Effect of high plant protein cowpeas (<i>Vigna unguculata</i>) and animal protein (casein) on renal function in rats

Abstract

Recent trends in weight loss diets have been formulated that led to a substantial increase in protein intake. It has however been established that high protein intake impacts negatively on already compromised kidney, while its effect on a healthy kidney remains unclear. Our aim therefore was to study the effect of animal (casein) and plant (cowpeas) proteins on some blood, urine and morphological renal parameters.

Sixty Wistar rats were used in this study. The rats were randomly distributed into 2 experimental groups of A and B (20 per group) and baseline (20). Group A rats were fed with 40% cowpeas diet and group B 40% casein diet. Baseline diet was the normal rat chow with 15% protein from soya beans and fish meal. Blood and 24 hour urine samples were collected at baseline, 1 month, 3 months and 6 months intervals. Creatinine and urea concentrations were measured in urine and blood spectrophotometrically using reagent kits. Glomerular filteration rate (GFR) was determined using Creatinine clearance.

When data obtained in the high protein fed rats (casein and cowpeas proteins) were compared with baseline values, a significant difference was observed in GFR, with rats fed cowpeas diets having a significant increase (P<0.01) in GFR at one month which remained relatively stable at 3 and 6 months. Significant increases (P<0.01) from baseline values at 1 month, which dropped at 3 months and started to increase again at 6 months in serum creatinine and urea concentrations were observed in rats on cowpeas and casein diets. Rats on casein diet had significantly lower (P<0.01) urine output and water intake when compared to baseline values and cowpeas fed rats. Mild morphological changes were observed in the kidney of rats fed cowpeas diet, while rats on casein diet had varied damages. This study has clearly shown that the intake of a high plant protein (cowpeas) does not affect the general functions of the kidney. On the other hand, an intake of high casein diet, an animal protein, induced renal damage as evidenced in the plasma and urine markers used in this study as well as morphological alterations.

Keywords: High animal, plant, protein, renal functions