Dietary soy protein effects on disease and IGF-I in male and female Han:SPRD-cy rats.
BACKGROUND
Dietary soy protein compared with casein retards disease progression in a gender-specific manner in the pcy mouse. In this model of polycystic kidney disease (PKD), kidney insulin-like growth factor-I (IGF-I) levels are elevated. The present study examined the gender-specific effects of soy protein feeding on disease and IGF-I in Han:SPRD-cy rats.


METHODS
Normal (+/+) and affected (cy/+) weanling male and female Han:SPRD-cy rats were given either casein- or soy protein-based diets for six weeks. Renal size, water content, cyst size and IGF-I, serum creatinine, urea and IGF-I, and creatinine clearance were determined.


RESULTS
Soy protein-fed cy/+ animals had lower kidney weight, water content and cyst size, lower serum urea and creatinine, and higher creatinine clearance. In cy/+ females, dietary soy protein resulted in normalized serum creatinine and creatinine clearance. Kidney IGF-I levels (ng/kidney) were 32 to 76% higher in cy/+ compared with +/+ groups (P < 0.001). Soy protein feeding resulted in lower kidney IGF-I in cy/+ males (1123 vs. 1496 ng/kidney, P < 0.001) and cy/+ females (816 vs. 943 ng/kidney, P < 0.05). In males, soy protein feeding resulted in lower serum IGF-I concentrations in +/+ (1439 vs. 1708 ng/mL, P < 0.05) and in cy/+ (1483 vs. 2073 ng/mL, P < 0.001) animals.


CONCLUSIONS
Dietary soy protein compared with casein delays the progression of disease in male and female Han:SPRD-cy rats. Overall, IGF-I was lower in +/+ animals, in females, and in animals consuming the soy protein diet, supporting a role for IGF-I in the pathogenesis of disease in the Han:SPRD-cy rat and an ameliorating role for dietary soy protein.
Aukema
H M
HM
Department of Nutrition and Food Sciences and Center for Research on Women's Health, Texas Woman's University, Denton, Texas, USA. aukemahm@ms.umanitoba.ca
Housini
I
I
D000818:Animals; D002364:Caseins / Q000494:pharmacology; D004044:Dietary Proteins / Q000494:pharmacology*; D018450:Disease Progression; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007668:Kidney / Q000473:pathology; D009929:Organ Size / Q000187:drug effects; D007690:Polycystic Kidney Diseases / Q000097:blood / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012727:Sex Characteristics; D030262:Soybean Proteins / Q000494:pharmacology*
D002364:Caseins; D004044:Dietary Proteins; D030262:Soybean Proteins; D007334:Insulin-Like Growth Factor I