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The novel adipokine asprosin, produced by the furin enzymatic cleavage of profibrillin 1 protein (encoded by the Fbn1 gene), is implicated in regulating many physiological functions, including reproduction in mammals. In males, asprosin is reported to increase sperm density, sperm motility, and steroid production by interacting with Olfr734, which belongs to the G-protein-coupled receptor family (GPCR). In 2023, our group predicted and characterized asprosin in silico for the first time and demonstrated the robust expression of fbn1, and furin in the gonads of teleost spotted snakehead (ss) Channa punctata. Taking it forward, in the current study, we have investigated the effect of asprosin on the testicular functions of the spotted snakehead. As C. punctata is a seasonal breeder, the reproductive-phase-dependent expression of fbn1 in the testis was analyzed, showing significant upregulation during the preparatory and post-spawning phases. Additionally, bacterially overexpressed recombinant asprosin of C. punctata was purified to study the effect of ss asprosin on gametogenesis and steroidogenesis. Ex vivo treatment with recombinant asprosin resulted in significant upregulation of spermatogenic marker genes pcna, aldh1a2, cyp26a1, and sycp3. Asprosin also enhanced the gene expression of gonadotropin receptors, as well as sex steroid receptors, in addition to steroidogenic genes star and cyp17a1. Further exploring the downstream signaling cascade, the second messenger of GPCRs, cAMP levels following asprosin treatment were analyzed. Asprosin treatment prominently enhanced cAMP levels, thereby indicating the involvement of GPCR in the transduction of asprosin action. Hence, the study elucidates the regulation of male reproductive function by asprosin in spotted snakeheads.
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Liraglutide, an analog of the incretin hormone glucagon-like peptide 1 (GLP-1), is widely used for obesity and type 2 diabetes treatment. However, there is scarce information about its effects on testicular function. Within the testis, Sertoli cells (SCs) provide nutritional support for germ cells; they metabolize glucose to lactate, which is delivered to germ cells to be used as a preferred energy substrate. Besides, SCs use fatty acids (FAs) as an energy source and store them as triacylglycerols (TAGs) within lipid droplets (LDs), which serve as an important energy reserve. In the present study, 20-day-old rat SC cultures were used to assess whether liraglutide affects their metabolic functions related to nutritional support and lipid storage. The results show that liraglutide does not modify glucose consumption or lactate production. However, it increases TAG levels and LD content. These effects are accompanied by an increase in the mRNA levels of the fatty acid transporter FAT/CD36, glycerol-3-phosphate-acyltransferase 3, and perilipins 1 and 4. The participation of the cAMP/PKA signaling pathway was explored. We observed that H89 (a PKA inhibitor) decreases the LD upregulation elicited by liraglutide, and that dibutyryl cAMP increases LD content and the expression of related genes. In summary, liraglutide promotes lipid storage in SCs through the regulation of key regulatory genes involved in FA transport, TAG synthesis, and LD formation. Considering the importance of lipid storage in SC energetic homeostasis maintenance, we postulate that liraglutide might improve the overall energetic status of the seminiferous tubule.
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LEAP2, a liver-derived antagonist for the ghrelin receptor, GHSR1a, counteracts the effects of ghrelin on appetite and energy balance. Less is known about its impact on blood glucose-regulating hormones from pancreatic islets. Here, we investigate whether acyl-ghrelin (AG) and LEAP2 regulate islet hormone release in a cell-type- and sex-specific manner. Hormone content from secretion experiments with isolated islets from male and female mice was measured by radioimmunoassay and mRNA expression by qPCR. LEAP2 enhanced insulin secretion in islets from males (P < 0.01) but not females (P > 0.2), whilst AG-stimulated somatostatin release was significantly reversed by LEAP2 in males (P < 0.001) but not females (P > 0.2). Glucagon release was not significantly affected by AG and LEAP2. Ghsr1a, Ghrelin, Leap2, Mrap2, Mboat4, and Sstr3 islet mRNA expression did not differ between sexes, whereas the SSTR3 antagonist MK4256 enhanced glucose-induced insulin secretion in islets from males only. In control male islets maintained without 17-beta oestradiol (E2), AG exerted an insulinostatic effect (P < 0.05), with a trend towards reversal by LEAP2 (P = 0.06). Both were abolished by 72 h E2 pre-treatment (10 nmol/L, P > 0.2). AG-stimulated somatostatin release was inhibited by LEAP2 from control (P < 0.001) but not E2-treated islets (P > 0.2). LEAP2 and AG did not modulate insulin secretion from MIN6 beta cells and Mrap2 was downregulated (P < 0.05) and Ghsr1a upregulated (P < 0.0001) in islets from Sst−/− mice. Our findings show that AG and LEAP2 regulate insulin and somatostatin release in an opposing and sex-dependent manner, which in males can be modulated by E2. We suggest that regulation of SST release is a key starting point for understanding the role of GHSR1a in islet function and glucose metabolism.
Centre for Systems Health and Integrated Metabolic Research, Department of Biosciences, Nottingham Trent University, Birmingham, UK
Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK
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Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
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Systemic glucocorticoid excess causes several adverse metabolic conditions, most notably Cushing’s syndrome. These effects are amplified by the intracellular enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Here, we determined the less well-characterised effects of glucocorticoid excess, and the contribution of 11β-HSD1 amplification on metabolic rate in mice. Male and female C57BL/6J (wild type, WT) and 11β-HSD1 knockout (11β-HSD1 KO) mice were treated with high-dose corticosterone or a vehicle control for 3 weeks. Indirect calorimetry was conducted during the final week of treatment, with or without fasting, to determine the impact on metabolic rate. We found that corticosterone treatment elevated metabolic rate and promoted carbohydrate utilisation primarily in female WT mice, with effects more pronounced during the light phase. Corticosterone treatment also resulted in greater fat accumulation in female WT mice. Corticosterone induced hyperphagia was identified as a likely causal factor altering the respiratory exchange ratio (RER) but not energy expenditure (EE). Male and female 11β-HSD1 KO mice were protected against these effects. We identify novel metabolic consequences of sustained glucocorticoid excess, identify a key mechanism of hyperphagia, and demonstrate that 11β-HSD1 is required to manifest the full metabolic derangement.
Department of Endocrinology & Diabetes, Princess Alexandra Hospital, Brisbane, Queensland, Australia
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The mineralocorticoid system, comprising the renin-angiotensin-aldosterone system (RAAS) and associated receptors, is traditionally viewed as a regulator of sodium and fluid balance and blood pressure (BP), with the main mineralocorticoid hormone aldosterone acting via the mineralocorticoid receptor (MR) in distal renal tubules. Over the past few decades, there has been a wider understanding of the role of the mineralocorticoid system in regulating both classical BP-dependent and non-BP-dependent systemic effects. Mounting evidence indicates the novel role of the mineralocorticoid system in cardiometabolic health, with excess mineralocorticoid system activity being associated with adiposity, diabetes, insulin resistance and cardiovascular diseases independent of its effect on BP, and RAAS blockade and MR antagonists offering protection against cardiometabolic dysfunction. The metabolic manifestations of mineralocorticoid system overactivation are mainly mediated by their interactions with adipose tissue, which orchestrates energy, lipids, and glucose homeostasis via effects on the functions of brown and white adipocytes and immune cells. Adipose tissue can, in turn, influence mineralocorticoid system activity by harboring its own RAAS system and by releasing mineralocorticoid-secretory factors/adipokines, resulting in further progression of cardiometabolic dysfunction. This article discusses the interplay between the mineralocorticoid system and adipose tissue in the pathophysiology of cardiometabolic diseases.
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Non-alcoholic fatty liver disease (NAFLD) is the fastest-growing cause of liver-associated death globally. Whole-body knockout (KO) of Na+/H+ exchanger 1 (NHE1, SLC9A1) was previously proposed to protect against high-fat diet-induced liver damage; however, mechanistic insight was lacking. The aim of the present work was to address this question in vitro to determine how NHE1, specifically in hepatocytes, impacts lipid overload-induced inflammation, fibrosis, and hepatocyte–hepatic stellate cell (HSC) crosstalk. We induced palmitate (PA)-based steatosis in AML12 and HepG2 hepatocytes; manipulated NHE1 activity pharmacologically and by CRISPR/Cas9-mediated KO and overexpression; and measured intracellular pH (pHi), steatosis-associated inflammatory and fibrotic mediators, and cell death. PA treatment increased NHE1 mRNA levels but modestly reduced NHE1 protein expression and hepatocyte pHi. NHE1 KO in hepatocytes did not alter lipid droplet accumulation but reduced inflammatory signaling (p38 MAPK activity), lipotoxicity (4-HNE accumulation), and apoptosis (poly-ADP-ribose-polymerase-1 (PARP) cleavage). Conditioned medium from PA-treated hepatocytes increased the expression of NHE1 and of the fibrosis regulator tissue inhibitor of matrix metalloproteinases-2 in LX-2 HSCs, in a manner abolished by NHE1 KO in hepatocytes. We conclude that NHE1 is regulated in NAFLD in vitro and contributes to the ensuing damage by aggravating hepatocyte injury and stimulating hepatocyte–HSC crosstalk.
Centre de recherche en reproduction, développement et santé intergénérationnelle, Department of Obstetrics, Gynecology, and Reproduction, Université Laval, Québec, Quebec, Canada
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Centre de recherche en reproduction, développement et santé intergénérationnelle, Department of Obstetrics, Gynecology, and Reproduction, Université Laval, Québec, Quebec, Canada
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The steroidogenic acute regulatory (STAR) protein is an essential cholesterol transporter that shuttles cholesterol from the outer to the inner mitochondrial membrane in the major steroidogenic endocrine organs. It is a key player in the acute regulation of steroid hormone biosynthesis in response to tropic hormone stimulation. Its discovery 30 years ago sparked immediate interest in understanding how STAR action is controlled. Since increased STAR gene expression is a classic feature of the acute regulation of steroidogenesis, a special emphasis was placed on defining the transcriptional regulatory mechanisms that underlie its rapid induction in response to tropic hormone stimulation. These mechanisms include the effects of enhancers, the regulation of chromatin accessibility, the impact of epigenetic factors, and the role of transcription factors. Over the past three decades, understanding the transcription factors that regulate STAR gene expression has been the subject of more than 170 independent scientific publications, making it one of, and if not the best, studied genes in the steroidogenic pathway. This intense research effort has led to the identification of dozens of transcription factors and their related binding sites in STAR 5' flanking (promoter) sequences across multiple species. STAR gene transcription appears to be complex in that a large number of transcription factors have been proposed to interact with either isolated or overlapping regulatory sequences that are tightly clustered over a relatively short promoter region upstream of the STAR transcription start site. Many of these transcription factors appear to work in unique combinatorial codes and are impacted by diverse hormonal and intracellular signaling pathways. This review provides a retrospective overview of the transcription factors proposed to regulate both basal and acute (hormonal) STAR gene expression, and how insights in this area have evolved over the past 30 years.
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Diabetes mellitus disturbs kisspeptin–neurokinin B–dynorphin A (KNDy) neurons in the arcuate nucleus (ARC), which regulate pulsatile luteinizing hormone (LH) secretion in both sexes. However, it remains unclear whether a sex-specific association with the negative effects of diabetes on KNDy neurons exists. Therefore, we examined mRNA expression in KNDy neurons of diabetic male and female rats 7 weeks after streptozotocin (STZ) injection using histochemistry. In gonad-intact rats, the numbers of Kiss1 and Pdyn mRNA-expressing cells in the ARC decreased in an STZ-dose-dependent manner; moreover, no sex-dependent association with STZ treatment was observed. In males, plasma LH and sex steroid levels decreased in diabetic rats. Conversely, those of females did not vary significantly between the control and diabetic rats. Kiss1 expression in the anteroventral periventricular nucleus was slightly affected in diabetic animals, but did not exhibit sex-dependent differences. In gonadectomized rats, the numbers of KNDy mRNA-expressing cells in the ARC and plasma LH levels decreased in diabetic male and female rats; however, sex-dependent differences did not exist. These results demonstrated that a sex-specific association with the negative effects of diabetes on KNDy neurons did not exist. Therefore, the stage of diabetes that induces the suppression of the hypothalamus may not vary according to sex.
National Taiwan University Hospital Primary Aldosteronism Center, Taipei, Taiwan
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Division of Nephrology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
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National Taiwan University Hospital Primary Aldosteronism Center, Taipei, Taiwan
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National Taiwan University Hospital Primary Aldosteronism Center, Taipei, Taiwan
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Aldosterone is a mineralocorticoid hormone involved in controlling electrolyte balance, blood pressure, and cellular signaling. It plays a pivotal role in cardiovascular and metabolic physiology. Excess aldosterone activates mineralocorticoid receptors, leading to subsequent inflammatory responses, increased oxidative stress, and tissue remodeling. Various mechanisms have been reported to link aldosterone with cardiovascular and metabolic diseases. However, mitochondria, responsible for energy generation through oxidative phosphorylation, have received less attention regarding their potential role in aldosterone-related pathogenesis. Excess aldosterone leads to mitochondrial dysfunction, and this may play a role in the development of cardiovascular and metabolic diseases. Aldosterone has the potential to affect mitochondrial structure, function, and dynamic processes, such as mitochondrial fusion and fission. In addition, aldosterone has been associated with the suppression of mitochondrial DNA, mitochondria-specific proteins, and ATP production in the myocardium through mineralocorticoid receptor, nicotinamide adenine dinucleotide phosphate oxidase, and reactive oxygen species pathways. In this review, we explore the mechanisms underlying aldosterone-induced cardiovascular and metabolic mitochondrial dysfunction, including mineralocorticoid receptor activation and subsequent inflammatory responses, as well as increased oxidative stress. Furthermore, we review potential therapeutic targets aimed at restoring mitochondrial function in the context of aldosterone-associated pathologies. Understanding these mechanisms is vital, as it offers insights into novel therapeutic strategies to mitigate the impact of aldosterone-induced mitochondrial dysfunction, thereby potentially improving the outcomes of individuals affected by cardiovascular and metabolic disorders.
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The pancreas suffers from lipotoxicity, which threatens the survival of pancreatic islets. Dual PPAR-alpha(a)/gamma(g) agonism is a promising method for treating type 2 diabetes. This study evaluated the effects of single PPAR-a and PPAR-g or their combined activation on pancreatic islet remodeling, beta-cell proliferation, identity, and maintenance in an experimental obesity model. Fifty three-month-old mice, randomly divided to receive the control (C) or high-fat (HF) diet for ten weeks, were then redivided for a four-week treatment: C, HF, HF-a (received the PPAR-a agonist), HF-g (PPAR-g agonist pioglitazone), and HF-d (PPAR-a/g agonists). The HF group was overweight, had oral glucose intolerance, showed a proinflammatory adipokine profile, exhibited increased alpha and beta cell masses, and islet gene expression compatible with compromised beta cell proliferation and favored dedifferentiation. All treatments reduced body weight, mitigated oral glucose intolerance, and produced an anti-inflammatory adipokine profile, which rescued islet cytoarchitecture, and beta cell function. Principal component analysis (PCA) revealed a shift in the antiapoptotic gene Bcl2 and beta cell proliferation genes (Pax4 and Neurog3) in HF-a. Conversely, HF-g and HF-d benefited from the upregulation of genes related to beta cell function (Fgf21, Glut2, and Glp1r), identity, and maintenance (Pdx1, Neurod1, Mafa, and Nkx6.1). The HF mice were glucose intolerant, showing islet hypertrophy and low beta cell identity-related genes. In contrast, PPAR activation rescued islet structure, and PCA showed that the PPAR-a/g combination was the most effective treatment because it favored beta cell function, identity, and maintenance-related genes, halting the T2DM spectrum in diet-induced obese mice.