Prevents Adipocyte Differentiation Research Articles

Assessment of the Anti-Adipogenic Effect of Crateva religiosa Bark Extract for Molecular Regulation of Adipogenesis: In Silico and In vitro Approaches for Management of Hyperlipidemia Through the 3T3-L1 Cell Line.

This study aimed to determine the phytoconstituents of Crateva religiosa bark (CRB) and evaluate the hypolipidemic effect of bioactive CRB extract by preventing adipocyte differentiation and lipogenesis. After performing the preliminary phytochemicals screening, the antioxidant activity of CRB extracts was determined through a DPPH (2, 2-diphenyl-1-picrylhydrazyl) assay. Ethyl acetate extract (CREAE) and ethanol extract (CRETE) of CRB were selected for chromatographic evaluation. The antihyperlipidemic potential was analyzed by molecular docking through the PKCMS software platform. Further, a 3T3-L1 cell line study via In vitro sulforhodamine B assay and western blotting was performed to confirm the prevention of adipocyte differentiation and lipogenesis Results: The total phenolic contents in CREAE and CRETE were estimated as 29.47 and 81.19 μg/mg equivalent to gallic acid, respectively. The total flavonoid content was found to be 8.78 and 49.08 μg/mg, equivalent to quercetin in CREAE and CRETE, respectively. CRETE exhibited greater scavenging activity with the IC50 value of 61.05 μg/ mL. GC-MS analysis confirmed the presence of three bioactive molecules, stigmasterol, gamma sitosterol, and lupeol, in CRETE. Molecular docking studies predicted that the bioactive molecules interact with HMG-CoA reductase, PPARγ, and CCAAT/EBP, which are responsible for lipid metabolism. In vitro, Sulforhodamine B assays revealed that CRETE dose-dependently reduced cell differentiation and viability. Cellular staining using 'Oil Red O' revealed a decreased lipid content in the CRETE-treated cell lines. CRETE significantly inhibited the induction of PPARγ and CCAAT/EBP expression, as determined through protein expression via western blotting. The influence of CRETE on lipid metabolism in 3T3-L1 cells is potentially suggesting a new approach to managing hyperlipidemia.

The effects of Formoterol in preventing adipogenesis and obesity are mediated by PPARγ/C/EBPα axis and AMPK/PGC-1α pathway.

Recent work suggests that Formoterol could be involved in the metabolic regulation of adipose tissue. It's unknown whether Formoterol possesses an effect against adipogenesis. Here, we found that Formoterol prevented adipocyte differentiation by reducing lipid accumulation, evidenced by reduced Oil Red O staining, declined intracellular triglyceride level, and downregulation of adipogenic factors (PPAR-γ, C/EBPα, and Glut4) in differentiation medium (MDI) stimulated 3T3-L1 preadipocytes. The administration of Formoterol ameliorated obesity in high fat diet (HFD) fed mice, which was evidenced by decreased body weight and ratio of fat/body weight, reduced adipocyte size, and decreased visceral adipocyte tissue weight. Furthermore, the expression level of adipogenic factors in white adipocyte tissues of HFD-fed mice was greatly repressed by Formoterol. Lastly, thermogenic markers (p-AMPK/AMPK, PGC-1α, and UCP-1) were dramatically upregulated by Formoterol. Collectively, Formoterol prevented adipogenesis and obesity in obese mice by regulating the PPARγ/C/EBPα axis and the AMPK/PGC-1α pathway.

Scopolin Prevents Adipocyte Differentiation in 3T3-L1 Preadipocytes and Weight Gain in an Ovariectomy-Induced Obese Mouse Model.

Obesity is prevalent in modern human societies. We examined the anti-obesity effects of scopolin on adipocyte differentiation in preadipocyte 3T3-L1 cells and weight loss in an ovariectomy (OVX)-induced obese mouse model. Scopolin inhibited adipocyte differentiation and lipid accumulation in the preadipocyte cells by suppressing the transcription of adipogenic-related factors, including adiponectin (Adipoq), peroxisome proliferator-activated receptor gamma (Pparg), lipoprotein lipase (Lpl), perilipin1 (Plin1), fatty acid-binding protein 4 (Fabp4), glucose transporter type 4 (Slc2a4), and CCAAT/enhancer-binding protein alpha (Cebpa). In OVX-induced obese mice, administration of scopolin promoted the reduction of body weight, total fat percentage, liver steatosis, and adipose cell size. In addition, the scopolin-treated OVX mice showed decreased serum levels of leptin and insulin. Taken together, these findings suggest that the use of scopolin prevented adipocyte differentiation and weight gain in vitro and in vivo, indicating that scopolin may be a potential bioactive compound for the treatment and prevention of obesity in humans.

Celastrol regulates bone marrow mesenchymal stem cell fate and bone-fat balance in osteoporosis and skeletal aging by inducing PGC-1α signaling.

Celastrol has recently been identified as a prospective new treatment for obesity and several metabolic complications. However, the effect of Celastrol in osteoporosis (OP) remains unknown. In this study, we demonstrated that Celastrol promotes osteoblast differentiation and prevents adipocyte differentiation in bone marrow mesenchymal stem cells (BM-MSCs) in vitro. Mechanistically, Celastrol was able to control the differentiation of BM-MSCs by stimulating PGC-1α signaling. Moreover, administration of Celastrol could alleviate bone loss and bone marrow adipose tissue (MAT) accumulation in ovariectomized (OVX) mice and aged mice. Together, these results recommended that Celastrol could regulate BM-MSCs fate and bone-fat balance in OP and skeletal aging by stimulating PGC-1α, which might act as a possible therapeutic target for OP and for the prevention of skeletal aging.

Antiadipogenic Effects of Mixtures of Cornus officinalis and Ribes fasciculatum Extracts on 3T3-L1 Preadipocytes and High-Fat Diet-Induced Mice.

Medicinal plants have been used worldwide as primary alternative healthcare supplements. Cornus officinalis (CO) and Ribes fasciculatum (RF) are traditional medicinal plants applied in East Asia to treat human diseases such as hepatitis, osteoporosis, oxidative stress and allergy. The aim of this study was to examine the anti-obesity effect of CO and RF on preadipocyte 3T3-L1 cells in vitro and high-fat diet (HFD)-induced obesity mice in vivo. Combination treatment of CO and RF in differentiated 3T3-L1 cells inhibited adipocyte differentiation through downregulation of adipogenesis-associated genes such as CCAAT/enhancer-binding protein alpha (Cebpa), fatty acid binding protein 4 (Fabp4), peroxisome proliferator-activated receptor gamma (Pparg) and sterol regulatory element binding protein (Srebp1). In vivo animal models showed that a mixture of CO and RF inhibited HFD-induced weight gain, resulting in decreased abdominal visceral fat tissues and fatty hepatocyte deposition. In addition, CO+RF treatment decreased HFD-induced adipogenesis-associated genes in abdominal white fat tissue. These results suggest that administration of a CO and RF mixture prevented adipocyte differentiation and lipid accumulation in preadipocyte cells and HFD-induced body weight in obesity mice. Therefore, combined therapy of CO and RF may be a protective therapeutic agent against obesity.

The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

Previously, the V1-3 isoforms of the transient receptor potential channel (TRP) have been shown to promote or prevent adipocyte differentiation. In the current study, the C isoforms were screened for blocking adipogenesis. The hypothesis that the TRP classic or canonical (TRPC) deters adipocyte differentiation was investigated in 3T3-L1 cells employing the channel-specific activator and antagonist, silencing, and overexpression techniques. Fat accumulation in cells was visualized by Oil Red O staining. Intracellular calcium inflow was estimated by confocal microscopy. A high-fat (HF) feeding study was also performed on C57BL/6J mice to verify the findings in the cell model. Among the 6 C isoforms tested, only TRPC-6 inhibited the differentiation of fat cells. The phytochemical quercetin induced the channel protein expression. Calcium-imaging results also revealed that the flavonoid could trigger calcium inflow. Coadministration of quercetin (1 or 20 mg/kg body weight) in an HF diet prevented TRPC-6 from declining and attenuated phosphorylated (p)-PKB and PI3k, as well as the proliferation of visceral fat cells. The present study illustrated that TRPC-6 activation could perturb adipocyte differentiation. The food flavonoid quercetin was a TRPC-6 inducer and activator and it could prevent adipogenesis in mice.-Tan, Y. Q., Kwan, H. Y., Yao, X., Leung, L. K. The activity of transient receptor potential channel C-6 modulates the differentiation of fat cells.

A PDE1 inhibitor reduces adipogenesis in mice via regulation of lipolysis and adipogenic cell signaling

Vinpocetine, a phosphodiesterase (PDE) type-1 inhibitor, increases cAMP and cGMP levels and is currently used for the management of cerebrovascular disorders, such as stroke, cerebral hemorrhage, and cognitive dysfunctions. In this study, we first determined that vinpocetine effectively suppressed adipogenesis and lipid accumulation. However, we questioned which molecular mechanism is involved because the role of PDE in adipogenesis is still controversial. Vinpocetine decreased adipogenic cell signaling, including the phosphorylation of ERK, AKT, JAK2, and STAT3, and adipokine secretion, including IL-6, IL-10, and IFN-α. Interestingly, vinpocetine increased the phosphorylation of HSL, suggesting the induction of the lipolysis pathway. Moreover, vinpocetine increased UCP1 expression via increasing cAMP and PKA phosphorylation. The administration of vinpocetine with a normal-chow diet (NFD) or a high-fat diet (HFD) in mice attenuated body weight gain in mice fed both the NFD and HFD. These effects were larger in the HFD-fed mice, without a difference in food intake. Vinpocetine drastically decreased fat weight and adipocyte cell sizes in gonadal and inguinal white adipose tissues and in the liver in both diet groups. Serum triacylglycerol levels and fasting blood glucose levels were reduced by vinpocetine treatment. This study suggested that vinpocetine prevents adipocyte differentiation through the inhibition of adipogenesis-associated cell signaling in the early stages of adipogenesis. Moreover, upregulating cAMP levels leads to an increase in lipolysis and UCP1 expression and then inhibits lipid accumulation. Therefore, we suggest that vinpocetine could be an effective agent for treating obesity, as well as improving cognition and cardiovascular function in older individuals.

DLK1 Is a Novel Link Between Reproduction and Metabolism.

Delta-like homolog 1 (DLK1), also called preadipocyte factor 1, prevents adipocyte differentiation and has been considered a molecular gatekeeper of adipogenesis. A DLK1 complex genomic defect was identified in five women from a single family with central precocious puberty (CPP) and increased body fat percentage. We studied 60 female patients with a diagnosis of CPP or history of precocious menarche. Thirty-one of them reported a family history of precocious puberty. DLK1 DNA sequencing was performed in all patients. Serum DLK1 concentrations were measured using an ELISA assay in selected cases. Metabolic and reproductive profiles of adult women with CPP caused by DLK1 defects were compared with those of 20 women with idiopathic CPP. We identified three frameshift mutations of DLK1 (p.Gly199Alafs*11, p.Val271Cysfs*14, and p.Pro160Leufs*50) in five women from three families with CPP. Segregation analysis was consistent with the maternal imprinting of DLK1. Serum DLK1 concentrations were undetectable in three affected women. Metabolic abnormalities, such as overweight/obesity, early-onset glucose intolerance/type 2 diabetes mellitus, and hyperlipidemia, were more prevalent in women with the DLK1 mutation than in the idiopathic CPP group. Notably, the human metabolic alterations were similar to the previously described dlk1-null mice phenotype. Two sisters who carried the p.Gly199Alafs*11 mutation also exhibited polycystic ovary syndrome and infertility. Loss-of-function mutations of DLK1 are a definitive cause of familial CPP. The high prevalence of metabolic alterations in adult women who experienced CPP due to DLK1 defects suggests that this antiadipogenic factor represents a link between reproduction and metabolism.

Anthocyanins from Purple Corn Ameliorated Tumor Necrosis Factor-α-Induced Inflammation and Insulin Resistance in 3T3-L1 Adipocytes via Activation of Insulin Signaling and Enhanced GLUT4 Translocation.

The aim was to compare the effect of an anthocyanin-rich extract from purple corn pericarp (PCW) and pure anthocyanins on adipogenesis, inflammation, and insulin resistance in 3T3-L1 adipocytes on basal and inflammatory conditions. Preadipocytes (3T3-L1) were treated during differentiation with or without PCW. Differentiated adipocytes were treated either individually or in combination with tumor necrosis factor α (TNF-α) and PCW, or pure C3G, Pr3G, P3G. PCW reduced preadipocyte differentiation (IC50 = 0.4 mg/mL). PCW and pure anthocyanins including C3G reduced fatty acid synthase enzymatic activity. PCW reduced TNF-α-dependent inflammatory status increasing adiponectin (39%), and decreasing leptin (-79%). PCW and C3G increased glucose uptake and reduced reactive oxygen species generation in insulin resistant adipocytes. An increase in phosphorylation was observed in AKT, IKK, and MEK, and a decrease in IRS and mTOR activating the insulin receptor-associated pathway. PCW (7.5-fold) and C3G (6.3-fold) enhanced GLUT4 membrane translocation compared to insulin resistant adipocytes. Anthocyanins from colored corn prevented adipocyte differentiation, lipid accumulation, and reduced PPAR-γ transcriptional activity on adipocytes in basal conditions. Ameliorated TNF-α-induced inflammation and insulin resistance in adipocytes via activation of insulin signaling and enhanced GLUT4 translocation suggesting a reduced hyperglycemia associated with the metabolic syndrome.

WISP1/CCN4 inhibits adipocyte differentiation through repression of PPAR\u03b3 activity

WISP1 (Wnt1-inducible signaling pathway protein-1, also known as CCN4) is a member of the CCN family able to mediate cell growth, transformation and survival in a tissue-specific manner. Here, we report that WISP1 expression was highly increased in preadipocytes and decreased during adipocyte differentiation. Moreover, we observed an increase in WISP1 gene expression in adipose tissue from both diet-induced and leptin-deficient ob/ob obese mice, suggesting that WISP1 could be involved in the pathophysiological onset of obesity. Interestingly, overexpression of WISP1 in 3T3-F442A cells prevented adipocyte differentiation via downregulation of peroxisome proliferator-activated receptor (PPARγ) transcriptional activity thereby attenuating the expression of adipogenic markers. Conversely, silencing of WISP1 enhanced adipocyte differentiation. We further show that the inactivation of PPARγ transcriptional activity was mediated, at least in part, by a direct physical association between WISP1 and PPARγ, followed by proteasome-dependent degradation of PPARγ. These results suggest for the first time that WISP1 interacts with PPARγ and that this interaction results in the inhibition of PPARγ activity. Taken together our results suggest that WISP1 functions as a negative regulator of adipogenesis.

DNA Topoisomerase IIα contributes to the early steps of adipogenesis in 3T3-L1 cells

DNA topoisomerases (Topo) are multifunctional enzymes resolving DNA topological problems such as those arising during DNA replication, transcription and mitosis. Mammalian cells express 2 class II isoforms, Topoisomerases IIα (Topo IIα) and IIβ (Topo IIβ), which have similar enzymatic properties but are differently expressed, in dividing and pluripotent cells, and in post-mitotic and differentiated cells respectively. Pre-adipocytes re-enter the cell cycle prior to committing to their differentiation and we hypothesised that Topo II could contribute to these processes. We show that Topo IIα expression in 3T3-L1 cells is induced within 16h after the initiation of the differentiation programme, peaks at 24h and rapidly declines thereafter. In contrast Topo IIβ was present both in pre-adipocytes and throughout differentiation. Inhibition of PI3K with LY294002, known to prevent adipocyte differentiation, consistently reduced the expression of Topo IIα, whereas a clear effect on Topo IIβ was not apparent. In addition, inhibition of mTOR with rapamycin also reduced the protein levels of Topo IIα. Using specific class IA PI3K catalytic subunit inhibitors, we show that p110α inhibition with A66 has the greatest reduction of Topo IIα expression and of differentiation, as measured by triglyceride storage. The timing of Topo IIα expression coincides with the mitotic clonal expansion (MCE) phase of differentiation and inhibition of Topo II with ICRF-187 during this stage decreased PPARγ1 and 2 protein levels and triglyceride storage, whereas inhibition later on has little impact. Moreover, the addition of ICRF-187 had no effect on the incorporation of EdU during S-phase at day 1 but lowered the relative cell numbers on day 2. ICRF-187 also induced an increase in the centri/pericentromeric heterochromatin localisation of Topo IIα, indicating a role for Topo IIα at these locations during MCE. In summary, we present evidence that Topo IIα plays an important role in adipogenesis during MCE and in a PI3K/mTOR-dependent manner. Considering that Topoisomerases II are targets in cancer chemotherapy, our results highlight that treatment of cancer with Topo II inhibitors may alter metabolic processes in the adipose tissue.

Hydroxycinnamic acid derivatives: a potential class of natural compounds for the management of lipid metabolism and obesity.

Hydroxycinnamic acid derivatives are important class of polyphenolic compounds originated from the Mavolanate-Shikimate biosynthesis pathways in plants. Several simple phenolic compounds such as cinnamic acid, p-coumaric acid, ferulic acid, caffeic acid, chlorgenic acid, and rosmarinic acid belong to this class. These phenolic compounds possess potent antioxidant and anti-inflammatory properties. These compounds were also showed potential therapeutic benefit in experimental diabetes and hyperlipidemia. Recent evidences also suggest that they may serve as valuable molecule for the treatment of obesity related health complications. In adipose tissues, hydroxycinnamic acid derivatives inhibit macrophage infiltration and nuclear factor κB (NF-κB) activation in obese animals. Hydroxycinnamic acid derivatives also reduce the expression of the potent proinflammatory adipokines tumor necrosis factor-α (TNFα), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor type-1 (PAI-1), and they increase the secretion of an anti-inflammatory agent adiponectin from adipocytes. Furthermore, hydroxycinnamic acid derivatives also prevent adipocyte differentiation and lower lipid profile in experimental animals. Through these diverse mechanisms hydroxycinnamic acid derivatives reduce obesity and curtail associated adverse health complications.

β-Catenin Stabilization in Skin Fibroblasts Causes Fibrotic Lesions by Preventing Adipocyte Differentiation of the Reticular Dermis

The Wnt/β-catenin pathway plays a central role in epidermal homeostasis and regeneration, but how it affects fibroblast fate decisions is unknown. We investigated the effect of targeted β-catenin stabilization in dermal fibroblasts. Comparative gene expression profiling of stem cell antigen 1- (Sca1-) and Sca1+ neonatal fibroblasts from upper and lower dermis, respectively, confirmed that Sca1+ cells had a preadipocyte signature and showed differential expression of Wnt/β-catenin–associated genes. By targeting all fibroblasts or selectively targeting Dlk1+ lower dermal fibroblasts, we found that β-catenin stabilization between developmental stages E16.5 and P2 resulted in a reduction in the dermal adipocyte layer with a corresponding increase in dermal fibrosis and an altered hair cycle. The fibrotic phenotype correlated with a reduction in the potential of Sca1+ fibroblasts to undergo adipogenic differentiation ex vivo. Our findings indicate that Wnt/β-catenin signaling controls adipogenic cell fate within the lower dermis, which potentially contributes to the pathogenesis of fibrotic skin diseases.

Inhibition of acetyl‐CoA carboxylase activity prevents adipocyte differentiation in 3T3‐L1 cells

Acetyl-CoA carboxylases (ACC) 1 and 2 catalyze the carboxylation of acetyl-CoA to malonyl-CoA and depend on biotin as a coenzyme. Cytoplasmic ACC1 produces malonyl-CoA which serves as a precursor in fatty acid (FA) synthesis. Malonyl-CoA produced by ACC2 in the outer mitochondrial membrane is an inhibitor of FA oxidation. We hypothesized that ACCs are checkpoints in adipocyte differentiation and tested this hypothesis in murine 3T3-L1 preadipocytes. Oil Red O staining and qRT-PCR were used to assess lipid droplet formation and the expression of adipocyte marker genes, respectively. Treatment of 3T3-L1 cells with up to 1 µM of the microbial ACC inhibitor soraphen A (SA) inhibited lipid droplet accumulation and was accompanied by a decrease in PPARγ mRNA expression (51.4±9.0% of controls, p<0.01) and a non-significant decrease in FABP4 mRNA expression to 55.1±21.6% of controls, at 4 days post differentiation. Treatment of 3T3-L1 cells with up to 200 μM palmitate maintained lipid droplet formation despite being treated with SA also. Expression of PPARy mRNA was similarly maintained in cells treated with both 100 nM SA and 200 µM palmitate (95.1±27.3% of controls). However, when SA treatment was initiated at 4 days post-differentiation of 3T3-L1 cells, the number or size of lipid droplets did not decrease. We conclude that ACCs are checkpoints in adipocyte differentiation. In future studies, we will use knockdown protocols to determine which of the two ACCs is the critical checkpoint in adipocyte differentiation. Supported by ARD Hatch, NIFA, and NIH.

Gcn5 and PCAF regulate PPARγ and Prdm16 expression to facilitate brown adipogenesis.

The acetyltransferase Gcn5 is critical for embryogenesis and shows partial functional redundancy with its homolog PCAF. However, the tissue- and cell lineage-specific functions of Gcn5 and PCAF are still not well defined. Here we probe the functions of Gcn5 and PCAF in adipogenesis. We found that the double knockout (DKO) of Gcn5/PCAF inhibits expression of the master adipogenic transcription factor gene PPARγ, thereby preventing adipocyte differentiation. The adipogenesis defects in Gcn5/PCAF DKO cells are rescued by ectopic expression of peroxisome proliferator-activated receptor γ (PPARγ), suggesting Gcn5/PCAF act upstream of PPARγ to facilitate adipogenesis. The requirement of Gcn5/PCAF for PPARγ expression was unexpectedly bypassed by prolonged treatment with an adipogenic inducer, 3-isobutyl-1-methylxanthine (IBMX). However, neither PPARγ ectopic expression nor prolonged IBMX treatment rescued defects in Prdm16 expression in DKO cells, indicating that Gcn5/PCAF are essential for normal Prdm16 expression. Gcn5/PCAF regulate PPARγ and Prdm16 expression at different steps in the transcription process, facilitating RNA polymerase II recruitment to Prdm16 and elongation of PPARγ transcripts. Overall, our study reveals that Gcn5/PCAF facilitate adipogenesis through regulation of PPARγ expression and regulate brown adipogenesis by influencing Prdm16 expression.

Fat depot-specific differences in pref-1 gene expression and adipocyte cellularity between Wagyu and Holstein cattle

Preadipocyte factor-1 (pref-1) is specifically expressed in preadipocytes and acts as a gatekeeper of adipogenesis by maintaining the preadipocyte state and preventing adipocyte differentiation. We hypothesized that the breed differences of adipogenic capacity in cattle could be explained by the expression level of pref-1. In this experiment, we studied the expression level of the pref-1 gene and adipocyte cellularity in subcutaneous and mesenteric adipose tissues of Japanese Black (Wagyu) and Holstein fattening cattle. In subcutaneous adipose tissue, there were no significant differences in the pref-1 gene expression levels and adipocyte sizes between the breeds. In contrast, the expression level of the pref-1 gene in mesenteric adipose tissue of Holsteins was significantly higher than that of Wagyu. In addition, the size of mesenteric adipocytes in Holsteins was significantly smaller than that of Wagyu. These results indicate that the breed differences of fattening cattle affect the expression pattern of the pref-1 gene and adipocyte cellularity in a fat depot-specific manner.

Suppression of PPARγ through MKRN1-mediated ubiquitination and degradation prevents adipocyte differentiation

The central regulator of adipogenesis, PPARγ, is a nuclear receptor that is linked to obesity and metabolic diseases. Here we report that MKRN1 is an E3 ligase of PPARγ that induces its ubiquitination, followed by proteasome-dependent degradation. Furthermore, we identified two lysine sites at 184 and 185 that appear to be targeted for ubiquitination by MKRN1. Stable overexpression of MKRN1 reduced PPARγ protein levels and suppressed adipocyte differentiation in 3T3-L1 and C3H10T1/2 cells. In contrast, MKRN1 depletion stimulated adipocyte differentiation in these cells. Finally, MKRN1 knockout MEFs showed an increased capacity for adipocyte differentiation compared with wild-type MEFs, with a concomitant increase of PPARγ and adipogenic markers. Together, these data indicate that MKRN1 is an elusive PPARγ E3 ligase that targets PPARγ for proteasomal degradation by ubiquitin-dependent pathways, and further depict MKRN1 as a novel target for diseases involving PPARγ.

Hypoxia induces adipocyte differentiation of adipose‐derived stem cells by triggering reactive oxygen species generation

Generation of reactive oxygen species (ROS) by NADPH oxidase 4 (Nox4) induces the proliferation and migration of adipose-derived stem cells (ASCs). However, the functional role of mitochondrial ROS (mtROS) generation in ASCs is unknown. Therefore, we have investigated whether hypoxia induces the differentiation of ASCs via ROS generation. We also have tried to identify the cellular mechanisms of ROS generation underlying adipocyte differentiation. Hypoxia (2%) and ROS generators, such as antimycin and rotenone, induced adipocyte differentiation, which was attenuated by an ROS scavenger. Although Nox4 generates ROS and regulates proliferation of ASCs, Nox4 inhibition or Nox4 silencing did not inhibit adipocyte differentiation; indeed fluorescence intensity of mito-SOX increased in hypoxia, and treatment with mito-CP, a mtROS scavenger, significantly reduced hypoxia-induced adipocyte differentiation. Phosphorylation of Akt and mTOR was induced by hypoxia, while inhibition of these molecules prevented adipocyte differentiation. Thus hypoxia induces adipocyte differentiation by mtROS generation, and the PI3K/Akt/mTOR pathway is involved.

Retinoids and nuclear retinoid receptors in white and brown adipose tissues: physiopathologic aspects.

Vitamin A, ingested either as retinol or β-carotene from animal- or plant-derived foods respectively, is a nutrient essential for many biological functions such as embryonic development, vision, immune response, tissue remodeling, and metabolism. Its main active metabolite is all trans-retinoic acid (atRA), which regulates gene expression through the activation of α, β, and γ isotypes of the nuclear atRA receptor (RAR). More recently, retinol derivatives were also shown to control the RAR activity, enlightening the interplay between vitamin A metabolism and RAR-mediated transcriptional control. The white and brown adipose tissues regulate the energy homeostasis by providing dynamic fatty acid storing and oxidizing capacities to the organism, in connection with the other fatty acid-consuming tissues. This concerted interorgan response to fatty acid fluxes is orchestrated, in part, by the endocrine activity of the adipose tissue depots. The adipose tissues are also sites for synthesizing and storing vitamin A derivatives, which will act as hormonal cues or intracellularly to regulate essential aspects of adipocyte biology. As agents that prevent adipocyte differentiation hence, expected to decrease fat mass, and inducers of uncoupling protein expression, thus, favoring energy expenditure, retinoids have prompted many investigations to decipher their roles in adipose tissue pathophysiology, which are summarized in this review.

Fisetin regulates obesity by targeting mTORC1 signaling

Fisetin, a flavonol present in vegetables and fruits, possesses antioxidative and anti-inflammatory properties. In this study, we have demonstrated that fisetin prevents diet-induced obesity through regulation of the signaling of mammalian target of rapamycin complex 1 (mTORC1), a central mediator of cellular growth, cellular proliferation and lipid biosynthesis. To evaluate whether fisetin regulates mTORC1 signaling, we investigated the phosphorylation and kinase activity of the 70-kDa ribosomal protein S6 kinase 1 (S6K1) and mTORC1 in 3T3-L1 preadipocytes. Fisetin treatment of preadipocytes reduced the phosphorylation of S6K1 and mTORC1 in a time- and concentration-dependent manner. To further our understanding of how fisetin negatively regulates mTORC1 signaling, we analyzed the phosphorylation of S6K1, mTOR and Akt in fisetin-treated TSC2-knockdown cells. The results suggested that fisetin treatment inhibits mTORC1 activity in an Akt-dependent manner. Recent studies have shown that adipocyte differentiation is dependent on mTORC1 activity. Fisetin treatment inhibited adipocyte differentiation, consistent with the negative effect of fisetin on mTOR. The inhibitory effect of fisetin on adipogenesis is dependent of mTOR activity, suggesting that fisetin inhibits adipogenesis and the accumulation of intracellular triglycerides during adipocyte differentiation by targeting mTORC1 signaling. Fisetin supplementation in mice fed a high-fat diet (HFD) significantly attenuated HFD-induced increases in body weight and white adipose tissue. We also observed that fisetin efficiently suppressed the phosphorylation of Akt, S6K1 and mTORC1 in adipose tissue. Collectively, these results suggest that inhibition of mTORC1 signaling by fisetin prevents adipocyte differentiation of 3T3-L1 preadipocytes and obesity in HFD-fed mice. Therefore, fisetin may be a useful phytochemical agent for attenuating diet-induced obesity.