Hypothalamic–Pituitary–Thyroid Axis Crosstalk With the Hypothalamic–Pituitary–Gonadal Axis and Metabolic Regulation in the Eurasian Tree Sparrow During Mating and Non-mating Periods

Abstract

Reproduction is an energetically costly phenomenon. Therefore, to optimize reproductive success, male birds invest enough energetic resources for maintaining well-developed testes. The hypothalamic-pituitary-thyroid (HPT) axis in birds can crosstalk with the hypothalamic-pituitary-gonadal (HPG) axis, thus orchestrating both the reproduction and metabolism. However, until now, how the free-living birds timely optimize both the energy metabolism and reproduction via HPT-axis is not understood. To uncover this physiological mechanism, we investigated the relationships among body mass, testis size, plasma hormones including thyroid-stimulating hormone (TSH), thyroxine (T 4), triiodothyronine (T 3), metabolites including glucose (Glu), triglyceride (TG), total cholesterol (TC), uric acid (UA), diencephalon mRNA expressions of type 2 (Dio2) and 3 (Dio3) iodothyronine deiodinase enzymes, thyrotropin-releasing hormone (TRH), thyroid-stimulating hormone (TSH), gonadotropin-releasing hormone I (GnRH-I), and gonadotropin-inhibitory hormone (GnIH) in a male Eurasian tree sparrow (ETS, Passer montanus). We found significantly larger testis size; elevated diencephalon Dio2 and TRH mRNA expressions, plasma T 3 , and UA levels; and significantly lowered Glu, TG, and TC levels during mating relative to the non-mating stages in male ETSs. However, Dio3, TSH, GnRH-I, and GnIH mRNA expression did not vary with the stage. Furthermore, life-history stage dependent variation in plasma T 3 had both direct effects on the available energy substrates and indirect effects on body mass and testis size, indicating a complex regulation of metabolic pathways through the HPT-and HPG-axes. The identified differences and relationships in mRNA expression, plasma T 3 and metabolites, and testis size in male ETSs contribute to our understanding how free-living birds adjust their molecular, endocrinal, and biochemical features to orchestrate their reproductive physiology and metabolism for the maintenance of well-developed testes.

A microscale 3D organ on a chip for recapitulating reciprocal neuroendocrine crosstalk between the hypothalamus and the pituitary gland

“…This in turn acts on the pituitary gland to stimulate secretion of two gonadotropins [follicle-stimulating hormone (FSH) and luteinizing hormone (LH)], which then stimulate folliculogenesis in female ovary [4] and spermatogenesis in male testis. Therefore, neuroendocrine crosstalk between the hypothalamus and the pituitary gland plays a key role in orchestrating both reproduction and development by controlling various endocrine systems [5]. Traditionally, single cell-based 2D in vitro culture models for HP axis have been widely used for physiological investigations and drug discoveries [6][7][8].…”

Effect of immunization against OPN5 on the reproductive performance in Shan Partridge ducks under different photoperiods

“…Reproduction in avian species is controlled by the hypothalamic-pituitary-gonadal axis ( HPGA ), and the HPGA is a comprehensive feedback system formed under central nervous regulation ( Rose et al, 2022 ). HPGA is a process in which the hypothalamus secretes GnRH and GnIH to regulate the secretion of gonadotropic hormones at the pituitary level ( Nabi et al, 2020 ), and gonadotropins regulate the secretion of gonadotropic hormones through blood circulation, which in turn promotes gonadal development and regulate animal reproduction. Due to positive and negative feedback, the dynamic balance of reproductive hormones associated with the HPGA in vivo is maintained and is essential for animal reproductive development.…”

OPN5 Regulating Mechanism of Follicle Development Through the TSH-DIO2/DIO3 Pathway in Mountain Ducks Under Different Photoperiods

“…Reproduction in birds is regulated by the hypothalamic-pituitary-gonadal axis, and the HPG axis is a complete feedback system formed by the hypothalamus, pituitary, and gonads under central nervous regulation ( Rose et al, 2022 ). Hypothalamus secretes GnRH and Gonadotropin-inhibitory hormone (GnIH) to regulate gonadotropin secretion at the pituitary level ( Nabi et al, 2020 ). Gonadotropins regulate the secretion of gonadotropic hormones through blood circulation, which in turn promotes gonadal development and regulates animal reproduction ( Zhu et al, 2019a ; Zhu et al, 2019b ).…”