LIPOPROTEIN COMPOSITIONAL ABNORMALITIES IN TYPE-1 (INSULIN-DEPENDENT)DIABETIC-PATIENTS

Patients with type 1 (insulin-dependent) diabetes mellitus in good met abolic control usually have normal plasma lipid levels yet they have a n increased incidence of vascular complications. Abnormalities in the distribution and composition of lipoprotein subfractions might in part be responsible for the macroangiopathy seen in type 1 diabetes mellit us. The plasma lipids, lipoproteins and apolipoproteins were studied i n 9 type 1 diabetic patients during conventional insulin therapy and i n 14 healthy controls. Plasma lipoproteins were analysed by ultracentr ifugation in a zonal rotor to evaluate their concentrations and flotat ion properties and for compositional analysis. In diabetic patients th e mean glycosylated haemoglobin (HbA1c) was 9.44 +/- 1.02% and the pla sma lipid concentrations were not significantly different from healthy controls. The very low density lipoprotein (VLDL) subclass cholestero l concentrations were no different in diabetic patients and control su bjects, but the VLDL cholesterol/triglyceride ratio was significantly lower in diabetic patients than in control subjects (0.43 +/- 0.05 vs 0.85 +/- 0.14; p < 0.05). The flotation rate of LDL2, the major compon ent of low density lipoprotein (LDL) was lower in the diabetic patient s compared with the control subjects. The cholesterol concentrations o f intermediate density lipoprotein and LDL3, the minor component of LD L, were significantly higher (0.17 +/- 0.03 and 0.83 +/- 0.14 mmol/l r espectively) in diabetic patients than in control subjects (0.05 +/- 0 .02 and 0.24 +/- 0.08 mmol/l). The flotation properties and cholestero l concentrations of the high density lipoprotein (HDL) subclass, and t he protein-lipid composition of LDL2, HDL2 and HDL3, were no different in diabetic patients and control subjects. Diabetic patients had lowe r apoprotein AII and higher CII and E levels than control subjects. Th e plasma lipoproteins in type 1 diabetes mellitus are characterized by increased intermediate density lipoprotein and LDL3 concentrations an d by abnormal LDL2 flotation properties. These lipoprotein abnormaliti es might have a role in atherogenesis in type 1 diabetic patients sinc e similar alterations were associated in some recent epidemiological s tudies with an increased incidence of cardiovascular disease in non-di abetic patients.