Decreased Adipocyte Differentiation Research Articles

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

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

Schisandrin C isolated from Schisandra chinensis fruits inhibits lipid accumulation by regulating adipogenesis and lipolysis through AMPK signaling in 3T3-L1 adipocytes.

In this study, lignans of Schisandra chinensis fruits (SCF) were profiled using HPLC-MS/MS, and the inhibitory effects of nine of these lignans were evaluated on triglyceride (TG) accumulation. We then examined the effects and molecular mechanisms on adipogenesis and lipolysis of schisandrin C (SC), which most inhibited TG levels during adipogenesis of 3T3-L1 cells. Treatment of 3T3-L1 cells with SC markedly decreased adipocyte differentiation but did not influence cell proliferation. During adipogenesis, SC significantly reduced total lipid and TG contents and down-regulated the mRNA expressions of C/EBPα, PPARγ, SREBP1c, aP2, and FAS. In addition, SC significantly increased p-AMPK, and this activation regulated the protein levels of major adipogenic transcription factors (PPARγ and C/EBPα). Furthermore, SC lowered the mRNA expressions of HSL and perilipin and inhibited pancreatic lipase levels, which are both related to lipolysis. PRACTICAL APPLICATIONS: Our results indicate that SC regulates lipogenesis and lipolysis by increasing AMPK phosphorylation and suggest that it may be beneficial for preventing obesity and related metabolic diseases. Thus, this study proposes a mechanical basis for developing SC-containing foods as a beneficial dietary strategy.

Bisphenol A and 2,3,7,8-tetrachlorodibenzo-p-dioxin at non-cytotoxic doses alter the differentiation potential and cell function of rat adipose-stem cells.

The possibility of chemical contamination is an important issue to consider when designing a cell therapy strategy. Both bisphenol A (BPA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are among the most environmentally relevant endocrine disrupting chemicals (EDCs, compounds with a high affinity for adipose tissue) recently studied. Adipose-derived stem cells (ASCs) are mesenchymal stromal cells (MSCs) obtained from adipose tissue widely used in regenerative medicine to prevent and treat diseases in several tissues and organs. Although the experimental use of tissue-engineered constructs requires careful analysis for approval and implantation, there has been a recent increase in the number of approved clinical trials for this promising strategy. This study aimed to evaluate cell viability, apoptosis, DNA damage, and the adipogenic or osteogenic differentiation potential of rat adipose-derived stem cells (rASCs) exposed to previously established non-cytotoxic doses of BPA and TCDD in vitro. Results demonstrated that 10μM of BPA and 10nM of TCDD were able to significantly reduce cell viability, while all exposure levels resulted in DNA damage, although did not increase the apoptosis rate. According to the analysis of adipogenic differentiation, 1μM of BPA induced the significant formation of oil droplets, suggesting an increased adipocyte differentiation, while both 10μM of BPA and 10nM of TCDD decreased adipocyte differentiation. Osteogenic differentiation did not differ among the treatments. As such, BPA and TCDD in the concentrations tested can modify important processes in rASCs such as cell viability, adipogenic differentiation, and DNA damage. Together, these findings prove that EDCs play an important role as contaminants, putatively interfering in cell differentiation and thus impairing the therapeutic use of ASCs.

Signal transducer and activator of transcription 3 as a potential therapeutic target for Graves’ orbitopathy

The roles of signal transducer and activator of transcription 3 (STAT3) in inflammation, oxidative stress, and adipogenesis during Graves’ orbitopathy (GO) are incompletely understood. Here, STAT3 expression in orbital tissues (from individuals with GO and healthy control subjects) was studied, and the role of STAT3 in GO pathogenesis was examined through small-interfering RNA (siRNA)-mediated silencing in primary orbital fibroblasts. STAT3 mRNA expression was higher in GO orbital tissues than in non-GO tissues. Treatment with proinflammatory cytokines, thyroid-stimulating hormone, or insulin-like growth factor-1 induced STAT3 mRNA in GO orbital fibroblasts, but not in non-GO cells. STAT3 silencing inhibited interleukin-1β-induced inflammatory cytokines and oxidative stress-induced haem oxygenase-1 expression. STAT3 siRNA-transfected GO orbital fibroblasts showed decreased adipocyte differentiation. STAT3 affected proinflammatory cytokine production, oxidative stress responses, and adipogenesis in an in vitro model of GO, suggesting that STAT3 mediates GO pathology, and that modulating STAT3 expression may have therapeutic potential against GO.

1210-P: Subcutaneous-Depot Specific Adiposity Change Is Associated with the Ectopic Fat Depot and Tissue Damage in High-Fat High-Sucrose (HFHS) Fed Fabp4 Cre-ERK2 Knockout Mice

Previous reports suggested that low subcutaneous adiposity increases the risk of cardiovascular events and diabetes. Mechanisms of depot-specific differences are still unknown. During studying tissue-specific roles of ERK2 (MAPK1), we observed Fabp4Cre mediated adipocyte-specific ERK2 knockout mice (AE2KO) with HFHS diet showed diminished the size of adipocytes in an only subcutaneous depot and increased ectopic fat depot and fibrotic steatohepatitis. The male AE2KO was created by crossing the C57BL/6 background Fabp4-Cre with ERK2flox/flox mouse. ERK2flox/flox Cre- mouse was used as a control. ERK2KO was observed only in white adipose tissues. With a normal diet, AE2KO mice showed no phenotype. HFHS diet started at age 6 weeks for 18 weeks. AE2KO exhibited 18% increase in body weight (n=8 each, p<0.05). Whereas HFHS increased adipose weight, the distribution of adipocyte size showed a significant decrease in subcutaneous depot (30 vs. 60 µm in mode, p<0.05 by 2-way ANOVA, n=8 each), but not in gonadal. RNA-sequence analysis (n=4, each) revealed a significant increase in expression of lipolysis gene (Prkaca, Tshr, and Adcy) and of the genes reported to cause a defect in fat storage (L3mbtl3, Pik3r1). Fasting glucose was increased and the Insulin tolerance test showed no change in plasma glucose in AE2KO compared to control (105% vs. 75% at 60 min, p<0.05, n=8 each). Liver weight increased 1.8-fold (n=8, p<0.05). NAS score increased (6.2 vs. 4.4, p<0.05, n=6) with prominent fibrosis. The increased ectopic fat depot was also observed in skeletal muscle and kidney. Oxygen consumption and RER was not changed. ERK2 knockout in human subcutaneous preadipocyte by Crispr Cas9 decreased adipocyte differentiation by 50%, suggesting an involvement of ERK2 in adipogenesis. These results strongly indicated that ERK2 is involved in subcutaneous depot abnormality which causes ectopic fat depot and organ damage by a high caloric diet. Disclosure Y. Ishinoda: None. T. Adachi: None. H. Kumagai: None. Y. Ido: None. M. Noguchi: None. Y. Yumita: None. K. Kagami: None. A. Osaki: None. Y. Satoh: None. S. Endo: None. A. Kasuga: None.

TET1 promotes RXRα expression and adipogenesis through DNA demethylation

Adipose tissue is important for systemic metabolic homeostasis in response to environmental changes, and adipogenesis involves dynamic transcriptional regulation. Ten-eleven translocation (TET) enzymes (TET1, 2 and 3) oxidize the 5-methylcytosine (5mC) in DNA to 5-hydroxylmethylcytosine (5hmC), which associates with transcriptional activation. Step by step, 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) are further generated by TETs and the cytosine can be restored through base-excision repair. It is still unclear how DNA demethylation is involved in adipogenesis. Through a phenotypic screen, we found TET inhibition decreased adipocyte differentiation from mesenchymal stem cells (MSCs). Comparing with the undifferentiated MSCs, the differentiated adipocytes exhibited much higher levels of 5hmC and slightly increased 5fC and 5caC. Higher 5hmC was associated with better differentiation at single-cell level by image analysis. TET1 is upregulated in differentiation and depletion of it significantly impaired the gain of 5hmC. Furthermore, Tet1 depletion significantly hampered the adipocyte differentiation. Using RNA-seq, 5mC and 5hmC-DNA immunoprecipitation, we found that Tet1 knockout led to lower expression of genes associated with lipid metabolism and fat cell differentiation. Genes with loss of 5mC or gain of 5hmC in adipocytes include Lipe, Bmp4 and Rxra, etc. RXRα agonist partially rescued the inhibitory effect of Tet1 knockout for adipogenesis. So, Rxra is one of the critical TET1 modulated genes. Together, TET1-mediated active DNA demethylation plays an important role in adipogenesis.

Lactosylceramide induced by elastin-derived peptides decreases adipocyte differentiation.

Elastin, the major protein of the extracellular matrix, is specially found in cardiovascular tissues and contributing to 30-50% of the dry weight of blood vessels. Elastin regulates cell signalling pathways involved in morphogenesis, injury response and inflammation. The function of elastin is frequently compromised in damaged or aged elastic tissues. Indeed, elastin degradation, observed during ageing, and the resulting production of elastin-derived peptides (EDPs), have crucial impacts on cardiovascular disease (atherosclerosis, thrombosis) or on metabolism disease progressions (type 2 diabetes or non-alcoholic steatohepatitis). In the present study, we analysed the EDP effects on 3T3 preadipocyte cell differentiation. In a first part, we treated 3T3-L1 cells with EDP and visualized the lipid droplet accumulation by the oil red O staining and measured the expression of various transcription factors and adipocyte-specific mRNAs by real-time RT-PCR. We demonstrated that the elastin receptor complex, ERC, is activated by EDPs and decreased adipocyte differentiation by a modulation of crucial adipogenesis transcriptional factor particularly PPARγ. In a second part, we identified the signalling pathway implicated in EDP-reduced cell differentiation. The flow cytometry and immunocytochemistry approaches showed that ERC activated by EDP produced a second messenger, lactosylceramide (Lac-Cer). Moreover, this Lac-Cer production favoured the phosphorylation of ERK1-2 (p-ERK1-2), to decrease adipocyte differentiation by a modulation of adipogenesis transcriptional factor PPARγ. To conclude, the EDP/Lac-Cer/p-ERK1-2 signalling pathway may be studied further as a critical target for treating complications associated with adipocyte dedifferentiation such as obesity and diabetes insulin resistance.

MiR-377-3p regulates adipogenic differentiation of human bone marrow mesenchymal stem cells by regulating LIFR.

MicroRNAs are members of the family of non-coding small RNAs that regulate gene expression either by inhibiting mRNA translation or by promoting mRNA degradation at the post-transcriptional level. They play an important role in the differentiation of human bone marrow mesenchymal stem cells (hMSCs) into adipocytes. However, the role of microRNAs in this process remains to be poorly understood. Here, we observed that miR-377-3p expression was markedly decreased during adipogenic differentiation of hMSCs. Overexpression of miR-377-3p decreased adipocyte differentiation and downregulated the expression of adipogenic markers. Meanwhile, bioinformatics-based studies suggested that LIFR is a target of miR-377-3p. Further analysis confirmed that expression of LIFR present markedly increased during adipogenic differentiation of hMSCs. In addition, downregulation expression of LIFR significantly inhibited the process of adipocyte differentiation. To confirm the relation between miR-377-3p and LIFR, luciferase reporter assays were carried out. The results indicated that miR-377-3p bound directly to the 3'-untranslated region of LIFR. These data indicate that miR-377-3p suppressed adipogenesis of hMSCs by targeting LIFR, which provides novel insights into the molecular mechanism of miRNA-mediated cellular differentiation.

Regulation of De Novo Adipocyte Differentiation Through Cross Talk Between Adipocytes and Preadipocytes.

There are many known adipokines differentially secreted from the different adipose depots; however, their paracrine and autocrine effects on de novo adipocyte formation are not fully understood. By developing a coculture method of preadipocytes with primary subcutaneous and visceral adipocytes or tissue explants, we could show that the total secretome inhibited preadipocyte differentiation. Using a proteomics approach with fractionated secretome samples, we were able to identify a spectrum of factors that either positively or negatively affected adipocyte formation. Among the secreted factors, Slc27a1, Vim, Cp, and Ecm1 promoted adipocyte differentiation, whereas Got2, Cpq, interleukin-1 receptor-like 1/ST2-IL-33, Sparc, and Lgals3bp decreased adipocyte differentiation. In human subcutaneous adipocytes of lean subjects, obese subjects, and obese subjects with type 2 diabetes, Vim and Slc27a1 expression was negatively correlated with adipocyte size and BMI and positively correlated with insulin sensitivity, while Sparc and Got2 showed the opposite trend. Furthermore, we demonstrate that Slc27a1 was increased upon weight loss in morbidly obese patients, while Sparc expression was reduced. Taken together, our findings identify adipokines that regulate adipocyte differentiation through positive or negative paracrine and autocrine feedback loop mechanisms, which could potentially affect whole-body energy metabolism.

Yin Yang 1 is a multi-functional regulator of adipocyte differentiation in 3T3-L1 cells

Yin Yang 1 (YY1) is an ubiquitously distributed transcription factor that belongs to the GLI-Kruppel class of zinc finger proteins. The mechanism by which YY1 regulates adipocyte differentiation remains unclear. In this study, we investigated the functional role of YY1 during adipocyte differentiation. During the early stage, YY1 gene and protein expression was transiently downregulated upon the induction of differentiation, however, it was consistently induced during the later stage. YY1 overexpression decreased adipocyte differentiation and blocked cell differentiation at the preadipocyte stage, while YY1 knockdown by RNA interference increased adipocyte differentiation. YY1 physically interacted with PPARγ (Peroxisome proliferator-activated receptor gamma) and C/EBPβ (CCAAT/enhancer-binding protein beta) respectively in 3T3-L1 cells. Through its interaction with PPARγ, YY1 directly decreased PPARγ transcriptional activity. YY1 ectopic expression prevented C/EBPβ from binding to the PPARγ promoter, resulting in the downregulation of PPARγ transcriptional activity. These results indicate that YY1 repressed adipocyte differentiation by repressing the activity of adipogenic transcriptional factors in 3T3-L1 cells.

Statins and diabetes risk: how real is it and what are the mechanisms?

In randomized trials and many observational studies, statins are associated with a modest excess of type 2 diabetes mellitus. High-intensity statins, such as atorvastatin 80 mg and rosuvastatin 20 mg, are associated with a higher excess risk of diabetes than moderate-intensity statins, such as atorvastatin 10 mg, simvastatin 20-40 mg, or pravastatin 40 mg. Multiple mechanisms have been proposed for statin-associated diabetes risk, primarily related to increased insulin resistance or impaired insulin secretion. Genetic polymorphisms with reduced HMG CoA reductase function are associated with weight gain, insulin resistance, and diabetes. Animal models have shown that HMG CoA inhibition has multiple downstream effects that may increase diabetes risk. Statin impairment of insulin signaling, decreased adipocyte differentiation, decreased pancreatic β-cell insulin secretion, and other effects have also been found. The excess risk of diabetes appears to be confined to those who are already at risk for developing diabetes. Diabetes is diagnosed only 2-4 months earlier in statin-treated patients and therefore is unlikely to have no long-term adverse consequences. The clinical impact of statin-associated diabetes is likely unimportant. The cardiovascular risk reduction benefit from statin far outweighs the potential for adverse effects in all but the very lowest risk individuals.

Identification and validation of N-acetyltransferase 2 as an insulin sensitivity gene.

Decreased insulin sensitivity, also referred to as insulin resistance (IR), is a fundamental abnormality in patients with type 2 diabetes and a risk factor for cardiovascular disease. While IR predisposition is heritable, the genetic basis remains largely unknown. The GENEticS of Insulin Sensitivity consortium conducted a genome-wide association study (GWAS) for direct measures of insulin sensitivity, such as euglycemic clamp or insulin suppression test, in 2,764 European individuals, with replication in an additional 2,860 individuals. The presence of a nonsynonymous variant of N-acetyltransferase 2 (NAT2) [rs1208 (803A>G, K268R)] was strongly associated with decreased insulin sensitivity that was independent of BMI. The rs1208 "A" allele was nominally associated with IR-related traits, including increased fasting glucose, hemoglobin A1C, total and LDL cholesterol, triglycerides, and coronary artery disease. NAT2 acetylates arylamine and hydrazine drugs and carcinogens, but predicted acetylator NAT2 phenotypes were not associated with insulin sensitivity. In a murine adipocyte cell line, silencing of NAT2 ortholog Nat1 decreased insulin-mediated glucose uptake, increased basal and isoproterenol-stimulated lipolysis, and decreased adipocyte differentiation, while Nat1 overexpression produced opposite effects. Nat1-deficient mice had elevations in fasting blood glucose, insulin, and triglycerides and decreased insulin sensitivity, as measured by glucose and insulin tolerance tests, with intermediate effects in Nat1 heterozygote mice. Our results support a role for NAT2 in insulin sensitivity.

Evaluation of Antiobesity Effect of Mangiferin in Adipogenesis-Induced Human Mesenchymal Stem Cells by Assessing Adipogenic Genes

We aimed to examine the anti-adipogenic effects of mangiferin (xanthone glucoside) and its related mechanism. Human mesenchymal stem cells (hMSCs) were cultured in Dulbecco's modified Eagle medium, after 60% confluence adipocyte differentiation was induced. Differentiation-induced hMSCs were cultured in the presence and absence of 10, 20 and 40 μmol of mangiferin from day 0 to day 10. Adipocyte differentiation and lipid accumulation were significantly decreased in 40 μmol mangiferin-treated groups when compared with the reference drugs (quercetin- and orlistat-treated groups). Using quantitative reverse transcription polymerase chain reaction, we studied the mRNA expression levels of resistin, adipocyte fatty acid-binding protein 2 (aP2), lipoprotein lipase (LPL), peroxisome proliferator-activated receptor (PPAR-γ) and tumor necrosis factor-α, in hMSCs undergoing adipocyte differentiation; treatment with mangiferin attenuated the expression of those adipogenic genes and decreased adipocyte differentiation. Mangiferin significantly inhibited hMSCs to preadipocyte differentiation within the first 2 days of treatment, indicating that the anti-adipogenic effects of mangiferin are achieved through the inhibition of differentiation and maturation. Practical Applications It is well known that various plant derived compounds presents antiobesity effect. However still there is lack of drugs for the arrest or inhibition of adipocyte differentiation from mesenchymal stem cell precursors. hMSCs treated with adipocyte differentiation medium along with mangiferin inhibits preadipocyte differentiation and maturation, via suppressing lipid accumulation. Mangiferin treatment resulted in a significant (p < 0.05) decrease in GPDH and triglyceride levels as well as an increase in LDH activity and attenuated lipid accumulation compared with untreated differentiating preadipocytes. This effect was demonstrated by the observed down-regulation of adipogenesis related genes after hMSCs underwent induced adipocyte differentiation.

Lipolytic and antiadipogenic effects of (3,3-dimethylallyl) halfordinol on 3T3-L1 adipocytes and high fat and fructose diet induced obese C57/BL6J mice

Aegle marmelos Correa., (Rutaceae) is a medium sized tree distributed in South East Asia and used traditionally for the management of obestiy and diabetes. In this study the lipolytic and antiadipogenic effects of (3,3-dimethylallyl) halfordinol (Hfn) isolated from leaves of A. marmelos have been investigated. Intracellular lipid accumulation was measured by oil red O staining and glycerol secretion. The expression of genes related to adipocyte differentiation was analyzed by reverse transcriptase–polymerase chain reaction (RT-PCR). Hfn decreased intracellular triglyceride accumulation and increased glycerol release in a dose dependent manner (5–20μg/ml) in differentiated 3T3-L1 adipocytes. In high fat diet fed C57/BL 6J mice, treatment with Hfn for four weeks reduced plasma glucose, insulin and triglyceride levels and showed a significant reduction in total adipose tissue mass by 37.85% and visceral adipose tissue mass by 62.99% at 50mg/kg b.w. concentration. RT-PCR analyses indicated that Hfn decreased the expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT enhancer binding protein α (CEBPα) and increased the expression of sterol regulatory enzyme binding protein (SREBP-1c), peroxisome proliferator-activated receptor α (PPARα), Adiponectin and Glucose transporter protein 4 (GLUT4) compared to the high fat diet group. These results suggested that Hfn decreased adipocyte differentiation and stimulated lipolysis of adipocytes. This study justifies the folklore medicinal uses and claims about the therapeutic values of this plant for the management of insulin resistance and obesity.

Comparison of extract and flavonoid‐rich Fraction from mulberry on proliferation and lipid accumulation in 3T3‐L1 adipocytes (LB392)

This study was performed to investigated the effect of ethanol extracts and fraction of Morus alba L. on adipocyte differentiation in 3T3‐L1 cell. Obesity is major obstacle for improving health. Therefore, the therapeutic approach using natural plants has been proposed as a novel strategy for preventing obesity. Fruits of mulberry (Morus alba L.) belonging to the Moraceae family have been widely used for therapeutic purposes in Asian countries for centuries. Many study investigated that mulberry fruits can be used as a warming agent, as a remedy for dysentery, and as a tonic, sedative, laxative, odontalgic, anthelmintic, expectorant, and emetic. This study was performed to investigated the effect of ethanol extract and flavonoid‐rich fraction (A2) of Morus alba. on adipocyte differentiation in 3T3‐L1cell. The anti‐proliferation effects of ethanolic extracts and A2 fraction were measured by MTT assay. Cell viability of ehtanolic extract decreased but not A2 fraction during 72 hr in preadipocyte. For anti‐adipogenic effects of Morus alba, ethanolic extract and A2 fraction were examined Oil red O staining assay. Treatment of 3T3‐L1 cells with ethanolic extracts and A2 fraction decreased adipocyte differentiation in a dose‐dependent manner by 18.1% and 32.7% in 100 μg/ml, respectively. The results indicate that Morus alba L. is a possible candidate for regulating lipid accumulation in obesity.Grant Funding Source: This work was supported by Priority Research Centers Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(KNF‐2009‐0094017).

The forkhead transcription factor FOXO1 stimulates the expression of the adipocyte resistin gene

Resistin is known as an adipocyte-specific hormone that can cause insulin resistance and decrease adipocyte differentiation. It can be regulated by transcriptional factors, but the possible role of forkhead transcription factor FOXO1 in regulating resistin gene expression is still unknown. Using 3T3 fibroblast and C3H10T1/2 and 3T3-L1 adipocytes, we found that transient overexpression of a non-phosphorylatable, constitutively active FOXO1, but not the wild type of FOXO1 or a DNA binding-deficient FOXO1, activated resistin promoter-directed luciferase expression. However, transient overexpression of a dominant-negative FOXO1 inactivated resistin promoter activity and reduced resistin mRNA expression. These observations indicate that the action of FOXO1 on resistin gene expression requires the activation of FOXO1 and that the effect of FOXO1 depends on the phosphorylation and dephosphorylation of FOXO1. The FOXO1 protein target sites on the resistin promoter were localized to the proximal −3545 to −787bp of 5′-flanking region of the resistin promoter. A chromatin immunoprecipitation assay also showed that FOXO1 bound the resistin promoter at nucleotide regions of −1539 to −1366bp and −1016 to −835bp, but not at the regions of −795 to −632bp. Results of this study suggest that FOXO1 transcription factor likely activates the expression of adipocyte resistin gene via direct association with the upstream resistin promoter.

Inhibitory Effects of Ethyl Acetate-Soluble Fraction from Morus alba on Lipid Accumulation in 3T3-L1 Cells

Fruits of mulberry (Morus alba) have been widely used for therapeutic purposes in Asian countries for centuries. Treatment of 3T3-L1 cells with ethanolic extracts of M. alba decreased adipocyte differentiation at 100 microg/mL by 18.6%. Treatment suppressed mRNA levels of PPARgamma and C/EBPalpha expression in 3T3-L1 cells. However, the extract did not change free glycerol release from mature adipocytes. Thus, M. alba inhibited lipid accumulation by regulating transcription factors in 3T3-L1 adipocytes without a lipolytic effect. Among the soluble- fractions, the ethyl acetate-soluble fraction had the highest antiadipogenic effects on 3T3-L1 cells. This fraction decreasing intracellular lipid accumulation by 38.5% in response to treatment with 100 microg/mL. In addition, HPLC analysis of the ethyl acetate-soluble fraction of M. alba contained 167.7 microM of protocatechulic acid in 1 mg/mL of fraction, which inhibited lipid accumulation by 44.8% in response to treatment with 100 microM. From these results, M. alba is a possible candidate for regulating lipid accumulation in obesity.

Decreased fat accumulation in 3T3‐L1 pre‐adipocytes treated with extracts of heat‐processed soy flour and breads

SummaryThe potential anti‐adipogenic effects of gluten‐free soy breads made from germinated soybean (GS), steamed soybean (SS) or roasted soybean (RS) were evaluated in an in vitro adipocyte cell model. GS and RS increased the total phenolic (TP) and total flavonoid (TF) contents of flours compared with the raw soybean (NS) flour. RS and GS had the highest TP (1.04 GAE mg g−1) and TF (0.92 CAE mg g−1) contents. Baking increased the TP content of breads, 0.09–0.26 GAE mg g−1, compared with the flours. Fermentation during breadmaking increased the DPPH scavenging activities compared with the flours. The ABTS scavenging exhibited similar patterns to those of DPPH. Lipid accumulation in 3T3‐L1 cells shows that the alcoholic extracts (100 μg mL−1) of SS flour and bread decreased adipocyte differentiation by 1.6‐ and 2.1‐fold, respectively, compared with control. SS bread extract substantially downregulated the adipogenesis‐related genes such as acetyl‐CoA carboxylase and glycerol‐3‐phosphate dehydrogenase.

Micro RNA ‐146b promotes adipogenesis by suppressing the SIRT 1‐ FOXO 1 cascade

Sirtuin 1 (SIRT1) plays a critical role in the maintenance of metabolic homeostasis and promotes fat mobilization in white adipose tissue. However, regulation of SIRT1 during adipogenesis, particularly through microRNAs, remains unclear. We observed that miR-146b expression was markedly increased during adipogenesis in 3T3-L1 cells. Differentiation of 3T3-L1 was induced by overexpression of miR-146b. Conversely, inhibition of miR-146b decreased adipocyte differentiation. Bioinformatics-based studies suggested that SIRT1 is a target of miR-146b. Further analysis confirmed that SIRT1 was negatively regulated by miR-146b. We also observed that miR-146b bound directly to the 3′-untranslated region of SIRT1 and inhibited adipogenesis through SIRT1 downregulation. The miR-146b/SIRT1 axis mediates adipogenesis through increased acetylation of forkhead box O1 (FOXO1). Expression of miR-146b was increased and SIRT1 mRNA subsequently decreased in the adipose tissues of diet-induced and genetically obese mice. Furthermore, in vivo knockdown of miR-146b by a locked nucleic acid miR-146b antagomir significantly reduced body weight and fat volume in accordance with upregulation of SIRT1 and subsequent acetylation of FOXO1. Therefore, the miR-146b/SIRT1 pathway could be a potential target for obesity prevention and treatment.

Caffeine inhibits adipogenic differentiation of primary adipose-derived stem cells and bone marrow stromal cells

Caffeine consumption has been related to loss of body weight and modulates lipid metabolism. However, impacts of caffeine on adipogenic differentiation have not been well determined yet. The present study evaluated the effects of caffeine on adipogenesis using primary rat adipose-derived stem cells (ADSCs) and a mouse bone marrow stromal cell line (M2-10B4) in vitro. ADSCs and M2-10B4 were continuously exposed to caffeine (0.1–1mM) during adipogenic differentiation for 7 and 12days, respectively. Oil red O and Nile red staining showed that caffeine reduced lipid droplet and adipocyte levels in both cell types. In addition, Nile red staining and FACScan flow cytometry showed that caffeine dose-dependently decreased adipocyte differentiation from 20% to 50% of the control ADSCs and M2-10B4 cells. Caffeine decreased the expression of adipogenesis-related genes including peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein-α, adipocyte lipid binding protein, lipoprotein lipase, leptin, and TNFα in a dose-dependent manner. Rather, low concentration of caffeine (0.1mM) significantly increased IL-6 expression, but unexpectedly inhibited that at a concentration more than 0.3mM. Taken together, caffeine was able to effectively inhibit adipogenic differentiation of ADSCs and M2-10B4 cells partly through its inhibition of adipogenesis-related factors.