17beta-Estradiol modulates apoptosis in pancreatic beta-cells by specific involvement of the sulfonylurea receptor (SUR) isoform SUR1

Gluco-regulation & type 2 diabetes: entrenched misconceptions updated to new governing principles for gold standard management

Our understanding of type 2 diabetes (T2D) has evolved dramatically. Advances have upended entrenched dogmas pertaining to the onset and progression of T2D, beliefs that have prevailed from the early era of diabetes research-and continue to populate our medical textbooks and continuing medical education materials. This review article highlights key insights that lend new governing principles for gold standard management of T2D. From the historical context upon which old beliefs arose to new findings, this article outlines evidence and perspectives on beta cell function, the underlying defects in glucoregulation, the remediable nature of T2D, and, the rationale supporting the shift to complication-centric prescribing. Practical approaches translate this rectified understanding of T2D into strategies that fill gaps in current management practices of prediabetes through late type 2 diabetes.

Effect of resveratrol in gestational diabetes mellitus and its complications

The incidence rate of diabetes in pregnancy is about 20%, and diabetes in pregnancy will have a long-term impact on the metabolic health of mothers and their offspring. Mothers may have elevated blood glucose, which may lead to blood pressure disease, kidney disease, decreased resistance and secondary infection during pregnancy. The offspring may suffer from abnormal embryonic development, intrauterine growth restriction, obesity, autism, and other adverse consequences. Resveratrol (RSV) is a natural polyphenol compound, which is found in more than 70 plant species and their products, such as Polygonum cuspidatum, seeds of grapes, peanuts, blueberries, bilberries, and cranberries. Previous studies have shown that RSV has a potential beneficial effect on complex pregnancy, including improving the indicators of diabetes and pregnancy diabetes syndrome. This article has reviewed the molecular targets and signaling pathways of RSV, including AMP-activated protein kinase, mitogen-activated protein kinases, silent information regulator sirtuin 1, miR-23a-3p, reactive oxygen species, potassium channels and CX3C chemokine ligand 1, and the effect of RSV on gestational diabetes mellitus (GDM) and its complications. RSV improves the indicators of GDM by improving glucose metabolism and insulin tolerance, regulating blood lipids and plasma adipokines, and modulating embryonic oxidative stress and apoptosis. Furthermore, RSV can ameliorate the GDM complications by reducing oxidative stress, reducing the effects on placentation, reducing the adverse effects on embryonic development, reducing offspring's healthy risk, and so on. Thus, this review is of great significance for providing more options and possibilities for further research on medication of gestational diabetes.

Potassium Channels as Therapeutic Targets in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a devastating disease with high morbidity and mortality. Deleterious remodeling in the pulmonary arterial system leads to irreversible arterial constriction and elevated pulmonary arterial pressures, right heart failure, and eventually death. The difficulty in treating PAH stems in part from the complex nature of disease pathogenesis, with several signaling compounds known to be involved (e.g., endothelin-1, prostacyclins) which are indeed targets of PAH therapy. Over the last decade, potassium channelopathies were established as novel causes of PAH. More specifically, loss-of-function mutations in the KCNK3 gene that encodes the two-pore-domain potassium channel KCNK3 (or TASK-1) and loss-of-function mutations in the ABCC8 gene that encodes a key subunit, SUR1, of the ATP-sensitive potassium channel (KATP) were established as the first two potassium channelopathies in human cohorts with pulmonary arterial hypertension. Moreover, voltage-gated potassium channels (Kv) represent a third family of potassium channels with genetic changes observed in association with PAH. While other ion channel genes have since been reported in association with PAH, this review focuses on KCNK3, KATP, and Kv potassium channels as promising therapeutic targets in PAH, with recent experimental pharmacologic discoveries significantly advancing the field.

Potassium (K+) channels in the pulmonary vasculature: Implications in pulmonary hypertension Physiological, pathophysiological and pharmacological regulation

The large K⁺ channel functional diversity in the pulmonary vasculature results from the multitude of genes expressed encoding K⁺ channels, alternative RNA splicing, the post-transcriptional modifications, the presence of homomeric or heteromeric assemblies of the pore-forming α-subunits and the existence of accessory β-subunits modulating the functional properties of the channel. K⁺ channels can also be regulated at multiple levels by different factors controlling channel activity, trafficking, recycling and degradation. The activity of these channels is the primary determinant of membrane potential (Em) in pulmonary artery smooth muscle cells (PASMC), providing an essential regulatory mechanism to dilate or contract pulmonary arteries (PA). K⁺ channels are also expressed in pulmonary artery endothelial cells (PAEC) where they control resting Em, Ca²⁺ entry and the production of different vasoactive factors. The activity of K⁺ channels is also important in regulating the population and phenotype of PASMC in the pulmonary vasculature, since they are involved in cell apoptosis, survival and proliferation. Notably, K⁺ channels play a major role in the development of pulmonary hypertension (PH). Impaired K⁺ channel activity in PH results from: 1) loss of function mutations, 2) downregulation of its expression, which involves transcription factors and microRNAs, or 3) decreased channel current as a result of increased vasoactive factors (e.g., hypoxia, 5-HT, endothelin-1 or thromboxane), exposure to drugs with channel-blocking properties, or by a reduction in factors that positively regulate K⁺ channel activity (e.g., NO and prostacyclin). Restoring K⁺ channel expression, its intracellular trafficking and the channel activity is an attractive therapeutic strategy in PH.

Approved LXR agonists exert unspecific effects on pancreatic β-cell function

Novel agonists of the nuclear liver-X-receptor (LXR) are designed to treat metabolic disorders or cancer. The rationale to develop these new drugs is based on promising results with established LXR agonist like T0901317 and GW3965. LXRα and LXRβ are expressed in β-cells, and expression is increased by T0901317. The aim of the present study was to evaluate whether effects of these drugs on β-cell function are specific and reliably linked to LXR activation. T0901317 and GW3965, widely used as specific LXR agonists, show rapid, non-genomic effects on stimulus-secretion coupling of mouse pancreatic β-cells at low µM concentrations. T0901317 lowered the cytosolic Ca²⁺ concentration, reduced or completely inhibited action potentials, and decreased insulin secretion. GW3965 exerted similar effects on insulin secretion. T0901317 affected the production of reactive oxygen species and ATP. The involvement of the classical nuclear LXRs in T0901317- and GW3965-mediated effects in β-cells could be ruled out using LXRα, LXRβ and double knockout mice. Our results strongly suggest that LXR agonists, that are considered to be specific for this receptor, interfere with mitochondrial metabolism and metabolism-independent processes in β-cells. Thus, it is indispensable to test novel LXR agonists accompanying to ongoing clinical trials for acute and chronic effects on cell function in cellular systems and/or animal models lacking classical LXRs.

Protective role of 17β-estradiol on tumor necrosis factor-α-induced apoptosis in human nucleus pulposus cells

The molecular mechanisms underlying protection and pathogenesis in spinal degenerative diseases remain unclear. Tumor necrosis factor-α (TNF-α) has been demonstrated to induce apoptosis of intervertebral disc (IVD) cells during IVD degeneration, and 17β-estradiol (17β-E2) has a protective effect against IVD cell apoptosis. However, the underlying molecular mechanism by which 17β-E2 protects nucleus pulposus (NP) cells remains to be investigated. The aim of the present study was to evaluate whether 17β-E2 modulates apoptosis of human NP cells induced by TNF-α. In addition, the concentration-response effect of 17β-E2 on human NP cells was investigated. Human NP cells were cultured in complete medium, which was replaced every three days until the culture was ~80% confluent. Cells were treated with 100 ng/ml TNF-α for 48 h, with or without pretreatment with various concentrations of 17β-E2, and ICI 182,780, for 30 min. Morphologic alterations characteristic of apoptosis were observed by inverted phase-contrast microscopy and Hoechst 33258 staining; the apoptosis rate was analyzed by flow cytometry. A Cell Counting kit-8 assay was used to assess cell proliferation. Furthermore, caspase-3 activity was determined and proteins associated with apoptosis were analyzed by western blotting. The level of apoptosis and caspase-3 activity in human NP cells increased, whereas proliferation and the expression of poly ADP-ribose polymerase decreased following TNF-α treatment. These effects of TNF-α were abolished by pretreatment with 17β-E2 in a concentration-dependent manner. The results of the present study indicated that 17β-E2 serves a critical role in the survival of degenerative human NP cells.

Effects of Bisphenol A on ion channels: Experimental evidence and molecular mechanisms

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) produced in huge quantities in the manufacture of polycarbonate plastics and epoxy resins. It is present in most humans in developed countries, acting as a xenoestrogen and it is considered an environmental risk factor associated to several diseases. Among the whole array of identified mechanisms by which BPA can interfere with physiological processes in living organisms, changes on ion channel activity is one of the most poorly understood. There is still little evidence about BPA regulation of ion channel expression and function. However, this information is key to understand how BPA disrupts excitable and non-excitable cells, including neurons, endocrine cells and muscle cells. This report is the result of a comprehensive literature review on the effects of BPA on ion channels. We conclude that there is evidence to say that these important molecules may be key end-points for EDCs acting as xenoestrogens. However, more research on channel-mediated BPA effects is needed. Particularly, mechanistic studies to unravel the pathophysiological actions of BPA on ion channels at environmentally relevant doses.

STRATEGY OF PROGRAMMED CELL DEATH IN PROKARYOTES

Programmed cell death (PCD) was first studied in eukaryotic organisms. This system also operates in the development life cycle of prokaryotes. The system PCD in microorganisms is activated a wide range of signals in response to the stresses associated with adverse environmental conditions or exposure to antibacterial agents. The results of numerous studies in the past decade allow considering the system PCD in prokaryotes as an evolutionary conservation of the species. These results significantly expanded understanding of the role of PCD in microorganisms and opened a number of important areas of research of the morphological and molecular genetic approaches to the study of death strategies for the survival in bacterial populations. The purpose of the review is to summarize the morphological and molecular genetic characteristics of PCD in prokaryotes which are real manifestations of the mechanisms of this phenomenon. 

Dehydroepiandrosterone, its metabolites and ion channels

This review is focused on the physiological and pathophysiological relevance of steroids influencing the activities of the central and peripheral nervous systems with regard to their concentrations in body fluids and tissues in various stages of human life like the fetal development or pregnancy. The data summarized in this review shows that DHEA and its unconjugated and sulfated metabolites are physiologically and pathophysiologically relevant in modulating numerous ion channels and participate in vital functions of the human organism. DHEA and its unconjugated and sulfated metabolites including 5α/β-reduced androstane steroids participate in various physiological and pathophysiological processes like the management of GnRH cyclic release, regulation of glandular and neurotransmitter secretions, maintenance of glucose homeostasis on one hand and insulin insensitivity on the other hand, control of skeletal muscle and smooth muscle activities including vasoregulation, promotion of tolerance to ischemia and other neuroprotective effects. In respect of prevalence of steroid sulfates over unconjugated steroids in the periphery and the opposite situation in the CNS, the sulfated androgens and androgen metabolites reach relevance in peripheral organs. The unconjugated androgens and estrogens are relevant in periphery and so much the more in the CNS due to higher concentrations of most unconjugated steroids in the CNS tissues than in circulation and peripheral organs. This article is part of a Special Issue entitled "Essential role of DHEA".

PBDE-47 exposure causes gender specific effects on apoptosis and heat shock protein expression in marine medaka, Oryzias melastigma

Marine medaka (Oryzias melastigma) was fed with a low and high dose of dietary 2,2',4,4'-tetra-bromodiphenyl ether (PBDE-47), over 21 days. Gender specific changes in caspases 3 and 8 in medaka were found as activities in male medaka were significantly increased in both liver and muscle at both low and high exposure levels whereas caspase activity in female medaka tissue remained unchanged. Results of HSP90 and HSP70 immunoassays also showed gender specific related changes as both HSP families were unchanged in liver and muscle of male medaka but significantly increased in liver and muscle of female medaka, following PBDE-47 exposure. The gender specific effects of PBDE-47 on HSP expression profiles could not be explained by inherent differences in the heat shock response of male and female marine medaka, as the HSP profiles in liver and muscle, induced by acute heat shock, were similar in both sexes. The findings from this study provide evidence that PBDE-47 can cause gender specific modulatory effects on mechanisms critical to the apoptotic cascade as well as HSP regulation and expression.

Neuroprotective effects of 17β-estradiol associate with KATP in rat brain

Previous studies have indicated that estrogen protects the brain from ischemic damage and regulates K(ATP) channel activity; the present study was designed to address the involvement of K(ATP) channels in the neuroprotective effects of estrogen in focal cerebral ischemia: in experiment 1, K(ATP) mRNA and protein in the cortices of rats were compared among groups of ovariectomized rats (Ovx-1), Sham-operated rats (Sham-1), and ovariectomized rats administered 17β-estradiol (Estr-1). In experiment 2, neurobehavioral scores and infarct volume of rats were evaluated after middle cerebral artery occlusion in ovariectomized rats (Ovx-2), Sham-operated rats (Sham-2), ovariectomized female rats administered 17β-estradiol (Estr-2), and ovariectomized rats administered both 17β-estradiol and stereotactic injections of glibenclamide (Estr+G). Our results showed that the Kir6.2 and SUR1 mRNA and protein levels in the brain cortices of female ovariectomized rats were lower than those in Sham rats. However, the expression levels of Kir6.2 and SUR1 in brain cortices of ovariectomized rats recovered after supplementation with 17β-estradiol. The protective effects of 17β-estradiol were abolished by glibenclamide, a K(ATP) channel blocker. This indicates that estradiol significantly upregulates the expression of K(ATP) channel subunits and channel activity in the brain cortices of ovariectomized rats. This regulation is associated with the neuroprotective effects of estradiol.

PDIp is a major intracellular oestrogen-storage protein that modulates tissue levels of oestrogen in the pancreas

E(2) (17β-oestradiol), a female sex hormone, has important biological functions in a woman's body. The pancreas, often considered a non-classical E(2)-targeting organ, is known to be functionally regulated by E(2), but little is known about how oestrogen actions are regulated in this organ. In the present study we report that PDIp (pancreas-specific protein disulfide isomerase), a protein-folding catalyst, can act as a major intracellular E(2) storage protein in a rat model to modulate the pancreatic tissue level, metabolism and action of E(2). The purified endogenous PDIp from both rat and human pancreatic tissues can bind E(2) with a K(d) value of approximately 150 nM. The endogenous PDIp-bound E(2) accounts for over 80% of the total protein-bound E(2) present in rat and human pancreatic tissues, and this binding protects E(2) from metabolic disposition and prolongs its duration of action. Importantly, we showed in ovariectomized female rats that the E(2) level in the pancreas reaches its highest level (9-fold increase over its basal level) at 24-48 h after a single injection of E(2), and even at 96 h its level is still approximately 5-fold higher. In contrast, the E(2) level in the uterus quickly returns to its basal level at 48 h after reaching its maximal level (approximately 2-fold increase) at 24 h. Taken together, these results show for the first time that PDIp is a predominant intracellular oestrogen storage protein in the pancreas, which offers novel mechanistic insights into the accumulation and action of oestrogen inside pancreatic cells.

The common C49620T polymorphism in the sulfonylurea receptor gene SUR1 (ABCC8) in patients with gestational diabetes and subsequent glucose metabolism abnormalities

AIM

The aim of this study is to investigate the relationship between the common C49620T polymorphism in the sulfonylurea receptor (SUR1) gene and glucose metabolism, β-cell secretory function and insulin resistance in women with a history of gestational diabetes (GDM).

MATERIAL AND METHODS

Study group included 199 women, diagnosed GDM within the last 5-12 years and control group of comparable 50 women in whom GDM was excluded during pregnancy. Blood glucose and insulin levels were measured during oral glucose tolerance test. Indices of insulin resistance (HOMA-IR) and β-cell function (HOMA %B) were calculated. In all patients, the C49620T polymorphism in intron 15 of the SUR1 gene was determined.

RESULTS

The distribution of the studied polymorphism in the two groups did not differ from each other (χ(2) = 0.34, P = 0.8425). No association between the distribution of polymorphisms and coexisting glucose metabolism disorders (χ(2) = 7,13, P = 0, 3043) was found. No association was also observed between the polymorphism and HOMA %B or HOMA-IR.

CONCLUSIONS

The polymorphism C49620T in the SUR1 gene is not associated with insulin resistance and/or insulin secretion in women with a history of GDM and does not affect the development of GDM, or the development of glucose intolerance in the studied population.

Role of 17β-estradiol and testosterone in apoptosis

17β-Estradiol (E2) and Testosterone (T) exert actions in most animal tissues, in addition to the reproductive system. Thus, both sex steroid hormones affect growth and different cell functions in several organs. Accordingly, the nuclear estrogen (ER) and androgen (AR) receptors are ubiquitously expressed. Moreover, ER and AR may have non-classical intracellular localizations, e.g. plasma membrane, mitochondria and endoplasmic reticulum, raising additional complexity to the functional roles of E2 and T. In addition to the modulation of gene transcription by direct interaction with their cognate nuclear receptors, the steroids can rapidly activate signaling pathways by a non-genomic mechanism mediated by receptors identical to or different from known steroid receptors. Among various functions, E2 and T can regulate apoptosis through those pathways. In mitochondria, the presence of ER and AR and actions of estrogen and androgen have been shown, in keeping with the organelle being a control point of apoptosis. The most recurrent action for each steroid hormone is the protection of mitochondria against different insults, resulting in antiapoptosis. This review summarizes the molecular basis of the modulation of programmed cell death by E2 and T in several tissues.

Regulation of K(ATP) channel by 17β-estradiol in pancreatic β-cells

ATP-sensitive potassium channels (K(ATP)) regulate electrical activity and insulin secretion in pancreatic β-cells. When glucose concentration increases, the [ATP]/[ADP] ratio rises closing K(ATP) channels, and the membrane potential depolarizes, triggering insulin secretion. This pivotal role of K(ATP) channels is used not only by glucose but also by neurotransmitters, hormones and other physiological agents to modulate electrical and secretory β-cell response. In recent years, it has been demonstrated that estrogens and estrogen receptors are involved in glucose homeostasis, and that they can modulate the electrical activity and insulin secretion of pancreatic β-cells. The hormone 17β-estradiol (E2), at physiological levels, is implicated in maintaining normal insulin sensitivity for β-cell function. Long term exposure to E2 increases insulin content, insulin gene expression and insulin release via the estrogen receptor α (ERα), while rapid responses to E2 can regulate K(ATP) channels increasing cGMP levels through the estrogen receptor β (ERβ) and type A guanylate cyclase receptor (GC-A). This review summarizes the main actions of 17β-estradiol on K(ATP) channels and the subsequent insulin release in pancreatic β-cells.

Phytochemicals in the oncology setting

Phytochemicals--the bioactive compounds found in plants--not only hold historical significance in various medical traditions, but also form the basis of many modern-day drugs. Phytochemicals are often used for primary disease prevention or as adjuncts to conventional therapies--despite uncertain effectiveness or safety. On the other hand, phytochemicals have given rise to numerous conventional drugs, which are widely used in mainstream medicine and compose the primary therapeutic strategies for numerous conditions (including cancer). In this review, we will discuss general safety considerations for integrating phytochemicals in the oncology setting. The supportive evidence and safety concerns of popular plant-based cancer therapies will also be summarized. Finally, a brief overview of the established and emerging anticancer drugs with botanical origins will be provided.

Environmental pollutants and type 2 diabetes: a review of mechanisms that can disrupt beta cell function

The prevalence of diabetes mellitus is currently at epidemic proportions and it is estimated that it will increase even further over the next decades. Although genetic predisposition and lifestyle choices are commonly accepted reasons for the occurrence of type 2 diabetes, it has recently been suggested that environmental pollutants are additional risk factors for diabetes development and this review aims to give an overview of the current evidence for this. More specifically, because of the crucial role of pancreatic beta cells in the development and progression of type 2 diabetes, the present work summarises the known effects of several compounds on beta cell function with reference to mechanistic studies that have elucidated how these compounds interfere with the insulin secreting capacity of beta cells. Oestrogenic compounds, organophosphorus compounds, persistent organic pollutants and heavy metals are discussed, and a critical reflection on the relevance of the concentrations used in mechanistic studies relative to the levels found in the human population is given. It is clear that some environmental pollutants affect pancreatic beta cell function, as both epidemiological and experimental research is accumulating. This supports the need to develop a solid and structured platform to fully explore the diabetes-inducing potential of pollutants.

Rapid regulation of K(ATP) channel activity by 17{beta}-estradiol in pancreatic {beta}-cells involves the estrogen receptor {beta} and the atrial natriuretic peptide receptor

The ATP-sensitive potassium (K(ATP)) channel is a key molecule involved in glucose-stimulated insulin secretion. The activity of this channel regulates beta-cell membrane potential, glucose- induced [Ca(2+)](i) signals, and insulin release. In this study, the rapid effect of physiological concentrations of 17beta-estradiol (E2) on K(ATP) channel activity was studied in intact beta-cells by use of the patch-clamp technique. When cells from wild-type (WT) mice were used, 1 nm E2 rapidly reduced K(ATP) channel activity by 60%. The action of E2 on K(ATP) channel was not modified in beta-cells from ERalpha-/- mice, yet it was significantly reduced in cells from ERbeta-/- mice. The effect of E2 was mimicked by the ERbeta agonist 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN). Activation of ERbeta by DPN enhanced glucose-induced Ca(2+) signals and insulin release. Previous evidence indicated that the acute inhibitory effects of E2 on K(ATP) channel activity involve cyclic GMP and cyclic GMP-dependent protein kinase. In this study, we used beta-cells from mice with genetic ablation of the membrane guanylate cyclase A receptor for atrial natriuretic peptide (also called the atrial natriuretic peptide receptor) (GC-A KO mice) to demonstrate the involvement of this membrane receptor in the rapid E2 actions triggered in beta-cells. E2 rapidly inhibited K(ATP) channel activity and enhanced insulin release in islets from WT mice but not in islets from GC-A KO mice. In addition, DPN reduced K(ATP) channel activity in beta-cells from WT mice, but not in beta-cells from GC-A KO mice. This work unveils a new role for ERbeta as an insulinotropic molecule that may have important physiological and pharmacological implications.

Sulfonylurea receptor 1 subunits of ATP-sensitive potassium channels and myocardial ischemia/reperfusion injury

K(ATP) channels are generally cardioprotective under conditions of metabolic impairment, consisting of pore-forming (Kir6.1 and/or Kir6.2) and sulphonylurea-binding, modulatory subunits [sulfonylurea receptor (SUR) 1, 2A, or 2B]. Cardiovascular K(ATP) channels are generally thought to consist of Kir6.2/SUR2A subunits (in the case of heart muscle) or Kir6.1/SUR2B subunits (smooth muscle), whereas SUR1-containing channels have well-documented roles in pancreatic insulin release. Recent data, however, demonstrated the presence of SUR1 subunits in mouse cardiac tissue (particularly in atria) and a surprising protection from myocardial ischemia/reperfusion in SUR1-null mice. Here, we review some of the extra-pancreatic roles assigned to SUR1 subunits and consider whether these might be involved in the sequelae of ischemia/reperfusion.

The role of oestrogens in the adaptation of islets to insulin resistance

Pregnancy is characterized by peripheral insulin resistance, which is developed in parallel with a plasma increase of maternal hormones; these include prolactin, placental lactogens, progesterone and oestradiol among others. Maternal insulin resistance is counteracted by the adaptation of the islets of Langerhans to the higher insulin demand. If this adjustment is not produced, gestational diabetes may be developed. The adaptation process of islets is characterized by an increase of insulin biosynthesis, an enhanced glucose-stimulated insulin secretion (GSIS) and an increase of beta-cell mass. It is not completely understood why, in some individuals, beta-cell mass and function fail to adapt to the metabolic demands of pregnancy, yet a disruption of the beta-cell response to maternal hormones may play a key part. The role of the maternal hormone 17beta-oestradiol (E2) in this adaptation process has been largely unknown. However, in recent years, it has been demonstrated that E2 acts directly on beta-cells to increase insulin biosynthesis and to enhance GSIS through different molecular mechanisms. E2 does not increase beta-cell proliferation but it is involved in beta-cell survival. Classical oestrogen receptors ERalpha and ERbeta, as well as the G protein-coupled oestrogen receptor (GPER) seem to be involved in these adaptation changes. In addition, as the main production of E2 in post-menopausal women comes from the adipose tissue, E2 may act as a messenger between adipocytes and islets in obesity.