Progression of renal failure: role of apolipoprotein B-containing lipoproteins.
Plasma lipoproteins (LP) may be identified on the basis of density properties or apolipoprotein (apo) composition. ApoB-containing LP occur in VLDL, IDL and LDL. There are several types of apoB-containing LP characterized by specific composition of minor apolipoproteins (apoC, apoE etc.) and lipid constituents (triglycerides and cholesterol), metabolic properties and relative atherogenicity. The alterations of lipoprotein metabolism in renal disease resulting in elevated levels of apoB-containing LP may be reflected in hyperlipidemia. Whereas nephrotic syndrome and heavy proteinuria are associated with increased formation of cholesterol-rich apoB-containing LP in LDL and VLDL, the characteristic feature in renal failure is the accumulation of intact or partially metabolised triglyceride-rich LP in IDL and VLDL. The potentially atherogenic apoB-containing LP have been linked to the pathogenic processes that result in progressive glomerular and interstitial lesions and ultimate loss of renal function. The mechanisms of injury are not fully understood. Receptor- and non-receptor mediated uptake of LP by mesangial cells may induce or accelerate proliferative and sclerotic processes in the glomerular mesangium that are analogous to atherosclerosis in the arterial wall. Changes in glomerular permeability can result in increased filtration of LP that may be internalized by tubular cells and elicit corresponding lesions in the interstitial tissues. The negative impact of proteinuria on the prognosis of renal disease could be mediated in part through an increased filtration of lipoproteins. Induction of hyperlipidemia accelerates glomerular and interstitial damage in experimental renal failure. This can be attenuated by treatment with hypolipemic agents. In patients, increased concentrations of apoB-containing LP are associated with more rapid progression of renal insufficiency in both primary renal disease and diabetic nephropathy. It is, however, presently not known to what extent treatment of the renal dyslipidemia can modify the progression of chronic renal failure. Experimental and clinical evidence suggest that apoB-containing LP may play a pathogenetic role in the progression of renal disease.