Valsartan slows the progression of diabetic nephropathy in db/db mice via a reduction in podocyte injury, and renal oxidative stress and inflammation

Abstract

Higher doses of AngII (angiotensin II) blockers are intended to optimize albuminuria reduction rather than for blood pressure control in chronic kidney disease. However, the long-term renoprotection of high-dose AngII blockers has yet to be defined. The present study sought to determine whether doses of ARB (AngII receptor blocker) that maximally reduce proteinuria could slow the progression of glomerulosclerosis in the uninephrectomized db/db mouse, a model of Type2 diabetes. Untreated uninephrectomized db/db mice had normal blood pressure, but developed progressive albuminuria and mesangial matrix expansion between 18 and 22weeks of age, which was associated with increased renal expression of TGFβ1 (transforming growth factor β1), PAI-1 (plasminogen-activator inhibitor-1), typeIV collagen and FN (fibronectin). Treatment with valsartan in the drinking water of db/db mice from 18 to 22weeks of age, at a dose that was determined previously to maximally reduce proteinuria, prevented the increases in albuminuria and the markers of renal fibrosis seen in untreated db/db mice. In addition, WT-1 (Wilms tumour protein-1)-immunopositive podocyte numbers were found to be lower in the untreated glomeruli of mice with diabetes. The expression of podocin and nephrin were continually decreased in mice with diabetes between 18 and 22weeks of age. These changes are indicative of podocyte injury and the administration of valsartan ameliorated them substantially. Renal expression of TNFα (tumour necrosis factor α), MCP-1 (monocyte chemoattractant protein-1), Nox2 (NADPH oxidase 2), p22phox and p47phox and urine TBARS (thiobarbituric acid-reacting substance) levels, the markers of renal inflammation and oxidative stress, were increased during disease progression in mice with diabetes. Valsartan treatment was shown to reduce these markers. Thus high doses of valsartan not only reduce albuminuria maximally, but also halt the progression of the glomerulosclerosis resulting from Type2 diabetes via a reduction in podocyte injury and renal oxidative stress and inflammation.