Lipoprotein Metabolism in Diabetics Treated with Diet, Oral Hypoglycemic Drug and Insulin

Abstract

In view of the high incidence of hyperlipidemia and the low sialic acid content in the membranes of diabetics, we analyzed the percentage composition of apolipoprotein CII, known as an activator of lipoprotein lipase, and a subspecies of apolipoprotein CIII, an inhibitor of lipoprotein lipase, in triglyceride-rich lipoproteins. CIII can be sub-divided into three groups, CIIl₀, CIII₁ and CIII₂, according to sialic acid content by isoelectric focusing gel. In 82 diabetics, serum lipids and lipids in various lipoprotein fractions differed according to treatment, (diet, oral hypoglycemic drug or insulin). CIIIo/CII showed a positive correlation to plasma triglyceride and cholesterol. In the group receiving oral medication (N=20), CIIIo/CII vs HDL-cholesterol showed a positive correlation, whereas CIII₂/CII vs plasma triglyceride showed an inverse correlation. In the insulin group (N=25), the percentage of CIIIo in VLDL apo C subspecies was inversely correlated with plasma cholesterol. In 38 diabetics whose HbA₁ was also examined, CIIIo/CII increased with elevation of HbA₁. CIIIo/CII in diabetics with HbA₁ higher than 10% was significantly high compared with the index in other diabetics. The percentage of CIII₁ in VLDL apo C subspecies was correlated to HbA₁ level positively in the diet group but inversely in the insulin group. These results suggest that lipoprotein metabolism in diabetics may vary according to treatment and the sialylation of apolipoprotein may play an important role in determining the severity of this disease.