Lipid abnormalities in the nephrotic syndrome: causes, consequences, and treatment

Hyperlipidemia so commonly complicates heavy proteinuria that it has come to be regarded as an integral feature of the nephrotic syndrome (NS). Characteristically, total plasma cholesterol and triglyceride levels are elevated, as are very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterol. Although high-density lipoprotein (HDL) concentrations may be normal, HDL subtypes are abnormally distributed, with a reduction of HDL2 and an increase in HDL3. In addition, lipoprotein (a) [Lp (a)] levels may be elevated. The mechanisms underlying these abnormalities are multifactorial, involving both increased rates of lipoprotein synthesis and defective clearance and catabolism of circulating particles. Although recent dietary and therapeutic studies have demonstrated that nephrotic hyperlipidemia can be effectively treated, the need for such intervention has not been clearly established. This pattern of lipoprotein abnormality is associated with an increased risk of cardiovascular disease in the general population, and several studies have suggested that nephrotic individuals are more likely to develop atherosclerosis. However, no prospective trials have evaluated the relationship between deranged lipid metabolism and coronary or cerebral artery disease in patients with NS. In addition, although recent experimental studies suggest that lipid abnormalities may accelerate renal injury and that lipid-lowering agents may protect renal function, there is little current evidence to suggest that such intervention is of value in preserving residual renal function in humans. Further studies are clearly required to assess the potential long-term benefits of lipid-lowering intervention in individuals with NS. In the meantime, based on data generated from other population groups, a rational approach to the clinical management of hyperlipidemia in these patients is presented.