Rumen-protected glucose stimulates the secretion of reproductive hormones and the mTOR/AKT signaling pathway in the ovaries of early postpartum

This study was conducted to determine the response of the reproductive hormones and the mTOR/AKT pathway in the ovaries of post-partum dairy cows with the dietary rumen-protected glucose (RPG) supplementation. Twelve Holstein cows were randomly assigned to two groups (n = 6 / group): control group (CT) and RPG group. Cows were fed with the diets from 1 week prepartum to 2 weeks postpartum, and euthanized on d 22 postpartum. Blood samples were collected from cows in each group on d 1, 7 and 14 after calving. The plasma hormones were determined using a bovine specific enzyme linked immimosorbent assay method. The gene expressions of the reproductive hormone receptors and mTOR/AKT pathway in the ovarian tissues were detected using real-time polymerase chain reaction, Western blot, and immunohistochemistry, respectively. The results showed that the RPG addition significantly increased the plasma LH, E2, and P4 concentrations on d14 after calving. The mRNA and protein expressions of the estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), 17β-hydroxysteroid dehydrogenase (17β-HSD), FSHR, LHR and cytochrome p450 (CYP17A1) were upregulated, while the mRNA and protein expression of steroidogenic acute regulatory protein (StAR) was downregulated in cows of the RPG group compared with the CT group. Immunohistochemical analysis identified higher expressions of the FSHR and LHR in the ovaries of RPG-fed cows versus CT cows. Furthermore, the ratios of the protein expressions of p-AKT to total AKT and p-mTOR to total mTOR ratio were significantly increased in the ovaries of RPG-fed cows compared with the CT group cows. The current results indicated that dietary RPG supplementation regulated the secretion of gonadal hormones, and stimulated the expressions of hormone receptors and the mTOR/AKT pathway in the ovaries of early postpartum dairy cows, and might beneficial for ovarian activity recovery in the post-calving dairy cows.