Gene expression of GnRH, kisspeptin, neuropeptide Y and receptors for estrogen and leptin in the hypothalamus of suckled and weaned beef cows

M.S.S. Ainu Husna, T. Flatscher-Bader, S.A. Lehnert, A. Reverter, E.K. Chan, N.J. Phillips, M. McGowan and M.J. D’Occhio

Abstract
The aim of this study was to ascertain the expression of multiple genes in the hypothalamic sub-regions of postpartum beef cows that were suckled or weaned, and had different ovarian phenotypes. Genes studied were gonadotrophinreleasing hormone (GNRH1), kisspeptin (KISS1), estrogen receptor-α (ESR1), leptin receptor (LEPR) and neuropeptide Y (NPY) in two hypothalamic subregions, H1 (anterior) and H2 (ventral posterior). The expression of GNRH1 was around 7-fold greater (p <0.01) within H1 than H2 while the expression of KISS1 was around 20-fold greater (p <0.01) within H2 than H1. Both ESR1 and NPY showed greater (p <0.05) expression within H2 than H1. Weaned cows had lower (p <0.05) expression of ESR1, LEPR and NPY than suckled cows in H1. Cows with suppressed follicle growth (follicles 4 – 5 mm) had greater (p <0.05) LEPR expression within H1 compared to cows with active follicle growth (follicles 10 mm) and cows that had ovulated. This is the first report of KISS1 expression in the bovine brain and also of regional differences in the expression of multiple genes within the bovine hypothalamus. The study on simultaneous gene expression within the hypothalamus provides a new approach in understanding the complex gene networks linked to the effects of nutrition, lactation, ovarian steroids, metabolic homeostasis and maternal bonding on central mechanisms associated with postpartum reproduction in bovine.

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