Effect of Soyabean Isoflavones Exposure on Onset of Puberty, Serum Hormone Concentration and Gene Expression in Hypothalamus, Pituitary Gland and Ovary of Female Bama Miniature Pigs.

This study was to investigate the effect of soyabean isoflavones (SIF) on onset of puberty, serum hormone concentration, and gene expression in hypothalamus, pituitary and ovary of female Bama miniature pigs. Fifty five, 35-days old pigs were randomly assigned into 5 treatment groups consisting of 11 pigs per treatment. Results showed that dietary supplementation of varying dosage (0, 250, 500, and 1,250 mg/kg) of SIF induced puberty delay of the pigs with the age of puberty of pigs fed basal diet supplemented with 1,250 mg/kg SIF was significantly higher (p<0.05) compared to control. Supplementation of SIF or estradiol valerate (EV) reduced (p<0.05) serum gonadotrophin releasing hormone and luteinizing hormone concentration, but increased follicle-stimulating hormone concentration in pigs at 4 months of age. The expression of KiSS-1 metastasis-suppressor (KISS1), steroidogenic acute regulatory protein (StAR) and 3-beta-hydroxysteroid dehydrogenase/delta-5-delta-4 isomerase (3ß-HSD) was reduced (p<0.01) in SIF-supplemented groups. Expression of gonadotropin-releasing hormone receptor in the pituitary of miniature pigs was reduced (p<0.05) compared to the control when exposed to 250, 1,250 mg/kg SIF and EV. Pigs on 250 mg/kg SIF and EV also showed reduced (p<0.05) expression of cytochrome P450 19A1 compared to the control. Our results indicated that dietary supplementation of SIF induced puberty delay, which may be due to down-regulation of key genes that play vital roles in the synthesis of steroid hormones.

Dietary soy isoflavones differentially regulate expression of the lipid-metabolic genes in different white adipose tissues of the female Bama mini-pigs.

Soy isoflavones have been shown to affect lipid metabolism, however the underlying molecular mechanism(s) have not yet been fully understood. The present study, using female Bama mini-pig as a model, examined the effects of soy isoflavones on lipid metabolism and involved gene expression in different white adipose tissues. Female Bama Xiang mini-pigs of 35 days old were fed a basal diet (control, Con), or basal diet supplemented with increasing amounts of soy isoflavones (250, 500, or 1250 mg/kg diet) for 120 days. The results showed that soy isoflavones did not affect the body weight, but decreased the dorsal subcutaneous adipose tissue (DSA) mass and increased the mass of abdominal subcutaneous adipose tissue (ASA) and perirenal adipose tissue (PRA). Besides, soy isoflavones decreased the expression of lipogenic genes and increased the expression of lipolytic genes in DSA, while the opposite effects were observed in ASA and PRA. In addition, the expression of lipoprotein lipase was down regulated in DSA while up regulated in ASA and PRA by soy isoflavones. Moreover, the expression of estrogen receptors (ERs) was up regulated in DSA, and down regulated in ASA and PRA by soy isoflavones. Our results suggest that soy isoflavones affected the lipid metabolism in white adipose tissues of Bama mini-pigs in a site-specific manner, which might be mediated through PPARs and ERs regulated gene expression.