Diabetic Nephropathy Is Associated with Oxidative Stress and Decreased Renal Nitric Oxide Production

Abstract

The pathogenesis of diabetic nephropathy remains far from clear, partly due to the lack of a suitable animal model that mimics human renal disease in type 2 diabetes. In this study, the natural history of renal manifestations in ZSF 1 rats, a recently developed rodent model of type 2 diabetes, is described. Male ZSF 1 rats developed obesity and hyperglycemia by 20 weeks of age on a highcarbohydrate diet. They also developed systolic and diastolic hypertension, hypercholesterolemia, profound hypertriglyceridemia, proteinuria, and renal failure. Renal histology demonstrated changes consistent with early diabetic nephropathy, including arteriolar thickening, tubular dilation and atrophy, glomerular basement membrane thickening, and mesangial expansion. Furthermore, renal nitric oxide production was decreased, and homogenates from renal cortices demonstrated reduced expression of renal endothelial and inducible nitric oxide synthases. These changes were associated with increased urinary levels and renal expression of 8-hydroxydeoxyguanosine, an indicator of mitochondrial oxidative stress, as well as with increased renal peroxynitrite formation. Administration of either insulin or the antioxidant alpha-lipoic acid decreased proteinuria and oxidative stress, but only the former slowed progression of renal failure. We conclude that ZSF 1 rats represent the best available rat model to study nephropathy from type 2 diabetes and that the renal lesions are associated with increased oxidative stress and decreased renal nitric oxide availability. 18: 294518: -295218: , 200718: . doi: 10.1681 Despite several recent advances, the pathogenesis of diabetic nephropathy (DN) remains far from clear. 1 The lack of suitable diabetic animal models that develop nephropathy akin to human disease is a major barrier for progress in this field. Notwithstanding the contribution to mechanistic pathways, the in vitro models to study DN have compounded the problem, necessitating more dependable in vivo animal models. Furthermore, the growing epidemic of metabolic syndrome warrants need for animal models that develop hyperlipidemia and obesity in addition to maturity-onset diabetes to mimic complications of human diabetes and metabolic syndrome. We report here a genetically engineered rat that developed features of DN as well as full-blown metabolic syndrome. Furthermore, decreased renal nitric oxide (NO) production was noted in these rats, consistent with our previous observations in mesangial cell cultures in vitro that were exposed to high ambient glucose concentrations. These changes were associated with increased oxidative stress, which partly accounted for decreased NO levels. J Am Soc Nephrol

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Reduction of circulating superoxide dismutase activity in type 2 diabetic patients with microalbuminuria and its modulation by telmisartan therapy

“…Indeed, NO may be extremely important for renoprotection in the diabetic state. Recent experimental studies of diabetic rats and mice have indicated that decreased renal NO levels are associated with the development of renal histologic lesions 31 and that NO deficiency by endothelial NO synthase knockout causes glomerular endothelial injury and overt albuminuria. 32 The reduction of circulating NO in the microalbuminuric stage of DN observed in the present study was probably attributed to the direct scavenging of NO by excessive superoxide, because serum NT levels, which reflect the formation of peroxynitrite by chemical interaction of superoxide with NO, were enhanced in this stage.…”

Zinc Status in Type 2 Diabetic Patients: Relation to the Progression of Diabetic Nephropathy

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