Adipocyte Differentiation In 3T3-L1 Cells Research Articles

E3 ubiquitin ligase E6AP negatively regulates adipogenesis by downregulating proadipogenic factor C/EBPalpha.

CCAAT/Enhancer Binding Protein Alpha (C/EBPα) is a key transcription factor involved in the adipocyte differentiation. Here for the first time we demonstrate that E6AP, an E3 ubiquitin ligase inhibits adipocyte differentiation in 3T3-L1 cells as revealed by reduced lipid staining with oil red. Knock down of E6AP in mouse 3T3L1 preadipocytes is sufficient to convert them to adipocytes independent of external hormonal induction. C/EBPα protein level is drastically increased in E6AP deficient 3T3L1 preadipocytes while inverse is observed when wild type E6AP is over expressed. We show that transient transfection of wild type E6AP downregulates C/EBPα protein expression in a dose dependent manner while catalytically inactive E6AP-C843A rather stabilizes it. In addition, wild type E6AP inhibits expression of proadipogenic genes while E6AP-C843A enhances them. More importantly, overexpression of E6AP-C843A in mesenchymal progenitor cells promotes accumulation of lipid droplets while there is drastically reduced lipid droplet formation when E6AP is over expressed. Taken together, our finding suggests that E6AP may negatively control adipogenesis by inhibiting C/EBPα expression by targeting it to ubiquitin-proteasome pathway for degradation.

Inhibition of preadipocyte differentiation and lipid accumulation by 7-O-galloyl-d-sedoheptulose treatment in 3T3-L1 adipocytes

In this study, we investigated the effect of 7-O-galloyl-d-sedoheptulose (GS) on adipocyte differentiation in 3T3-L1 cells. GS significantly suppressed 3T3-L1 differentiation. The activation of adenosine monophosphate-activated protein kinase (AMPK) was demonstrated by measuring phosphorylation. In addition, GS down-regulated the adipogenesis-related protein expression of the sterol regulatory element-binding protein 1c. GS significantly reduced the protein expression of the peroxisome proliferator-activated receptor γ and of the CCAAT/enhancer-binding protein α, two key transcription factors in adipogenesis. These findings indicate that GS exerts anti-adipogenic activity via AMPK activation and may act to prevent obesity.

Regulation of adipocyte differentiation of 3T3-L1 cells by PDZRN3

PDZRN3, a member of the PDZRN (or LNX) family of proteins, is essential for the differentiation of mesenchymal stem cells into myotubes, but it plays an inhibitory role in the differentiation of these cells into osteoblasts. Given that mesenchymal stem cells also differentiate into adipocytes, we examined the possible role of PDZRN3 in adipogenesis in mouse 3T3-L1 preadipocytes. The expression of PDZRN3 decreased at both the mRNA and protein levels during adipogenic differentiation. RNAi-mediated depletion of PDZRN3 enhanced the differentiation of 3T3-L1 cells into adipocytes as assessed on the basis of lipid accumulation. The upregulation of aP2 and CCAAT/enhancer-binding protein (C/EBP)-β during adipocyte differentiation was also enhanced in the PDZRN3-depleted cells, as was the induction of peroxisome proliferator-activated receptor-γ (PPARγ), an upstream regulator of aP2 and C/EBPα, at both the mRNA and protein levels. Among transcription factors that control the expression of PPARγ, we found that STAT5b, but not STAT5a, was upregulated in PDZRN3-depleted cells at both mRNA and protein levels. Tyrosine phosphorylation of STAT5b, but not that of STAT5a, was also enhanced at an early stage of differentiation by PDZRN3 depletion. In addition, the expression of C/EBPβ during the induction of differentiation was enhanced at the mRNA and protein levels in PDZRN3-depleted cells. Our results thus suggest that PDZRN3 negatively regulates adipogenesis in 3T3-L1 cells through downregulation of STAT5b and C/EBPβ and consequent suppression of PPARγ expression.

Determination of protocatechuic acid from Rubus coreanus fruits and their inhibitory effects of triglyceride accumulation on 3T3‐L1 cells

Obesity is a serious health problem in industrialized countries because it is implicated in various diseases. With the recent increased interest in antiobesity, many investigators are interested in finding phytochemicals such as triterpenoid, essential oil, flavonoid that play a role in this adipocyte differentiation mechanism. Fruits of black raspberry (Rubus coreanus) belonging to the Rosaceae family has been used for centuries as a traditional alternative medicine. This study was investigated determination of protocatechuic acid and their effects of TG accumulation on adipocyte differentiation in 3T3‐L1cells. From this extract fractionated with petroleum ether (A1) and MtBE (A2). We used HPLC to determine the level of protocatechulic acid in A2 fraction from Rubus coreanus. The protocatechulic acid in A2 fraction from Rubus coreanus were confirmed by comparison of the retention times and UV spectra of the samples with those of standard compounds. Thousand ppm of A2 fraction from Rubus coreanus contained 76.64 μM of protocatechulic acid. Anti‐adipogenic effects of A2 fraction from Rubus coreanus were investigated by measuring cell viability and differentiation in 3T3‐L1cells. Treatment of 3T3‐L1 cells with A2 fraction of Rubus coreanus decreased cell viability in time‐dependently. And treatment of A2 fraction inhibited lipid accumulation on adipocytes by 28.8% in 100ug/ml. We also found that containing compounds exerted inhibitory activity in the adipocyte differentiation in this study. Protocatechuic acid which is contained in A2 fraction form Rubus coreanus inhibited lipid accumulation on adipocyte by 26.8 % in 10ug/ml. Thus, Rubus coreanus is a possible candidate for regulating lipid accumulation in obesity.

Scutellarin from Scutellaria baicalensis Suppresses Adipogenesis by Upregulating PPARα in 3T3-L1 Cells

Adipocyte dysfunction is a major cause of obesity, which is associated strongly with many disorders including psychological and medical morbidities, metabolic abnormalities, and cardiovascular diseases as well as a series of cancers. This study investigated the antiadipogenic activity of scutellarin (1) in 3T3-L1 preadipocytes as well as the underlying molecular mechanisms. It was observed that 1 reduced adipocyte differentiation of 3T3-L1 cells potently, as evidenced by a decrease in cellular lipid accumulation. At the molecular level, mRNA expression of the master adipogenic transcription factors, PPARγ and C/EBPα, was decreased markedly. However, mRNA levels of C/EBPβ, the upstream regulator of PPARγ and C/EBPα, were not decreased by 1. Moreover, a dose-dependent upregulation of PPARα was observed for 1. Computational modeling indicated that 1 can bind to PPARα, γ, and δ each in a distinct manner, while it can activate PPARα only by forming a hydrogen bond with Y464, thus stabilizing the AF-2 helix and activating PPARα. Therefore, these results suggest that 1, a major component of Scutellaria baicalensis, attenuates fat cell differentiation by upregulating PPARα as well as downregulating the expression of PPARγ and C/EBPα, thus showing therapeutic potential for obesity-related diseases.

6‐Gingerol Inhibits Rosiglitazone‐Induced Adipogenesis in 3T3‐L1 Adipocytes

We investigated the effects of 6-gingerol ((S)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-decanone) on the inhibition of rosiglitazone (RGZ)-induced adipogenesis in 3T3-L1 cells. The morphological changes were photographed based on staining lipid accumulation by Oil-Red O in RGZ (1 µmol/l)-treated 3T3-L1 cells without or with various concentrations of 6-gingerol on differentiation day 8. Quantitation of triglycerides content was performed in cells on day 8 after differentiation induction. Differentiated cells were lysed to detect mRNA and protein levels of adipocyte-specific transcription factors by real-time reverse transcription-polymerase chain reaction and Western blot analysis, respectively. 6-gingerol (50 µmol/l) effectively suppressed oil droplet accumulation and reduced the sizes of the droplets in RGZ-induced adipocyte differentiation in 3T3-L1 cells. The triglyceride accumulation induced by RGZ in differentiated 3T3-L1 cells was also reduced by 6-gingerol (50 µmol/l). Treatment of differentiated 3T3-L1 cells with 6-gingerol (50 µmol/l) antagonized RGZ-induced gene expression of peroxisome proliferator-activated receptor (PPAR)γ and CCAAT/enhancer-binding protein α. Additionally, the increased levels of mRNA and protein in adipocyte-specific fatty acid binding protein 4 and fatty acid synthase induced by RGZ in 3T3-L1 cells were decreased upon treatment with 6-gingerol. Our data suggests that 6-gingerol may be beneficial in obesity, by reducing adipogenesis partly through the down-regulating PPARγ activity.

Identification of LRP16 as a Negative Regulator of Insulin Action and Adipogenesis in 3T3-L1 Adipocytes

Leukemia related protein 16 (LRP16) was first cloned from acute myeloid leukemia cells in our laboratory. In the present study, we sought to investigate the role of LRP16 in insulin action and sensitivity, using LRP16-depleted and -overexpressing 3T3-L1 cells. LRP16 silencing resulted in a reduction of the expression and secretion of tumor necrosis factor-alpha (TNF-α) and a concomitant increase in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ). Moreover, LRP16 depletion promoted insulin-induced glucose uptake and adipocyte differentiation of 3T3-L1 cells. In contrast, LRP16 overexpression increased TNF-α secretion, suppressed glucose uptake, and attenuated 3T3-L1 cell differentiation. The phosphorylation levels of insulin receptor substrate 1 (IRS-1), phosphatidylinositide 3-kinase (PI3-K), and Akt were increased in LRP16-deficient 3T3-L1 cells, and conversely, diminished in LRP16-overexpressing 3T3-L1 cells, when compared to the corresponding control cells. Additionally, LRP16 overexpression raised the phosphorylation level of mammalian target of rapamycin (mTOR). The pretreatment with rapamycin, a specific inhibitor of mTOR, prevented the TNF-α elevation and PPAR-γ reduction and restored the phosphorylation of IRS-1, PI3-K, and Akt in LRP16-overexpressing cells. Our data collectively indicate that LRP16 acts as a negative regulator of insulin action and adipogenesis in 3T3-L1 adipocytes, which involves the activation of the mTOR signaling pathway.

백모근(白茅根) 청피(靑皮) 오수유(吳茱萸) 복합방(複合方)(YY312)의 고지방식이로 유도된 마우스와 3T3-L1 세포에서 항비만 효과

Objectives : The purpose of this study was to determine the anti-obesity effect and molecular mechanism of YY312, a herbal extract composed of Imperatae Rhizoma, Citri Unshius Pericarpium Immaturus, and Evodiae Fructus, on a high-fat diet-induced animal model and on 3T3-L1 cells. Methods : C57BL/6 mice were fed for 6 weeks with a normal diet or a high-fat diet (HFD). Then they orally administered daily with 300 mg/kg YY312 for next 10 weeks. Body weight and food consumption were recorded weekly and daily, respectively. Tissue weights, serum lipid, and glucose levels were analyzed at the end of the study. Additionally, the effects of YY312 on adipocyte differentiation in 3T3-L1 cells were examined. After differentiating 3T3-L1 cells were treated with YY312, Oil-red O staining, RT-PCR, and Western blotting were performed for lipid accumulation, mRNA expression of adipogenesis gene, and AMP-activated protein kinase (AMPK) phosphorylation, respectively. Results : YY312-administered mice showed a significant reduction of body weights and abdominal adipose tissue weights. YY312 also reduced the serum levels of triglycerides and total cholesterol, compared with the HFD group. Treatment with YY312 inhibited lipid accumulation and blocked expression of adipogenic transcription factors and lipogenesis genes, including peroxisome proliferator-activated receptor <TEX>${\gamma}$</TEX>, CCAT/enhancer binding protein <TEX>${\alpha}$</TEX> and fatty acid synthase. YY312 increased AMPK phosphorylation in 3T3-L1 adipocytes. Conclusions : This study showed that herbal extract YY312 has an anti-obesity effect in vitro and in vivo. Thus, YY312 could be developed as a supplement for reduction of body weight gain induced by an HFD.

ER stress signalling through eIF2α and CHOP, but not IRE1α, attenuates adipogenesis in mice.

Although obesity is associated with endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) in adipose tissue, it is not known how UPR signalling affects adipogenesis. To test whether signalling through protein kinase RNA-like ER kinase/eukaryotic initiation factor 2 alpha (PERK/eIF2α) or inositol-requiring enzyme 1 alpha/X-box binding protein 1 (IRE1α/XBP1) is required for adipogenesis, we studied the role of UPR signalling in adipocyte differentiation in vitro and in vivo in mice. The role of UPR signalling in adipogenesis was investigated using 3T3-L1 cells and primary mouse embryonic fibroblasts (MEFs) by activation or inhibition of PERK-mediated phosphorylation of the eIF2α- and IRE1α-mediated splicing of Xbp1 mRNA. Body weight change, fat mass composition and adipocyte number and size were measured in wild-type and genetically engineered mice fed a control or high-fat diet (HFD). ER stress repressed adipocyte differentiation in 3T3-L1 cells. Impaired eIF2α phosphorylation enhanced adipocyte differentiation in MEFs, as well as in mice. In contrast, increased eIF2α phosphorylation reduced adipocyte differentiation in 3T3-L1 cells. Forced production of CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP), a downstream target of eIF2α phosphorylation, inhibited adipogenesis in 3T3-L1 cells. Mice with deletion of Chop (also known as Ddit3) (Chop (-/-)) gained more fat mass than wild-type mice on HFD. In addition, Chop deletion in genetically obese Lepr (db/db) mice increased body fat mass without altering adipocyte size. In contrast to the eIF2α-CHOP pathway, activation or deletion of Ire1a (also known as Ern1) did not alter adipocyte differentiation in 3T3-L1 cells. These results demonstrate that eIF2α-CHOP suppresses adipogenesis and limits expansion of fat mass in vivo in mice, rendering this pathway a potential therapeutic target.

Brazilein fromCaesalpinia sappanL. Antioxidant Inhibits Adipocyte Differentiation and Induces Apoptosis through Caspase-3 Activity and Anthelmintic Activities againstHymenolepis nanaandAnisakis simplex

Brazilein, a natural, biologically active compound from Caesalpinia sappan L., has been shown to exhibit anti-inflammatory and antioxidant properties and to inhibit the growth of several cancer cells. This study verifies the antioxidant and antitumor characteristics of brazilein in skin cancer cells and is the first time to elucidate the inhibition mechanism of adipocyte differentiation, cestocidal activities against Hymenolepis nana, and reduction of spontaneous movement in Anisakis simplex. Brazilein exhibits an antioxidant capacity as well as the ability to scavenge DPPH• and ABTS•+ free radicals and to inhibit lipid peroxidation. Brazilein inhibited intracellular lipid accumulation during adipocyte differentiation in 3T3-L1 cells and suppressed the induction of peroxisome proliferator-activated receptor γ (PPARγ), the master regulator of adipogenesis, suggesting that brazilein presents the antiobesity effects. The toxic effects of brazilein were evaluated in terms of cell viability, induction of apoptosis, and the activity of caspase-3 in BCC cells. The inhibition of the growth of skin cancer cells (A431, BCC, and SCC25) by brazilein is greater than that of human skin malignant melanoma (A375) cells, mouse leukemic monocyte macrophage (RAW 264.7 cells), and noncancerous cells (HaCaT and BNLCL2 cells). The anthelmintic activities of brazilein against Hymenolepis nana are better than those of Anisakis simplex.

Radiolytic transformation of rotenone with potential anti-adipogenic activity

Radiolytic transformation of the isoflavonoid rotenone (1) with γ-irradiation afforded two new degraded products, rotenoisins A (2) and (3). The structures of the two new rotenone derivatives were elucidated on the basis of spectroscopic methods. The new products 2 and 3 exhibited significantly enhanced inhibitory activities against pancreatic lipase and adipocyte differentiation in 3T3-L1 cells when compared to parent rotenone.

Centipede grass exerts anti-adipogenic activity through inhibition of C/EBPβ, C/EBPα, and PPARγ expression and the AKT signaling pathway in 3T3-L1 adipocytes

BackgroundCentipede grass (CG) originates from China and South America and is reported to contain several C-glycosyl flavones and phenolic constituents, including maysin and luteolin derivatives. This study aimed to investigate, for the first time, the antiobesity activity of CG and its potential molecular mechanism in 3T3-L1 cells.MethodsTo study the effect of CG on adipogenesis, differentiating 3T3-L1 cells were treated every day with CG at various concentrations (0–100 μg/ml) for six days. Oil-red O staining and triglyceride content assay were performed to determine the lipid accumulation in 3T3-L1 cells. The expression of mRNAs or proteins associated with adipogenesis was measured using RT-PCR and Western blotting analysis. We examined the effect of CG on level of phosphorylated Akt in 3T3-L1 cells treated with CG at various concentration s during adipocyte differentiation.ResultsDifferentiation was investigated with an Oil-red O staining assay using CG-treated 3T3-L1 adipocytes. We found that CG suppressed lipid droplet formation and adipocyte differentiation in 3T3-L1 cells in a dose-dependent manner. Treatment of the 3T3-L1 adipocytes with CG resulted in an attenuation of the expression of adipogenesis-related factors and lipid metabolic genes. The expression of C/EBPα and PPARγ, the central transcriptional regulators of adipogenesis, was decreased by the treatment with CG. The expression of genes involved in lipid metabolism, aP2 were significantly inhibited following the CG treatment. Moreover, the CG treatment down-regulated the phosphorylation levels of Akt and GSK3β.ConclusionsTaken collectively, these data indicated that CG exerts antiadipogenic activity by inhibiting the expression of C/EBPβ, C/EBPα, and PPARγ and the Akt signaling pathway in 3T3-L1 adipocytes.

Aristolochia Manshuriensis Kom Inhibits Adipocyte Differentiation by Regulation of ERK1/2 and Akt Pathway

Aristolochia manshuriensis Kom (AMK) is a traditional medicinal herb used for the treatment of arthritis, rheumatism, hepatitis, and anti-obesity. Because of nephrotoxicity and carcinogenicity of AMK, there are no pharmacological reports on anti-obesity potential of AMK. Here, we showed AMK has an inhibitory effect on adipocyte differentiation of 3T3-L1 cells along with significantly decrease in the lipid accumulation by downregulating several adipocyte-specific transcription factors including peroxisome proliferation-activity receptor γ (PPAR-γ), CCAAT/enhancer binding protein α (C/EBP-α) and C/EBP-β, which are critical for adipogenesis in vitro. AMK also markedly activated the extracellular signal-regulated protein kinase 1/2 (ERK1/2) pathway including Ras, Raf1, and mitogen-activated protein kinase kinase 1 (MEK1), and significantly suppressed Akt pathway by inhibition of phosphoinositide-dependent kinase 1 (PDK1). Aristolochic acid (AA) and ethyl acetate (EtOAc) fraction of AMK with AA were significantly inhibited TG accumulation, and regulated two pathway (ERK1/2 and Akt) during adipocyte differentiation, and was not due to its cytotoxicity. These two pathways were upstream of PPAR-γ and C/EBPα in the adipogenesis. In addition, gene expressions of secreting factors such as fatty acid synthase (FAS), adiponectin, lipopreotein lipase (LPL), and aP2 were significantly inhibited by treatment of AMK during adipogenesis. We used the high-fat diet (HFD)-induced obesity mouse model to determine the inhibitory effects of AMK on obesity. Oral administration of AMK (62.5 mg/kg/day) significantly decreased the fat tissue weight, total cholesterol (TC), and low density lipoprotein-cholesterol (LDL-C) concentration in the blood. The results of this study suggested that AMK inhibited lipid accumulation by the down-regulation of the major transcription factors of the adipogensis pathway including PPAR-γ and C/EBP-α through regulation of Akt pathway and ERK 1/2 pathway in 3T3-L1 adipocytes and HFD-induced obesity mice, and AA may be main act in inhibitory effects of AMK during adipocyte differentiation.

Indole-3-carbinol directly targets SIRT1 to inhibit adipocyte differentiation

Indole-3-carbinol (I3C), a natural product of Brassica vegetables such as broccoli and cabbage, inhibits proliferation and induces apoptosis in various cancer cells. I3C has recently received attention as a possible anti-obesity agent. However, how I3C interacts with specific targets in the pathways involved in obesity and metabolic disorders is unknown. Silent mating type information regulation 2 homolog 1 (SIRT1), a NADþ-dependent deacetylase sirtuin, has recently emerged as a novel therapeutic target for metabolic diseases. Herein, we report that I3C is a potent, specific SIRT1 activator efficacious in cultured 3T3-L1 cell lines. A pull-down assay showed that I3C binds to SIRT1. To assess the significance of this binding, we determined whether I3C could activate SIRT1 deacetylase activity in a cell-free system. We found that I3C binds to SIRT1 and activates SIRT1 deacetylase activity in 3T3-L1 cells. In addition, I3C did not inhibit adipocyte differentiation in 3T3-L1 cells in which SIRT1 was knockdowned. Further, reverse transcriptase polymerase chain reaction analysis showed that I3C treatment reduced mRNA levels of adipogenic genes that encode for C/EBPa, PPARg2, FAS, and aP2 in 3T3-L1 cells but not in SIRT1 knockdown cells. Overall, these results suggested that I3C ameliorates adipogenesis by activating SIRT1 in 3T3-L1 cells.

The Role of Nocturnin in Early Adipogenesis and Modulation of Systemic Insulin Resistance in Human

The deadenylase nocturnin (Noc, Ccrn4l) has been recently found to regulate lipid metabolism and to control preadipocyte differentiation. Here, we showed that among the five deadenylases tested, Noc and Pan2 exhibited a biphasic expression which is out of phase to each other during adipocyte differentiation of 3T3-L1 cells. The expression levels of other deadenylases, including Parn, Ccr4, and Caf1, were relatively unchanged or reduced. The immediate early expressed Noc during 3T3-L1 adipogenesis was involved in regulating mitotic clonal expansion (MCE) and cyclin D1 expression, as demonstrated in Noc-silenced 3T3-L1 cells and Noc(-/-) primary mouse embryonic fibroblasts (MEFs). Transcriptional profiling of Noc-depleted 3T3-L1 adipocytes revealed that most of the differentially expressed genes were related to cell growth and proliferation. In human adipose tissue, NOC mRNA level negatively associated with both fasting serum insulin and homeostasis model assessment of insulin resistance, and positively associated with both adiponectin mRNA levels and circulating adiponectin levels. Taken together, these results suggest the role of Noc in the modulation of early adipogenesis as well as systemic insulin sensitivity.

Black soybean anthocyanins inhibit adipocyte differentiation in 3T3-L1 cells

Anthocyanins are naturally occurring polyphenolic pigments in plants that have been shown to decrease weight gain and insulin resistance in mice-fed high-fat diets. We investigated the effects of anthocyanins on cell growth, differentiation, and lipolysis in 3T3-L1 cells to test our hypothesis that anthocyanins could reduce adipose tissue mass by acting directly on adipocytes. Anthocyanin extracts from black soybeans were used and composed of 3 of the following major anthocyanins: cyanidine-3-O-glucoside (68.3%), delphinidin-3-O-glucoside (25.2%), and petunidin-3-O-glucoside (6.5%). Treatment with 12.5 and 50 μg/mL of black soybean anthocyanins exhibited inhibitory effects on the proliferation of both preconfluent preadipocytes (P < .01) and maturing postconfluent adipocytes (P < .01). In fully differentiated adipocytes, the number of viable cells was reduced by black soybean anthocyanins (P < .01). Treatment with 50 μg/mL of black soybean anthocyanins slightly increased epinephrine-induced lipolysis but decreased the basal lipolysis of fully differentiated adipocytes (P < .05). Black soybean anthocyanins also reduced lipid accumulation and suppressed the expression of the peroxisome proliferator–activated receptor γ, a major transcription factor for the adipogenic gene (P < .01). These results suggest that black soybean anthocyanins inhibit adipocyte differentiation and basal lipolysis, which may contribute to their antiobesity and antidiabetic properties.

New cromones from Cnidium monnieri fruits inhibit adipocyte differentiation in 3T3-L1 cells

New cromones from Cnidium monnieri fruits inhibit adipocyte differentiation in 3T3-L1 cells

Syzygium aromaticum ethanol extract reduces high-fat diet-induced obesity in mice through downregulation of adipogenic and lipogenic gene expression

Numerous medicinal plants and their derivatives have been reported to prevent obesity and related diseases. Although Syzygium aromaticum has traditionally been used as an anodyne, carminative and anthelmintic in Asian countries, its potential in the prevention and treatment of obesity has not yet been explored. Therefore, the present study investigated the anti-obesity effect of S. aromaticum ethanol extract (SAE) both in vitro and in vivo. To evaluate the anti-obesity potential of SAE in vitro, the effect of SAE treatment on adipocyte differentiation in 3T3-L1 cells was investigated. To evaluate its potential in vivo, mice were assigned to three groups: a group fed the American Institute of Nutrition AIN-76A diet (normal group), an experimental group fed a high-fat diet (HFD group) and an experimental group fed an HFD supplemented with 0.5% (w/w) SAE (HFD + SAE group). After 9 weeks of feeding, the body weight; white adipose tissue (WAT) mass; serum triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, glucose, insulin and leptin; hepatic lipid accumulation; and levels of lipid metabolism-related genes in the liver and WAT were measured. In vitro investigation of the effect of SAE treatment on 3T3-L1 cells revealed that it had efficiently inhibited the conversion of cells into adipocytes in a dose-dependent manner. In vivo investigation revealed that SAE supplementation had significantly decreased HFD-induced increases in the body weight, liver weight, WAT mass, and serum TG, TC, lipid, glucose, insulin and leptin levels. Consistent with its effects on liver weight and WAT mass, SAE supplementation was found to have suppressed the expression of lipid metabolism-related proteins, including SREBP-1, FAS, CD36 and PPARγ in the liver and WAT, in addition to downregulating mRNA levels of transcription factors including Srebp and Pparg. SAE inhibits fat accumulation in HFD-fed mice via the suppression of transcription factors integral to adipogenesis and lipogenesis, suggesting its potential in preventing obesity.

Compound K, a novel ginsenoside metabolite, inhibits adipocyte differentiation in 3T3-L1 cells: Involvement of angiogenesis and MMPs

Compound K, a novel ginsenoside metabolite formed by intestinal bacteria, is shown to inhibit angiogenesis and matrix metalloproteinase (MMP) activities. Since growth and development of adipose tissue are thought to require adipogenesis, angiogenesis, and extracellular matrix remodeling, we investigated whether compound K inhibits adipocyte differentiation and its potential mechanisms. Treatment of 3T3-L1 adipocytes with compound K inhibited lipid accumulation and expression of adipocyte-specific genes (i.e., PPARγ, leptin, aP2, and C/EBPα). Compound K decreased mRNA levels of angiogenic factors (i.e., VEGF-A and FGF-2) and MMPs (i.e., MMP-2 and MMP-9), whereas it increased mRNA levels of angiogenic inhibitors (TSP-1, TIMP-1, and TIMP-2) in 3T3-L1 cells. MMP-2 and MMP-9 activities were also decreased in compound K-treated cells. These results demonstrate that compound K effectively inhibited adipogenesis and that this process may be mediated in part through changes in the expression of genes involved in angiogenesis and MMP system. Thus, by suppressing adipogenesis, compound K likely has therapeutic potential for the treatment of obesity and related disorders.

Piperine, a Component of Black Pepper, Inhibits Adipogenesis by Antagonizing PPARγ Activity in 3T3-L1 Cells

This study investigated the antiadipogenic activity of black pepper extract and its constituent piperine in 3T3-L1 preadipocytes as well as the underlying molecular mechanisms. Both black pepper extract and piperine, without affecting cytotoxicity, strongly inhibited the adipocyte differentiation of 3T3-L1 cells. The mRNA expression of the master adipogenic transcription factors, PPARγ, SREBP-1c, and C/EBPβ, was markedly decreased. Intriguingly, mRNA levels of PPARγ target genes were also down-regulated. Moreover, a luciferase reporter assay indicated that pipierine significantly represses the rosiglitazone-induced PPARγ transcriptional activity. Finally, GST-pull down assays demonstrated that piperine disrupts the rosiglitazone-dependent interaction between PPARγ and coactivator CBP. Genome-wide analysis using microarray further supports the role of piperine in regulating genes associated with lipid metabolism. Overall, these results suggest that piperine, a major component of black pepper, attenuates fat cell differentiation by down-regulating PPARγ activity as well as suppressing PPARγ expression, thus leading to potential treatment for obesity-related diseases.