Journal of molecular endocrinology最新文献

Obesity is known to have detrimental effects on female fertility, influencing both ovarian and endometrial functions. There is evidence that endometrial function is altered in obese and/or insulin-resistant women. Metformin, an insulin-sensitizing drug, has shown potential in treating metabolic and reproductive disorders, including polycystic ovary syndrome (PCOS) and may enhance fertility outcomes by improving endometrial dysfunction. Using a mouse model, this study aimed to investigate how a high-fat diet impacts endometrial-specific protein expression and whether metformin can mitigate these effects. C57BL/6N mice were fed a standard or high-fat diet and either received metformin treatment or did not. Proteomic analyses revealed significant alterations in endometrial protein expression due to the high-fat diet, while metformin administration appeared to restore many of these changes to normal levels. Metformin's impact was evident through alterations in specific proteins associated with reproductive health and metabolic functions, such calcium-independent phospholipase A2-gamma, ATP-binding cassette sub-family D member 1, RAC-beta serine/threonine-protein kinase, acyl-CoA:lysophosphatidylglycerol acyltransferase 1, O-GlcNAcase, scavenger receptor class A member 3, protein kinase C beta type, sortilin, beta-2-microglobulin and apolipoprotein C-III. These results suggest a potential therapeutic role for metformin in normalizing endometrial protein expression, providing insights into how this drug could improve fertility outcomes in obese or insulin-resistant females, besides normalizing ovulation patterns. Overall, this study enhances our understanding of the relationship among obesity, endometrial function and metformin's therapeutic potential, offering a foundation for further research into reproductive health and metabolic disorders.

Osteoporosis diagnoses are increasing in the ageing population, and although some treatments exist, these have several disadvantages, highlighting the need to identify new drug targets. G protein-coupled receptors (GPCRs) are transmembrane proteins whose surface expression and extracellular activation make them desirable drug targets. Our previous studies have identified 144 GPCR genes to be expressed in primary human osteoclasts, which could provide novel drug targets. The development of high-throughput assays to assess osteoclast activity would improve the efficiency at which we could assess the effect of GPCR activation on human bone cells and could be utilised for future compound screening. Here, we assessed the utility of a high-content imaging (HCI) assay that measured cytoplasmic-to-nuclear translocation of the nuclear factor of activated T cells-1 (NFATc1), a transcription factor that is essential for osteoclast differentiation, and resorptive activity. We first demonstrated that the HCI assay detected changes in NFATc1 nuclear translocation in human primary osteoclasts using GIPR as a positive control, and then developed an automated analysis platform to assess NFATc1 in nuclei in an efficient and unbiased manner. We assessed six GPCRs simultaneously and identified four receptors (FFAR2, FFAR4, FPR1 and GPR35) that reduced osteoclast activity. Bone resorption assays and measurements of TRAP activity verified that activation of these GPCRs reduced osteoclast activity, and that receptor-specific antagonists prevented these effects. These studies demonstrate that HCI of NFATc1 can accurately assess osteoclast activity in human cells, reducing observer bias and increasing efficiency of target detection for future osteoclast-targeted osteoporosis therapies.

Somatostatin (Sst) is an inhibitory regulator of many hormones. The prenatal environment impacts an offspring's risk to type 2 diabetes in adulthood. However, the effect of maternal Sst deficiency on glucose and insulin metabolism in offspring and metabolic disease risk in their adult life has been poorly understood. The study was to investigate the impact of a lack of maternal Sst exposure in mouse male and female offspring on diet-induced changes in glucose metabolism and adiposity. Sst knockout offspring, SstKO born to the Sst-heterozygous dams or SstKO-MSD born to the Sst-homozygous dams were fed either a regular diet (CD) or a high-fat diet (HFD) at 3-week-old for 15 weeks. Body weight and blood glucose levels were monitored. Glucose and insulin tolerance tests were performed. Plasma hormone levels and gene expression in the hypothalamus were investigated. The results demonstrated that only male SstKO-MSD offspring developed obesity accompanied by severe insulin and leptin resistance after HFD challenge. Insulin secretion was reduced in both basal and oral glucose-challenged conditions in the CD-fed male SstKO-MSD mice. A reduced ratio of islet area to pancreas area was noted in SstKO-MSD mice in both sexes. Plasma levels of glucagon, Glp1 and Pyy were elevated in both male and female SstKO and SstKO-MSD mice. mRNA expression of leptin receptor, FoxO1, Npy and Agrp was downregulated in male SstKO-MSD mice. These results demonstrate that a lack of fetal somatostatin exposure impairs the islet development in offspring and increases risk of obesity, insulin resistance and leptin resistance later in life.

The core clock gene Bmal1 has been associated with the development of a variety of inflammatory diseases, with its deletion shown to induce or aggravate autoimmune disease in a tissue-specific pattern. Building on our previous findings that light shift can disrupt thyroid clock and exacerbate autoimmune thyroiditis (AIT), we investigated the specific role of the thyroid clock in AIT using a thyrocyte-specific Bmal1 knockdown mouse model (cKO). Our study revealed that Bmal1 knockdown in thyrocytes disrupted the rhythmic expression of intrathyroidal clock genes. Both cKO and Ctrl mice exhibited more severe experimental autoimmune thyroiditis (EAT) when immunized at ZT6 compared to ZT18. However, cKO-EAT mice showed elevated levels of anti-thyroglobulin antibodies (TgAb) and inflammatory cytokines compared to Ctrl-EAT mice, which correlated with CD4+ T cell-mediated immune responses. These findings highlight a novel role for Bmal1 in regulating the thyroid clock and modulating the severity of EAT, uncovering a previously unrecognized connection between circadian regulation and thyroid autoimmune disease.

Lipopolysaccharides (LPS) are major components of gram-negative bacteria. LPS not only induce endotoxemia and inflammation but also contribute to various diseases. In experimental settings, LPS administration serves as a model for acute inflammatory responses. This study aimed to evaluate the anti-inflammatory potential and mechanism of action of palmitoylated prolactin-releasing peptide (palm11-PrRP31) in a rat model of LPS-induced inflammation. Palm11-PrRP31 has demonstrated efficacy in mitigating LPS-induced weight loss and anorexia, emphasizing its potential protective effects. The cytokine profiles revealed a consistent reduction in tumor necrosis factor α, highlighting the potent anti-inflammatory effects of palm11-PrRP31. The peptide also modulated key cytokines and chemokines in the plasma, liver and hypothalamus, reflecting its broad-spectrum anti-inflammatory properties. Palm11-PrRP31 also effectively attenuated the expression levels of Toll-like receptor 4 signaling components in the liver, suggesting its ability to suppress the activation of these pathways during LPS-induced inflammation. These anti-inflammatory effects were specific to palm11-PrRP31, whereas natural PrRP31 had a minimal impact. In conclusion, this study reveals the efficacy of palm11-PrRP31 in modulating LPS-induced inflammation, offering insights into its immunomodulatory properties. The ability of the peptide to suppress proinflammatory responses and attenuate relevant signaling pathways indicates its potential use as a therapeutic agent for inflammatory disorders.

Delayed wound closure is a significant hallmark associated with diabetes. A previous study from our laboratory identified decreased levels of Dicer and miRNAs together with altered levels of wound-healing genes in the wounded tissues of diabetic rats. Comprehensive regulators of these wound-healing genes mapped onto the PRC2 (polycomb repressive complex 2) complex. Here, we show that Dicer inhibition increases the transcript levels of core components of the PRC2 complex, namely Suz12 (suppressor of zeste 12) and Ezh2 (enhancer of zeste 2), and of Mtf2 (metal response element-binding transcription factor 2), its additional subunit, and elevates H3K27me3 levels in HaCaT cells. Such patterns of increase were also observed in the wounded tissues of diabetic rats as compared to those of normal rats. In a scratch assay in HaCaT cells, while Dicer inhibition significantly prevented wound closure, this was rescued by Suz12 siRNA but not by Ezh2 inhibition, suggesting that Suz12 mediates the effects of Dicer siRNA in these cells. In addition, as compared to scramble-transfected cells, Dicer siRNA decreased the levels of integrin alpha V (Itgav), which is extensively implicated in the process of wound healing, and this effect was rescued in the presence of Suz12 siRNA. Itgav harbours potential histone methylation marks across the gene length, and Dicer inhibition, by increasing PRC2-mediated H3K27 methylation on Itgav, possibly decreases its transcription that subsequently impairs wound closure. These data put forth novel aspects of delayed wound closure as seen during diabetes and might be a potential target for therapeutic intervention.

In endocrinology, there are many similarities in the regulation of gene expression between alleles, paralogous genes or orthologous genes, at the genetic or epigenetic level. However, there are also major differences in the spatial and temporal expression patterns of these genes, in particular between species. In few cases, it has been shown in vitro and/or in vivo that regulatory differences are mainly due to subtle differences (from one bp to less than 12 bp) in the nucleotide sequence of transcription factor-binding sites localized in the vicinity of the proximal promoter. In this short review, we propose to cite some of them, without claiming to be exhaustive. We also briefly review new methodologies that allow for more global studies of comparisons of expression regulations at the transcriptional level. We also discuss whether such studies could have given rise to any paradigm.

Glucose transporter type 2 (GLUT2), encoded by the Slc2a2 gene, is essential for glucose-stimulated insulin secretion (GSIS) in pancreatic islet β-cells, and low expression of GLUT2 is associated with β-cell dysfunction during the progression of type 2 diabetes in humans and animal models. Glucocorticoids are stress hormones that regulate inflammation and metabolism through the glucocorticoid receptor (GR), a member of the nuclear receptor superfamily, and synthetic glucocorticoids are widely used for the treatment of inflammatory disorders. Prolonged exposure to glucocorticoids induces β-cell dysfunction and diabetes, but the effects of Slc2a2 gene repression in β-cells, if any, and the mechanisms involved remain unclear. In the present study, we measured the expression of GSIS-related genes in the MIN6 β-cell line and found that Slc2a2 mRNA expression was selectively reduced by dexamethasone (DEX), a synthetic glucocorticoid. Using bioinformatics and reporter assays, we identified two β-cell enhancers of the Slc2a2 gene, one within the first intron and another located approximately 40 kb downstream of the transcription start site. The latter enhancer (designated as E3c) was responsible for the DEX-induced repression of the Slc2a2 gene. Of the previously identified β-cell-enriched transcription factors (NEUROD1, MAFA, HNF1α and HNF1β) that activate the E3c enhancer, the transcriptional activity of HNF1α and HNF1β, responsible for maturity-onset diabetes of the young types 3 and 5, respectively, was repressed by DEX and GR. This functional link between HNF1α/HNF1β and GR should help elucidate the mechanism of glucocorticoid-induced β-cell dysfunction and diabetes.

Diabetes is a complex disease that impacts more than 500 million people across the world. Many of these individuals will develop diabetic neuropathy as a comorbidity, which is historically treated with exogenous opioids, such as morphine, oxycodone, or tramadol. Although these opioids are effective analgesics, growing evidence indicates that they may directly impact the endocrine pancreas function in patients. One common feature of these exogenous opioid ligands is their preference for the mu-opioid receptor (MOPR), so we aimed to determine whether endogenous MOPRs directly regulate pancreatic islet metabolism and hormone secretion. We show that pharmacological antagonism of MOPRs enhances glucagon secretion, but not insulin secretion, from human islets under high-glucose conditions. This increased secretion is accompanied by increased cAMP signaling. mRNA expression of MOPRs is robust in nondiabetic human islets but downregulated in islets from T2D donors, suggesting a link between metabolism and MOPR expression. Conditional genetic knockout of MOPRs in murine α-cells increases glucagon secretion under high-glucose conditions without increasing glucagon content. Consistent with downregulation of MOPRs during metabolic disease, conditional MOPR knockout mice treated with a high-fat diet show impaired glucose tolerance, increased glucagon secretion, increased insulin content, and increased islet size. Together, these results demonstrate a direct mechanism of action for endogenous opioid regulation of endocrine pancreas.

Ghrelin is a gut hormone that enhances food intake and growth hormone secretion through its G-protein coupled receptor, the growth hormone secretagogue receptor (GHSR). Recently, we have shown that ghrelin interacts with syndecans (SDCs), a family of membrane proteins known to modulate hypothalamic appetite signaling. Here, we investigated whether SDCs impact ghrelin signaling at GHSR by assessing ghrelin-induced intracellular Ca2+ mobilization (iCa2+) and inositol phosphate 1 (IP1) production in HEK293 cells. Compared with controls, the overexpression of SDCs dose-dependently increased the maximum iCa2+ response two- to four-fold, without affecting EC50. The IP1 response was similarly amplified by SDCs, but it also indicated that they reduce constitutive (ghrelin-independent) activity of GHSR. These enhanced responses occurred despite a SDC dose-dependent reduction in plasma membrane GHSR levels. Although ghrelin-stimulated Gαq activation was unaltered by SDC1 expression, it failed to restore iCa2+ responsiveness in GNAQ/11 knockout cells, indicating dependence on Gαq/11, not another Gα subunit. This suggests that SDCs modulate either signaling downstream of Gαq/11 or quenching of β-arrestin2 recruitment to GHSR. Indeed, expression of SDCs at levels that only modestly suppress cell surface receptor reduced ghrelin-induced β-arrestin2 recruitment by ∼80%. SDC co-expression also delayed the peak β-arrestin2 response. However, peak β-arrestin2 recruitment follows the peak iCa2+ response, making it unclear whether reduced β-arrestin2 recruitment potentiated Ca2+ signaling. Altogether, SDCs enhanced iCa2+/IP1 and reduced β-arrestin2 recruitment by GHSR in response to ghrelin, likely by modulating signaling downstream of Gαq. This could be a novel mechanism through which SDCs affect metabolism and obesity.