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Renea A Taylor, Mitchell G Lawrence, and Gail P Risbridger

There is longstanding interest in the role of androgens in the aetiology of prostate cancer, one of the most common malignancies worldwide. In this review, we reflect on the ways that knowledge of prostate development and hormone action have catalysed advances in the management of patients with prostate cancer. The use of hormone therapies to treat prostate cancer has changed significantly over time, including the emergence of androgen receptor signalling inhibitors (ARSI). These compounds have improved outcomes for patients with castration-resistant prostate cancer, which was once considered ‘androgen-independent’ but is clearly still driven by androgen receptor signalling in many cases. There is also a need for new therapies to manage neuroendocrine prostate cancer, which is not responsive to hormonal agents. One of the major gaps is understanding how treatment-induced neuroendocrine prostate cancer emerges and whether it can be re-sensitised to treatment. Patient-derived models, including patient-derived xenografts (PDXs), will be instrumental in facilitating future discoveries in these areas. Developments in the use of PDXs have been fostered by lessons from the field of endocrinology, such as the role of stroma and hormones in normal and developmental tissues. Thus, there is ongoing reciprocity between the discoveries in endocrinology and advances in prostate cancer research and treatment.

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N Zlocowski, L d V Sosa, B De la Cruz-Thea, C B Guido, M G Martín, J H Mukdsi, A I Torres, and J P Petiti

Interest in epigenetics has gained substantial momentum as a result of their identified role in the regulation of tumor progression as well as their ability to pharmacologically target genes. Pituitary neuroendocrine tumors (PitNETs) tend to be inactivated via epigenetic modification, and although emerging evidence has suggested a role for epigenetic factors in PitNET tumorigenesis, the degree to which these factors may be targeted by new therapeutic strategies still remains poorly understood. The objective of the present study was to examine the participation of the EZH2/H3K27me3 axis in the proliferation of lactotroph tumor cells. We demonstrated that the levels of EZH2 and H3K27me3 were increased in murine experimental prolactin (PRL) tumors with respect to a control pituitary, in contrast with the low p21 mRNA levels encountered, with an H3K27me3 enrichment being observed in its promoter region in a GH3 tumor cell. Furthermore, specific EZH2/H3K27me3 axis inhibition blocked the proliferation of primary tumor cell culture and GH3 cells, thereby making it an attractive therapeutic target for PRL PitNETs.

Open access

Bettina Geidl-Flueck and Philipp A Gerber

Despite the existence of numerous studies supporting a pathological link between fructose consumption and the development of the metabolic syndrome and its sequelae, such as non-alcoholic fatty liver disease (NAFLD), this link remains a contentious issue. With this article, we shed a light on the impact of sugar/fructose intake on hepatic de novo lipogenesis (DNL), an outcome parameter known to be dysregulated in subjects with type 2 diabetes and/or NAFLD. In this review, we present findings from human intervention studies using physiological doses of sugar as well as mechanistic animal studies. There is evidence from both human and animal studies that fructose is a more potent inducer of hepatic lipogenesis than glucose. This is most likely due to the liver’s prominent physiological role in fructose metabolism, which may be disrupted under pathological conditions by increased hepatic expression of fructolytic and lipogenic enzymes. Increased DNL may not only contribute to ectopic fat deposition (i.e. in the liver), but it may also impair several metabolic processes through DNL-related fatty acids (e.g. beta-cell function, insulin secretion, or insulin sensitivity).

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Sy-Ying Leu, Yi-Ling Tsang, Li-Chun Ho, Ching-Chun Yang, Ai-Ning Shao, Chia-Yu Chang, Hui-Kuan Lin, Pei-Jane Tsai, Junne-Ming Sung, and Yau-Sheng Tsai

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an oligomeric complex that assembles in response to exogenous signals of pathogen infection and endogenous danger signals of non-microbial origin. When NLRP3 inflammasome assembly activates caspase-1, it promotes the maturation and release of the inflammatory cytokines interleukin-1B and IL-18. Aberrant activation of the NLRP3 inflammasome has been implicated in various diseases, including chronic inflammatory, metabolic, and cardiovascular diseases. The NLRP3 inflammasome can be activated through several principal mechanisms, including K+ efflux, lysosomal damage, and the production of mitochondrial reactive oxygen species. Interestingly, metabolic danger signals activate the NLRP3 inflammasome to induce metabolic diseases. NLRP3 contains three crucial domains: an N-terminal pyrin domain, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat domain. Protein–protein interactions act as a ‘pedal or brake’ to control the activation of the NLRP3 inflammasome. In this review, we present the mechanisms underlying NLRP3 inflammasome activation after induction by metabolic danger signals or via protein–protein interactions with NLRP3 that likely occur in metabolic diseases. Understanding these mechanisms will enable the development of specific inhibitors to treat NLRP3-related metabolic diseases.

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Ken KY Ho, Anthony J O’Sullivan, and Morton G Burt

The fact that growth hormone (GH) plays an important role in health after the cessation of growth requiring replacement therapy in adult life has only been recognised in the last three decades. This has only been made possible by recombinant technology providing GH supplies required to undertake investigations in the physiology of GH action and the benefits of replacement therapy in patients identified by rigorously validated diagnostic tests for GH deficiency (GHD). Human studies have revealed important regulatory roles in substrate metabolism, sodium homeostasis, body composition, and physical function. GH-induced anabolism is achieved by stimulating amino acid incorporation into protein while reducing oxidative loss simultaneously enhancing lipid utilisation by stimulating fatty acid oxidation and reducing lipid storage. Sodium and fluid retention are enhanced by activating the renin–angiotensin system and distal renal tubular reabsorption. GH stimulates the aerobic and anaerobic energy systems that underpin muscle and cardiovascular function. These pleiotropic actions explain the clinical picture of increased adiposity, reduced lean mass, and impaired physical and psychological function in the GHD adult, all of which are reversed when GH is replaced. Women require a greater replacement dose of GH than men. This is because androgens enhance while oestrogens attenuate GH action. The oestrogen effect is route-dependent, occurring with oral delivery blunting the liver-mediated actions of GH by directly inhibiting GH receptor signalling, global experience spanning over 30 years has attested to the safety, efficacy, and benefits of replacement therapy for adults with GHD.

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Yuta Kasahara, Hiroshi Kishi, Ryo Yokomizo, and Aikou Okamoto

There are many previous reports on the effects of ethanol on physiological function, including reports of elevated blood estrogen levels in women who drank alcohol. However, the mechanism of ethanol's effects on ovarian functions, such as follicle development and hormone secretion, has not been fully clarified. Therefore, in this study, we investigated the impacts of ethanol on these phenomena and their mechanisms using a primary culture system of rat ovarian granulosa cells (GCs). In the present experiment, groups were created in which follicle-stimulating hormone (FSH) or ethanol was added alone or FSH and ethanol were co-added, and mRNA and protein expression in each group was measured for luteinizing hormone receptor (LHR) and sex steroid hormone synthase, as well as for estradiol (E2) production, cAMP production, and FSH receptor (FSHR) internalization rate. The addition of FSH induced mRNA expression of LHR and aromatase, which led to membrane LHR expression and E2 production. The coexistence of ethanol enhanced all these responses. The action of FSH is exerted via cAMP, and the co-addition of ethanol enhanced this cAMP production. Ethanol alone did not induce cAMP production. The enhancing effect of ethanol was also observed for cAMP induced by cholera toxin. Ethanol had no significant effect on the internalization rate of FSHR. In conclusion, ethanol increased FSH-stimulated cAMP production by increasing the activity of adenylyl cyclase, which enhanced FSH actions in rat GCs. Alcohol is an exacerbating factor in several female hormone-related diseases, and the mechanism of ethanol-induced increase in estrogen secretion revealed in this study may be involved in the pathogenesis of these diseases.

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Jitendra Vishwakarma, Keerti Gupta, Juhi Mishra, Asmita Garg, Rafat Malik, Amit Kashyap, Manoj Shukla, Dhirendra Singh, and Sanghamitra Bandyopadhyay

Thyroid hormones (TH) are vital for brain functions, while TH deficiency, i.e. hypothyroidism, induces neurological impairment in children and adults. Cerebellar neuronal apoptosis and motor deficits are crucial events in hypothyroidism; however, the underlying mechanism is less-known. Using a methimazole-treated hypothyroidism rat model, we investigated cerebellar autophagy, growth factor, and apoptotic mechanisms that participate in motor functions. We first identified that methimazole up-regulated cerebellar autophagy, marked by enhanced LC3B-II, Beclin-1, ATG7, ATG5-12, p-AMPKα/AMPKα, and p62 degradation as well as reduced p-AKT/AKT, p-mTOR/mTOR, and p-ULK1/ULK1 in developing and young adult rats. We probed upstream effectors of this abnormal autophagy and detected a methimazole-induced reduction in cerebellar phospho-epidermal growth factor receptor (p-EGFR)/EGFR and heparin-binding EGF-like growth factor (HB-EGF). Here, while a thyroxine-induced TH replenishment alleviated autophagy process and restored HB-EGF/EGFR, HB-EGF treatment regulated AKT-mTOR and autophagy signaling in the cerebellum. Moreover, neurons of the rat cerebellum demonstrated this reduced HB-EGF-dependent increased autophagy in hypothyroidism. We further checked whether the above events were related to cerebellar neuronal apoptosis and motor functions. We detected that comparable to thyroxine, treatment with HB-EGF or autophagy inhibitor, 3-MA, reduced methimazole-induced decrease in Nissl staining and increase in c-Caspase-3 and TUNEL-+ve apoptotic count of cerebellar neurons. Additionally, 3-MA, HB-EGF, and thyroxine attenuated the methimazole-induced diminution in riding time on rota-rod and grip strength for the motor performance of rats. Overall, our study enlightens HB-EGF/EGFR-dependent autophagy mechanism as a key to cerebellar neuronal loss and functional impairments in developmental hypothyroidism, which may be inhibited by HB-EGF and 3-MA treatments, like thyroxine.

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Mari van de Vyver

Inflammation is part of the body’s innate immune response and is an essential process that not only defends against harmful bacteria and pathogens but also plays a key role in the maintenance and repair of tissues. Under pathological conditions, there is bilateral crosstalk between immune regulation and aberrant metabolism resulting in persistent inflammation in the absence of infection. This phenomenon is referred to as sterile metabolic inflammation (metainflammation) and occurs if the initiating stimulus is not removed or if the resolution process is disrupted. Disruption of this tightly regulated immune response and its failure to resolve as is evident in metabolic disorders is not only associated with disease progression but also leads to immune senescence and should not be neglected in the clinical management of patients. This review gives an overview of the mechanisms underlying chronic metabolic inflammation, the aberrant metabolic activation of innate immune cells (neutrophils, macrophages, mast cells, dendritic cells), and its role in disease progression using obesity–diabetes as a prime example. Addressing the underlying subclinical metabolic inflammation in addition to achieving glucose control may contribute significantly towards therapeutic interventions aimed at preventing the onset of co-morbidities in diabetic patients.

Free access

Samuel M Lee, Jose Muratalla, Marta Sierra-Cruz, and Jose Cordoba-Chacon

Peroxisome proliferator-activated receptor γ (PPARγ) belongs to a family of nuclear receptors that could serve as lipid sensors. PPARγ is the target of a group of insulin sensitizers called thiazolidinediones (TZDs) which regulate the expression of genes involved in glucose and lipid metabolism as well as adipokines that regulate metabolic function in other tissues. Non-alcoholic fatty liver disease (NAFLD) has a high prevalence worldwide and is even higher in patients with obesity and insulin resistance. TZD-mediated activation of PPARγ could serve as a good treatment for NAFLD because TZDs have shown anti-fibrogenic and anti-inflammatory effectsin vitro and increase insulin sensitivity in peripheral tissues which improves liver pathology. However, mechanistic studies in mouse models suggest that the activation of PPARγ in hepatocytes might reduce or limit the therapeutic potential of TZD against NAFLD. In this review, we briefly describe the short history of PPAR isoforms, the relevance of their expression in different tissues, as well as the pathogenesis and potential therapeutics for NAFLD. We also discuss some evidence derived from mouse models that could be useful for endocrinologists to assess tissue-specific roles of PPARs, complement reverse endocrinology approaches, and understand the direct role that PPARγ has in hepatocytes and non-parenchymal cells.

Free access

Jasleen Kaur and Elizabeth R Seaquist

Glucagon is secreted by the pancreatic alpha cell and has long been known to oppose insulin action. A lyophilized form of the hormone has been available to treat episodes of insulin-induced hypoglycemia in insulin-treated people with diabetes for decades, but the difficulty of use was a barrier to widespread utilization. Newer formulations of glucagon are stable at room temperature in single-use devices that many caregivers find are easier to use than the original glucagon emergency kit. In this review , we will review what is known about the role of glucagon in normal physiology and diabetes and then discuss how the research in this area has been translated into treatment for metabolic conditions.