Glycoxidation of LDL Generates Cytotoxic Adducts and Elicits Humoral Response in Type 2 Diabetes Mellitus

Abstract

Abstract This study elucidates the immunological implications of methylglyoxal (MGO) modified LDL in diabetes type 2 patients (T2DM). Under in-vitro modifications, MGO altered the tertiary structure of LDL. TNBS and phenanthrenequinone assays confirmed lysine and arginine residues as main targets of MGO in LDL. HPLC and LCMS studies confirmed the generation of Nϵ-(carboxymethyl) lysine in the modified protein. Comet assay showing increased tail length of DNA in lymphocytes inferred the cytotoxicity of MGO-LDL. The easy penetration of MGO-LDL into the nucleus is possibly a consequence of its reduced size, post-modification, as observed from the studies on hydrodynamic radii studies in DLS experiments. MGO-LDL was found to be more immunogenic, as compared to native LDL, in immunological studies conducted on experimental rabbits. Our results reflect the presence of neo-antigenic determinants on modified LDL. Competitive inhibition ELISA suggested the presence of neo-epitopes with marked immunogenicity eliciting specific immune response. Binding studies on purified IgG confirmed the enhanced and specific immunogenicity of MGO-LDL. Studies on interaction of MGO-LDL with the circulating auto-antibodies from T2DM patients showed high affinity of serum-antibodies towards MGO-LDL. This study suggests a potent role of glycoxidatively modified LDL in the generation of auto-immune response in T2DM patients.