Analysis of glycated serum proteins in type 2 diabetes patients with nephropathy

The aim of this study was to screen for proteins that are susceptible to glycation under hyperglycemic conditions in patients with type 2 diabetic nephropathy. Serum proteins were analyzed by a proteomic approach using two-dimensional electrophoresis (2-DE) and ESI-Q-TOF MS/MS. Gels were stained with Pro-Q Emerald 488 to analyze the serum glycoproteome, followed by silver nitrate to examine the total serum proteome. Patient sera were divided into four groups according to their microalbuminuria index: type 2 diabetics with normoalbuminuria, microalbuminuria, and overt nephropathy, and healthy subjects. When the HbA1c levels of the diabetic groups were examined, groups with higher HbA1c exhibited higher fructosamine levels, suggesting that the loss of glycemic control affected the glycation of serum proteins. The proteins that became glycated under poor glycemic control were PEDF, apolipoprotein J precursor, hemopexin, immunoglobulin mu heavy chain, and immunoglobulin kappa chain. As albuminuria increased, a marker of kidney damage, the levels of glycated prekallikrein and complement factor C4B3 also increased. The glycated proteins identified in this study may provide the foundation for the development of novel markers of diabetes, hyperglycemia, and diabetic complications.