HYPERLIPIDEMIA OF CHRONIC-RENAL-FAILURE

Plasma triglycerides are increased in the majority of patients with advanced renal failure but cholesterol is not. HDL cholesterol is reduced while LDL IDL and VLDL cholesterol is increased. Lecithin:cholesterol acyltransferase (LCAT), an enzyme necessary for HDL maturation, is reduced in chronic renal failure (CRF). As a consequence, while all subtypes of HDL are reduced, the small HDL(3) subtype is relatively enriched at the expense of the larger, more functional HDL(2) subtype. Triglycerides are increased in all lipoprotein fractions. HDL-associated apolipoproteins, ape A-I and A-II are decreased, while apo B is increased. Lipoprotein catabolic rate is reduced, but the cause of hyperlipidemia is multifactorial; reduced lipoprotein lipase (LPL) activity, increased concentration of apo C-III (a specific inhibitor of LPL) in plasma, secondary hyperparathyroidism, insulin resistance. Hyperlipidemia is not corrected by dialysis. Lipid levels are somewhat higher in CAPD patients, possibly as a consequence of increased glucose absorption or as a consequence of transperitoneal HDL losses. Triglycerides decrease and cholesterol increases following transplantation. Oxidized lipids are increased in plasma of patients with CRF. Plasma polyunsaturated fatty acids are decreased and saturated fatty acids increased. The same changes occur in the lipid bilayers composing leukocytes and red blood cell membranes. These changes result in altered membrane fluidity, and are corrected by dialysis. While atherosclerotic disease is a leading cause of death in dialysis patients, it is not certain that the specific lipid disorders of CRF are responsible for this morbidity, nor is it recommended at this time that qualitative abnormalities be treated pharmacologically in the absence of increased lipid levels.