Down-regulation Of Adipogenic Transcription Factors Research Articles

Strongylocentrotus intermedius Extract Suppresses Adiposity by Inhibiting Adipogenesis and Promoting Adipocyte Browning via AMPK Activation in 3T3-L1 Cells.

The current study aimed to determine whether Strongylocentrotus intermedius (S. intermedius) extract (SIE) exerts anti-obesity potentials employing 3T3-L1 cells as in vitro model. Herein we reported that treatment of SIE for 6 days reduced lipid accretion and triglyceride content whereas it increased the release of free glycerol. The inhibited lipid accumulation and induced lipolysis were evidenced by the downregulation of lipogenesis proteins, such as fatty acid synthase and lipoprotein lipase, and the upregulation of hormone-sensitive lipase expression. Furthermore, the downregulation of adipogenic transcription factors, including peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein α, and sterol regulatory element-binding protein 1, highlights that reduced lipid accumulation is supported by lowering adipocyte differentiation. Additionally, treatment activates brown adipocyte phenotype in 3T3-L1 cells by inducing expression of brown adipose tissue-specific proteins, such as uncoupling protein 1 and peroxisome proliferator-activated receptor-γ coactivator 1α. Moreover, SIE induced the phosphorylation of AMP-activated protein kinase (AMPK). The pharmacological approach using AMPK inhibitor revealed that the restraining effect of SIE on adipogenesis and promotion of adipocyte browning were blocked. In GC-MS analysis, SIE was mainly composed of cholest-5-en-3-ol (36.71%) along with saturated and unsaturated fatty acids which have favorable anti-obesity potentials. These results reveal that SIE has the possibility as a lipid-lowering agent for the intervention of obesity.

Effect of Metformin and Simvastatin in Inhibiting Proadipogenic Transcription Factors.

Obesity is a multifactorial chronic disease characterized by the excessive accumulation of fat in adipose tissue driven by hypertrophy and hyperplasia of adipocytes through adipogenesis. Adipogenesis plays a key role in the development of obesity and related metabolic disorders, which makes it potential target for the therapeutic approach to obesity. An increasing number of studies confirm the pleiotropic action of the combined treatment with metformin and statins, suggesting their anti-hypertensive, anti-inflammatory, and anti-adipogenic effect. The aim of this study was to analyze the effect of different doses of metformin (MET) and simvastatin (SIM) on the expression of key transcription factors of adipogenesis. Mouse 3T3-L1 preadipocytes were induced to differentiation in adipogenic medium with sustained MET and SIM treatment to assess the effect on adipogenesis. Nine days after initiating adipogenesis, the cells were prepared for further experiments, including Oil Red O staining, RT-PCR, Western blotting, and immunocytochemistry. Treating the cells with the combination of MET and SIM slightly reduced the intensity of Oil Red O staining compared with the control group, and down-regulated mRNA and protein expression of PPARγ, C/EBPα, and SREBP-1C. In conclusion, the inhibitory effect of MET and SIM on adipocyte differentiation, as indicated by decreased lipid accumulation, appears to be mediated through the down-regulation of adipogenic transcription factors, peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding pro-tein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP-1C).

Sinensol-C Isolated from Spiranthes sinensis Inhibits Adipogenesis in 3T3-L1 Cells through the Regulation of Adipogenic Transcription Factors and AMPK Activation.

Obesity is an abnormal medical condition caused by accumulation of body fat that presents negative health impacts. Adipocyte hyperplasia, also known as adipogenesis, is one of the major manifestations of obesity. In the present study, we isolated six phenanthrene derivatives (compounds 1–6) from the ethyl acetate fraction of Spiranthes sinensis and investigated their anti-adipogenic activity. We found that among the six phenanthrene derivatives, compound 6 (sinensol-C) exhibited strong inhibitory activity against intracellular lipid accumulation in 3T3-L1 adipocytes, with an IC50 value of 12.67 μM. Sinensol-C remarkably suppressed the accumulation of lipid droplets and adipogenesis, via down-regulation of adipogenic transcription factors, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), sterol regulatory element binding protein-1 (SREBP-1c), fatty acid synthase (FAS), and fatty acid binding protein 4 (FABP4), during adipocyte differentiation in 3T3-L1 cells. In addition, treatment with sinensol-C significantly increased the adenosine monophosphate-activated protein kinase (AMPK) activity in 3T3-L1 cells. Taken together, these data strongly suggest that sinensol-C regulates adiogenesis via down-regulation of adipogenic transcription factors and up-regulation of AMPK. Furthermore, this is the first study that demonstrates that sinensol-C has the capacity to modulate adipogenesis.

Indole-3-carbinol alleviates carbon tetrachloride-induced liver injury by inhibiting inflammatory response and regulating lipid metabolism

The hepatoprotective effects of indole-3-carbinol (I3C), one of the byproducts of the breakdown of glucosinolate glucobrassicin, were examined in mice with carbon tetrachloride (CCl4)-induced hepatotoxicity. I3C was administered orally at a dose of 50 or 100 mg/kg to C57BL/6 mice for 3 consecutive days with or without a subsequent single oral administration of CCl4 (1.5 mL/kg). I3C treatment significantly suppressed the increases in alanine aminotransferase and aspartate aminotransferase levels in the sera of CCl4-injured mice. In addition, I3C treatment markedly suppressed CCl4-induced hepatic inflammation, by suppressing the activation of macrophages and Kupffer cells in the liver. To examine the effects of I3C on lipid accumulation, 3T3-L1 pre-adipocytes were differentiated with I3C or vehicle control. I3C treatment reduced lipid accumulation, which appeared to be associated with the downregulation of adipogenic transcription factors, such as CCAAT/enhancer-binding protein α, peroxisome proliferator-activated receptor γ, and lipid accumulation-related genes, including adipocyte protein-2. Taken together, the present study suggest that I3C treatment reduces hepatocyte death and lipid accumulation in hepatocytes in CCl4-induced hepatic injury with concurrent suppression of macrophages/Kupffer cells, which was further evidenced by I3C-treated pre-adipocytes in vitro, through downregulation of lipid metabolism.

Fermented black radish (Raphanus sativus L. var. niger) attenuates methionine and choline deficient diet-induced nonalcoholic fatty liver disease in mice.

As one of the wide‐ranging form of chronic liver disease, there are only limited therapeutic options for nonalcoholic fatty liver disease (NAFLD). We evaluated whether fermented black radish (Raphanus sativus L. var. niger; FBR) ameliorates lipid accumulation, inflammation, and hepatic fibrosis, which are characteristics of the pathogenesis of NAFLD. Fermented black radish treatment reduced lipid accumulation in 3T3‐L1 adipocytes, which appeared to be associated with the downregulation of adipogenic transcription factors, including sterol regulatory element‐binding protein 1c, CCAAT/enhancer‐binding protein α, peroxisome proliferator‐activated receptor γ, and lipid accumulation‐related genes including adipocyte protein‐2 and fatty acid synthase. Administration of FBR to C57BL/6J mice challenged with methionine and choline deficient (MCD) diet significantly attenuated the increased serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and triglyceride. In addition, treatment with FBR interestingly repressed the hepatic inflammation induced with MCD diet, by lowering the expression of inducible nitric oxide synthase and suppressing the inactivation of macrophages and Kupffer cells in the liver. Fermented black radish was also shown to mitigate liver fibrosis through the inhibition of alpha‐smooth muscle actin, transforming growth factor beta‐1, and collagen type I alpha 1 chain. Our results indicate that FBR ameliorates NAFLD and its related metabolic disease by regulating multiple pathways, suggesting that FBR may be an effective dietary supplement for ameliorating NAFLD.

Suppression of adipocyte differentiation and lipid accumulation by stearidonic acid (SDA) in 3T3-L1 cells

BackgroundIncreased consumption of omega-3 (ω-3) fatty acids found in cold-water fish and fish oil has been reported to protect against obesity. A potential mechanism may be through reduction in adipocyte differentiation. Stearidonic acid (SDA), a plant-based ω-3 fatty acid, has been targeted as a potential surrogate for fish-based fatty acids; however, its role in adipocyte differentiation is unknown. This study was designed to evaluate the effects of SDA on adipocyte differentiation in 3T3-L1 cells.Methods3T3-L1 preadipocytes were differentiated in the presence of SDA or vehicle-control. Cell viability assay was conducted to determine potential toxicity of SDA. Lipid accumulation was measured by Oil Red O staining and triglyceride (TG) quantification in differentiated 3T3-L1 adipocytes. Adipocyte differentiation was evaluated by adipogenic transcription factors and lipid accumulation gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Fatty acid analysis was conducted by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS).Results3T3-L1 cells treated with SDA were viable at concentrations used for all studies. SDA treatment reduced lipid accumulation in 3T3-L1 adipocytes. This anti-adipogenic effect by SDA was a result of down-regulation of mRNA levels of the adipogenic transcription factors CCAAT/enhancer-binding proteins alpha and beta (C/EBPα, C/EBPβ), peroxisome proliferator-activated receptor gamma (PPARγ), and sterol-regulatory element binding protein-1c (SREBP-1c). SDA treatment resulted in decreased expression of the lipid accumulation genes adipocyte fatty-acid binding protein (AP2), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD-1), lipoprotein lipase (LPL), glucose transporter 4 (GLUT4) and phosphoenolpyruvate carboxykinase (PEPCK). The transcriptional activity of PPARγ was found to be decreased with SDA treatment. SDA treatment led to significant EPA enrichment in 3T3-L1 adipocytes compared to vehicle-control.ConclusionThese results demonstrated that SDA can suppress adipocyte differentiation and lipid accumulation in 3T3-L1 cells through down-regulation of adipogenic transcription factors and genes associated with lipid accumulation. This study suggests the use of SDA as a dietary treatment for obesity.

Aged citrus peel (chenpi) extract reduces lipogenesis in differentiating 3T3-L1 adipocytes

Aged citrus peel (chenpi) is made from the dry peel of the fruit of Citrus reticulate Blanco after aging process. It has long been used as a food ingredient, a dietary supplement, and for medicinal purpose. Compared to fresh citrus peel extract, chenpi extract contains more 5-demethylated polymethoxyflavones (5-OH PMFs). To investigate a potential direct role of chenpi extract on adipose tissue, we examined the effect of chenpi extract on differentiating 3T3-L1 cells. We showed that two types of chenpi extract varying in 5-OH PMF contents consistently reduces intracellular lipid accumulation without significantly affecting cell viability and proliferation. The reduction in lipid accumulation is correlated with AMP-activated protein kinase (AMPK) activation and down-regulation of adipogenic transcription factors as well as lipogenic genes. The results indicate that chenpi extract may directly affect lipogenesis in adipose tissue and the content of 5-OH PMFs likely affects the anti-lipogenic activity of chenpi extract.

TRAIL (TNF-related apoptosis-inducing ligand) inhibits human adipocyte differentiation via caspase-mediated downregulation of adipogenic transcription factors.

Tumor necrosis factor-α (TNFα) and other ligands of the TNF superfamily are potent regulators of adipose tissue metabolism and play a crucial role in the obesity-induced inflammation of adipose tissue. Adipose tissue expression levels of TRAIL (TNF-related apoptosis-inducing ligand) and its receptor were shown to be upregulated by overfeeding and decreased by fasting in mice. In the present study we aimed to elucidate the impact of TRAIL on adipogenesis. To this end, human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes as well as stromal-vascular cells isolated from human white adipose tissue were used as model systems. Human recombinant TRAIL inhibited adipogenic differentiation in a dose-dependent manner. It activated the cleavage of caspase-8 and -3, which in turn resulted in a downregulation of the key adipogenic transcription factors C/EBPα, C/EBPδ, and PPARγ. The effect was completely blocked by pharmacological or genetic inhibition of caspases. Taken together we discovered a so far unrecognized function of TRAIL in the regulation of adipogenesis. Targeting the TRAIL/TRAIL receptor system might provide a novel strategy to interfere with adipose tissue homeostasis.

An isoflavone cladrin prevents high-fat diet-induced bone loss and inhibits the expression of adipogenic gene regulators in 3T3-L1 adipocyte.

This study evaluates the effect of isoflavone cladrin on high-fat diet (HFD)-induced bone loss and adipogenesis. Thirty-two 4-week-old male C57BL/6J mice were divided into four groups: a standard diet group, a HFD group and HFD group with cladrin (5 and 10 mg/kg per day orally) for 12 weeks. The effect of cladrin on bone micro-architecture, bone marrow cell lineages and hyperlipidaemia were assessed. For assessing anti-adipogenic activity of cladrin, 3T3-L1 cells were used. Cladrin attenuated HFD-induced hyperlipidaemia and bone loss by preserving bone micro-architecture and strength. Effect of cladrin was found at the level of bone marrow progenitor cells. Gene expression profile of cladrin-treated mice bone showed upregulation of osteoblast and downregulation of adipogenic transcription factors and increased OPG/RANKL ratio. Cladrin inhibited cellular lipid accumulation through downregulation of transcription factors such as PPAR-γ and C/EBP-α and modulated the expression of major adipokines involved behind obesity stimulation without eliciting cell cytotoxicity in 3T3-L1 adipocytes. We conclude that cladrin may improve obesity-induced bone loss and hyperlipidaemia in mice fed HFD and adipogenesis in 3T3-L1 cells by modifying adipokines and could offer clinical benefits as a supplement to treat obesity-induced disorders.

Assessment of the pectolinarin content and the radical scavenging-linked antiobesity activity of Cirsium setidens Nakai extracts

Cirsium setidens Nakai contains bioactive compounds that exert biological activities. Method validation for analysis of the pectolinarin content in Cirsium setidens extracts (CSE) and radical scavenging-linked antiobesity activities using 3T3-L1 cells and C57BL/6 mice were performed. The pectolinarin content of CSE was 2.81±0.01 mg/g with a high degree of linearity in calibration curves (R2=0.9999). CSE exhibited free radical-scavenging activities and a reducing power. CSE and pectolinarin inhibited lipid accumulation during adipogenesis of 3T3-L1 cells via down-regulation of adipogenic transcription factors. CSE supplementation suppressed body weight in C57BL/6 mice fed a high fat diet and reduced plasma total cholesterol, triglyceride, insulin, and glucose levels. Pectolinarin-enriched CSE can be considered as a good source of natural antioxidants and antiobesity ingredients.

Anti-adipogenic effects in 3T3-L1 cells of acetone extracts and fractions from Styrax japonica fruit

Reduction in reactive oxygen species (ROS) production facilitated by Styrax japonica (SJ) extracts and fractions for inhibition of obesity development through inhibition of adipogenesis was investigated. Treatment of cells with SJ extracts and fractions did not result in changes in cell viability. SJ extracts and fractions inhibited lipid accumulation in a dose-dependent manner during adipogenesis. Expressions of PPARγ and C/EBPα, key adipogenic markers, were decreased in cells treated with SJ extracts and fractions. Inhibitory effects of SJ extracts and fractions were the most powerful in the early stages of differentiation (days 0-2). Intracellular ROS production was decreased in cells treated with SJ extracts and fractions. SJ extracts and fractions can inhibit adipogenesis via reduced ROS levels, which involves down-regulation of adipogenic transcription factors.

Flavonoids from Triticum aestivum inhibit adipogenesis in 3T3-L1 cells by upregulating the insig pathway.

The present study aimed to compare the potential anti-adipogenic effects and underlying mechanisms of the luteolin, isoscoparin and isoorientin flavonoids, purified from Triticum aestivum sprout (TA) in 3T3-L1 cells. The cells were treated with different concentrations of flavonoids for 8 days and the lipid accumulation was assessed using Oil-Red-O staining. The expression levels of the transcription factors and the genes involved in adipogenesis in the cells were assessed by reverse transcription-quantitative polymerase chain reaction and western blotting. The results demonstrated that 10 μM luteolin, isoscoparin or isoorientin inhibited lipid deposition in the cells by 74, 63 and 65%, respectively. The flavonoids also significantly inhibited the transcriptional regulators of adipogenesis, including peroxisome proliferator-activated receptor-γ, CAAT/enhancer binding protein-α and sterol regulatory element binding protein (SREBP)-1c, compared with the control cells. Similarly, there was a significant downregulation of the adipocyte specific markers associated with lipid metabolism, including activating protein-2, fatty acid synthase, hormone-sensitive lipase and lipoprotein lipase, in the flavonoid treated cells. Notably, the cells treated with the flavonoids demonstrated increased expression levels of the insulin-induced genes, insig-1 and insig-2, which may have inhibited the activation of the adipogenic transcription factor, SREBP, eventually leading to the inhibition of adipogenesis. Taken together, these results revealed that the flavonoids from TA possessed an inhibitory effect on adipogenesis through downregulation of adipogenic transcription factors and genes associated with lipid metabolism, and the upregulation of insig 1 and 2, suggesting that the flavonoids from TA may be potential therapeutic agents for the prevention and treatment of obesity.

<i>Trapa japonica</i> Flerov Extract Attenuates Lipid Accumulation through Downregulation of Adipogenic Transcription Factors in 3T3-L1 Cells

Obesity is a major human health problem associated with various diseases, including cardiac injury and type 2 diabetes. Trapa japonica Flerov (TJF) has been used in traditional oriental medicine to treat diabetes. In this study, we evaluated the inhibitory effect of and the mechanism underlying the effect of TJF extract on adipogenesis in 3T3-L1 cells. The effects of TJF extract on cell viability were analyzed using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, and the anti-adipogenic effect was measured by oil red O staining. The expression of peroxisomal proliferator activated receptor (PPAR)γ, CCAAT/enhancer-binding protein-α (C/EBP)α, adenosine monophosphate-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), adiponectin, and fatty acid binding protein (FABP)4 involved in adipogenesis was determined by western blot analysis. TJF extract effectively inhibited lipid accumulation and the expression of PPARγ and C/EBPα in 3T3-L1 cells. TJF also increased the phosphorylation of AMPK and ACC, and decreased the expression of adiponectin and FABP4. These results indicate that TJF extract exerts its anti-obesity effect through the downregulation of adipogenic transcription factors and adipogenic marker genes.

Dioscin inhibits adipogenesis through the AMPK/MAPK pathway in 3T3-L1 cells and modulates fat accumulation in obese mice.

Dioscin (DS) is a steroidal saponin present in a number of medicinal plants and has been shown to exert anticancer, antifungal and antiviral effects. The present study aimed to deternube the effects DS on the regulation of adipogenesis and to elucidate the underlying mechanisms. In vitro experiments were performed using differentiating 3T3-L1 cells treated with various concentrations (0-4 µM) of DS for 6 days. A cell viability assay was performed on differentiating cells following exposure to DS. Oil Red O staining and triglyceride content assay were performed to evaluate the lipid accumulation in the cells. We also carried out the following experiments: i) flow cytometry for cell cycle analysis, ii) quantitative reverse transcription polymerase chain reaction for measuring adipogenesis-related gene expression, and iii) western blot analysis to measure the expression of adipogenesis transcription factors and AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC) and mitogen-activated protein kinase (MAPK) phosphorylation. In vivo experiements were performed using mice with obesity induced by a high-fat diet (HFD) that were treated with or without DS for 7 weeks. DS suppressed lipid accumulation in the 3T3-L1 cells without affecting viability at a dose of up to 4 µM. It also delayed cell cycle progression 48 h after the initiation of adipogenesis. DS inhibited adipocyte differentiation by the downregulation of adipogenic transcription factors and attenuated the expression of adipogenesis-associated genes. In addition, it enhanced the phosphorylation of AMPK and its target molecule, ACC, during the differentiation of the cells. Moreover, the inhibition of adipogenesis by DS was mediated through the suppression of the phosphorylation of MAPKs, such as extracellular-regulated kinase 1/2 (ERK1/2) and p38, but not c-Jun-N-terminal kinase (JNK). DS significantly reduced weight gain in the mice with HFD-induced obesity; this was evident by the suppression of fat accumulation in the abdomen. the present study reveals an anti-adipogenic effect of DS in vitro and in vivo and highlights AMPK/MAPK signaling as targets for DS during adipogenesis.

Sphingosine-1-phosphate inhibits the adipogenic differentiation of 3T3-L1 preadipocytes.

Sphingosine-1-phosphate (S1P) is a pluripotent lipid mediator that transmits signals through G-protein-coupled receptors to control diverse biological processes. The novel biological activity of S1P in the adipogenesis of 3T3-L1 preadipocytes was identified in the present study. S1P significantly decreased lipid accumulation in maturing preadipocytes in a dose‑dependent manner. In order to understand the anti‑adipogenic effects of S1P, preadipocytes were treated with S1P, and the change in the expression of several adipogenic transcription factors and enzymes was investigated using quantitative RT-PCR. S1P downregulated the transcriptional levels of the peroxisome proliferator-activated receptor γ, CCAAT/enhancer binding proteins and adiponectin, which are markers of adipogenic differentiation. The effects of S1P on the levels of mitogen‑activated protein kinase (MAPK) signals in preadipocytes were also investigated. The activation of JNK and p38 were downregulated by S1P treatment in human preadipocytes. In conclusion, the results of this study suggest that S1P alters fat mass by directly affecting adipogenesis. This is mediated by the downregulation of adipogenic transcription factors and by inactivation of the JNK and p38 MAPK pathways. Thus, selective targeting of the S1P receptors and sphingosine kinases may have clinical applications for the treatment of obesity.

Guava Leaf Extracts Inhibit 3T3-L1 Adipocyte Differentiation Via Activating AMPK

The guava tree (psidium guajava linn.) is commonly used not only as food but also as folk medicine. In our previous studies, we showed that oral administration of guava leaf extracts (GLE) had beneficial anti-obesity effects using metabolic syndrome model rats. However, we did not clarify molecular mechanism by which GLE administration leads to anti-obesity effect. This study was designed to evaluate the mechanism of anti-obesity by GLE using 3T3-L1 pre-adipocyte cell lines. We found that GLE significantly inhibited 3T3-L1 differentiation via down-regulation of adipogenic transcription factors and markers. Mitotic clonal expansion, which is essential for adipose differentiation, was also depressed in the early phase. Interestingly, GLE increased the phosphorylation of AMPK on 3T3-L1 cells and, by pretreatment with AMPK siRNA, the GLE treatment group showed restored adipocyte differentiation. In conclusion, these results showed that GLE is capable of inhibiting adipocyte differentiation via AMPK activation and therefore it may prevent obesity in vivo.

Artemisia iwayomogiExtract Attenuates High-Fat Diet-Induced Obesity by Decreasing the Expression of Genes Associated with Adipogenesis in Mice

The objective of the present study was to determine whether Artemisia iwayomogi (AI) extract reduces visceral fat accumulation and obesity-related biomarkers in mice fed a high-fat diet (HFD), and if so, whether these effects are exerted by modulation of the expression of genes associated with adipogenesis and inflammation. AI extract supplementation for 11 weeks significantly prevented HFD-induced increments in body weight, visceral adiposity, adipocyte hypertrophy, and plasma levels of lipids and leptin. Additionally, AI extract supplementation resulted in downregulation of adipogenic transcription factors (PPARγ2 and C/EBPα) and their target genes (CD36, aP2, and FAS) in epididymal adipose tissue compared to the HFD alone. The AI extract effectively reversed the HFD-induced elevations in plasma glucose and insulin levels and the homeostasis model assessment of insulin resistance index. Furthermore, the extract significantly decreased gene expression of proinflammatory cytokines (TNFα, MCP1, IL-6, IFNα, and INFβ) in epididymal adipose tissue and reduced plasma levels of TNFα and MCP1 as compared to HFD alone. In conclusion, these results suggest that AI extract may prevent HFD-induced obesity and metabolic disorders, probably by downregulating the expression of genes related to adipogenesis and inflammation in visceral adipose tissue.

Inhibitory effect of galanolactone isolated from Zingiber officinale roscoe extract on adipogenesis in 3T3-L1 cells

Zingiber officinale Roscoe commonly known as ginger, has been used in traditional medicine. Inhibtion effect of galanolactone isolated from Z. officinale Roscoe on adipogenesis in 3T3-L1 cells was evaluated. Effect of galanolactone on 3T3-L1 adipocyte differentiation was measured by Oil Red O staining, and cytotoxicity effect of galanolactone was analyzed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. The expression of various genes involved in adipogenic action of galanolactone was determined by real-time PCR and Western blot. Peroxisome proliferator-activated receptor γ (PPARγ) luciferase transactivation assay was used to evaluate the PPARγ transcriptional activity of galanolactone in HEK 293T cells. Galanolactone inhibited lipid accumulation and expression of adipocyte fatty acid-binding protein (aP2) and resistin in a dose-dependent manner in 3T3-L1 cells. Treatment with 50 and 100 μM of galanolactone significantly decreased the troglitazone-induced PPARγ transcripitional activity in HEK 293T cells, and suppressed expressions of PPARγ and CCAAT-enhancer-binding protein α (C/EBPα) at mRNA and protein levels in 3T3-L1 cells. These findings suggest that galanolactone isolated from Z. officinale Roscoe exerts anti-obesity effect through downregulation of adipogenic transcription factors and adipogenic marker genes.

Phosphorylated glucosamine inhibits adipogenesis in 3T3-L1 adipocytes

Phosphorylated glucosamine (glucosamine-6-phosphate, PGlc) was synthesized using methanesulfonic acid, phosphorus pentoxide (P 2O 5), NH 2NH 2 and DMF. Its inhibitory effect on lipid accumulation in cultured 3T3-L1 adipocytes was investigated by measuring triglyceride contents and Oil Red O staining. In order to understand the mechanism by which lipid accumulation in adipocytes is decreased by PGlc, we examined the expression levels of several genes and proteins associated with adipogenesis and lipolysis using reverse transcription polymerase chain reaction, real-time polymerase chain reaction and Western blot analysis. Treatment with PGlc significantly reduced lipid accumulation during adipocyte differentiation and induced down-regulation of peroxisome proliferator-activated receptor-γ, sterol regulatory element binding protein 1 and CCAAT/enhancer binding protein-α in a dose-dependent manner. Moreover, treatment with PGlc during adipocyte differentiation induced significant up-regulation of preadipocyte factor 1 mRNA and down-regulation of such adipocyte-specific gene promoters as adipocyte fatty acid binding protein, fatty acid synthase, lipoprotein lipase and leptin. According to the lipolytic response, PGlc up-regulated hormone-sensitive lipase mRNA expression and suppressed the expression levels of tumor necrosis factor-α mRNA compared with fully differentiated adipose tissue. These results suggest that the inhibitory effect of PGlc on adipocyte differentiation might be mediated through the down-regulation of adipogenic transcription factors, such as peroxisome proliferator-activated receptor-γ, sterol regulatory element binding protein 1 and CCAAT/enhancer binding protein-α, which are related to the downstream adipocyte-specific gene promoters.