The effects of feeding a
soy protein isolate or
genistein, an isoflavonoid present in
soy protein, on
cyst development were examined in the DBA/2FG-pcy (pcy) mouse, an accepted animal model of
polycystic kidney disease, before the appearance of clinical symptoms. In study 1, 60-day-old male pcy mice were evenly divided into two groups and fed semipurified diets, based on
casein or a
soy protein isolate (15
g protein/100 g diet) for 90 days. In study 2, the animals were fed a
casein-based diet (25 g
casein/100 g diet) with or without
genistein (0.05 g/100 g diet) for 60 days. In study 1, total kidney weight and kidney weight relative to
body weight were significantly reduced (by 24% to 25%) in the animals fed the
soy protein-based diet, relative to the
casein-fed group, as was kidney water content (by 38%). In addition, mean
cyst volume, as measured by morphometry, were lower (by 25%) in kidneys from the
soy protein-fed group. No differences were found between these two groups with respect to final
body weight, plasma
creatinine, and
protein content; however, plasma
urea values were significantly lower in the
soy protein-fed animals.
Genistein supplementation of a
casein-based diet in study 2 did not reduce the renal enlargement and
cyst development associated with progression of
polycystic kidney disease. These results suggest that
soy protein is effective in retarding
cyst development in the pcy mouse and that this beneficial effect may be unrelated to its
genistein content.