Lipid changes in the nephrotic syndrome: new insights into pathomechanisms and treatment

The abnormalities of lipid metabolism in nephrotic syndrome consist in an increase in total and low-density lipoprotein (LDL) cholesterol, apolipoproteins B (ApoB), C-II and C-III, associated in patients with heavier or marked hypoalbuminemia with an increase in triglycerides and very low-density lipoprotein (VLDL) cholesterol, while the high-density lipoproteins (HDL) are distributed abnormally (increased HDL3 fraction and decreased HDL2 fraction) and the Apo A-I to Apo B ratio is reduced. Both increased hepatic lipoprotein synthesis and reduced removal capacity contribute to this hyperlipidemia. Proteinuria may lead to the lipoprotein abnormalities through stimulation of VLDL synthesis by the liver induced by hypoalbuminemia, although it has been more recently suggested that urinary protein loss is associated with the urinary loss of some important cofactor for the regulation of lipid synthesis or catabolism. Treatment of lipid abnormalities in patients with long-lasting heavy proteinuria is mandatory, because they may cause or contribute to accelerated atherosclerosis, but also because they appear to accelerate progression of renal disease by favouring mesangial sclerosis. Four groups of lipid-lowering drugs have been tested: 1) bile acid-binding resins; 2) fibric acid; 3) probucol; 4) inhibitors of HMG CoA reductase. The drugs of the last group appear to be effective and safe in short-term experiments, but long-term studies are necessary to confirm their validity. A dietary approach, consisting in a strictly vegetarian soy diet, very rich in poly- and monounsaturates fatty acids, has been recently tested by the author, with very promising results.