Endocrinology最新文献

Serotonin neurons are thought to exert a modulatory influence on the secretion of the gonadotropin hormones in mammals, but their mechanism of action remains unclear. We examined here the potential role of serotonin neurons in modulating the activity of the gonadotropin-releasing hormone (GnRH) pulse generator formed by the arcuate nucleus kisspeptin (ARNKISS) neurons. Acute brain slice electrophysiology revealed that ∼60% of ARNKISS neurons in diestrous female mice were activated by serotonin while less than 10% were inhibited. Pharmacological studies indicated that combinatorial patterns of 5-HT receptor subtype activation were likely responsible for the excitatory actions. The role of serotonin in ARNKISS neuron synchronization behavior was assessed using GCaMP imaging in acute brain slices from diestrous female and male mice. In both sexes, serotonin-evoked potent recurring bouts of synchronization activity amongst ARNKISS neurons. To evaluate the impact of serotonin in vivo, we used "fluidic" GCaMP fiber photometry in which serotonin was infused directly into the ARN while recording the ARNKISS neuron population activity in freely behaving diestrous female mice. In all cases, the infusion of serotonin evoked a robust ARNKISS neuron synchronization episode. These data demonstrate that serotonin exerts a direct, predominantly stimulatory action on ARNKISS neuron pulse generator through a variety of 5-HT receptors. Serotonergic inputs appear to provide a potent synchronizing influence on the ARNKISS neuron population and suggest considerable potential for 5-HT to control the frequency of pulsatile reproductive hormone secretion in mice and likely other mammals.

Activin-class ligands of the transforming growth factor β family induce follicle-stimulating hormone (FSH) production by pituitary gonadotrope cells in mice via the actions of the transcription factors SMAD3, SMAD4, and FOXL2, which bind to cis-elements in the FSHβ subunit (Fshb) promoter. An enhancer region for murine Fshb transcription was identified in vitro. However, deletion of the region using CRISPR-Cas9 did not affect FSH synthesis or secretion in mice. Using single-nucleus ATAC-seq of whole murine pituitaries, we identified 3 additional open chromatin regions upstream of Fshb exclusively in gonadotropes. These regions, as well as the Fshb gene, were fully or partially closed in gonadotropes of FSH-deficient mice with genetically or pharmacologically inactivated activin type II receptors. The initially characterized enhancer region did not significantly alter basal or activin-stimulated murine Fshb promoter-reporter activity in homologous LβT2 cells. In contrast, the other 3 open chromatin regions enhanced basal and activin A-stimulated Fshb promoter-reporter activity in LβT2 cells, with the 2 most distal showing the greatest effects. These 2 regions were open, exhibited enrichment of the enhancer mark H3K27ac, and were bound by SMAD2/3 and FOXL2 in response to activin A in LβT2 cells. The most distal enhancer exhibited strong FOXL2 and weak SMAD4 binding in gel shift assays. SMAD4, but not FOXL2, directly bound the other distal enhancer. Mutation of defined FOXL2 and SMAD4 cis-elements diminished enhancer activity in reporter assays in LβT2 cells. Collectively, the data indicate that there may be as many as 4 activin-sensitive enhancers upstream of murine Fshb.

Cancers of the breast and prostate are one of the leading causes of cancer deaths in women and men, respectively. Although several treatment options have been developed to transform these cancers into manageable chronic diseases, they still contribute to over 70 000 deaths each year in the United States. Though majority of these cancers belong to slow growing differentiated subtypes, the cancers evolve over time due to treatment-related pressure into aggressive treatment-resistant types. A mechanism attributed to the transformation of hormonal and other cancers into aggressive treatment-refractory cancers is "lineage plasticity," a term used to describe a switch in the cell type or lineage. Evolving evidences suggest that the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a key role in driving lineage plasticity. This review discusses the role of JAK-STAT signaling pathway in hormonal cancers' evolution into aggressive cancers and in treatment resistance, with focus on treatment-induced lineage plasticity.

The transcription of the Hairless gene (Hr), which encodes a histone demethylase, is strongly induced by thyroid hormone (T3) in many cell types. This is mediated by heterodimers formed between T3 nuclear receptors (TRs) and retinoid X receptors (RXRs). These heterodimers are bound to specific DNA response elements present in regulatory sequences and activate transcription upon T3 binding. To address the significance of this regulation, we identified a single DNA response element upstream of the Hr transcription start site, which plays a key role in this regulation. A single nucleotide mutation in this DNA response element, which prevents the binding of heterodimers, was shown to prevent the activation of Hr by T3 signaling in mice. Analysis of gene expression in the heart and striatum of mice homozygous for this mutation highlights the influence of the Hairless cofactor on thyroid hormone signaling.

Acute pharmacological administration of the endocrine hormone fibroblast growth factor 21 (FGF21) enhances insulin sensitivity. This acute insulin-sensitizing effect of FGF21 is mediated through direct signaling to brown adipose tissues. Since skeletal muscle is an important site of insulin-stimulated glucose intake and shares a common progenitor cell with brown adipocytes, we examined whether the beneficial effects of FGF21 administration could be enhanced by making skeletal muscle a FGF21-responsive target tissue. This was accomplished by ectopically expressing the FGF21 co-receptor, β-klotho, in skeletal muscle. Here, we demonstrate that under normal conditions, FGF21 does not enhance insulin-stimulated glucose uptake in skeletal muscle. In addition, generation of FGF21 responsiveness and direct signaling to skeletal muscle also has no effect on FGF21-mediated increases in whole-body or skeletal muscle insulin sensitivity. Instead, FGF21 uniquely signals to brown adipocytes to enhance insulin-stimulated glucose uptake. Therefore, to identify how FGF21 signals to brown adipocytes to enhance insulin sensitivity, we performed comprehensive phospho-proteomics in brown adipocytes in response to FGF21 and/or insulin. Our results indicate that FGF21 administration increases the phosphorylation of several proteins involved in the trafficking of GLUT4 in primary brown adipocytes. These results provide new insights into how FGF21 enhances insulin sensitivity.

Anterior pituitary hormone secretion is generally considered to be under the strong regulation of hypothalamic neuropeptides. In mammals, adrenocorticotropic hormone (ACTH), which plays a crucial role in the stress response, is secreted from corticotropes and is regulated primarily by corticotropin-releasing hormone (CRH). In teleosts, although the pharmacological effects of hypothalamic factors have been demonstrated, their relative importance in regulating ACTH release remains controversial. One reason for this is the lack of methods for evaluating ACTH release at cellular resolution. Using medaka as a model organism, we systematically examined the direct effects of hypothalamic peptides on ACTH cells by combining cell type-specific transcriptomics with Ca²⁺ imaging. We show that thyrotropin-releasing hormone (TRH) robustly elevates intracellular Ca²⁺ ([Ca²⁺]ᵢ) levels in ACTH cells, surpassing the responses elicited by CRH or arginine vasotocin (AVT). TRH also strongly activates MSH cells, the other POMC-derived pituitary cell population, while CRH induces only a modest response. Furthermore, in situ hybridization chain reaction analyses revealed that TRH receptor (trhra) is expressed in MSH cells, supporting their direct responsiveness to TRH signaling, whereas TRH receptor expression in ACTH cells was below thsse detection limit, leaving open the possibility that their activation is mediated by indirect or low-abundance receptor pathways. These findings suggest the existence of a novel TRH-driven regulatory pathway orchestrating both the teleost stress axis and pigmentation axis.

Growth hormone (GH) controls sexual dimorphism in hepatocyte gene expression programs governing lipid metabolism, bile acid synthesis and xenobiotic processing, which contribute to sex differences in metabolic dysfunction-associated steatotic liver disease (MASLD) risk. Although GH-regulated sex-specific transcription is well-studied, the functional cis-regulatory hepatocyte enhancers that orchestrate these sex-dependent metabolic programs remain largely unknown. Here, we integrated single-nucleus multiomic profiling of hepatocyte chromatin accessibility with in vivo functional enhancer assays to identify and validate GH-responsive, sex-biased hepatocyte enhancers in intact mouse liver. We constructed a tiled HDI-STARR-seq library of 23,912 reporters spanning 1,839 liver ATAC regions and delivered it to liver by hydrodynamic injection, enabling enhancer activity assessment across different biological conditions. Reporters representing 840 ATAC regions showed sex-biased and/or GH-regulated enhancer activity, in many cases mirroring regulation of their accessibility in hepatocyte chromatin, validating them as functional, physiologically regulated enhancers. The regulated enhancer sequences were enriched for activating histone marks (H3K27ac, H3K4me1), and for binding sites for the STAT5-dependent, sex-specific repressors BCL6 and CUX2; whereas, STAT5 binding was enriched at both regulated and non-regulated enhancers. Motifs for HNF4A and for several novel factors identified de novo were specifically enriched at the regulated enhancers. Sex-biased and GH-regulated enhancers were linked to both MASLD-enabling and MASLD-protective genes, suggesting that GH-dependent chromatin remodeling at these loci contributes to sex-differential metabolic disease susceptibility. This integrated in vivo approach defines a validated set of GH-regulated hepatocyte enhancers through which chromatin accessibility and transcription factor binding drive sexual dimorphism in hepatic metabolism and MASLD risk.

The clinical characteristics of type 2 diabetes (T2D) differ between the sexes. For example, the risk of T2D is higher in males than in premenopausal females, whereas the risk of T2D-associated cardiovascular disease is higher in females. However, the sex-dependent mechanisms of T2D pathogenesis remain incompletely understood. Publicly available human islet datasets, such as HPAP and Humanislets.com, offer a valuable tool for uncovering the impact of biological sex on islet structure, gene expression, and function at a scale that was not previously possible. We performed an integrated analysis of data from publicly available sources to identify sex differences in baseline islet characteristics in donors without diabetes and subsequently examined these features in donors who lived with T2D. Among donors without diabetes, female islets had a greater proportion of alpha-cells compared with male islets and showed enriched expression of ribosomal and mitochondrial pathways in both beta- and alpha-cells. Measurements of mitochondrial function in female islets revealed lower spare respiratory capacity compared to male islets. Male and female islets had distinct changes in gene and protein expression in the context of T2D with female islets having greater preservation of insulin content and fewer defects in islet function. Together, these data show female islets have fewer islet impairments in T2D. This highlights the need for detailed mechanistic studies in both sexes to support effective and sex-informed interventions for T2D.