Role of Amadori-modified nonenzymatically glycated serum proteins in the pathogenesis of diabetic nephropathy.

Abstract

Accelerated nonenzymatic glycation in diabetes, resulting in Amadori-modified proteins and the later-developing advanced glycation end-products, has been mechanistically linked to the pathogenesis of diabetic nephropathy. Recent focus on putative AGE-induced pathophysiology has shifted attention from the possible role of Amadori-modified proteins in the development of diabetic complications. Ample experimental evidence has demonstrated that Amadori-modified serum proteins adversely affect renal glomerular capillary function, structure, and metabolism. Previous studies from the laboratories of this study's authors have shown that human serum containing diabetic concentrations of albumin modified by Amadori-glucose adducts inhibits the replication of murine mesangial cells in culture and stimulates the production and gene expression of type IV collagen. Monoclonal antibodies (A717) specific for Amadori-glycated albumin prevent these abnormalities. In other studies, it has also been shown that in vivo administration of A717 (Fab fragments) retards the progression of diabetic nephropathy in diabetic db/db mice. Neutralizing the effects of the elevated circulating glycated albumin concentration is associated with reduction in proteinuria and mesangial matrix expansion, and prevention of the overexpression of mRNA encoding type IV collagen and fibronectin in the renal cortex. The renoprotective effects of A717 are independent of any change in blood glucose concentrations. These studies implicate Amadori-modified glycated albumin in the pathogenesis of diabetic nephropathy. It is proposed in this study that abrogating the biologic effects of increased glycated albumin in diabetes has novel therapeutic potential in the management of diabetic renal complications.