Protective effects of combined vitamin E and vitamin C supplementation on renal functions and Klotho protein levels in hyperoxaluric rats

Abstract

Effects of combined vitamin E and vitamin C supplement on renal functions, oxidative stress status and Klotho protein levels in hydroxy-l-proline (HLP) induced hyperoxaluria in rats were investigated for 21 days’ duration. The experimental study was divided into two parts; part I and part II. The seventy male Sprague Dawley rats were divided randomly into 5 groups: control (group 1), hyperoxaluric rats (group 2), hyperoxaluric rats with vitamin E supplement (group 3), hyperoxaluric rats with vitamin C supplement (group 4) and hyperoxaluric rats with vitamin E and C supplement (group 5). Hyperoxaluria was induced by feeding hydroxyl-L-proline (HLP) dissolved in drinking water. Intraperitoneal 200 mg/kg of vitamin E was given twice a week in group 3 and 5 while 500 mg of vitamin C was injected intravenously once a week in group 4 and 5. At the end of the study, clearance study was performed in the part I of the study while the vascular perfusion fixation was performed in the part II of the study for collection of the kidney tissues on day 21.

At the end of the study, the results showed that the urinary excretion of oxalate was significantly higher in HLP-treated group when compared with a control group (p<0.05) while it was maintained in group 3 and 5. The glomerular filtration rate (GFR), water and sodium reabsorption at the proximal tubule were drastically decreased in group 2 and improved considerably in group 3, 4 and 5. The total antioxidant status in urine (UTAS) decreased while the levels of malondialdehyde in plasma (PMDA) were significantly increased in group 2 as comparable with group 1 and they were reversed after receiving antioxidant alone or in combination (group 3, 4 and 5). The urinary calcium oxalate crystals increased in group 2 and reduced after receiving vitamin E and/or C (group 3-5). Additionally, vitamin E and/or C stabilized the activity of superoxide dismutase (SOD) in the kidney tissue, as comparable with group 2. Plasma and kidney Klotho protein were reduced significantly in group 2 while the vitamin E and/or C was improved the levels of Klotho protein in the plasma and kidney tissues. Furthermore, the histopathology demonstrated that vitamin E and/or C could preserved structural damage of glomerular and tubular part of kidney as compared to group 2. The most improvement of all parameters were seen in group 5 while receiving vitamin E and C which was supported by maintaining kidney GSH level when receiving HLP.

It is concluded that in rats with hyperoxaluria induced by HLP had diminished on renal functions, enhanced oxidative stress status and, lowered Klotho protein levels. Vitamin E and/or C can preserve the kidney functions and histopathology lesions with increased kidney Klotho protein expression especially when giving in combination which may be mediated by antioxidant effects.