[A fundamental study on the metabolism of glycosylated low-density lipoprotein]

Low-density lipoprotein (LDL) is considered to be one of the accelerating factors in atherosclerosis. Recently, it has been pointed out that nonenzymaticaly glycosylated LDL (Glc.LDL) is increased in the blood of diabetic patients. In this study, the binding ability of Glc.LDL to culturer cells and its clearance rate in New Zealand White rabbits were examined to the purpose of elucidating those metabolism. Human LDL was taken from healthy subjects and prepared by the ultracentrifugation method, then was glycosylated in vitro by adding [D]glucose. The incorporation of covalently bound glucose increased linearly from beginning and get to the plateau after 12 days of incubation. Surface binding of 125I-Glc.LDL to cultured human fibroblasts was low degree compared to that of native 131I-LDL. The clearance rate of 125I-Glc.LDL in rabbits was slower than that of native 131I-LDL. The half-time for Glc.LDL was 85 hours, and for native LDL the time was 10 hours. Finally, Glc.LDL in human plasma was measured by a m-aminophenylboronic acid affinity column. Preliminary data revealed that the Glc.LDL level was 10.6 +/- 3.0% in diabetic patients (n = 21) and 5.25 +/- 1.1% in non-diabetes (n = 18). The relationships between Glc.LDL and glucose in human plasma for all patients (n = 39) showed linearity and the correlation coefficient was about 0.87 (p less than 0.001).