DECREASED PLASMA LECITHIN - CHOLESTEROL ACYLTRANSFER AND ASSOCIATED CHANGES IN PLASMA AND RED-CELL LIPIDS IN UREMIA

Plasma lipids, lecithin : cholesterol acyltransferase (LCAT) activity and erythrocyte lipid composition were compared for a group of newly d iagnosed uraemic patients and a group of healthy subjects. Plasma tria cylglycerol was increased and both total and high-density lipoprotein (HDL) cholesterol were decreased. A lower percentage of total choleste rol in patients' plasma was in the esterified form and plasma values o f the phospholipid, lysolecithin, were also lower. The plasma LCAT act ivity of uraemic patients, whether expressed as nmol or percentage of cholesterol esterified per hour, was significantly lower than for norm als. Both LCAT activity and lysolecithin in uraemic plasma were invers ely correlated with the concentration of urea. The lipid composition o f erythrocytes from patients was also abnormal, with both free cholest erol and lecithin being increased. These results are consistent with t he occurrence of an acquired deficiency of LCAT in uraemia, comparable to that previously described in hepatic disease. The LCAT enzyme is s ecreted by the liver, and the inverse correlation noted in this study between LCAT activity and urea suggests that the increased urea in ren al disease may inhibit the synthesis and secretion of the enzyme by th e liver. The resulting reduction in LCAT activity may lead to the accu mulation of cholesterol and lecithin in cell membranes and contribute to the overall pathophysiology of renal disease.