Food restriction retards body growth and prevents end-stage renal pathology in remnant kidneys of rats regardless of protein intake

The objectives of this study were to evaluate the effects of food restriction (without protein or phosphorus restriction) and protein restriction (without the restriction of other nutrients or calories) on the outcome of the remnant kidney model of chronic renal failure in rats. After 5/6 nephrectomy, rats were assigned to one of the following dietary groups: group I (control-ad libitum) consumed a 21% casein diet ad libitum; group II (food restriction with protein restriction) consumed 36% less calories, protein and minerals than group I; group III (food restriction without protein restriction) consumed 36% less calories and minerals than group I, but equivalent amounts of protein; group IV (protein restriction) consumed 38% less protein than group I, but equivalent amounts of calories and minerals; group V (NaCl restriction) consumed 40% less sodium chloride than group I, but equivalent amounts of all other nutrients. All groups consumed equivalent amounts of calcium, phosphorus and vitamins. Groups II and III experienced retardation of growth in comparison to groups I, IV and V. The food-restricted groups II and III, but not groups IV and V, had less proteinuria than group I 20 weeks postablation. By 21 weeks postablation, the kidneys from group I showed severe parenchymal damage, characteristic of end-stage renal pathology. These changes were prevented in the food-restricted groups II and III, but not in groups IV and V. The percentage of glomeruli with severe structural damage was less in groups II (27.3 ± 8.8) and III (26.9 ± 7.5) compared with group I (72.4 ± 7.8). In contrast, the corresponding values in groups IV and V were not significantly different from group I. Interstitial volume (the percentage of tubulointerstitium which is interstitium) which was proportional to the severity of tubular damage was significantly lower in groups II (25.1 ± 4.5) and III (20.4 ± 2.9) when compared with groups I (48.1 ± 3.0), IV (44.4 ± 6.6), or V (41.9 ± 4.2). An interstitial volume less than 30 correlated with well preserved renal histology, whereas a value greater than 40 was indicative of end-stage renal pathology. These results indicate that the restriction of carbohydrate, fat, and minerals (except for calcium and phosphorus) retarded growth and prevented the development of end-stage renal pathology in the remnant kidney model of chronic renal failure in rats, regardless of whether protein was restricted or not. In contrast, protein restriction withouth the restriction of any other dietary component failed to retard growth or protect the remnant kidney. Growth retardation may be a critical factor in nutritional interventions which slow the progression of experimental renal disease.