Journal of Endocrinology最新文献

We recently showed that the ratio of capillaries to myofibers in skeletal muscle, which accounts for 80% of insulin-directed glucose uptake and metabolism, was reduced in baboon fetuses in which estrogen was suppressed by maternal letrozole administration. Since vascular endothelial growth factor (VEGF) promotes angiogenesis, the present study determined the impact of estrogen deprivation on fetal skeletal muscle VEGF expression, capillary development, and long-term vascular and metabolic function in 4- to 8-year-old adult offspring. Maternal baboons were untreated or treated with letrozole or letrozole plus estradiol on days 100-164 of gestation (term = 184 days). Skeletal muscle VEGF protein expression was suppressed by 45% (P < 0.05) and correlated (P = 0.01) with a 47% reduction (P < 0.05) in the number of capillaries per myofiber area in fetuses of baboons in which serum estradiol levels were suppressed 95% (P < 0.01) by letrozole administration. The reduction in fetal skeletal muscle microvascularization was associated with a 52% decline (P = 0.02) in acetylcholine-induced brachial artery dilation and a 23% increase (P = 0.01) in mean arterial blood pressure in adult progeny of letrozole-treated baboons, which was restored to normal by letrozole plus estradiol. The present study indicates that estrogen upregulates skeletal muscle VEGF expression and systemic microvessel development within the fetus as an essential programming event critical for ontogenesis of systemic vascular function and insulin sensitivity/glucose homeostasis after birth in primate offspring.

The fundamental models underlying hormonal physiological regulation and homeostasis remain poorly understood. We aimed to derive quantitative evidence regarding these models from the study of population data of balance points of different parameters and their respective controlling hormones. We studied the slopes of correlations between concentrations of circulating free thyroxine and thyrotropin, calcium and parathyroid hormone, hemoglobin and erythropoietin, and glucose and insulin in such population data, as well as the slopes of the limbs of various feedback loops estimated empirically and by reverse engineering of the population data. We used computer simulations to model the factors that influence the slopes derived from the population data, and then matched these simulations with the empirically derived slopes. Our simulations showed that changes to the population distribution of feedback loop limbs may alter the slopes of correlations within population data in specific ways. Non-random (interdependent) associations of the limbs of feedback loops may also have this effect, as well as producing discrepancies between the slopes of feedback limb loops determined experimentally and the same slopes determined by derivation from population data. Our corresponding empirical findings were consistent with the presence of such interdependence in the free thyroxine/thyrotropin, hemoglobin/erythropoietin, and glucose/insulin systems. The glucose/insulin data provided evidence consistent with increasing interdependence with age in childhood. Our findings therefore provide strong evidence that the interdependence of the limbs of feedback loops is a general feature of endocrine homeostatic regulation. This interdependence potentially bestows evolutionary homeostatic and regulatory advantages.

CD44, a cell surface adhesion receptor and stem cell biomarker, is recently implicated in chronic metabolic diseases. Ablation of CD44 ameliorates adipose tissue inflammation and insulin resistance in obesity. Here, we investigated cell type specific CD44 expression in human and mouse adipose tissue and further studied how CD44 in preadipocytes regulates adipocyte function. Using Crispr Cas9-mdediated gene deletion and lentivirus-mediated gene re-expression, we discovered that deletion of CD44 promotes adipocyte differentiation and adipogenesis, whereas re-expression of CD44 abolishes this effect and decreases insulin responsiveness and adiponectin secretion in 3T3-L1 cells. Mechanistically, CD44 does so via suppressing Pparg expression. Using quantitative proteomics analysis, we further discovered that cell cycle-regulated pathways were mostly decreased by deletion of CD44. Indeed, re-expression of CD44 moderately restored expression of proteins involved in all phases of the cell cycle. These data were further supported by increased preadipocyte proliferation rates in CD44 deficient cells and re-expression of CD44 diminished this effect. Our data suggest that CD44 plays a crucial role in regulating adipogenesis and adipocyte function possibly through regulating PPARɣ and cell cycle-related pathways. This study provides evidence for the first time that CD44 expressed in preadipocytes plays key roles in regulating adipocyte function outside immune cells where CD44 is primarily expressed. Therefore, targeting CD44 in (pre)adipocytes may provide therapeutic potential to treat obesity-associated metabolic complications.

The impaired endometrial receptivity is a major factor contributing to infertility in patients with endometriosis (EM), but the underlying mechanism remains unclear. Our study aimed to investigate the role of Kruppel-like factor 15 (KLF15) in endometrial receptivity and its regulation in EM. We observed a significant decrease in KLF15 expression in the mid-secretory epithelial endometrial cells of EM patients compared to normal females without EM. To confirm the role of KLF15 in endometrial receptivity, we found a significantly reduced KLF15 expression and a significant decrease in embryo implantation number in the rat model via uterine horn infection with siRNA. This highlights the importance of KLF15 as a regulator receptivity. Furthermore, through ChIP-qPCR, we discovered that the progesterone receptor (PR) directly binds to KLF15 promoter regions, indicating that progesterone resistance may mediate the decrease in KLF15 expression in EM patients. Additionally, we found that the mid-secretory endometrium of EM patients exhibited impaired epithelial-mesenchymal transition (EMT). Knockdown of KLF15 upregulated E-cadherin and downregulated vimentin expression, leading to inhibited invasiveness and migration of Ishikawa cells. Overexpression KLF15 promotes EMT, invasiveness, and migration ability, and increases the attachment rate of JAR cells to Ishikawa cells. Through RNA-seq analysis, we identified TWIST2 as a downstream gene of KLF15. We confirmed that KLF15 directly binds to the promoter region of TWIST2 via ChIP-qPCR, promoting epithelial cell EMT during the establishment of endometrial receptivity. Our study reveals the involvement of KLF15 in the regulation of endometrial receptivity and its downstream effects on EMT. These findings provide valuable insights into potential therapeutic approaches for treating non-receptive endometrium in patients with EM.

Thyroid disorders affect more women than men, but the underlying mechanisms contributing to this disparity remain incompletely understood. Thyrotropin (TSH), the primary regulator of thyroid oxidative hormonogenesis, has been implicated as a risk factor for proliferative thyroid diseases and a predictor of malignancy. In this study, we aimed to evaluate the impact of sustained elevated TSH levels on thyroid redox homeostasis, inflammatory markers, and DNA damage response in both male and female rats. Rats were treated with methimazole for 7 or 21 days, and hormonal measurements were conducted. H2O2 levels were evaluated in thyroid membrane fractions, while enzymatic activities were assessed in total thyroid homogenates. Sex-specific differences emerged, with females displaying higher reactive oxygen species levels - increased transiently NOX and sustained DUOX activities. Lipid peroxidation marker 4-hydroxynonenal (4-HNE) was elevated in females at both time points, contrasting with males just at 21 days. Sexual dimorphism was observed in DNA damage response, with females showing higher γH2AX levels at 21 days. Elevated IL-1β, TNF-α, CD11b mRNA, and phospho-NF-κB levels at 7 days indicated a distinct inflammatory profile in females. Notably, both sexes exhibited upregulated antioxidant enzymes. Our data suggest that females are more susceptible to oxidative damage and inflammation in our goiter model, which may be associated with higher ROS production and a less-efficient antioxidant defense system. These findings provide insights into the sex-specific mechanisms underlying thyroid dysfunction and highlight the importance of considering sex disparities in thyroid disorder research.

The glucagon-like peptide 1 receptor (GLP-1R) is a class B G protein-coupled receptor (GPCR) that emerged as a pharmacologic target in cardiometabolic disease, including diabetes and obesity, over 30 years ago. The subsequent widespread clinical use of GLP-1R agonists, including exenatide, liraglutide, and semaglutide, has made the GLP-1R a preeminent model for understanding basic GPCR biology, including the emergent field of biased agonism. Recent data demonstrate that the dual GLP-1R/glucose dependent insulinotropic polypeptide receptor (GIPR) agonist tirzepatide exhibits a biased signaling profile characterized by preferential Gαs activation over β-arrestin recruitment, which appears to contribute to its insulinotropic and body-weight reducing effects in preclinical models. This constitutes a major finding in which nuanced, mechanistic receptor signaling dynamics in vitro mediate real-world clinical differentiation within a drug class. Because of the striking bench-top-to-bed side relevance of this biased signaling phenomenon, we have undertaken a review of the emerging data detailing biased agonism at the GLP-1R. In this review, we introduce the core concept of biased agonism followed by a detailed consideration of the key mechanisms, including ligand-mediated bias, receptor-mediated bias, and systems/cell-type bias. Current industry programs are largely, if not entirely, focused on developing biased ligands, and so we have dedicated a section of the review to a brief meta-analysis of compounds reported to drive biased signaling, with a consideration of the structural determinants of receptor-ligand interactions. In this work, we aim to assess the current knowledge regarding signaling bias at the GLP-1R and how these ideas might be leveraged in future optimization.

For many years, research in the field of steroid synthesis has aimed to understand the regulation of the rate-limiting step of steroid synthesis, i.e. the transport of cholesterol from the outer to the inner mitochondrial membrane, and identify the protein involved in the conversion of cholesterol into pregnenolone. The extraordinary work by B Clark, J Wells, S R King, and D M Stocco eventually identified this protein and named it steroidogenic acute regulatory protein (StAR). The group's finding was also one of the milestones in understanding the mechanism of nonvesicular lipid transport between organelles. A notable feature of StAR is its high degree of phosphorylation. In fact, StAR phosphorylation in the acute phase is required for full steroid biosynthesis. As a contribution to this subject, our work has led to the characterization of StAR as a substrate of kinases and phosphatases and as an integral part of a mitochondrion-associated multiprotein complex, essential for StAR function and cholesterol binding and mitochondrial transport to yield maximum steroid production. Results allow us to postulate the existence of a specific cellular microenvironment where StAR protein synthesis and activation, along with steroid synthesis and secretion, are performed in a compartmentalized manner, at the site of hormone receptor stimulation, and involving the compartmentalized formation of the steroid molecule-synthesizing complex.

Estrogen deficiency is one of the main causes for postmenopausal osteoporosis. Current osteoporotic therapies are of high cost and associated with serious side effects. So there is an urgent need for cost-effective anti-osteoporotic agents. Anti-osteoporotic activity of Litsea glutinosa extract (LGE) is less explored. Moreover, its role in fracture healing and mechanism of action is still unknown. In the present study we explore the osteoprotective potential of LGE in osteoblast cells and fractured and ovariectomized (Ovx) mice models. Alkaline phosphatase (ALP), MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and mineralization assays revealed that LGE treatment increased osteoblast cell differentiation, viability and mineralization. LGE treatment at 0.01 μg increased the expression of BMP2, PSMAD, RUNX2 and type 1 col. LGE also mitigated RANKL-induced osteoclastogenesis. Next, drill hole injury Balb/C mice model was treated with LGE for 12 days. Micro-CT analysis and Calcein labeling at the fracture site showed that LGE (20 mg/kg) enhanced new bone formation and bone regeneration, also increased expression of BMP2/SMAD1 signaling genes at fracture site. Ovx mice were treated with LGE for 1 month. μCT analysis indicated that the treatment of LGE at 20 mg/kg dose prevented the alteration in bone microarchitecture and maintained bone mineral density and bone mineral content. Treatment also increased bone strength and restored the bone turnover markers. Furthermore, in bone samples, LGE increased osteogenesis by enhancing the expression of BMP2/SMAD1 signaling components and decreased osteoclast number and surface. We conclude that LGE promotes osteogenesis via modulating the BMP2/SMAD1 signaling pathway. The study advocates the therapeutic potential of LGE in osteoporosis treatment.

The glucagon receptor family are typical class B1 G protein-coupled receptors (GPCRs) with important roles in metabolism, including the control of pancreas, brain, and liver function. As proteins with 7 transmembrane domains, GPCRs are intimately in contact with lipid bilayers and therefore can be putatively regulated by interactions with their lipidic components, including cholesterol, sphingolipids, and other lipid species. Additionally, these receptors, as well as the agonists they bind to, can undergo lipid modifications, which can influence their binding capacity and/or elicit modified or biased signalling profiles. While the effect of lipids, and in particular cholesterol, has been widely studied for other GPCR classes, information about their role in regulating the glucagon receptor family is only beginning to emerge. Here we summarise our current knowledge on the effects of cholesterol modulation of glucagon receptor family signalling and trafficking profiles, as well as existing evidence for specific lipid–receptor binding and indirect effects of lipids via lipid modification of cognate agonists. Finally, we discuss the different methodologies that can be employed to study lipid-receptor interactions and summarise the importance of this area of investigation to increase our understanding of the biology of this family of metabolically relevant receptors.

Exposure to glyphosate-based herbicides (GBH) and consumption of cafeteria (CAF) diet, which are widespread in Western society, seem to be associated with endometrial hyperplasia (EH). Here, we aimed to evaluate the effects of a subchronic low dose of a GBH added to CAF diet on the rat uterus. Female Wistar rats were fed from postnatal day (PND)21 until PND240 with chow (Control) or CAF diet. Since PND140, rats also received GBH (2 mg of glyphosate/kg/day) or water through food, yielding four experimental groups: Control, CAF, GBH and CAF+GBH. On PND240, CAF and CAF+GBH animals showed an increased adiposity index. Respect to Control group, no changes on the serum levels of 17β-estradiol and progesterone were found. However, progesterone levels were higher in CAF+GBH group than in CAF and GBH groups. In the uterus, both studied factors alone and in combination induced morphological and molecular changes associated with EH. Furthermore, the addition of GBH provoked an increased thickness of subepithelial stroma in rats fed with CAF diet. As a consequence of GBH exposure, CAF+GBH rats exhibited an increased density of abnormal gland area, considered preneoplastic lesions, as well as a reduced PTEN and p27 expression, both tumor suppressor molecules that inhibit cell proliferation, respect to Control rats. These results indicate that the addition of GBH exacerbates the CAF-effects on uterine lesions and that the PTEN/p27 signaling pathway seems to be involved. Further studies focusing on the interaction between unhealthy diets and environmental chemicals should be encouraged to better understand uterine pathologies.