Role of the CCAAT enhancer binding proteins (C/EBPs) in adipocyte differentiation

The Long Non-Coding RNA Obesity-Related (Obr) Contributes To Lipid Metabolism Through Epigenetic Regulation

Obesity is a multifactorial disease that is part of today's epidemic and also increases the risk of other metabolic diseases. Long noncoding RNAs (lncRNAs) provide one tier of regulatory mechanisms to maintain metabolic homeostasis. Although lncRNAs are a significant constituent of the mammalian genome, studies aimed at their metabolic significance, including obesity, are only beginning to be addressed. Here, a developmentally regulated lncRNA, termed as obesity related (Obr), whose expression in metabolically relevant tissues such as skeletal muscle, liver, and pancreas is altered in diet-induced obesity, is identified. The Clone 9 cell line and high-fat diet-induced obese Wistar rats are used as a model system to verify the function of Obr. By using stable expression and antisense oligonucleotide-mediated downregulation of the expression of Obr followed by different molecular biology experiments, its role in lipid metabolism is verified. It is shown that Obr associates with the cAMP response element-binding protein (Creb) and activates different transcription factors involved in lipid metabolism. Its association with the Creb histone acetyltransferase complex, which includes the cAMP response element-binding protein (CBP) and p300, positively regulates the transcription of genes involved in lipid metabolism. In addition, Obr is regulated by Pparγ in response to lipid accumulation.

Vitamin D3 exacerbates steatosis while calcipotriol inhibits inflammation in non-alcoholic fatty liver disease in Sod1 knockout mice: a comparative study of two forms of vitamin D

The role of vitamin D (VD) in non-alcoholic fatty liver disease (NAFLD) remains controversial, possibly due to the differential effects of various forms of VD. In our study, Sod1 gene knockout (SKO) mice were utilized as lean NAFLD models, which were administered 15 000 IU VD3 per kg diet, or intraperitoneally injected with the active VD analog calcipotriol for 12 weeks. We found that VD3 exacerbated hepatic steatosis in SKO mice, with an increase in the levels of Cd36, Fatp2, Dgat2, and CEBPA. However, calcipotriol exerted no significant effect on hepatic steatosis. Calcipotriol inhibited the expression of Il-1a, Il-1b, Il-6, Adgre1, and TNF, with a reduction of NFκB phosphorylation in SKO mice. No effect was observed by either VD3 or calcipotriol on hepatocyte injury and hepatic fibrosis. Co-immunofluorescence stains of CD68, a liver macrophage marker, and VDR showed that calcipotriol reduced CD68 positive cells, and increased the colocalization of VDR with CD68. However, VD3 elevated hepatocyte VDR expression, with no substantial effect on the colocalization of VDR with CD68. Finally, we found that VD3 increased the levels of serum 25(OH)D3 and 24,25(OH)2D3, whereas calcipotriol decreased both. Both VD3 and calcipotriol did not disturb serum calcium and phosphate levels. In summary, our study found that VD3 accentuated hepatic steatosis, while calcipotriol diminished inflammation levels in SKO mice, and the difference might stem from their distinct cellular selectivity in activating VDR. This study provides a reference for the application of VD in the treatment of lean NAFLD.

AP-1/C-FOS and AP-1/FRA2 differentially regulate early and late adipogenic differentiation of mesenchymal stem cells

Obesity is defined as an abnormal accumulation of adipose tissue in the body and is a major global health problem due to increased morbidity and mortality. Adipose tissue is made up of adipocytes, which are fat-storing cells, and the differentiation of these fat cells is known as adipogenesis. Several transcription factors (TFs) such as CEBPβ, CEBPα, PPARγ, GATA, and KLF have been reported to play a key role in adipogenesis. In this study, we report one more TF AP-1, which is found to be involved in adipogenesis. Human mesenchymal stem cells  were differentiated into adipocytes, and the expression pattern of different subunits of AP-1 was examined during adipogenesis. It was observed that C-FOS was predominantly expressed at an early stage (Day 2), whereas FRA2 expression peaked at later stages (Days 6 and 8) of adipogenesis. Chromatin immunoprecipitation-sequencing analysis revealed that C-FOS binds mainly to the promoters of WNT1, miR-30a, and ANAPC7 and regulates their expression during mitotic clonal expansion. In contrast, FRA2 binds to the promoters of CIDEA, NOTCH1, ARAF, and MYLK, regulating their expression and lipid metabolism. Data obtained clearly indicate that the differential expression of C-FOS and FRA2 is crucial for different stages of adipogenesis. This also raises the possibility of considering AP-1 as a therapeutic target for treating obesity and related disorders.

TET2 is recruited by CREB to promote Cebpb, Cebpa, and Pparg transcription by facilitating hydroxymethylation during adipocyte differentiation

Ten-eleven translocation proteins (TETs) are dioxygenases that convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), an important epigenetic mark that regulates gene expression during development and differentiation. Here, we found that the TET2 expression was positively associated with adipogenesis. Further, in vitro and in vivo experiments showed that TET2 deficiency blocked adipogenesis by inhibiting the expression of the key transcription factors CCAAT/enhancer-binding protein beta (C/EBPβ), C/EBPα and peroxisome proliferator-activated receptor gamma (PPARγ). In addition, TET2 promoted 5hmC on the CpG islands (CGIs) of Cebpb, Cebpa and Pparg at the initial time point of their transcription, which requires the cAMP-responsive element-binding protein (CREB). At last, specific knockout of Tet2 in preadipocytes enabled mice to resist obesity and attenuated the obesity-associated insulin resistance. Together, TET2 is recruited by CREB to promote the expression of Cebpb, Cebpa and Pparg via 5hmC during adipogenesis and may be a potential therapeutic target for obesity and insulin resistance.

A Dual-Targeting Liposome Enhances Triple-Negative Breast Cancer Chemoimmunotherapy through Inducing Immunogenic Cell Death and Inhibiting STAT3 Activation

Immunotherapy gains increasing focus in treating triple-negative breast cancer (TNBC), while its efficacy is greatly restricted owing to low tumor immunogenicity and immunosuppressive tumor microenvironment (ITM). Herein, a LyP-1 and chondroitin sulfate (CS) dual-modified liposome co-loaded with paclitaxel (PTX) and cryptotanshinone (CTS), namely CS/LyP-1-PC Lip, is engineered for TNBC chemoimmunotherapy via induction of immunogenic cell death (ICD) and inhibition of signal transducer and activator of transcript-3 (STAT3) activation. CS/LyP-1-PC Lip enhances cellular uptake through p32 and CD44 dual receptor-mediated endocytosis. Within the tumor, the CS layer is continuously detached by hyaluronidase to release drugs. Subsequently, CTS sensitizes the cytotoxicity of PTX to 4T1 tumor cells. PTX induces ICD of tumor cells and facilitates infiltration of cytotoxic T lymphocyte to provoke immune response. Meanwhile, the concomitant delivery of CTS inhibits STAT3 activation to decrease infiltration of regulatory T cell, M2-type tumor-associated macrophage, and myeloid-derived suppressor cell, thus reversing ITM. Markedly, the dual-targeting liposome shows superior anti-tumor efficacy in subcutaneous TNBC mice and significant lung metastasis suppression in tumor metastasis model. Overall, this work offers a feasible combination regimen and a promising nanoplatform for the development of TNBC chemoimmunotherapy.

Brown Adipose Tissue-A Translational Perspective

Brown adipose tissue (BAT) displays the unique capacity to generate heat through uncoupled oxidative phosphorylation that makes it a very attractive therapeutic target for cardiometabolic diseases. Here, we review BAT cellular metabolism, its regulation by the central nervous and endocrine systems and circulating metabolites, the plausible roles of this tissue in human thermoregulation, energy balance, and cardiometabolic disorders, and the current knowledge on its pharmacological stimulation in humans. The current definition and measurement of BAT in human studies relies almost exclusively on BAT glucose uptake from positron emission tomography with 18F-fluorodeoxiglucose, which can be dissociated from BAT thermogenic activity, as for example in insulin-resistant states. The most important energy substrate for BAT thermogenesis is its intracellular fatty acid content mobilized from sympathetic stimulation of intracellular triglyceride lipolysis. This lipolytic BAT response is intertwined with that of white adipose (WAT) and other metabolic tissues, and cannot be independently stimulated with the drugs tested thus far. BAT is an interesting and biologically plausible target that has yet to be fully and selectively activated to increase the body's thermogenic response and shift energy balance. The field of human BAT research is in need of methods able to directly, specifically, and reliably measure BAT thermogenic capacity while also tracking the related thermogenic responses in WAT and other tissues. Until this is achieved, uncertainty will remain about the role played by this fascinating tissue in human cardiometabolic diseases.

Crosstalk of Inflammatory Cytokines within the Breast Tumor Microenvironment

Several immune and immunocompetent cells, including dendritic cells, macrophages, adipocytes, natural killer cells, T cells, and B cells, are significantly correlated with the complex discipline of oncology. Cytotoxic innate and adaptive immune cells can block tumor proliferation, and others can prevent the immune system from rejecting malignant cells and provide a favorable environment for tumor progression. These cells communicate with the microenvironment through cytokines, a chemical messenger, in an endocrine, paracrine, or autocrine manner. These cytokines play an important role in health and disease, particularly in host immune responses to infection and inflammation. They include chemokines, interleukins (ILs), adipokines, interferons, colony-stimulating factors (CSFs), and tumor necrosis factor (TNF), which are produced by a wide range of cells, including immune cells, such as macrophages, B-cells, T-cells, and mast cells, as well as endothelial cells, fibroblasts, a variety of stromal cells, and some cancer cells. Cytokines play a crucial role in cancer and cancer-related inflammation, with direct and indirect effects on tumor antagonistic or tumor promoting functions. They have been extensively researched as immunostimulatory mediators to promote the generation, migration and recruitment of immune cells that contribute to an effective antitumor immune response or pro-tumor microenvironment. Thus, in many cancers such as breast cancer, cytokines including leptin, IL-1B, IL-6, IL-8, IL-23, IL-17, and IL-10 stimulate while others including IL-2, IL-12, and IFN-γ, inhibit cancer proliferation and/or invasion and enhance the body's anti-tumor defense. Indeed, the multifactorial functions of cytokines in tumorigenesis will advance our understanding of cytokine crosstalk pathways in the tumor microenvironment, such as JAK/STAT, PI3K, AKT, Rac, MAPK, NF-κB, JunB, cFos, and mTOR, which are involved in angiogenesis, cancer proliferation and metastasis. Accordingly, targeting and blocking tumor-promoting cytokines or activating and amplifying tumor-inhibiting cytokines are considered cancer-directed therapies. Here, we focus on the role of the inflammatory cytokine system in pro- and anti-tumor immune responses, discuss cytokine pathways involved in immune responses to cancer and some anti-cancer therapeutic applications.

The glucocorticoid receptor represses, whereas C/EBPβ can enhance or repress CYP26A1 transcription

Retinoic acid (RA) counters insulin's metabolic actions. Insulin reduces liver RA biosynthesis by exporting FoxO1 from nuclei. RA induces its catabolism, catalyzed by CYP26A1. A CYP26A1 contribution to RA homeostasis with changes in energy status had not been investigated. We found that glucagon, cortisol, and dexamethasone decrease RA-induced CYP26A1 transcription, thereby reducing RA oxidation during fasting. Interaction between the glucocorticoid receptor and the RAR/RXR coactivation complex suppresses CYP26A1 expression, increasing RA's elimination half-life. Interaction between CCAAT-enhancer-binding protein beta (C/EBPβ) and the major allele of SNP rs2068888 enhances CYP26A1 expression; the minor allele restricts the C/EBPβ effect on CYP26A1. The major and minor alleles associate with impaired human health or reduction in blood triglycerides, respectively. Thus, regulating CYP26A1 transcription contributes to adapting RA to coordinate energy availability with metabolism. These results enhance insight into CYP26A1 effects on RA during changes in energy status and glucocorticoid receptor modification of RAR-regulated gene expression.

Identification of Potential Candidate Genes From Co-Expression Module Analysis During Preadipocyte Differentiation in Landrace Pig

Preadipocyte differentiation plays an important role in lipid deposition and affects fattening efficiency in pigs. In the present study, preadipocytes isolated from the subcutaneous adipose tissue of three Landrace piglets were induced into mature adipocytes in vitro. Gene clusters associated with fat deposition were investigated using RNA sequencing data at four time points during preadipocyte differentiation. Twenty-seven co-expression modules were subsequently constructed using weighted gene co-expression network analysis. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses revealed three modules (blue, magenta, and brown) as being the most critical during preadipocyte differentiation. Based on these data and our previous differentially expressed gene analysis, angiopoietin-like 4 (ANGPTL4) was identified as a key regulator of preadipocyte differentiation and lipid metabolism. After inhibition of ANGPTL4, the expression of adipogenesis-related genes was reduced, except for that of lipoprotein lipase (LPL), which was negatively regulated by ANGPTL4 during preadipocyte differentiation. Our findings provide a new perspective to understand the mechanism of fat deposition.

Ajuba functions as a co-activator of C/EBPβ to induce expression of PPARγ and C/EBPα during adipogenesis

Adipogenesis is regulated by a complicated network of transcription factors among which PPARγ and C/EBP family members are the major regulators. During adipogenesis, C/EBPβ is induced early and then transactivates PPARγ and C/EBPα, which cooperatively induce genes whose expressions give rise to the mature adipocyte phenotype. Identifying the factors that influence the expression and activity of C/EBPβ should provide additional insight into the mechanisms regulating adipogenesis. Here, we demonstrate that depletion of Ajuba in 3T3-L1 cells significantly decreases mRNA and protein levels of PPARγ and C/EBPα and impairs adipocyte differentiation, while overexpression increases expression of these genes and promotes adipocyte differentiation. Moreover, restoration of C/EBPα or PPARγ expression in Ajuba-deficient 3T3-L1 cells improves the impaired lipid accumulation. Mechanistically, Ajuba interacts with C/EBPβ and recruits CBP to facilitate the binding of C/EBPβ to the promoter of PPARγ and C/EBPα, resulting in increased H3 histone acetylation and target gene expression. Collectively, these data indicate that Ajuba functions as a co-activator of C/EBPβ, and may be an important therapeutic target for combating obesity-related diseases.

Liraglutide suppresses obesity and promotes browning of white fat via miR-27b in vivo and in vitro

Objective

To investigate the effect of liraglutide on the browning of white fat and the suppression of obesity via regulating microRNA (miR)-27b in vivo and in vitro.

Methods

Sprague-Dawley rats were fed a high-fat (HF) diet and 3T3-L1 pre-adipocytes were differentiated into mature white adipocytes. Rats and mature adipocytes were then treated with different doses of liraglutide. The mRNA and protein levels of browning-associated proteins, including uncoupling protein 1 (UCP1), PR domain containing 16 (PRDM16), CCAAT enhancer binding protein β (CEBPβ), cell death-inducing DFFA-like effector A (CIDEA) and peroxisome proliferator-activated receptor-γ-coactivator 1α (PGC-1α), were detected using quantitative real-time polymerase chain reaction and Western blotting.

Results

Liraglutide decreased body weight and reduced the levels of blood glucose, triglyceride and low-density lipoprotein cholesterol in HF diet-fed rats. Liraglutide increased the levels of UCP1, PRDM16, CEBPβ, CIDEA and PGC-1α in vivo and vitro. The levels of miR-27b were upregulated in HF diet-fed rats, whereas liraglutide reduced the levels of miR-27b. In vitro, overexpression of miR-27b decreased the mRNA and protein levels of UCP1, PRDM16, CEBPβ, CIDEA and PGC-1α. Transfection with the miR-27b mimics attenuated the effect of liraglutide on the browning of white adipocytes.

Conclusion

Liraglutide induced browning of white adipose through regulation of miR-27b.

C/EBP-α induces autophagy by binding to Beclin1 through its own acetylation modification in activated hepatic stellate cells

The activation of hepatic stellate cells (HSCs) plays a key role in the occurrence of liver fibrosis，and promoting the apoptosis of activated HSCs or reducing the number of activated HSCs can reverse the development of liver fibrosis. In our previous studies, we have demonstrated that the CCAAT/enhancer binding protein α (C/EBP-α) played an important role in promoting the apoptosis of activated HSCs, thereby exerting an anti-liver fibrosis effect. Unlike apoptosis, autophagy, as a caspase-independent programmed cell death, can promptly remove the abnormal accumulation of substances or damaged organelles in cells and play a key role in regulating the homeostasis of intracellular environment. However, it is still unclear whether C/EBP-α participates in the occurrence of autophagy in HSCs. Therefore, in this study, we firstly used the methods of Western blot and immunofluorescence to characterize the consequence of C/EBP-α overexpression on the expression of proteins LC3B, P62, ATG5 and Beclin1 which were related to autophagy in HSCs. Subsequently, we performed Western blot and site-directed mutagenesis methods to clarify the type and related mechanism of autophagy which was induced by C/EBP-α. Here we show that C/EBP-α promotes the occurrence of autophagy in HSCs and the autophagy induced by C/EBP-α belongs to mitophagy. The stability of C/EBP-α protein regulates the level of autophagy in HSCs. In addition, acetylation of C/EBP-α also regulates the occurrence of autophagy in HSCs. Acetylation of lysine at positions K298, K302 and K326 of C/EBP-α promotes its binding to Beclin1. In conclusion, our study uncovers the role of C/EBP-α in regulating autophagy in HSCs, thereby providing a new strategy for clinical treatment of liver fibrosis.

C/EBPβ is a MYB- and p300-cooperating pro-leukemogenic factor and promising drug target in acute myeloid leukemia

Transcription factor MYB has recently emerged as a promising drug target for the treatment of acute myeloid leukemia (AML). Here, we have characterized a group of natural sesquiterpene lactones (STLs), previously shown to suppress MYB activity, for their potential to decrease AML cell proliferation. Unlike what was initially thought, these compounds inhibit MYB indirectly via its cooperation partner C/EBPβ. C/EBPβ-inhibitory STLs affect the expression of a large number of MYB-regulated genes, suggesting that the cooperation of MYB and C/EBPβ broadly shapes the transcriptional program of AML cells. We show that expression of GFI1, a direct MYB target gene, is controlled cooperatively by MYB, C/EBPβ, and co-activator p300, and is down-regulated by C/EBPβ-inhibitory STLs, exemplifying that they target the activity of composite MYB-C/EBPβ-p300 transcriptional modules. Ectopic expression of GFI1, a zinc-finger protein that is required for the maintenance of hematopoietic stem and progenitor cells, partially abrogated STL-induced myelomonocytic differentiation, implicating GFI1 as a relevant target of C/EBPβ-inhibitory STLs. Overall, our data identify C/EBPβ as a pro-leukemogenic factor in AML and suggest that targeting of C/EBPβ may have therapeutic potential against AML.

SFPQ associated with a co-activator for PPARγ, HELZ2, regulates key nuclear factors for adipocyte differentiation

We recently isolated a novel co-activator of peroxisome proliferator-activated receptor γ, helicase with zinc finger 2 (HELZ2). HELZ2 null mice were resistant to diet-induced obesity and NAFFL/NASH, and HELZ2 was phosphorylated at tyrosine residues. In order to find a factor related to HELZ2, we analyzed products co-immunoprecipitated with phosphorylated HELZ2 by mass spectrometry analyses. We identified proline- and glutamine-rich (SFPQ) as a protein associating with tyrosine-phosphorylated HELZ2. The knockdown of SFPQ in 3T3-L1 cells downregulated mRNA levels of transcription factors including Krox20, Cebpβ, and Cebpδ: key factors for early-stage adipocyte differentiation. In addition, knockdown of SFPQ inhibited 3T3-L1 cell differentiation to mature adipocytes. These findings demonstrated that SFPQ associating with HELZ2 is an important novel transcriptional regulator of adipocyte differentiation.

FGF10 and Lipofibroblasts in Lung Homeostasis and Disease: Insights Gained From the Adipocytes

Adipocytes not only function as energy depots but also secrete numerous adipokines that regulate multiple metabolic processes, including lipid homeostasis. Dysregulation of lipid homeostasis, which often leads to adipocyte hypertrophy and/or ectopic lipid deposition in non-adipocyte cells such as muscle and liver, is linked to the development of insulin resistance. Similarly, an altered secretion profile of adipokines or imbalance between calorie intake and energy expenditure is associated with obesity, among other related metabolic disorders. In lungs, lipid-laden adipocyte-like cells known as lipofibroblasts share numerous developmental and functional similarities with adipocytes, and similarly influence alveolar lipid homeostasis by facilitating pulmonary surfactant production. Unsurprisingly, disruption in alveolar lipid homeostasis may propagate several chronic inflammatory disorders of the lung. Given the numerous similarities between the two cell types, dissecting the molecular mechanisms underlying adipocyte development and function will offer valuable insights that may be applied to, at least, some aspects of lipofibroblast biology in normal and diseased lungs. FGF10, a major ligand for FGFR2b, is a multifunctional growth factor that is indispensable for several biological processes, including development of various organs and tissues such as the lung and WAT. Moreover, accumulating evidence strongly implicates FGF10 in several key aspects of adipogenesis as well as lipofibroblast formation and maintenance, and as a potential player in adipocyte metabolism. This review summarizes our current understanding of the role of FGF10 in adipocytes, while attempting to derive insights on the existing literature and extrapolate the knowledge to pulmonary lipofibroblasts.

Transient Delivery of A-C/EBP Protein Perturbs Differentiation of 3T3-L1 Cells and Induces Preadipocyte Marker Genes

Transformation of committed 3T3-L1 preadipocytes to lipid-laden adipocytes involves the timely appearance of numerous transcription factors (TFs); foremost among them, C/EBPβ is expressed during the early phases of differentiation. Here, we describe liposome-mediated protein transfection approach to rapidly downregulate C/EBPβ by A-C/EBP protein inhibitor. Signals from EGFP-tagged A-C/EBP protein were observed in 3T3-L1 cells within 2 h of transfections, whereas for A-C/EBP gene transfections, equivalent signals appeared in 48 h. Following transient transfections, the expression profiles of 24 marker genes belonging to pro- and anti-adipogenic, cell cycle, and preadipocyte pathways were analyzed. Expectedly, the mRNA and protein expression profiles of adipocyte marker genes showed lower expression in both A-C/EBP protein- and gene-transfected samples. Interestingly, for preadipocytes and cell fate determinant genes, striking differences were observed between A-C/EBP protein- and A-C/EBP gene-transfected samples. Preadipocyte differentiation factors Stat5a and Creb were downregulated in A-C/EBP protein samples. Five preadipocyte markers, namely, Pdgfrα, Pdgfrβ, Ly6A, CD34, and Itgb1, showed high expression in A-C/EBP protein samples, whereas only Ly6A and CD34 were expressed in A-C/EBP gene-transfected samples. Pdgfrα and Pdgfrβ, two known cell fate markers, were expressed in A-C/EBP protein-transfected samples, suggesting a possible reversal of differentiation. Our study provides evidences for the immediate and efficient knockdown of C/EBPβ protein to understand time-dependent preadipocytes differentiation.

MLL3/MLL4-Associated PAGR1 Regulates Adipogenesis by Controlling Induction of C/EBPβ and C/EBPδ

Transcription factors C/EBPβ and C/EBPδ are induced within hours after initiation of adipogenesis in culture. They directly promote the expression of master adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and C/EBPα and are required for adipogenesis in vivo However, the mechanism that controls the induction of C/EBPβ and C/EBPδ remains elusive. We previously showed that histone methyltransferases MLL3/MLL4 and associated PTIP are required for the induction of PPARγ and C/EBPα during adipogenesis. Here, we show MLL3/MLL4/PTIP-associated protein PAGR1 (also known as PA1) cooperates with phosphorylated CREB and ligand-activated glucocorticoid receptor to directly control the induction of C/EBPβ and C/EBPδ in the early phase of adipogenesis. Deletion of Pagr1 in white and brown preadipocytes prevents the induction of C/EBPβ and C/EBPδ and leads to severe defects in adipogenesis. Adipogenesis defects in PAGR1-deficient cells can be rescued by the ectopic expression of C/EBPβ or PPARγ. Finally, the deletion of Pagr1 in Myf5⁺ precursor cells impairs brown adipose tissue and muscle development. Thus, by controlling the induction of C/EBPβ and C/EBPδ, PAGR1 plays a critical role in adipogenesis.

A human preadipocyte cell strain with multipotent differentiation capability as an in vitro model for adipogenesis

Murine 3T3 cell lines constitute a standard model system for in vitro study of mammalian adipogenesis although they do not faithfully reflect the biology of the human adipose cells. Several human adipose cell lines and strains have been used to recapitulate human adipogenesis in vitro, but to date there is no generally accepted in vitro model for human adipogenesis. We obtained a clonal strain of human subcutaneous adipose stromal cells, IPI-SA3-C4, and characterized its utility as an in vitro model for human subcutaneous adipogenesis. IPI-SA3-C4 cells showed a high proliferative potential for at least 30 serial passages, reached 70 cumulative population doublings and exhibited a population doubling time of 47 h and colony forming efficiency of 12% at the 57th cumulative population doublings. IPI-SA3-C4 cells remained diploid (46XY) even at the 56th cumulative population doublings and expressed the pluripotency markers POU5F1, NANOG, KLF4, and MYC even at 50th cumulative population doublings. Under specific culture conditions, IPI-SA3-C4 cells displayed cellular hallmarks and molecular markers of adipogenic, osteogenic, and chondrogenic lineages and showed adipogenic capacity even at the 66th cumulative population doublings. These characteristics show IPI-SA3-C4 cells as a promising potential model for human subcutaneous adipogenesis in vitro.

Serpina3c Regulates Adipogenesis by Modulating Insulin Growth Factor 1 and Integrin Signaling

Preadipocyte differentiation can be induced upon a hormonal treatment, and various factors secreted by the cells may contribute to adipogenesis. In this study, RNA-seq revealed Serpina3c as a critical factor regulating the signaling network during adipogenesis. Serpina3c is a secretory protein and is highly expressed in fat tissues. Knockdown of Serpina3c decreased adipogenesis by attenuating the mitotic clonal expansion of 3T3-L1 cells. These cells exhibited decreases in integrin α5, which abolished the phosphorylation of integrin β3. We found that Serpina3c inhibits a serine protease that regulates integrin α5 degradation. Knockdown of Serpina3c disrupted integrin-mediated insulin growth factor 1 (IGF-1) signaling and ERK activation. Serpina3c-mediated regulation of integrin-IGF-1 signaling is also associated with AKT activation, which affects the nuclear translocation of GSK3β. Altogether, our results indicate that Serpina3c secreted from differentiating adipocytes inhibits serine proteases to modulate integrin/IGF-1-mediated ERK and AKT signaling and thus is a critical factor contributing to adipogenesis.

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RNA-seq revealed Serpina3c as a critical factor regulating adipogenesis

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Knockdown of Serpina3c attenuated the mitotic clonal expansion of 3T3-L1 cells

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Knockdown of Serpina3c leads to the degradation of integrin α5

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Serpina3c regulates integrin-mediated IGF-1 signaling and ERK/AKT activation

Expression Profiles of MicroRNAs in Stem Cells Differentiation

Stem cells are undifferentiated cells and have a great potential in multilineage differentiation. These cells are classified into adult stem cells like Mesenchymal Stem Cells (MSCs) and Embryonic Stem Cells (ESCs). Stem cells also have potential therapeutic utility due to their pluripotency, self-renewal, and differentiation ability. These properties make them a suitable choice for regenerative medicine. Stem cells differentiation toward functional cells is governed by different signaling pathways and transcription factors. Recent studies have demonstrated the key role of microRNAs in the pathogenesis of various diseases, cell cycle regulation, apoptosis, aging, cell fate decisions. Several types of stem cells have different and unique miRNA expression profiles. Our review summarizes novel regulatory roles of miRNAs in the process of stem cell differentiation especially adult stem cells into a variety of functional cells through signaling pathways and transcription factors modulation. Understanding the mechanistic roles of miRNAs might be helpful in elaborating clinical therapies using stem cells and developing novel biomarkers for the early and effective diagnosis of pathologic conditions.

Red pepper seed water extract suppresses high-fat diet-induced obesity in C57BL/6 mice

In this study, the protective effect of red pepper seed water extract (RPS) against the obesity in high fat diet (HFD)-fed mice was investigated (HFD control group, and HFD group treated with 100 or 200 mg/kg body weight of RPS for 13 weeks). The application of RPS partially reversed the HFD-induced increases in body weight and adipose tissue weight. The patterns of the adipose tissue weights were parallel to the patterns of fat area, as measured in DXA procedure. In the adipose tissue, RPS suppressed the expression of adipogenic transcription factors and adipose marker genes. AMP-activated protein kinase activation was observed in the adipose tissue by RPS treatment. In addition, RPS improved high homeostasis model assessment of insulin resistance and hyperlipidemia in HFD fed mice. These findings suggest that RPS can be used as a potential therapeutic substance for reducing body fat and obesity related diseases.

Hyperglycemia Changes Expression of Key Adipogenesis Markers (C/EBPα and PPARᵞ)and Morphology of Differentiating Human Visceral Adipocytes

Disturbances in adipose tissue significantly contribute to the development of metabolic disorders, which are connected with hyperglycemia (HG) and underlain by epigenetics-based mechanisms. Therefore, we aimed to evaluate the effect of hyperglycemia on proliferating, differentiating and maturating human visceral pre/adipocytes (HPA-v). Three stages of cell culture were conducted under constant or variable glycemic conditions. Adipogenesis progress was assessed using BODIPY 505/515 staining. Lipid content typical for normal and hyperglycemic conditions of adipocytes was analyzed using Raman spectroscopy and imaging. Expression of adipogenic markers, PPARγ and C/EBPα, was determined at the mRNA and protein levels. We also examined expression of miRNAs proven to target PPARγ (miR-34a-5p) and C/EBPα (miR-137-3p), employing TaqMan Low-Density Arrays (TLDA) cards. Hyperglycemia altered morphology of differentiating HPA-v in relation to normoglycemia by accelerating the formation of lipid droplets and making their numbers and volume increase. Raman results confirmed that the qualitative and quantitative lipid composition under normal and hyperglycemic conditions were different, and that the number of lipid droplets increased in (HG)-treated cells. Expression profiles of both examined genes markedly changed either during adipogenesis under physiological and hyperglycemic conditions, orat particular stages of adipogenesis upon chronic and/or variable glycemia. Expression levels of PPARγ seemed to correspond to some expression changes of miR-34a-5p. miR-137-3p, whose expression was rather stable throughout the culture, did not seem to affect C/EBPα. Our observations revealed that chronic and intermittent hyperglycemia change the morphology of visceral pre/adipocytes during adipogenesis. Moreover, hyperglycemia may utilize miR-34a-5p to induce some expression changes in PPARγ.

GDF10 blocks hepatic PPARγ activation to protect against diet-induced liver injury

OBJECTIVE

Growth differentiation factors (GDFs) and bone-morphogenic proteins (BMPs) are members of the transforming growth factor β (TGFβ) superfamily and are known to play a central role in the growth and differentiation of developing tissues. Accumulating evidence, however, demonstrates that many of these factors, such as BMP-2 and -4, as well as GDF15, also regulate lipid metabolism. GDF10 is a divergent member of the TGFβ superfamily with a unique structure and is abundantly expressed in brain and adipose tissue; it is also secreted by the latter into the circulation. Although previous studies have demonstrated that overexpression of GDF10 reduces adiposity in mice, the role of circulating GDF10 on other tissues known to regulate lipid, like the liver, has not yet been examined.

METHODS

Accordingly, GDF10^-/- mice and age-matched GDF10^+/+ control mice were fed either normal control diet (NCD) or high-fat diet (HFD) for 12 weeks and examined for changes in liver lipid homeostasis. Additional studies were also carried out in primary and immortalized human hepatocytes treated with recombinant human (rh)GDF10.

RESULTS

Here, we show that circulating GDF10 levels are increased in conditions of diet-induced hepatic steatosis and, in turn, that secreted GDF10 can prevent excessive lipid accumulation in hepatocytes. We also report that GDF10^-/- mice develop an obese phenotype as well as increased liver triglyceride accumulation when fed a NCD. Furthermore, HFD-fed GDF10^-/- mice develop increased steatosis, endoplasmic reticulum (ER) stress, fibrosis, and injury of the liver compared to HFD-fed GDF10^+/+ mice. To explain these observations, studies in cultured hepatocytes led to the observation that GDF10 attenuates nuclear peroxisome proliferator-activated receptor γ (PPARγ) activity; a transcription factor known to induce de novo lipogenesis.

CONCLUSION

Our work delineates a hepatoprotective role of GDF10 as an adipokine capable of regulating hepatic lipid levels by blocking de novo lipogenesis to protect against ER stress and liver injury.

Effect of Lippia alba essential oil administration on obesity and T2DM markers in Wistar rats

Introduction: Lippia alba (Mill) N.E. Brown (Verbenaceae) is an aromatic plant from Central America, South America, and the Caribbean, it is traditionally used by the Colombian population to treat various diseases such as diabetes and hypertension. The purpose of this research was to evaluate the metabolic effects of Lippia alba essential oil (EO) oral administration on obesity and diabetes markers in Wistar rats. Methods: control and Streptozotocin (STZ) diabetes induced rats were used to evaluate the EO metabolic effects. Glucose and triglycerides were measured using commercial colorimetric kits, the animals’ weight was followed for 21 days treatment and TNF- and adiponectin concentration was determined with ELISA technique. Results: The consumption of EO shows body weight gain regulation, lower glucose and cholesterol levels in normal rats and lower TNF- in comparison with the Glibenclamide treated rats between the STZ diabetic groups. No toxic effects were founded. Conclusions: The EO exerts a benefical metabolic effect in rats, therefore it is interesting to be evaluate a future in human beings with T2DM or overweight.

Genetic association of DDIT3, RPL23A, SESN2 and NR4A1 genes with milk yield and composition in dairy cattle

Previously, we identified by RNA sequencing that DDIT3, RPL23A, SESN2 and NR4A1 genes were significantly differentially expressed between the mammary glands of lactating Holstein cows with extremely high and low milk protein and fat percentages; thus, these four genes are considered as promising candidates potentially affecting milk yield and composition traits in dairy cattle. In the present study, we further verified whether these genes have genetic effects on milk traits in a Chinese Holstein population. By re-sequencing part of the non-coding and the entire coding regions of the DDIT3, RPL23A, SESN2 and NR4A1 genes, a total of 35 SNPs and three insertions/deletions were identified, of which three were found in DDIT3, 12 in RPL23A, 16 in SESN2 and seven in NR4A1. Moreover, two of the insertions/deletions-g.125714860_125714872del and g.125714806delinsCCCC in SESN2-were novel and have not been reported previously. Subsequent single SNP analyses revealed multiple significant association with all 35 SNPs and three indels regressed against the dairy production traits (P-value = <0.0001-0.0493). In addition, with a linkage disequilibrium analysis, we found one, one, three, and one haplotype blocks in the DDIT3, RPL23A, SESN2 and NR4A1 genes respectively. Haplotype-based association analyses revealed that some haplotypes were also significantly associated with milk production traits (P-value = <0.0001-0.0461). We also found that 12 SNPs and two indels (two in DDIT3, two in RPL23A, nine in SESN2 and one in NR4A1) altered the specific transcription factor binding sites in the promoter, thereby regulating promoter activity, suggesting that they might be promising potential functional variants for milk traits. In summary, our findings first determined the genetic associations of DDIT3, RPL23A, SESN2 and NR4A1 with milk yield and composition traits in dairy cattle and also suggested potentially causal variants, which require in-depth validation.

Mechanisms of Impaired Brown Adipose Tissue Recruitment in Obesity

Brown adipose tissue (BAT) dissipates energy to produce heat. Thus, it has the potential to regulate body temperature by thermogenesis. For the last decade, BAT has been in the spotlight due to its rediscovery in adult humans. This is evidenced by over a hundred clinical trials that are currently registered to target BAT as a therapeutic tool in the treatment of metabolic diseases, such as obesity or diabetes. The goal of most of these trials is to activate the BAT thermogenic program via several approaches such as adrenergic stimulation, natriuretic peptides, retinoids, capsinoids, thyroid hormones, or glucocorticoids. However, the impact of BAT activation on total body energy consumption and the potential effect on weight loss is still limited. Other studies have focused on increasing the mass of thermogenic BAT. This can be relevant in obesity, where the activity and abundance of BAT have been shown to be drastically reduced. The aim of this review is to describe pathological processes associated with obesity that may influence the correct differentiation of BAT, such as catecholamine resistance, inflammation, oxidative stress, and endoplasmic reticulum stress. This will shed light on the thermogenic potential of BAT as a therapeutic approach to target obesity-induced metabolic diseases.

Adenanthin, a Natural ent-Kaurane Diterpenoid Isolated from the Herb Isodon adenantha Inhibits Adipogenesis and the Development of Obesity by Regulation of ROS

Adenanthin, a natural ent-kaurane diterpenoid extracted from the herb Isodon adenantha, has been reported to increase intracellular reactive oxygen species in leukemic and hepatocellular carcinoma cells. However, the function and mechanism of the compound in adipogenesis and the development of obesity is still unknown. In this study, we demonstrated that adenanthin inhibited adipogenesis of 3T3-L1 and mouse embryonic fibroblasts, and the underlying mechanism included two processes: a delayed mitotic clonal expansion via G0/G1 cell cycle arrest by inhibiting the RB-E2F1 signaling pathway and a reduced C/EBPβ signaling by inhibiting the expression and activity of C/EBPβ during mitotic clonal expansion. Furthermore, adenanthin significantly reduced the growing body weight and adipose tissue mass during high-fat diet-inducing obesity of mice, indicating the beneficial effects of adenanthin as a potential agent for prevention of obesity.

Connecting homocysteine and obesity through pyroptosis, gut microbiome, epigenetics, peroxisome proliferator-activated receptor γ, and zinc finger protein 407

Although homocysteine (Hcy), a part of the epigenome, contributes to cell death by pyroptosis and decreases peroxisome proliferator-activated receptor γ (PPARγ) levels, the mechanisms are unclear. Hcy is found in high concentrations in the sera of obese individuals, which can elicit an immune response as well by hypermethylating CpG islands of specific gene promoters, a marker of epigenetics. Hcy has also been established to chelate divalent metal ions like Cu²⁺ and Zn²⁺, but this role of Hcy has not been established in relationship with obesity. It has been known for a while that PPARγ dysregulation results in various metabolic disorders including glucose and lipid metabolism. Recently, zinc finger protein 407 (Zfp407) is reported to regulate PPARγ target gene expression without affecting PPARγ transcript and protein levels by synergistically working with PPARγ. However, the mechanism(s) of this synergy, as well as other factors contributing to or inhibiting this synergism, have not been proven. This review suggests that Hcy contributes to pyroptosis, changes gut microbiome, and alters PPARγ-dependent mechanism(s) via Zfp407-mediated upregulated adipogenesis and misbalanced fatty acid metabolism, which can predispose to obesity and, consequently, obesity-related metabolic disorders.

Citrus aurantium L. dry extracts promote C/ebpβ expression and improve adipocyte differentiation in 3T3-L1 cells

Metabolic and/or endocrine dysfunction of the white adipose tissue (WAT) contribute to the development of metabolic disorders, such as Type 2 Diabetes (T2D). Therefore, the identification of products able to improve adipose tissue function represents a valuable strategy for the prevention and/or treatment of T2D. In the current study, we investigated the potential effects of dry extracts obtained from Citrus aurantium L. fruit juice (CAde) on the regulation of 3T3-L1 cells adipocyte differentiation and function in vitro. We found that CAde enhances terminal adipocyte differentiation of 3T3-L1 cells raising the expression of CCAAT/enhancer binding protein beta (C/Ebpβ), peroxisome proliferator activated receptor gamma (Pparγ), glucose transporter type 4 (Glut4) and fatty acid binding protein 4 (Fabp4). CAde improves insulin-induced glucose uptake of 3T3-L1 adipocytes, as well. A focused analysis of the phases occurring in the pre-adipocytes differentiation to mature adipocytes furthermore revealed that CAde promotes the early differentiation stage by up-regulating C/ebpβ expression at 2, 4 and 8 h post the adipogenic induction and anticipating the 3T3-L1 cell cycle entry and progression during mitotic clonal expansion (MCE). These findings provide evidence that the exposure to CAde enhances in vitro fat cell differentiation of pre-adipocytes and functional capacity of mature adipocytes, and pave the way to the development of products derived from Citrus aurantium L. fruit juice, which may improve WAT functional capacity and may be effective for the prevention and/or treatment of T2D.

Screening of potential anti-adipogenic effects of phenolic compounds showing different chemical structure in 3T3-L1 preadipocytes

This study was designed to analyze the anti-adipogenic effect of fifteen phenolic compounds from various chemical groups in 3T3-L1 pre-adipocytes. Cells were treated with 25 μM, 10 μM or 1 μM of apigenin, luteolin, catechin, epicatechin, epigallocatechin, genistein, daizein, naringenin, hesperidin, quercetin, kaempferol, resveratrol, vanillic acid, piceatannol and pterostilbene for 8 days. At 25 μM lipid accumulation was reduced by all the compounds, with the exception of catechin, epicatechin and epigallocatechin. At a dose of 10 μM apigenin, luteolin, naringenin, hesperidin, quercetin and kaempferol induced significant reductions, and at 1 μM only naringenin, hesperidin and quercetin were effective. The expression of c/ebpα was not. C/ebpβ was significantly reduced by genistein and kaempferol, pparγ by genistein and pterostilbene, srebp1c by luteolin, genistein, hesperidin, kaempferol, pterostilbene and vanillic acid, and lpl by kaempferol. In conclusion, the most effective phenolic compounds are naringenin, hesperidin and quercetin. Differences were found in terms of effects on the expression of genes involved in adipogenesis among the analyzed compounds.

Light-Activatable Red Blood Cell Membrane-Camouflaged Dimeric Prodrug Nanoparticles for Synergistic Photodynamic/Chemotherapy

Biomimetic approach offers numerous opportunities to design therapeutic platforms with enhanced antitumor performance and biocompatibility. Herein we report red blood cell membrane-camouflaged nanoparticles (RBC(M(TPC-PTX))) for synergistic chemo- and photodynamic therapy (PDT). Specifically, the inner core is mainly constructed by reactive oxygen species (ROS)-responsive PTX dimer (PTX₂-TK) and photosensitizer 5,10,15,20-tetraphenylchlorin (TPC). In vitro experiments show that the prepared RBC(M(TPC-PTX)) is readily taken up into endosomes. Under appropriate light irradiation, the TPC can generate ROS, not only for PDT but also for triggering PTX₂-TK cleavage and on-demand PTX release for chemotherapy. In vivo results show that the coating of RBC membrane prolongs blood circulation and improves tumor accumulation. The combination of chemo- and photodynamic therapy enhances anticancer therapeutic activity, and light-triggered drug release reduces systematic toxicity. All these characteristics render the described technology extremely promising for cancer treatment.

The natural anti-tumor compound Celastrol targets a Myb-C/EBPβ-p300 transcriptional module implicated in myeloid gene expression

Myb is a key regulator of hematopoietic progenitor cell proliferation and differentiation and has emerged as a potential target for the treatment of acute leukemia. Using a myeloid cell line with a stably integrated Myb-inducible reporter gene as a screening tool we have previously identified Celastrol, a natural compound with anti-tumor activity, as a potent Myb inhibitor that disrupts the interaction of Myb with the co-activator p300. We showed that Celastrol inhibits the proliferation of acute myeloid leukemia (AML) cells and prolongs the survival of mice in an in vivo model of AML, demonstrating that targeting Myb with a small-molecule inhibitor is feasible and might have potential as a therapeutic approach against AML. Recently we became aware that the reporter system used for Myb inhibitor screening also responds to inhibition of C/EBPβ, a transcription factor known to cooperate with Myb in myeloid cells. By re-investigating the inhibitory potential of Celastrol we have found that Celastrol also strongly inhibits the activity of C/EBPβ by disrupting its interaction with the Taz2 domain of p300. Together with previous studies our work reveals that Celastrol independently targets Myb and C/EBPβ by disrupting the interaction of both transcription factors with p300. Myb, C/EBPβ and p300 cooperate in myeloid-specific gene expression and, as shown recently, are associated with so-called super-enhancers in AML cells that have been implicated in the maintenance of the leukemia. We hypothesize that the ability of Celastrol to disrupt the activity of a transcriptional Myb-C/EBPβ-p300 module might explain its promising anti-leukemic activity.

Red Pepper Seed Inhibits Differentiation of 3T3-L1 Cells during the Early Phase of Adipogenesis via the Activation of AMPK

Obesity is the main risk factor for metabolic syndromes and there has been an upsurge in demand for effective therapeutic strategies. This study investigated the effect of red pepper seed water extract (RPS) on the process of differentiation in 3T3-L1 adipocytes. RPS treatment significantly suppressed cellular lipid accumulation and reduced the expression of adipocytes-associated proteins, peroxisome proliferator-activated receptor-[Formula: see text] (PPAR-[Formula: see text]), CCAAT/enhancer-binding proteins [Formula: see text] (C/EBP [Formula: see text]), sterol regulatory element binding protein-1c (SREBP-1c), as well as fatty acid synthase (FAS), and fatty acid binding protein 4 (FABP4). The inhibitory effect of RPS on differentiation was mainly through the modulation of the C/EBP [Formula: see text] and C/EBP [Formula: see text] expression at the early phase of differentiation. Moreover, at the early phase of differentiation, RPS markedly increased the phosphorylation of AMP-activated protein kinase (AMPK). Such enhancing effect of RPS was abolished in the presence of compound C. Our results suggest that activation of AMPK at early stage of adipogenesis is involved in the anti-adipogenesis effect of RPS.

Bee Venom Suppresses the Differentiation of Preadipocytes and High Fat Diet-Induced Obesity by Inhibiting Adipogenesis

Bee venom (BV) has been widely used in the treatment of certain immune-related diseases. It has been used for pain relief and in the treatment of chronic inflammatory diseases. Despite its extensive use, there is little documented evidence to demonstrate its medicinal utility against obesity. In this study, we demonstrated the inhibitory effects of BV on adipocyte differentiation in 3T3-L1 cells and on a high fat diet (HFD)-induced obesity mouse model through the inhibition of adipogenesis. BV inhibited lipid accumulation, visualized by Oil Red O staining, without cytotoxicity in the 3T3-L1 cells. Male C57BL/6 mice were fed either a HFD or a control diet for 8 weeks, and BV (0.1 mg/kg or 1 mg/kg) or saline was injected during the last 4 weeks. BV-treated mice showed a reduced body weight gain. BV was shown to inhibit adipogenesis by downregulating the expression of the transcription factors CCAAT/enhancer-binding proteins (C/EBPs) and the peroxisome proliferator-activated receptor gamma (PPARγ), using RT-qPCR and Western blotting. BV induced the phosphorylation of AMP-activated kinase (AMPK) and acetyl-CoA carboxylase (ACC) in the cell line and in obese mice. These findings demonstrate that BV mediates anti-obesity/differentiation effects by suppressing obesity-related transcription factors.

Itm2a silencing rescues lamin A mediated inhibition of 3T3-L1 adipocyte differentiation

Dysregulation of adipose tissue metabolism is associated with multiple metabolic disorders. One such disease, known as Dunnigan-type familial partial lipodystrophy (FPLD2) is characterized by defective fat metabolism and storage. FPLD2 is caused by a specific subset of mutations in the LMNA gene. The mechanisms by which LMNA mutations lead to the adipose specific FPLD2 phenotype have yet to be determined in detail. We used RNA-Seq analysis to assess the effects of wild-type (WT) and mutant (R482W) lamin A on the expression profile of differentiating 3T3-L1 mouse preadipocytes and identified Itm2a as a gene that was upregulated at 36 h post differentiation induction in these cells. In this study we identify Itm2a as a novel modulator of adipogenesis and show that endogenous Itm2a expression is transiently downregulated during induction of 3T3-L1 differentiation. Itm2a overexpression was seen to moderately inhibit differentiation of 3T3-L1 preadipocytes while shRNA mediated knockdown of Itm2a significantly enhanced 3T3-L1 differentiation. Investigation of PPARγ levels indicate that this enhanced adipogenesis is mediated through the stabilization of the PPARγ protein at specific time points during differentiation. Finally, we demonstrate that Itm2a knockdown is sufficient to rescue the inhibitory effects of lamin A WT and R482W mutant overexpression on 3T3-L1 differentiation. This suggests that targeting of Itm2a or its related pathways, including autophagy, may have potential as a therapy for FPLD2.

TSA increases C/EBP‑α expression by increasing its lysine acetylation in hepatic stellate cells

CCAAT enhancer binding protein‑α (C/EBP‑α) is a transcription factor expressed only in certain tissues, including the liver. It has been previously demonstrated that C/EBP‑α may induce apoptosis in hepatic stellate cells (HSCs), raising the question of whether acetylation of C/EBP‑α is associated with HSCs, and the potential associated mechanism. A total of three histone deacetylase inhibitors (HDACIs), including trichostatin A (TSA), suberoylanilide hydroxamic acid and nicotinamide, were selected to determine whether acetylation affects C/EBP‑α expression. A Cell Counting Kit‑8 assay was used to determine the rate of proliferation inhibition following treatment with varying doses of the three HDACIs in HSC‑T6 and BRL‑3A cells. Western blot analysis was used to examine Caspase‑3, ‑8, ‑9, and ‑12 levels in HSC‑T6 cells treated with adenoviral‑C/EBP‑α and/or TSA. Following treatment with TSA, a combination of reverse transcription‑quantitative polymerase chain reaction and western blot analyses was used to determine the inherent C/EBP‑α mRNA and protein levels in HSC‑T6 cells at 0, 1, 2, 4, 8, 12, 24, 36 and 48 h. Nuclear and cytoplasmic proteins were extracted to examine C/EBP‑α distribution. Co‑immunoprecipitation analysis was used to examine the lysine acetylation of C/EBP‑α. It was observed that TSA inhibited the proliferation of HSC‑T6 cells to a greater extent compared with BRL‑3A cells, following treatment with the three HDACIs. TSA induced apoptosis in HSC‑T6 cells and enhanced the expression of C/EBP‑α. Following treatment of HSC‑T6 cells with TSA, inherent C/EBP‑α expression increased in a time‑dependent manner, and its lysine acetylation simultaneously increased. Therefore, the results of the present study suggested that TSA may increase C/EBP‑α expression by increasing its lysine acetylation in HSCs.

Withaferin A, a natural compound with anti-tumor activity, is a potent inhibitor of transcription factor C/EBPβ

Recent work has shown that deregulation of the transcription factor Myb contributes to the development of leukemia and several other human cancers, making Myb and its cooperation partners attractive targets for drug development. By employing a myeloid Myb-reporter cell line we have identified Withaferin A (WFA), a natural compound that exhibits anti-tumor activities, as an inhibitor of Myb-dependent transcription. Analysis of the inhibitory mechanism of WFA showed that WFA is a significantly more potent inhibitor of C/EBPβ, a transcription factor cooperating with Myb in myeloid cells, than of Myb itself. We show that WFA covalently modifies specific cysteine residues of C/EBPβ, resulting in the disruption of the interaction of C/EBPβ with the co-activator p300. Our work identifies C/EBPβ as a novel direct target of WFA and highlights the role of p300 as a crucial co-activator of C/EBPβ. The finding that WFA is a potent inhibitor of C/EBPβ suggests that inhibition of C/EBPβ might contribute to the biological activities of WFA.

Comparative Transcriptomic and Epigenomic Analyses Reveal New Regulators of Murine Brown Adipogenesis

Increasing energy expenditure through brown adipocyte recruitment is a promising approach to combat obesity. We report here the comprehensive profiling of the epigenome and transcriptome throughout the lineage commitment and differentiation of C3H10T1/2 mesenchymal stem cell line into brown adipocytes. Through direct comparison to datasets from differentiating white adipocytes, we systematically identify stage- and lineage-specific coding genes, lncRNAs and microRNAs. Utilizing chromatin state maps, we also define stage- and lineage-specific enhancers, including super-enhancers, and their associated transcription factor binding motifs and genes. Through these analyses, we found that in brown adipocytes, brown lineage-specific genes are pre-marked by both H3K4me1 and H3K27me3, and the removal of H3K27me3 at the late stage is necessary but not sufficient to promote brown gene expression, while the pre-deposition of H3K4me1 plays an essential role in poising the brown genes for expression in mature brown cells. Moreover, we identify SOX13 as part of a p38 MAPK dependent transcriptional response mediating early brown cell lineage commitment. We also identify and subsequently validate PIM1, SIX1 and RREB1 as novel regulators promoting brown adipogenesis. Finally, we show that SIX1 binds to adipogenic and brown marker genes and interacts with C/EBPα, C/EBPβ and EBF2, suggesting their functional cooperation during adipogenesis.

Caffeine inhibits adipogenesis through modulation of mitotic clonal expansion and the AKT/GSK3 pathway in 3T3-L1 adipocytes

Caffeine has been proposed to have several beneficial effects on obesity and its related metabolic diseases; however, how caffeine affects adipocyte differentiation has not been elucidated. In this study, we demonstrated that caffeine suppressed 3T3-L1 adipocyte differentiation and inhibited the expression of CCAAT/enhancer binding protein (C/EBP)α and peroxisome proliferator-activated receptor (PPAR)γ, two main adipogenic transcription factors. Anti-adipogenic markers, such as preadipocyte secreted factor (Pref)-1 and Krüppel-like factor 2, remained to be expressed in the presence of caffeine. Furthermore, 3T3-L1 cells failed to undergo typical mitotic clonal expansion in the presence of caffeine. Investigation of hormonal signaling revealed that caffeine inhibited the activation of AKT and glycogen synthase kinase (GSK) 3 in a dose-dependent manner, but not extracellular signal-regulated kinase (ERK). Our data show that caffeine is an anti-adipogenic bioactive compound involved in the modulation of mitotic clonal expansion during adipocyte differentiation through the AKT/GSK3 pathway. [BMB Reports 2016; 49(2): 111-115]

Helenalin Acetate, a Natural Sesquiterpene Lactone with Anti-inflammatory and Anti-cancer Activity, Disrupts the Cooperation of CCAAT Box/Enhancer-binding Protein β (C/EBPβ) and Co-activator p300

Recent work has demonstrated pro-oncogenic functions of the transcription factor CCAAT box/enhancer-binding protein β (C/EBPβ) in various tumors, implicating C/EBPβ as an interesting target for the development of small-molecule inhibitors. We have previously discovered that the sesquiterpene lactone helenalin acetate, a natural compound known to inhibit NF-κB, is a potent C/EBPβ inhibitor. We have now examined the inhibitory mechanism of helenalin acetate in more detail. We demonstrate that helenalin acetate is a significantly more potent inhibitor of C/EBPβ than of NF-κB. Our work shows that helenalin acetate inhibits C/EBPβ by binding to the N-terminal part of C/EBPβ, thereby disrupting the cooperation of C/EBPβ with the co-activator p300. C/EBPβ is expressed in several isoforms from alternative translational start codons. We have previously demonstrated that helenalin acetate selectively inhibits only the full-length (liver-enriched activating protein* (LAP*)) isoform but not the slightly shorter (LAP) isoform. Consistent with this, helenalin acetate binds to the LAP* but not to the LAP isoform, explaining why its inhibitory activity is selective for LAP*. Although helenalin acetate contains reactive groups that are able to interact covalently with cysteine residues, as exemplified by its effect on NF-κB, the inhibition of C/EBPβ by helenalin acetate is not due to irreversible reaction with cysteine residues of C/EBPβ. In summary, helenalin acetate is the first highly active small-molecule C/EBPβ inhibitor that inhibits C/EBPβ by a direct binding mechanism. Its selectivity for the LAP* isoform also makes helenalin acetate an interesting tool to dissect the functions of the LAP* and LAP isoforms.

C/EBP β mRNA expression is upregulated and positively correlated with the expression of TNIP1/TNFAIP3 in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

CCAAT/enhancer-binding protein β (C/EBP β) has important roles in numerous signaling pathways. The expression of the majority of regulators and target gene products of C/EBP β, including tumor necrosis factor α-induced protein 3 (TNFAIP3) and TNFAIP3-interacting protein 1 (TNIP1), are upregulated in patients with systemic lupus erythematosus (SLE). The aim of the present study was to investigate whether C/EBP β expression is associated with SLE pathogenesis and correlates with TNIP1 and TNFAIP3 expression. Quantitative reverse transcription-polymerase chain reaction analysis was used to assess the expression of C/EBP β, TNIP1, and TNFAIP3 mRNA in peripheral blood mononuclear cells (PBMC) from 20 patients with SLE and 20 healthy controls. Spearman's rank test was used to determine the correlation between C/EBP β expression and SLE disease activity, and that between C/EBP β expression and TNIP1/TNFAIP3 expression in PBMCs from patients with SLE. C/EBP β mRNA expression was markedly increased in patients with SLE compared with healthy controls. The expression of C/EBP β was positively correlated with the SLE disease activity index and negatively correlated with the serum level of complement components C3 and C4. In addition, C/EBP β mRNA expression was increased in PBMCs from SLE patients that were positive for antinuclear, anti-Smith and anti-nRNP antibodies, compared with the antibody negative SLE patients. Furthermore, the mRNA expression levels of C/EBP β in patients with SLE was positively correlated with TNIP1 and TNFAIP3 expression. The results of the current study suggest that the increased expression of C/EBP β in PBMCs and the interaction between C/EBP β and TNIP1/TNFAIP3 may be involved in the pathogenesis of SLE.

Upregulation of the C/EBP β LAP isoform could be due to decreased TNFAIP3/TNIP1 expression in the peripheral blood mononuclear cells of patients with systemic lupus erythematosus

OBJECTIVES

We aimed to examine CCAAT/enhancer-binding protein β (C/EBP β), TNF-alpha-induced protein 3 (TNFAIP3), and TNFAIP3-interacting protein 1 (TNIP1) expression in peripheral blood mononuclear cells (PBMCs) of systemic lupus erythematosus (SLE) patients to assess their relationship in SLE pathogenesis.

METHODS

C/EBP β, TNIP1, and TNFAIP3 expression was assessed in PBMCs from 20 SLE patients and 20 controls by western blotting. The correlation between C/EBP β/TNFAIP3/TNIP1 expression and SLE disease activity was determined by Spearman's rank. C/EBP β, TNIP1, and TNFAIP3 levels in THP-1 cells, THP-1 cells transfected with plasmids encoding TNFAIP3 shRNA, and THP-1 cells infected with lentiviral vectors encoding TNIP1 shRNA were assessed by western blotting.

RESULTS

C/EBP β LAP isoform expression was increased and LIP/TNFAIP3/TNIP1 expression was decreased in SLE patients. LAP expression was positively correlated with SLE disease activity; TNFAIP3 and TNIP1 expression was negatively correlated with SLE disease activity. LAP expression was increased in SLE patients with proteinuria and elevated anti-dsDNA antibody, as well as in THP-1 cells transfected with plasmids encoding TNFAIP3 shRNA and THP-1 cells infected with lentiviral vectors encoding TNIP1 shRNA.

CONCLUSIONS

C/EBP β/TNFAIP3/TNIP1 is associated with SLE activity. The upregulated expression of C/EBP β LAP could be caused by reduced TNFAIP3/TNIP1 expression.

Shp2 suppresses the adipogenic differentiation of preadipocyte 3T3-L1 cells at an early stage

Tyrosine phosphatase protein Shp2 is a potential therapeutic target for obesity. However, the mechanism of Shp2 during adipogenesis is not fully understood. The present study investigated the role of Shp2 in the terminal differentiation of preadipocytes. The results showed that Shp2 suppressed adipocyte differentiation in 3T3-L1 cells; overexpression of Shp2 reduced lipid droplet production in 3T3-L1 cells, whereas Shp2 knockdown increased lipid droplet production in 3T3-L1 cells. Furthermore, inhibition of Shp2 activity also enhanced adipocyte differentiation. Interestingly, Shp2 expression was specifically decreased early during differentiation in response to stimulation with the dexamethasone–methylisobutylxanthine–insulin (DMI) hormone cocktail. During the first 2 days of differentiation, Shp2 overexpression impaired the DMI-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) in 3T3-L1 cells and blocked the peak expression of CCAAT/enhancer-binding proteins β and δ during preadipocyte differentiation. In conclusion, Shp2 downregulated the early stages of hormone-induced differentiation of 3T3-L1 cells and inhibited the expression of the first wave of transcription factors by suppressing the DMI-induced STAT3 signaling pathway. These discoveries point to a novel role of Shp2 during adipogenesis and support the hypothesis that Shp2 could be a therapeutic target for the control of obesity.

Dexras1 links glucocorticoids to insulin-like growth factor-1 signaling in adipogenesis

Glucocorticoids are associated with obesity, but the underlying mechanism by which they function remains poorly understood. Previously, we showed that small G protein Dexras1 is expressed by glucocorticoids and leads to adipocyte differentiation. In this study, we explored the mechanism by which Dexras1 mediates adipogenesis and show a link to the insulin-like growth factor-1 (IGF-1) signaling pathway. Without Dexras1, the activation of MAPK and subsequent phosphorylation of CCAAT/enhancer binding protein β (C/EBPβ) is abolished, thereby inhibiting mitotic clonal expansion and further adipocyte differentiation. Dexras1 translocates to the plasma membrane upon insulin or IGF-1 treatment, for which the unique C-terminal domain (amino acids 223–276) is essential. Dexras1-dependent MAPK activation is selectively involved in the IGF-1 signaling, because another Ras protein, H-ras localized to the plasma membrane independently of insulin treatment. Moreover, neither epidermal growth factor nor other cell types shows Dexras1-dependent MAPK activation, indicating the importance of Dexras1 in IGF-1 signaling in adipogenesis. Dexras1 interacts with Shc and Raf, indicating that Dexras1-induced activation of MAPK is largely dependent on the Shc-Grb2-Raf complex. These results suggest that Dexras1 is a critical mediator of the IGF-1 signal to activate MAPK, linking glucocorticoid signaling to IGF-1 signaling in adipogenesis.

Processed Panax ginseng, sun ginseng, inhibits the differentiation and proliferation of 3T3-L1 preadipocytes and fat accumulation in Caenorhabditis elegans

Background

Heat-processed ginseng, sun ginseng (SG), has been reported to have improved therapeutic properties compared with raw forms, such as increased antidiabetic, anti-inflammatory, and antihyperglycemic effects. The aim of this study was to investigate the antiobesity effects of SG through the suppression of cell differentiation and proliferation of mouse 3T3-L1 preadipocyte cells and the lipid accumulation in Caenorhabditis elegans.

Methods

To investigate the effect of SG on adipocyte differentiation, levels of stained intracellular lipid droplets were quantified by measuring the oil red O signal in the lipid extracts of cells on differentiation Day 7. To study the effect of SG on fat accumulation in C. elegans, L4 stage worms were cultured on an Escherichia coli OP50 diet supplemented with 10 μg/mL of SG, followed by Nile red staining. To determine the effect of SG on gene expression of lipid and glucose metabolism-regulation molecules, messenger RNA (mRNA) levels of genes were analyzed by real-time reverse transcription-polymerase chain reaction analysis. In addition, the phosphorylation of Akt was examined by Western blotting.

Results

SG suppressed the differentiation of 3T3-L1 cells stimulated by a mixture of 3-isobutyl-1-methylxanthine, dexamethasone, and insulin (MDI), and inhibited the proliferation of adipocytes during differentiation. Treatment of C. elegans with SG showed reductions in lipid accumulation by Nile red staining, thus directly demonstrating an antiobesity effect for SG. Furthermore, SG treatment downregulated mRNA and protein expression levels of peroxisome proliferator-activated receptor subtype γ (PPARγ) and CCAAT/enhancer-binding protein-alpha (C/EBPα) and decreased the mRNA level of sterol regulatory element-binding protein 1c in MDI-treated adipocytes in a dose-dependent manner. In differentiated 3T3-L1 cells, mRNA expression levels of lipid metabolism-regulating factors, such as amplifying mouse fatty acid-binding protein 2, leptin, lipoprotein lipase, fatty acid transporter protein 1, fatty acid synthase, and 3-hydroxy-3-methylglutaryl coenzyme A reductase, were increased, whereas that of the lipolytic enzyme carnitine palmitoyltransferase-1 was decreased. Our data demonstrate that SG inversely regulated the expression of these genes in differentiated adipocytes. SG induced increases in the mRNA expression of glycolytic enzymes such as glucokinase and pyruvate kinase, and a decrease in the mRNA level of the glycogenic enzyme phosphoenol pyruvate carboxylase. In addition, mRNA levels of the glucose transporters GLUT1, GLUT4, and insulin receptor substrate-1 were elevated by MDI stimulation, whereas SG dose-dependently inhibited the expression of these genes in differentiated adipocytes. SG also inhibited the phosphorylation of Akt (Ser473) at an early phase of MDI stimulation. Intracellular nitric oxide (NO) production and endothelial nitric oxide synthase mRNA levels were markedly decreased by MDI stimulation and recovered by SG treatment of adipocytes.

Conclusion

Our results suggest that SG effectively inhibits adipocyte proliferation and differentiation through the downregulation of PPARγ and C/EBPα, by suppressing Akt (Ser473) phosphorylation and enhancing NO production. These results provide strong evidence to support the development of SG for antiobesity treatment.

Blockade of Sphingosine 1-Phosphate Receptor 2 Signaling Attenuates High-Fat Diet-Induced Adipocyte Hypertrophy and Systemic Glucose Intolerance in Mice

Sphingosine 1-phosphate (S1P) is known to regulate insulin resistance in hepatocytes, skeletal muscle cells, and pancreatic β-cells. Among its 5 cognate receptors (S1pr1-S1pr5), S1P seems to counteract insulin signaling and confer insulin resistance via S1pr2 in these cells. S1P may also regulate insulin resistance in adipocytes, but the S1pr subtype(s) involved remains unknown. Here, we investigated systemic glucose/insulin tolerance and phenotypes of epididymal adipocytes in high-fat diet (HFD)-fed wild-type and S1pr2-deficient (S1pr2(-/-)) mice. Adult S1pr2(-/-) mice displayed smaller body/epididymal fat tissue weights, but the differences became negligible after 4 weeks with HFD. However, HFD-fed S1pr2(-/-) mice displayed better scores in glucose/insulin tolerance tests and had smaller epididymal adipocytes that expressed higher levels of proliferating cell nuclear antigen than wild-type mice. Next, proliferation/differentiation of 3T3-L1 and 3T3-F442A preadipocytes were examined in the presence of various S1pr antagonists: JTE-013 (S1pr2 antagonist), VPC-23019 (S1pr1/S1pr3 antagonist), and CYM-50358 (S1pr4 antagonist). S1P or JTE-013 treatment of 3T3-L1 preadipocytes potently activated their proliferation and Erk phosphorylation, whereas VPC-23019 inhibited both of these processes, and CYM-50358 had no effects. In contrast, S1P or JTE-013 treatment inhibited adipogenic differentiation of 3T3-F442A preadipocytes, whereas VPC-23019 activated it. The small interfering RNA knockdown of S1pr2 promoted proliferation and inhibited differentiation of 3T3-F442A preadipocytes, whereas that of S1pr1 acted oppositely. Moreover, oral JTE-013 administration improved glucose tolerance/insulin sensitivity in ob/ob mice. Taken together, S1pr2 blockade induced proliferation but suppressed differentiation of (pre)adipocytes both in vivo and in vitro, highlighting a novel therapeutic approach for obesity/type 2 diabetes.

Transcription factor C/EBPβ promotes the transcription of the porcine GPR120 gene

G protein-coupled receptor 120 (GPR120), an adipogenic receptor critical for the differentiation and maturation of adipocytes, plays an important role in controlling obesity in both humans and rodents and, thus, is an attractive target of obesity treatment studies. However, the mechanisms that regulate the expression of porcine GPR120 remain unclear. In this study, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) techniques were used to analyze and identify the binding of C/EBPβ (transcription factor CCAAT/enhancer binding protein beta) to the GPR120 promoter. C/EBPβ overexpression and RNA interference studies showed that C/EBPβ regulated GPR120 promoter activity and endogenous GPR120 expression. The binding site of C/EBPβ in the GPR120 promoter region from -101 to -87 was identified by promoter deletion analysis and site-directed mutagenesis. Overexpression of C/EBPβ increased endogenous GPR120 expression in pig kidney cells (PK). Furthermore, when endogenous C/EBPβ was knocked down, GPR120 mRNA and protein levels were decreased. The stimulatory effect of C/EBPβ on GPR120 transcription and its ability to bind the transcription factor-binding site were confirmed by luciferase, ChIP, and EMSA. Moreover, the mRNA and protein expression levels of C/EBPβ were induced by high fat diet feeding. Taken together, it can be concluded that C/EBPβ plays a vital role in regulating GPR120 transcription and suggests HFD-feeding induces GPR120 transcription by influencing C/EBPβ expression.