REDUCED LECITHIN - CHOLESTEROL ACYLTRANSFERASE (LCAT) AND NA-PATIENTS(,K+,ATPASE ACTIVITY IN DIABETIC)

Objectives: To investigate the plasma concentrations of lecithin:chole sterol acyltransferase (LCAT EC 2.3.1.43) and erythrocyte membrane Na,K+,ATPase and the correlation of these parameters in diabetes mellitu s. Design and Methods: Na+,K+,ATPase was measured with spectro-photome tric method and LCAT with radioactive method in 19 patients with insul in-dependent diabetes mellitus (IDDM), in 20 with non-insulin-dependen t diabetes mellitus (NIDDM) and in 20 healthy volunteers as the contro l group. Results: Compared with the control group, plasma LCAT concent rations were found to be decreased in both of the patient groups (p < 0.01 for both). Erythrocyte membrane Na+,K+,ATPase activities were hig her in the controls than both in the NIDDM and IDDM groups (p < 0.01 a nd p < 0.001, respectively). There were significant correlations betwe en LCAT and Na+,K+,ATPase in IDDM (r = 0.82, p < 0.001) and in NIDDM ( r = 0.74, p < 0.001). In order to investigate the effect of cholestero l (C) and lysophosphatidylcholine (LPC) on Na+,K+,ATPase activity, thi s enzyme's activity was determined in erythrocyte membranes obtained f rom diabetic subjects after in vitro incubation with increasing concen trations of LPC and C (2-10 mu M). Enzymatic activity was significantl y reduced by in vitro C at increasing concentrations but significantly increased by in vitro LPC at increasing concentrations. Conclusions: From these data, it is to be concluded that the decrease in Na+,K+,ATP ase activity in diabetes might be due to decreased LCAT concentrations and that may explain the development of atherosclerosis in diabetics.