Determinants of glycated LDL levels in nondiabetic and diabetic hyperlipidaemic patients in Kuwait.

Background: Glycation and oxidative modification of lipoproteins enhance the uptake of these lipids by macrophages in the early stages of atherogenesis. Measurement of blood levels of modified LDL particles could thus constitute another useful modality in identifying subjects at high risk of coronary atherosclerosis (CHD).
Objective: To measure the glycated LDL level and assess its associations with other metabolic parameters in diabetic and nondiabetic hyperlipidaemic subjects attending a Lipid Clinic in Kuwait.
Subjects and Methods: One hundred thirty-three hyperlipidaemic (HL) (72 nondiabetic (ND); 61 diabetic (D)) patients and 42 healthy control (HC) subjects had their fasting serum samples analyzed for glucose, total cholesterol (TC), triglycerides (TG), urate, HDL, LDL (by routine autoanalyzer methods), apolipoproteins A1 and B (by nephelometry), fructosamine (by spectrophotometry) and glycated LDL (gLDL) by ELISA.
Results: The serum gLDL level was significantly higher in HL [D+ND] than in HC (p<0.001). Within the HL group, the DHL patients had higher levels than the NDHL [p<0.001]. These differences were maintained when the gLDL level was also expressed as a percentage of the apo B concentration. The gLDL level correlated positively (p<0.01) with those of glucose, TC, TG and LDL and negatively with HDL (p<0.05) in all the subjects as a whole, healthy and hyperlipidaemia [HC+HL]. In the HL (D+ND) group as a whole, gLDL correlated significantly only with glucose [p<0.01]. In group DHL, however, gLDL correlated significantly with glucose, fructosamine and LDL [all p<0.05]. As expected, fructosamine levels were highest in the DHL group. The significant correlations established between fructosamine and the different analytes measured in the different subject groups were essentially similar to those observed for gLDL, except for the finding of persistent significant negative correlations of fructosamine with LDL in all the subject groups.
Conclusions: (i) Serum gLDL levels are increased in hyperlipidaemic patients and are further increased with diabetes, suggesting that the significant glycation of LDL occurs in all hyperlipidaemic patients irrespective of their glycaemic status. (ii) The significant correlation of gLDL with glucose and fructosamine in diabetic patients would suggest its potential utility as another index of medium term glycaemic control. (iii) gLDL is easily measurable and its values could provide additional information in ascertaining an individual's aggregate CHD risk.