Long-term dietary vitamin e prevents age-related decrease in renal function in rats

Free radical production leading to oxidative damage has long been thought to be an important mechanism involved in aging. The present study was performed to determine if long-term dietary supplementation with an anti-oxidant would prevent age-related decrements in renal function. Male Sprague Dawley rats, aged 12-13 mos, were given a diet with Vitamin E (5000U/kg) (n = 6) or a control diet (n = 6), which contained all ingredients except Vitamin E, for 9 months. Urinary protein excretion rates were not different between the groups during the months of feeding. Renal function was measured in the anesthetized rats at 21-22 mos of age. Kidney and body weights were similar. Data are expressed as mean ±SEM; *, p < 0.05. MAP GFR/g RPF/g RVR (mmHg) (ml/min/g) (ml/min/g) (mmHg/ml/min) controls 123±6 0.44±0.05 1.9710.31 19.28±4.25 Vit E 117±4 0.64±0.06* 2.78±0.36 12.33±2.13 Arterial pressure (MAP) was not different between the groups. Vitamin E diet prevented the age-related decrease in GFR and tended to improve renal plasma flow (RPF) and renal vascular resistance (RVR), although they were not statistically different. Malondiaidehyde levels in kidneys were also measured as an index of oxidative stress and were significantly lower in the Vitamin E treated rats than in the control rats (controls: 3.0±0.3; Vit E: l .910. l nmol/mg protein). These data show that long-term treatment with Vitamin E improves age-related decreases in renal function at least in part by decreasing oxidative stress.