NEPHROLOGY - ORIGINAL PAPER The effect on renal structure and function of late-life-introduced caloric restriction (CR) in rats R. Podkowka-Sieczka Æ K. Wieczorowska-Tobis Æ Z. I. Niemir Æ A. Styszynski Æ A. Breborowicz Æ D. G. Oreopoulos Received: 20 January 2008 / Accepted: 24 October 2008 / Published online: 2 December 2008 Ó Springer Science+Business Media, B.V. 2008 Abstract Previous studies have shown that life-long caloric restriction in rats protects the kidneys from age-dependent injury. In this study, we analyzed whether late-life-introduced caloric restriction has a similar effect. The study lasted 12 months. Three groups of animals were analyzed: rats fed ‘‘ad libitum’’ (AD, n = 9), rats on 60% caloric restriction (CR, n = 9), and rats fed ‘‘ad libitum’’ for the first six months of their life then switched to 60% caloric restriction thereafter (LCR, n = 9). At the end of the study kidney function was assessed and kidney samples were analyzed histologically. Serum creati- nine and urine albumin were higher in AD than in both CR and LCR (P \ 0.001). Creatinine clearance (Cl cr ) corrected for body weight was lowest in AD and comparable in CR and LCR. Similarly Cl cr corrected for kidney weight was lower in AD than in both CR and LCR (P \ 0.05). Severe albuminuria was observed only in AD. In CR and LCR the amount of albumin excreted was comparable (AD vs. CR, P \ 0.0001; AD vs. LCR, P \ 0.001). In morpho- metric analysis, the mean size of the glomeruli was higher in AD than in both CR and LCR (P \ 0.01). Similar results were found for the mesangial area (AD vs. CR, P \ 0.001; AD vs. LCR, P \ 0.01) and for mesangial cell counts (AD vs. CR, P \ 0.001; AD vs. LCR, P \ 0.05). No difference was found between CR and LCR in morphometry. In conclusion, our study indicates that late-life introduction of caloric restriction reverses most of the structural and func- tional changes observed in the kidneys of ‘‘ad libitum’’-fed rats. Keywords Aging Á Caloric restriction Á Rat Á Renal function Á Renal morphology Introduction Aging is associated with degenerative changes in many organs including the kidney [1]. As the kidney has a pivotal role in the maintaining body health and homeostasis, age-related nephropathy has been stud- ied in detail on the basis of many different models, including rat models. Despite the inconsistency of the R. Podkowka-Sieczka (&) Á K. Wieczorowska-Tobis Laboratory for Geriatric Medicine and Gerontology, Department of Pathophysiology, University of Medical Sciences, Ul. Swiecickiego 6, 60-781 Poznan, Poland e-mail: podkowka@ump.edu.pl Z. I. Niemir Department of Nephrology, University of Medical Sciences, Poznan, Poland A. Styszynski Á A. Breborowicz Department of Pathophysiology, University of Medical Sciences, Poznan, Poland D. G. Oreopoulos Division of Nephrology, University Health Network and University of Toronto, Toronto, Canada 123 Int Urol Nephrol (2009) 41:211–217 DOI 10.1007/s11255-008-9499-4