Lecithin:cholesterol acyltransferase activity and high-density lipoprotein subfraction composition in type 1 diabetic patients with improving metabolic control

On initial diagnosis or when metabolic control is poor, subjects with type 1 (insulin-dependent) diabetes mellitus often exhibit decreased high density lipoprotein (HDL) cholesterol levels, which have been associated in numerous studies in non-diabetic subjects with atherosclerosis and coronary artery disease. We measured the activities of plasma lecithin:cholesterol acyltransferase (LCAT), post-heparin lipoprotein lipase, and the composition of the HDL subfractions HDL₂ and HDL₃, in ten poorly controlled type 1 diabetic patients admitted to a metabolic ward (six women and four men, aged 18–37 years). The measurements were repeated after metabolic control had been optimised and again a week after discharge. The results were compared with those of ten healthy normolipidaemic subjects matched for age, sex and body mass. LCAT activity increased significantly (P<0.05) with improved metabolic control in the diabetic patients, and showed positive within — person correlation with HDL₂ cholesterol ester (r=0.67;P<0.01), HDL₂ free cholesterol (r=0.67;P<0.01), phosphatidylcholine (r=0.49;P<0.05), total phospholipids (r=0.50;P<0.01) and apolipoprotein A-I (apo A-I:r=0.72;P<0.01). With improving metabolic control HDL₂ lipid levels increased more than twofold and the compositional changes in HDL₂ were reflected by an increased apo A-I:apo A-II ratio (P<0.05) and a decreased triglyceride:apo A-I ratio (P<0.05). Changes in HDL₃ levels and composition were minor. The results of this study indicate that an increase in LCAT activity increases the concentration and changes the composition of HDL₂ in type 1 diabetic patients with improved metabolic control.