Downregulation Of PPARγ2 Research Articles

Antiadipogenesis of Oroxylum indicum (L.) Kurz Extract via PPARγ2 in 3T3-L1 Adipocytes.

Oroxylum indicum is regarded as a traditional food with medicinal properties and is used widely throughout Asia. It has previously been demonstrated that O. indicum extract (OIE) was able to suppress the differentiation of 3T3-L1 preadipocytes to adipocytes. However, the mechanism underlying the antiadipogenesis of this plant has not been fully investigated. The present study aimed to explore the impact of OIE at 50 to 200 μg mL−1 on the molecular mechanism involved in the antiadipogenic activity in 3T3-L1 cells at day 0 of their differentiation to adipocytes. The morphology and biochemistry of the cells on day 12 were investigated and compared to the relevant controls. Adiponectin was measured using enzyme-linked immunosorbent assay (ELISA). The mRNA expression of peroxisome proliferator-activated receptor-gamma 2 (PPARγ2), sterol regulatory element-binding proteins 1c (SREBP-1c), fatty acid synthetase (FAS), glucose transporter (GLUT4), and leptin in adipocytes was determined by real-time PCR. The results demonstrated that the OIE at 200 μg mL−1 exhibited strongest suppression on intracellular lipid accumulation. The levels of adiponectin were dramatically increased in the untreated adipocytes, whereas significantly decreased in the 200 μg mL−1 OIE-treated adipocytes (P < 0.05). Expression of the mRNAs revealed that OIE-treated adipocytes at 200 μg mL−1 significantly inhibited the expression of PPARγ2 and SREBP-1c and lowered the level of expression of GLUT4, FAS, and leptin compared to the control (P < 0.05). These findings suggest that OIE inhibits adipocyte differentiation along with the downregulation of PPARγ2, SREBP-1c, and GLUT4, leading to the decrease in the expression of FAS and adipokine (leptin and adiponectin). Thus, OIE might be developed for hyperlipidemia and obesity prevention.

Dietary supplementation with soy isoflavones or replacement with soy proteins prevents hepatic lipid droplet accumulation and alters expression of genes involved in lipid metabolism in rats

Accumulation of hepatic lipid droplet (HLD) is the hallmark pathology of non-alcoholic fatty liver disease (NAFLD). This study examined the effects of soy isoflavones (ISF) and different amounts of soy proteins on the accumulation of HLD, lipid metabolism and related gene expression in rats. Weanling Sprague-Dawley rats were fed diets containing either 20% casein protein without (D1) or with (D2) supplemental ISF (50mg/kg diet) or substitution of casein with increasing amounts of alcohol-washed soy protein isolate (SPI, 5, 10, and 20%; D3, D4, D5) for 90 days. Dietary casein (20%) induced accumulation of HLD in female, but not in male rats. Both soy proteins and ISF remarkably prevented the formation of HLD. Soy proteins lowered hepatic total cholesterol and triglyceride in a dose-dependent manner. Interestingly, soy proteins but not ISF significantly increased free fatty acids in the liver of the female rats compared to D1. Proteomic analysis showed that at least 3 enzymes involved in lipogenesis were down-regulated and 7 proteins related to fatty acid β-oxidation or lipolysis were up-regulated by soy protein over D1. Additionally, 9 differentially expressed proteins identified were related to amino acid metabolism, 5 to glycolysis and 2 to cholesterol metabolism. Dietary ISF and SPI markedly reduced hepatic-peroxisome-proliferator-activated receptor γ2 (PPARγ2) and fat-specific protein 27 (FSP27) in female rats. Overall, this study has shown that partial or full replacement of dietary casein by soy protein or supplementation with soy ISF can effectively prevent the accumulation of HLD. The potential molecular mechanism(s) involved might be due to suppression of lipogenesis and stimulation of lipolysis and down-regulation of PPARγ2 and FSP27. This suggests that consumption of soy foods or supplements might be a useful strategy for the prevention or treatment of fatty liver diseases.

Protein tyrosine phosphatase 1B inhibits adipocyte differentiation and mediates TNFα action in obesity

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of systemic glucose and insulin homeostasis; however, its exact role in adipocytes is poorly understood. This study was to elucidate the role of PTP1B in adipocyte differentiation and its implication in obesity. During differentiation of 3T3-L1 white preadipocytes, PTP1B decreased progressively with adipocyte maturation. Lentivirus-mediated PTP1B overexpression in preadipocytes delayed adipocyte differentiation, shown as lack of mature adipocytes, low level of lipid accumulation, and down-regulation of main markers (PPARγ2, SREBP-1c, FAS and LPL). In contrast, lentivirus-mediated PTP1B knockdown accelerated adipocyte differentiation, demonstrated as full of mature adipocytes, high level of lipid accumulation, and up-regulation of main markers. Dominant-negative inhibition on endogenous PTP1B by lentivirus-mediated overexpression of PTP1B double mutant in Tyr-46 and Asp-181 residues (LV-D/A-Y/F) also stimulated adipogenesis, more efficient than PTP1B knockdown. Diet-induced obesity mice exhibited an up-regulation of PTP1B and TNFα accompanied by a down-regulation of PPARγ2 in white adipose tissue. TNFα recombinant protein impeded PTP1B reduction and inhibited adipocyte differentiation in vitro; this inhibitory effect was prevented by LV-D/A-Y/F. Moreover, PTP1B inhibitor treatment improved adipogenesis and suppressed TNFα in adipose tissue of obese mice. All together, PTP1B negatively regulates adipocyte development and may mediate TNFα action to impair adipocyte differentiation in obesity. Our study provides novel evidence for the importance of PTP1B in obesity and for the potential application of PTP1B inhibitors.

Berberine Improves Insulin Sensitivity by Inhibiting Fat Store and Adjusting Adipokines Profile in Human Preadipocytes and Metabolic Syndrome Patients

Berberine is known to inhibit the differentiation of 3T3-L1 cells in vitro, improve glycemic control, and attenuate dyslipidemia in clinical study. The aim of this study was to investigate the effects of berberine on preadipocytes isolated from human omental fat and in metabolic syndrome patients treated with berberine for 3 months. We have shown that treatment with 10 μM berberine resulted in a major inhibition of human preadipocyte differentiation and leptin and adiponectin secretion accompanied by downregulation of PPARγ2, C/EBPα, adiponectin, and leptin mRNA expression. After 3 months of treatment, metabolic syndrome patients showed decrease in their BMI (31.5 ± 3.6 versus 27.4 ± 2.4 kg/m2) and leptin levels (8.01 versus 5.12 μg/L), as well as leptin/adiponectin ratio and HOMA-IR. These results suggest that berberine improves insulin sensitivity by inhibiting fat store and adjusting adipokine profile in human preadipocytes and metabolic syndrome patients.

Sida rhomboidea. Roxb Leaf Extract Down-Regulates Expression of PPARγ2 and Leptin Genes in High Fat Diet Fed C57BL/6J Mice and Retards in Vitro 3T3L1 Pre-Adipocyte Differentiation

Sida rhomboidea. Roxb leaf extract (SRLE) is being used by the populace of North-East India to alleviate symptoms of diabetes and obesity. We have previously reported its hypolipidemic and anti-diabetic properties. In this study, we report the effect of SRLE on (i) in vivo modulation of genes controlling high fat diet (HFD) induced obesity and (ii) in vitro 3T3L1 pre-adipocyte differentiation and leptin release. Supplementation with SRLE significantly prevented HFD induced increment in bodyweight, plasma lipids and leptin, visceral adiposity and adipocyte hypertrophy. Also, SRLE supplementation reduced food intake, down regulated PPARγ2, SREBP1c, FAS and LEP expressions and up-regulated CPT-1 in epididymal adipose tissue compared to obese mice. In vitro adipogenesis of 3T3L1 pre-adipocytes was significantly retarded in the presence of SRLE extract. Also decreased triglyceride accumulation, leptin release and glyceraldehyde-3-Phosphate dehydrogenase activity along with higher glycerol release without significant alteration of viability of 3T3L1 pre-adipocytes, was recorded. Our findings suggest that prevention of HFD induced visceral adiposity is primarily by down regulation of PPARγ2 and leptin gene expression coupled with attenuation of food intake in C57BL/6J mice. SRLE induced prevention of pre-adipocytes differentiation, and leptin release further substantiated these findings and scientifically validates the potential application of SRLE as a therapeutic agent against obesity.

Anti-obesity potential of Clerodendron glandulosum.Coleb leaf aqueous extract

Clerodendron glandulosum.Coleb leaf aqueous extract (CG) is traditionally used by people of North-East India to alleviate symptoms of diabetes, obesity and hypertension. Previous study from our laboratory have documented anti-diabetic and anti-hypertensive properties of CG extract but, till date there are no pharmacological studies available on its anti-obesity potential. This inventory investigates the underlining molecular mechanism/s of CG induced regulation of in vivo HFD induced obesity and in vitro adipocyte differentiation. To evaluate effects of CG extract on (i) expression of genes regulating visceral adiposity and (ii) in vitro adipocyte differentiation and LEP release. Body weight, lee index, plasma lipids and LEP, mRNA expression of PPARγ-2, SREBP1c, FAS, CPT-1 and LEP in epididymal adipose tissue of control and experimental groups were evaluated. Also, potential of CG extract on in vitro adipocyte differentiation and LEP release was assessed. Supplementation of CG extract to HFD fed mice significantly prevented HFD induced increment in bodyweight, lee index, plasma lipids and LEP, visceral adiposity and adipocyte hypertrophy. Also, CG extract supplementation resulted in down regulation of PPARγ-2, SREBP1c, FAS and LEP expression along with up-regulation of CPT-1 in epididymal adipose tissue compared to HFD fed mice. In vitro study recorded significant anti-adipogenic effect of CG extract that resulted in decreased adipogenesis, TG accumulation, LEP release, G3PDH activity along with higher glycerol release without significantly altering viability of 3T3L1 pre-adipocytes. Clerodendron glandulosum.Coleb extract prevents adipocyte differentiation and visceral adiposity by down regulation of PPARγ-2 related genes and Lep expression thus validating its traditional therapeutic use in controlling obesity.

Compressive force inhibits adipogenesis through COX-2-mediated down-regulation of PPARγ2 and C/EBPα

Various mechanical stimuli affect differentiation of mesoderm-derived cells such as osteoblasts or myoblasts, suggesting that adipogenesis may also be influenced by mechanical stimulation. However, effects of mechanical stimuli on adipogenesis are scarcely known. Compressive force was applied to a human preadipocyte cell line, SGBS. Levels of gene expression were estimated by real-time reverse transcription-polymerase chain reaction. The accumulation of lipids was evaluated by Sudan III or Oil Red O staining. In SGBS cells subjected to a compressive force of 226 Pa for 12 h before adipogenic induction, adipogenesis was inhibited. Compressive force immediately after adipogenic induction did not affect the adipogenesis. The expression of peroxisome proliferator-activated receptor (PPAR) gamma2 and CCAAT/enhancer binding protein (C/EBP) alpha mRNA during adipogenesis was inhibited by compressive force, whereas C/EBPbeta and C/EBPdelta mRNA levels were unaffected. In preadipocytes, compressive force increased mRNA levels of Krüppel-like factor 2, preadipocyte factor 1, WNT10b, and cyclooxygenase-2 (COX-2) which are known as negative regulators for the PPARgamma2 and C/EBPalpha genes. Furthermore, a COX-2 inhibitor completely reversed the inhibition of adipogenesis by compressive force. In conclusion, compressive force inhibited adipogenesis by suppressing expression of PPARgamma2 and C/EBPalpha in a COX-2-dependent manner.

Oncostatin M decreases adiponectin expression and induces dedifferentiation of adipocytes by JAK3- and MEK-dependent pathways

Adiponectin, an adipokine secreted from adipocytes, plays a crucial role in the regulation of glucose and lipid metabolism. In the present study, we examine the role of the IL-6 family of cytokines in the expression of adiponectin in human adipocytes derived from human adipose tissue-derived stromal cells. Oncostatin M (OSM), but not IL-6, attenuated the expression level of adiponectin dose- and time-dependently, and the inhibitory effect of OSM on adiponectin expression was as potent as that of TNF-α. The OSM-induced down-regulation of adiponectin expression was correlated with the down-regulation of PPARγ2 and lipoprotein lipase, markers for adipogenic differentiation, and depletion of intracellular lipid droplets, suggesting dedifferentiation of adipocytes in response to OSM. OSM induced phosphorylation of STAT1, and treatment of adipocytes with JAK3 inhibitor WHI-P131 or MEK inhibitor U0126, but not with JAK2 inhibitor AG490, prevented the activation of STAT1. Furthermore, the OSM-induced suppression of adiponectin expression and dedifferentiation of adipocytes were ameliorated by WHI-P131 or U0126, but not by AG490. These results suggest that OSM inhibits adiponectin expression by inducing dedifferentiation of adipocytes through signaling pathways involving JAK3 and MEK, but not JAK2.

Tea Catechin Suppresses Adipocyte Differentiation Accompanied by Down-regulation of PPARγ2 and C/EBPα in 3T3-L1 Cells

Obesity is a serious health problem, and its prevention is promoted through life style including diet and exercise. In this study, we investigated the suppressive effects of tea catechin on the differentiation of 3T3-L1 preadipocytes to adipocytes. (-)-Catechin 3-gallate (CG), (-)-epigallocatechin (EGC), (-)-epicatechin 3-gallate, and (-)-epigallocatechin 3-gallate at 5 muM suppressed intracellular lipid accumulation. The suppressive effects of CG and EGC were stronger than the others, and CG and EGC also suppressed the activity of glycerol-3-phosphate dehydrogenase as a differentiation marker. These catechins inhibited the expression of peroxisome proliferator-activated receptor (PPAR) gamma2 and CCAAT/enhancer-binding protein (C/EBP) alpha, both of which act as key transcription factors at an early stage of differentiation, followed by the expression of glucose transporter (GLUT) 4 at a later stage. In addition, the catechins did not affect the phosphorylation status of the insulin signal pathway. Thus, catechin suppressed adipocyte differentiation accompanied by the down-regulation of PPARgamma2, C/EBPalpha, and GLUT4. These results suggest that tea catechin prevents obesity through the suppression of adipocyte differentiation.