Fan J, Zhang B, Li L, Xiao C, Oladele OA, Jiang G, Ding H, Wang S, Xing Y, Xiao D, Yin Y.

Asian-Australas J Anim Sci. 2015 Nov;28(11):1573-1582.

http://www.ncbi.nlm.nih.gov/pubmed/26580281

Abstract

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 (3β-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.

Figure 1

Effects of soyabean isoflavones (SIF) on the expression of genes in the hypothalamus of the mini-pigs. Pigs were exposed to varing dosages (0, 250, 500, and 1,250 mg/kg) of SIF and estradiol valerate (EV; 0.66 mg/kg). The hypothalamus samples (n = 6 per treatment) from each pig was separated and frozen in liquid N, and then stored at −80°C. Gene expression were analyzed by RT-PCR. Data were presented as mean±standard error of the mean.