DYSLIPOPROTEINEMIA IN MANIFEST DIABETES

The prevalence of hypercholesterolaemia is similar in non-insulin-depe ndent diabetic (NIDDM) patients and in non-diabetic subjects. The prev alence of hypertriglyceridaemia and of low high-density-lipoprotein (H DL) cholesterol is roughly double the norm in NIDDM, but the exact pre valence varies greatly from study to study. Obesity and a familial for m of hypertriglyceridaemia (conditions that may alter plasma lipoprote in levels) are frequently observed in NIDDM patients. In carefully con trolled NIDDM patients without concomitant primary hyperlipoproteinaem ia, body weight may be more important than glycaemic control or the ty pe of treatment plan adopted in determining lipoprotein levels. Hypert riglyceridaemia in NIDDM is a result of both increased very-low-densit y-lipoprotein (VLDL) synthesis and impaired VLDL catabolism. Whilst lo w-density-lipoprotein (LDL) levels are normal, the LDL synthesis and r emoval rates may be increased. Low high-density-lipoprotein (HDL) leve ls may be due to increased catabolism. In addition to quantitative cha nges in plasma lipids and lipoproteins, NIDDM patients demonstrate qua litative lipoprotein alterations. The size and density of LDL particle s in NIDDM patients are greatly affected by triglyceride levels. Small er, denser LDL particles have been observed in hypertriglyceridaemic s ubjects. Glycosylation of apolipoproteins may alter the metabolic prop erties of lipoproteins. Glycosylated and small, dense LDL have an incr eased susceptibility to oxidation.