Modified fluidity and lipid composition in lipoproteins and platelet membranes from diabetic patients

The interaction between lipoproteins and the platelet membrane has been proved to cause a modification in cellular functions. We studied 12 men with insulin-dependent diabetes mellitus (IDDM), 14 men with noninsulin-dependent diabetes mellitus (NIDDM), and 26 age-matched healthy men on the same diet. We determined fluidity by measuring the fluorescence polarization (P) of the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) both in platelet membranes and in lipoproteins isolated by ultracentrifugation in NaBr density gradient. The lipid composition of lipoproteins and of platelet membranes was determined by enzymatic methods. The fluidity of platelet membranes was significantly increased both in patients affected by NIDDM and in subjects with IDDM compared with normal subjects. Low-density lipoproteins (LDL) showed an increased fluidity only in NIDDM patients. A percent increase in the triglyceride content was observed in all lipoprotein fractions in diabetic subjects. Increased phospholipid content was found in the platelet membranes from IDDM and NIDDM patients. The change in LDL fluidity observed in NIDDM patients might determine altered interactions between the lipoprotein and cellular receptors. The role of lipoproteins in the modulation of the platelet membrane properties in diabetes mellitus deserves further studies.