Abstract 133: Effects of Valsartan and Clofibrate on Oxidative Stress and Fatty Acid Metabolism in the Kidney of Puromycin-induced Nephrotic Rats

Abstract

Fatty acids (FAs) bound to albumin are overloaded to renal proximal tubules in proteinuria and contribute to tubulointerstitial damage. Angiotensin II receptor blocker (ARB) and fibrate have renal protective effects in proteinuria, however it isn’t clear they have effects on fatty acid metabolism (FAM) in the nephrotic kidney. The study tested effects of valsartan and clofibrate on FAM in the nephrotic kidney. Sprague-Dawley rats were used and nephrotic syndrome was induced by Puromycin Aminonucleoside (PAN; 100 mg/kg, iv). Rats were randomly divided into four groups; (1) control group; (2) PAN group; (3) PAN rat treated with valsartan group (PAN+val; 30mg/kg/day, orally); (4) PAN rat treated with clofibrate group (PAN+clo; 500 mg/kg/day, sc). Rats were killed on the 14th day and urinary 8OHdG, a marker of oxidative stress in the kidney, and NAG, a marker of proximal tubular cell damage, were measured. The protein expression of enzymes in the kidney was analyzed by Western blot and immunohistochemistry. Compared with the control group, in the PAN group 8OHdG and NAG increased to 154% and 903% and Western blot showed the protein levels of medium-chain acyl-CoA dehydrogenase (MCAD), a mitochondrial β-oxidation enzyme, cytochrome P450 (CYP)4A, a microsomal ω-hydroxylase of FAs, and PPARγ coactivator-1α (PGC-1α), a regulator of mitochondrial function, decreased respectively to 55%, 54% and 51% without change of the protein level of PPARα, a nuclear receptor regulating FAM. In the PAN+val group proteinuria, 8OHdG and NAG decreased respectively to 57%, 76% and 35% in comparison with the PAN group. In the PAN+clo group proteinuria and NAG decreased to 58% and 28%, but 8OHdG increased additionally to 142% in comparison with the PAN group. Valsartan and clofibrate ameliorated the decreased protein levels of MCAD and CYP4A, but didn’t ameliorate the expression level of PGC-1α. Immunohistochemistry showed the localization of MCAD, CYP4A and PGC-1α in the proximal tubule and confirmed the results by Western blot. ARB and fibrate reduced proteinuria and proximal tubular damage, and ameriorated the disorder of MCAD and CYP4A in the nephrotic kidney. The different effect on 8OHdG in ARB and fibrate would suggest they have variant influence on oxidative stress in the kidney.