The Histone Demethylase UTX Promotes Brown Adipocyte Thermogenic Program Via Coordinated Regulation of H3K27 Demethylation and Acetylation

Dnmt3b deficiency in adipocyte progenitor cells ameliorates obesity in female mice

Obesity arises from chronic energy imbalance where energy intake exceeds energy expenditure. Emerging evidence supports a key role of DNA methylation in the regulation of adipose tissue development and metabolism. We recently discovered a key role of DNA methylation, catalyzed by DNA methyltransferase 1 or 3a (Dnmt1 or 3a), in the regulation of adipocyte differentiation and metabolism. Here, we aimed to investigate the role of adipocyte progenitor cell Dnmt3b, an enzyme mediating de novo DNA methylation, in energy metabolism and obesity. We generated a genetic model with Dnmt3b knockout in adipocyte progenitor cells (PD3bKO) by crossing Dnmt3b -floxed mice with platelet-derived growth factor receptor alpha (Pdgfrα)-Cre mice. Dnmt3b gene deletion in adipocyte progenitors enhanced thermogenic gene expression in brown adipose tissue, increased overall energy expenditure, and mitigated high-fat diet (HFD)-induced obesity in female mice. PD3bKO mice also displayed a lower respiratory exchange ratio (RER), indicative of a metabolic shift favoring fat utilization as an energy source. Furthermore, female PD3bKO mice exhibited improved insulin sensitivity alongside their lean phenotype. In contrast, male PD3bKO mice showed no changes in body weight but demonstrated decreased insulin sensitivity, revealing a sexually dimorphic metabolic response to Dnmt3b deletion in adipocyte progenitor cells. These findings underscore the critical role of Dnmt3b in regulating energy homeostasis, body weight, and metabolic health, with significant implications for understanding sex-specific mechanisms of obesity and metabolism.

Elevated EBF2 in mouse but not pig drives the progressive brown fat lineage specification via chromatin activation

Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis, but it is absent in some mammals, including pigs. During development, BAT progenitors are derived from paired box 7 (Pax7)-expressing somitic mesodermal stem cells, which also give rise to skeletal muscle. However, the intrinsic mechanisms underlying the fate decisions between brown fat and muscle progenitors remain elusive across species. In this study, we analyzed the dynamics of chromatin landscape during the segregation and specification of brown fat and muscle lineages from Pax7+ multipotent mesodermal stem cells, aiming to uncover epigenetic factors that drive de novo BAT formation. Notably, myogenic progenitors were specified at embryonic day (E) 12.5, exhibiting high levels of H3K4me3 and low H3K27me3 at muscle-related genes. In contrast, the specification of the BAT lineage occurred much later, with coordinated step-wise depositions of histone modifications at BAT-associated genes from E10.5 to E14.5. We identified the transcription factor early B-cell factor 2 (EBF2) as a key driver of the progressive specification of brown fat lineage and the simultaneous deviation away from the muscle lineage. Mechanistically, EBF2 interacts with transcriptional co-activators CREB binding protein/ E1A-binding protein p300 (CBP/P300) to induce H3K27ac deposition and chromatin activation at BAT-associated genes to promote brown adipogenesis. Both mouse and pig EBF2 could potently stimulate adipogenesis in unspecified multipotent mesodermal stem cells. However, in pigs, EBF2 expression was depleted during the critical lineage specification time window, thus preventing the embryonic formation and development of porcine BAT. Hence, the elevation of EBF2 in mice, but not in pigs, promote chromatin activation to drive the progressive specification of brown fat lineage.

Impact of heat and cold shock on epigenetics and chromatin structure

Cells are continuously exposed to various sources of insults, among which temperature variations are extremely common. Epigenetic mechanisms, critical players in gene expression regulation, undergo alterations due to these stressors, potentially leading to health issues. Despite the significance of DNA methylation and histone modifications in gene expression regulation, their changes following heat and cold shock in human cells remain poorly understood. In this study, we investigated the epigenetic profiles of human cells subjected to hyperthermia and hypothermia, revealing significant variations. Heat shock primarily led to DNA methylation increments and epigenetic modifications associated with gene expression silencing. In contrast, cold shock presented a complex scenario, with both methylation and demethylation levels increasing, indicating different epigenetic responses to the opposite thermal stresses. These temperature-induced alterations in the epigenome, particularly their impact on chromatin structural organization, represent an understudied area that could offer important insights into genome function and potential prospects for therapeutic targets.

An Updated Review on the Significance of DNA and Protein Methyltransferases and De-methylases in Human Diseases: From Molecular Mechanism to Novel Therapeutic Approaches

Epigenetic mechanisms are crucial in regulating gene expression. These mechanisms include DNA methylation and histone modifications, like methylation, acetylation, and phosphorylation. DNA methylation is associated with gene expression suppression; however, histone methylation can stimulate or repress gene expression depending on the methylation pattern of lysine or arginine residues on histones. These modifications are key factors in mediating the environmental effect on gene expression regulation. Therefore, their aberrant activity is associated with the development of various diseases. The current study aimed to review the significance of DNA and histone methyltransferases and demethylases in developing various conditions, like cardiovascular diseases, myopathies, diabetes, obesity, osteoporosis, cancer, aging, and central nervous system conditions. A better understanding of the epigenetic roles in developing diseases can pave the way for developing novel therapeutic approaches for affected patients.

Adipose tissue browning and thermogenesis under physiologically energetic challenges: a remodelled thermogenic system

Metabolic diseases such as obesity and diabetes are often thought to be caused by reduced energy expenditure, which poses a serious threat to human health. Cold exposure, exercise and caloric restriction have been shown to promote adipose tissue browning and thermogenesis. These physiological interventions increase energy expenditure and thus have emerged as promising strategies for mitigating metabolic disorders. However, that increased adipose tissue browning and thermogenesis elevate thermogenic consumption is not a reasonable explanation when humans and animals confront energetic challenges imposed by these interventions. In this review, we collected numerous results on adipose tissue browning and whitening and evaluated this bi-directional conversion of adipocytes from the perspective of energy homeostasis. Here, we propose a new interpretation of the role of adipose tissue browning under energetic challenges: increased adipose tissue browning and thermogenesis under energy challenge is not to enhance energy expenditure, but to reestablish a more economical thermogenic pattern to maintain the core body temperature. This can be achieved by enhancing the contribution of non-shivering thermogenesis (adipose tissue browning and thermogenesis) and lowering shivering thermogenesis and high intensity shivering. Consequently, the proportion of heat production in fat increases and that in skeletal muscle decreases, enabling skeletal muscle to devote more energy reserves to overcoming environmental stress.

Altered expression, but small contribution, of the histone demethylase KDM6A in obstructive uropathy in mice

Epigenetic processes have emerged as important modulators of kidney health and disease. Here, we studied the role of KDM6A (a histone demethylase that escapes X-chromosome inactivation) in kidney tubule epithelial cells. We initially observed an increase in tubule cell Kdm6a mRNA in male mice with unilateral ureteral obstruction (UUO). However, tubule cell knockout of KDM6A had relatively minor consequences, characterized by a small reduction in apoptosis, increase in inflammation and downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway. In proximal tubule lineage HK-2 cells, KDM6A knockdown decreased PPARγ coactivator-1α (PGC-1α) protein levels and mRNA levels of the encoding gene, PPARGC1A. Tubule cell Kdm6a mRNA levels were approximately 2-fold higher in female mice than in male mice, both under sham and UUO conditions. However, kidney fibrosis after UUO was similar in both sexes. The findings demonstrate Kdm6a to be a dynamically regulated gene in the kidney tubule, varying in expression levels by sex and in response to injury. Despite the context-dependent variation in Kdm6a expression, knockout of tubule cell KDM6A has subtle (albeit non-negligible) effects in the adult kidney, at least in males.

Molecular and cellular regulation of thermogenic fat

Thermogenic fat, consisting of brown and beige adipocytes, dissipates energy in the form of heat, in contrast to the characteristics of white adipocytes that store energy. Increasing energy expenditure by activating brown adipocytes or inducing beige adipocytes is a potential therapeutic strategy for treating obesity and type 2 diabetes. Thus, a better understanding of the underlying mechanisms of thermogenesis provides novel therapeutic interventions for metabolic diseases. In this review, we summarize the recent advances in the molecular regulation of thermogenesis, focusing on transcription factors, epigenetic regulators, metabolites, and non-coding RNAs. We further discuss the intercellular and inter-organ crosstalk that regulate thermogenesis, considering the heterogeneity and complex tissue microenvironment of thermogenic fat.

Epigenetic Regulation of Hepatic Lipid Metabolism by DNA Methylation

While extensive investigations have been devoted to the study of genetic pathways related to fatty liver diseases, much less is known about epigenetic mechanisms underlying these disorders. DNA methylation is an epigenetic link between environmental factors (e.g., diets) and complex diseases (e.g., non-alcoholic fatty liver disease). Here, it is aimed to study the role of DNA methylation in the regulation of hepatic lipid metabolism. A dynamic change in the DNA methylome in the liver of high-fat diet (HFD)-fed mice is discovered, including a marked increase in DNA methylation at the promoter of Beta-klotho (Klb), a co-receptor for the biological functions of fibroblast growth factor (FGF)15/19 and FGF21. DNA methyltransferases (DNMT) 1 and 3A mediate HFD-induced methylation at the Klb promoter. Notably, HFD enhances DNMT1 protein stability via a ubiquitination-mediated mechanism. Liver-specific deletion of Dnmt1 or 3a increases Klb expression and ameliorates HFD-induced hepatic steatosis. Single-nucleus RNA sequencing analysis reveals pathways involved in fatty acid oxidation in Dnmt1-deficient hepatocytes. Targeted demethylation at the Klb promoter increases Klb expression and fatty acid oxidation, resulting in decreased hepatic lipid accumulation. Up-regulation of methyltransferases by HFD may induce hypermethylation of the Klb promoter and subsequent down-regulation of Klb expression, resulting in the development of hepatic steatosis.

Glutamine metabolism in breast cancer and possible therapeutic targets

Cancer is characterized by metabolic reprogramming, which is a hot topic in tumor treatment research. Cancer cells alter metabolic pathways to promote their growth, and the common purpose of these altered metabolic pathways is to adapt the metabolic state to the uncontrolled proliferation of cancer cells. Most cancer cells in a state of nonhypoxia will increase the uptake of glucose and produce lactate, called the Warburg effect. Increased glucose consumption is used as a carbon source to support cell proliferation, including nucleotide, lipid and protein synthesis. In the Warburg effect, pyruvate dehydrogenase activity decreases, thereby disrupting the TCA cycle. In addition to glucose, glutamine is also an important nutrient for the growth and proliferation of cancer cells, an important carbon bank and nitrogen bank for the growth and proliferation of cancer cells, providing ribose, nonessential amino acids, citrate, and glycerin necessary for cancer cell growth and proliferation and compensating for the reduction in oxidative phosphorylation pathways in cancer cells caused by the Warburg effect. In human plasma, glutamine is the most abundant amino acid. Normal cells produce glutamine via glutamine synthase (GLS), but the glutamine synthesized by tumor cells is insufficient to meet their high growth needs, resulting in a "glutamine-dependent phenomenon." Most cancers have an increased glutamine demand, including breast cancer. Metabolic reprogramming not only enables tumor cells to maintain the reduction-oxidation (redox) balance and commit resources to biosynthesis but also establishes heterogeneous metabolic phenotypes of tumor cells that are distinct from those of nontumor cells. Thus, targeting the metabolic differences between tumor and nontumor cells may be a promising and novel anticancer strategy. Glutamine metabolic compartments have emerged as promising candidates, especially in TNBC and drug-resistant breast cancer. In this review, the latest discoveries of breast cancer and glutamine metabolism are discussed, novel treatment methods based on amino acid transporters and glutaminase are discussed, and the relationship between glutamine metabolism and breast cancer metastasis, drug resistance, tumor immunity and ferroptosis are explained, which provides new ideas for the clinical treatment of breast cancer.

Transcriptome Analysis of Beet Webworm Shows That Histone Deacetylase May Affect Diapause by Regulating Juvenile Hormone

The beet webworm (Loxostege sticticalis L.) is an important agricultural pest and can tolerate harsh environmental conditions by entering diapause. The diapause mechanism of beet webworm is unknown. Therefore, we conducted a transcriptomic study of the process from diapause induction to diapause release in beet webworms. The results revealed 393 gene modules closely related to the diapause of beet webworm. The hub gene of the red module was the HDACI gene, which acts through histone deacetylase (HDAC) enzymes. HDAC enzyme activity was regulated by the light duration and influenced the JH content under induced beet webworm diapause conditions (12 h light:12 h dark). In addition, transcriptomic data suggested that circadian genes may not be the key genes responsible for beet webworm diapause. However, we showed that the photoperiod affects HDAC enzyme activity, and HDAC can regulate the involvement of JH in beet webworm diapause. This study provided a new module for studying insect diapause and links histone acetylation and diapause at the transcriptome level.

Interplay Among Metabolism, Epigenetic Modifications, and Gene Expression in Cancer

Epigenetic modifications and metabolism are two fundamental biological processes. During tumorigenesis and cancer development both epigenetic and metabolic alterations occur and are often intertwined together. Epigenetic modifications contribute to metabolic reprogramming by modifying the transcriptional regulation of metabolic enzymes, which is crucial for glucose metabolism, lipid metabolism, and amino acid metabolism. Metabolites provide substrates for epigenetic modifications, including histone modification (methylation, acetylation, and phosphorylation), DNA and RNA methylation and non-coding RNAs. Simultaneously, some metabolites can also serve as substrates for nonhistone post-translational modifications that have an impact on the development of tumors. And metabolic enzymes also regulate epigenetic modifications independent of their metabolites. In addition, metabolites produced by gut microbiota influence host metabolism. Understanding the crosstalk among metabolism, epigenetic modifications, and gene expression in cancer may help researchers explore the mechanisms of carcinogenesis and progression to metastasis, thereby provide strategies for the prevention and therapy of cancer. In this review, we summarize the progress in the understanding of the interactions between cancer metabolism and epigenetics.

Adipocyte Utx Deficiency Promotes High-Fat Diet-Induced Metabolic Dysfunction in Mice

While the main function of white adipose tissue (WAT) is to store surplus of energy as triacylglycerol, that of brown adipose tissue (BAT) is to burn energy as heat. Epigenetic mechanisms participate prominently in both WAT and BAT energy metabolism. We previously reported that the histone demethylase ubiquitously transcribed tetratricopeptide (Utx) is a positive regulator of brown adipocyte thermogenesis. Here, we aimed to investigate whether Utx also regulates WAT metabolism in vivo. We generated a mouse model with Utx deficiency in adipocytes (AUTXKO). AUTXKO animals fed a chow diet had higher body weight, more fat mass and impaired glucose tolerance. AUTXKO mice also exhibited cold intolerance with an impaired brown fat thermogenic program. When challenged with high-fat diet (HFD), AUTXKO mice displayed adipose dysfunction featured by suppressed lipogenic pathways, exacerbated inflammation and fibrosis with less fat storage in adipose tissues and more lipid storage in the liver; as a result, AUTXKO mice showed a disturbance in whole body glucose homeostasis and hepatic steatosis. Our data demonstrate that Utx deficiency in adipocytes limits adipose tissue expansion under HFD challenge and induces metabolic dysfunction via adipose tissue remodeling. We conclude that adipocyte Utx is a key regulator of systemic metabolic homeostasis.

Histone demethylase UTX aggravates acetaminophen overdose induced hepatotoxicity through dual mechanisms

Acetaminophen (APAP) overdose is a major cause of acute liver failure, while the underlying mechanisms of APAP hepatotoxicity are not fully understood. Recently, emerging evidence suggests that epigenetic enzymes play roles in APAP-induced liver injury. Here, we found that Utx (ubiquitously transcribed tetratricopeptide repeat, X chromosome, also known as KDM6A), a X-linked histone demethylase which removes the di- and tri-methyl groups from histone H3K27, was markedly induced in the liver of APAP-overdosed female mice. Hepatic deletion of Utx suppressed APAP overdose-induced hepatotoxicity in female but not male mice. RNA-sequencing analysis suggested that Utx deficiency in female mice upregulated antitoxic phase II conjugating enzymes, including sulfotransferase family 2 A member 1 (Sult2a1), thus reduces the amount of toxic APAP metabolites in injured liver; while Utx deficiency also alleviated ER stress through downregulating transcription of ER stress genes including Atf4, Atf3, and Chop. Mechanistically, Utx promoted transcription of ER stress related genes in a demethylase activity-dependent manner, while repressed Sult2a1 expression through mediating H3K27ac levels independent of its demethylase activity. Moreover, overexpression of Sult2a1 in the liver of female mice rescued APAP-overdose induced liver injury. Together, our results indicated a novel UTX-Sult2a1 axis for the prevention or treatment of APAP-induced liver injury.

Brown Fat Dnmt3b Deficiency Ameliorates Obesity in Female Mice

Obesity results from a chronic energy imbalance due to energy intake exceeding energy expenditure. Activation of brown fat thermogenesis has been shown to combat obesity. Epigenetic regulation, including DNA methylation, has emerged as a key regulator of brown fat thermogenic function. Here we aimed to study the role of Dnmt3b, a DNA methyltransferase involved in de novo DNA methylation, in the regulation of brown fat thermogenesis and obesity. We found that the specific deletion of Dnmt3b in brown fat promotes the thermogenic and mitochondrial program in brown fat, enhances energy expenditure, and decreases adiposity in female mice fed a regular chow diet. With a lean phenotype, the female knockout mice also exhibit increased insulin sensitivity. In addition, Dnmt3b deficiency in brown fat also prevents diet-induced obesity and insulin resistance in female mice. Interestingly, our RNA-seq analysis revealed an upregulation of the PI3K-Akt pathway in the brown fat of female Dnmt3b knockout mice. However, male Dnmt3b knockout mice have no change in their body weight, suggesting the existence of sexual dimorphism in the brown fat Dnmt3b knockout model. Our data demonstrate that Dnmt3b plays an important role in the regulation of brown fat function, energy metabolism and obesity in female mice.

Epigenetic interaction between UTX and DNMT1 regulates diet-induced myogenic remodeling in brown fat

Brown adipocytes share the same developmental origin with skeletal muscle. Here we find that a brown adipocyte-to-myocyte remodeling also exists in mature brown adipocytes, and is induced by prolonged high fat diet (HFD) feeding, leading to brown fat dysfunction. This process is regulated by the interaction of epigenetic pathways involving histone and DNA methylation. In mature brown adipocytes, the histone demethylase UTX maintains persistent demethylation of the repressive mark H3K27me3 at Prdm16 promoter, leading to high Prdm16 expression. PRDM16 then recruits DNA methyltransferase DNMT1 to Myod1 promoter, causing Myod1 promoter hypermethylation and suppressing its expression. The interaction between PRDM16 and DNMT1 coordinately serves to maintain brown adipocyte identity while repressing myogenic remodeling in mature brown adipocytes, thus promoting their active brown adipocyte thermogenic function. Suppressing this interaction by HFD feeding induces brown adipocyte-to-myocyte remodeling, which limits brown adipocyte thermogenic capacity and compromises diet-induced thermogenesis, leading to the development of obesity.

Epigenetic regulation of energy metabolism in obesity

Obesity has reached epidemic proportions globally. Although modern adoption of a sedentary lifestyle coupled with energy-dense nutrition is considered to be the main cause of obesity epidemic, genetic preposition contributes significantly to the imbalanced energy metabolism in obesity. However, the variants of genetic loci identified from large-scale genetic studies do not appear to fully explain the rapid increase in obesity epidemic in the last four to five decades. Recent advancements of next-generation sequencing technologies and studies of tissue-specific effects of epigenetic factors in metabolic organs have significantly advanced our understanding of epigenetic regulation of energy metabolism in obesity. The epigenome, including DNA methylation, histone modifications, and RNA-mediated processes, is characterized as mitotically or meiotically heritable changes in gene function without alteration of DNA sequence. Importantly, epigenetic modifications are reversible. Therefore, comprehensively understanding the landscape of epigenetic regulation of energy metabolism could unravel novel molecular targets for obesity treatment. In this review, we summarize the current knowledge on the roles of DNA methylation, histone modifications such as methylation and acetylation, and RNA-mediated processes in regulating energy metabolism. We also discuss the effects of lifestyle modifications and therapeutic agents on epigenetic regulation of energy metabolism in obesity.

Prognostic value of glutaminase 1 in breast cancer depends on H3K27me3 expression and menopausal status

Glutaminase 1 (GLS) is a therapeutic target for breast cancer; although GLS inhibitors have been developed, only a few subjects responded well to the therapy. Considering that the expression of histone H3 lysine 27 trimethylation (H3K27me3) and menopausal status was closely linked to GLS, we examined the effects of H3K27me3 and menopausal status on GLS to breast cancer prognosis. Data for 962 women diagnosed with primary invasive breast cancer were analyzed. H3K27me3 and GLS expression in tumors were evaluated with tissue microarrays by immunohistochemistry. Hazard ratios (HRs) and their 95% confidence intervals (CIs) for overall survival and progression-free survival were estimated using Cox regression models. Statistical interaction was assessed on multiplicative scale. There was a beneficial prognostic effect of GLS expression on overall survival for those with low H3K27me3 level (HR = 0.50, 95% CI: 0.20-1.28) but an adverse prognostic effect for those with high H3K27me3 level (HR = 3.90, 95% CI: 1.29-11.78) among premenopausal women, and the statistical interaction was significant (P_interaction = 0.003). Similar pattern was further observed for progression-free survival (HR = 0.44, 95% CI: 0.20-0.95 for low H3K27me3 level, HR = 1.35, 95% CI: 0.74-2.48 for high H3K27me3 level, P_interaction = 0.024). The statistical interaction did not occur among postmenopausal women. Our study showed that the prognostic effects of GLS on breast cancer correlated to the expression level of H3K27me3 and menopausal status, which would help optimize the medication strategies of GLS inhibitors.

Adipose tissue-derived neurotrophic factor 3 regulates sympathetic innervation and thermogenesis in adipose tissue

Activation of brown fat thermogenesis increases energy expenditure and alleviates obesity. Sympathetic nervous system (SNS) is important in brown/beige adipocyte thermogenesis. Here we discover a fat-derived "adipokine" neurotrophic factor neurotrophin 3 (NT-3) and its receptor Tropomyosin receptor kinase C (TRKC) as key regulators of SNS growth and innervation in adipose tissue. NT-3 is highly expressed in brown/beige adipocytes, and potently stimulates sympathetic neuron neurite growth. NT-3/TRKC regulates a plethora of pathways in neuronal axonal growth and elongation. Adipose tissue sympathetic innervation is significantly increased in mice with adipocyte-specific NT-3 overexpression, but profoundly reduced in mice with TRKC haploinsufficiency (TRKC +/-). Increasing NT-3 via pharmacological or genetic approach promotes beige adipocyte development, enhances cold-induced thermogenesis and protects against diet-induced obesity (DIO); whereas TRKC + /- or SNS TRKC deficient mice are cold intolerant and prone to DIO. Thus, NT-3 is a fat-derived neurotrophic factor that regulates SNS innervation, energy metabolism and obesity.

Dnmt3b Deficiency in Myf5+-Brown Fat Precursor Cells Promotes Obesity in Female Mice

Increasing energy expenditure through activation of brown fat thermogenesis is a promising therapeutic strategy for the treatment of obesity. Epigenetic regulation has emerged as a key player in regulating brown fat development and thermogenic program. Here, we aimed to study the role of DNA methyltransferase 3b (Dnmt3b), a DNA methyltransferase involved in de novo DNA methylation, in the regulation of brown fat function and energy homeostasis. We generated a genetic model with Dnmt3b deletion in brown fat-skeletal lineage precursor cells (3bKO mice) by crossing Dnmt3b-floxed (fl/fl) mice with Myf5-Cre mice. Female 3bKO mice are prone to diet-induced obesity, which is associated with decreased energy expenditure. Dnmt3b deficiency also impairs cold-induced thermogenic program in brown fat. Surprisingly, further RNA-seq analysis reveals a profound up-regulation of myogenic markers in brown fat of 3bKO mice, suggesting a myocyte-like remodeling in brown fat. Further motif enrichment and pyrosequencing analysis suggests myocyte enhancer factor 2C (Mef2c) as a mediator for the myogenic alteration in Dnmt3b-deficient brown fat, as indicated by decreased methylation at its promoter. Our data demonstrate that brown fat Dnmt3b is a key regulator of brown fat development, energy metabolism and obesity in female mice.

Histone H3 methyltransferase Ezh2 promotes white adipocytes but inhibits brown and beige adipocyte differentiation in mice

Obesity is a disease characterized by imbalance between energy intake and expenditure, excessive energy store in white adipocytes, but brown and beige adipocytes consume energy to relieve obesity. In this study, we want to explore the role of the histone H3 methyltransferase Ezh2 in the differentiation of white, brown and beige adipocytes with Ezh2 conditional knockout mice (Ezh2flox/floxPrx1-cre) and mouse embryonic fibroblasts (MEFs). The results showed that Ezh2-deficient mice have a leaner phenotype and less white adipose tissues. The morphological changes in the adipose tissue included smaller white adipose tissue depots, white adipocytes with smaller diameter, smaller lipid droplets inside the brown adipocytes and more beige adipocytes in the Ezh2-deficient mice compared with the control. The differentiation markers of white adipocytes in Ezh2 knockout mice decreased; Ucp1 and other browning markers increased in brown and beige adipocytes. The Ezh2 knockout mice could better tolerate cold stimulation, and they can also resist obesity and insulin resistance induced by a high-fat diet. The Ezh2 inhibitor GSK126 could inhibit the differentiation of MEFs into white adipocytes but promote their differentiation into brown/beige adipocytes. The H3K27me3 demethylase Jmjd3/UTX inhibitor GSKJ4 inhibited MEFs' differentiation into brown/beige adipocytes. These results showed that Ezh2 promotes the differentiation of white adipocytes and inhibits the differentiation of brown and beige adipocytes in vivo and in vitro through its methylase activity and this may represent new knowledge for obesity therapeutic strategy.

Thermogenic Fat: Development, Physiological Function, and Therapeutic Potential

The concerning worldwide increase of obesity and chronic metabolic diseases, such as T2D, dyslipidemia, and cardiovascular disease, motivates further investigations into preventive and alternative therapeutic approaches. Over the past decade, there has been growing evidence that the formation and activation of thermogenic adipocytes (brown and beige) may serve as therapy to treat obesity and its associated diseases owing to its capacity to increase energy expenditure and to modulate circulating lipids and glucose levels. Thus, understanding the molecular mechanism of brown and beige adipocytes formation and activation will facilitate the development of strategies to combat metabolic disorders. Here, we provide a comprehensive overview of pathways and players involved in the development of brown and beige fat, as well as the role of thermogenic adipocytes in energy homeostasis and metabolism. Furthermore, we discuss the alterations in brown and beige adipose tissue function during obesity and explore the therapeutic potential of thermogenic activation to treat metabolic syndrome.

Identification of Dacinostat as a potential anti-obesity compound through transcriptional activation of adipose thermogenesis in mice

Obesity is a worldwide health problem. Activating fat mobilization and reducing fat synthesis is a promising strategy to mitigate obesity and its complicated metabolic diseases. However, few clinically effective and safe agents conform to the strategy. In the present study, by screening the next-generation L1000-based CMAP small molecule library, we identify histone deacetylase inhibitor Dacinostat, which has been previously tested in clinical trials for patients with advanced solid tumors, as an anti-obesity candidate. Administration of Dacinostat prevents high-fat diet-induced obesity, insulin resistance, and fatty liver in mice without causing adverse effects. Dacinostat treatment enhances adipose thermogenesis as shown by elevated body temperature, accompanied with high mRNA expression of Ucp1 and Ppargc1α. Mechanistically, we show that the thermogenic effect of Dacinostat is achieved by acetylation of histone 3 lysine 27 mediated transcriptional activation of Ucp1 and Ppargc1α in adipose tissue. In conclusion, these findings suggest that Dacinostat is a potential anti-obesity compound through transcriptional activation of adipose thermogenesis.

Epigenetic Regulators of White Adipocyte Browning

Adipocytes play an essential role in maintaining energy homeostasis in mammals. The primary function of white adipose tissue (WAT) is to store energy; for brown adipose tissue (BAT), primary function is to release fats in the form of heat. Dysfunctional or excess WAT can induce metabolic disorders such as dyslipidemia, obesity, and diabetes. Preadipocytes or adipocytes from WAT possess sufficient plasticity as they can transdifferentiate into brown-like beige adipocytes. Studies in both humans and rodents showed that brown and beige adipocytes could improve metabolic health and protect from metabolic disorders. Brown fat requires activation via exposure to cold or β-adrenergic receptor (β-AR) agonists to protect from hypothermia. Considering the fact that the usage of β-AR agonists is still in question with their associated side effects, selective induction of WAT browning is therapeutically important instead of activating of BAT. Hence, a better understanding of the molecular mechanisms governing white adipocyte browning is vital. At the same time, it is also essential to understand the factors that define white adipocyte identity and inhibit white adipocyte browning. This literature review is a comprehensive and focused update on the epigenetic regulators crucial for differentiation and browning of white adipocytes.

White adipose remodeling during browning in mice involves YBX1 to drive thermogenic commitment

Objective

Increasing adaptive thermogenesis by stimulating browning in white adipose tissue is a promising method of improving metabolic health. However, the molecular mechanisms underlying this transition remain elusive. Our study examined the molecular determinants driving the differentiation of precursor cells into thermogenic adipocytes.

Methods

In this study, we conducted temporal high-resolution proteomic analysis of subcutaneous white adipose tissue (scWAT) after cold exposure in mice. This was followed by loss- and gain-of-function experiments using siRNA-mediated knockdown and CRISPRa-mediated induction of gene expression, respectively, to evaluate the function of the transcriptional regulator Y box-binding protein 1 (YBX1) during adipogenesis of brown pre-adipocytes and mesenchymal stem cells. Transcriptomic analysis of mesenchymal stem cells following induction of endogenous Ybx1 expression was conducted to elucidate transcriptomic events controlled by YBX1 during adipogenesis.

Results

Our proteomics analysis uncovered 509 proteins differentially regulated by cold in a time-dependent manner. Overall, 44 transcriptional regulators were acutely upregulated following cold exposure, among which included the cold-shock domain containing protein YBX1, peaking after 24 h. Cold-induced upregulation of YBX1 also occurred in brown adipose tissue, but not in visceral white adipose tissue, suggesting a role of YBX1 in thermogenesis. This role was confirmed by Ybx1 knockdown in brown and brite preadipocytes, which significantly impaired their thermogenic potential. Conversely, inducing Ybx1 expression in mesenchymal stem cells during adipogenesis promoted browning concurrent with an increased expression of thermogenic markers and enhanced mitochondrial respiration. At a molecular level, our transcriptomic analysis showed that YBX1 regulates a subset of genes, including the histone H3K9 demethylase Jmjd1c, to promote thermogenic adipocyte differentiation.

Conclusion

Our study mapped the dynamic proteomic changes of murine scWAT during browning and identified YBX1 as a novel factor coordinating the genomic mechanisms by which preadipocytes commit to brite/beige lineage.

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Dynamic proteome remodeling occurs in mouse subcutaneous white fat with cold.

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YBX1 acutely increases in response to cold in thermogenic adipose tissues.

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YBX1 is required for the optimal implementation of the early thermogenic program.

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YBX1 promotes metabolic and thermogenic programs and enhances mitochondrial respiration.

The histone methyltransferase Suv39h regulates 3T3-L1 adipogenesis

We discovered a unique expression pattern of two histone methyltransferases Suv39h1 and Suv39h2 during 3T3-L1 adipogenesis, both of which preferentially catalyse the formation of H3K9 dimethylation (H3K9me2) and further H3K9 trimethylation (H3K9me3), a transcriptional repressive mark. The expression of Suv39h1 and Suv39h2 displayed a sharp increase at the early stage of 3T3-L1 differentiation, which peaked after differentiation induction, and then declined towards later stage of differentiation, suggesting a key role for these two histone methyltransferases in adipogenesis. Indeed, inactivating Suv39h1 or Suv39h2 via lentiviral shRNA knockdown inhibited adipogenesis, while overexpressing Suv39h1 promoted adipogenesis. Notably, overexpressing or knocking down Suv39h1 in 3T3-L1 cells was associated with reciprocal changes in the expression of Wnt10a, an anti-adipogenic regulator. Further, Wnt10a knockdown largely prevented the inhibitory effect of Suv39h1 on adipogenesis, indicating Wnt10a as a downstream target mediating Suv39h1’s action in adipogenesis. Mechanistically, our comprehensive approaches involving ChIP, co-immunoprecipitation and pyrosequencing analysis demonstrated that Suv39h1 may regulate Wnt10a expression via H3K9 methylation and interaction with DNA methyltransferase 1 (DNMT1) at the Wnt10a promoter, resulting in altered DNA methylation at the promoter. We conclude that Suv39h promotes adipogenesis by epigenetically down-regulating Wnt10a expression via H3K9me3 and DNA methylation at the Wnt10a promoter.Abbreviated title: Suv39h and 3T3-L1 Adipogenesis

A bioluminescent probe for longitudinal monitoring of mitochondrial membrane potential

Mitochondrial membrane potential (ΔΨm) is a universal selective indicator of mitochondrial function and is known to play a central role in many human pathologies, such as diabetes mellitus, cancer and Alzheimer's and Parkinson's diseases. Here, we report the design, synthesis and several applications of mitochondria-activatable luciferin (MAL), a bioluminescent probe sensitive to ΔΨm, and partially to plasma membrane potential (ΔΨp), for non-invasive, longitudinal monitoring of ΔΨm in vitro and in vivo. We applied this new technology to evaluate the aging-related change of ΔΨm in mice and showed that nicotinamide riboside (NR) reverts aging-related mitochondrial depolarization, revealing another important aspect of the mechanism of action of this potent biomolecule. In addition, we demonstrated application of the MAL probe for studies of brown adipose tissue (BAT) activation and non-invasive in vivo assessment of ΔΨm in animal cancer models, opening exciting opportunities for understanding the underlying mechanisms and for discovery of effective treatments for many human pathologies.

Understanding Dietary Intervention-Mediated Epigenetic Modifications in Metabolic Diseases

The global prevalence of metabolic disorders, such as obesity, diabetes and fatty liver disease, is dramatically increasing. Both genetic and environmental factors are well-known contributors to the development of these diseases and therefore, the study of epigenetics can provide additional mechanistic insight. Dietary interventions, including caloric restriction, intermittent fasting or time-restricted feeding, have shown promising improvements in patients' overall metabolic profiles (i.e., reduced body weight, improved glucose homeostasis), and an increasing number of studies have associated these beneficial effects with epigenetic alterations. In this article, we review epigenetic changes involved in both metabolic diseases and dietary interventions in primary metabolic tissues (i.e., adipose, liver, and pancreas) in hopes of elucidating potential biomarkers and therapeutic targets for disease prevention and treatment.

KMT5c modulates adipocyte thermogenesis by regulating Trp53 expression

Brown and beige adipocytes harbor the thermogenic capacity to adapt to environmental thermal or nutritional changes. Histone methylation is an essential epigenetic modification involved in the modulation of nonshivering thermogenesis in adipocytes. Here, we describe a molecular network leading by KMT5c, a H4K20 methyltransferase, that regulates adipocyte thermogenesis and systemic energy expenditure. The expression of Kmt5c is dramatically induced by a β3-adrenergic signaling cascade in both brown and beige fat cells. Depleting Kmt5c in adipocytes in vivo leads to a decreased expression of thermogenic genes in both brown and subcutaneous (s.c.) fat tissues. These mice are prone to high-fat-diet-induced obesity and develop glucose intolerance. Enhanced transformation related protein 53 (Trp53) expression in Kmt5c knockout (KO) mice, that is due to the decreased repressive mark H4K20me3 on its proximal promoter, is responsible for the metabolic phenotypes. Together, these findings reveal the physiological role for KMT5c-mediated H4K20 methylation in the maintenance and activation of the thermogenic program in adipocytes.

Can the aging influence cold environment mediated cancer risk in the USA female population?

Cancer is one of the most debilitating diseases worldwide. Cancer incidence and/or death depends on several intrinsic and extrinsic factors (e.g., dietary habits, socio-behavioral activities, physical inactivity, smoking, alcohol consumption, gender, races/ethnicities and age). Various studies have found that an inverse relationship subsists between environmental temperature and cancer risk. Furthermore, this negative relationship was found to be more consistent in the USA female population. This research mainly focuses on influence of aging on cold environment mediated cancer risk for overall and various anatomical site-specific cancers. Age-specific county-wise data of cancer incidence rate (CIR) in the USA female population was selected in this study. Statistical analysis found a negative correlation between the average annual temperature (AAT) and CIR in all anatomical sites (AAS; overall) as well as different anatomical site-specific cancers (e.g., breast, melanoma, leukaemia, pancreas, bladder, uterus, thyroid and non-Hodgkin's lymphoma (NHL), except for cervical cancer) in different age groups (e.g., less than 50 years, 50 plus years, less than 65 years and 65 plus years). In addition, an inverse relationship between the AAT and CIR was found in case of paediatric cancer. However, all the results obtained from the linear model based statistical analysis proposed that the older age-group of females particularly above 65 years seems to be more prone to cold temperature linked cancer risk. For example, age-specific cold linked cancer incidence appears to be more inclined in case of breast cancer in the age-group of 65 plus years. This study, for first time, proposes that aging may have a positive influence on the relationship between cancer incidence and environment temperature.

Inhibition of HDAC1/2 Along with TRAP1 Causes Synthetic Lethality in Glioblastoma Model Systems

The heterogeneity of glioblastomas, the most common primary malignant brain tumor, remains a significant challenge for the treatment of these devastating tumors. Therefore, novel combination treatments are warranted. Here, we showed that the combined inhibition of TRAP1 by gamitrinib and histone deacetylases (HDAC1/HDAC2) through romidepsin or panobinostat caused synergistic growth reduction of established and patient-derived xenograft (PDX) glioblastoma cells. This was accompanied by enhanced cell death with features of apoptosis and activation of caspases. The combination treatment modulated the levels of pro- and anti-apoptotic Bcl-2 family members, including BIM and Noxa, Mcl-1, Bcl-2 and Bcl-xL. Silencing of Noxa, BAK and BAX attenuated the effects of the combination treatment. At the metabolic level, the combination treatment led to an enhanced reduction of oxygen consumption rate and elicited an unfolded stress response. Finally, we tested whether the combination treatment of gamitrinib and panobinostat exerted therapeutic efficacy in PDX models of glioblastoma (GBM) in mice. While single treatments led to mild to moderate reduction in tumor growth, the combination treatment suppressed tumor growth significantly stronger than single treatments without induction of toxicity. Taken together, we have provided evidence that simultaneous targeting of TRAP1 and HDAC1/2 is efficacious to reduce tumor growth in model systems of glioblastoma.

Cold-hearted: A case for cold stress in cancer risk

A negative correlation exists between environmental temperature and cancer risk based on both epidemiological and statistical analyses. Previously, cold stress was reported to be an effective cause of tumorigenesis. Several studies have demonstrated that cold temperature serves as a potential risk factor in cancer development. Most recently, a link was demonstrated between the effects of extreme cold climate on cancer incidence, pinpointing its impact on tumour suppressor genes by causing mutation. The underlying mechanism behind cold stress and its association with tumorigenesis is not well understood. Hence, this review intends to shed light on the role of associated factors, genetic and/or non-genetic, which are modulated by cold temperature, and eventually influence tumorigenic potential. While scrutinizing the effect of cold exposure on the body, the expression of certain genes, e.g. uncoupled proteins and heat-shock proteins, were elevated. Biological chemicals such as norepinephrine, thyroxine, and cholesterol were also elevated. Brown adipose tissue, which plays an essential role in thermogenesis, displayed enhanced activity upon cold exposure. Adaptive measures are utilized by the body to tolerate the cold, and in doing so, invites both epigenetic and genetic changes. Unknowingly, these adaptive strategies give rise to a lethal outcome i.e., genesis of cancer. Concisely, this review attempts to draw a link between cold stress, genetic and epigenetic changes, and tumorigenesis and aspires to ascertain the mechanism behind cold temperature-mediated cancer risk.

HNF1A recruits KDM6A to activate differentiated acinar cell programs that suppress pancreatic cancer

Defects in transcriptional regulators of pancreatic exocrine differentiation have been implicated in pancreatic tumorigenesis, but the molecular mechanisms are poorly understood. The locus encoding the transcription factor HNF1A harbors susceptibility variants for pancreatic ductal adenocarcinoma (PDAC), while KDM6A, encoding Lysine-specific demethylase 6A, carries somatic mutations in PDAC. Here, we show that pancreas-specific Hnf1a null mutant transcriptomes phenocopy those of Kdm6a mutations, and both defects synergize with KrasG12D to cause PDAC with sarcomatoid features. We combine genetic, epigenomic, and biochemical studies to show that HNF1A recruits KDM6A to genomic binding sites in pancreatic acinar cells. This remodels the acinar enhancer landscape, activates differentiated acinar cell programs, and indirectly suppresses oncogenic and epithelial-mesenchymal transition genes. We also identify a subset of non-classical PDAC samples that exhibit the HNF1A/KDM6A-deficient molecular phenotype. These findings provide direct genetic evidence that HNF1A deficiency promotes PDAC. They also connect the tumor-suppressive role of KDM6A deficiency with a cell-specific molecular mechanism that underlies PDAC subtype definition.

Postnatal leptin surge is critical for the transient induction of the developmental beige adipocytes in mice

Beige adipocytes have become a promising therapeutic target to combat obesity. Our senior author Dr. B. Xue previously discovered a transient but significant induction of beige adipocytes in mice during early postnatal development, which peaked at postnatal day (P) 20 and then disappeared thereafter. However, the physiological mechanism underlying the transient induction of the developmental beige cells remains mystery. Interestingly, there exists a postnatal surge of leptin in mice at P10 before the appearance of the developmental beige adipocytes. Given the neurotropic effect of leptin during neuronal development and its role in activating the sympathetic nervous system (SNS), we tested the hypothesis that postnatal leptin surge is required for the transient induction of developmental beige adipocytes through sympathetic innervation. Unlike wild-type (WT) mice that were able to acquire the developmentally induced beige adipocytes at P20, ob/ob mice had much less uncoupling protein 1 (UCP1)-positive multilocular cells in inguinal white adipose tissue at the same age. This was consistent with reduced expression of UCP1 mRNA and protein levels in white fat of ob/ob mice. In contrast, daily injection of ob/ob mice with leptin between P8 and P16, mimicking the postnatal leptin surge, largely rescued the ability of these mice to acquire the developmentally induced beige adipocytes at P20, which was associated with enhanced sympathetic nerve innervation assessed by whole mount adipose tissue immunostaining of tyrosine hydroxylase. Our data demonstrate that the postnatal leptin surge is essential for the developmentally induced beige adipocyte formation in mice, possibly through increasing sympathetic nerve innervation.

Epigenetic dynamics of the thermogenic gene program of adipocytes

Brown adipose tissue (BAT) is a metabolically beneficial organ capable of burning fat by dissipating chemical energy into heat, thereby increasing energy expenditure. Moreover, subcutaneous white adipose tissue can undergo so-called browning/beiging. The recent recognition of the presence of brown or beige adipocytes in human adults has attracted much attention to elucidate the molecular mechanism underlying the thermogenic adipose program. Many key transcriptional regulators critical for the thermogenic gene program centering on activating the UCP1 promoter, have been discovered. Thermogenic gene expression in brown adipocytes rely on co-ordinated actions of a multitude of transcription factors, including EBF2, PPARγ, Zfp516 and Zc3h10. These transcription factors probably integrate into a cohesive network for BAT gene program. Moreover, these transcription factors recruit epigenetic factors, such as LSD1 and MLL3/4, for specific histone signatures to establish the favorable chromatin landscape. In this review, we discuss advances made in understanding the molecular mechanism underlying the thermogenic gene program, particularly epigenetic regulation.

Stat5a promotes brown adipocyte differentiation and thermogenic program through binding and transactivating the Kdm6a promoter

Previous studies reported that Stat5 promotes adipogenesis and white adipocyte differentiation. However, the role of Stat5 in brown adipocyte development is poorly understood. We found Stat5a was higher expressed in brown adipocytes than in white adipocytes, and its level was increased during the process of brown adipocyte differentiation. In addition, Stat5a expression was affected by cold stress and high-fat diet-feeding, suggesting a potential role in thermogenesis. Knockdown of Stat5a induced downregulation of brown fat specific genes (UCP1, PGC-1α, Acox-1 and Cidea), while overexpression of Stat5a did the opposite effect. What is more, bioinformatics analysis, ChIP assay and Luciferase activity assay all verified that Stat5a directly bind and transactivate Kdm6a promoter (Lysine-specific demethylase 6A). Further, we found that Stat5a overexpression promoted the expression of Kdm6a and inhibited the trimethylation of H3K27. While inhibiting of Kdm6a reversed the promoting effect of Stat5a overexpression on the expression of brown fat specific genes. Therefore, we conclude that Stat5a participated in brown adipocyte differentiation and thermogenic program through binding and transactivating the Kdm6a promoter.Abbreviations: Stat5: Signal transducers and activators of transcription 5; BAT: brown adipose tissue; WAT; white adipose tissue; eWAT: epididymal white adipose tissue; sWAT: subcutaneous white adipose tissue; SVFs: stromal vascular fractions; UCP1: Uncoupling protein 1; PGC-1α: Peroxisome proliferator-activated receptor gamma coactivator 1-alpha; Acox-1: Peroxisomal acyl-coenzyme A oxidase 1; Cidea: Cell death activator CIDE-A; ChIP: Chromatin Immunoprecipitation; HFD: High fat diet; FBS: Fetal bovine serum; siStat5a: Stat5a siRNA; siKdm6: Kdm6a siRNA; pcDNA-Stat5a: over expression of Stat5a pcDNA3.1 vector; IgG: mouse immunoglobulin G; Kdm6a: Lysine-specific demethylase 6A; H3K27me3: trimethylated H3K27.

Alternative Polyadenylation and Differential Regulation of Ucp1: Implications for Brown Adipose Tissue Thermogenesis Across Species

Brown adipose tissue (BAT) is a thermogenic organ owing to its unique expression of uncoupling protein 1 (UCP1), which is a proton channel in the inner mitochondrial membrane used to dissipate the proton gradient and uncouple the electron transport chain to generate heat instead of adenosine triphosphate. The discovery of metabolically active BAT in human adults, especially in lean people after cold exposure, has provoked the "thermogenic anti-obesity" idea to battle weight gain. Because BAT can expend energy through UCP1-mediated thermogenesis, the molecular mechanisms regulating UCP1 expression have been extensively investigated at both transcriptional and posttranscriptional levels. Of note, the 3'-untranslated region (3'-UTR) of Ucp1 mRNA is differentially processed between mice and humans that quantitatively affects UCP1 synthesis and thermogenesis. Here, we summarize the regulatory mechanisms underlying UCP1 expression, report the number of poly(A) signals identified or predicted in Ucp1 genes across species, and discuss the potential and caution in targeting UCP1 for enhancing thermogenesis and metabolic fitness.

Beige Fat Maintenance; Toward a Sustained Metabolic Health

Understanding the mammalian energy balance can pave the way for future therapeutics that enhance energy expenditure as an anti-obesity and anti-diabetic strategy. Several studies showed that brown adipose tissue activity increases daily energy expenditure. However, the size and activity of brown adipose tissue is reduced in individuals with obesity and type two diabetes. Humans have an abundance of functionally similar beige adipocytes that have the potential to contribute to increased energy expenditure. This makes beige adipocytes a promising target for metabolic disease therapies. While brown adipocytes tend to be stable, beige adipocytes have a high level of plasticity that allows for the rapid and dynamic induction of thermogenesis by external stimuli such as low environmental temperatures. This means that after browning stimuli have been withdrawn beige adipocytes quickly transition back to their white adipose state. The detailed molecular mechanisms regulating beige adipocytes development, function, and reversibility are not fully understood. The goal of this review is to give a comprehensive overview of beige fat development and origins, along with the transcriptional and epigenetic programs that lead to beige fat formation, and subsequent thermogenesis in humans. An improved understanding of the molecular pathways of beige adipocyte plasticity will enable us to selectively manipulate beige cells to induce and maintain their thermogenic output thus improving the whole-body energy homeostasis.

The Beige Adipocyte as a Therapy for Metabolic Diseases

Adipose tissue is traditionally categorized into white and brown relating to their function and morphology. The classical white adipose tissue builds up energy in the form of triglycerides and is useful for preventing fatigue during periods of low caloric intake and the brown adipose tissue more energetically active, with a greater number of mitochondria and energy production in the form of heat. Since adult humans possess significant amounts of active brown fat depots and its mass inversely correlates with adiposity, brown fat might play an important role in human obesity and energy homeostasis. New evidence suggests two types of thermogenic adipocytes with distinct developmental and anatomical features: classical brown adipocytes and beige adipocytes. Beige adipocyte has recently attracted special interest because of its ability to dissipate energy and the possible ability to differentiate themselves from white adipocytes. The presence of brown and beige adipocyte in human adults has acquired attention as a possible therapeutic intervention for metabolic diseases. Importantly, adult human brown appears to be mainly composed of beige-like adipocytes, making this cell type an attractive therapeutic target for obesity and obesity-related diseases, such as atherosclerosis, arterial hypertension and diabetes mellitus type 2. Because many epigenetics changes can affect beige adipocyte differentiation from adipose progenitor cells, the knowledge of the circumstances that affect the development of beige adipocyte cells may be important to new pathways in the treatment of metabolic diseases. New molecules have emerged as possible therapeutic targets, which through the impulse to develop beige adipocytes can be useful for clinical studies. In this review will discuss some recent observations arising from the unique physiological capacity of these cells and their possible role as ways to treat obesity and diabetes mellitus type 2.

Mstn knockdown decreases the trans-differentiation from myocytes to adipocytes by reducing Jmjd3 expression via the SMAD2/SMAD3 complex

Myostatin (Mstn) is an important growth/differentiation factor, and knockdown of Mstn reduces fat content. Here, we knocked down Mstn expression in C2C12 myoblasts and then induced adipogenic trans-differentiation in the cells. The effects of Mstn knockdown on lipid droplet contents and H3K27me3 marker expression on adipocyte-specific genes were detected. The results showed that Mstn knockdown reduced the formation of lipid droplets, downregulated the expression of adipocyte-specific genes, and increased H3K27me3 marker expression on adipocyte-specific genes. Chromatin immunoprecipitation analysis showed that the SMAD2/SMAD3 complex could combine with the Jumonji D3 (Jmjd3) promoter and that Mstn regulated Jmjd3 expression through this process. Jmjd3 overexpression removed the H3K27me3 marker and increased the expression of adipocyte-specific genes. Overall, our results showed that Mstn regulated Jmjd3 expression through SMAD2/SMAD3, thus affecting the H3K27me3 marker on adipocyte-specific genes and the trans-differentiation from myocytes to adipocytes.

Sympathetic nerve innervation is required for beigeing in white fat

It is increasingly recognized that activation of beige adipocyte thermogenesis by pharmacological or genetic approaches increases energy expenditure and alleviates obesity. Sympathetic nervous system (SNS) directly innervating brown adipose tissue (BAT) and white adipose tissue (WAT) plays a key role in promoting nonshivering thermogenesis. However, direct evidence that supports the importance of SNS innervation for beige adipocyte formation is still lacking, and the significance of beige adipocyte thermogenesis in protection of body temperature during cold challenge is not clear. Here we tested the necessity of SNS innervation into WAT for beige adipocyte formation in mice with defective brown fat thermogenesis via interscapular BAT (iBAT) SNS denervation. SNS denervation was achieved by microinjection of 6-hydroxydopamine (6-OHDA), a selective neurotoxin to SNS nerves, into iBAT, inguinal WAT (iWAT), or both. The partial chemical denervation of iBAT SNS down-regulated UCP-1 protein expression in iBAT demonstrated by immunoblotting and immunohistochemical measurements. This was associated with an up-regulation of UCP1 protein expression and enhanced formation of beige cells in iWAT of mice with iBAT SNS denervation. In contrast, the chemical denervation of iWAT SNS completely abolished the upregulated UCP-1 protein and beige cell formation in iWAT of mice with iBAT SNS denervation. Our data demonstrate that SNS innervation in WAT is required for beige cell formation during cold-induced thermogenesis. We conclude that there exists a coordinated thermoregulation for BAT and WAT thermogenesis via a functional cross talk between BAT and WAT SNS.

Epigenetic regulation of beige adipocyte fate by histone methylation

Adipose tissue harbors plasticity to adapt to environmental thermal changes. While brown adipocyte is a thermogenic cell which produces heat acutely in response to cold stimuli, beige (or brite) adipocyte is an inducible form of thermogenic adipocytes which emerges in the white adipose depots in response to chronic cold exposure. Such adaptability of adipocytes is regulated by epigenetic mechanisms. Among them, histone methylation is chemically stable and thus is an appropriate epigenetic mark for mediating cellular memory to induce and maintain the beige adipocyte characteristics. The enzymes that catalyze the methylation or demethylation of H3K27 and H3K9 regulate brown adipocyte biogenesis through their catalytic activity-dependent and -independent mechanisms. Resolving the bivalency of H3K4me3 and H3K27me3 as well as "opening" the chromatin structure by demethylation of H3K9 both mediate beige adipogenesis. In addition, it is recently reported that maintenance of beige adipocyte, beige-to-white transition, and cellular memory of prior cold exposure in beige adipocyte are also regulated by histone methylation. A further understanding of the epigenetic mechanism of beige adipocyte biogenesis would unravel the mechanism of the cellular memory of environmental stimuli and provide a novel therapeutics for the metabolic disorders such as obesity and diabetes that are influenced by environmental factors.

MBD3/NuRD loss participates with KDM6A program to promote DOCK5/8 expression and Rac GTPase activation in human acute myeloid leukemia

Cancer genome sequencing studies have focused on identifying oncogenic mutations. However, mutational profiling alone may not always help dissect underlying epigenetic dependencies in tumorigenesis. Nucleosome remodeling and deacetylase (NuRD) is an ATP-dependent chromatin remodeling complex that regulates transcriptional architecture and is involved in cell fate commitment. We demonstrate that loss of MBD3, an important NuRD scaffold, in human primary acute myeloid leukemia (AML) cells associates with leukemic NuRD. Interestingly, CHD4, an intact ATPase subunit of leukemic NuRD, coimmunoprecipitates and participates with H3K27Me3/2-demethylase KDM6A to induce expression of atypical guanine nucleotide exchange factors, dedicator of cytokinesis (DOCK) 5 and 8 (DOCK5/8), promoting Rac GTPase signaling. Mechanistically, MBD3 deficiency caused loss of histone deacytelase 1 occupancy with a corresponding increase in KDM6A, CBP, and H3K27Ac on DOCK5/8 loci, leading to derepression of gene expression. Importantly, the Cancer Genome Atlas AML cohort reveals that DOCK5/ 8 levels are correlated with MBD3 and KDM6A, and DOCK5/ 8 expression is significantly increased in patients who are MBD3 low and KDM6A high with a poor survival. In addition, pharmacological inhibition of DOCK signaling selectively attenuates AML cell survival. Because MBD3 and KDM6A have been implicated in metastasis, our results may suggest a general phenomenon in tumorigenesis. Collectively, these findings provide evidence for MBD3-deficient NuRD in leukemia pathobiology and inform a novel epistasis between NuRD and KDM6A toward maintenance of oncogenic gene expression in AML.-Biswas, M., Chatterjee, S. S., Boila, L. D., Chakraborty, S., Banerjee, D., Sengupta, A. MBD3/NuRD loss participates with KDM6A program to promote DOCK5/8 expression and Rac GTPase activation in human acute myeloid leukemia.

Transcriptional Control of Brown and Beige Fat Development and Function

Adipose tissue, once viewed as an inert organ of energy storage, is now appreciated to be a central node for the dynamic regulation of systemic metabolism. There are three general types of adipose tissue: white, brown, and brown-in-white or "beige" fat. All three types of adipose tissue communicate extensively with other organs in the body, including skin, liver, pancreas, muscle, and brain, to maintain energy homeostasis. When energy intake chronically exceeds energy expenditure, obesity and its comorbidities can develop. Thus, understanding the molecular mechanisms by which different types of adipose tissues develop and function could uncover new therapies for combating disorders of energy imbalance. In this review, the recent findings on the transcriptional and chromatin-mediated regulation of brown and beige adipose tissue activity are highlighted.

Class I and II Histone Deacetylase Inhibitors Differentially Regulate Thermogenic Gene Expression in Brown Adipocytes

Class I histone deacetylase inhibitors (HDACis) enhance whole body energy expenditure and attenuate high fat diet-induced insulin resistance. However, it is not clear whether this is exerted directly through activating brown fat thermogenesis. Here, we find that pan-HDACi TSA exerts paradoxical effects on brown fat gene expression, as it inhibits the expression of Ucp1, Pparγ and Prdm16 in brown adipocytes, while promoting the expression of other brown fat-specific genes such as Pgc1α, Pgc1β, Acox1 and Cidea. Further studies indicate that class I HDACi MS-275 significantly increases; whereas class II HDACi MC-1568 markedly reduces, the expression of Ucp1 and other brown fat-specific genes in treated brown adipocytes. ChIP assay reveals an enhanced H3 acetylation at the Pgc1α promoter in MS-275-treated brown adipocytes; whereas the effect of MC-1568 is associated with up-regulation of retinoblastoma protein (Rb) and an enhanced acetylation of H3K27 at the Rb promoter. Loss of function studies indicate that Pgc1α up-regulation largely mediates the stimulatory effect of class I HDACis on the thermogenic program, whereas up-regulation of Rb may be responsible for the inhibitory effect of class II HDACis. Thus, our data suggest that class I and II HDACis have differential effects on brown fat thermogenic gene expression.

Cancer-associated 2-oxoglutarate analogues modify histone methylation by inhibiting histone lysine demethylases

Histone lysine demethylases (KDMs) are 2-oxoglutarate-dependent dioxygenases (2-OGDDs) that regulate gene expression by altering chromatin structure. Their dysregulation has been associated with many cancers. We set out to study the catalytic and inhibitory properties of human KDM4A, KDM4B, KDM5B, KDM6A and KDM6B, aiming in particular to reveal which of these enzymes are targeted by cancer-associated 2-oxoglutarate (2-OG) analogues. We used affinity-purified insect cell-produced enzymes and synthetic peptides with trimethylated lysines as substrates for the in vitro enzyme activity assays. In addition, we treated breast cancer cell lines with cell-permeable forms of 2-OG analogues and studied their effects on the global histone methylation state. Our data show that KDMs have substrate specificity. Among the enzymes studied, KDM5B had the highest affinity for the peptide substrate but the lowest affinity for the 2-OG and the Fe²⁺ cosubstrate/cofactors. R-2-hydroxyglutarate (R-2HG) was the most efficient inhibitor of KDM6A, KDM4A and KDM4B, followed by S-2HG. This finding was supported by accumulations of the histone H3K9me3 and H3K27me3 marks in cells treated with the cell-permeable forms of these compounds. KDM5B was especially resistant to inhibition by R-2HG, while citrate was the most efficient inhibitor of KDM6B. We conclude that KDM catalytic activity is susceptible to inhibition by tumorigenic 2-OG analogues and suggest that the inhibition of KDMs is involved in the disease mechanism of cancers in which these compounds accumulate, such as the isocitrate dehydrogenase mutations.

MacroH2A1.1 cooperates with EZH2 to promote adipogenesis by regulating Wnt signaling

White adipocytes play important roles in many physiological processes, including energy storage, endocrine signaling, and inflammatory responses. Understanding the molecular mechanisms of adipocyte formation (adipogenesis) provides insights into therapeutic approaches against obesity and its related diseases. Many transcriptional factors and epigenetic enzymes are known to regulate adipogenesis; however, whether histone variants play a role in this process is unknown. Here we found that macroH2A1.1 (mH2A1.1), a variant of histone H2A, was upregulated during adipocyte differentiation in 3T3-L1 cells and in the white adipose tissue of obese mice. Ablation of mH2A1.1 activated Wnt/β-catenin signaling pathway, while overexpression of mH2A1.1 showed opposite effects. We further found that mH2A1.1 regulated Wnt/β-catenin signaling pathway by cooperating with EZH2, a histone H3K27 methyltransferase, thus led to accumulation of H3K27me2 and H3K27me3 on the promoters of Wnt genes. Mutations in the macro-domain, mH2A1.1G224E, and mH2A1.1G314E, not only impaired adipogenesis, but also impaired the binding ability of mH2A1.1 to EZH2 and the enrichments of H3K27me2 and H3K27me3 on the promoters of Wnt genes. Together, our study reveals a novel regulatory role of mH2A1.1 in adipogenesis and obesity, which provides new insights in white fat development.

Genetic and epigenetic control of adipose development

White adipose tissue (WAT) is the primary energy storage organ and its excess contributes to obesity, while brown adipose tissue (BAT) and inducible thermogenic (beige/brite) adipocytes in WAT dissipate energy via Ucp1 to maintain body temperature. BAT and subcutaneous WAT develop perinatally while visceral WAT forms after birth from precursors expressing distinct markers, such as Myf5, Pref-1, Wt1, and Prx1, depending on the anatomical location. In addition to the embryonic adipose precursors, a pool of endothelial cells or mural cells expressing Pparγ, Pdgfrβ, Sma and Zfp423 may become adipocytes during WAT expansion in adults. Several markers, such as Cd29, Cd34, Sca1, Cd24, Pdgfrα and Pref-1 are detected in adult WAT SVF cells that can be differentiated into adipocytes. However, potential heterogeneity and differences in developmental stage of these cells are not clear. Beige cells form in a depot- and condition-specific manner by de novo differentiation of precursors or by transdifferentiation. Thermogenic gene activation in brown and beige adipocytes relies on common transcriptional machinery that includes Prdm16, Zfp516, Pgc1α and Ebf2. Moreover, through changing the chromatin landscape, histone methyltransferases, such as Mll3/4 and Ehmt1, as well as demethylases, such as Lsd1, play an important role in regulating the thermogenic gene program. With the presence of BAT and beige/brite cells in human adults, increasing thermogenic activity of BAT and BAT-like tissues may help promote energy expenditure to combat obesity.

Shifts in podocyte histone H3K27me3 regulate mouse and human glomerular disease

Histone protein modifications control fate determination during normal development and dedifferentiation during disease. Here, we set out to determine the extent to which dynamic changes to histones affect the differentiated phenotype of ordinarily quiescent adult glomerular podocytes. To do this, we examined the consequences of shifting the balance of the repressive histone H3 lysine 27 trimethylation (H3K27me3) mark in podocytes. Adriamycin nephrotoxicity and subtotal nephrectomy (SNx) studies indicated that deletion of the histone methylating enzyme EZH2 from podocytes decreased H3K27me3 levels and sensitized mice to glomerular disease. H3K27me3 was enriched at the promoter region of the Notch ligand Jag1 in podocytes, and derepression of Jag1 by EZH2 inhibition or knockdown facilitated podocyte dedifferentiation. Conversely, inhibition of the Jumonji C domain-containing demethylases Jmjd3 and UTX increased the H3K27me3 content of podocytes and attenuated glomerular disease in adriamycin nephrotoxicity, SNx, and diabetes. Podocytes in glomeruli from humans with focal segmental glomerulosclerosis or diabetic nephropathy exhibited diminished H3K27me3 and heightened UTX content. Analogous to human disease, inhibition of Jmjd3 and UTX abated nephropathy progression in mice with established glomerular injury and reduced H3K27me3 levels. Together, these findings indicate that ostensibly stable chromatin modifications can be dynamically regulated in quiescent cells and that epigenetic reprogramming can improve outcomes in glomerular disease by repressing the reactivation of developmental pathways.

Brown and Beige Adipose Tissues in Health and Disease

Brown and beige adipocytes arise from distinct developmental origins. Brown adipose tissue (BAT) develops embryonically from precursors that also give to skeletal muscle. Beige fat develops postnatally and is highly inducible. Beige fat recruitment is mediated by multiple mechanisms, including de novo beige adipogenesis and white-to-brown adipocyte transdifferentiaiton. Beige precursors reside around vasculatures, and proliferate and differentiate into beige adipocytes. PDGFRα+Ebf2+ precursors are restricted to beige lineage cells, while another PDGFRα+ subset gives rise to beige adipocytes, white adipocytes, or fibrogenic cells. White adipocytes can be reprogramed and transdifferentiated into beige adipocytes. Brown and beige adipocytes display many similar properties, including multilocular lipid droplets, dense mitochondria, and expression of UCP1. UCP1-mediated thermogenesis is a hallmark of brown/beige adipocytes, albeit UCP1-independent thermogenesis also occurs. Development, maintenance, and activation of BAT/beige fat are guided by genetic and epigenetic programs. Numerous transcriptional factors and coactivators act coordinately to promote BAT/beige fat thermogenesis. Epigenetic reprograming influences expression of brown/beige adipocyte-selective genes. BAT/beige fat is regulated by neuronal, hormonal, and immune mechanisms. Hypothalamic thermal circuits define the temperature setpoint that guides BAT/beige fat activity. Metabolic hormones, paracrine/autocrine factors, and various immune cells also play a critical role in regulating BAT/beige fat functions. BAT and beige fat defend temperature homeostasis, and regulate body weight and glucose and lipid metabolism. Obesity is associated with brown/beige fat deficiency, and reactivation of brown/beige fat provides metabolic health benefits in some patients. Pharmacological activation of BAT/beige fat may hold promise for combating metabolic diseases. © 2017 American Physiological Society. Compr Physiol 7:1281-1306, 2017.

Alterations of Histone Modifications Contribute to Pregnane X Receptor-Mediated Induction of CYP3A4 by Rifampicin

CYP3A4 is one of the major drug-metabolizing enzymes in human and is responsible for the metabolism of 60% of clinically used drugs. Many drugs are able to induce the expression of CYP3A4, which usually causes drug-drug interactions and adverse drug reactions. This study aims to explore the role of histone modifications in rifampicin-induced expression of CYP3A4 in LS174T cells. We found that the induction of CYP3A4 mRNA (4- to 15-fold) by rifampicin in LS174T cells was associated with increased levels of histone H3 lysine 4 trimethylation (H3K4me3, above 1.8-fold) and H3 acetylation (above 2-fold) and a decreased level of histone H3 lysine 27 trimethylation (H3K27me3, about 50%) in the CYP3A4 promoter. Rifampicin enhanced recruitment to the CYP3A4 promoter of nuclear receptor coactivator 6 (NCOA6, above 3-fold) and histone acetyltransferase p300 (p300, above 1.6-fold). Silencing NCOA6 or p300 by short-hairpin RNAs resulted in inhibition of the CYP3A4 induction as well as altered levels of H3K4me3, H3K27me3, or H3 acetylation in the CYP3A4 promoter. Knockdown of pregnane X receptor (PXR) expression not only suppressed the recruitment of NCOA6 and p300 but also abolished the changes caused by rifampicin in H3K4me3, H3K27me3, and H3 acetylation levels in the CYP3A4 promoter. Moreover, rifampicin treatment enhanced the nuclear accumulation and interactions between PXR and NCOA6/p300. In conclusion, we show that the alterations of histone modifications contribute to the PXR-mediated induction of CYP3A4 by rifampicin.