Diabetes, Vol 30, Issue 10 875-878, Copyright © 1981 by American Diabetes Association
Nonenzymatic glycosylation of low density lipoproteins in vitro. Effects on cell-interactive properties
B Gonen, J Baenziger, G Schonfeld, D Jacobson and P Farrar
Atherosclerosis occurs at an accelerated rate in patients with diabetes
mellitus. Since some proteins undergo nonenzymatic glycosylation in
diabetic patients and because certain chemical modifications of low density
lipoproteins produced alterations in their interactions with certain
cultured cells, a fact that may be relevant to atherogenesis, we
investigated the effect of in vitro glycosylation on cell-related
properties of low density lipoproteins. Glycosylation was carried out by
incubating LDL (1-10 mg LDL-protein/ml) with glucose (0-100 mM) in 0.5 M
phosphate buffer, pH 8.0, at 37 degrees C. The amount of glucose
incorporated into LDL after 1-2 wk of incubation was estimated to be in the
range of 1-10 mol/mol LDL-protein. Amino acid analysis of glycosylated LDL
showed that glucose was covalently bound to lysine residues. In studies
with cultured human fibroblasts, glycosylated LDL was internalized and
degraded significantly less than control LDL, in proportion to the
estimated degree of glycosylation (12% of control for the most extensively
glycosylated LDL). Glycosylation of LDL also impaired significantly its
ability to stimulate cholesteryl ester synthesis by cultured fibroblasts.
Glycosylated LDL did not stimulate cholesteryl ester synthesis in rat
peritoneal macrophages. If glycosylation of LDL occurs in diabetic
patients, some pathophysiologic consequences related to the increased
incidence of atherosclerosis in these patients may result.