Epigenetic regulation of glucose transporter 4 by estrogen receptor β

Arsenic in brown rice: do the benefits outweigh the risks?

Brown rice has been advocated for as a healthier alternative to white rice. However, the concentration of arsenic and other pesticide contaminants is greater in brown rice than in white. The potential health risks and benefits of consuming more brown rice than white rice remain unclear; thus, mainstream nutritional messaging should not advocate for brown rice over white rice. This mini-review aims to summarize the most salient concepts related to dietary arsenic exposure with emphasis on more recent findings and provide consumers with evidence of both risks and benefits of consuming more brown rice than white rice. Despite risk-benefit assessments being a challenging new frontier in nutrition, researchers should pursue an assessment to validate findings and solidify evidence. In the interim, consumers should be cognizant that the dose of arsenic exposure determines its toxicity, and brown rice contains a greater concentration of arsenic than white rice.

Glucose transporter 4: Insulin response mastermind, glycolysis catalyst and treatment direction for cancer progression

The glucose transporter family (GLUT) consists of fourteen members. It is responsible for glucose homeostasis and glucose transport from the extracellular space to the cell cytoplasm to further cascade catalysis. GLUT proteins are encoded by the solute carrier family 2 (SLC2) genes and are members of the major facilitator superfamily of membrane transporters. Moreover, different GLUTs also have their transporter kinetics and distribution, so each GLUT member has its uniqueness and importance to play essential roles in human physiology. Evidence from many studies in the field of diabetes showed that GLUT4 travels between the plasma membrane and intracellular vesicles (GLUT4-storage vesicles, GSVs) and that the PI3K/Akt pathway regulates this activity in an insulin-dependent manner or by the AMPK pathway in response to muscle contraction. Moreover, some published results also pointed out that GLUT4 mediates insulin-dependent glucose uptake. Thus, dysfunction of GLUT4 can induce insulin resistance, metabolic reprogramming in diverse chronic diseases, inflammation, and cancer. In addition to the relationship between GLUT4 and insulin response, recent studies also referred to the potential upstream transcription factors that can bind to the promoter region of GLUT4 to regulating downstream signals. Combined all of the evidence, we conclude that GLUT4 has shown valuable unknown functions and is of clinical significance in cancers, which deserves our in-depth discussion and design compounds by structure basis to achieve therapeutic effects. Thus, we intend to write up a most updated review manuscript to include the most recent and critical research findings elucidating how and why GLUT4 plays an essential role in carcinogenesis, which may have broad interests and impacts on this field.

Sexual Dimorphism in Adipose-Hypothalamic Crosstalk and the Contribution of Aryl Hydrocarbon Receptor to Regulate Energy Homeostasis

There are fundamental sex differences in the regulation of energy homeostasis. Better understanding of the underlying mechanisms of energy balance that account for this asymmetry will assist in developing sex-specific therapies for sexually dimorphic diseases such as obesity. Multiple organs, including the hypothalamus and adipose tissue, play vital roles in the regulation of energy homeostasis, which are regulated differently in males and females. Various neuronal populations, particularly within the hypothalamus, such as arcuate nucleus (ARC), can sense nutrient content of the body by the help of peripheral hormones such leptin, derived from adipocytes, to regulate energy homeostasis. This review summarizes how adipose tissue crosstalk with homeostatic network control systems in the brain, which includes energy regulatory regions and the hypothalamic–pituitary axis, contribute to energy regulation in a sex-specific manner. Moreover, development of obesity is contingent upon diet and environmental factors. Substances from diet and environmental contaminants can exert insidious effects on energy metabolism, acting peripherally through the aryl hydrocarbon receptor (AhR). Developmental AhR activation can impart permanent alterations of neuronal development that can manifest a number of sex-specific physiological changes, which sometimes become evident only in adulthood. AhR is currently being investigated as a potential target for treating obesity. The consensus is that impaired function of the receptor protects from obesity in mice. AhR also modulates sex steroid receptors, and hence, one of the objectives of this review is to explain why investigating sex differences while examining this receptor is crucial. Overall, this review summarizes sex differences in the regulation of energy homeostasis imparted by the adipose–hypothalamic axis and examines how this axis can be affected by xenobiotics that signal through AhR.

A Mixture of Endocrine Disrupting Chemicals Associated with Lower Birth Weight in Children Induces Adipogenesis and DNA Methylation Changes in Human Mesenchymal Stem Cells

Endocrine Disrupting Chemicals (EDCs) are man-made compounds that alter functions of the endocrine system. Environmental mixtures of EDCs might have adverse effects on human health, even though their individual concentrations are below regulatory levels of concerns. However, studies identifying and experimentally testing adverse effects of real-life mixtures are scarce. In this study, we aimed at evaluating an epidemiologically identified EDC mixture in an experimental setting to delineate its cellular and epigenetic effects. The mixture was established using data from the Swedish Environmental Longitudinal Mother and child Asthma and allergy (SELMA) study where it was associated with lower birth weight, an early marker for prenatal metabolic programming. This mixture was then tested for its ability to change metabolic programming of human mesenchymal stem cells. In these cells, we assessed if the mixture induced adipogenesis and genome-wide DNA methylation changes. The mixture increased lipid droplet accumulation already at concentrations corresponding to levels measured in the pregnant women of the SELMA study. Furthermore, we identified differentially methylated regions in genes important for adipogenesis and thermogenesis. This study shows that a mixture reflecting human real-life exposure can induce molecular and cellular changes during development that could underlie adverse outcomes.

Metabolic and Epigenetic Regulation by Estrogen in Adipocytes

Sex hormones contribute to differences between males and females in body fat distribution and associated disease risk. Higher concentrations of estrogens are associated with a more gynoid body shape and with more fat storage on hips and thighs rather than in visceral depots. Estrogen-mediated protection against visceral adiposity is shown in post-menopausal women with lower levels of estrogens and the reduction in central body fat observed after treatment with hormone-replacement therapy. Estrogen exerts its physiological effects via the estrogen receptors (ERα, ERβ and GPR30) in target cells, including adipocytes. Studies in mice indicate that estrogen protects against adipose inflammation and fibrosis also before the onset of obesity. The mechanisms involved in estrogen-dependent body fat distribution are incompletely understood, but involve, e.g., increased mTOR signaling and suppression of autophagy and adipogenesis/lipid storage. Estrogen plays a key role in epigenetic regulation of adipogenic genes by interacting with enzymes that remodel DNA methylation and histone tail post-translational modifications. However, more studies are needed to map the differential epigenetic effects of ER in different adipocyte subtypes, including those in subcutaneous and visceral adipose tissues. We here review recent discoveries of ER-mediated transcriptional and epigenetic regulation in adipocytes, which may explain sexual dimorphisms in body fat distribution and obesity-related disease risk.

Endometrial Glucose Transporters in Health and Disease

Pregnancy loss is a frequent occurrence during the peri-implantation period, when there is high glucose demand for embryonic development and endometrial decidualization. Glucose is among the most essential uterine fluid components required for those processes. Numerous studies associate abnormal glucose metabolism in the endometrium with a higher risk of adverse pregnancy outcomes. The endometrium is incapable of synthesizing glucose, which thus must be delivered into the uterine lumen by glucose transporters (GLUTs) and/or the sodium-dependent glucose transporter 1 (SGLT1). Among the 26 glucose transporters (14 GLUTs and 12 SGLTs) described, 10 (9 GLUTs and SGLT1) are expressed in rodents and 8 (7 GLUTs and SGLT1) in the human uterus. This review summarizes present knowledge on the most studied glucose transporters in the uterine endometrium (GLUT1, GLUT3, GLUT4, and GLUT8), whose data regarding function and regulation are still lacking. We present the recently discovered SGLT1 in the mouse and human endometrium, responsible for controlling glycogen accumulation essential for embryo implantation. Moreover, we describe the epigenetic regulation of endometrial GLUTs, as well as signaling pathways included in uterine GLUT’s expression. Further investigation of the GLUTs function in different endometrial cells is of high importance, as numerous glucose transporters are associated with infertility, polycystic ovary syndrome, and gestational diabetes.

Exploring the Hereditary Nature of Migraine

Migraine is a common neurological disorder which affects 15-20% of the population; it has a high socioeconomic impact through treatment and loss of productivity. Current forms of diagnosis are primarily clinical and can be difficult owing to comorbidity and symptom overlap with other neurological disorders. As such, there is a need for better diagnostic tools in the form of genetic testing. Migraine is a complex disorder, encompassing various subtypes, and has a large genetic component. Genetic studies conducted on rare monogenic subtypes, including familial hemiplegic migraine, have led to insights into its pathogenesis via identification of causal mutations in three genes (CACNA1A, ATP1A2 and SCN1A) that are involved in transport of ions at synapses and glutamatergic transmission. Study of familial migraine with aura pedigrees has also revealed other causal genes for monogenic forms of migraine. With respect to the more common polygenic form of migraine, large genome-wide association studies have increased our understanding of the genes, pathways and mechanisms involved in susceptibility, which are largely involved in neuronal and vascular functions. Given the preponderance of female migraineurs (3:1), there is evidence to suggest that hormonal or X-linked components can also contribute to migraine, and the role of genetic variants in mitochondrial DNA in migraine has been another avenue of exploration. Epigenetic studies of migraine have shown links between hormonal variation and alterations in DNA methylation and gene expression. While there is an abundance of preliminary studies identifying many potentially causative migraine genes and pathways, more comprehensive genomic and functional analysis to better understand mechanisms may aid in better diagnostic and treatment outcomes.

Evaluation of the possibility of selective modulation of retinal glucose transporters in diabetic complications: An experimental study

PURPOSE:

To identify the possibility of modulating retinal glucose transporters in diabetic conditions to prevent retinal complications of diabetic retinopathy.

MATERIALS AND METHODS:

In silico and in vitro binding assays were performed to assess the effect of genistein and positive controls (pioglitazone and estradiol) on nuclear receptor estrogen receptor beta and peroxisome proliferator-activated receptor gamma (PPARγ). In vivo effects of compounds were tested on diabetic rats. Structural and functional analysis of retina was performed at 28^th day followed by gene expression analysis of glucose transporters and nuclear receptors. Pioglitazone and genistein levels were analyzed by liquid chromatography with tandem mass spectrometry.

RESULTS:

Genistein showed equi-affinity toward PPARγ in In silico experiments contrary to in vitro findings. In multidose study, their therapeutic effects were observed by analyzing the retinal function. Retinal gene expression studies revealed that both test agents significantly up regulated PPARγ, GLUT4, and down regulated GLUT1. Genistein showed significant up regulation of GLUT4 and down regulation of GLUT1 as compared to PGZ which has been well correlated with the Electroretinography (ERG) outcome.

CONCLUSION:

This study showed the possibility of selective upregulation of GLUT4 (independent of PPARγ activation) in the retina of diabetic rats using genistein. Selective modulation of retinal glucose transporters as therapeutic target in ocular diabetic complications can be possibly explored.

Impact of lignans in oilseed mix on gut microbiome composition and enterolignan production in younger healthy and premenopausal women: an in vitro pilot study

BACKGROUND

Dietary lignans belong to the group of phytoestrogens together with coumestans, stilbenes and isoflavones, and themselves do not exhibit oestrogen-like properties. Nonetheless, the gut microbiota converts them into enterolignans, which show chemical similarity to the human oestrogen molecule. One of the richest dietary sources of lignans are oilseeds, including flaxseed. The aim of this pilot study was to determine the concentration of the main dietary lignans in an oilseed mix, and explore the gut microbiota-dependent production of enterolignans for oestrogen substitution in young and premenopausal women. The oilseed mix was fermented in a pH-controlled batch culture system inoculated with women's faecal samples. The lignan content and enterolignan production were measured by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and the faecal-derived microbial communities were profiled by 16S rRNA gene-based next-generation sequencing.

RESULTS

In vitro batch culture fermentation of faecal samples inoculated with oilseed mix for 24 h resulted in a substantial increase in enterolactone production in younger women and an increase in enterodiol in the premenopausal group. As for the gut microbiota, different baseline profiles were observed as well as different temporal dynamics, mainly related to Clostridiaceae, and Klebsiella and Collinsella spp.

CONCLUSIONS

Despite the small sample size, our pilot study revealed that lignan-rich oilseeds could strongly influence the faecal microbiota of both younger and premenopausal females, leading to a different enterolignan profile being produced. Further studies in larger cohorts are needed to evaluate the long-term effects of lignan-rich diets on the gut microbiota and find out how enterolactone-producing bacterial species could be increased. Diets rich in lignans could potentially serve as a safe supplement of oestrogen analogues to meet the cellular needs of endogenous oestrogen and deliver numerous health benefits, provided that the premenopausal woman microbiota is capable of converting dietary precursors into enterolignans.

DNA methylation profiling to explore colorectal tumor differences according to menopausal hormone therapy use in women

Aim: Use of menopausal hormone therapy (MHT) has been associated with a reduced risk for colorectal cancer, but mechanisms underlying this relationship are not well understood. In the colon, MHT appears to act through estrogen receptor β (ERβ) which may influence DNA methylation by binding to DNA. Using genome-wide methylation profiling data, we aimed to identify genes that may be differentially methylated according to MHT use. Materials & methods: DNA methylation was measured using Illumina HumanMethylation450k arrays in two independent tumor sample sets of colorectal cancer patients. Differential methylation was determined using R/limma. Results: In the discovery analysis, two CpG sites showed differential DNA methylation according to MHT use, both were not replicated. In stratified analyses, 342 CpG sites were associated with current MHT use only in ERβ-positive tumors. Conclusion: The suggestive findings of differential methylation according to current MHT use in ERβ-positive tumors warrant further investigation.

Downregulations of placental fatty acid transporters during cadmium-induced fetal growth restriction

Cadmium (Cd) is one of the environmental pollutants, which has multiple toxic effects on fetuses and placentas. Placental fatty acid (FA) uptake and transport are critical for the fetal and placental development. We aimed to analyze the triglyceride (TG) level, the expression patterns of several key genes involved in FA uptake and transport, and the molecular mechanisms for the altered gene expressions in placentas in response to Cd treatment. Our results showed that the placental TG level was significantly decreased in the Cd-exposed placentas. Fatty acid transporting protein 1 (FATP1), FATP6 and fatty acid binding protein 3 (FABP3) were significantly down-regulated in the placentas from Cd-exposed mice. The expression level of phospho-p38 MAPK was increased by Cd treatment, while the protein level of total p38 MAPK remained unchanged. The expression levels of peroxisome proliferator-activated receptor-γ (PPAR-γ) and the hypoxia-inducible factor-1α (HIF-1α) were significantly decreased in the Cd-exposed placentas. The methylation levels of the promoter regions of FATP1, FATP6 and FABP3 showed no significant differences between the treatment and control groups. In addition, the circulating non-esterified fatty acid (NEFA), total cholesterol (TC), and TG levels were not decreased in the maternal serum from the Cd-exposed mice. Therefore, our results suggest Cd exposure dose not reduce the maternal FA supply, but reduces the placental TG level. Cd treatment also downregulates the placental expressions of FATP1, FATP6 and FABP3, respectively associated with p38-MAPK, p38 MAPK/PPAR-γ and HIF-1α pathways.

Genome-wide DNA methylation differences according to oestrogen receptor beta status in colorectal cancer

Involvement of sex hormones in colorectal cancer (CRC) development has been linked to oestrogen receptor β (ERβ). Expression of ERβ is found reduced in tumour tissue and inversely related to mortality. However, mechanisms are not well understood. Our study aimed to detect differentially methylated genes associated with ERβ expression, which could point to mechanisms by which ERβ could influence risk and prognosis of CRC. Epigenome-wide DNA methylation profiling was performed using Illumina HumanMethylation450k BeadChip arrays in two independent tumour sample sets of CRC patients recruited in 2003-2010 by the German DACHS study (discovery cohort n = 917, replication cohort n = 907). ERβ expression was measured using immunohistochemistry and scored as negative, moderate and high. Differentially methylated CpG sites and genomic regions were determined using limma in the R-package RnBeads. For the comparison of tumours with moderate/high ERβ versus negative expression, differentially methylated CpG sites were identified but not confirmed by replication. Comparing tumours of high with tumours of negative ERβ expression revealed 2,904 differentially methylated CpG sites of which 403 were replicated (FDR adjusted p-value<0.05). Replicated CpGs were annotated to genes such as CD36, HK1 or LRP5. A survival analysis indicates that 30 of the replicated CpGs are also associated with overall survival (FDR-adjusted p-value<0.05). The regional analysis identified 60 differentially methylated promotor regions. The epigenome-wide analysis identified both novel genes as well as genes already implicated in CRC. Follow-up mechanistic studies to better understand the regulatory role of ERβ could inform potential targets for improving treatment or prevention of CRC.

High Estradiol Differentially Affects the Expression of the Glucose Transporter Type 4 in Pelvic Floor Muscles of Rats

PURPOSE

To characterize the relationship between serum estradiol levels and the expression of glucose transporter type 4 (Glut4) in the pubococcygeus and iliococcygeus muscles in female rats.

METHODS

The muscles were excised from virgin rats during the metestrus and proestrus stages of the estrous cycle, and from sham and ovariectomized rats implanted with empty or estradiol benzoate-filled capsules. The expression of estrogen receptors (ERs) was inspected in the muscles at metestrus and proestrus. Relative Glut4 expression, glycogen content, and serum glucose levels were measured. Appropriate statistical tests were done to identify significant differences (P≤0.05).

RESULTS

The pubococcygeus and iliococcygeus muscles expressed ERα and ERβ. Glut4 expression and glycogen content in the pubococcygeus muscle were higher at proestrus than at metestrus. No significant changes were observed in the iliococcygeus muscle. In ovariectomized rats, the administration of estradiol benzoate increased Glut4 expression and glycogen content in the pubococcygeus muscle alone.

CONCLUSION

High serum estradiol levels increased Glut4 expression and glycogen content in the pubococcygeus muscle, but not in the iliococcygeus muscle.

Proteomics in plasma of ovariectomized rats and those exposed to estradiol valerate

The menopausal period, an inevitable physiological process for women, is frequently associated with physiological and psychological dysfunction attributable to substantial fluctuation and gradual decrease in female hormones induced by ovarian failure, leading to corresponding symptoms and diseases that impact multiple systems in the body to varying degrees. As prior studies have focused primarily on menopausal syndrome-related pathophysiological changes and hormone replacement therapy effects, here we approached menopausal disease incidence risk and pathogenesis through systemic plasma proteomics analysis. Female Sprague-Dawley rats were randomly divided into sham, ovariectomized, and estrogen treatment after ovariectomy groups (n=9 per group). Tandem Mass Tag quantitative proteomics analysis of their plasma identified over 900 proteins by MS. Between group fold change of >1.2 and p<0.05 (Student's t-test) identified 121 (including 36 up-regulated and 85 down-regulated), 117 (69 up-regulated and 48 down-regulated), and 109 (41 up-regulated and 68 down-regulated) differentially expressed proteins between groups, respectively. Of these, 5 (GHR, LIFR, apoA IV, RTN, and Lin28b) were verified by parallel reaction monitoring to be reliable. Further application of optimized screening criteria and performance of a series of bioinformatics analyses allowed the selection of 35 optimal differentially expressed proteins. Gene ontology annotation results suggested that the differentially expressed proteins are mainly annotated as protein binding, cell, and single organism process in terms of molecular function, cell composition, and biological process, respectively. KEGG pathway analysis indicated that the PI3-Akt pathway has the highest aggregation degree of differentially expressed proteins. Protein-protein interaction analysis noted GLUT4 as an important node protein. This research is the first to comprehensively analyze plasma protein changes, together with estrogen efficacy, in ovariectomized rats. The findings facilitate our understanding of the molecular mechanism of systemic menopausal changes and provide valuable clues for developing diagnostic biomarkers for menopausal dysfunctions and selecting clinical therapeutic strategies.

Genes, Gender, Environment, and Novel Functions of Estrogen Receptor Beta in the Susceptibility to Neurodevelopmental Disorders

Many neurological disorders affect men and women differently regarding prevalence, progression, and severity. It is clear that many of these disorders may originate from defective signaling during fetal or perinatal brain development, which may affect males and females differently. Such sex-specific differences may originate from chromosomal or sex-hormone specific effects. This short review will focus on the estrogen receptor beta (ERβ) signaling during perinatal brain development and put it in the context of sex-specific differences in neurodevelopmental disorders. We will discuss ERβ’s recent discovery in directing DNA de-methylation to specific sites, of which one such site may bear consequences for the susceptibility to the neurological reading disorder dyslexia. We will also discuss how dysregulations in sex-hormone signaling, like those evoked by endocrine disruptive chemicals, may affect this and other neurodevelopmental disorders in a sex-specific manner through ERβ.

High Glucose-Induced Hypomethylation Promotes Binding of Sp-1 to Myo-Inositol Oxygenase: Implication in the Pathobiology of Diabetic Tubulopathy

The catabolic enzyme myo-inositol oxygenase (MIOX) is expressed in proximal tubules and up-regulated in the diabetic state. Previously, we reported its transcriptional and translation regulation by high glucose (HG), osmolytes, and fatty acids. However, its epigenetic regulation is unknown. Bisulfite sequencing revealed that both human and mouse MIOX promoters, enriched with CpG sites, are hypomethylated and unmethylated under HG ambience and hyperglycemic states associated with increased MIOX expression. Eletrophoretic mobility shift assays revealed increased binding of unmethylated oligos with nucleoproteins of cells maintained under HG. In addition, a strong binding of specificity protein (Sp)-1 transcription factor with MIOX promoter was observed under HG, especially with unmethylated Sp-1 oligo. Specificity of binding was established by supershift assays and treatment with the Sp-1 inhibitor mithramycin. Promoter analysis revealed an increase in luciferase activity under HG, which was reduced after mutation of the Sp-1-binding site. Sp1 siRNA treatment reduced mRNA and protein expression of Sp-1 and MIOX and generation of reactive oxygen species derived from NADPH oxidase (NOX)-4 and mitochondrial sources. In addition, there was reduced expression of hypoxia-inducible factor-1α relevant in the pathogenesis of diabetic nephropathy. Sp1 siRNA treatment reduced fibronectin expression, an extracellular matrix protein that is increased in diabetic nephropathy and tubulopathy. HG-induced MIOX expression was also reduced with the treatment of apelin-13, which deacetylates histones. Overall, these findings highlight the epigenetic regulation of MIOX in the pathogenesis of diabetic tubulopathy.

Sex-gender-related therapeutic approaches for cardiovascular complications associated with diabetes

Diabetes is a chronic disease associated with micro- and macrovascular complications and is a well-established risk factor for cardiovascular disease. Cardiovascular complications associated with diabetes are among the most important causes of death in diabetic patients. Interestingly, several sex-gender differences have been reported to significantly impact in the pathophysiology of diabetes. In particular, sex-gender differences have been reported to affect diabetes epidemiology, risk factors, as well as cardiovascular complications associated with diabetes. This suggests that different therapeutic approaches are needed for managing diabetes-associated cardiovascular complications in men and women. In this review, we will discuss about the sex-gender differences that are known to impact on diabetes, mainly focusing on the cardiovascular complications associated with the disease. We will then discuss the therapeutic approaches for managing diabetes-associated cardiovascular complications and how differences in sex-gender can influence the existing therapeutic approaches.

The role of sex steroids in white adipose tissue adipocyte function

With the increasing knowledge that gender influences normal physiology, much biomedical research has begun to focus on the differential effects of sex on tissue function. Sexual dimorphism in mammals is due to the combined effects of both genetic and hormonal factors. Hormonal factors are mutable particularly in females in whom the estrous cycle dominates the hormonal milieu. Given the severity of the obesity epidemic and the fact that there are differences in the obesity rates in men and women, the role of sex in white adipose tissue function is being recognized as increasingly important. Although sex differences in white adipose tissue distribution are well established, the mechanisms affecting differential function of adipocytes within white adipose tissue in males and females remain largely understudied and poorly understood. One of the largest differences in the endocrine environment in males and females is the concentration of circulating androgens and estrogens. This review examines the effects of androgens and estrogens on lipolysis/lipogenesis, adipocyte differentiation, insulin sensitivity and adipokine production in adipocytes from white adipose tissue with a specific emphasis on the sexual dimorphism of adipocyte function in white adipose tissue during both health and disease.

Alterations in the neuropeptide galanin system in major depressive disorder involve levels of transcripts, methylation, and peptide

Major depressive disorder (MDD) is a substantial burden to patients, families, and society, but many patients cannot be treated adequately. Rodent experiments suggest that the neuropeptide galanin (GAL) and its three G protein-coupled receptors, GAL_1-3, are involved in mood regulation. To explore the translational potential of these results, we assessed the transcript levels (by quantitative PCR), DNA methylation status (by bisulfite pyrosequencing), and GAL peptide by RIA of the GAL system in postmortem brains from depressed persons who had committed suicide and controls. Transcripts for all four members were detected and showed marked regional variations, GAL and galanin receptor 1 (GALR1) being most abundant. Striking increases in GAL and GALR3 mRNA levels, especially in the noradrenergic locus coeruleus and the dorsal raphe nucleus, in parallel with decreased DNA methylation, were found in both male and female suicide subjects as compared with controls. In contrast, GAL and GALR3 transcript levels were decreased, GALR1 was increased, and DNA methylation was increased in the dorsolateral prefrontal cortex of male suicide subjects, however, there were no changes in the anterior cingulate cortex. Thus, GAL and its receptor GALR3 are differentially methylated and expressed in brains of MDD subjects in a region- and sex-specific manner. Such an epigenetic modification in GALR3, a hyperpolarizing receptor, might contribute to the dysregulation of noradrenergic and serotonergic neurons implicated in the pathogenesis of MDD. Thus, one may speculate that a GAL₃ antagonist could have antidepressant properties by disinhibiting the firing of these neurons, resulting in increased release of noradrenaline and serotonin in forebrain areas involved in mood regulation.

Animal models of monogenic migraine

Migraine is a highly prevalent and disabling neurological disorder with a strong genetic component. Rare monogenic forms of migraine, or syndromes in which migraine frequently occurs, help scientists to unravel pathogenetic mechanisms of migraine and its comorbidities. Transgenic mouse models for rare monogenic mutations causing familial hemiplegic migraine (FHM), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and familial advanced sleep-phase syndrome (FASPS), have been created. Here, we review the current state of research using these mutant mice. We also discuss how currently available experimental approaches, including epigenetic studies, biomolecular analysis and optogenetic technologies, can be used for characterization of migraine genes to further unravel the functional and molecular pathways involved in migraine.

Oestrogen receptor β regulates epigenetic patterns at specific genomic loci through interaction with thymine DNA glycosylase

Background

DNA methylation is one way to encode epigenetic information and plays a crucial role in regulating gene expression during embryonic development. DNA methylation marks are established by the DNA methyltransferases and, recently, a mechanism for active DNA demethylation has emerged involving the ten-eleven translocator proteins and thymine DNA glycosylase (TDG). However, so far it is not clear how these enzymes are recruited to, and regulate DNA methylation at, specific genomic loci. A number of studies imply that sequence-specific transcription factors are involved in targeting DNA methylation and demethylation processes. Oestrogen receptor beta (ERβ) is a ligand-inducible transcription factor regulating gene expression in response to the female sex hormone oestrogen. Previously, we found that ERβ deficiency results in changes in DNA methylation patterns at two gene promoters, implicating an involvement of ERβ in DNA methylation. In this study, we set out to explore this involvement on a genome-wide level, and to investigate the underlying mechanisms of this function.

Results

Using reduced representation bisulfite sequencing, we compared genome-wide DNA methylation in mouse embryonic fibroblasts derived from wildtype and ERβ knock-out mice, and identified around 8000 differentially methylated positions (DMPs). Validation and further characterisation of selected DMPs showed that differences in methylation correlated with changes in expression of the nearest gene. Additionally, re-introduction of ERβ into the knock-out cells could reverse hypermethylation and reactivate expression of some of the genes. We also show that ERβ is recruited to regions around hypermethylated DMPs. Finally, we demonstrate here that ERβ interacts with TDG and that TDG binds ERβ-dependently to hypermethylated DMPs.

Conclusion

We provide evidence that ERβ plays a role in regulating DNA methylation at specific genomic loci, likely as the result of its interaction with TDG at these regions. Our findings imply a novel function of ERβ, beyond direct transcriptional control, in regulating DNA methylation at target genes. Further, they shed light on the question how DNA methylation is regulated at specific genomic loci by supporting a concept in which sequence-specific transcription factors can target factors that regulate DNA methylation patterns.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-016-0055-7) contains supplementary material, which is available to authorised users.

Developmental exposure to bisphenol A alters expression and DNA methylation of Fkbp5, an important regulator of the stress response

Bisphenol A (BPA), an abundant endocrine disruptor, affects stress-responsiveness and related behaviors in children. In rats, perinatal BPA exposure modifies stress response in pubertal offspring via unknown mechanisms. Here we examined possible epigenetic modifications in the glucocorticoid receptor gene and its regulator Fkbp5 in hypothalamus and hippocampus of exposed offspring. We found increased DNA methylation of Fkbp5 and reduced protein levels in the hippocampus of exposed male rats. Similar effects were obtained in a male hippocampal cell line when exposed to BPA during differentiation. The estrogen receptor (ER) antagonist ICI 182,780 or ERβ knock-down affected Fkbp5 expression and methylation similarly to BPA. Further, BPA's effect on Fkbp5 was abolished upon knock-down of ERβ, suggesting a role for this receptor in mediating BPA's effects on Fkbp5. These data demonstrate that developmental BPA exposure modifies Fkbp5 methylation and expression in male rats, which may be related to its impact on stress responsiveness.

Epigenetics and Metabolism

The molecular signatures of epigenetic regulation and chromatin architectures are fundamental to genetically determined biological processes. Covalent and post-translational chemical modification of the chromatin template can sensitize the genome to changing environmental conditions to establish diverse functional states. Recent interest and research focus surrounds the direct connections between metabolism and chromatin dynamics, which now represents an important conceptual challenge to explain many aspects of metabolic dysfunction. Several components of the epigenetic machinery require intermediates of cellular metabolism for enzymatic function. Furthermore, changes to intracellular metabolism can alter the expression of specific histone methyltransferases and acetyltransferases conferring widespread variations in epigenetic modification patterns. Specific epigenetic influences of dietary glucose and lipid consumption, as well as undernutrition, are observed across numerous organs and pathways associated with metabolism. Studies have started to define the chromatin-dependent mechanisms underlying persistent and pathophysiological changes induced by altered metabolism. Importantly, numerous recent studies demonstrate that gene regulation underlying phenotypic determinants of adult metabolic health is influenced by maternal and early postnatal diet. These emerging concepts open new perspectives to combat the rising global epidemic of metabolic disorders.

Nuclear receptors and epigenetic regulation: opportunities for nutritional targeting and disease prevention

Posttranslational modifications of histones, alterations in the recruitment and functions of non-histone proteins, DNA methylation, and changes in expression of noncoding RNAs contribute to current models of epigenetic regulation. Nuclear receptors (NRs) are a group of transcription factors that, through ligand-binding, act as sensors to changes in nutritional, environmental, developmental, pathophysiologic, and endocrine conditions and drive adaptive responses via gene regulation. One mechanism through which NRs direct gene expression is the assembly of transcription complexes with cofactors and coregulators that possess chromatin-modifying properties. Chromatin modifications can be transient or become part of the cellular "memory" and contribute to genomic imprinting. Because many food components bind to NRs, they can ultimately influence transcription of genes associated with biologic processes, such as inflammation, proliferation, apoptosis, and hormonal response, and alter the susceptibility to chronic diseases (e.g., cancer, diabetes, obesity). The objective of this review is to highlight how NRs influence epigenetic regulation and the relevance of dietary compound-NR interactions in human nutrition and for disease prevention and treatment. Identifying gene targets of unliganded and bound NRs may assist in the development of epigenetic maps for food components and dietary patterns. Progress in these areas may lead to the formulation of disease-prevention models based on epigenetic control by individual or associations of food ligands of NRs.

Antenatal prediction of postpartum depression with blood DNA methylation biomarkers

Postpartum depression (PPD) affects ∼10-18% of women in the general population and results in serious consequences to both the mother and offspring. We hypothesized that predisposition to PPD risk is due to an altered sensitivity to estrogen-mediated epigenetic changes that act in a cell autonomous manner detectable in the blood. We investigated estrogen-mediated epigenetic reprogramming events in the hippocampus and risk to PPD using a cross-species translational design. DNA methylation profiles were generated using methylation microarrays in a prospective sample of the blood from the antenatal period of pregnant mood disorder patients who would and would not develop depression postpartum. These profiles were cross-referenced with syntenic locations exhibiting hippocampal DNA methylation changes in the mouse responsive to long-term treatment with 17β-estradiol (E2). DNA methylation associated with PPD risk correlated significantly with E2-induced DNA methylation change, suggesting an enhanced sensitivity to estrogen-based DNA methylation reprogramming exists in those at risk for PPD. Using the combined mouse and human data, we identified two biomarker loci at the HP1BP3 and TTC9B genes that predicted PPD with an area under the receiver operator characteristic (ROC) curve (area under the curve (AUC)) of 0.87 in antenatally euthymic women and 0.12 in a replication sample of antenatally depressed women. Incorporation of blood count data into the model accounted for the discrepancy and produced an AUC of 0.96 across both prepartum depressed and euthymic women. Pathway analyses demonstrated that DNA methylation patterns related to hippocampal synaptic plasticity may be of etiological importance to PPD.

Ovarian steroids influence cerebral glucose transporter expression in a region- and isoform-specific pattern

Cerebral glucose uptake is mediated by several members of the family of facilitated glucose transporters (protein nomenclature GLUT; gene nomenclature solute carrier family 2 Slc2a). Glucose uptake differs between the sexes and also varies with menstrual status in women and across the rodent oestrous cycle. The present study demonstrates the extent to which hormonal variation across the four stages of the rat oestrous cycle affects the mRNA abundance of four members of the GLUT family, including the most well characterised cerebral transporters Slc2a1 and Slc2a3, as well as the insulin-sensitive transporters Slc2a4 and Slc2a8 in the hypothalamus, hippocampus and prefrontal cortex. Slc2a1 varied significantly across the cycle in the hippocampus and prefrontal cortex, and Slc2a3 and Slc2a4 also showed significant fluctuation in the hippocampus. Transporter expression significantly increased during pro-oestrus in both the hippocampus and prefrontal cortex. Furthermore, ovarian hormones are critical for normal expression of GLUT mRNA, as demonstrated by reduced expression of Slc2a1, Slc2a3 and Sl2a8 in the hippocampus after ovariectomy. Collectively, the data reported in the present study demonstrate that glucose transporters are highly sensitive to hormonal variation and that this sensitivity is regionally distinct; thereby fluctuations likely have specific phenotypic implications.

Sex differences in adipose tissue: It is not only a question of quantity and distribution

Obesity and its associated secondary complications are active areas of investigation in search of effective treatments. As a result of this intensified research numerous differences between males and females at all levels of metabolic control have come to the forefront. These differences include not only the amount and distribution of adipose tissue, but also differences in its metabolic capacity and functions between the sexes. Here, we review some of the recent advances in our understanding of these dimorphisms and emphasize the fact that these differences between males and females must be taken into consideration in hopes of obtaining successful treatments for both sexes.

Sex, sex steroids, and diabetic cardiomyopathy: making the case for experimental focus

More than three decades ago, the Framingham study revealed that cardiovascular risk is elevated for all diabetics and that this jeopardy is substantially accentuated for women in particular. Numerous studies have subsequently documented worsened cardiac outcomes for women. Given that estrogen and insulin exert major regulatory effects through common intracellular signaling pathways prominent in maintenance of cardiomyocyte function, a sex-hormone:diabetic-disease interaction is plausible. Underlying aspects of female cardiovascular pathophysiology that exaggerate cardiovascular diabetic risk may be identified, including increased vulnerability to coronary microvascular disease, age-dependent impairment of insulin-sensitivity, and differential susceptibility to hyperglycemia. Since Framingham, considerable progress has been made in the development of experimental models of diabetic disease states, including a diversity of genetic rodent models. Ample evidence indicates that animal models of both type 1 and 2 diabetes variably recapitulate aspects of diabetic cardiomyopathy including diastolic and systolic dysfunction, and cardiac structural pathology including fibrosis, loss of compliance, and in some instances ventricular hypertrophy. Perplexingly, little of this work has explored the relevance and mechanisms of sexual dimorphism in diabetic cardiomyopathy. Only a small number of experimental studies have addressed this question, yet the prospects for gaining important mechanistic insights from further experimental enquiry are considerable. The case for experimental interrogation of sex differences, and of sex steroid influences in the aetiology of diabetic cardiomyopathy, is particularly compelling-providing incentive for future investigation with ultimate therapeutic potential.

Post-weaning selenium and folate supplementation affects gene and protein expression and global DNA methylation in mice fed high-fat diets

Background

Consumption of high-fat diets has negative impacts on health and well-being, some of which may be epigenetically regulated. Selenium and folate are two compounds which influence epigenetic mechanisms. We investigated the hypothesis that post-weaning supplementation with adequate levels of selenium and folate in offspring of female mice fed a high-fat, low selenium and folate diet during gestation and lactation will lead to epigenetic changes of potential importance for long-term health.

Methods

Female offspring of mothers fed the experimental diet were either maintained on this diet (HF-low-low), or weaned onto a high-fat diet with sufficient levels of selenium and folate (HF-low-suf), for 8 weeks. Gene and protein expression, DNA methylation, and histone modifications were measured in colon and liver of female offspring.

Results

Adequate levels of selenium and folate post-weaning affected gene expression in colon and liver of offspring, including decreasing Slc2a4 gene expression. Protein expression was only altered in the liver. There was no effect of adequate levels of selenium and folate on global histone modifications in the liver. Global liver DNA methylation was decreased in mice switched to adequate levels of selenium and folate, but there was no effect on methylation of specific CpG sites within the Slc2a4 gene in liver.

Conclusions

Post-weaning supplementation with adequate levels of selenium and folate in female offspring of mice fed high-fat diets inadequate in selenium and folate during gestation and lactation can alter global DNA methylation in liver. This may be one factor through which the negative effects of a poor diet during early life can be ameliorated. Further research is required to establish what role epigenetic changes play in mediating observed changes in gene and protein expression, and the relevance of these changes to health.

Epigenetic mechanisms in migraine: a promising avenue?

Migraine is a disabling common brain disorder typically characterized by attacks of severe headache and associated with autonomic and neurological symptoms. Its etiology is far from resolved. This review will focus on evidence that epigenetic mechanisms play an important role in disease etiology. Epigenetics comprise both DNA methylation and post-translational modifications of the tails of histone proteins, affecting chromatin structure and gene expression. Besides playing a role in establishing cellular and developmental stage-specific regulation of gene expression, epigenetic processes are also important for programming lasting cellular responses to environmental signals. Epigenetic mechanisms may explain how non-genetic endogenous and exogenous factors such as female sex hormones, stress hormones and inflammation trigger may modulate attack frequency. Developing drugs that specifically target epigenetic mechanisms may open up exciting new avenues for the prophylactic treatment of migraine.

Epigenetic regulation of estrogen signaling in breast cancer

Estrogen signaling is mediated by ERα and ERβ in hormone dependent, breast cancer (BC). Over the last decade the implication of epigenetic pathways in BC tumorigenesis has emerged: cancer-related epigenetic modifications are implicated in both gene expression regulation, and chromosomal instability. In this review, the epigenetic-mediated estrogen signaling, controlling both ER level and ER-targeted gene expression in BC, are discussed: (1) ER silencing is frequently observed in BC and is often associated with epigenetic regulations while chemical epigenetic modulators restore ER expression and increase response to treatment;(2) ER-targeted gene expression is tightly regulated by co-recruitment of ER and both coactivators/corepressors including HATs, HDACs, HMTs, Dnmts and Polycomb proteins.

Identifying candidate genes for Type 2 Diabetes Mellitus and obesity through gene expression profiling in multiple tissues or cells

Type 2 Diabetes Mellitus (T2DM) and obesity have become increasingly prevalent in recent years. Recent studies have focused on identifying causal variations or candidate genes for obesity and T2DM via analysis of expression quantitative trait loci (eQTL) within a single tissue. T2DM and obesity are affected by comprehensive sets of genes in multiple tissues. In the current study, gene expression levels in multiple human tissues from GEO datasets were analyzed, and 21 candidate genes displaying high percentages of differential expression were filtered out. Specifically, DENND1B, LYN, MRPL30, POC1B, PRKCB, RP4-655J12.3, HIBADH, and TMBIM4 were identified from the T2DM-control study, and BCAT1, BMP2K, CSRNP2, MYNN, NCKAP5L, SAP30BP, SLC35B4, SP1, BAP1, GRB14, HSP90AB1, ITGA5, and TOMM5 were identified from the obesity-control study. The majority of these genes are known to be involved in T2DM and obesity. Therefore, analysis of gene expression in various tissues using GEO datasets may be an effective and feasible method to determine novel or causal genes associated with T2DM and obesity.

Genomic DNA methylation changes in NYGGF4-overexpression 3T3-L1 adipocytes

NYGGF4, an obesity-related gene, is proposed to be involved in the development of insulin resistance; however, the underlying molecular mechanisms remain unclear. In the present analysis, NimbleGen tiling arrays were used to determine the patterns of genomic DNA methylation at CpG islands and promoters in NYGGF4-overexpression adipocytes. A total of 2352 CpG dinucleotides in 2018 genes and 3490 CpG dinucleotides in 3064 genes were found to be hypermethylated or hypomethylated, respectively, in NYGGF4-overexpression adipocytes. Furthermore, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis revealed enrichment of biological processes associated with energy metabolism and signal transduction events, including the peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway, and mitogen-activated protein kinases(MAPK) and Ras homolog gene family, member A (RhoA) signaling. These data demonstrate that differentially methylated genes are significantly overrepresented in NYGGF4-overexpression adipocytes, providing valuable clues for further exploration of the role of NYGGF4 in insulin sensitivity regulation.

The rs3743205 SNP is important for the regulation of the dyslexia candidate gene DYX1C1 by estrogen receptor β and DNA methylation

Estrogen is involved in numerous physiological processes such as growth, differentiation, and function of the male and female reproductive tissues. In the developing brain, estrogen signaling has been linked to cognitive functions, such as learning and memory; however, the molecular mechanisms underlying this phenomenon are poorly understood. We have previously shown a link between developmental dyslexia and estrogen signaling, when we studied the functional interactions between the dyslexia candidate protein DYX1C1 and the estrogen receptors α (ERα) and β (ERβ). Here, we investigate the 17β-estradiol (E2)-dependent regulation of dyslexia susceptibility 1 candidate 1 (DYX1C1) expression. We demonstrate that ERβ, not ERα, binds to a transcriptionally active cis-regulatory region upstream of DYX1C1 transcriptional start site and that DYX1C1 expression is enhanced by E2 in a neuroblastoma cell line. This regulation is dependent on transcription factor II-I and liganded ERβ recruitment to this region. In addition, we describe that a single nucleotide polymorphism previously shown to be associated with dyslexia and located in the cis-regulatory region of DYX1C1 may alter the epigenetic and endocrine regulation of this gene. Our data provide important molecular insights into the relationship between developmental dyslexia susceptibility and estrogen signaling.