Histone methyltransferase G9a modulates hepatic insulin signaling via regulating HMGA1

Large scale serum proteomics identifies proteins associated with performance decline and clinical milestones in Duchenne muscular dystrophy

Serum biomarkers are promising minimally invasive outcome measures in clinical studies in Duchenne muscular dystrophy (DMD). However, biomarkers strongly associated with clinical progression and predicting performance decline are lacking. In this study we aimed to identify serum biomarkers associated with clinical performance and able to predict clinical milestones in DMD. Towards this aim we present a retrospective multi-center cohort study including serum samples and clinical data collected in research participants with DMD as part of a natural history study at the University of Florida (UF) and real-world observations at Leiden University Medical Center (LUMC) between 2009-2022. The 7K SomaScan® assay was used to analyse protein levels in in individual serum samples. Serum biomarkers predicted age at loss of ambulation (LoA), age at loss of overhead reach (OHR) and age at loss of hand to mouth function (HTM). Secondary outcomes were the association of biomarkers with age, corticosteroid (CS) usage, and clinical performance based on the North Star Ambulatory Assessment (NSAA), 10 meter run velocity (10mrv), 6 minute walk (6MWT) and Performance of the Upper Limb (PUL2.0). A total of 716 serum samples were collected in 79 participants at UF and 74 at LUMC (mean[SD] age; 10.9[3.2] vs 8.4[3.4]). 244 serum proteins showed an association with CS usage in both cohorts independent of CS type and regimen, including MMP3 and IGLL1. 318 probes (corresponding to 294 proteins) showed significant associations with NSAA, 10mrv, 6MWT and/or PUL2.0 across both cohorts. The expression of 38 probes corresponding to 36 proteins such as RGMA, EHMT2, ART3, ANTXR2 and DLK1 was associated with risk of both lower and upper limb clinical milestones in both the LUMC and UF cohort. In conclusion, multiple biomarkers were associated with CS use, motor function and upper lower and upper limb disease milestones in DMD. These biomarkers were validated across two independent cohorts, increasing their likelihood of translation for use within the broader DMD population.

Unraveling the relationship between histone methylation and nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) poses a significant health challenge in modern societies due to shifts in lifestyle and dietary habits. Its complexity stems from genetic predisposition, environmental influences, and metabolic factors. Epigenetic processes govern various cellular functions such as transcription, chromatin structure, and cell division. In NAFLD, these epigenetic tendencies, especially the process of histone methylation, are intricately intertwined with fat accumulation in the liver. Histone methylation is regulated by different enzymes like methyltransferases and demethylases and influences the expression of genes related to adipogenesis. While early-stage NAFLD is reversible, its progression to severe stages becomes almost irreversible. Therefore, early detection and intervention in NAFLD are crucial, and understanding the precise role of histone methylation in the early stages of NAFLD could be vital in halting or potentially reversing the progression of this disease.

Post-translational modifications in diabetic cardiomyopathy

The increasing attention towards diabetic cardiomyopathy as a distinctive complication of diabetes mellitus has highlighted the need for standardized diagnostic criteria and targeted treatment approaches in clinical practice. Ongoing research is gradually unravelling the pathogenesis of diabetic cardiomyopathy, with a particular emphasis on investigating various post-translational modifications. These modifications dynamically regulate protein function in response to changes in the internal and external environment, and their disturbance of homeostasis holds significant relevance for the development of chronic ailments. This review provides a comprehensive overview of the common post-translational modifications involved in the initiation and progression of diabetic cardiomyopathy, including O-GlcNAcylation, phosphorylation, methylation, acetylation and ubiquitination. Additionally, the review discusses drug development strategies for targeting key post-translational modification targets, such as agonists, inhibitors and PROTAC (proteolysis targeting chimaera) technology that targets E3 ubiquitin ligases.

Phase Separation of Chromatin Structure-related Biomolecules: A Driving Force for Epigenetic Regulations

Intracellularly, membrane-less organelles are formed by spontaneous fusion and fission of macro-molecules in a process called phase separation, which plays an essential role in cellular activities. In certain disease states, such as cancers and neurodegenerative diseases, aberrant phase separations take place and participate in disease progression. Chromatin structure-related proteins, based on their characteristics and upon external stimuli, phase separate to exert functions like genome assembly, transcription regulation, and signal transduction. Moreover, many chromatin structure-related proteins, such as histones, histone-modifying enzymes, DNA-modifying enzymes, and DNA methylation binding proteins, are involved in epigenetic regulations through phase separation. This review introduces phase separation and how phase separation affects epigenetics with a focus on chromatin structure-related molecules.

Removal of epigenetic repressive mark on inflammatory genes in fat liver

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. The detailed epigenomic changes during fat accumulation in liver are not clear yet. Here, we performed ChIP-Seq analysis in the liver tissues of high-fat diet and regular chow diet mice and investigated the dynamic landscapes of H3K27ac and H3K9me3 marks on chromatin. We find that the activated typical enhancers marked with H3K27ac are enriched on lipid metabolic pathways in fat liver; however, super enhancers do not change much. The regions covered with H3K9me3 repressive mark seem to undergo great changes, and its peak number and intensity both decrease in fat liver. The enhancers located in lost H3K9me3 regions are enriched in lipid metabolism and inflammatory pathways; and motif analysis shows that they are potential targets for transcription factors involved in metabolic and inflammatory processes. Our study has revealed that H3K9me3 may play an important role during the pathogenesis of NAFLD through regulating the accessibility of enhancers.

Loss of renal tubular G9a benefits acute kidney injury by lowering focal lipid accumulation via CES1

Surgery-induced renal ischemia and reperfusion (I/R) injury and nephrotoxic drugs like cisplatin can cause acute kidney injury (AKI), for which there is no effective therapy. Lipid accumulation is evident following AKI in renal tubules although the mechanisms and pathological effects are unclear. Here, we report that Ehmt2-encoded histone methyltransferase G9a is upregulated in patients and mouse kidneys after AKI. Renal tubular specific knockout of G9a (Ehmt2Ksp ) or pharmacological inhibition of G9a alleviates lipid accumulation associated with AKI. Mechanistically, G9a suppresses transcription of the lipolytic enzyme Ces1; moreover, G9a and farnesoid X receptor (FXR) competitively bind to the same promoter regions of Ces1. Ces1 is consistently observed to be downregulated in the kidney of AKI patients. Pharmacological inhibition of Ces1 increases lipid accumulation, exacerbates renal I/R-injury and eliminates the beneficial effects on AKI observed in Ehmt2Ksp mice. Furthermore, lipid-lowering atorvastatin and an FXR agonist alleviate AKI by activating Ces1 and reducing renal lipid accumulation. Together, our results reveal a G9a/FXR-Ces1 axis that affects the AKI outcome via regulating renal lipid accumulation.

Transcriptional coactivation by EHMT2 restricts glucocorticoid-induced insulin resistance in a study with male mice

The classical dogma of glucocorticoid-induced insulin resistance is that it is caused by the transcriptional activation of hepatic gluconeogenic and insulin resistance genes by the glucocorticoid receptor (GR). Here, we find that glucocorticoids also stimulate the expression of insulin-sensitizing genes, such as Irs2. The transcriptional coregulator EHMT2 can serve as a transcriptional coactivator or a corepressor. Using male mice that have a defective EHMT2 coactivation function specifically, we show that glucocorticoid-induced Irs2 transcription is dependent on liver EHMT2's coactivation function and that IRS2 play a key role in mediating the limitation of glucocorticoid-induced insulin resistance by EHMT2's coactivation. Overall, we propose a model in which glucocorticoid-regulated insulin sensitivity is determined by the balance between glucocorticoid-modulated insulin resistance and insulin sensitizing genes, in which EHMT2 coactivation is specifically involved in the latter process.

TNFα Effects on Adipocytes Are Influenced by the Presence of Lysine Methyltransferases, G9a (EHMT2) and GLP (EHMT1)

Impaired adipocyte function contributes to systemic metabolic dysregulation, and altered fat mass or function increases the risk of Type 2 diabetes. EHMTs 1 and 2 (euchromatic histone lysine methyltransferases 1 and 2), also known as the G9a-like protein (GLP) and G9a, respectively, catalyze the mono- and di-methylation of histone 3 lysine 9 (H3K9) and also methylate nonhistone substrates; in addition, they can act as transcriptional coactivators independent of their methyltransferase activity. These enzymes are known to contribute to adipocyte development and function, and in vivo data indicate a role for G9a and GLP in metabolic disease states; however, the mechanisms involved in the cell-autonomous functions of G9a and GLP in adipocytes are largely unknown. Tumor necrosis factor alpha (TNFα) is a proinflammatory cytokine typically induced in adipose tissue in conditions of insulin resistance and Type 2 diabetes. Using an siRNA approach, we have determined that the loss of G9a and GLP enhances TNFα-induced lipolysis and inflammatory gene expression in adipocytes. Furthermore, we show that G9a and GLP are present in a protein complex with nuclear factor kappa B (NF-κB) in TNFα-treated adipocytes. These novel observations provide mechanistic insights into the association between adipocyte G9a and GLP expression and systemic metabolic health.

Epigenetics of methylation modifications in diabetic cardiomyopathy

Type 2 diabetes is one of the most common metabolic diseases with complications including diabetic cardiomyopathy and atherosclerotic cardiovascular disease. Recently, a growing body of research has revealed that the complex interplay between epigenetic changes and the environmental factors may significantly contribute to the pathogenesis of cardiovascular complications secondary to diabetes. Methylation modifications, including DNA methylation and histone methylation among others, are important in developing diabetic cardiomyopathy. Here we summarized the literatures of studies focusing on the role of DNA methylation, and histone modifications in microvascular complications of diabetes and discussed the mechanism underlying these disorders, to provide the guidance for future research toward an integrated pathophysiology and novel therapeutic strategies to treat or prevent this frequent pathological condition.

Targeting epigenetics in diabetic cardiomyopathy: Therapeutic potential of flavonoids

The pathophysiological mechanisms of diabetic cardiomyopathy have been extensively studied, but there is still a lack of effective prevention and treatment methods. The ability of flavonoids to protect the heart from diabetic cardiomyopathy has been extensively described. In recent years, epigenetics has received increasing attention from scholars in exploring the etiology and treatment of diabetes and its complications. DNA methylation, histone modifications and non-coding RNAs play key functions in the development, maintenance and progression of diabetic cardiomyopathy. Hence, prevention or reversal of the epigenetic alterations that have occurred during the development of diabetic cardiomyopathy may alleviate the personal and social burden of the disease. Flavonoids can be used as natural epigenetic modulators in alternative therapies for diabetic cardiomyopathy. In this review, we discuss the epigenetic effects of different flavonoid subtypes in diabetic cardiomyopathy and summarize the evidence from preclinical and clinical studies that already exist. However, limited research is available on the potential beneficial effects of flavonoids on the epigenetics of diabetic cardiomyopathy. In the future, clinical trials in which different flavonoids exert their antidiabetic and cardioprotective effects through various epigenetic mechanisms should be further explored.

DNA and histone modifications as potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine

Lung cancer has a very high mortality in females and males. Most (~ 85%) of lung cancers are non-small cell lung cancers (NSCLC). When lung cancer is diagnosed, most of them have either local or distant metastasis, with a poor prognosis. In order to achieve better outcomes, it is imperative to identify the molecular signature based on genetic and epigenetic variations for different NSCLC subgroups. We hypothesize that DNA and histone modifications play significant roles in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine). Epigenetics has a significant impact on tumorigenicity, tumor heterogeneity, and tumor resistance to chemotherapy, targeted therapy, and immunotherapy. An increasing interest is that epigenomic regulation is recognized as a potential treatment option for NSCLC. Most attention has been paid to the epigenetic alteration patterns of DNA and histones. This article aims to review the roles DNA and histone modifications play in tumorigenesis, early detection and diagnosis, and advancements and therapies of NSCLC, and also explore the connection between DNA and histone modifications and PPPM, which may provide an important contribution to improve the prognosis of NSCLC. We found that the success of targeting DNA and histone modifications is limited in the clinic, and how to combine the therapies to improve patient outcomes is necessary in further studies, especially for predictive diagnostics, targeted prevention, and personalization of medical services in the 3P medicine approach. It is concluded that DNA and histone modifications are potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine.

MicroRNA-205-5p plays a suppressive role in the high-fat diet-induced atrial fibrosis through regulation of the EHMT2/IGFBP3 axis

Objective

MicroRNAs (miRNAs) targeting has been revealed to be an appealing strategy for the treatment and management of atrial fibrillation (AF). In this research, we aimed to explore the mechanisms of miR-205-5p in reducing the high-fat diet (HFD)-induced atrial fibrosis through the EHMT2/IGFBP3 axis.

Methods

Expression levels of miR-205-5p, IGFBP3 and EHMT2 were determined in AF patients, cell fibrosis models and mouse atrial fibrosis models. Luciferase activity and RIP assays were performed to detect the binding between miR-205-5p and EHMT2, and ChIP assays were implemented to detect the enrichment of H3K9me2 and H3K4me3 in the promoter region of IGFBP3 in cells. The related experiments focusing on the inflammatory response, atrial fibrosis, mitochondrial damage, and metabolic abnormalities were performed to figure out the roles of miR-205-5p, IGFBP3, and EHMT2 in cell and mouse atrial fibrosis models.

Results

Low expression levels of miR-205-5p and IGFBP3 and a high expression of EHMT2 were found in AF patients, cell fibrosis models and mouse atrial fibrosis models. Upregulation of miR-205-5p reduced the expression of TGF-β1, α-SMA, Col III and other fibrosis-related proteins. miR-205-5p overexpression targeted EHMT2 to regulate the methylation of H3 histones to promote IGFBP3 expression, which in turn affected the fibrosis of atrial muscle cells. In HFD-induced atrial fibrosis mice, upregulated miR-205-5p or elevated IGFBP3 alleviated atrial fibrosis, mitochondrial damage, and metabolic abnormalities.

Conclusion

This study suggests that miR-205-5p attenuates HFD-induced atrial fibrosis via modulating the EHMT2/IGFBP3 axis.

Graphical Abstract

miR-205-5p alleviates high-fat diet-induced atrial fibrosis in mice via EHMT2/IGFBP3.

Epigenetics alternation in lung fibrosis and lung cancer

Respiratory disease including interstitial lung diseases (ILDs) and lung cancer is a group of devastating diseases that linked with increased morbidity and healthcare burden. However, respiratory diseases cannot be fully explained by the alternation of genetic information. Genetic studies described that epigenetic mechanisms also participate to transmit genetic information. Recently, many studies demonstrated the role of altered epigenetic modification in the pathogenesis of lung cancer and pulmonary fibrosis. Due to lacking effective medication, the underlying pathophysiological processes and causal relationships of lung diseases with epigenetic mechanisms still need to be better understood. Our present review provided a systematic revision of current knowledge concerning diverse epigenetic aberrations in major lung diseases, with special emphasis on DNA methylation, histone modifications, lncRNAs profiles, telomere patterns, as well as chromatin-remodelling complexes. We believed that a new target therapy for lung disease based on findings of the involved epigenetic pathway is a promising future direction.

Epigenetics and Beyond: Targeting Histone Methylation to Treat Type 2 Diabetes Mellitus

Diabetes mellitus is a global public health challenge with high morbidity. Type 2 diabetes mellitus (T2DM) accounts for 90% of the global prevalence of diabetes. T2DM is featured by a combination of defective insulin secretion by pancreatic β-cells and the inability of insulin-sensitive tissues to respond appropriately to insulin. However, the pathogenesis of this disease is complicated by genetic and environmental factors, which needs further study. Numerous studies have demonstrated an epigenetic influence on the course of this disease via altering the expression of downstream diabetes-related proteins. Further studies in the field of epigenetics can help to elucidate the mechanisms and identify appropriate treatments. Histone methylation is defined as a common histone mark by adding a methyl group (-CH3) onto a lysine or arginine residue, which can alter the expression of downstream proteins and affect cellular processes. Thus, in tthis study will discuss types and functions of histone methylation and its role in T2DM wilsed. We will review the involvement of histone methyltransferases and histone demethylases in the progression of T2DM and analyze epigenetic-based therapies. We will also discuss the potential application of histone methylation modification as targets for the treatment of T2DM.

Gene cascade analysis in human granulosa tumor cells (KGN) following exposure to high levels of free fatty acids and insulin

Maternal metabolic disorders such as obesity and diabetes are detrimental factors that compromise fertility and the success rates of medically assisted procreation procedures. During metabolic stress, adipose tissue is more likely to release free fatty acids (FFA) in the serum resulting in an increase of FFA levels not only in blood, but also in follicular fluid (FF). In humans, high concentrations of palmitic acid and stearic acid reduced granulosa cell survival and were associated with poor cumulus-oocyte complex (COC) morphology. Obesity and high levels of circulating FFA were also causatively linked to hampered insulin sensitivity in cells and compensatory hyperinsulinemia. To provide a global picture of the principal upstream signaling pathways and genomic mechanisms involved in this metabolic context, human granulosa-like tumor cells (KGN) were treated with a combination of palmitic acid, oleic acid, and stearic acid at the higher physiological concentrations found in the follicular fluid of women with a higher body mass index (BMI) (≥ 30.0 kg/m2). We also tested a high concentration of insulin alone and in combination with high concentrations of fatty acids. Transcription analysis by RNA-seq with a cut off for fold change of 1.5 and p-value 0.05 resulted in thousands of differentially expressed genes for each treatment. Using analysis software such as Ingenuity Pathway Analysis (IPA), we were able to establish that high concentrations of FFA affected the expression of genes mainly related to glucose and insulin homoeostasis, fatty acid metabolism, as well as steroidogenesis and granulosa cell differentiation processes. The combination of insulin and high concentrations of FFA affected signaling pathways related to apoptosis, inflammation, and oxidative stress. Taken together, our results provided new information on the mechanisms that might be involved in human granulosa cells exposed to high concentrations of FFA and insulin in the contexts of metabolism disorders.

Epigenetics of Hepatic Insulin Resistance

Insulin resistance (IR) is largely recognized as a unifying feature that underlies metabolic dysfunction. Both lifestyle and genetic factors contribute to IR. Work from recent years has demonstrated that the epigenome may constitute an interface where different signals may converge to promote IR gene expression programs. Here, we review the current knowledge of the role of epigenetics in hepatic IR, focusing on the roles of DNA methylation and histone post-translational modifications. We discuss the broad epigenetic changes observed in the insulin resistant liver and its associated pathophysiological states and leverage on the wealth of 'omics' studies performed to discuss efforts in pinpointing specific loci that are disrupted by these changes. We envision that future studies, with increased genomic resolution and larger cohorts, will further the identification of biomarkers of early onset hepatic IR and assist the development of targeted interventions. Furthermore, there is growing evidence to suggest that persistent epigenetic marks may be acquired over prolonged exposure to disease or deleterious exposures, highlighting the need for preventative medicine and long-term lifestyle adjustments to avoid irreversible or long-term alterations in gene expression.

Muscular G9a Regulates Muscle-Liver-Fat Axis by Musclin Under Overnutrition in Female Mice

Cross talk among different tissues and organs is a hotspot in metabolic research. Recent studies have revealed the regulatory roles of a number of myokines in metabolism. Here, we report that female mice lacking muscle-specific histone methylase G9a (Ehmt2 ^Ckmm knockout [KO] or Ehmt2 ^HSA KO) are resistant to high-fat diet (HFD)-induced obesity and hepatic steatosis. Furthermore, we identified a significantly upregulated circulating level of musclin, a myokine, in HFD-fed Ehmt2 ^Ckmm KO or Ehmt2 ^HSA KO female mice. Similarly, upregulated musclin was observed in mice injected with two structurally different inhibitors for G9a methylase activity: BIX01294 and A366. Moreover, injection of recombinant full-length musclin or its functional core domain inhibited the HFD-induced obesity and hepatic steatosis in wild-type female and male mice. Mechanistically, G9a methylase activity-dependently regulated muscular musclin level by binding to its promoter, also by regulating phosphorylated-FOXO1/FOXO1 levels in vivo and in vitro. Collectively, these data suggest a critical role for G9a in the muscle-liver-fat metabolic axis, at least for female mice. Musclin may serve as a potential therapeutic candidate for obesity and associated diseases.

Radiation-induced H3K9 methylation on E-cadherin promoter mediated by ROS/Snail axis : Role of G9a signaling during lung epithelial-mesenchymal transition

Lung cancer patients who have undergone radiotherapy developed severe complications such as pneumonitis and fibrosis. Upon irradiation, epithelial cells acquire mesenchymal phenotype via a process called epithelial to mesenchymal transition (EMT), which plays a vital role in organ fibrosis. Several mechanisms have been studied on EMT, however, the correlation between radiation-induced EMT and epigenetic changes are not well known. In the present study, we investigated the role of histone methyltransferase G9a on radiation-induced EMT signaling. There was an increase in total global histone methylation level in irradiated epithelial cells. Western blot analysis on irradiated cells showed an increased expression of H3K9me2/3. The pre-treatment of G9a inhibitor enhanced E-cadherin expression and decreased the mesenchymal markers like N-cadherin, vimentin in the radiated group. Surprisingly, radiation-induced ROS generation and pERK1/2 levels were also inhibited by G9a inhibitor BIX01294, which is showing its antioxidant potential. The ChIP-qPCR analysis on the E-cadherin promoter suggested that G9a and Snail might have formed complex to enrich suppressive marker H3K9me2/3. On the whole, our present study suggested that 1] ROS could modify H3K9 methylation via G9a and promote radiation-induced lung EMT in Beas2B and A549 cells 2] E-cadherin promoter enrichment with heterochromatin mark H3K9me2 expression upon irradiation could be modified by regulating G9a methyltransferase.

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.

Multigenerational maternal obesity increases the incidence of HCC in offspring via miR-27a-3p

BACKGROUND & AIMS

Obesity is an independent risk factor for malignancies, including hepatocellular carcinoma (HCC). However, it remains unknown whether maternal obesity affects the incidence of HCC in offspring. Thus, we aimed to investigate this association and its underlying mechanisms.

METHODS

Diethylnitrosamine (DEN) was used to induce HCC in a high-fat diet (HFD)-induced multigenerational obesity model. RNA-sequencing was performed to identify the genes and microRNAs (miRNAs) that were altered over generations. The role of the miR-27a-3p-Acsl1/Aldh2 axis in HCC was evaluated in cell lines and HCC-bearing nude mice, and its intergenerational impact was studied in pregnant mice and their offspring.

RESULTS

Under HFD stress, maternal obesity caused susceptibility of offspring to DEN-induced HCC, and such susceptibility was cumulative over generations. We identified that Acsl1 and Aldh2, direct targets of miR-27a-3p, were gradually changed over generations. Under hyperlipidemic conditions, downregulation of Acsl1 and Aldh2 increased cell proliferation (in vitro) or tumor growth (in vivo) in synergy. Intratumor injection of an miR-27a-3p agomir exacerbated tumor growth by downregulating Acsl1 and Aldh2; while intratumor injection of an miR-27a-3p antagomir had the opposite effect. Moreover, serum miR-27a-3p levels gradually increased in the HFD-fed maternal lineage over generations. Injecting pregnant mice with an miR-27a-3p agomir not only upregulated hepatic miR-27a-3p and downregulated Acsl1/Aldh2 in offspring (fetus, young and adult stages), but also exacerbated HCC development in DEN-treated offspring. In human HCC, upregulated miR-27a-3p and downregulated Acsl1/Aldh2 were negatively correlated with survival on TCGA analysis; while, hepatic miR-27a-3p was negatively correlated with Acsl1/Aldh2 expression in tumor/non-tumor tissues from fatty/non-fatty livers.

CONCLUSIONS

Maternal obesity plays a role in regulating cumulative susceptibility to HCC development in offspring over multiple generations through the miR-27a-3p-Acsl1/Aldh2 axis.

LAY SUMMARY

It is not currently known how maternal obesity affects the incidence of liver cancer in offspring. In this study, we identified a microRNA (miR-27a-3p) that was upregulated in obese mothers and could be passed on to their offspring. This microRNA enhanced the risk of liver cancer in offspring by regulating 2 genes (Acsl1 and Aldh2). This mechanism could be a future therapeutic target.

HMGA Genes and Proteins in Development and Evolution

HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.

Fat-Specific Knockout of Mecp2 Upregulates Slpi to Reduce Obesity by Enhancing Browning

Abnormalities of methyl-CpG binding protein 2 (Mecp2) cause neurological disorders with metabolic dysfunction; however, its role in adipose tissues remains unclear. Here, we report upregulated Mecp2 in white adipose tissues (WAT) of obese humans, as well as in obese mice and during in vitro adipogenesis. Normal chow-fed adipocyte-specific Mecp2 knockout mice (Mecp2 ^Adi KO mice) showed a lean phenotype, with downregulated lipogenic genes and upregulated thermogenic genes that were identified using RNA sequencing. Consistently, the deficiency of Mecp2 in adipocytes protected mice from high-fat diet (HFD)-induced obesity and inhibited in vitro adipogenesis. Furthermore, Mecp2 ^Adi KO mice showed increased browning under different stimuli, including cold treatment. Mechanistically, Mecp2 bound to the promoter of secretory leukocyte protease inhibitor (Slpi) and negatively regulated its expression. Knockdown of Slpi in inguinal WAT of Mecp2 ^Adi KO mice prevented cold-induced browning. Moreover, recombinant SLPI treatment reduced the HFD-induced obesity via enhancing browning. Together, our results suggest a novel non-central nervous system function of Mecp2 in obesity by suppressing browning, at least partially, through regulating adipokine Slpi.

Gene surgery: Potential applications for human diseases

Gene therapy became in last decade a new emerging therapeutic era showing promising results against different diseases such as cancer, cardiovascular diseases, diabetes, and neurological disorders. Recently, the genome editing technique for eukaryotic cells called CRISPR-Cas (Clustered Regulatory Interspaced Short Palindromic Repeats) has enriched the field of gene surgery with enhanced applications. In the present review, we summarized the different applications of gene surgery for treating human diseases such as cancer, diabetes, nervous, and cardiovascular diseases, besides the molecular mechanisms involved in these important effects. Several studies support the important therapeutic applications of gene surgery in a large number of health disorders and diseases including β-thalassemia, cancer, immunodeficiencies, diabetes, and neurological disorders. In diabetes, gene surgery was shown to be effective in type 1 diabetes by triggering different signaling pathways. Furthermore, gene surgery, especially that using CRISPR-Cas possessed important application on diagnosis, screening and treatment of several cancers such as lung, liver, pancreatic and colorectal cancer. Nevertheless, gene surgery still presents some limitations such as the design difficulties and costs regarding ZFNs (Zinc Finger Nucleases) and TALENs (Transcription Activator-Like Effector Nucleases) use, off-target effects, low transfection efficiency, in vivo delivery-safety and ethical issues.

Liver-specific knockout of histone methyltransferase G9a impairs liver maturation and dysregulates inflammatory, cytoprotective, and drug-processing genes

Methyltransferase G9a is essential for a key gene silencing mark, histone H3 dimethylation at lysine-9 (H3K9me2). Hepatic G9a expression is down-regulated by xenobiotics and diabetes. However, little is known about the role of G9a in liver. Thus, we generated mice with liver-specific knockout (Liv-KO) of G9a. Adult G9a Liv-KO mice had marked loss of H3K9me2 proteins in liver, without overt liver injury or infiltration of inflammatory cells. However, G9a-null livers had ectopic induction of certain genes normally expressed in neural and immune systems. Additionally, G9a-null livers had moderate down-regulation of cytoprotective genes, markedly altered expression of certain important drug-processing genes, elevated endogenous reactive oxygen species, induction of ER stress marker Chop, but decreased glutathione and nuclear Nrf2. microRNA-383, a negative regulator of the PI3K/Akt pathway, was strongly induced in G9a Liv-KO mice. After LPS treatment, G9a Liv-KO mice had aggravated lipid peroxidation and proinflammatory response. Taken together, the present study demonstrates that G9a regulates liver maturation by silencing neural and proinflammatory genes but maintaining/activating cytoprotective and drug-processing genes, in which the G9a/miR-383/PI3K/Akt/Nrf2 (Chop) pathways may play important roles. G9a deficiency due to genetic polymorphism and/or environmental exposure may alter xenobiotic metabolism and aggravate inflammation and liver dysfunction.

Lung Cancer Therapy Targeting Histone Methylation: Opportunities and Challenges

Lung cancer is one of the most common malignancies. In spite of the progress made in past decades, further studies to improve current therapy for lung cancer are required. Dynamically controlled by methyltransferases and demethylases, methylation of lysine and arginine residues on histone proteins regulates chromatin organization and thereby gene transcription. Aberrant alterations of histone methylation have been demonstrated to be associated with the progress of multiple cancers including lung cancer. Inhibitors of methyltransferases and demethylases have exhibited anti-tumor activities in lung cancer, and multiple lead candidates are under clinical trials. Here, we summarize how histone methylation functions in lung cancer, highlighting most recent progresses in small molecular inhibitors for lung cancer treatment.

Transcriptional Regulation of Glucose Metabolism: The Emerging Role of the HMGA1 Chromatin Factor

HMGA1 (high mobility group A1) is a nonhistone architectural chromosomal protein that functions mainly as a dynamic regulator of chromatin structure and gene transcription. As such, HMGA1 is involved in a variety of fundamental cellular processes, including gene expression, epigenetic regulation, cell differentiation and proliferation, as well as DNA repair. In the last years, many reports have demonstrated a role of HMGA1 in the transcriptional regulation of several genes implicated in glucose homeostasis. Initially, it was proved that HMGA1 is essential for normal expression of the insulin receptor (INSR), a critical link in insulin action and glucose homeostasis. Later, it was demonstrated that HMGA1 is also a downstream nuclear target of the INSR signaling pathway, representing a novel mediator of insulin action and function at this level. Moreover, other observations have indicated the role of HMGA1 as a positive modulator of the Forkhead box protein O1 (FoxO1), a master regulatory factor for gluconeogenesis and glycogenolysis, as well as a positive regulator of the expression of insulin and of a series of circulating proteins that are involved in glucose counterregulation, such as the insulin growth factor binding protein 1 (IGFBP1), and the retinol binding protein 4 (RBP4). Thus, several lines of evidence underscore the importance of HMGA1 in the regulation of glucose production and disposal. Consistently, lack of HMGA1 causes insulin resistance and diabetes in humans and mice, while variations in the HMGA1 gene are associated with the risk of type 2 diabetes and metabolic syndrome, two highly prevalent diseases that share insulin resistance as a common pathogenetic mechanism. This review intends to give an overview about our current knowledge on the role of HMGA1 in glucose metabolism. Although research in this field is ongoing, many aspects still remain elusive. Future directions to improve our insights into the pathophysiology of glucose homeostasis may include epigenetic studies and the use of "omics" strategies. We believe that a more comprehensive understanding of HMGA1 and its networks may reveal interesting molecular links between glucose metabolism and other biological processes, such as cell proliferation and differentiation.