The small molecule phenamil is a modulator of adipocyte differentiation and PPARgamma expression

Transcriptomic Analyses Reveal the Effects of Walnut Kernel Cake on Adipose Deposition in Pigs

With the rising cost of animal feed protein, finding affordable and effective substitutes is crucial. Walnut kernel cake, a polyphenol-, fiber-, protein- and fat-rich byproduct of walnut oil extraction, has been underexplored as a potential protein replacement in pig feed. In this study, we found that feeding large Diqing Tibetan pigs walnut kernel cake promoted adipose deposition and improved pork quality during pig growth. Transcriptome analysis revealed the upregulation of genes ANGPTL8, CCNP, ETV4, and TRIB3, associated with adipose deposition. Pathway analysis highlighted enrichment in adipose deposition-related pathways, including PPAR, insulin, PI3K-Akt, Wnt, and MAPK signaling. Further analysis identified DEGs (differentially expressed genes) positively correlated with adipose-related traits, such as PER2 and PTGES. Single-cell transcriptome data pointed to the specific expression of CD248 and PTGES in adipocyte progenitor/stem cells (APSCs), pivotal for adipocyte differentiation and adipose deposition regulation. This study demonstrates walnut kernel cake's potential to substitute soybean cake in pig feed, providing high-quality protein and promoting adipose deposition. It offers insights into feed protein replacement, human functional food, fat metabolism, and related diseases, with marker genes and pathways supporting pig breeding and pork quality improvement.

Integrative analysis of mitochondrial metabolic reprogramming in early-stage colon and liver cancer

Gastrointestinal malignancies, including colon adenocarcinoma (COAD) and liver hepatocellular carcinoma (LIHC), remain leading causes of cancer-related deaths worldwide. To better understand the underlying mechanisms of these cancers and identify potential therapeutic targets, we analyzed publicly accessible Cancer Genome Atlas datasets of COAD and LIHC. Our analysis revealed that differentially expressed genes (DEGs) during early tumorigenesis were associated with cell cycle regulation. Additionally, genes related to lipid metabolism were significantly enriched in both COAD and LIHC, suggesting a crucial role for dysregulated lipid metabolism in their development and progression. We also identified a subset of DEGs associated with mitochondrial function and structure, including upregulated genes involved in mitochondrial protein import and respiratory complex assembly. Further, we identified mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) as a crucial regulator of cancer cell metabolism. Using a genome-scale metabolic model, we demonstrated that HMGCS2 suppression increased glycolysis, lipid biosynthesis, and elongation while decreasing fatty acid oxidation in colon cancer cells. Our study highlights the potential contribution of dysregulated lipid metabolism, including ketogenesis, to COAD and LIHC development and progression and identifies potential therapeutic targets for these malignancies.

Single-cell analysis of white adipose tissue reveals the tumor-promoting adipocyte subtypes

BACKGROUND

The tumor-adipose microenvironment (TAME) is characterized by the enrichment of adipocytes, and is considered a special ecosystem that supports cancer progression. However, the heterogeneity and diversity of adipocytes in TAME remains poorly understood.

METHODS

We conducted a single-cell RNA sequencing analysis of adipocytes in mouse and human white adipose tissue (WAT). We analyzed several adipocyte subtypes to evaluate their relationship and potential as prognostic factors for overall survival (OS). The potential drugs are screened by using bioinformatics methods. The tumor-promoting effects of a typical adipocyte subtype in breast cancer are validated by performing in vitro functional assays and immunohistochemistry (IHC) in clinical samples.

RESULTS

We profiled a comprehensive single-cell atlas of adipocyte in mouse and human WAT and described their characteristics, origins, development, functions and interactions with immune cells. Several cancer-associated adipocyte subtypes, namely DPP4+ adipocytes in visceral adipose and ADIPOQ+ adipocytes in subcutaneous adipose, are identified. We found that high levels of these subtypes are associated with unfavorable outcomes in four typical adipose-associated cancers. Some potential drugs including Trametinib, Selumetinib and Ulixertinib are discovered. Emphatically, knockdown of adiponectin receptor 1 (AdipoR1) and AdipoR2 impaired the proliferation and invasion of breast cancer cells. Patients with AdipoR2-high breast cancer display significantly shorter relapse-free survival (RFS) than those with AdipoR2-low breast cancer.

CONCLUSION

Our results provide a novel understanding of TAME at the single-cell level. Based on our findings, several adipocyte subtypes have negative impact on prognosis. These cancer-associated adipocytes may serve as key prognostic predictor and potential targets for treatment in the future.

Curcuma zedoaria 50% methanol extracts increase adiponectin secretion by enhancing PPARγ mRNA expression in 3T3-L1 cells

Curcuma zedoaria is a characteristic species of its genus that contains little to no curcuminoid. Here, we demonstrate that C. zedoaria extracts with 50% methanol increases adiponectin secretion into the media by enhancing PPARγ mRNA expression in 3T3-L1 cells. These results indicate that C. zedoaria may be useful for preventing/improving lifestyle-related diseases such as diabetes and atherosclerosis.

Biomimetic Nanofibrous 3D Materials for Craniofacial Bone Tissue Engineering

Repair of large bone defects using biomaterials-based strategies has been a significant challenge due to the complex characteristics required for tissue regeneration, especially in the craniofacial region. Tissue engineering strategies aimed at restoration of function face challenges in material selection, synthesis technique, and choice of bioactive factor release in combination with all aforementioned facets. Biomimetic nanofibrous (NF) scaffolds are attractive vehicles for tissue engineering due to their ability to promote endogenous bone regeneration by mimicking the shape and chemistry of natural bone extracellular matrix (ECM). To date, several techniques for generation of biomimetic NF scaffolds have been discovered, each possessing several advantages and drawbacks. This spotlight highlights two of the more popular techniques for biomimetic NF scaffold synthesis: electrospinning and thermally-induced phase separation (TIPS), covering development from inception in each technique as well as discussing the most recent innovations in each fabrication method.

Sesamol Increases Ucp1 Expression in White Adipose Tissues and Stimulates Energy Expenditure in High-Fat Diet-Fed Obese Mice

Sesamol found in sesame oil has been shown to ameliorate obesity by regulating lipid metabolism. However, its effects on energy expenditure and the underlying molecular mechanism have not been clearly elucidated. In this study, we show that sesamol increased the uncoupling protein 1 (Ucp1) expression in adipocytes. The administration of sesamol in high-fat diet (HFD)-fed mice prevented weight gain and improved metabolic derangements. The three-week sesamol treatment of HFD-fed mice, when the body weights were not different between the sesamol and control groups, increased energy expenditure, suggesting that an induced energy expenditure is a primary contributing factor for sesamol’s anti-obese effects. Consistently, sesamol induced the expression of energy-dissipating thermogenic genes, including Ucp1, in white adipose tissues. The microarray analysis showed that sesamol dramatically increased the Nrf2 target genes such as Hmox1 and Atf3 in adipocytes. Moreover, 76% (60/79 genes) of the sesamol-induced genes were also regulated by tert-butylhydroquinone (tBHQ), a known Nrf2 activator. We further verified that sesamol directly activated the Nrf2-mediated transcription. In addition, the Hmox1 and Ucp1 induction by sesamol was compromised in Nrf2-deleted cells, indicating the necessity of Nrf2 in the sesamol-mediated Ucp1 induction. Together, these findings demonstrate the effects of sesamol in inducing Ucp1 and in increasing energy expenditure, further highlighting the use of the Nrf2 activation in stimulating thermogenic adipocytes and in increasing energy expenditure in obesity and its related metabolic diseases.

Mineralized nanofibrous scaffold promotes phenamil-induced osteoblastic differentiation while mitigating adipogenic differentiation

Large bone defects represent a significant unmet medical challenge. Cost effectiveness and better stability make small molecule organic compounds a more promising alternative compared with biomacromolecules, for example, growth factors/hormones, in regenerative medicine. However, one common challenge for the application of these small compounds is their side-effect issue. Phenamil is emerging as an intriguing small molecule to promote bone repair by strongly activating bone morphogenetic protein signaling pathway. In addition to osteogenesis, phenamil also induces significant adipogenesis based on some in vitro studies, which is a concern that impedes it from potential clinical applications. Besides the soluble chemical signals, cellular differentiation is heavily dependent on the microenvironments provided by the 3D scaffolds. Therefore, we developed a 3D nanofibrous biomimetic scaffold-based strategy to harness the phenamil-induced stem cell lineage differentiation. Based on the gene expression, alkaline phosphatase activity, and mineralization data, we indicated that bone-matrix mimicking mineralized-gelatin nanofibrous scaffold effectively improved phenamil-induced osteoblastic differentiation, while mitigating the adipogenic differentiation in vitro. In addition to normal culture conditions, we also indicated that mineralized matrix can significantly improve phenamil-induced osteoblastic differentiation in simulated inflammatory condition. In viewing of the crucial role of mineralized matrix, we developed an innovative and facile mineral deposition-based strategy to sustain release of phenamil from 3D scaffolds for efficient local bone regeneration. Overall, our study demonstrated that biomaterials played a crucial role in modulating small molecule drug phenamil-induced osteoblastic differentiation by providing a bone-matrix mimicking mineralized gelatin nanofibrous scaffolds.

Oxyresveratrol Increases Energy Expenditure through Foxo3a-Mediated Ucp1 Induction in High-Fat-Diet-Induced Obese Mice

The phytochemical oxyresveratrol has been shown to exert diverse biological activities including prevention of obesity. However, the exact reason underlying the anti-obese effects of oxyresveratrol is not fully understood. Here, we investigated the effects and mechanism of oxyresveratrol in adipocytes and high-fat diet (HFD)-fed obese mice. Oxyresveratrol suppressed lipid accumulation and expression of adipocyte markers during the adipocyte differentiation of 3T3-L1 and C3H10T1/2 cells. Administration of oxyresveratrol in HFD-fed obese mice prevented body-weight gains, lowered adipose tissue weights, improved lipid profiles, and increased glucose tolerance. The anti-obese effects were linked to increases in energy expenditure and higher rectal temperatures without affecting food intake, fecal lipid content, and physical activity. The increased energy expenditure by oxyresveratrol was concordant with the induction of thermogenic genes including Ucp1, and the reduction of white adipocyte selective genes in adipose tissue. Furthermore, Foxo3a was identified as an oxyresveratrol-induced gene and it mimicked the effects of oxyresveratrol for induction of thermogenic genes and suppression of white adipocyte selective genes, suggesting the role of Foxo3a in oxyresveratrol-mediated anti-obese effects. Taken together, these data show that oxyresveratrol increases energy expenditure through the induction of thermogenic genes in adipose tissue and further implicates oxyresveratrol as an ingredient and Foxo3a as a molecular target for the development of functional foods in obesity and metabolic diseases.

Identification of Phf16 and Pnpla3 as new adipogenic factors regulated by phytochemicals

Adipocyte differentiation is controlled by multiple signaling pathways. To identify new adipogenic factors, C3H10T1/2 adipocytes were treated with previously known antiadipogenic phytochemicals (resveratrol, butein, sulfuretin, and fisetin) for 24 hours. Commonly regulated genes were then identified by transcriptional profiling analysis. Three genes (chemokine (C-X-C motif) ligand 1 [ Cxcl1], heme oxygenase 1 [ Hmox1], and PHD (plant homeo domain) finger protein 16 [ Phf16]) were upregulated while two genes (G0/G1 switch gene 2 [ G0s2] and patatin-like phospholipase domain containing 3 [ Pnpla3]) were downregulated by these four antiadipogenic compounds. Tissue expression profiles showed that the G0s2 and Pnpla3 expressions were highly specific to adipose depots while the other three induced genes were ubiquitously expressed with significantly higher expression in adipose tissues. While Cxcl1 expression was decreased, expressions of the other four genes were significantly increased during adipogenic differentiation of C3H10T1/2 cells. Small interfering RNA-mediated knockdown including Phf16 and Pnpla3 indicated that these genes might play regulatory roles in lipid accumulation and adipocyte differentiation. Specifically, the silencing of two newly identified adipogenic genes, Phf16 or Pnpla3, suppressed lipid accumulation and expression of adipocyte markers in both 3T3-L1 and C3H10T1/2 cells. Taken together, these data showed previously uncovered roles of Phf16 and Pnpla3 in adipogenesis, highlighting the potential of using phytochemicals for further investigation of adipocyte biology.

Chemical Characterization of Novel Natural Products from the Roots of Asian Rice ( Oryza sativa) that Control Adipocyte and Osteoblast Differentiation

Oryza sativa L. is consumed globally as a staple food, and its roots have been used as a Korean and Chinese medical supplement for protection of the stomach and lungs and for amelioration of vomiting and fever. In our continuing search for biologically effective metabolites from Korean natural materials, we found that an EtOH extract of O. sativa root reciprocally regulated adipocyte and osteoblast differentiation. Chemical analysis of the EtOH extract using a bioassay-guided fractionation protocol led to the isolation and determination of two novel lignans, oryzativols A and B, responsible for these regulatory activities. Using 1D and 2D nuclear magnetic resonance spectroscopic analyses, high-resolution mass spectrometry, and circular dichroism analysis, the structures of the novel compounds were elucidated. We examined their effects on the regulation of mesenchymal stem cell differentiation. Treatment with oryzativol A in the human mesenchymal cell line C3H10T1/2 suppressed gene expression of peroxisome proliferator activated receptor γ, which resulted in a reduction in adipogenesis. Oryzativol A also enhanced the expression of Runx2 and cellular differentiation into osteoblasts in the same mesenchymal stem cell line.

Pyrintegrin Induces Soft Tissue Formation by Transplanted or Endogenous Cells

Focal adipose deficiency, such as lipoatrophy, lumpectomy or facial trauma, is a formidable challenge in reconstructive medicine, and yet scarcely investigated in experimental studies. Here, we report that Pyrintegrin (Ptn), a 2,4-disubstituted pyrimidine known to promote embryonic stem cells survival, is robustly adipogenic and induces postnatal adipose tissue formation in vivo of transplanted adipose stem/progenitor cells (ASCs) and recruited endogenous cells. In vitro, Ptn stimulated human adipose tissue derived ASCs to differentiate into lipid-laden adipocytes by upregulating peroxisome proliferator-activated receptor (PPARγ) and CCAAT/enhancer-binding protein-α (C/EBPα), with differentiated cells increasingly secreting adiponectin, leptin, glycerol and total triglycerides. Ptn-primed human ASCs seeded in 3D-bioprinted biomaterial scaffolds yielded newly formed adipose tissue that expressed human PPARγ, when transplanted into the dorsum of athymic mice. Remarkably, Ptn-adsorbed 3D scaffolds implanted in the inguinal fat pad had enhanced adipose tissue formation, suggesting Ptn’s ability to induce in situ adipogenesis of endogenous cells. Ptn promoted adipogenesis by upregulating PPARγ and C/EBPα not only in adipogenesis induction medium, but also in chemically defined medium specifically for osteogenesis, and concurrently attenuated Runx2 and Osx via BMP-mediated SMAD1/5 phosphorylation. These findings suggest Ptn’s novel role as an adipogenesis inducer with a therapeutic potential in soft tissue reconstruction and augmentation.

Effects of Bioactive Compounds on Odontogenic Differentiation and Mineralization

Direct pulp capping involves the placement of dental materials directly onto vital pulp tissues after deep caries removal to stimulate the regeneration of reparative dentin. This physical barrier will serve as a "biological seal" between these materials and the pulp tissue. Although numerous direct pulp capping materials are available, the use of small bioactive compounds that can potently stimulate and expedite reparative dentin formation is still underexplored. Here, the authors compared and evaluated the pro-osteogenic and pro-odontogenic effects of 4 small bioactive compounds- phenamil (Phen), purmorphamine (Pur), genistein (Gen), and metformin (Met). The authors found that these compounds at noncytotoxic concentrations induced differentiation and mineralization of preosteoblastic MC3T3-E1 cells and preodontoblastic dental pulp stem cells (DPSCs) in a dose-dependent manner. Among them, Phen consistently and potently induced differentiation and mineralization in vitro. A single treatment with Phen was sufficient to enhance the mineralization potential of DPSCs in vitro. More importantly, Phen-treated DPSCs showed enhanced odontogenic differentiation and mineralization in vivo. Our study suggests that these small bioactive compounds merit further study for their potential clinical use as pulp capping materials.

Small Molecule-Induced Complement Factor D (Adipsin) Promotes Lipid Accumulation and Adipocyte Differentiation

Adipocytes are differentiated by various transcriptional cascades integrated on the master regulator, Pparγ. To discover new genes involved in adipocyte differentiation, preadipocytes were treated with three newly identified pro-adipogenic small molecules and GW7845 (a Pparγ agonist) for 24 hours and transcriptional profiling was analyzed. Four genes, Peroxisome proliferator-activated receptor γ (Pparγ), human complement factor D homolog (Cfd), Chemokine (C-C motif) ligand 9 (Ccl9), and GIPC PDZ Domain Containing Family Member 2 (Gipc2) were induced by at least two different small molecules but not by GW7845. Cfd and Ccl9 expressions were specific to adipocytes and they were altered in obese mice. Small hairpin RNA (shRNA) mediated knockdown of Cfd in preadipocytes inhibited lipid accumulation and expression of adipocyte markers during adipocyte differentiation. Overexpression of Cfd promoted adipocyte differentiation, increased C3a production, and led to induction of C3a receptor (C3aR) target gene expression. Similarly, treatments with C3a or C3aR agonist (C4494) also promoted adipogenesis. C3aR knockdown suppressed adipogenesis and impaired the pro-adipogenic effects of Cfd, further suggesting the necessity for C3aR signaling in Cfd-mediated pro-adipogenic axis. Together, these data show the action of Cfd in adipogenesis and underscore the application of small molecules to identify genes in adipocytes.

Phenamil enhances the adipogenic differentiation of hen preadipocytes

A study was conducted to examine the effect of phenamil on adipogenic differentiation and expression of key adipogenic transcripts in hen preadipocytes. Preadipocytes were isolated from 20-week old Single Comb White Leghorn hens (Gallas gallus, Lohman strain). The experiment lasted for 48 h and had six treatments. Non-treated control (C) cells, cells treated with dexamethasone, 3-isobutyl-1-methylxanthine, insulin, and oleic acid (DMIOA) (T1), DMIOA + 15 μM phenamil (T2), DMIOA + 30 μM phenamil (T3), 15 μM phenamil alone (T4), and 30 μM phenamil alone (T5). Neutral lipid accumulation and the mRNA expression of key adipogenic transcripts were measured in all treatments and compared. Lipid accumulation was detected in T1, T2, and T3 only. Expression of peroxisome proliferator receptor-activator gamma 2 (PPARγ2), the core enhancer binding protein α (C/EBPα), C/EBPβ, fatty acid binding protein 4 (FABP4), and lipoprotein lipase (LPL) as well as ETS variant 4 (ETV4) and 5 was higher (P < 0.05) in T2, T3, T4, and T5 compared to C. Expression of these transcripts was higher (P < 0.05) in T2 and T3 compared to T4 and T5. The core enhancer binding protein α, C/EBPβ, and FABP4 were highly expressed (P < 0.05) in T1 compared to C. However, the expression of PPARγ2, LPL, and ETV4 and ETV5 was not significantly different. Expression of C/EBPα, C/EBPβ, and FABP4 was higher (P < 0.05) in T2 and T3 compared to T1. Expression of sterol regulatory element binding protein 1 (SREBP1) and leptin receptor (LEPR) was not significantly different among the treatments. In conclusion, phenamil enhances DMIOA-induced adipogenic differentiation of hen preadipocytes but does not induce adipogenesis by itself.

Prdm4 induction by the small molecule butein promotes white adipose tissue browning

Increasing the thermogenic activity of adipocytes holds promise as an approach to combating human obesity and its related metabolic diseases. We identified PR domain containing 4 (Prdm4) induction by the small molecule butein as a means to induce uncoupling protein 1 expression, increase energy expenditure, and stimulate the generation of thermogenic adipocytes. This study highlights a Prdm4-dependent pathway, modulated by small molecules, that stimulates white adipose tissue browning.

The effect of combined regulation of the expression of peroxisome proliferator-activated receptor-γ and calcitonin gene-related peptide on alcohol-induced adipogenic differentiation of bone marrow mesenchymal stem cells

Studies have shown that alcohol can upregulate the expression of peroxisome proliferator-activated receptor-γ (PPARγ) gene in bone marrow mesenchymal stem cells (BMSCs). High expression of PPARγ can promote adipogenic differentiation of BMSCs, and reduce their osteogenic differentiation. Abnormal proliferation of adipocytes and fatty accumulation in osteocytes can result in high intraosseous pressure and disturbance of blood circulation in the femoral head, which induces osteonecrosis of the femoral head (ONFH). Downregulation of PPARγ is efficient in inhibiting adipogenesis and maintaining osteogenesis of BMSCs, which might potentially reduce the incidence of ONFH. Calcitonin gene-related peptide (CGRP) is a neuropeptide gene which has been closely associated with bone regeneration. In this study, we aimed to observe the effect of combined regulation of the expression of PPARγ and CGRP genes on alcohol-induced adipogenic differentiation of BMSCs. Our results demonstrated that simultaneous downregulation of PPARγ and upregulation of CGRP was efficient in suppressing adipogenic differentiation of BMSCs and promoting their osteogenic differentiation. These findings might enlighten a novel approach for the prevention of ONFH.

Adipocytes under assault: environmental disruption of adipose physiology

The burgeoning obesity epidemic has placed enormous strains on individual and societal health mandating a careful search for pathogenic factors, including the contributions made by endocrine disrupting chemicals (EDCs). In addition to evidence that some exogenous chemicals have the capacity to modulate classical hormonal signaling axes, there is mounting evidence that several EDCs can also disrupt metabolic pathways and alter energy homeostasis. Adipose tissue appears to be a particularly important target of these metabolic disruptions. A diverse array of compounds has been shown to alter adipocyte differentiation, and several EDCs have been shown to modulate adipocyte physiology, including adipocytic insulin action and adipokine secretion. This rapidly emerging evidence demonstrating that environmental contaminants alter adipocyte function emphasizes the potential role that disruption of adipose physiology by EDCs may play in the global epidemic of metabolic disease. Further work is required to better characterize the molecular targets responsible for mediating the effects of EDCs on adipose tissue. Improved understanding of the precise signaling pathways altered by exposure to environmental contaminants will enhance our understanding of which chemicals pose a threat to metabolic health and how those compounds synergize with lifestyle factors to promote obesity and its associated complications. This knowledge may also improve our capacity to predict which synthetic compounds may alter energy homeostasis before they are released into the environment while also providing critical evidentiary support for efforts to restrict the production and use of chemicals that pose the greatest threat to human metabolic health. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

Suppression of PPARγ through MKRN1-mediated ubiquitination and degradation prevents adipocyte differentiation

The central regulator of adipogenesis, PPARγ, is a nuclear receptor that is linked to obesity and metabolic diseases. Here we report that MKRN1 is an E3 ligase of PPARγ that induces its ubiquitination, followed by proteasome-dependent degradation. Furthermore, we identified two lysine sites at 184 and 185 that appear to be targeted for ubiquitination by MKRN1. Stable overexpression of MKRN1 reduced PPARγ protein levels and suppressed adipocyte differentiation in 3T3-L1 and C3H10T1/2 cells. In contrast, MKRN1 depletion stimulated adipocyte differentiation in these cells. Finally, MKRN1 knockout MEFs showed an increased capacity for adipocyte differentiation compared with wild-type MEFs, with a concomitant increase of PPARγ and adipogenic markers. Together, these data indicate that MKRN1 is an elusive PPARγ E3 ligase that targets PPARγ for proteasomal degradation by ubiquitin-dependent pathways, and further depict MKRN1 as a novel target for diseases involving PPARγ.

Butein is a novel anti-adipogenic compound

Rhus verniciflua Stokes (RVS) has been used as a traditional herbal medicine for its various biological activities including anti-adipogenic effects. Activity-guided separation led to the identification of the anti-adipogenic functions of butein. Butein, a novel anti-adipogenic compound, robustly suppressed lipid accumulation and inhibited expression of adipogenic markers. Molecular studies showed that activated transforming growth factor-β (TGF-β) and suppressed signal transducer and activator of transcription 3 (STAT3) signaling pathways were mediated by butein. Analysis of the temporal expression profiles suggests that TGF-β signaling precedes the STAT3 in the butein-mediated anti-adipogenic cascade. Small interfering RNA-mediated silencing of STAT3 or SMAD2/3 blunted the inhibitory effects of butein on adipogenesis indicating that an interaction between two signaling pathways is required for the action of butein. Upon butein treatments, stimulation of TGF-β signaling was still preserved in STAT3 silenced cells, whereas regulation of STAT3 signaling by butein was significantly impaired in SMAD2/3 silenced cells, further showing that TGF-β acts upstream of STAT3 in the butein-mediated anti-adipogenesis. Taken together, the present study shows that butein, a novel anti-adipogenic compound from RVS, inhibits adipocyte differentiation through the TGF-β pathway followed by STAT3 and peroxisome proliferator-activated receptor γ signaling, further implicating potential roles of butein in TGF-β- and STAT3-dysregulated diseases.

Functional relevance of genes implicated by obesity genome-wide association study signals for human adipocyte biology

AIMS/HYPOTHESIS

Genome-wide association studies (GWAS) have identified numerous single-nucleotide polymorphisms associated with obesity, consequently implying a role in adipocyte biology for many closely residing genes. We investigated the functional relevance of such genes in human adipocytes.

METHODS

We selected eight genes (BDNF, MAF, MTCH2, NEGR1, NPC1, PTER, SH2B1 and TMEM18) from obesity GWAS and analysed their effect in human adipogenesis using small interfering (si)RNA-mediated knockdown, their regulation by metabolic agents in adipocytes and pre-adipocytes, and gene expression in paired samples of human fat biopsies (68 non-obese, 165 obese) by quantitative real-time PCR.

RESULTS

We show a two- to threefold upregulation of MAF, MTCH2 and NEGR1 and a two- to fourfold downregulation of BDNF and PTER during adipogenesis. Knockdown of BDNF (mean ± SEM; 83.8 ± 4.7% of control; p = 0.0002), MTCH2 (72.7 ± 9.5%; p = 0.0006), NEGR1 (70.2 ± 5.7%; p < 0.0001) and TMEM18 (70.8 ± 6.1%; p < 0.0001) significantly inhibited adipocyte maturation, while knockdown of the other proteins had no effect. Insulin slightly induced MAF (1.65-fold; p = 0.0009) and MTCH2 (1.72-fold; p < 0.0001), while it suppressed BDNF (59.6%; p = 0.0009), NEGR1 (58.0%; p = 0.0085) and TMEM18 (69.3%; p = 0.0377) in adipocytes. The synthetic glucocorticoid dexamethasone suppressed MAF (45.7%; p = 0.0022), BDNF (66.6%; p = 0.0012) and TMEM18 (63.5%; p = 0.0181), but induced NEGR1 (3.2-fold; p = 0.0117) expression. Furthermore, MTCH2, NEGR1 and TMEM18 were differentially expressed in subcutaneous and visceral adipose tissue. TMEM18 expression was decreased in the adipose tissue of obese patients, and negatively correlated with anthropometric variables and adipocyte size.

CONCLUSIONS/INTERPRETATION

Our results imply a regulatory role for TMEM18, BDNF, MTCH2 and NEGR1 in adipocyte differentiation and biology. In addition, we show a variation of MAF expression during adipogenesis, while NPC1, PTER and SH2B1 were not regulated.

A computational procedure for identifying master regulator candidates: a case study on diabetes progression in Goto-Kakizaki rats

Background

We have recently identified a number of active regulatory networks involved in diabetes progression in Goto-Kakizaki (GK) rats by network screening. The networks were quite consistent with the previous knowledge of the regulatory relationships between transcription factors (TFs) and their regulated genes. To study the underlying molecular mechanisms directly related to phenotype changes, such as diseases, we also previously developed a computational procedure for identifying transcriptional master regulators (MRs) in conjunction with network screening and network inference, by effectively perturbing the phenotype states.

Results

In this work, we further improved our previous method for identifying MR candidates, by listing them in a more reliable manner, and applied the method to reveal the MR candidates for diabetes progression in GK rats from the active networks. Specifically, the active TF-gene pairs for different time periods in GK rats were first extracted from the networks by network screening. Another set of active TF-gene pairs was selected by network inference, by considering the gene expression signatures for those periods between GK and Wistar-Kyoto (WKY) rats. The TF-gene pairs extracted by the two methods were then further selected, from the viewpoints of the emergence specificity of TF in GK rats and the regulated-gene coverage of TF in the expression signature. Finally, we narrowed all of the genes down to only 5 TFs (Etv4, Fus, Nr2f1, Sp2, and Tcfap2b) as the candidates of MRs, with 54 regulated genes, by merging the selected TF-gene pairs.

Conclusions

The present method has successfully identified biologically plausible MR candidates, including the TFs related to diabetes in previous reports. Although the experimental verifications of the candidates and the present procedure are beyond the scope of this study, we narrowed down the candidates to 5 TFs, which can be used to perform the verification experiments relatively easily. The numerical results showed that our computational method is an efficient way to detect the key molecules responsible for biological phenomena.

A novel RNAi lethality rescue screen to identify regulators of adipogenesis

Adipogenesis, the differentiation of fibroblast-like mesenchymal stem cells into mature adipocytes, is tightly regulated by a complex cascade of transcription factors, including the nuclear receptor Peroxisome proliferator activator receptor γ (PPARγ). RNAi-mediated knock down libraries may present an atractive method for the identification of additional adipogenic factors. However, using in vitro adipogenesis model systems for high-throughput screening with siRNA libraries is limited since (i) differentiation is not homogeneous, but results in mixed cell populations, and (ii) the expression levels (and activity) of adipogenic regulators is highly dynamic during differentiation, indicating that the timing of RNAi-mediated knock down during differentiation may be extremely critical. Here we report a proof-of-principle for a novel RNAi screening method to identify regulators of adipogenesis that is based on lethality rescue rather than differentiation, using microRNA expression driven by a PPARγ responsive RNA polymerase II promoter. We validated this novel method through screening of a dedicated deubiquitinase knock down library, resulting in the identification of UCHL3 as an essential deubiquitinase in adipogenesis. This system therefore enables the identification of novel genes regulating PPARγ-mediated adipogenesis in a high-throughput setting.

Silk peptides inhibit adipocyte differentiation through modulation of the Notch pathway in C3H10T1/2 cells

Silk protein is a biocompatible material that has been used in many biotechnological applications and exhibits body fat-lowering effects. Recent studies have shown that silk peptides increase expression of osteogenic markers in osteoblast-like cells. Because osteogenic and adipogenic differentiation from common mesenchymal progenitor cells are inverse processes and often regulated reciprocally, we hypothesized that silk peptides might suppress adipocyte differentiation. We therefore endeavored to evaluate the effects of silk peptides on adipocyte differentiation in C3H10T1/2 cells. We find that silk peptides inhibit lipid accumulation and morphological differentiation in these cells. Molecular studies show that silk peptides block expression of adipocyte-specific genes such as peroxisome proliferator-activated receptor γ and its targets, including aP2, Cd36, CCAAT enhancer binding proteinα. Silk peptides appear to inhibit adipogenesis by suppression of the Notch pathway, repressing the Notch target genes Hes-1 and Hey-1. In addition, these peptides inhibit endogenous Notch activation, as shown by a reduction in generation of Notch intracellular domain. N-[N-(3.5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butylester, compound E, and WPE-III-31C, which are all known Notch signaling inhibitors, block adipocyte differentiation to an extent similar to silk peptides. Together, our data demonstrate that silk peptides can modulate adipocyte differentiation through inhibition of the Notch signaling and further suggest potential future strategies for treating obesity and its related metabolic diseases.

Current methods of adipogenic differentiation of mesenchymal stem cells

There has been a recent increase in our understanding in the isolation, culture, and differentiation of mesenchymal stem cells (MSCs). Concomitantly, the availability of MSCs has increased, with cells now commercially available, including human MSCs from adipose tissue and bone marrow. Despite an increased understanding of MSC biology and an increase in their availability, standardization of techniques for adipogenic differentiation of MSCs is lacking. The following review will explore the variability in adipogenic differentiation in vitro, specifically in 3T3-L1 and primary MSCs derived from both adipose tissue and bone marrow. A review of alternative methods of adipogenic induction is also presented, including the use of specific peroxisome proliferator-activated receptor-gamma agonists as well as bone morphogenetic proteins. Finally, we define a standard, commonly used adipogenic differentiation medium in the hopes that this will be adopted for the future standardization of laboratory techniques--however, we also highlight the essentially arbitrary nature of this decision. With the current, rapid pace of electronic publications, it becomes imperative for standardization of such basic techniques so that interlaboratory results may be easily compared and interpreted.

miR-615-3p promotes the phagocytic capacity of splenic macrophages by targeting ligand-dependent nuclear receptor corepressor in cirrhosis-related portal hypertension

Hypersplenism is a condition in which the spleen is overactive. It is common in patients with cirrhosis-related portal hypertension. The over-activated hemophagocytic splenic macrophages are an important cause of hypersplenism. MicroRNAs (miRNAs) are 21-22 nt single-stranded RNAs expressed endogenously, which play important roles in many diseases. We have found by microarray, previously, that miR-615-3p is highly expressed in splenic macrophages of hypersplenism. In this study, we found that miR-615-3p enhanced the phagocytic capacity of splenic macrophages. Bioinformatics analysis indicated that ligand-dependent nuclear receptor corepressor (LCoR) was a potential phagocytosis-related target of miR-615-3p. This was proved by dual luciferase assay and Western blot in THP-1 cells and normal/hypersplenisum splenic macrophages. Our results showed that the presence of miR-615-3p repressed the expression of LCoR, a derepressor of peroxisome proliferator-activated receptor gamma (PPARγ), which has been confirmed to be able to promote the phagocytic capacity of macrophages. In conclusion, high expression of miR-615-3p in over-activated splenic macrophages depresses LCoR expression, low level of LCoR derepresses the expression of PPARγ and finally upregulated PPARγ enhances the phagocytic capacity of splenic macrophages. This finding might be useful in the study of hypersplenism and other macrophage-associated diseases.

TLE3 is a dual-function transcriptional coregulator of adipogenesis

PPARγ and Wnt signaling are central positive and negative regulators of adipogenesis, respectively. Here we identify the groucho family member TLE3 as a transcriptional integrator of the PPARγ and Wnt pathways. TLE3 is a direct target of PPARγ that participates in a feed-forward loop during adipocyte differentiation. TLE3 enhances PPARγ activity and functions synergistically with PPARγ on its target promoters to stimulate adipogenesis. At the same time, induction of TLE3 during differentiation provides a mechanism for termination of Wnt signaling. TLE3 antagonizes TCF4 activation by β-catenin in preadipocytes, thereby inhibiting Wnt target gene expression and reversing β-catenin-dependent repression of adipocyte gene expression. Transgenic expression of TLE3 in adipose tissue in vivo mimics the effects of PPARγ agonist and ameliorates high-fat-diet-induced insulin resistance. Our data suggest that TLE3 acts as a dual-function switch, driving the formation of both active and repressive transcriptional complexes that facilitate the adipogenic program.

Endocrine disrupting chemicals and the developmental programming of adipogenesis and obesity

Obesity and related disorders are a burgeoning public health epidemic, particularly in the U.S. Currently 34% of the U.S. population is clinically obese (BMI > 30) and 68% are overweight (BMI > 25), more than double the worldwide average and 10-fold higher than Japan and South Korea. Obesity occurs when energy intake exceeds energy expenditure; however, individuals vary widely in their propensity to gain weight and accrue fat mass, even at identical levels of excess caloric input. Clinical, epidemiological, and biological studies show that obesity is largely programmed during early life, including the intrauterine period. The environmental obesogen hypothesis holds that prenatal or early life exposure to certain endocrine disrupting chemicals can predispose exposed individuals to increased fat mass and obesity. Obesogen exposure can alter the epigenome of multipotent stromal stem cells, biasing them toward the adipocyte lineage at the expense of bone. Hence, humans exposed to obesogens during early life might have an altered stem cell compartment, which is preprogrammed toward an adipogenic fate. This results in a higher steady state number of adipocytes and potentially a lifelong struggle to maintain a healthy weight, which can be exacerbated by societal influences that promote poor diet and inadequate exercise. This review focuses on the developmental origins of the adipocyte, the relationship between adipocyte number and obesity, and how obesogenic chemicals may interfere with the highly efficient homeostatic mechanisms regulating adipocyte number and energy balance.