A717

We recently reported that when diabetic db/db mice, which develop glomerular pathology resembling that in human diabetes mellitus, are treated with monoclonal antibodies (A717) that neutralize the effects of excess glycated albumin, there is an amelioration of mesangial expansion, renal overexpression of mRNAs encoding for the extracellular matrix proteins collagen IV and fibronectin and proteinuria. These findings suggested that A717 might also retard the development of compromised renal function in this animal model. To examine this possibility, serum creatinine and blood urea nitrogen (BUN) were measured in diabetic db/db mice and their non-diabetic db/m littermates before and after an 8-week course of treatment with A717 or irrelevant murine immunoglobulin (MIg). Early in the course of diabetes, BUN and serum creatinine concentrations did not significantly differ from those in the db/m littermates, but were significantly increased after 10 weeks of sustained hyperglycaemia. Treatment of db/db mice with A717 prevented the rise in creatinine and attenuated the elevation in BUN. A717 also prevented the decrease in creatinine clearance observed in diabetic compared with non-diabetic animals (2.2 +/- 0.8 vs 4.1 +/- 0.3 vs 5.0 +/- 1.1 ml/h in db/db vs db/db-A717 vs db/m, respectively). MIg did not alter the change in renal function with time in db/db mice. Taken together with our previous results, the present findings indicate that the diabetic db/db mouse develops changes in renal function and structure that parallel the course of human diabetic nephropathy in nature and chronology and demonstrate, for the first time, that therapy directed against increased glycated albumin can prevent the decline in renal function in this rodent model of genetic diabetes.

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.