrosol (HT) . Biophenols may influence glucose metabolism via several mechanisms; inhibition of carbohydrate digestion and glucose absorption in the intestine, activation of insulin receptors and glucose uptake in the tissues, antioxidative properties, potent free-radical scavenging and immunomodulatory effects. Multiple studies proven that EVOO improve metabolic control by affection of adipokines .The inhibition of carbohydrate digestion and absorption takes place through an inhibition of some digestive enzymes, especially the carbohydrate-hydrolyzing enzymes α-amylase and α glucosidase. Inhibition of these enzymes retards carbohydrate digestion, thus causing a reduction in glucose absorption rate .With their antioxidative properties, polyphenols diminish the production of advanced glycosylated end products such as HbA1c, AGEs, which are readily formed and accumulated with sustained hyperglycemia, contribute to the development of diabetic complications. As a consequence, inhibition of AGE formation constitutes an attractive therapeutic/preventive target .

Studies both in healthy subjects and in persons with type 2 diabetes mellitus have demonstrated that levels of GLP-1are increased more by dietary MUFA than by dietary saturated fatty acids, and that the greater postprandial clearance of an oral overload of MUFA-rich fats is associated with a greater increase in postprandial incretins such as GLP-1 or gastric inhibitory polypeptide. MUFAs from olive oil, therefore, appear to significantly increase the insulin and GPL-1 secretion .