Background/aims: Previous observations indicate that protein and calorie restrictions can affect the course of renal disease progression. We compared the effects of selective protein and calorie restriction on glomerular hemodynamics and proteinuria in a model of spontaneous glomerular injury in the rat.
Methods: Three groups of male MWF rats were assigned to three different diets: standard diet (ST, 19% protein, 3.4 kcal/g), low protein (LP) and low calorie (LC). Proteinuria and systolic blood pressure were periodically measured. Glomerular hemodynamics and tuft volume were determined after 2 months of dietary treatment.
Results: The effective mean protein intake was 3.4 +/- 0.4, 1.6 +/- 0.2, and 3.2 +/- 0.2 g/day/rat, respectively, for the ST, LP, and LC diets, while caloric intake averaged 60 +/- 7, 59 +/- 9, and 30 +/- 2 kcal/day/rat. Both LP and LC diets significantly prevented proteinuria (104 +/- 32, 36 +/- 9, and 18 +/- 8 mg/day, respectively, in the three groups). The systolic blood pressure was unaffected by the diets. The LC diet induced lower body and kidney weights than the ST diet. The glomerular filtration rate was slightly but significantly increased by the LP diet, but not by the LC diet (0.64 +/- 0.14, 0.81 +/- 0.08, and 0.67 +/- 0.12 ml/min, respectively, for ST, LP and LC diets). The glomerular hydraulic pressures were not affected by the diets. No differences were also observed in glomerular volume. The incidences of glomerulosclerosis and tubulointerstitial changes were comparable in ST and LP diets and completely absent in the LC diet group.
Conclusion: These results indicate that restriction of both protein and calorie intakes prevents spontaneous proteinuria in male MWF rats by preventing deterioration of glomerular perm-selective functions.