The effects of dietary
soy protein compared to
casein were examined in male and female CD1-pcy/pcy (pcy) mice with
polycystic kidney disease. Animals 10 wk of age were fed purified diets containing either
soy protein isolate or
casein given at a level of 17.4 or 6%
protein. After 13 wk on the diets,
body weights and serum concentrations of
albumin and
protein indicated that
protein nutrition was adequate on all diets. Overall, animals fed
soy protein versus
casein had 28% lower (P = 0.0037) relative kidney weights (g/100 g body wt), 37% lower (P = 0.0089)
cyst scores (%
cyst area x relative kidney weight), and 25% less (P = 0.0144) kidney water (g).
Dietary protein reduction resulted in 30% lower (P = 0.0010) relative kidney weights, 25% lower (P = 0.0327)
cyst scores, and 35% less (P = 0.0001) kidney water. Analysis of interactions between main effects revealed that the effects of
soy protein on kidney size were significant only in females, and that effects of
soy protein on
cyst score were significant only in animals on the
low protein diets. In addition, differences in kidney weights and
cyst score due to
protein reduction were significant in animals fed
soy protein, but not in those fed
casein as the
protein source. These results show that both
dietary protein source and level significantly affect
polycystic kidney disease in pcy animals, with the effects of dietary
soy protein being most pronounced in female animals fed the
low protein diets and the effects of
protein reduction being most pronounced in animals fed
soy protein-based diets.