General and comparative endocrinology最新文献

The present study was aimed at gaining insight into the signalling relationship between glucagon-like peptide-1 (GLP-1) and its receptor (GLP-1R) in the regulation of glucose metabolism. Further, to assess the role of G-protein-coupled receptor 40 (GPR40) and insulin receptor (INSR) in the pancreas of sheep that were supplemented with calcium salts of long-chain fatty acids (CSFAs). An experiment was carried out over a period of 60 days with eighteen sheep, and they were fed with a standard basal diet. The sheep were divided into three groups: CSFA0 (without CSFAs), while CSFA3 and CSFA5 were supplemented with 3 % and 5 % of CSFAs, respectively. Plasma concentrations of GLP-1, insulin, glucagon, and glucose were assessed every two weeks. At the end of the experiment, sheep were slaughtered, and samples of gastrointestinal tract (GIT) epithelial tissues and pancreas were collected to assess the relative expression of mRNA of GPR40, GLP-1R, and INSR. Postprandial GLP-1 and insulin were increased by 3.7–4.1 and 1.45–1.5 times, respectively, in the CSFAs-supplemented groups compared to CSFA0. Post-feeding, glucagon and glucose levels decreased in CSFA3 and CSFA5 compared to CSFA0. The results indicated that the supplementation of LCFAs increased the expression of GLP-1R in the GIT and pancreas, as well as the mRNA of GPR40 and INSR in the pancreas. Chemosensing of LCFAs by GPR40 in the pancreas triggers signalling transduction, and enhanced GLP-1 and GLP-1R resulted in moderately increased insulin secretion and reduced glucagon levels. These combined effects, along with the glucose-lowering effect of GLP-1, effectively lowered glucose levels in normoglycemic sheep.

Sexual dimorphism in plumage is widespread among avian species. In chickens, adult females exhibit countershading, characterized by dull-colored round feathers lacking fringe on the saddle, while adult males display vibrant plumage with deeply fringed bright feathers. This dimorphism is estrogen-dependent, and administering estrogen to males transforms their showy plumage into cryptic female-like plumage. Extensive studies have shown that estrogen’s role in female plumage formation requires thyroid hormone; however, the precise mechanisms of their interaction remain unclear. In this study, we investigated the roles of estrogen and thyroid hormone in creating sexual dimorphism in the structure and coloration of saddle feathers by administering each hormone to adult males and observing the resulting changes in regenerated feathers induced by plucking. RT-PCR analysis revealed that the expression of type 3 deiodinase (DIO3), responsible for thyroid hormone inactivation, correlates with fringing. Estrogen suppressed DIO3 and agouti signaling protein (ASIP) expression while stimulating BlSK1, a marker of barbule cells, resulting in female-like feathers with mottled patterns and lacking fringes. Administration of thyroxine (T4) stimulated BlSK1 and proopiomelanocortin (POMC) expression, with no effect on ASIP, leading to the formation of solid black feathers lacking fringes. Triiodothyronine (T3) significantly increased POMC expression in pulp cells in culture. Taken together, these findings suggest that estrogen promotes the formation of solid vanes by suppressing DIO3 expression, while also inducing the formation of mottled patterns through inhibition of ASIP expression and indirect stimulation of melanocortin expression via changes in local T3 concentration. This is the first report describing molecular mechanism underlying hormonal crosstalk in creating sexual dimorphism in feathers.

Knowledge on hormonal regulation of reproductive cycles in viperid snakes is still incipient, especially when it comes to females and tropical species. There is an urgent need to understand the reproduction of venomous snakes to improve assisted reproduction techniques and optimize the maintenance of these animals in captivity. With this in mind, we monitored Northern pit viper females year-round throughout different seasons via serum levels of progesterone (P₄) and estradiol (E₂) in conjunction with ultrasound examinations. Ovarian follicles were classified according to their size and stage of vitellogenesis in F-I and F-II (non-vitellogenic phase) or in F-III and F-IV (vitellogenic phase). During autumn and winter, five adult males were rotated among these females for reproductive pairing, which resulted in 17 copulations and 2 pregnancies in the first year and 12 copulations and 5 pregnancies in the second year. Then, we assessed changes in P4 and E2 levels according to seasons, predominant ovarian structures and the presence of embryos or eggs in the oviduct. Our findings showed high levels of E₂ when a greater number of vitellogenic follicles were detected, indicating a possible influence of E₂ on vitellogenesis and higher levels of P₄ whenever eggs and embryos were visualized in the oviduct, implying its role in maintaining pregnancy. Descriptive analysis of the vipers’ ovarian cycles revealed a greater number of vitellogenic follicles during winter, probably as a result of increases in E₂; whereas pregnancies occurred predominantly in spring, under the influence of P4. The use of ultrasound images, as a minimally invasive methodology, associated with serum steroid levels has proven to be an efficient approach in the reproductive monitoring of Northern pit vipers in vivo. In addition, these data suggest that female pit vipers under human care display a seasonal reproductive cycle, despite earlier studies involving captive males of the species indicating a lack of seasonality in sperm production and quality.

Environmental cues such as temperature induce macroscopic changes in the molting cycle of crustaceans, however, the physiological mechanisms behind these changes remain unclearWe aimed to investigate the regulatory mechanisms in the intermolt and premolt stages of the Callinectes sapidus molt cycle in response to thermal stimuli. The concentration of ecdysteroids and lipids in the hemolymph, and the expression of heat shock proteins (HSPs) and molt key genes were assessed at 19 °C, 24 °C and 29 °C. The premolt animals exhibited a much larger response to the colder temperature than intermolt animals. Ecdysteroids decreased drastically in premolt animals, whereas the expression of their hepatopancreas receptor (CasEcR) increased, possibly compensating for the low hemolymphatic levels at 19 °C. This decrease might be due to increased HSPs and inhibited ecdysteroidogenesis in the Y-organ. In addition, the molting-inhibiting hormone expression in the X-organ/sinus gland (XO/SG) remained constant between temperatures and stages, suggesting it is constitutive in this species. Lipid concentration in the hemolymph, and the expression of CasEcR and CasHSP90 in the XO/SG were influenced by the molting stage, not temperature. On the other hand, the expression of HSPs in the hepatopancreas is the result of the interaction between the two factors evaluated in the study. Our results demonstrated that temperature is an effective modulator of responses related to the molting cycle at the endocrine level and that temperature below the control condition caused a greater effect on the evaluated responses compared to the thermostable condition, especially when the animal was in the premolt stage.

Neuropeptides are essential neuronal signaling molecules that orchestrate animal behavior and physiology via actions within the nervous system and on peripheral tissues. Due to the small size of biologically active mature peptides, their identification on a proteome-wide scale poses a significant challenge using existing bioinformatics tools like BLAST. To address this, we have developed NeuroPeptide-HMMer (NP-HMMer), a hidden Markov model (HMM)-based tool to facilitate neuropeptide discovery, especially in underexplored invertebrates. NP-HMMer utilizes manually curated HMMs for 46 neuropeptide families, enabling rapid and accurate identification of neuropeptides. Validation of NP-HMMer on Drosophila melanogaster, Daphnia pulex, Tribolium castaneum and Tenebrio molitor demonstrated its effectiveness in identifying known neuropeptides across diverse arthropods. Additionally, we showcase the utility of NP-HMMer by discovering novel neuropeptides in Priapulida and Rotifera, identifying 22 and 19 new peptides, respectively. This tool represents a significant advancement in neuropeptide research, offering a robust method for annotating neuropeptides across diverse proteomes and providing insights into the evolutionary conservation of neuropeptide signaling pathways.

Immunosenescence corresponds to the progressive decline of immune functions with increasing age. Although it is critical to understand what modulates such a decline, the ecological and physiological drivers of immunosenescence remain poorly understood in the wild. Among them, the level of glucocorticoids (GCs) during early life are good candidates to modulate immunosenescence patterns because these hormones can have long-term consequences on individual physiology. Indeed, GCs act as regulators of energy allocation to ensure allostasis, are part of the stress response triggered by unpredictable events and have immunosuppressive effects when chronically elevated. We used longitudinal data collected over two decades in two populations of roe deer (Capreolus capreolus) to test whether higher baseline GC levels measured within the first year of life were associated with a more pronounced immunosenescence and parasite susceptibility. We first assessed immunosenescence trajectories in these populations facing contrasting environmental conditions. Then, we found that juvenile GC levels can modulate lymphocyte trajectory. Lymphocyte depletion was accelerated late in life when GCs were elevated early in life. Although the exact mechanism remains to be elucidated, it could involve a role of GCs on thymic characteristics. In addition, elevated GC levels in juveniles were associated with a higher abundance of lung parasites during adulthood for individuals born during bad years, suggesting short-term negative effects of GCs on juvenile immunity, having in turn long-lasting consequences on adult parasite load, depending on juvenile environmental conditions. These findings offer promising research directions in assessing the carry-over consequences of GCs on life-history traits in the wild.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) control antral follicular growth by regulating several processes, such as the synthesis of hormones and signaling molecules, proliferation, survival, apoptosis, luteinization, and ovulation. To exert these effects, gonadotropins bind to their respective G_s protein-coupled receptors, activating the protein kinase A (PKA) pathway or recruiting G_q proteins to activate protein kinase C (PKC) signaling. Although the action mechanism of FSH and LH is clear, recently, it has been shown that both gonadotropins promote the synthesis of sphingosine-1-phosphate (S1P) in granulosa and theca cells through the activation of sphingosine kinase 1. Moreover, the inhibition of SPHKs reduces S1P synthesis, cell viability, and the proliferation of follicular cells in response to gonadotropins, and the addition of S1P to the culture medium increases the proliferation of granulosa and theca cells without apparent effects on sexual steroid synthesis. Therefore, we consider that S1P is a crucial signaling molecule that complements the canonical gonadotropin pathway to promote the proliferation and viability of granulosa and theca cells.

In recent years, new concepts have emerged regarding the nomenclature, functions, and relationships of different peptide families of the gonadotropin-releasing hormone (GnRH) superfamily. One of the main driving forces for this originated from the emerging evidence that neuropeptides previously called molluscan GnRH are multifunctional and should be classified as corazonin (CRZ). However, research articles still appear that use incorrect nomenclature and attribute the same function to molluscan CRZs as vertebrate GnRHs. The aim of the present study was to further support the recent interpretation of the origin and function of the GnRH superfamily. Towards this goal, we report the characterization of CRZ signaling system in the molluscan model species, the great pond snail (Lymnaea stagnalis). We detected a CRZ-receptor-like sequence (Lym-CRZR) by homology-searching in the Lymnaea transcriptomes and the deduced amino acid sequence showed high sequence similarity to GnRH receptors and CRZ receptors. Molecular phylogenetic tree analysis demonstrated that Lym-CRZR is included in the cluster of molluscan CRZRs. Lym-CRZR transiently transfected into HEK293 cells was found to be localized at the plasma membrane, confirming that it functions as a membrane receptor, like other G protein-coupled receptors. The signaling assays revealed that the previously identified Lym-CRZ neuropeptide stimulated intracellular Ca²⁺ mobilization in a dose-dependent manner, but not cyclic AMP production, in HEK293 cells transfected with Lym-CRZR. Finally, we demonstrated a wide tissue distribution of Lym-CRZR. These results suggest that Lym-CRZ is a multifunctional peptide and provide further insights into the evolution of the GnRH neuropeptide superfamily. The present study also supports the notion that previously termed molluscan “GnRH” should be classified as “CRZ”.