Avian corticosteroid-binding globulin: biological function and regulatory mechanisms in physiological stress responses

Effect of a Territorial Challenge on the Steroid Profile of a Juvenile Songbird

Aggression is a social behavior that is critical for survival and reproduction. In adults, circulating gonadal hormones, such as androgens, act on neural circuits to modulate aggressive interactions, especially in reproductive contexts. In many species, individuals also demonstrate aggression before reaching gonadal maturation. Adult male song sparrows, Melospiza melodia, breed seasonally but maintain territories year-round. Juvenile (hatch-year) males aggressively compete for territory ownership during their first winter when circulating testosterone is low. Here, we characterized the relationship between the steroid milieu and aggressive behavior in free-living juvenile male song sparrows in winter. We investigated the effect of a 10 min simulated territorial intrusion (STI) on behavior and steroid levels in blood, 10 microdissected brain regions, and four peripheral tissues (liver, pectoral muscle, adrenal glands, and testes). Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we quantified 12 steroids: pregnenolone, progesterone, corticosterone, 11-dehydrocorticosterone, dehydroepiandrosterone, androstenedione, testosterone, 5α-dihydrotestosterone, 17β-estradiol, 17α-estradiol, estrone, and estriol. We found that juvenile males are robustly aggressive, like adult males. An STI increases progesterone and corticosterone levels in blood and brain and increases 11-dehydrocorticosterone levels in blood only. Pregnenolone, androgens, and estrogens are generally non-detectable and are not affected by an STI. In peripheral tissues, steroid concentrations are very high in the adrenals. These data suggest that adrenal steroids, such as progesterone and corticosterone, might promote juvenile aggression and that juvenile and adult songbirds might rely on distinct neuroendocrine mechanisms to support similar aggressive behaviors.

Does contaminant exposure disrupt maternal hormones deposition? A study on per- and polyfluoroalkyl substances in an Arctic seabird

Maternal effects are thought to be essential tools for females to modulate offspring development. The selective deposition of avian maternal hormones could therefore allow females to strategically adjust the phenotype of their offspring to the environmental situation encountered. However, at the time of egg formation, several contaminants are also transferred to the egg, including per- and polyfluoroalkyl substances (PFAS) which are ubiquitous organic contaminants with endocrine disrupting properties. It is, however, unknown if they can disrupt maternal hormone deposition. In this study we explored relationships between female PFAS burden and maternal deposition in the eggs of steroids (dihydrotestosterone, androstenedione and testosterone), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine and thyroxine) in a population of the Arctic-breeding black-legged kittiwake (Rissa tridactyla). Egg yolk hormone levels were unrelated to female hormone plasma levels. Second-laid eggs had significantly lower concentrations of androstenedione than first-laid eggs. Triiodothyronine yolk levels were decreasing with increasing egg mass but increasing with increasing females' body condition. Testosterone was the only transferred yolk hormone correlated to maternal PFAS burden: specifically, we found a positive correlation between testosterone in yolks and circulating maternal perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDcA) and perfluoroundecanoic acid (PFUnA) in first-laid eggs. This correlative study provides a first insight into the potential of some long-chain perfluoroalkyl acids to disrupt maternal hormones deposition in eggs and raises the question about the consequences of increased testosterone deposition on the developing embryo.

Comparative Analysis of the Temporal Impacts of Corticosterone and Simulated Production Stressors on the Metabolome of Broiler Chickens

The impact of physiological stress on the metabolome of breast muscle, liver, kidney, and hippocampus was investigated in Ross 308 broiler chicks. Simulated on-farm stressors were compared to a corticosterone model of physiological stress. The three different stressors investigated were: (i) corticosterone at a dose of 15 mg/kg of feed; (ii) heat treatment of 36 °C and 40% RH for 8 h per day; and (iii) isolation for 1 h per day. Liver, kidney, breast muscle, and hippocampus samples were taken after 2, 4, 6, and 8 days of stress treatment, and subjected to untargeted ¹H-nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis to provide insights on how stress can modulate metabolite profiles and biomarker discovery. Many of the metabolites that were significantly altered in tissues were amino acids, with glycine and alanine showing promise as candidate biomarkers of stress. Corticosterone was shown to significantly alter alanine, aspartate, and glutamate metabolism in the liver, breast, and hippocampus, while isolation altered the same pathways, but only in the kidneys and hippocampus. Isolation also significantly altered the glycine, serine, and threonine metabolism pathway in the liver and breast, while the same pathway was significantly altered by heat in the liver, kidneys, and hippocampus. The study's findings support corticosterone as a model of stress. Moreover, a number of potential metabolite biomarkers were identified in chicken tissues, which may allow producers to effectively monitor stress and to objectively develop and evaluate on-farm mitigations, including practices that reduce stress and enhance bird health.

First Evidence Indicates the Physiology- and Axial-Myopia-Dependent Profiles of Steroid Hormones in Aqueous Humor

The quantitative level of steroid hormones (SHs) in some body fluids have been accepted for clinical diagnosis, whereas their distribution in aqueous humor (AH) is unknown yet. Herein, a profiling study was conducted with a total of 171 AH and 107 plasma samples using liquid chromatography coupled with tandem mass spectrometry (LC MS/MS). For the first time, six kinds of SHs in AH were quantitatively estimated, and their abundances were ranked at cortisol (F), corticosterone (COR), androstenedione (A2), and 11-deoxycortisol (11DOC). The corresponding abundance of all SHs in AH was significantly lower than those in plasma, while there was a lack of a proportional relationship with the abundance of plasma SHs. Dehydroepiandrosterone sulfate, the most abundant plasma SH, was undetectable in AH, implying that the blood-aqueous barrier might specifically block its transferral. Axial myopia generally results from many factors throughout the entire eye from tissues and molecules; furthermore, the correlation of AH SHs and axial myopia was assessed to look for their indication in such myopia. The panel with five kinds of AH SHs (F, COR, CORT, ALD and A2) was functional as a discriminator for axial myopia and control. The abundance of SHs, therefore, has a specific distribution in AH and can potentially contribute to axial myopia.