Characterization of the non enzymatic glycation of high density lipoprotein in diabetic patients.

In diabetic patients, hyperglycaemia results in the non enzymatic glycation of many proteins. We studied the glycation of HDL of patients with either type 1 or type 2 diabetes compared with that of control subjects. Although a basal glycation was detectable in HDL of normal individuals, this increased by about 400% in HDL of both groups of diabetic patients. The degree of HDL glycation was positively correlated with blood glucose concentration. All the HDL apoproteins were glycated but the glycation of apo A-I represented about 80% of the total HDL. These data were compared to those obtained in vitro after incubation of normal apo A-I either as free molecular species or as phospholipid/apo A-I complex, in the presence of glucose (0 to 80 mmol/l) at 37 degrees C. The resulting apo A-I glycation was dependent upon both time of incubation and glucose concentration and was largely increased in the presence of phospholipids. These data suggest that the in vivo glycation of HDL apoproteins might depend upon glucose concentration but might also be partly influenced by their lipid environment.