Glycation and Deamidation Result in HDL Dysfunction in Patients with Type 2 Diabetes

Abstract

Diabetes is associated with HDL dysfunction and perturbed iron metabolism. ApoAI, transferrin (Trf) and ceruloplasmin (Cp) are the key HDL proteins involved in cholesterol efflux and iron metabolism. We tested the hypothesis that hyperglycemia-induced glycation contributes to HDL dysfunction and altered iron metabolism in diet-controlled patients with T2D. HDL from patients with T2D and matched healthy controls (n=9/group) was isolated and it’s anti-oxidant and cholesterol efflux properties were quantified. HDL proteome composition and post-translational modification of proteins were quantified by proteomics aproach. Metabolic 2H2O-labeling was applied to quantify HDL proteome dynamics. Patients with T2D and controls had similar lipid (triglycerides, total cholesterol, and HDL cholesterol) profile. HDL from T2D patients had reduced anti-oxidant (PON1 activity) and macrophage-cholesterol efflux capacity (P<0.05) and was enriched with glycated apoAI and transferrin (Tf), and deamidated ceruloplasmin (Cp), the key HDL proteins involved in cholesterol and iron transport. Both ApoAI and Trf glycation were directly correlated with HbA1c and the extent of glycations were associated with their increased degradation. ApoAI glycation was inversely correlated with cholesterol efflux activity of HDL. Trf glycations at Lys-2and Lys-534 sites involved in iron coordination, were 2-3 fold higher in T2D than in the controls. The PTM search on Cp revealed five asparagine deamidation sites in T2D patients with N-943 being located on one of the oxidation-prone motifs and may result in the loss of Cp’s ferroxidase activity. In vivo HDL flux study demonstrated that glycated apoAI and Tf, and deamidated Cp species were degraded 3, 10, and 2 fold faster than the respective non-modified native proteins. HDL dysfunction and oxidative stress in T2D is related to glycation- and deamidation-induced instability of HDL proteins, including ApoAI, Tf and Cp. Disclosure T. Kasumov: None. M. Golizeh: None. S. Kashyap: None.