Gene expression of adiponectin and its receptors in hypothalamus and pituitary of Holstein cattle during the estrous cycle

BACKGROUND: Adiponectin is one of the most important adipocytokines that regulate male and female fertility via AdipoR1 and AdipoR2 receptors. Recently expression of adiponectin system and its negative regulatory role on hypothalamus-pituitary axis have been confirmed. Objectives: No information is available about the expression pattern of adiponectin and its receptors in hypothalamus-pituitary axis in domestic animals. Here for the first time, we studied hypothalamus-pituitary adiponectin system gene expression in different stages of bovine estrous cycle. Methods: Anterior pituitary and hypothalamus were collected from Holstein cow at the local abattoir. The estrous cycle was classified to four phases (proestrous, metstrous, early luteal and late luteal) based on macroscopic examination of ovaries and uteri. Gene expression analysis of adiponectin and its receptors was done using quantitative real time PCR (qPCR Probe MasteKit) and according to the comparative 2-ΔΔCt method. E2 and P4 levels were measured using ELISA method. Results: Our results demonstrated that adiponectin and its two receptors were expressed in pituitary and hypothalamus of cyclic cow. Maximal expression of adiponectin was observed in early luteal phase, while it was expressed at minimal level during the proestrous stage. We observed no significant changes in the expression of AdipoR1 in both tissues at different stages of estrous cycle. The highest expression of AdipoRII in both tissues was detected during the proestrous stage, while it expressed at minimal level during the late luteal phase. E2 and P4 had respectively negative and positive correlations with adiponectin expression levels in hypothalamus and pituitary. Conclusions: Based on our results that demonstrated adiponectin was minimally expressed at proestrous stage and other data about the negative action of adiponectin on LH secretion from pituitary, we concluded that adiponectin may has role in the hormonal function of this axis during the estrous cycle.