Energy balance affects pulsatile secretion of luteinizing hormone from the adenohypophesis and expression of neurokinin B in the hypothalamus of ovariectomized gilts

Authors: THORSON, JENNIFER - Montana State University; PREZOTTO, LIGIA - Montana State University; ADAMS, HILLARY - University Of Massachusetts; PETERSEN, SANDRA - University Of Massachusetts; CLAPPER, JEFFREY - South Dakota State University; Wright, Elane; Oliver, William; Freking, Bradley - Brad; Foote, Andrew; Berry, Elaine; Nonneman, Danny - Dan; Lents, Clay

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2018
Publication Date: 8/1/2018
Citation: Thorson, J.F., Prezotto, L.D., Adams, H., Petersen, S.L., Clapper, J.A., Wright, E.C., Oliver, W.T., Freking, B.A., Foote, A.P., Berry, E.D., Nonneman, D.J., Lents, C.A. 2018. Energy balance affects pulsatile secretion of luteinizing hormone from the adenohypophesis and expression of neurokinin B in the hypothalamus of ovariectomized gilts. Biology of Reproduction. 99(2):433-445. https://doi.org/10.1093/biolre/ioy069.
DOI: https://doi.org/10.1093/biolre/ioy069

Interpretive Summary: Puberty, brought about by changes in secretion of luteinizing hormone (LH), is metabolically gated in the pig. There is little information about the mechanisms through which nutrition brings about the timing of this relationship for the proper activation of the reproductive axis in pigs. ARS scientists found that kisspeptin, a factor in the hypothalamus of the central nervous system, can affect secretion of LH in young female pigs called gilts. Researchers looked to see if kisspeptin is expressed differently in gilts fed different levels of nutrition, which can cause changes in secretion of LH. Although no differences were seen in the expression of kisspeptin, researchers discovered that nutrition altered the expression of another hypothalamic factor called neurokinin B. This is important because neurokinin B has been implicated in regulating the release of kisspeptin in laboratory animals. Researchers are focused on understanding how expression and release of kisspeptin and neurokinin B regulate reproductive function in pigs, which will facilitate the development of management strategies to optimize feeding and growth of gilts. This is important because gilts that reach puberty at a younger age have a longer and more productive life.

Technical Abstract: The pubertal transition of gonadotropin secretion in pigs is metabolically gated. Kisspeptin (KISS1) and neurokinin B (NKB) are coexpressed in neurons within the arcuate nucleus of the hypothalamus (ARC) and are thought to play an important role in the integration of nutrition and metabolic state with the reproductive neuroendocrine axis. The hypothesis that circulating concentrations of luteinizing hormone (LH) and expression of KISS1 and tachykinin 3(TAC3, encodes NKB) in the ARC of female pigs are reduced with negative energy balance was tested using ovariectomized, prepubertal gilts fed to either gain or lose body weight. Restricted feeding of ovariectomized gilts caused a rapid and sustained metabolic response characterized by reduced concentrations of plasma urea nitrogen, insulin, leptin, and insulin-like growth factor-1 and elevated concentrations of free fatty acids. The secretory pattern of LH shifted from one of low amplitude to one of high amplitude, which caused overall circulating concentrations of LH to be greater in restricted gilts. Nutrient-restricted gilts had greater expression of follicle-stimulating hormone and gonadotropinreleasing hormone receptor, but not LH in the anterior pituitary gland. Expression of KISS1 in the ARC was not affected by dietary treatment, but expression of TAC3 was greater in restricted gilts. These data are consistent with the idea that hypothalamic expression of KISS1 is correlated with the number of LH pulse in pig, and further indicate that amplitude of LH pulses may be regulated by NKB in the gilt.