Serum Levels of Carbamylated LDL, Nitrotyrosine and Soluble Lectin-like Oxidized Low-density Lipoprotein Receptor-1 in Poorly Controlled Type 2 Diabetes Mellitus

Abstract

Introduction: Carbamylated low-density lipoprotein (cLDL) has profound proatherogenic properties. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as the primary cLDL receptor. The soluble form of LOX-1 (sLOX-1) and 3-nitroty-rosine (NT) have recently been suggested as biomarkers of vascular disease. Although type 2 diabetes mellitus (T2DM) is characterised by an increased atherosclerotic risk, the clinical data on cLDL, NT and sLOX-1 levels in T2DM are limited. Aim: To explore the possible role of cLDL, NT and sLOX-1 as potential biomarkers for disease progression and complications in poorly controlled T2DM patients with and without microalbuminuria. Materials and methods: The serum concentrations of cLDL, NT and sLOX-1 were measured by ELISA in a cross-sectional study of 60 T2DM patients and 35 nondiabetic controls. Results: Both the normoalbuminuric (n = 34) and the microalbuminuric (n = 26) patients had significantly higher serum levels of cLDL and NT than the healthy controls, but sLOX-1 was only elevated in the microalbuminuric subgroup (p < 0.05). Carbamylated LDL correlated positively with NT in the diabetic subjects (rs = 0.266, p = 0.04) while it correlated with urea only in the control group (rs = 0.475, p = 0.004). The serum concentration of sLOX-1 correlated significantly with fasting glucose (rs = 0.441, p < 0.001), HbA1c (rs = 0.328, p = 0.01) and microalbuminuria (rs = 0.272, p = 0.035) in the whole diabetic cohort. Conclusions: The present study highlights the potential of cLDL, NT and sLOX-1 as possible markers of diabetic complications.