Life-long caloric restriction suppresses age-associated Fas expression in the Fischer 344 rat kidney.

It has been shown that the expression of Fas is substantially increased in the aging process in various organs, but its role in the aging kidney is not yet clear. In this study, the expression of Fas in the kidneys of 6- and 24-month-old male Fischer 344 rats fed ad libitum was studied by using quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. In addition, possible effects of life-long caloric restriction (30% as those of ad libitum fed group) in the expression of Fas were also studied in 6- and 24-month-old rat kidneys. Kidneys obtained from 24-month-old ad libitum fed rats showed glomerulosclerosis with marked tubulointerstitial damage including interstitial fibrosis, while in the kidneys of 24-month-old calorie-restricted rats, renal damage was remarkedly less than that noted in 24-month-old ad libitum fed rats kidneys. RT-PCR and immunohistochemical analysis showed an increased expression of Fas in both mRNA and protein level in 24-month-old rat kidneys; life-long caloric restriction significantly reduces renal expression of Fas. Our results suggest that increased expression of Fas is associated with age-related renal damage and that life-long diet-restricted alteration of its expression is associated with the modulation of age-associated renal structural damage.