Endocrinology最新文献

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.

Glucagon is a peptide hormone mainly secreted by the alpha cells of the pancreatic islets in response to nutritional stimuli. Traditionally recognized for its hyperglycemic function counteracting insulin action, it mainly acts on the liver to affect glycogen, amino acid, lipid, and energy metabolism. Beyond its metabolic effects, glucagon also increases hepatocyte cell survival and reduces viral replication. Peptides with glucagon-activity have recently emerged as a promising therapeutic candidate for obesity, type 2 diabetes, and associated liver disease, with several glucagon-based agents currently in phase 2/3 clinical trials. Despite this progression, and although discovered roughly the same time as insulin, how glucagon exerts its pleiotropic effects on metabolism and beyond remains relatively poorly understood. Knowledge of these signaling pathways could pave the way for further refinement of glucagon-based pharmacotherapy with more pronounced effects or reduced side effects. This review aims to address established literature and its limitations on glucagon signaling mechanisms, and provides an update on the state-of-the-art on glucagon signaling pathways to help in understanding the mechanisms behind glucagon action.

Socio-sexual behaviors, a key aspect of mammalian biology, are governed by evolutionarily conserved neuronal circuits that control partner preference, sexual attraction, and attachment. This mini-review summarizes recent advances in understanding neuroendocrine pathways involved in various levels of socio-sexual interactions, from mating preferences to forming long-term sexual partnerships. We first briefly examine how prenatal hormone exposure shapes brain structures that later influence partner choices, with a particular focus on mechanisms driven by sex steroid hormones in rodent models. We also highlight some of the latest evidence showing how multimodal sensory cues activate neural circuits and neuroendocrine responses to initiate sexual behaviors. Finally, we examine how molecularly defined neuronal populations differently impact sexual performance and socio-sexual attachment in a sex-dependent manner. Some of the evidence presented here might have been overlooked and warrants greater attention to improve guidance and discuss future directions for our field.

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.

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 sub-type 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 fibre 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.

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 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.

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.

A large "gene desert" located far upstream from Fshb and Kcna4 contains several gonadotrope-specific accessible chromatin sites which were seen in chromatin conformation capture (3C) to make distinct contacts with both genes. Expression of Fshb and Kcna4 was strongly inhibited by JQ-1, which represses super-enhancer activity, and the region displays super-enhancer characteristics. The sites of open chromatin were seen, in chromatin immunoprecipitation (ChIP), to bind Brd4 and Med1, most notably at a site -67 kb from the Fshb gene, as well as binding Ctcf further upstream (-123 kb), all of which were increased following activin exposure. The locus is transcribed to chromatin-associated lncRNAs whose levels correlate with Fshb and Kcna4 mRNA levels in vivo and in cultured gonadotrope cells, indicating coordinated regulation. CRISPR interference (CRISPRi) confirmed distinct functions for each element and, together with the 3C data, indicate that the -67 kb locus mediates basal and activin-stimulated Fshb expression, while the site at -59 kb contributes to activin-stimulation of both genes. Single-cell multiomics revealed that the -67 kb locus is accessible in pituitary stem cells and throughout gonadotrope differentiation, preceding opening of the Fshb promoter, although it is closed in other differentiated cell types, suggesting a gonadotrope-specific factor that keeps it open at this stage. Foxl2 was found to bind this element, contributes to maintaining its chromatin accessibility, and recruits Supt16h, a component of the Facilitates Active Chromatin Transcription (FACT) histone chaperone complex. These findings define a distal, Foxl2-bound super-enhancer that regulates Fshb transcription and shapes the gonadotrope regulatory landscape.

Polycystic ovary syndrome (PCOS) is a systemic endocrine disorder characterized by perturbations in both androgen and insulin signaling pathways that result in anovulatory infertility and metabolic syndrome. This study aimed to elucidate insulin signaling in the PCOS ovary using a mouse model that develops both the metabolic and reproductive manifestations of PCOS due to chronic postnatal dihydrotestosterone exposure. PCOS mice developed anovulation, cystic follicles, systemic insulin resistance with compensatory hyperinsulinemia and mild excess adiposity, but not hepatic steatosis, adipose inflammation or frank obesity, suggesting that hyperandrogenism is the main driver of the metabolic perturbations in this model. Insulin signaling was then assessed in the ovary, liver, and skeletal muscle from hyperinsulinemic, fasting PCOS mice. Ovarian theca and granulosa cells showed upregulated markers of insulin signaling, while the liver and skeletal muscle from the same mice showed no changes compared to controls. However, cultured primary PCOS hepatocytes were profoundly insulin resistant in vitro, while primary theca cells (TCs) and granulosa cells (GCs) isolated from the same PCOS mice were insulin-sensitive. Both PCOS TCs and GCs produced significantly more steroid hormones than control cells when stimulated with insulin and gonadotropins. Our findings indicate that the PCOS ovary remains sensitive to insulin despite systemic insulin resistance, and that insulin works synergistically with gonadotropins to stimulate ovarian testosterone production in PCOS. We therefore suggest that insulin resistance is not merely a byproduct of hyperandrogenism but is a disease-driving factor in PCOS and should be treated as a clinical target in PCOS management.