Apolipoprotein E phenotype frequency in type II diabetic patients with different forms of hyperlipoproteinemia

Atherosclerosis is the main cause of death in diabetes mellitus. This may at least in part be due to lipoprotein abnormalities which have been described in these patients. Apolipoprotein-E is a component of most lipoprotein fractions and plays an important role in the catabolism of VLDL. The different apolipoprotein-E phenotypes determined genetically are associated with certain hyperlipoproteinemias in a various degree in nondiabetic patients. In most cases apolipoprotein-E phenotype E2/2 is characteristic for familial dysbetalipoproteinemia. Phenotype E3/2 was found to be more frequent in hypertriglyceridemia while phenotype E4/3 was associated with hypercholesterolemia as well as with type V hyperlipoproteinemia. We studied apolipoprotein-E phenotypes and serum lipids in 141 type II diabetic patients (36 normolipidemic 41 type IIa hyperlipidemic, 32 type IIb hyperlipidemic, 24 type II hyperlipidemic, 8 type V hyperlipidemic). the phenotype E3/3 was more common in normolipidemic diabetic (77.8%) than in hyperlipoproteinemic diabetic patients (42.9%) or in the control group (57.5%). On the other hand phenotype E3/2 was more frequent in hypertriglyceridemic (50%) than in normolipidemic (5.6%) or hypercholesterolemic (hyperlipoproteinemia IIa: 4.9%, IIb: 9.4%) diabetic patients. The phenotype E4/3 was more frequent in all hyperlipoproteinemic diabetic patients, especially in those having hypercholesterolemia (34.2%) or mixed hyperlipidemia (50%). In conclusion we found a strong association between apo-E2 and hypertriglyceridemia in diabetic patients. This association was stronger than the one found in the general population. The association between apo-E4 and hypercholesterolemia in diabetic patients was similar to the one described in non-diabetic patients. We therefore conclude that type II diabetes mellitus is a possible cofactor in the apolipoprotein-E2 associated hyperlipoproteinemia.