Serum N-epsilon-(carboxymethyl)lysine is elevated in nondiabetic coronary heart disease patients

The accumulation of Nxi-(carboxymethyl)lysine (CML), a product of glycoxidation and lipoxidation reactions, on tissue proteins is related to the formation and acceleration of diabetic and nondiabetic atherosclerotic lesions. Yet, little is known about the levels of circulating serum CML-containing protein in nondiabetic patients with clinical symptoms of advanced atherosclerosis. We measured the levels of immunoreactive CML in sera from non-diabetic patients with accelerated symptoms of coronary heart disease, from diabetic patients with no late complications, and from healthy individuals. Serum CML was significantly higher in non-diabetic patients with coronary heart disease than in healthy control subjects and was comparable to serum CML in patients with type 2 diabetes mellitus without late complications and coronary heart disease. In nondiabetic patients with coronary heart disease, a significant inverse correlation was found between serum levels of CML and proinsulin C-peptide, a marker of pancreatic beta cells activity that affects microvascular function. Serum levels of CML and high density lipoprotein (HDL) were positively correlated in this group. We conclude that glycoxidation and lipoxidation are associated with serum HDL levels and the secretive capacity of pancreatic beta cells in nondiabetic patients with coronary heart disease.