Physiological and genomic insight into neuroendocrine regulation of puberty in gilts

Authors: Lents, Clay; LINDO, A - West Virginia University; HILEMAN, S - West Virginia University; Nonneman, Danny - Dan

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2020
Publication Date: 10/1/2020
Citation: Lents, C.A., Lindo, A.N., Hileman, S.M., Nonneman, D.J. 2020. Physiological and genomic insight into neuroendocrine regulation of puberty in gilts. Domestic Animal Endocrinology. 73. Article 106446. https://doi.org/10.1016/j.domaniend.2020.106446.
DOI: https://doi.org/10.1016/j.domaniend.2020.106446

Interpretive Summary: Attainment of puberty in replacement females (gilts) is critical for successful swine production and failure of gilts to become pubertal is a management challenge in pork production. Complex developmental changes in the hypothalamic-pituitary-ovarian (HPG) axis are necessary for puberty to occur. There is a concomitant decrease of inhibitory signals and increase of stimulatory signals in the brain that coordinates release of reproductive hormones that trigger puberty. Puberty in the pig is metabolically gated, and metabolites and metabolic hormones such as leptin have profound effects on these regulatory mechanisms. Puberty is a heritable genetic trait and genetic association studies have identified many genomic regions related to puberty in pigs. These genomic regions contain genes regulating growth, adiposity, and function of the HPG axis, which underscores the relationship of body composition with reproductive cycles. Some of these genes have also been associated with control of puberty in humans. Summary of the current state of knowledge about these physiological and genomic mechanisms related is important to identify new solutions to manage pubertal development of gilts in commercial swine production.

Technical Abstract: The timing of pubertal attainment in gilts is a critical factor for pork production and is an early indicator of future reproductive potential. Puberty, defined as age at first standing estrus in the presence of a boar, is brought about by an escape from estrogen inhibition of the GnRH pulse generator, which allows for increasing LH pulses leading to the onset of cyclicity. The biological mechanisms that control the timing of these events is related to decreasing inhibitory signals with a concomitant increase in stimulatory signals within the hypothalamus. The roles of gamma-aminobutyric acid, endogenous opioid peptides, and gonadotropin-inhibitory hormone in negatively regulating gonadotropin secretion in gilts is explored. Developmental changes in stimulatory mechanisms of glutamatergic and kisspeptin neurons are important for increased LH pulsatility required for the occurrence of puberty in pigs. Age at first estrus of gilts is metabolically gated, and numerous metabolites, metabolic hormones, and appetite-regulating neurotransmitters have been implicated in the nutritional regulation of gonadotropin secretion. Leptin is an important metabolic signal linking body energy reserves with age at puberty in gilts. Leptin acting through neuropeptide Y and proopiomelanocortin neurons in the hypothalamus has important impacts on the function of the reproductive neurosecretory axis of gilts. Age at puberty in swine is heritable, and genomic analyses reveal it to be a polygenic trait. Genome-wide association studies for pubertal age in gilts have revealed several genomic regions in common with those identified for age at menarche in humans.Candidate genes have been identified that have important functions in growth and adiposity. Numerous genes regulating hypothalamic neuronal function, gonadotropes in the adenohypophysis, and ovarian follicular development have been identified and illustrate the complex maturational changes occurring in the hypothalamic–pituitary–ovarian axis during puberty in gilts.