Hypermethylation of Sp1 binding site suppresses hypothalamic POMC in neonates and may contribute to metabolic disorders in adults: impact of maternal dietary CLAs

DNA Methylation in the Hypothalamic Feeding Center and Obesity

Obesity rates have been increasing worldwide for decades, mainly due to environmental factors, such as diet, nutrition, and exercise. However, the molecular mechanisms through which environmental factors induce obesity remain unclear. Several mechanisms underlie the body's response to environmental factors, and one of the main mechanisms involves epigenetic modifications, such as DNA methylation. The pattern of DNA methylation is influenced by environmental factors, and altered DNA methylation patterns can affect gene expression profiles and phenotypes. DNA methylation may mediate the development of obesity caused by environmental factors. Similar to the factors governing obesity, DNA methylation is influenced by nutrients and metabolites. Notably, DNA methylation is associated with body size and weight programming. The DNA methylation levels of proopiomelanocortin (Pomc) and neuropeptide Y (Npy) in the hypothalamic feeding center, a key region controlling systemic energy balance, are affected by diet. Conditional knockout mouse studies of epigenetic enzymes have shown that DNA methylation in the hypothalamic feeding center plays an indispensable role in energy homeostasis. In this review, we discuss the role of DNA methylation in the hypothalamic feeding center as a potential mechanism underlying the development of obesity induced by environmental factors.

Hypothalamic DNA 5-hydroxymethylation levels are altered by diet-induced weight gain during the development of obesity in a sex-specific manner

Obesity is a major health concern that is associated with altered gene transcription in the hypothalamus. However, the mechanisms controlling this gene expression dysregulation remain largely unknown. DNA 5-hydroxymethylation (5-hmC) is a potent transcriptional activator that is expressed at 10 times higher levels in the brain than the periphery. Despite this, no study has examined if DNA 5-hmC is altered in the brain following exposure to obesogenic diets or contributes to abnormal weight gain over time. Here, we used a rodent diet-induced obesity model in combination with quantitative molecular assays and CRISPR-dCas9 manipulations to test the role of hypothalamic DNA 5-hmC in abnormal weight gain in male and female rats. We found that males, but not females, have decreased levels of DNA 5-hmC in the hypothalamus following exposure to a high fat diet, which directly correlate with increased body weight. Short-term exposure to a high fat diet, which does not result in significant weight gain, resulted in decreased hypothalamic DNA 5-hmC levels, suggesting these changes occur prior to obesity development. Moreover, decreases in DNA 5-hmC persist even after the high fat diet is removed, though the extent of this is diet-dependent. Importantly, CRISPR-dCas9-mediated upregulation of DNA 5-hmC enzymes in the male, but not female, ventromedial nucleus of the hypothalamus significantly reduced the percentage of weight gained on the high fat diet relative to controls. These results suggest that hypothalamic DNA 5-hmC is an important sex-specific regulator of abnormal weight gain following exposure to high fat diets.

Targeted inhibition of PPARα ameliorates CLA-induced hypercholesterolemia via hepatic cholesterol biosynthesis reprogramming

BACKGROUND & AIMS

Disruption of lipid metabolism is largely linked to metabolic disorders, such as hypercholesterolemia (HCL) and liver steatosis. While cholesterol metabolic re-programmers can serve as targets for relevant interventions. Here we explored the dietary conjugated linoleic acids (CLA)-induced HCL in mice and the molecular regulation behind it.

METHODS

A high dose of CLA supplementation in the diet was used to induce HCL in mice and was found to cause a hyper-activated cholesterol biosynthesis programme in the liver, leading to cholesterol metabolism dysregulation. The effects of a small-molecule drug targeting PPARα, i.e., GW6471 were studied in vivo in mice fed diets with CLA supplementation for 28 days, and in primary hepatocytes derived from HCL-mice in vitro.

RESULTS

We demonstrate that CLA induced HCL and liver steatosis through multiple pathways. Among which was the PPARα-mediated cholesterogenesis. It was found to cooperate with SREBP2 via binding to Hmgcr and Dhcr7 (genes encoding key enzymes of the cholesterol biosynthetic pathway) and recruits the histone marks H3K27ac and H3K4me1 and cofactors. PPARα inhibition disrupts its physical association with SREBP2 by blocking cobinding of PPARα and SREBP2 to the genomic DNA response element. We showed that NR RORγ functions as an essential mediator that facilitates the interaction of PPARα and SREBP2 to modulate the cholesterol biosynthesis genes expression.

CONCLUSIONS

Our study unravels that the small-molecule compound GW6471 exerts an attractive therapeutic effect for CLA-induced HCL, involving multiple pathways with the "PPARα-RORγ-SREBP2" being a potential complex player in this hepatic cholesterol biosynthesis programming.

The interplay between diet, gut microbes, and host epigenetics in health and disease

The mechanisms linking the function of microbes to host health are becoming better defined but are not yet fully understood. One recently explored mechanism involves microbe-mediated alterations in the host epigenome. Consumption of specific dietary components such as fiber, glucosinolates, polyphenols, and dietary fat has a significant impact on gut microbiota composition and function. Microbial metabolism of these dietary components regulates important epigenetic functions that ultimately influences host health. Diet-mediated alterations in the gut microbiome regulate the substrates available for epigenetic modifications like DNA methylation or histone methylation and/or acetylation. In addition, generation of microbial metabolites such as butyrate inhibits the activity of core epigenetic enzymes like histone deacetylases (HDACs). Reciprocally, the host epigenome also influences gut microbial composition. Thus, complex interactions exist between these three factors. This review comprehensively examines the interplay between diet, gut microbes, and host epigenetics in modulating host health. Specifically, the dietary impact on gut microbiota structure and function that in-turn regulates host epigenetics is evaluated in terms of promoting protection from disease development.

Sex and Exposure to Postnatal Chlorpyrifos Influence the Epigenetics of Feeding-Related Genes in a Transgenic APOE Mouse Model: Long-Term Implications on Body Weight after a High-Fat Diet

Developmental exposure to toxicants and diet can interact with an individual's genetics and produce long-lasting metabolic adaptations. The different isoforms of the apolipoprotein E (APOE) are an important source of variability in metabolic disorders and influence the response to the pesticide chlorpyrifos (CPF). We aimed to study the epigenetic regulation on feeding control genes and the influence of postnatal CPF exposure, APOE genotype, and sex, and how these modifications impact on the metabolic response to a high-fat diet (HFD). Both male and female apoE3- and apoE4-TR mice were exposed to CPF on postnatal days 10-15. The DNA methylation pattern of proopiomelanocortin, neuropeptide Y, leptin receptor, and insulin-like growth factor 2 was studied in the hypothalamus. At adulthood, the mice were given a HFD for eight weeks. The results highlight the importance of sex in the epigenetic regulation and the implication of CPF treatment and APOE genotype. The body weight progression exhibited sex-dimorphic differences, apoE4-TR males being the most susceptible to the effects induced by CPF and HFD. Overall, these results underscore the pivotal role of sex, APOE genotype, and developmental exposure to CPF on subsequent metabolic disturbances later in life and show that sex is a key variable in epigenetic regulation.

Co-option of PPARα in the regulation of lipogenesis and fatty acid oxidation in CLA-induced hepatic steatosis

Nonalcoholic-fatty-liver-disease (NAFLD) is the result of imbalances in hepatic lipid partitioning and is linked to dietary factors. We demonstrate that conjugated linoleic acid (CLA) when given to mice as a dietary supplement, induced an enlarged liver, hepatic steatosis, and increased plasma levels of fatty acid (FA), alanine transaminase, and triglycerides. The progression of NAFLD and insulin resistance was reversed by GW6471 a small-molecule antagonist of peroxisome proliferator-activated receptor α (PPARα). Transcriptional profiling of livers revealed that the genes involved in FA oxidation and lipogenesis as two core gene programs controlled by PPARα in response to CLA and GW6471 including Acaca and Acads. Bioinformatic analysis of PPARα ChIP-seq data set and ChIP-qPCR showed that GW6471 blocks PPARα binding to Acaca and Acads and abolishes the PPARα-mediated local histone modifications of H3K27ac and H3K4me1 in CLA-treated hepatocytes. Thus, our findings reveal a dual role of PPARα in the regulation of lipid homeostasis and highlight its druggable nature in NAFLD.

Fetal Programming by Methyl Donors Modulates Central Inflammation and Prevents Food Addiction-Like Behavior in Rats

Fetal programming by hypercaloric intake leads to food addiction-like behavior and brain pro-inflammatory gene expression in offspring. The role of methylome modulation during programming on central immune activation and addiction-like behavior has not been characterized. We employed a nutritional programming model exposing female Wistar rats to chow diet, cafeteria (CAF), or CAF-methyl donor’s diet from pre-pregnancy to weaning. Addiction-like behavior in offspring was characterized by the operant training response using Skinner boxes. Food intake in offspring was determined after fasting–refeeding schedule and subcutaneous injection of ghrelin. Genome-wide DNA methylation in the nucleus accumbens (NAc) shell was performed by fluorescence polarization, and brain immune activation was evaluated using real-time PCR for pro-inflammatory cytokines (IL-1β, TNF-1α, and IL-6). Molecular effects of methyl modulators [S-adenosylmethionine (SAM) or 5-azatidine (5-AZA)] on pro-inflammatory cytokine expression and phagocytosis were identified in the cultures of immortalized SIM-A9 microglia cells following palmitic acid (100 μM) or LPS (100 nM) stimulation for 6 or 24 h. Our results show that fetal programming by CAF exposure increases the number of offspring subjects and reinforcers under the operant training response schedule, which correlates with an increase in the NAc shell global methylation. Notably, methyl donor’s diet selectively decreases lever-pressing responses for reinforcers and unexpectedly decreases the NAc shell global methylation. Also, programmed offspring by CAF diet shows a selective IL-6 gene expression in the NAc shell, which is reverted to control values by methyl diet exposure. In vitro analysis identified that LPS and palmitic acid activate IL-1β, TNF-1α, and IL-6 gene expression, which is repressed by the methyl donor SAM. Finally, methylation actively represses phagocytosis activity of SIM-A9 microglia cells induced by LPS and palmitic acid stimulation. Our in vivo and in vitro data suggest that fetal programming by methyl donors actively decreases addiction-like behavior to palatable food in the offspring, which correlates with a decrease in NAc shell methylome, expression of pro-inflammatory cytokine genes, and activity of phagocytic microglia. These results support the role of fetal programming in brain methylome on immune activation and food addiction-like behavior in the offspring.

Identification of High-Frequency Methylation Sites in RNF180 Promoter Region Affecting Expression and Their Relationship with Prognosis of Gastric Cancer

Background

Ring finger protein 180 (RNF180) is a tumor suppressor gene regulated by promoter methylation. We previously demonstrated that the RNF180 promoter methylation could be a risk factor for gastric cancer (GC); and eight high-frequency hypermethylated CpG sites were associated with GC. However, it is not clear whether these key sites can affect gene expression and involve in prognosis. The aim of this study was to investigate the effects of above CpG sites on the gene expression and prognosis of GC.

Patients and Methods

A total of 164 GC tissues were enrolled and followed up. Tissue samples were used for DNA and RNA isolation. Methylation status of RNF180 was detected using bisulfite sequencing PCR (BSP). Expression levels of RNF180 were detected using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). JASPAR and PROMO databases were used to predict the transcription factors (TFs) binding to the CpG site.

Results

The methylation in RNF180 promoter region increased and mRNA expression decreased in GC tissue. Correlation analysis revealed that the average methylation rate (AMR) and four CpG sites methylation rate were negatively related to RNF180 expression, including M3(−165)(Chr5:64165942), M5(−148)(Chr5:64,165,959), M7(−133)(Chr5:64,165,974) and M8(−130)(Chr5:64,165,977). Furthermore, the methylation rate of M5(−148)(Chr5:64,165,959) and M27(−26)(Chr5:64,166,081) above 0.3 indicated poor prognosis (P_M5 = 0.008, P_M27 = 0.003, HR_M5(−148) = 2.000 (1.201,3.332), HR_M27(−26)=2.389 (1.336,4.271)), which could be independent factors of prognosis.

Conclusion

By focusing on the methylation sites in the RNF180 promoter region, we identified two high-frequency methylation sites, M5(−148)(Chr5:64,165,959) and M27(−26)(Chr5:64,166,081), which could affect gene expression and predict the prognosis of GC. In the future, the possible molecular mechanism involved needs to be further studied.

Sex-specific epigenetic alterations of the hypothalamic Agrp-Pomc system do not explain 'diabesity' in the offspring of high-fat diet (HFD) overfed maternal rats

Maternal high-fat diet (HFD) overfeeding pre- and during pregnancy and lactation may 'program' a 'diabesity' predisposition in the offspring, for inconclusive reasons. Acquired alterations of the hypothalamic promoter methylation and mRNA expression of the satiety neurohormone Pomc are possibly of critical importance here. We investigated within one developmental approach, including male and female rats, the sex-specific DNA methylation pattern and corresponding mRNA expression of both Pomc and its endogenous functional antagonist Agrp in the hypothalamus of adult HFD offspring. Obesity and diabetic disturbances occurred in both male and female HFD offspring, accompanied by altered Pomc promoter methylation pattern. However, this was not related to significant Pomc mRNA expression alterations. In contrast, male-specific alterations of Agrp promoter methylation were found, even associated with reduced mRNA expression of this orexigenic/anabolic Pomc antagonist. In conclusion, acquired epigenetic alterations of the hypothalamic Agrp-Pomc system hardly explain the 'diabesity' phenotype in HFD offspring, while distinct vulnerability and functionality of Agrp promoter and related genomic regions methylation should be further investigated.

Diet-induced DNA methylation within the hypothalamic arcuate nucleus and dysregulated leptin and insulin signaling in the pathophysiology of obesity

Obesity rates continue to rise in an unprecedented manner in what could be the most rapid population‐scale shift in human phenotype ever to occur. Increased consumption of unhealthy, calorie‐dense foods, coupled with sedentary lifestyles, is the main factor contributing to a positive energy balance and the development of obesity. Leptin and insulin are key hormones implicated in pathogenesis of this disorder and are crucial for controlling whole‐body energy homeostasis. Their respective function is mediated by the counterbalance of anorexigenic and orexigenic neurons located within the hypothalamic arcuate nucleus. Dysregulation of leptin and insulin signaling pathways within this brain region may contribute not only to the development of obesity, but also systemically affect the peripheral organs, thereby manifesting as metabolic diseases. Although the exact mechanisms detailing how these hypothalamic nuclei contribute to disease pathology are still unclear, increasing evidence suggests that altered DNA methylation may be involved. This review evaluates animal studies that have demonstrated diet‐induced DNA methylation changes in genes that regulate energy homeostasis within the arcuate nucleus, and elucidates possible mechanisms causing hypothalamic leptin and insulin resistance leading to the development of obesity and metabolic diseases.

Epigenetic regulation of POMC; implications for nutritional programming, obesity and metabolic disease

Proopiomelanocortin (POMC) is a key mediator of satiety. Epigenetic marks such as DNA methylation may modulate POMC expression and provide a biological link between early life exposures and later phenotype. Animal studies suggest epigenetic marks at POMC are influenced by maternal energy excess and restriction, prenatal stress and Triclosan exposure. Postnatal factors including energy excess, folate, vitamin A, conjugated linoleic acid and leptin may also affect POMC methylation. Recent human studies suggest POMC DNA methylation is influenced by maternal nutrition in early pregnancy and associated with childhood and adult obesity. Studies in children propose a link between POMC DNA methylation and elevated lipids and insulin, independent of body habitus. This review brings together evidence from animal and human studies and suggests that POMC is sensitive to nutritional programming and is associated with a wide range of weight-related and metabolic outcomes.

Effect of CREB1 promoter non-CpG island methylation on its differential expression profile on sheep ovaries associated with prolificacy

This study aimed to investigate the effect of different methylated regions of cyclic-AMP response element binding protein 1 (CREB1) by comparing the high prolificacy (HP) group and low prolificacy (LP) group, which was detected in our previous study. The expression level of CREB1 mRNA in the ovaries of the HP group was higher than in the LP group (P <  0.05). The differential methylated region (DMR) had 4 methylated CG dinucleotides(CGs): -1546, -1544, -1494 and -1464. The DNA methylation levels of -1546 CGs and -1464 CGs were significantly higher in the HP group than in the LP group (P <  0.05). The activity from -1296 to +26 (without DMR) was significantly higher than the activity from -1598 to +26 (with DMR) (P <  0.05). The result of 5-aza-2'-deoxycytidine treatment indicated that the inhibition DNA methylation of DMR reduced the transcription of CREB1. The bioinformatics predictive analysis were found that the -1546 CG site was located in the CCAAT/enhancer-binding protein alpha (CEBPA) binding site and the -1464 CG site was located in the Sp1 binding site. Finally, this study revealed the relationship between the methylation of non-CpG sites of the promoter and transcription of CREB1. This study will provide a theoretical basis of the Hu sheep ovaries associated with DNA methylation.

DNA-binding activity of STAT3 increased in hypothalamus of DIO mice; the reduction of STAT3 phosphorylation may facilitate leptin signaling

Leptin-mediated DNA-binding activity of STAT3 in hypothalamus plays crucial roles in the maintenance of energy homeostasis in lean mice; however its effects still remains unclear in case of leptin resistance in mice with diet induced obesity (DIO). In this study significant elevation of both basal and exogenously leptin-treated DNA-binding activity of STAT3 was detected using EMSA in the hypothalamus of male C57BL/6J mice fed high-fat diet for 10 wks, in concomitant with hyperleptinemia, high body weight, high fat mass, and hyperphagia as well as decreased POMC expression. The studies in vitro showed that both DNA binding activity and the proximal SBE of POMC promoter was essential to leptin-mediated POMC expression. However, the diminution of STAT3 phosphorylation, achieved by S3I-201 or a FoxO1 mutant, facilitated leptin-mediated POMC expression. The findings here demonstrated excess STAT3 activity negatively regulated POMC expression in hypothalamus of DIO mice, and suggested the limitation of STAT3 activity may promote leptin signaling.

Detecting genome-wide directional effects of transcription factor binding on polygenic disease risk

Biological interpretation of genome-wide association study data frequently involves assessing whether SNPs linked to a biological process, for example, binding of a transcription factor, show unsigned enrichment for disease signal. However, signed annotations quantifying whether each SNP allele promotes or hinders the biological process can enable stronger statements about disease mechanism. We introduce a method, signed linkage disequilibrium profile regression, for detecting genome-wide directional effects of signed functional annotations on disease risk. We validate the method via simulations and application to molecular quantitative trait loci in blood, recovering known transcriptional regulators. We apply the method to expression quantitative trait loci in 48 Genotype-Tissue Expression tissues, identifying 651 transcription factor-tissue associations including 30 with robust evidence of tissue specificity. We apply the method to 46 diseases and complex traits (average n = 290 K), identifying 77 annotation-trait associations representing 12 independent transcription factor-trait associations, and characterize the underlying transcriptional programs using gene-set enrichment analyses. Our results implicate new causal disease genes and new disease mechanisms.

Maternal overnutrition programs epigenetic changes in the regulatory regions of hypothalamic Pomc in the offspring of rats

Background and objective

Maternal overnutrition has been implicated in affecting the offspring by programming metabolic disorders such as obesity and diabetes, by mechanisms that are not clearly understood. This study aimed to determine the long-term impact of maternal high-fat (HF) diet feeding on epigenetic changes in the offspring’s hypothalamic Pomc gene, coding a key factor in the control of energy balance. Further, it aimed to study the additional effects of postnatal overnutrition on epigenetic programming by maternal nutrition.

Methods

Eight-week-old female Sprague–Dawley rats were fed HF diet or low-fat (LF) diet for 6 weeks before mating, and throughout gestation and lactation. At postnatal day 21, samples were collected from a third offspring and the remainder were weaned onto LF diet for 5 weeks, after which they were either fed LF or HF diet for 12 weeks, resulting in four groups of offspring differing by their maternal and postweaning diet.

Results

With maternal HF diet, offspring at weaning had rapid early weight gain, increased adiposity, and hyperleptinemia. The programmed adult offspring, subsequently fed LF diet, retained the increased body weight. Maternal HF diet combined with offspring HF diet caused more pronounced hyperphagia, fat mass, and insulin resistance. The ARC Pomc gene from programmed offspring at weaning showed hypermethylation in the enhancer (nPE1 and nPE2) regions and in the promoter sequence mediating leptin effects. Interestingly, hypermethylation at the Pomc promoter but not at the enhancer region persisted long term into adulthood in the programmed offspring. However, there were no additive effects on methylation levels in the regulatory regions of Pomc in programmed offspring fed a HF diet.

Conclusion

Maternal overnutrition programs long-term epigenetic alterations in the offspring’s hypothalamic Pomc promoter. This predisposes the offspring to metabolic disorders later in life.

DNA methylation directly downregulates human cathelicidin antimicrobial peptide gene (CAMP) promoter activity

LL-37, the active product of human cathelicidin antimicrobial peptide (CAMP) has a broad spectrum of antibacterial activity. LL-37 also has important physiological functions in immune regulation, angiogenesis and in modulating apoptosis. The roles of LL-37 in oral squamous cell carcinoma (OSCC) are still not clear. The correlation between DNA methylation and human CAMP expression is also unknown. Here human CAMP/LL-37 expression was assessed by immunohistochemistry in normal and OSCC tissues. The results indicated that low expression of CAMP/LL-37 correlated with histological differentiation and lymph node metastasis and also promoted tumor progression. A cell-specific methylation pattern in the promoter region of human CAMP was detected. Treatment with 5-aza-2'-deoxycytidine, a DNA demethylation reagent can increase human CAMP expression in epithelial cancer cells. The reporter assay showed that unmethylated human CAMP promoter activity was significantly higher than methylated promoter activity. Taken together, these results suggested that human CAMP/LL-37 might act as a tumor-suppressor in OSCC and DNA methylation might play roles during carcinogenesis via directly downregulating human CAMP promoter activity.

Preclinical models for obesity research

A multi-dimensional strategy to tackle the global obesity epidemic requires an in-depth understanding of the mechanisms that underlie this complex condition. Much of the current mechanistic knowledge has arisen from preclinical research performed mostly, but not exclusively, in laboratory mouse and rat strains. These experimental models mimic certain aspects of the human condition and its root causes, particularly the over-consumption of calories and unbalanced diets. As with human obesity, obesity in rodents is the result of complex gene–environment interactions. Here, we review the traditional monogenic models of obesity, their contemporary optogenetic and chemogenetic successors, and the use of dietary manipulations and meal-feeding regimes to recapitulate the complexity of human obesity. We critically appraise the strengths and weaknesses of these different models to explore the underlying mechanisms, including the neural circuits that drive behaviours such as appetite control. We also discuss the use of these models for testing and screening anti-obesity drugs, beneficial bio-actives, and nutritional strategies, with the goal of ultimately translating these findings for the treatment of human obesity.

Summary: We review genetic models of obesity, their optogenetic and chemogenetic successors, and the use of dietary manipulations and meal-feeding regimes.

Genome-wide methylation analysis reveals differentially methylated loci that are associated with an age-dependent increase in bovine fibroblast response to LPS

BACKGROUND

Differences in DNA methylation are known to contribute to the development of immune-related disorders in humans but relatively little is known about how methylation regulates immune function in cattle. Utilizing whole-transcriptome analyses of bovine dermal fibroblasts, we have previously identified an age and breed-dependent up-regulation of genes within the toll-like receptor 4 (TLR4) pathway that correlates with enhanced fibroblast production of IL-8 in response to lipopolysaccharide (LPS). Age-dependent differences in IL-8 production are abolished by treatment with 5-aza-2-deoxycytidine and Trichostatin A (AZA-TSA), suggesting epigenetic regulation of the innate response to LPS. In the current study, we performed reduced representation bisulfite sequencing (RRBS) on fibroblast cultures isolated from the same animals at 5- and 16-months of age to identify genes that exhibit variable methylation with age. To validate the role of methylation in gene expression, six innate response genes that were hyper-methylated in young animals were assessed by RT-qPCR in fibroblasts from animals at different ages and from different breeds.

RESULTS

We identified 14,094 differentially methylated CpGs (DMCs) that differed between fibroblast cultures at 5- versus 16-months of age. Of the 5065 DMCs that fell within gene regions, 1117 were located within promoters, 1057 were within gene exons and 2891 were within gene introns and 67% were more methylated in young cultures. Transcription factor enrichment of the promoter regions hyper-methylated in young cultures revealed significant regulation by the key pro-inflammatory regulator, NF-κB. Additionally, five out of six chosen genes (PIK3R1, FES, NFATC1, TNFSF13 and RORA) that were more methylated in young cultures showed a significant reduction in expression post-LPS treatment in comparison with older cultures. Two of these genes, FES and NFATC1, were similarly down-regulated in Angus cultures that also exhibit a low LPS response phenotype.

CONCLUSIONS

Our study has identified immune-related loci regulated by DNA methylation in cattle that may contribute to differential cellular response to LPS, two of which exhibit an identical expression profile in both low-responding age and breed phenotypes. Methylation biomarkers of differential immunity may prove useful in developing selection strategies for replacement cows that are less susceptible to severe infections, such as coliform mastitis.

DNA CpG Methylation (5-Methylcytosine) and Its Derivative (5-Hydroxymethylcytosine) Alter Histone Posttranslational Modifications at the Pomc Promoter, Affecting the Impact of Perinatal Diet on Leanness and Obesity of the Offspring

A maternal high-fat diet (HFD) alters the offspring's feeding regulation, leading to obesity. This phenomenon is partially mediated by aberrant expression of the hypothalamic anorexigenic neuropeptide proopiomelanocortin (POMC). Nevertheless, although some individual offspring suffer from morbid obesity, others escape the malprogramming. It is suggested that this difference is due to epigenetic programming. In this study, we report that in lean offspring of non-HFD-fed dams, essential promoter regions for Pomc expression were enriched with 5-hydroxymethylcytosine (5hmC) together with a reduction in the level of 5-methylcytosine (5mC). Moreover, 5hmC was negatively correlated whereas 5mC was positively correlated with body weight in offspring from both HFD- and control-fed dams. We further found that Pomc expression in obese offspring is determined by a two-step epigenetic inhibitory mechanism in which CpG methylation is linked with histone posttranslational modifications. An increase in CpG methylation at the Poxmc promoter enables binding of methyl-binding domain 1 (MBD1) to 5mC, but not to its derivative 5hmC. MBD1 then interacts with SET domain bifurcated 1 methyltransferase to promote bimethylation on the histone 3 lysine 9 residue, reducing Pomc mRNA expression. These results suggest an epigenetic regulatory mechanism that affects obesity-prone or resilient traits.

Epigenetic and SP1-mediated regulation is involved in the repression of galactokinase 1 gene in the liver of neonatal piglets born to betaine-supplemented sows

PURPOSE

In this study, we sought to investigate the effects of maternal betaine supplementation on the expression and regulation of GALK1 gene in the liver of neonatal piglets.

METHODS

Sixteen sows of two groups were fed control or betaine-supplemented diets (3 g/kg), respectively, throughout the pregnancy. Newborn piglets were individually weighed immediately after birth, and one male piglet close to mean body weight from the same litter was selected and killed before suckling. Serum samples of newborn piglets were analyzed for biochemical indexes, hormone and amino acid levels. Liver samples were analyzed for GALK1 expression by real-time PCR and western blotting, while GALK1 regulational mechanism was analyzed by methylated DNA immunoprecipitation, chromatin immunoprecipitation and microRNAs expression.

RESULTS

Betaine-exposed neonatal piglets had lower serum concentration of galactose, which was associated with significantly down-regulated hepatic GALK1 expression. The repression of GALK1 mRNA expression was associated with DNA hypermethylation and more enriched repression histone mark H3K27me3 on its promoter. Binding sites of SP1, GR and STAT3 were predicted on GALK1 promoter, and decreased SP1 protein content and lower SP1 binding to GALK1 promoter were detected in the liver of betaine-exposed piglets. Furthermore, the expression of miRNA-149 targeting GALK1 was up-regulated in the liver of betaine-exposed piglets, along with elevated miRNAs-processing enzymes Dicer and Ago2.

CONCLUSIONS

Our results suggest that maternal dietary betaine supplementation during gestation suppresses GALK1 expression in the liver of neonatal piglets, which involves complex gene regulation mechanisms including DNA methylation, histone modification, miRNAs expression and SP1-mediated transcriptional modulation.

ITPKA Gene Body Methylation Regulates Gene Expression and Serves as an Early Diagnostic Marker in Lung and Other Cancers

INTRODUCTION

Despite recent advances in cancer therapy, the overall 5-year survival rate of patients with lung cancer remains low. The aim of our study was to search for novel markers for early diagnosis in patients with lung cancer.

METHODS

Complementary DNA microarray analysis was performed in primary lung adenocarcinomas and cell lines to search for differentially expressed genes, followed by in vivo and in vitro tumorigenic assays to characterize the oncogenic potential of the candidate genes. Gene body methylation was analyzed by 450K methylation array, bisulfite sequencing, and quantitative methylation-specific polymerase chain reaction assays. In silico analysis of The Cancer Genome Atlas data set was also performed.

RESULTS

Inositol-trisphosphate 3-kinase A gene (ITPKA), a kinase with limited tissue distribution, was identified as a potential oncogene. We showed that ITPKA expression is up-regulated in many forms of cancers, including lung and breast cancers, and that overexpressed ITPKA contributes to tumorigenesis. We also demonstrated that ITPKA expression is regulated by epigenetic DNA methylation of ITPKA gene body through modulation of the binding of SP1 transcription factor to the ITPKA promoter. ITPKA gene body displayed low or absent levels of methylation in most normal tissue but was significantly methylated in malignant tumors. In lung cancer, ITPKA gene body methylation first appeared at the in situ carcinoma stage and progressively increased after invasion.

CONCLUSIONS

ITPKA is a potential oncogene that it is overexpressed in most tumors, and its overexpression promotes tumorigenesis. ITPKA gene body methylation regulates its expression and thus serves as a novel and potential biomarker for early cancer detection.

Neuroendocrinological and Epigenetic Mechanisms Subserving Autonomic Imbalance and HPA Dysfunction in the Metabolic Syndrome

Impact of environmental stress upon pathophysiology of the metabolic syndrome (MetS) has been substantiated by epidemiological, psychophysiological, and endocrinological studies. This review discusses recent advances in the understanding of causative roles of nutritional factors, sympathomedullo-adrenal (SMA) and hypothalamic-pituitary adrenocortical (HPA) axes, and adipose tissue chronic low-grade inflammation processes in MetS. Disturbances in the neuroendocrine systems for leptin, melanocortin, and neuropeptide Y (NPY)/agouti-related protein systems have been found resulting directly in MetS-like conditions. The review identifies candidate risk genes from factors shown critical for the functioning of each of these neuroendocrine signaling cascades. In its meta-analytic part, recent studies in epigenetic modification (histone methylation, acetylation, phosphorylation, ubiquitination) and posttranscriptional gene regulation by microRNAs are evaluated. Several studies suggest modification mechanisms of early life stress (ELS) and diet-induced obesity (DIO) programming in the hypothalamic regions with populations of POMC-expressing neurons. Epigenetic modifications were found in cortisol (here HSD11B1 expression), melanocortin, leptin, NPY, and adiponectin genes. With respect to adiposity genes, epigenetic modifications were documented for fat mass gene cluster APOA1/C3/A4/A5, and the lipolysis gene LIPE. With regard to inflammatory, immune and subcellular metabolism, PPARG, NKBF1, TNFA, TCF7C2, and those genes expressing cytochrome P450 family enzymes involved in steroidogenesis and in hepatic lipoproteins were documented for epigenetic modifications.

Glycerol-3-phosphate acyltransferase-1 upregulation by O-GlcNAcylation of Sp1 protects against hypoxia-induced mouse embryonic stem cell apoptosis via mTOR activation

Oxygen signaling is critical for stem cell regulation, and oxidative stress-induced stem cell apoptosis decreases the efficiency of stem cell therapy. Hypoxia activates O-linked β-N-acetyl glucosaminylation (O-GlcNAcylation) of stem cells, which contributes to regulation of cellular metabolism, as well as cell fate. Our study investigated the role of O-GlcNAcylation via glucosamine in the protection of hypoxia-induced apoptosis of mouse embryonic stem cells (mESCs). Hypoxia increased mESCs apoptosis in a time-dependent manner. Moreover, hypoxia also slightly increased the O-GlcNAc level. Glucosamine treatment further enhanced the O-GlcNAc level and prevented hypoxia-induced mESC apoptosis, which was suppressed by O-GlcNAc transferase inhibitors. In addition, hypoxia regulated several lipid metabolic enzymes, whereas glucosamine increased expression of glycerol-3-phosphate acyltransferase-1 (GPAT1), a lipid metabolic enzyme producing lysophosphatidic acid (LPA). In addition, glucosamine-increased O-GlcNAcylation of Sp1, which subsequently leads to Sp1 nuclear translocation and GPAT1 expression. Silencing of GPAT1 by gpat1 siRNA transfection reduced glucosamine-mediated anti-apoptosis in mESCs and reduced mammalian target of rapamycin (mTOR) phosphorylation. Indeed, LPA prevented mESCs from undergoing hypoxia-induced apoptosis and increased phosphorylation of mTOR and its substrates (S6K1 and 4EBP1). Moreover, mTOR inactivation by rapamycin (mTOR inhibitor) increased pro-apoptotic proteins expressions and mESC apoptosis. Furthermore, transplantation of non-targeting siRNA and glucosamine-treated mESCs increased cell survival and inhibited flap necrosis in mouse skin flap model. Conversely, silencing of GPAT1 expression reversed those glucosamine effects. In conclusion, enhancing O-GlcNAcylation of Sp1 by glucosamine stimulates GPAT1 expression, which leads to inhibition of hypoxia-induced mESC apoptosis via mTOR activation.

An assessment of molecular pathways of obesity susceptible to nutrient, toxicant and genetically induced epigenetic perturbation

In recent years, the etiology of human disease has greatly improved with the inclusion of epigenetic mechanisms, in particular as a common link between environment and disease. However, for most diseases we lack a detailed interpretation of the epigenetic regulatory pathways perturbed by environment and causal mechanisms. Here, we focus on recent findings elucidating nutrient-related epigenetic changes linked to obesity. We highlight studies demonstrating that obesity is a complex disease linked to disruption of epigenetically regulated metabolic pathways in the brain, adipose tissue and liver. These pathways regulate (1) homeostatic and hedonic eating behaviors, (2) adipocyte differentiation and fat accumulation, and (3) energy expenditure. By compiling these data, we illustrate that obesity-related phenotypes are repeatedly linked to disruption of critical epigenetic mechanisms that regulate key metabolic genes. These data are supported by genetic mutation of key epigenetic regulators, and many of the diet-induced epigenetic mechanisms of obesity are also perturbed by exposure to environmental toxicants. Identifying similarly perturbed epigenetic mechanisms in multiple experimental models of obesity strengthens the translational applications of these findings. We also discuss many of the ongoing challenges to understanding the role of environmentally induced epigenetic pathways in obesity and suggest future studies to elucidate these roles. This assessment illustrates our current understanding of molecular pathways of obesity that are susceptible to environmental perturbation via epigenetic mechanisms. Thus, it lays the groundwork for dissecting the complex interactions between diet, genes and toxicants that contribute to obesity and obesity-related phenotypes.

Inactivation of BLU is associated with methylation of Sp1-binding site of BLU promoter in gastric cancer

BLU is a candidate tumor suppressor gene, which is epigenetically inactivated in many human malignancies. However, the expression and biological functions of BLU in gastric cancer has not yet been reported. In the present study, we identified a functional BLU promoter which was regulated by the transcription activator Sp1. Bisulfite sequencing and qRT-PCR assays indicated that the silence of BLU expression in gastric cancer was significantly associated with DNA hypermethylation of BLU promoter including -39 CpG site located in the Sp1 transcription element. The expression of BLU was notably restored in AGS and SGC7901 cells following the demethylation-treatment with 5'-Aza-2'-deoxycytidine. Moreover, the results from ChIP, EMSA and luciferase reporter gene showed that -39 CpG methylation could prevent Sp1 from binding to the promoter of BLU and decreased transcription activity of the BLU gene by ~70%. In addition, knockdown of BLU significantly promoted cellular proliferation and colony formation in gastric cancer cells. In conclusion, we identified a novel functional BLU promoter and proved that BLU promoter activity was regulated by Sp1. Furthermore, we found that hypermethylated -39 CpG in BLU proximal promoter directly reduced its binding with Sp1, which may be one of the mechanisms accounting for the inactivation of BLU in gastric cancer.

Maternal supplementation with conjugated linoleic acid in the setting of diet-induced obesity normalises the inflammatory phenotype in mothers and reverses metabolic dysfunction and impaired insulin sensitivity in offspring

Maternal consumption of a high-fat diet significantly impacts the fetal environment and predisposes offspring to obesity and metabolic dysfunction during adulthood. We examined the effects of a high-fat diet during pregnancy and lactation on metabolic and inflammatory profiles and whether maternal supplementation with the anti-inflammatory lipid conjugated linoleic acid (CLA) could have beneficial effects on mothers and offspring. Sprague-Dawley rats were fed a control (CD; 10% kcal from fat), CLA (CLA; 10% kcal from fat, 1% total fat as CLA), high-fat (HF; 45% kcal from fat) or high fat with CLA (HFCLA; 45% kcal from fat, 1% total fat as CLA) diet ad libitum 10days prior to and throughout gestation and lactation. Dams and offspring were culled at either late gestation (fetal day 20, F20) or early postweaning (postnatal day 24, P24). CLA, HF and HFCLA dams were heavier than CD throughout gestation. Plasma concentrations of proinflammatory cytokines interleukin-1β and tumour necrosis factor-α were elevated in HF dams, with restoration in HFCLA dams. Male and female fetuses from HF dams were smaller at F20 but displayed catch-up growth and impaired insulin sensitivity at P24, which was reversed in HFCLA offspring. HFCLA dams at P24 were protected from impaired insulin sensitivity as compared to HF dams. Maternal CLA supplementation normalised inflammation associated with consumption of a high-fat diet and reversed associated programming of metabolic dysfunction in offspring. This demonstrates that there are critical windows of developmental plasticity in which the effects of an adverse early-life environment can be reversed by maternal dietary interventions.

Developmental programming of type 2 diabetes: early nutrition and epigenetic mechanisms

PURPOSE OF REVIEW

The environment experienced during critical windows of development can 'programme' long-term health and risk of metabolic diseases such as type 2 diabetes in the offspring. The purpose of this review is to discuss potential epigenetic mechanisms involved in the developmental programming of type 2 diabetes by early nutrition.

RECENT FINDINGS

Maternal and more recently paternal nutrition have been shown to play key roles in metabolic programming of the offspring. Although the exact mechanisms are still not clear, epigenetic processes have emerged as playing a plausible role. Epigenetic dysregulation is associated with several components that contribute to type 2 diabetes risk, including altered feeding behaviour, insulin secretion and insulin action. It may also contribute to transgenerational risk transmission.

SUMMARY

Epigenetic processes may represent a central underlying mechanism of developmental programming of type 2 diabetes. During embryonic and foetal development, extensive epigenetic remodelling takes place not only in somatic but also in primordial germ cells. Therefore, concerns have been raised that epigenetic dysregulation induced by a suboptimal early environment could programme altered phenotypes not only in the first generation but also in the subsequent ones. Characterizing these altered epigenetic marks has great implications for identifying individuals at an increased disease risk as well as potentially leading to novel preventive and treatment strategies.

Developmental programming of hypothalamic neuronal circuits: impact on energy balance control

The prevalence of obesity in adults and children has increased globally at an alarming rate. Mounting evidence from both epidemiological studies and animal models indicates that adult obesity and associated metabolic disorders can be programmed by intrauterine and early postnatal environment- a phenomenon known as "fetal programming of adult disease." Data from nutritional intervention studies in animals including maternal under- and over-nutrition support the developmental origins of obesity and metabolic syndrome. The hypothalamic neuronal circuits located in the arcuate nucleus controlling appetite and energy expenditure are set early in life and are perturbed by maternal nutritional insults. In this review, we focus on the effects of maternal nutrition in programming permanent changes in these hypothalamic circuits, with experimental evidence from animal models of maternal under- and over-nutrition. We discuss the epigenetic modifications which regulate hypothalamic gene expression as potential molecular mechanisms linking maternal diet during pregnancy to the offspring's risk of obesity at a later age. Understanding these mechanisms in key metabolic genes may provide insights into the development of preventative intervention strategies.