RELATIONSHIPS BETWEEN SERUM-LIPIDS, PLATELET MEMBRANE FATTY-ACID COMPOSITION AND PLATELET-AGGREGATION IN TYPE-2 DIABETES-MELLITUS

In order to gain further insight into the mechanism of platelet dysfun ction frequently reported in diabetes we investigated circulating fatt y acids, lipid composition of platelet membrane and platelet function in Type 2 diabetic patients. In these subjects, percentages of C16 : I n-7 and C18 : 1n-9 in serum phospholipid fraction and of C16 : In-7 in serum cholesterol eater fraction were decreased. Moreover, the conten t of C20 : 4n-6 in serum cholesterol esters was increased. Fatty acid composition of platelet membranes was altered in Type 2 diabetic subje cts : C18 : 0 and C20 : 3n-6 were increased but C20 : 4n-6 content was similar to controls. Aggregation in vitro did not differ from control s but aggregation in vivo was increased in Type 2 diabetic subjects. N o correlation was observed between metabolic parameters -i.e., HbA1, b lood glucose, serum triglycerides and total cholesterol, circulating f atty acids and fatty acid content of platelet membrane. A negative lin ear correlation was found between aggregation in vivo and C20 : 4n-6 c ontent of platelet membrane. Moreover, a U shaped relationship was obs erved between platelet aggregation in vitro and C20 : 4n-6 content of platelet membrane suggesting that C20 : 4n-6 level should be tightly c ontrolled otherwise platelet hyperreactivity may occur. These results indicate that despite a normal mean C20 : 4n-6 content in the platelet membrane, regulation of C20 : 4n-6 metabolism is less strictly contro lled in Type 2 diabetes mellitus and confirm the importance of arachid onic acid platelet content in the regulation of platelet aggregability .