Histone demethylase Kdm4b functions as a co-factor of C/EBPβ to promote mitotic clonal expansion during differentiation of 3T3-L1 preadipocytes

Caveolin-2 controls preadipocyte survival in the mitotic clonal expansion for adipogenesis

Here, we report that Caveolin-2 (Cav-2) is a cell cycle regulator in the mitotic clonal expansion (MCE) for adipogenesis. For the G2/M phase transition and re-entry into the G1 phase, dephosphorylated Cav-2 by protein tyrosine phosphatase 1B (PTP1B) controlled epigenetic activation of Ccnb1, Cdk1, and p21 in a lamin A/C-dependent manner, thereby ensuring the survival of preadipocytes. Cav-2, associated with lamin A/C, recruited the repressed promoters of Ccnb1 and Cdk1 for activation, and disengaged the active promoter of p21 from lamin A/C for inactivation through histone H3 modifications at the nuclear periphery. Cav-2 deficiency abrogated the histone H3 modifications and impeded the transactivation of Ccnb1, Cdk1, and p21, leading to a delay in mitotic entry, retardation of re-entry into G1 phase, and the apoptotic cell death of preadipocytes. Re-expression of Cav-2 restored the G2/M phase transition and G1 phase re-entry, preadipocyte survival, and adipogenesis in Cav-2-deficient preadipocytes. Our study uncovers a novel mechanism by which cell cycle transition and apoptotic cell death are controlled for adipocyte hyperplasia.

Deciphering adipose development: Function, differentiation and regulation

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

Deubiquitinase USP1 enhances CCAAT/enhancer-binding protein beta (C/EBPβ) stability and accelerates adipogenesis and lipid accumulation

Dysregulation of the ubiquitin-proteasome system has been implicated in the pathogenesis of several metabolic disorders, including obesity, diabetes, and non-alcoholic fatty liver disease; however, the mechanisms controlling pathogenic metabolic disorders remain unclear. Transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) regulates adipogenic genes. The study showed that the expression level of C/EBPβ is post-translationally regulated by the deubiquitinase ubiquitin-specific protease 1 (USP1) and that USP1 expression is remarkably upregulated during adipocyte differentiation and in the adipose tissue of mice fed a high-fat diet (HFD). We found that USP1 directly interacts with C/EBPβ. Knock-down of USP1 decreased C/EBPβ protein stability and increased its ubiquitination. Overexpression of USP1 regulates its protein stability and ubiquitination, whereas catalytic mutant of USP1 had no effect on them. It suggests that USP1 directly deubiquitinases C/EBPβ and increases the protein expression, leading to adipogenesis and lipid accumulation. Notably, the USP1-specific inhibitor ML323-originally developed to sensitize cancer cells to DNA-damaging agents-decreased adipocyte differentiation and lipid accumulation in 3T3-L1 cells without cytotoxicity. Oral gavage of ML323 was administered to HFD-fed mice, which showed weight loss and improvement in insulin and glucose sensitivity. Both fat mass and adipocyte size in white adipose tissues were significantly reduced by ML323 treatment, which also reduced the expression of genes involved in adipogenesis and inflammatory responses. ML323 also reduced lipid accumulation, hepatic triglycerides, free fatty acids, and macrophage infiltration in the livers of HFD-fed mice. Taken together, we suggest that USP1 plays an important role in adipogenesis by regulating C/EBPβ ubiquitination, and USP1-specific inhibitor ML323 is a potential treatment option and further study by ML323 is needed for clinical application for metabolic disorders.

Leuconostoc Citreum Inhibits Adipogenesis and Lipogenesis by Inhibiting p38 MAPK/Erk 44/42 and Stimulating AMPKα Signaling Pathways

Probiotics provide a range of health benefits. Several studies have shown that using probiotics in obesity treatment can reduce bodyweight. However, such treatments are still restricted. Leuconostoc citreum, an epiphytic bacterium, is widely used in a variety of biological applications. However, few studies have investigated the role of Leuconostoc spp. in adipocyte differentiation and its molecular mechanisms. Therefore, the objective of this study was to determine the effects of cell-free metabolites of L. citreum (LSC) on adipogenesis, lipogenesis, and lipolysis in 3T3-L1 adipocytes. The results showed that LSC treatment reduced the accumulation of lipid droplets and expression levels of CCAAT/ enhancer-binding protein-α & β (C/EBP-α & β), peroxisome proliferator-activated receptor-γ (PPAR-γ), serum regulatory binding protein-1c (SREBP-1c), adipocyte fatty acid binding protein (aP2), fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), resistin, pp38MAPK, and pErk 44/42. However, compared to control cells, adiponectin, an insulin sensitizer, was elevated in adipocytes treated with LSC. In addition, LSC treatment increased lipolysis by increasing pAMPK-α and suppressing FAS, ACC, and PPAR-γ expression, similarly to the effects of AICAR, an AMPK agonist. In conclusion, L. citreum is a novel probiotic strain that can be used to treat obesity and its associated metabolic disorders.

Inhibitory Effect of Isopanduratin A on Adipogenesis: A Study of Possible Mechanisms

The root of Boesenbergia rotunda, a culinary plant commonly known as fingerroot, has previously been reported to possess anti-obesity activity, with four flavonoids identified as active principles, including pinostrobin, panduratin A, cardamonin, and isopanduratin A. However, the molecular mechanisms underlying the antiadipogenic potential of isopanduratin A remain unknown. In this study, isopanduratin A at non-cytotoxic concentrations (1-10 μM) significantly suppressed lipid accumulation in murine (3T3-L1) and human (PCS-210-010) adipocytes in a dose-dependent manner. Downregulation of adipogenic effectors (FAS, PLIN1, LPL, and adiponectin) and adipogenic transcription factors (SREBP-1c, PPARγ, and C/EBPα) occurred in differentiated 3T3-L1 cells treated with varying concentrations of isopanduratin A. The compound deactivated the upstream regulatory signals of AKT/GSK3β and MAPKs (ERK, JNK, and p38) but stimulated the AMPK-ACC pathway. The inhibitory trend of isopanduratin A was also observed with the proliferation of 3T3-L1 cells. The compound also paused the passage of 3T3-L1 cells by inducing cell cycle arrest at the G0/G1 phase, supported by altered levels of cyclins D1 and D3 and CDK2. Impaired p-ERK/ERK signaling might be responsible for the delay in mitotic clonal expansion. These findings revealed that isopanduratin A is a strong adipogenic suppressor with multi-target mechanisms and contributes significantly to anti-obesogenic activity. These results suggest the potential of fingerroot as a functional food for weight control and obesity prevention.

C/EBPβ Coupled with E2F2 Promoted the Proliferation of hESC-Derived Hepatocytes through Direct Binding to the Promoter Regions of Cell-Cycle-Related Genes

Human embryonic stem cells (hESCs) hold the potential to solve the problem of the shortage of functional hepatocytes in clinical applications and drug development. However, a large number of usable hepatocytes derived from hESCs cannot be effectively obtained due to the limited proliferation capacity. In this study, we found that enhancement of liver transcription factor C/EBPβ during hepatic differentiation could not only significantly promote the expression of hepatic genes, such as albumin, alpha fetoprotein, and alpha-1 antitrypsin, but also dramatically reinforce proliferation-related phenotypes, including increasing the expression of proliferative genes, such as CDC25C, CDC45L, and PCNA, and the activation of cell cycle and DNA replication pathways. In addition, the analysis of CUT&Tag sequencing further revealed that C/EBPβ is directly bound to the promoter region of proliferating genes to promote cell proliferation; this interaction between C/EBPβ and DNA sequences of the promoters was verified by luciferase assay. On the contrary, the knockdown of C/EBPβ could significantly inhibit the expression of the aforementioned proliferative genes. RNA transcriptome analysis and GSEA enrichment indicated that the E2F family was enriched, and the expression of E2F2 was changed with the overexpression or knockdown of C/EBPβ. Moreover, the results of CUT&Tag sequencing showed that C/EBPβ also directly bound the promoter of E2F2, regulating E2F2 expression. Interestingly, Co-IP analysis exhibited a direct binding between C/EBPβ and E2F2 proteins, and this interaction between these two proteins was also verified in the LO2 cell line, a hepatic progenitor cell line. Thus, our results demonstrated that C/EBPβ first initiated E2F2 expression and then coupled with E2F2 to regulate the expression of proliferative genes in hepatocytes during the differentiation of hESCs. Therefore, our findings open a new avenue to provide an in vitro efficient approach to generate proliferative hepatocytes to potentially meet the demands for use in cell-based therapeutics as well as for pharmaceutical and toxicological studies.

Elucidation of adipogenic differentiation regulatory mechanism in human maxillary/mandibular bone marrow-derived stem cells

OBJECTIVE

This study aims to investigate the underlying molecular mechanisms that regulate the adipogenic differentiation of maxillary/mandibular bone marrow-derived mesenchymal stem cells (MBMSCs).

DESIGN

MBMSCs and iliac bone marrow-derived MSCs (IBMSCs) were compared for osteogenic, chondrogenic, and adipogenic differentiation. Cell surface antigen expression was examined using flow cytometry, and stem cell marker expression was assessed using real-time polymerase chain reaction (PCR). Various adipogenic regulatory factors' expression was evaluated using real-time PCR and western blotting.

RESULTS

No significant differences in cell surface antigen profiles or stem cell marker expression in MBMSCs and IBMSCs were observed. MBMSCs and IBMSCs displayed similar osteogenic and chondrogenic potentials, whereas MBMSCs showed significantly lower adipogenic potentials than those shown by IBMSCs. Expression of CCAAT/enhancer binding protein β (C/EBPβ), C/EBPδ, early B-cell factor 1 (Ebf-1), and Krüppel-like factor 5 (KLF5), which are early adipogenic differentiation factors, was suppressed in MBMSCs compared to that in IBMSCs. Peroxisome proliferator-activated receptor-γ (PPARγ) and C/EBPα, which play important roles in the terminal differentiation of adipocytes, was lower in MBMSCs than that in IBMSCs. Furthermore, the level of zinc finger protein 423 (Zfp423), which is involved in the commitment of undifferentiated MSCs to the adipocyte lineage, was significantly lower in MBMSCs than that in IBMSCs.

CONCLUSIONS

MBMSCs are negatively regulated in the commitment of undifferentiated MSCs to the adipocyte lineage (preadipocytes) as well as in the terminal differentiation of preadipocytes into mature adipocytes. These results may elucidate the site-specific characteristics of MBMSCs.

Epigenetic regulation of Cebpb activation by pY19-Caveolin-2 at the nuclear periphery in association with the nuclear lamina

Here, we show that Caveolin-2 (Cav-2) is an epigenetic regulator for adipogenesis. Upon adipogenic stimulation, inner nuclear membrane (INM)-targeted pY19-Cav-2 interacted with lamin A/C to disengage the repressed Cebpb promoter from lamin A/C, which facilitated the Cebpb promoter association with lamin B1. Consequently, pY19-Cav-2 recruited lysine demethylase 4b (KDM4b) for demethylation of histone H3 lysine 9 trimethylation (H3K9me3) and histone acetyltransferase GCN5 for acetylation of H3K27, and subsequently RNA polymerase II (Pol II) on Cebpb promoter for epigenetic activation of Cebpb, to initiate adipogenesis. Cav-2 knock-down abrogated the Cebpb activation and blocked the Pparg2 and Cebpa activation. Re-expression of Cav-2 restored Cebpb activation and adipogenesis in Cav-2-deficient preadipocytes. Our data identify a new mechanism by which the epigenetic activation of Cebpb is controlled at the nuclear periphery to promote adipogenesis.

Krüppel-like factors family regulation of adipogenic markers genes in bovine cattle adipogenesis

Intramuscular fat (IMF) content is a crucial determinant of meat quality traits in livestock. A network of transcription factors act in concert to regulate adipocyte formation and differentiation, which in turn influences intramuscular fat. Several genes and associated transcription factors have been reported to influence lipogenesis and adipogenesis during fetal and subsequent growth stage. Specifically in cattle, Krüppel-like factors (KLFs), which represents a family of transcription factors, have been reported to be involved in adipogenic differentiation and development. KLFs are a relatively large group of zinc-finger transcription factors that have a variety of functions in addition to adipogenesis. In mammals, the participation of KLFs in cell development and differentiation is well known. Specifically in the context of adipogenesis, KLFs function either as positive (KLF4, KLF5, KLF6, KLF8, KLF9, KLF10, KLF11, KLF12, KLF13, KLF14 and KLF15) or negative organizers (KLF2, KLF3 and KLF7), by a variety of different mechanisms such as crosstalk with C/EBP and PPARγ. In this review, we aim to summarize the potential functions of KLFs in regulating adipogenesis and associated pathways in cattle. Furthermore, the function of known bovine adipogenic marker genes, and associated transcription factors that regulate the expression of these marker genes is also summarized. Overall, this review will provide an overview of marker genes known to influence bovine adipogenesis and regulation of expression of these genes, to provide insights into leveraging these genes and transcription factors to enhance breeding programs, especially in the context of IMF deposition and meat quality.

The Diverse Roles of Histone Demethylase KDM4B in Normal and Cancer Development and Progression

Histone methylation status is an important process associated with cell growth, survival, differentiation and gene expression in human diseases. As a member of the KDM4 family, KDM4B specifically targets H1.4K26, H3K9, H3K36, and H4K20, which affects both histone methylation and gene expression. Therefore, KDM4B is often regarded as a key intermediate protein in cellular pathways that plays an important role in growth and development as well as organ differentiation. However, KDM4B is broadly defined as an oncoprotein that plays key roles in processes related to tumorigenesis, including cell proliferation, cell survival, metastasis and so on. In this review, we discuss the diverse roles of KDM4B in contributing to cancer progression and normal developmental processes. Furthermore, we focus on recent studies highlighting the oncogenic functions of KDM4B in various kinds of cancers, which may be a novel therapeutic target for cancer treatment. We also provide a relatively complete report of the progress of research related to KDM4B inhibitors and discuss their potential as therapeutic agents for overcoming cancer.

Mechanism of the fungal-like particles in the inhibition of adipogenesis in 3T3-L1 adipocytes

The dynamic ability of adipocytes in adipose tissue to store lipid in response to changes in the nutritional input and inflammatory elicitors has a major impact on human health. Previously, we established laminarin-coated beads or LCB as an inflammatory elicitor for adipocytes. However, it was not clear whether LCB inhibits lipid accumulation in adipocytes. Here, we show that LCB acts in the early stage of adipogenesis through both interleukin-1 receptor-associated kinases (IRAK) and spleen tyrosine kinase (SYK) pathways, resulting in the activation of the AMP-activated protein kinase (AMPK) and nuclear factor-κB (NF-κB) complexes, which subsequently cause cell cycle arrest, downregulation of the key transcription factors and enzymes responsible for adipogenesis, inhibition of adipogenesis, and stimulation of an inflammatory response. While LCB could effectively block lipid accumulation during the early stage of adipogenesis, it could stimulate an inflammatory response at any stage of differentiation. Additionally, our results raise a possibility that toll-like receptor 2 (TLR2) and C-type lectin domain family 7 member A (CLEC7A/Dectin-1) might be potential β-glucan receptors on the fat cells. Together, we present the mechanism of LCB, as fungal-like particles, that elicits an inflammatory response and inhibits adipogenesis at the early stage of differentiation.

Chrysanthemum indicum suppresses adipogenesis by inhibiting mitotic clonal expansion in 3T3-L1 preadipocytes

Herbs have been of interest to treat diseases, including obesity, owing to their various bioactive constituents that exhibit therapeutic and prophylactic properties. The present study examined the anti-adipogenic effects and mechanisms of Chrysanthemum indicum aqueous extract (CAE) in 3T3-L1 preadipocytes. CAE comprises 1,3-dicaffeoylquinic acid, chlorogenic acid, kaempferol-3-O-glucoside, caffeic acid, and apigenin, which were corresponded with previous reports. CAE inhibited the accumulation of lipid droplets and significantly alleviated the expression of lipogenesis- and adipogenesis-associated biomarkers. Treatment with CAE inhibited the mitotic clonal expansion (MCE), corroborated by cell cycle arrest at the G₀ /G₁ phase, and mitigated the expression of cell cycle progression-associated proteins and in addition to phosphorylation of MCE-promoting transcription factors. Moreover, CAE downregulated the activation of Akt and extracellular signal-regulated kinase 1/2 signaling pathways. In summary, CAE facilitates adipogenic inhibition during the early phase of differentiation, especially MCE, and its phenolic compounds can contribute to its anti-obesogenic properties. PRACTICAL APPLICATIONS: Chrysanthemum indicum has been mainly used as traditional herbal tea and drinks. Chrysanthemum indicum aqueous extract (CAE) inhibits adipogenesis by suppressing mitotic clonal expansion during the early phase of differentiation in 3T3-L1 preadipocytes. 1,3-Dicaffeoylquinic acid, chlorogenic acid, kaempferol-3-O-glucoside, caffeic acid, and apigenin were detected in CAE. Based on these findings, CAE can be used as nutraceutical agents for prevention and treatment of obesity.

HMGB2 orchestrates mitotic clonal expansion by binding to the promoter of C/EBPβ to facilitate adipogenesis

High-mobility group box 2 (HMGB2) is an abundant, chromatin-associated protein that plays an essential role in the regulation of transcription, cell proliferation, differentiation, and tumorigenesis. However, the underlying mechanism of HMGB2 in adipogenesis remains poorly known. Here, we provide evidence that HMGB2 deficiency in preadipocytes impedes adipogenesis, while overexpression of HMGB2 increases the potential for adipogenic differentiation. Besides, depletion of HMGB2 in vivo caused the decrease in body weight, white adipose tissue (WAT) mass, and adipocyte size. Consistently, the stromal vascular fraction (SVF) of adipose tissue derived from hmgb2-/- mice presented impaired adipogenesis. When hmgb2-/- mice were fed with high-fat diet (HFD), the body size, and WAT mass were increased, but at a lower rate. Mechanistically, HMGB2 mediates adipogenesis via enhancing expression of C/EBPβ by binding to its promoter at "GGGTCTCAC" specifically during mitotic clonal expansion (MCE) stage, and exogenous expression of C/EBPβ can rescue adipogenic abilities of preadipocytes in response to HMGB2 inhibition. In general, our findings provide a novel mechanism of HMGB2-C/EBPβ axis in adipogenesis and a potential therapeutic target for obesity.

MYOD1 inhibits avian adipocyte differentiation via miRNA-206/KLF4 axis

BACKGROUND

A considerable number of muscle development-related genes were differentially expressed in the early stage of avian adipocyte differentiation. However, the functions of them in adipocyte differentiation remain largely known. In this study, the myoblast determination protein 1 (MYOD1) was selected as a representative of muscle development. We investigated its expression, function, and regulation in avian adipocyte differentiation.

RESULTS

The expression of MYOD1 decreased significantly in the early stage of avian adipocyte differentiation. CRISPR/Cas9-mediated deletion of MYOD1 induced adipocyte differentiation, whereas over-expression of MYOD1 inhibited adipogenesis. The mRNA-seq data showed that MYOD1 could perturb the lipid biosynthetic process during differentiation. Our results showed that MYOD1 directly up-regulates the miR-206 expression by binding the upstream 1200 bp region of miR-206. Then, over-expression of miR-206 can inhibit the adipogenesis. Furthermore, MYOD1 affected the expression of endogenous miR-206 and its target gene Kruppel-like factor 4 (KLF4), which is an important activator of adipogenesis. Accordingly, the inhibition of miR-206 or over-expression of KLF4 could counteract the inhibitory effect of MYOD1 on adipocyte differentiation.

CONCLUSIONS

Our results establish that MYOD1 inhibits adipocyte differentiation by up-regulating miR-206 to suppress the KLF4 expression. These findings identify a novel function of MYOD1 in adipocyte differentiation, suggesting a potential role in body-fat distribution regulation.

Thrombopoietic effects of CCAAT/enhancer-binding protein β on the early-stage differentiation of megakaryocytes

CCAAT/enhancer-binding protein β (C/EBPβ) is a transcription factor that is involved in adipocytic and monocytic differentiation. However, the physiological role of C/EBPβ in megakaryocytes (MKs) is not clear. In this study, we investigated the effects of C/EBPβ on the early-stage differentiation of MKs, and explored the potential mechanisms of action. We established a cytosine arabinoside-induced thrombocytopenia mouse model using C57BL/6 mice. In the thrombocytopenia mice, the platelet count was found to be decreased, and the mRNA and protein expression levels of C/EBPβ in MKs were also reduced. Furthermore, the maturation of Dami (MKs cell line) cells was induced by phorbol 12-myristate 13-acetate. When C/EBPβ was silenced in Dami cells by transfection using C/EBPβ-small interfering RNA, the expression of MKs-specific markers CD41 and CD62P, was dramatically decreased, resulting in morphological changes and differentiation retardation in low ploidy, which were evaluated using flow cytometry, real-time polymerase chain reaction, western blot, and confocal microscopy. The mitogen activated protein kinase-extracellular signal-regulated kinase signaling pathway was found to be required for the differentiation of MKs; knockdown of C/EBPβ in MEK/ERK1/2 pathway attenuated MKs differentiation. Overexpression of C/EBPβ in MEK/ERK1/2 pathway inhibited by U0126 did not promote MKs differentiation. To the best of our knowledge, C/EBPβ plays an important role in MKs differentiation and polyploidy cell cycle control. Taken together, C/EBPβ may have thrombopoietic effects in the differentiation of MKs, and may assist in the development of treatments for various disorders.

Emerging trends in chromatin remodeler plasticity in mesenchymal stromal cell function

Emerging evidences highlight importance of epigenetic regulation and their integration with transcriptional and cell signaling machinery in determining tissue resident adult pluripotent mesenchymal stem/stromal cell (MSC) activity, lineage commitment, and multicellular development. Histone modifying enzymes and large multi-subunit chromatin remodeling complexes and their cell type-specific plasticity remain the central defining features of gene regulation and establishment of tissue identity. Modulation of transcription factor expression gradient ex vivo and concomitant flexibility of higher order chromatin architecture in response to signaling cues are exciting approaches to regulate MSC activity and tissue rejuvenation. Being an important constituent of the adult bone marrow microenvironment/niche, pathophysiological perturbation in MSC homeostasis also causes impaired hematopoietic stem/progenitor cell function in a non-cell autonomous mechanism. In addition, pluripotent MSCs can function as immune regulatory cells, and they reside at the crossroad of innate and adaptive immune response pathways. Research in the past few years suggest that MSCs/stromal fibroblasts significantly contribute to the establishment of immunosuppressive microenvironment in shaping antitumor immunity. Therefore, it is important to understand mesenchymal stromal epigenome and transcriptional regulation to leverage its applications in regenerative medicine, epigenetic memory-guided trained immunity, immune-metabolic rewiring, and precision immune reprogramming. In this review, we highlight the latest developments and prospects in chromatin biology in determining MSC function in the context of lineage commitment and immunomodulation.

Lifestyle intervention in individuals with impaired glucose regulation affects Caveolin-1 expression and DNA methylation

Aims: We investigated whether a lifestyle intervention could influence expression and DNA methylation of diabetes-related genes in patients with impaired glucose regulation (IGR), the results were compared to bariatric surgery, considering it an intensive change. Methods: Twenty participants with IGR had adipose tissue biopsy and blood collected pre- and post-lifestyle (6 months) intervention; 12 obese patients had subcutaneous fat taken before and after bariatric surgery. RNA/DNA was extracted from all samples and underwent qPCR. DNA was bisulphite converted and 12 CpG sites of Caveolin-1 (CAV1) promoter were pyrosequenced. Results: lifestyle intervention resulted in opposite direction changes in fat tissue and blood for CAV1 expression and DNA methylation and these changes were correlated between tissues, while no significative differences were found in CAV1 expression after bariatric surgery. Conclusions: Our findings suggest a role for CAV1 in modulating adipocyte function as a consequence of lifestyle changes, as exercises and diet. These results may provide insights into new therapeutic targets for diabetes prevention.

Inula britannica Inhibits Adipogenesis of 3T3-L1 Preadipocytes via Modulation of Mitotic Clonal Expansion Involving ERK 1/2 and Akt Signaling Pathways

The flower of Inula britannica contains various phenolic compounds with prophylactic properties. This study aimed to determine the anti-adipogenic effect of an I. britannica flower aqueous extract (IAE) and its underlying mechanisms in the 3T3-L1 preadipocytes and to identify the phenolic compounds in the extract. Treatment with IAE inhibited the adipogenesis by showing a dose-dependent suppressed intracellular lipid accumulation and mitigated expression levels of lipogenesis- and adipogenesis-associated biomarkers including transcription factors. IAE exerted an anti-adipogenic effect through the modulation of the early phases of adipogenesis including mitotic clonal expansion (MCE). Treatment with IAE inhibited MCE by arresting the cell cycle at the G0/G1 phase and suppressing the activation of MCE-related transcription factors. Furthermore, IAE inhibited adipogenesis by regulating the extracellular signal-regulated kinase 1/2 and Akt signaling pathways. Protocatechuic acid, chlorogenic acid, kaempferol-3-O-glucoside, and 6-methoxyluteolin, which are reported to exhibit anti-adipogenic properties, were detected in IAE. Therefore, modulation of early phases of adipogenesis, especially MCE, is a key mechanism underlying the anti-adipogenic activity of IAE. In summary, the anti-obesity effects of IAE can be attributed to its phenolic compounds, and hence, IAE can be used for the development of anti-obesity products.

Molecular Mechanisms of Adipogenesis: The Anti-adipogenic Role of AMP-Activated Protein Kinase

Obesity is now a widespread disorder, and its prevalence has become a critical concern worldwide, due to its association with common co-morbidities like cancer, cardiovascular diseases and diabetes. Adipose tissue is an endocrine organ and therefore plays a critical role in the survival of an individual, but its dysfunction or excess is directly linked to obesity. The journey from multipotent mesenchymal stem cells to the formation of mature adipocytes is a well-orchestrated program which requires the expression of several genes, their transcriptional factors, and signaling intermediates from numerous pathways. Understanding all the intricacies of adipogenesis is vital if we are to counter the current epidemic of obesity because the limited understanding of these intricacies is the main barrier to the development of potent therapeutic strategies against obesity. In particular, AMP-Activated Protein Kinase (AMPK) plays a crucial role in regulating adipogenesis – it is arguably the central cellular energy regulation protein of the body. Since AMPK promotes the development of brown adipose tissue over that of white adipose tissue, special attention has been given to its role in adipose tissue development in recent years. In this review, we describe the molecular mechanisms involved in adipogenesis, the role of signaling pathways and the substantial role of activated AMPK in the inhibition of adiposity, concluding with observations which will support the development of novel chemotherapies against obesity epidemics.

Anti-Obesity Effects of Tanshinone I from Salvia miltiorrhiza Bunge in Mice Fed a High-Fat Diet through Inhibition of Early Adipogenesis

Tanshinone I (Tan I) is a diterpenoid isolated from Salvia miltiorrhiza Bunge and exhibits antitumor effects in several cancers. However, the anti-obesity properties of Tan I remain unexplored. Here, we evaluated the anti-obesity effects of Tan I in high-fat-diet (HFD)-induced obese mice and investigated the underlying molecular mechanisms in 3T3-L1 cells. HFD-induced obese mice were orally administrated Tan I for eight weeks, and body weight, weight gain, hematoxylin and eosin staining and serum biological parameters were examined. The adipogenesis of 3T3-L1 preadipocytes was assessed using Oil Red O staining and measurement of intracellular triglyceride (TG) levels, and mitotic clonal expansion (MCE) and its related signal molecules were analyzed during early adipogenesis of 3T3-L1 cells. The administration of Tan I significantly reduced body weight, weight gain, and white adipocyte size, and improved obesity-induced serum levels of glucose, free fatty acid, total TG, and total cholesterol in vivo in HFD-induced obese mice. Furthermore, Tan I-administered mice demonstrated improvement of glucose metabolism and insulin sensitivity. Treatment with Tan I inhibited the adipogenesis of 3T3-L1 preadipocytes in vitro, with this inhibition mainly occurring at an early phase of adipogenesis through the attenuation of MCE via cell cycle arrest at the G1/S phase transition. Tan I inhibited the phosphorylation of p38, extracellular signal-regulated kinase (ERK), and Akt during the process of MCE, while it stimulated the phosphorylation of AMP-activated protein kinase. Furthermore, Tan I repressed the expression of CCAAT-enhancer-binding protein β (C/EBPβ), histone H3K9 demethylase JMJD2B, and subsequently cell cycle genes. Moreover, Tan I regulated the expression of early adipogenic transcription factors including GATAs and Kruppel-like factor family factors. These results indicate that Tan I prevents HFD-induced obesity via the inhibition of early adipogenesis, and thus improves glucose metabolism and insulin sensitivity. This suggests that Tan I possesses therapeutic potential for the treatment of obesity and obesity-related diseases.

Histone demethylase KDM4D cooperates with NFIB and MLL1 complex to regulate adipogenic differentiation of C3H10T1/2 mesenchymal stem cells

The coordinated and sequential actions of lineage-specific transcription factors and epigenetic regulators are essential for the initiation and maintenance of cellular differentiation. We here report KDM4D histone demethylase as a key regulator of adipogenesis in C3H10T1/2 mesenchymal stem cells. The depletion of KDM4D results in impaired differentiation, which can be rescued by exogenous KDM4D, PPARγ, and C/EBPα, but not by C/EBPβ. In addition, KDM4D interacts physically and functionally with both NFIB and MLL1 complex to regulate C/EBPα and PPARγ expression upon adipogenic hormonal induction. Although KDM4D is dispensable for the binding of both NFIB and MLL1 complex to the target promoters, the demethylation of tri-methylated H3K9 by KDM4D is required for NFIB and MLL1 complex to deposit tri-methylated H3K4 and activate PPARγ and C/EBPα expression. Taken together, our data provide a molecular framework for lineage-specific transcription factor and histone modifiers to cooperate in adipogenic differentiation, in which KDM4D removes repressive histone marks at genes with a bivalent chromatin domain and allows NFIB and MLL1 complex to promote the expression of key adipogenic regulators.

Epigenetic Regulation of Adipogenic Differentiation by Histone Lysine Demethylation

Obesity is a rising public health problem that contributes to the development of several metabolic diseases and cancer. Adipocyte precursors outside of adipose depots that expand due to overweight and obesity may have a negative impact on human health. Determining how progenitor cells acquire a preadipocyte commitment and become mature adipocytes remains a significant challenge. Over the past several years, we have learned that the establishment of cellular identity is widely influenced by changes in histone marks, which in turn modulate chromatin structure. In this regard, histone lysine demethylases (KDMs) are now emerging as key players that shape chromatin through their ability to demethylate almost all major histone methylation sites. Recent research has shown that KDMs orchestrate the chromatin landscape, which mediates the activation of adipocyte-specific genes. In addition, KDMs have functions in addition to their enzymatic activity, which are beginning to be revealed, and their dysregulation seems to be related to the development of metabolic disorders. In this review, we highlight the biological functions of KDMs that contribute to the establishment of a permissive or repressive chromatin environment during the mesenchymal stem cell transition into adipocytes. Understanding how KDMs regulate adipogenesis might prompt the development of new strategies for fighting obesity-related diseases.

Benzyl Isothiocyanate and Phenethyl Isothiocyanate Inhibit Adipogenesis and Hepatosteatosis in Mice with Obesity Induced by a High-Fat Diet

Benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC) are organosulfur phytochemicals rich in cruciferous vegetables. We investigated the antiobesity and antihepatosteatosis activities of BITC and PEITC and the working mechanisms involved. C57BL/6J mice were fed a low-fat diet (LFD), a high-fat diet (HFD), or a HFD supplemented with 0.5 (L) or 1 g/kg (H) BITC or PEITC for 18 weeks. Compared with the HFD group, BITC or PEITC decreased the final body weight of mice in a dose-dependent manner [39.0 ± 3.1 (HFD), 34.4 ± 3.2 (BITC-L), 32.4 ± 2.8 (BITC-H), 36.2 ± 4.4 (PEITC-L), and 32.8 ± 2.9 (PEITC-H) g, p < 0.05], relative weight of epididymal fat [5.7 ± 0.4 (HFD), 4.7 ± 0.7 (BITC-L), 3.7 ± 0.3 (BITC-H), 4.4 ± 1.0 (PEITC-L), and 3.2 ± 0.6 (PEITC-H) %, p < 0.05], hepatic triglycerides [98.4 ± 6.0 (HFD), 81.0 ± 8.9 (BITC-L), 63.5 ± 5.6 (BITC-H), 69.3 ± 5.6 (PEITC-L), and 49.4 ± 2.9 (PEITC-H) mg/g, p < 0.05], and plasma total cholesterol [140 ± 21.3 (HFD), 109 ± 5.6 (BITC-L), 101 ± 11.3 (BITC-H), 126 ± 8.3 (PEITC-L), and 91.8 ± 12.7 (PEITC-H) mg/dL, p < 0.05]. Q-PCR and immunoblotting assays revealed that BITC and PEITC suppressed the expression of liver X receptor α, sterol regulatory element-binding protein 1c, stearoyl-CoA desaturase 1, fatty acid synthase, and acetyl-CoA carboxylase in both epididymal adipose and liver tissues. After a single oral administration of 85 mg/kg BITC or PEITC, the maximum plasma concentrations ( C_max) of BITC and PEITC were 5.8 ± 2.0 μg/mL and 4.3 ± 1.9 μg/mL, respectively. In 3T3-L1 adipocytes, BITC and PEITC dose-dependently reduced adipocyte differentiation and cell cycle was arrested in G0/G1 phase. These findings indicate that BITC and PEITC ameliorate HFD-induced obesity and fatty liver by down-regulating adipocyte differentiation and the expression of lipogenic transcription factors and enzymes.

The brominated flame retardant PBDE 99 promotes adipogenesis via regulating mitotic clonal expansion and PPARγ expression

"Obesogens" have been widely accepted as chemicals that promote obesity, and there are many environmental pollutants that were functionally identified as obesogens. PBDE 99 is one of the most abundant PBDE congeners detected in human. However, its obesogenic effects are poorly understood. Here, we explore the in vitro effects of PBDE 99 on adipogenesis, which is a key process in obesogenesis. We observed an increase in adipogenesis when differentiating cells were exposed to PBDE 99. Further, the promoting effects of PBDE 99 on adipogenesis were most efficient during the first 4 days of 3T3-L1 differentiation. Consistent with this, early transcriptional factor CCAAT/enhancer-binding proteins β (C/EBPβ) was upregulated at Days 1 and 2 during differentiation, which is accompanied with the acceleration of mitotic clonal expansion (MCE) and the upregulation of terminal transcriptional factors C/EBPα and PPARγ2 from Day 2 or Day 4. Additionally, bisulfite genomic sequencing analysis revealed that PBDE 99 decreased methylation status of the CpG sites at PPARγ promoter region. Collectively, these findings demonstrate that PBDE 99 may be a potential environmental obesogen by promoting adipogenesis through facilitating MCE progression at early differentiation stage and upregulating key adipogenic factor PPARγ2 expression both in direct transcriptional and epigenetic regulation dependent manner.

Histone demethylase KDM5A is transactivated by the transcription factor C/EBPβ and promotes preadipocyte differentiation by inhibiting Wnt/β-catenin signaling

β-Catenin signaling is triggered by WNT proteins and is an important pathway that negatively regulates adipogenesis. However, the mechanisms controlling the expression of WNT proteins during adipogenesis remain incompletely understood. Lysine demethylase 5A (KDM5A) is a histone demethylase that removes trimethyl (me3) marks from lysine 4 of histone 3 (H3K4) and serves as a general transcriptional corepressor. Here, using the murine 3T3-L1 preadipocyte differentiation model and an array of biochemical approaches, including ChIP, immunoprecipitation, RT-qPCR, and immunoblotting assays, we show that Kdm5a is a target gene of CCAAT/enhancer-binding protein β (C/EBPβ), an important early transcription factor required for adipogenesis. We found that C/EBPβ binds to the Kdm5a gene promoter and transactivates its expression. We also found that siRNA-mediated KDM5A down-regulation inhibits 3T3-L1 preadipocyte differentiation. The KDM5A knockdown significantly up-regulates the negative regulator of adipogenesis Wnt6, having increased levels of the H3K4me3 mark on its promoter. We further observed that WNT6 knockdown significantly rescues adipogenesis inhibited by the KDM5A knockdown. Moreover, we noted that C/EBPβ negatively regulates Wnt6 expression by binding to the Wnt6 gene promoter and repressing Wnt6 transcription. Further experiments indicated that KDM5A interacts with C/EBPβ and that their interaction cooperatively inhibits Wnt6 transcription. Of note, C/EBPβ knockdown impaired the recruitment of KDM5A to the Wnt6 promoter, which had higher H3K4me3 levels. Our results suggest a mechanism involving C/EBPβ and KDM5A activities that down-regulates the Wnt/β-catenin pathway during 3T3-L1 preadipocyte differentiation.

Lipid Accumulation and Chronic Kidney Disease

Obesity and hyperlipidemia are the most prevalent independent risk factors of chronic kidney disease (CKD), suggesting that lipid accumulation in the renal parenchyma is detrimental to renal function. Non-esterified fatty acids (also known as free fatty acids, FFA) are especially harmful to the kidneys. A concerted, increased FFA uptake due to high fat diets, overexpression of fatty acid uptake systems such as the CD36 scavenger receptor and the fatty acid transport proteins, and a reduced β-oxidation rate underlie the intracellular lipid accumulation in non-adipose tissues. FFAs in excess can damage podocytes, proximal tubular epithelial cells and the tubulointerstitial tissue through various mechanisms, in particular by boosting the production of reactive oxygen species (ROS) and lipid peroxidation, promoting mitochondrial damage and tissue inflammation, which result in glomerular and tubular lesions. Not all lipids are bad for the kidneys: polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) seem to help lag the progression of chronic kidney disease (CKD). Lifestyle interventions, especially dietary adjustments, and lipid-lowering drugs can contribute to improve the clinical outcome of patients with CKD.

Regulation of the bi-directional cross-talk between ovarian cancer cells and adipocytes by SPARC

Ovarian cancer (OvCa) exhibits a specific predilection for metastasis to the omentum. Our earlier studies highlighted the tumour-suppressor effect of secreted protein acidic and rich in cysteine (SPARC) in OvCa through multi-faceted roles inhibiting cancer cell interactions within the peritoneal milieu. The goal of this study is to investigate the role of SPARC in OvCa interactions with omental adipocytes and its role in OvCa colonization in the omentum. We employed multi-pronged approach using primary omental adipocytes from Sparc knockout mice, genetically engineered human omental adipocytes in 3D co-cultures with OvCa cells, as well as treatment with recombinant SPARC protein. We show that SPARC suppresses multistep cascade in OvCa omental metastasis. SPARC inhibited in vivo and adipocyte-induced homing, proliferation, and invasion of OvCa cells. SPARC suppressed metabolic programming of both adipocytes and OvCa cells and exerted an inhibitory effect of adipocyte differentiation and their phenotypic switch to cancer-associated phenotype. Mechanistic studies revealed that this effect is mediated through inhibition of cEBPβ-NFkB-AP-1 transcription machinery. These findings define a novel and functionally important role of SPARC in OvCa and not only bridge the knowledge gap but highlight the need to consider SPARC protein expression in therapeutic development.

KDM4B: A Nail for Every Hammer?

Epigenetic changes are well-established contributors to cancer progression and normal developmental processes. The reversible modification of histones plays a central role in regulating the nuclear processes of gene transcription, DNA replication, and DNA repair. The KDM4 family of Jumonj domain histone demethylases specifically target di- and tri-methylated lysine 9 on histone H3 (H3K9me3), removing a modification central to defining heterochromatin and gene repression. KDM4 enzymes are generally over-expressed in cancers, making them compelling targets for study and therapeutic inhibition. One of these family members, KDM4B, is especially interesting due to its regulation by multiple cellular stimuli, including DNA damage, steroid hormones, and hypoxia. In this review, we discuss what is known about the regulation of KDM4B in response to the cellular environment, and how this context-dependent expression may be translated into specific biological consequences in cancer and reproductive biology.

Histone H3K9 demethylase JMJD2B induces hepatic steatosis through upregulation of PPARγ2

Understanding the epigenetic mechanisms underlying the progression of hepatic steatosis is important for identifying new therapeutic targets against nonalcoholic fatty liver disease (NAFLD). We investigated the functional role of histone demethylase JMJD2B in the pathologic regulation of hepatic steatosis. JMJD2B expression was markedly increased in HepG2 cells treated with palmitate and oleate or liver X receptor agonist T09013178 and in the liver of high-fat diet (HFD)-induced obese mice. Overexpression of JMJD2B using adenovirus in HepG2 cells stimulated the expression of peroxisome proliferator-activated receptor γ2 (PPARγ2) and its steatosis target genes associated with fatty acid uptake and lipid droplet formation, resulting in increased intracellular triglyceride (TG) accumulation. Conversely, knocking down JMJD2B using siRNA reversed JMJD2B-mediated effects in HepG2 cells. The JMJD2B-dependent upregulation of PPARγ2 was associated with the removal of di- and trimethylation of histone H3 lysine 9 on the promoter of PPARγ2. Furthermore, exogeneous expression of JMJD2B using adenovirus in mice resulted in hepatic steatosis when fed a HFD, which was accompanied with increased expression of hepatic PPARγ2 and its steatosis target genes. Together, our results provide novel insights into the pivotal role of JMJD2B in the development of hepatic steatosis through upregulation of PPARγ2 and steatosis target genes.

JMJD2B/KDM4B inactivation in adipose tissues accelerates obesity and systemic metabolic abnormalities

Obesity is a serious global health issue; however, the roles of genetics and epigenetics in the onset and progression of obesity are still not completely understood. The aim of this study was to determine the role of Kdm4b, which belongs to a subfamily of histone demethylases, in adipogenesis and fat metabolism in vivo. We established conditional Kdm4b knockout mice. Inactivation of Kdm4b in adipocytes (K4bKO) induced profound obesity in mice on a high fat diet (HFD). The HFD-fed K4bKO mice exhibited an increased volume of fat mass and higher expression levels of adipogenesis-related genes. In contrast, the genes involved in energy expenditure and mitochondrial functions were down-regulated. Supporting these findings, the energy expenditure of Kdm4b-deficient cells was markedly decreased. In addition, progression of glucose intolerance and hepatic steatosis with hepatocellular damages was observed. These data indicate that Kdm4b is a critical regulator of systemic metabolism via enhancing energy expenditure in adipocytes.

Krüppel-like factor 10 (KLF10) is transactivated by the transcription factor C/EBPβ and involved in early 3T3-L1 preadipocyte differentiation

Adipose tissue stores energy and plays an important role in energy homeostasis. CCAAT/enhancer-binding protein β (C/EBPβ) is an important early transcription factor for 3T3-L1 preadipocyte differentiation, facilitating mitotic clonal expansion (MCE) and transactivating C/EBPα and peroxisome proliferator-activated receptor-γ (PPARγ) to promote adipogenesis. C/EBPβ is induced early, but the expression of antimitotic C/EBPα and PPARγ is not induced until ∼48 h. The delayed expression of C/EBPα and PPARγ is thought to ensure MCE progression, but the molecular mechanism for this delay remains elusive. Here, we show that the zinc-finger transcription factor Krüppel-like factor 10 (KLF10) is induced after adipogenic induction and that its expression positively correlates with that of C/EBPβ but inversely correlates with expression of C/EBPα and PPARγ. C/EBPβ bound to the KLF10 promoter and transactivated its expression during MCE. KLF10 overexpression in 3T3-L1 preadipocyte repressed adipogenesis and decreased C/EBPα and PPARγ expression, whereas siRNA-mediated down-regulation of KLF10 enhanced adipogenesis and increased C/EBPα and PPARγ expression. Luciferase assays revealed an inhibitory effect of KLF10 on C/EBPα promoter activity. Using promoter deletion and mutation analysis, we identified a KLF10-binding site within the proximal promoter region of C/EBPα. Furthermore, KLF10 interacted with and recruited histone deacetylase 1 (HDAC1) to the C/EBPα promoter, decreasing acetylated histone H4 on the C/EBPα promoter and inactivating C/EBPα transcription. Because C/EBPα can transactivate PPARγ, our results suggest a mechanism by which expression of C/EBPα and PPARγ is delayed via KLF10 expression and shed light on the negative feedback loop for C/EBPβ-regulated adipogenesis in 3T3-L1 preadipocyte.

A network of epigenomic and transcriptional cooperation encompassing an epigenomic master regulator in cancer

Coordinated experiments focused on transcriptional responses and chromatin states are well-equipped to capture different epigenomic and transcriptomic levels governing the circuitry of a regulatory network. We propose a workflow for the genome-wide identification of epigenomic and transcriptional cooperation to elucidate transcriptional networks in cancer. Gene promoter annotation in combination with network analysis and sequence-resolution of enriched transcriptional motifs in epigenomic data reveals transcription factor families that act synergistically with epigenomic master regulators. By investigating complementary omics levels, a close teamwork of the transcriptional and epigenomic machinery was discovered. The discovered network is tightly connected and surrounds the histone lysine demethylase KDM3A, basic helix-loop-helix factors MYC, HIF1A, and SREBF1, as well as differentiation factors AP1, MYOD1, SP1, MEIS1, ZEB1, and ELK1. In such a cooperative network, one component opens the chromatin, another one recognizes gene-specific DNA motifs, others scaffold between histones, cofactors, and the transcriptional complex. In cancer, due to the ability to team up with transcription factors, epigenetic factors concert mitogenic and metabolic gene networks, claiming the role of a cancer master regulators or epioncogenes. Significantly, specific histone modification patterns are commonly associated with open or closed chromatin states, and are linked to distinct biological outcomes by transcriptional activation or repression. Disruption of patterns of histone modifications is associated with the loss of proliferative control and cancer. There is tremendous therapeutic potential in understanding and targeting histone modification pathways. Thus, investigating cooperation of chromatin remodelers and the transcriptional machinery is not only important for elucidating fundamental mechanisms of chromatin regulation, but also necessary for the design of targeted therapeutics.

Nasal DNA methylation is associated with childhood asthma

AIM

We aim to study DNA methylation (DNAm) variations associated with childhood asthma.

METHODS

Nasal DNAm was compared between sibling pairs discordant for asthma, 29 sib pairs for genome-wide association studies and 54 sib pairs for verification by pyrosequencing. Associations of methylation with asthma symptoms, allergy and environmental exposures were evaluated. In vitro experiments and functional genomic analyses were performed to explore biologic relevance.

RESULTS

Three CpGs were associated with asthma. cg14830002 was associated with allergies in nonasthmatics. cg23602092 was associated with asthma symptoms. cg14830002 and cg23602092 were associated with traffic-related air pollution exposure. Nearby genes were transcriptionally regulated by diesel exhaust, house dust mite and 5-aza-2'-deoxycytidine. Active chromatin marks and transcription factor binding were found around these sites.

CONCLUSION

We identified novel DNAm variations associated with childhood asthma and suggested new disease-contributing epigenetic mechanisms.

The involvement of histone methylation in osteoblastic differentiation of human periosteum-derived cells cultured in vitro under hypoxic conditions

Although oxygen concentrations affect the growth and function of mesenchymal stem cells (MSCs), the impact of hypoxia on osteoblastic differentiation is not understood. Likewise, the effect of hypoxia-induced epigenetic changes on osteoblastic differentiation of MSCs is unknown. The aim of this study was to examine the in vitro hypoxic response of human periosteum-derived cells (hPDCs). Hypoxia resulted in greater proliferation of hPDCs as compared with those cultured in normoxia. Further, hypoxic conditions yielded decreased expression of apoptosis- and senescence-associated genes by hPDCs. Osteoblast phenotypes of hPDCS were suppressed by hypoxia, as suggested by alkaline phosphatase activity, alizarin red-S-positive mineralization, and mRNA expression of osteoblast-related genes. Chromatin immunoprecipitation assays showed an increased presence of H3K27me3, trimethylation of lysine 27 on histone H3, on the promoter region of bone morphogenetic protein-2. In addition, mRNA expression of histone lysine demethylase 6B (KDM6B) by hPDCs was significantly decreased in hypoxic conditions. Our results suggest that an increased level of H3K27me3 on the promoter region of bone morphogenetic protein-2, in combination with downregulation of KDM6B activity, is involved in the suppression of osteogenic phenotypes of hPDCs cultured in hypoxic conditions. Although oxygen tension plays an important role in the viability and maintenance of MSCs in an undifferentiated state, the effect of hypoxia on osteoblastic differentiation of MSCs remains controversial. In addition, evidence regarding the importance of epigenetics in regulating MSCs has been limited. This study was to examine the role hypoxia on osteoblastic differentiation of hPDCs, and we examined whether histone methylation is involved in the observed effect of hypoxia on osteogenic differentiation of hPDCs.

Ligand-dependent corepressor (LCoR) represses the transcription factor C/EBPβ during early adipocyte differentiation

Nuclear receptors (NRs) regulate gene transcription by recruiting coregulators, involved in chromatin remodeling and assembly of the basal transcription machinery. The NR-associated protein ligand-dependent corepressor (LCoR) has previously been shown to suppress hepatic lipogenesis by decreasing the binding of steroid receptor coactivators to thyroid hormone receptor. However, the role of LCoR in adipogenesis has not been established. Here, we show that LCoR expression is reduced in the early stage of adipogenesis in vitro LCoR overexpression inhibited 3T3-L1 adipocyte differentiation, whereas LCoR knockdown promoted it. Using an unbiased affinity purification approach, we identified CCAAT/enhancer-binding protein β (C/EBPβ), a key transcriptional regulator in early adipogenesis, and corepressor C-terminal binding proteins as potential components of an LCoR-containing complex in 3T3-L1 adipocytes. We found that LCoR directly interacts with C/EBPβ through its C-terminal helix-turn-helix domain, required for LCoR's inhibitory effects on adipogenesis. LCoR overexpression also inhibited C/EBPβ transcriptional activity, leading to inhibition of mitotic clonal expansion and transcriptional repression of C/EBPα and peroxisome proliferator-activated receptor γ2 (PPARγ2). However, LCoR overexpression did not affect the recruitment of C/EBPβ to the promoters of C/EBPα and PPARγ2 in 3T3-L1 adipocytes. Of note, restoration of PPARγ2 or C/EBPα expression attenuated the inhibitory effect of LCoR on adipogenesis. Mechanistically, LCoR suppressed C/EBPβ-mediated transcription by recruiting C-terminal binding proteins to the C/EBPα and PPARγ2 promoters and by modulating histone modifications. Taken together, our results indicate that LCoR negatively regulates early adipogenesis by repressing C/EBPβ transcriptional activity and add LCoR to the growing list of transcriptional corepressors of adipogenesis.

Coffee extract inhibits adipogenesis in 3T3-L1 preadipocyes by interrupting insulin signaling through the downregulation of IRS1

Although epidemiological data have indicated that a strong negative association exists between coffee consumption and the prevalence of obesity-associated diseases, the molecular mechanisms by which coffee intake prevents obesity-associated diseases has not yet been elucidated. In this study, we found that coffee intake significantly suppressed high-fat diet (HFD)-induced metabolic alternations such as increases in body weight and the accumulation of adipose tissue, and up-regulation of glucose, free fatty acid, total cholesterol and insulin levels in the blood. We also found that coffee extract significantly inhibited adipogenesis in 3T3-L1 preadipocytes. In the early phase of adipogenesis, 3T3-L1 cells treated with coffee extract displayed the retardation of cell cycle entry into the G2/M phase called as mitotic clonal expansion (MCE). Coffee extract also inhibited the activation of CCAAT/enhancer-binding protein β (C/EBPβ) by preventing its phosphorylation by ERK. Furthermore, the coffee extract suppressed the adipogenesis-related events such as MCE and C/EBPβ activation through the down-regulation of insulin receptor substrate 1 (IRS1). The stability of the IRS1 protein was markedly decreased by the treatment with coffee extract due to proteasomal degradation. These results have revealed an anti-adipogenic function for coffee intake and identified IRS1 as a novel target for coffee extract in adipogenesis.

Gomisin N inhibits adipogenesis and prevents high-fat diet-induced obesity

Gomisin N (GN) is a physiological lignan derived from Schisandra chinensis. In the present study, we investigated the inhibitory effects of GN on differentiation of 3T3-L1 preadipocytes and the anti-obesity effects of GN in high-fat diet (HFD)-induced obese mice. Incubation with GN significantly inhibited the differentiation of 3T3-L1 preadipocytes in a dose-dependent manner. This inhibitory effect primarily occurred at an early adipogenic stage through impairment of mitotic clonal expansion (MCE) caused by cell cycle arrest at the G1/S phase transition. GN inhibited the extracellular signal-regulated kinase and phosphoinositide 3-kinase/protein kinase B signaling in the MCE process and activated AMP-activated protein kinase. Furthermore, GN downregulated CCAT/enhancer-binding protein β (C/EBPβ) and histone H3K9 demethylase JMJD2B during early stages of adipogenesis, and therefore repressed the expression of C/EBPβ-targeted cell cycle genes. In addition, GN also repressed the expression of histone H3K4 methyltransferase MLL4 and reduced PPARγ expression. Moreover, GN effectively lowered the final body weight, adipose tissue mass, and reduced the serum levels of glucose, total triglyceride, and cholesterol in the HFD-induced obese mice. GN also markedly reduced hepatic triglyceride level induced by HFD. Collectively, these findings suggest that GN has potential as a novel agent for the prevention and treatment of obesity.

Histone H3K9 Demethylase JMJD2B Activates Adipogenesis by Regulating H3K9 Methylation on PPARγ and C/EBPα during Adipogenesis

Previous studies have shown that tri- or di-methylation of histone H3 at lysine 9 (H3K9me3/me2) on the promoter of the peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα) contribute to the repression of PPARγ and C/EBPα and inhibition of adipogenesis in 3T3-L1 preadipocytes. The balance of histone methylation is regulated by histone methyltransferases and demethylases. However, it is poorly understood which demethylases are responsible for removing H3K9me3/me2 on the promoter of PPARγ and C/EBPα. JMJD2B is a H3K9me3/me2 demethylase that was previously shown to activate adipogenesis by promoting mitotic clonal expansion. Nevertheless, it remains unclear whether JMJD2B plays a role in the regulation of adipogenesis by removing H3K9me3/me2 on the promoter of PPARγ and C/EBPα and subsequently activating PPARγ and C/EBPα expression. Here, we showed that JMJD2B decreased H3K9me3/me2 on the promoter of PPARγ and C/EBPα, which in turn stimulated the expression of PPARγ and C/EBPα. JMJD2B knockdown using siRNA in 3T3-L1 preadipocytes repressed the expression of PPARγ and C/EBPα, resulting in inhibition of adipogenesis. This was accompanied by increased enrichment of H3K9me3/me2 on the promoter of PPARγ and C/EBPα. In contrast, overexpression of JMJD2B increased the expression of PPARγ and C/EBPα, which was accompanied by decreased enrichment of H3K9me3/me2 on the promoter and activated adipogenesis. Together, these results indicate that JMJD2B regulates PPARγ and C/EBPα during adipogenesis.

Methyl gallate, a potent antioxidant inhibits mouse and human adipocyte differentiation and oxidative stress in adipocytes through impairment of mitotic clonal expansion

Methyl gallate (MG) is a derivative of gallic acid and a potent antioxidant. In this study, we confirmed that MG treatment effectively inhibits lipid accumulation, which occurred mostly in the early stages of adipogenesis. We also showed that shortly after adipogenic induction, MG facilitated a G0/G1 cell cycle arrest. Mechanistic studies revealed that MG treatment inhibited ERK1/2 phosphorylation, which is a key regulator of the G1- to S-phase transition. Furthermore, MG treatment prevented the adipogenic hormonal stimuli-induced inhibition of the cyclin-dependent kinase inhibitor p27^Kip1 . This led to inhibition of the transcription factor E2F1 by preventing the phosphorylation of, and thereby activation of its destruction partner RB. MG treatment also downregulated factors that are upstream of RB-E2F1 signaling such as Cdk2, Cyclin E, Cdk4, and Cyclin D1 where Cyclin D3 level was unaffected. We also found that MG treatment markedly decreased the expression and phosphorylation of C/EBPβ, by phosphorylating, and therefore inactivating, GSK3β, which is a prerequisite for its DNA binding capacity, and thereby mitotic clonal expansion (MCE). Ultimately, MG treatment downregulates key terminal adipogenic transcription factors including C/EBPα, PPARγ, aP2 (Fabp4), and adiponectin. Moreover, MG also protects adipocytes from oxidative stress by alleviating intracellular reactive oxygen species and activating Nrf2, HO-1, and PRDX3. Thus, this study provides a mechanistic insight into the anti-adipogenic actions of MG. © 2016 BioFactors, 42(6):716-726, 2016.

Silencing the epigenetic silencer KDM4A for TRAIL and DR5 simultaneous induction and antitumor therapy

Recombinant TRAIL and agonistic antibodies to death receptors (DRs) have been in clinical trial but displayed limited anti-cancer efficacy. Lack of functional DR expression in tumors is a major limiting factor. We report here that chromatin regulator KDM4A/JMJD2A, not KDM4B, has a pivotal role in silencing tumor cell expression of both TRAIL and its receptor DR5. In TRAIL-sensitive and -resistant cancer cells of lung, breast and prostate, KDM4A small-molecule inhibitor compound-4 (C-4) or gene silencing strongly induces TRAIL and DR5 expression, and causes TRAIL-dependent apoptotic cell death. KDM4A inhibition also strongly sensitizes cells to TRAIL. C-4 alone potently inhibits tumor growth with marked induction of TRAIL and DR5 expression in the treated tumors and effectively sensitizes them to the newly developed TRAIL-inducer ONC201. Mechanistically, C-4 does not appear to act through the Akt-ERK-FOXO3a pathway. Instead, it switches histone modifying enzyme complexes at promoters of TRAIL and DR5 transcriptional activator CHOP gene by dissociating KDM4A and nuclear receptor corepressor (NCoR)-HDAC complex and inducing the recruitment of histone acetylase CBP. Thus, our results reveal KDM4A as a key epigenetic silencer of TRAIL and DR5 in tumors and establish inhibitors of KDM4A as a novel strategy for effectively sensitizing tumors to TRAIL pathway-based therapeutics.

C/EBPβ regulates sensitivity to bortezomib in prostate cancer cells by inducing REDD1 and autophagosome-lysosome fusion

The purpose of this study was to ascertain the mechanisms by which advanced prostate cancer cells resist bortezomib therapy. Several independent studies have shown that cells are protected from proteasome inhibition by increased autophagic activity. We investigated whether C/EBPβ, a transcription factor involved in the control of autophagic gene expression, regulates resistance to proteasome inhibition. In PC3 cells over-expressing C/EBPβ, turnover of autophagic substrates and expression of core autophagy genes were increased. Conversely, C/EBPβ knockdown suppressed autophagosome-lysosome fusion. We also found that C/EBPβ knockdown suppressed REDD1 expression to delay early autophagy, an effect rescued by exogenous REDD1. Cells with suppressed C/EBPβ levels showed delayed autophagy activation upon bortezomib treatment. Knockdown of C/EBPβ sensitized PC3 cells to bortezomib, and blockade of autophagy by chloroquine did not further increase cell death in cells expressing shRNA targeting C/EBPβ. Lastly, we observed a decreased growth of PC3 cells and xenografts with C/EBPβ knockdown and such xenografts were sensitized to bortezomib treatment. Our results demonstrate that C/EBPβ is a critical effector of autophagy via regulation of autolysosome formation and promotes resistance to proteasome inhibitor treatment by increasing autophagy.

Histone methyltransferases and demethylases: regulators in balancing osteogenic and adipogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are characterized by their self-renewing capacity and differentiation potential into multiple tissues. Thus, management of the differentiation capacities of MSCs is important for MSC-based regenerative medicine, such as craniofacial bone regeneration, and in new treatments for metabolic bone diseases, such as osteoporosis. In recent years, histone modification has been a growing topic in the field of MSC lineage specification, in which the Su(var)3–9, enhancer-of-zeste, trithorax (SET) domain-containing family and the Jumonji C (JmjC) domain-containing family represent the major histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs), respectively. In this review, we summarize the current understanding of the epigenetic mechanisms by which SET domain-containing KMTs and JmjC domain-containing KDMs balance the osteogenic and adipogenic differentiation of MSCs.

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ are transcription factors of the basic-leucine zipper class which share phylogenetic, structural and functional features. In this review we first describe in depth their basic molecular biology which includes fascinating aspects such as the regulated use of alternative initiation codons in the C/EBPβ mRNA. The physical interactions with multiple transcription factors which greatly opens the number of potentially regulated genes or the presence of at least five different types of post-translational modifications are also remarkable molecular mechanisms that modulate C/EBPβ and C/EBPδ function. In the second part, we review the present knowledge on the localization, expression changes and physiological roles of C/EBPβ and C/EBPδ in neurons, astrocytes and microglia. We conclude that C/EBPβ and C/EBPδ share two unique features related to their role in the CNS: whereas in neurons they participate in memory formation and synaptic plasticity, in glial cells they regulate the pro-inflammatory program. Because of their role in neuroinflammation, C/EBPβ and C/EBPδ in microglia are potential targets for treatment of neurodegenerative disorders. Any strategy to reduce C/EBPβ and C/EBPδ activity in neuroinflammation needs to take into account its potential side-effects in neurons. Therefore, cell-specific treatments will be required for the successful application of this strategy.

Transcriptional regulation of adipocyte differentiation: a central role for CCAAT/enhancer-binding protein (C/EBP) β

A detailed understanding of the processes controlling adipogenesis is instrumental in the fight against the obesity epidemic. Adipogenesis is controlled by a transcriptional cascade composed of a large number of transcriptional factors, among which CCAAT/enhancer-binding protein (C/EBP) β plays an essential role. During 3T3-L1 adipocyte differentiation, C/EBPβ is induced early to transactivate the expression of C/EBPα and peroxisome proliferator-activated receptor γ (PPARγ), two master transcription factors for terminal adipocyte differentiation. Studies in recent years have revealed many new target genes of C/EBPβ, implicating its participation in many other processes during adipogenesis, such as mitotic clonal expansion, epigenetic regulation, unfolded protein response, and autophagy. Moreover, the function of C/EBPβ is highly regulated by post-translational modifications, which are crucial for the proper activation of the adipogenic program. Advances toward elucidation of the function and roles of the post-translational modification of C/EBPβ during adipogenesis will greatly improve our understanding of the molecular mechanisms governing adipogenesis.

GPS2/KDM4A pioneering activity regulates promoter-specific recruitment of PPARγ

Timely and selective recruitment of transcription factors to their appropriate DNA-binding sites represents a critical step in regulating gene activation; however, the regulatory strategies underlying each factor's effective recruitment to specific promoter and/or enhancer regions are not fully understood. Here, we identify an unexpected regulatory mechanism by which promoter-specific binding, and therefore function, of peroxisome proliferator-activator receptor γ (PPARγ) in adipocytes requires G protein suppressor 2 (GPS2) to prime the local chromatin environment via inhibition of the ubiquitin ligase RNF8 and stabilization of the H3K9 histone demethylase KDM4A/JMJD2. Integration of genome-wide profiling data indicates that the pioneering activity of GPS2/KDM4A is required for PPARγ-mediated regulation of a specific transcriptional program, including the lipolytic enzymes adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL). Hence, our findings reveal that GPS2 exerts a biologically important function in adipose tissue lipid mobilization by directly regulating ubiquitin signaling and indirectly modulating chromatin remodeling to prime selected genes for activation.

Suv39h1 mediates AP-2α-dependent inhibition of C/EBPα expression during adipogenesis

Previous studies have shown that CCAAT/enhancer-binding protein α (C/EBPα) plays a very important role during adipocyte terminal differentiation and that AP-2α (activator protein 2α) acts as a repressor to delay the expression of C/EBPα. However, the mechanisms by which AP-2α prevents the expression of C/EBPα are not fully understood. Here, we present evidence that Suv39h1, a histone H3 lysine 9 (H3K9)-specific trimethyltransferase, and G9a, a euchromatic methyltransferase, both interact with AP-2α and enhance AP-2α-mediated transcriptional repression of C/EBPα. Interestingly, we discovered that G9a mediates dimethylation of H3K9, thus providing the substrate, which is methylated by Suv39h1, to H3K9me3 on the C/EBPα promoter. The expression level of AP-2α was consistent with enrichment of H3K9me2 and H3K9me3 on the C/EBPα promoter in 3T3-L1 preadipocytes. Knockdown of Suv39h markedly increased C/EBPα expression and promoted adipogenesis. Conversely, ectopic expression of Suv39h1 delayed C/EBPα expression and impaired the accumulation of triglyceride, while simultaneous knockdown of AP-2α or G9a partially rescued this process. These findings indicate that Suv39h1 enhances AP-2α-mediated transcriptional repression of C/EBPα in an epigenetic manner and further inhibits adipocyte differentiation.