DYSLIPOPROTEINEMIA IN MANIFEST DIABETES

The prevalence of hypercholesterolaemia is similar in non-insulin-dependent diabetic (NIDDM) patients and in non-diabetic subjects. The prevalence of hypertriglyceridaemia and of low high-density-lipoprotein (HDL) cholesterol is roughly double the norm in NIDDM, but the exact prevalence varies greatly from study to study. Obesity and a familial form of hypertriglyceridaemia (conditions that may alter plasma lipoprotein levels) are frequently observed in NIDDM patients. In carefully controlled NIDDM patients without concomitant primary hyperlipoproteinaemia, body weight may be more important than glycaemic control or the type of treatment plan adopted in determining lipoprotein levels. Hypertriglyceridaemia in NIDDM is a result of both increased very-low-density-lipoprotein (VLDL) synthesis and impaired VLDL catabolism. Whilst low-density-lipoprotein (LDL) levels are normal, the LDL synthesis and removal rates may be increased. Low high-density-lipoprotein (HDL) levels may be due to increased catabolism. In addition to quantitative changes in plasma lipids and lipoproteins, NIDDM patients demonstrate qualitative lipoprotein alterations. The size and density of LDL particles in NIDDM patients are greatly affected by triglyceride levels. Smaller, denser LDL particles have been observed in hypertriglyceridaemic subjects. Glycosylation of apolipoproteins may alter the metabolic properties of lipoproteins. Glycosylated and small, dense LDL have an increased susceptibility to oxidation.