Effects of Sinensetin on Lipid Metabolism in Mature 3T3‐L1 Adipocytes

Sinensetin is a rare polymethoxylated flavone found in certain citrus fruits. In this study, we investigated the effects of sinensetin on lipid metabolism in mature 3T3‐L1 adipocytes. Sinensetin decreased the expression of sterol regulatory element‐binding protein 1c (SREBP1c), suggesting its antiadipogeneic property via downreguation of SREBP1c. Also, sinensetin increased the phosphorylation of protein kinase A and hormone‐sensitive lipase, indicating its lipolytic property via a cAMP‐mediated signaling pathway. Moreover, sinensetin inhibited insulin‐stimulated glucose uptake by decreasing the phosphorylation of insulin receptor substrate and Akt. Furthermore, sinensetin increased the phosphorylation of AMP‐activated protein kinase (AMPK) and acetyl‐CoA carboxylase. It also upregulated mRNA expression of carnitine palmitoyltransferase‐1a, suggesting that sinensetin enhances fatty acid β‐oxidation through the AMPK pathway. Taken together, these results suggest that sinensetin may have potential as a natural agent for prevention/improvement of obesity. Copyright © 2012 John Wiley & Sons, Ltd.     

Berberine inhibits SREBP‐1‐related clozapine and risperidone induced adipogenesis in 3T3‐L1 cells

Weight gain is a common and potentially serious complication associated with the treatment of second generation antipsychotics such as clozapine and risperidone. Increased peripheral adipogenesis via the SREBP‐1 pathway could be one critical mechanism responsible for antipsychotic drug‐induced weight gain. Berberine, a botanic alkaloid, has been shown in our previous studies to inhibit adipogenesis in cell and animal models. MTT was used to determine the cytotoxic effects of clozapine and risperidone in combination with berberine. Differentiation of 3T3‐L1 cells was monitored by Oil‐Red‐O staining and the expression of SREBP‐1 and related proteins was determined by real‐time RT‐PCR and western blotting. The results showed that neither clozapine nor risperidone, alone or in combination with berberine had significant effects on cell viability. Eight days treatment with 15 μm clozapine increased adipogenesis by 37.4% and 50 μm risperidone increased adipogenesis by 26.5% during 3T3‐L1 cell differentiation accompanied by increased SREBP‐1, PPARγ, C/EBPα, LDLR and Adiponectin gene expression. More importantly, the addition of 8 μm berberine diminished the induction of adipogenesis almost completely accompanied by down‐regulated mRNA and protein expression levels of SREBP‐1‐related proteins. These encouraging results may lead to the use of berberine as an adjuvant to prevent weight gain during second generation antipsychotic medication. Copyright © 2010 John Wiley & Sons, Ltd.     

Inhibitory effects of green tea catechin on the lipid accumulation in 3T3‐L1 adipocytes

The aim of the present study was to evaluate the effects of green tea (‐)‐epigallocatechin‐3‐gallate (EGCG) on the depletion of accumulated fat in differentiated 3T3‐L1 adipocytes. Intracellular lipid accumulation was decreased significantly after 24 h of incubation with 10 µm EGCG, while the viability of adipocytes was reported to be unaffected. Under the same experimental conditions, the amount of glycerol released from cells into the medium was increased by 10 µm EGCG. The level of mRNA in the 3T3‐L1 adipocytes was analysed by quantitative real‐time RT‐PCR. EGCG notably increased the mRNA level of hormone sensitive lipase (HSL), which catalyses the rate‐limiting stage in hydrolysis of stored triacylglycerol to monoacylglycerol and free fatty acids. In conclusion, the experiment produced results which showed that green tea EGCG effectively depleted fat accumulation via the stimulation of lipolysis and increased HSL gene expression in 3T3‐L1 adipocytes. These results may relate to the mechanism by which EGCG modulates lipolysis in adipocytes. Copyright © 2008 John Wiley & Sons, Ltd.     

齐墩果酸抑制3T3-L1脂肪细胞脂质堆积

目的：从57个中药化合物筛选具有抑制3T3-L1脂肪细胞脂质堆积的活性成分。方法：3T3-L1细胞培养至融合后用化合物进行干预,并诱导使其分化,采用高内涵影像方法检测细胞中脂滴含量。对发现的活性成分用ToxInsight体外毒性检测方法评价其肝毒性。结果：发现并验证活性成分齐墩果酸（OA）具有显著的脂质形成抑制作用,其半数抑制浓度（IC50）为14.5 μmol·L-1,且在60 μmol·L-1测试浓度范围内对HepG2 细胞无显著损伤作用。结论：OA 具有显著的降低脂质形成作用,是潜在的降脂候选化合物。     

Genistein suppresses adipogenesis of 3T3‐L1 cells via multiple signal pathways

Genistein, an isoflavone, was shown to have therapeutic effects for obesity, diabetes and cardiovascular diseases. This study investigated the effect and underlying mechanism of genistein on adipogenesis in 3T3‐L1 preadipocytes. Genistein inhibited lipid accumulation and decreased the nonesterified fatty acid (NEFA) content of 3T3‐L1 on day 6 after the induction of differentiation with methylisobutylxanthine, dexamethasone and insulin (MDI). Genistein recovered nitric oxide (NO) release suppressed by MDI and the results were consistent with the expression of endothelial NO synthase (eNOS) assayed by western blotting. Pretreatment with genistein inhibited the phosphorylation of p38 mitogen‐activated protein kinase (p38 MAPK) stimulated with 10 µg/mL of insulin. Furthermore, genistein inhibited the expression of fatty acid synthase (FAS) from 178% of the MDI group to 74%. SB203580, a p38 inhibitor, mimicked the FAS inhibition effect of genistein, suggesting that the inhibitory effect of genistein on FAS was partially via the p38 pathway. On the other hand, genistein abolished the phosphorylation of janus‐activated kinase 2 (JAK2) in response to MDI. AG490, a JAK2 inhibitor, suppressed the expression of CCAAT/enhancer binding protein alpha (C/EBPα), a marker of adipocyte differentiation. The findings suggest that genistein attenuates the differentiation of 3T3‐L1 involving multiple signal pathways. Copyright © 2008 John Wiley & Sons, Ltd.     

5‐Hydroxyferulic acid methyl ester isolated from wasabi leaves inhibits 3T3‐L1 adipocyte differentiation

To investigate the compounds present in wasabi leaves (Wasabia japonica Matsumura) that inhibit the adipocyte differentiation, activity‐guided fractionation was performed on these leaves. 5‐Hydroxyferulic acid methyl ester ( 1 : 5‐HFA ester), one of the phenylpropanoids, was isolated from wasabi leaves as a compound that inhibits the adipocyte differentiation. Compound 1 suppressed the intracellular lipid accumulation of 3T3‐L1 cells without significant cytotoxicity. Gene expression analysis revealed that 1 suppressed the mRNA expression of 2 master regulators of adipocyte differentiation, PPARγ and C/EBPα. Furthermore, 1 downregulated the expression of adipogenesis‐related genes, GLUT4, LPL, SREBP‐1c, ACC, and FAS. Protein expression analysis revealed that 1 suppressed PPARγ protein expression. Moreover, to investigate the relationship between the structure and activity of inhibiting the adipocyte differentiation, we synthesized 12 kinds of phenylpropanoid analog. Comparison of the activity among 1 and its analogs suggested that the compound containing the substructure that possess a common functional group at the ortho position such as a catechol group exhibits the activity of inhibiting the adipocyte differentiation. Taken together, our findings suggest that 1 from wasabi leaves inhibits adipocyte differentiation via the downregulation of PPARγ.     

Effect of Sutherlandia frutescens on the Lipid Metabolism in an Insulin Resistant Rat Model and 3T3‐L1 Adipocytes

High fat diet induced insulin resistance correlates with dyslipidaemia and ectopic fat deposits in skeletal muscle and liver. The effects of Sutherlandia frutescens, an antidiabetic medicinal plant, on lipid metabolism were evaluated in an insulin resistant (IR) rat model and in 3 T3‐preadipocytes. Wistar rats received normal diet (ND) or high fat diet (HFD). After the onset of IR in the HFD group, the rats were subdivided into two subgroups, which either continued with HFD or were treated with 50 mg S. frutescens/kg BW/day and HFD (HFD + SF). After 4 weeks, the HFD + SF rats had a significantly lower body weight than the HFD rats (p < 0.05). Blood plasma analysis showed a decrease in insulin, free fatty acids and triglycerides. Related changes in lipid parameters were observed in the liver, skeletal muscle and adipose tissue. To investigate the effects of S. frutescens on adipose tissue, 3 T3‐L1 cells were used as a model. Treatment with S. frutescens led to a decrease in triglyceride accumulation, whilst glucose consumption and lactate production were increased (p < 0.05). These results indicate that S. frutescens directly affects mitochondrial activity and lipid biosynthesis in adipose tissue and provide a mechanism by which S. frutescens can restore insulin sensitivity by modulating fatty acid biosynthesis. Copyright © 2012 John Wiley & Sons, Ltd.     

Bromophenol (5‐bromo‐3,4‐dihydroxybenzaldehyde) isolated from red alga Polysiphonia morrowii inhibits adipogenesis by regulating expression of adipogenic transcription factors and AMP‐activated protein kinase activation in 3T3‐L1 adipocytes

The aim of the present study was to investigate the effect of 5‐bromo‐3,4‐dihydroxybenzaldehyde (BD) isolated from Polysiphonia morrowii on adipogenesis and differentiation of 3T3‐L1 preadipocytes into mature adipocytes and its possible mechanism of action. Levels of lipid accumulation and triglyceride were significantly lower in BD treated cells than those in untreated cells. In addition, BD treatment reduced protein expression levels of peroxisome proliferator‐activated receptor‐γ, CCAAT/enhancer‐binding proteins α, and sterol regulatory element‐binding protein 1 compared with control (no treatment). It also reduced expression levels of adiponectin, leptin, fatty acid synthase, and fatty acid binding protein 4. AMP‐activated protein kinase activation was found to be one specific mechanism involved in the effect of BD. These results demonstrate that BD possesses inhibitory effect on adipogenesis through activating AMP‐activated protein kinase signal pathway.     

Reduction of Adipogenesis and Lipid Accumulation by Taraxacum officinale (Dandelion) Extracts in 3T3L1 Adipocytes: An in vitro Study

In this in vitro study, we have investigated the ability of Taraxacum officinale (dandelion) to inhibit adipocyte differentiation and lipogenesis in 3T3‐L1 preadipocytes. HPLC analysis of the three plant extracts used in this study—leaf and root extracts and a commercial root powder—identified caffeic and chlorogenic acids as the main phenolic constituents. Oil Red O staining and triglyceride levels analysis showed decreased lipid and triglyceride accumulation, respectively. Cytotoxicity was assessed with the MTT assay showing non‐toxic effect among the concentrations tested. DNA microarray analysis showed that the extracts regulated the expression of a number of genes and long non‐coding RNAs that play a major role in the control of adipogenesis. Taken together, our results indicate that the dandelion extracts used in this study may play a significant role during adipogenesis and lipid metabolism, and thus, supporting their therapeutic interest as potential candidates for the treatment of obesity. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of Diphlorethohydroxycarmalol Isolated From Ishige okamurae on Apoptosis in 3 t3‐L1 Preadipocytes

Obesity is an important issue in the world of public health and preventive medicine. Inhibition of proliferation of preadipocytes plays an important role in proposed antiobesity mechanisms. In this study, we investigated the effect of diphlorethohydroxycarmalol (DPHC) isolated from Ishige okamurae on the apoptotic pathway. The results showed that DPHC inhibited population growth in 3 T3‐L1 preadipocytes as assessed using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Flow cytometric analysis of 3 T3‐L1 preadipocytes showed that the number of early and late apoptotic cells increases in a dose‐dependent manner after exposure to DPHC, while the number of normal cells was reduced. Our findings indicate that the induction of apoptosis in 3 T3‐L1 preadipocytes by DPHC is mediated through the activation of caspase‐3, Bax, and caspase‐9, and then through the cleavage of poly(ADP‐ribose) polymerase and the down‐regulation of Bcl‐2. The data also indicated that treatment with DPHC inhibits histone deacetylase activity in 3 T3‐L1 preadipocytes. These results show that DPHC efficiently induces apoptosis in 3 T3‐L1 preadipocytes. Copyright © 2012 John Wiley & Sons, Ltd.     

Anti‐diabetic Activity of Swertiamarin is due to an Active Metabolite,Gentianine, that Upregulates PPAR‐γ Gene Expression in 3T3‐L1 cells

We have previously shown the anti‐diabetic effects of swertiamarin; however, pharmacokinetic analysis showed that swertiamarin had a plasma half‐life of 1.3 h. Gentianine is an active metabolite of swertiamarin that possesses a pharmacophoric moiety. The aim of this study was to explore the possibility whether the anti‐diabetic effect of swertiamarin is due to gentianine. Swertiamarin treatment had no significant effect on adipogenesis, or the mRNA expression of PPAR‐γ and GLUT‐4; however, there was a significant increase in the mRNA expression of adiponectin. On the other hand, treatment with gentianine significantly increased adipogenesis, which was associated with a significant increase in the mRNA expression of PPAR‐γ, GLUT‐4 and adiponectin. These findings suggest, for the first time, that the anti‐diabetic effect of swertiamarin is due to gentianine, an active metabolite of swertiamarin. Copyright © 2012 John Wiley & Sons, Ltd.