Baicalein Inhibits Adipocyte Differentiation by Enhancing COX-2 Expression

Unraveling Obesity: Transgenerational Inheritance, Treatment Side Effects, Flavonoids, Mechanisms, Microbiota, Redox Balance, and Bioavailability-A Narrative Review

Obesity is known as a transgenerational vicious cycle and has become a global burden due to its unavoidable complications. Modern approaches to obesity management often involve the use of pharmaceutical drugs and surgeries that have been associated with negative side effects. In contrast, natural antioxidants, such as flavonoids, have emerged as a promising alternative due to their potential health benefits and minimal side effects. Thus, this narrative review explores the potential protective role of flavonoids as a natural antioxidant in managing obesity. To identify recent in vivo studies on the efficiency of flavonoids in managing obesity, a comprehensive search was conducted on Wiley Online Library, Scopus, Nature, and ScienceDirect. The search was limited to the past 10 years; from the search, we identified 31 articles to be further reviewed. Based on the reviewed articles, we concluded that flavonoids offer novel therapeutic strategies for preventing obesity and its associated co-morbidities. This is because the appropriate dosage of flavonoid compounds is able to reduce adipose tissue mass, the formation of intracellular free radicals, enhance endogenous antioxidant defences, modulate the redox balance, and reduce inflammatory signalling pathways. Thus, this review provides an insight into the domain of a natural product therapeutic approach for managing obesity and recapitulates the transgenerational inheritance of obesity, the current available treatments to manage obesity and its side effects, flavonoids and their sources, the molecular mechanism involved, the modulation of gut microbiota in obesity, redox balance, and the bioavailability of flavonoids. In toto, although flavonoids show promising positive outcome in managing obesity, a more comprehensive understanding of the molecular mechanisms responsible for the advantageous impacts of flavonoids-achieved through translation to clinical trials-would provide a novel approach to inculcating flavonoids in managing obesity in the future as this review is limited to animal studies.

Natural products as novel anti-obesity agents: insights into mechanisms of action and potential for therapeutic management

Obesity affects more than 10% of the adult population globally. Despite the introduction of diverse medications aimed at combating fat accumulation and obesity, a significant number of these pharmaceutical interventions are linked to substantial occurrences of severe adverse events, occasionally leading to their withdrawal from the market. Natural products serve as attractive sources for anti-obesity agents as many of them can alter the host metabolic processes and maintain glucose homeostasis via metabolic and thermogenic stimulation, appetite regulation, pancreatic lipase and amylase inhibition, insulin sensitivity enhancing, adipogenesis inhibition and adipocyte apoptosis induction. In this review, we shed light on the biological processes that control energy balance and thermogenesis as well as metabolic pathways in white adipose tissue browning, we also highlight the anti-obesity potential of natural products with their mechanism of action. Based on previous findings, the crucial proteins and molecular pathways involved in adipose tissue browning and lipolysis induction are uncoupling protein-1, PR domain containing 16, and peroxisome proliferator-activated receptor-γ in addition to Sirtuin-1 and AMP-activated protein kinase pathway. Given that some phytochemicals can also lower proinflammatory substances like TNF-α, IL-6, and IL-1 secreted from adipose tissue and change the production of adipokines like leptin and adiponectin, which are important regulators of body weight, natural products represent a treasure trove for anti-obesity agents. In conclusion, conducting comprehensive research on natural products holds the potential to accelerate the development of an improved obesity management strategy characterized by heightened efficacy and reduced incidence of side effects.

COX-2 Deficiency Promotes White Adipogenesis via PGE2-Mediated Paracrine Mechanism and Exacerbates Diet-Induced Obesity

Cyclooxygenase-2 (COX-2) plays a critical role in regulating innate immunity and metabolism by producing prostaglandins (PGs) and other lipid mediators. However, the implication of adipose COX-2 in obesity remains largely unknown. Using adipocyte-specific COX-2 knockout (KO) mice, we showed that depleting COX-2 in adipocytes promoted white adipose tissue development accompanied with increased size and number of adipocytes and predisposed diet-induced adiposity, obesity, and insulin resistance. The increased size and number of adipocytes by COX-2 KO were reversed by the treatment of prostaglandin E2 (PGE2) but not PGI2 and PGD2 during adipocyte differentiation. PGE2 suppresses PPARγ expression through the PKA pathway at the early phase of adipogenesis, and treatment of PGE2 or PKA activator isoproterenol diminished the increased lipid droplets in size and number in COX-2 KO primary adipocytes. Administration of PGE2 attenuated increased fat mass and fat percentage in COX-2 deficient mice. Taken together, our study demonstrated the suppressing effect of adipocyte COX-2 on adipogenesis and reveals that COX-2 restrains adipose tissue expansion via the PGE2-mediated paracrine mechanism and prevents the development of obesity and related metabolic disorders.

The Lipocalin Apolipoprotein D Functional Portrait: A Systematic Review

Apolipoprotein D is a chordate gene early originated in the Lipocalin protein family. Among other features, regulation of its expression in a wide variety of disease conditions in humans, as apparently unrelated as neurodegeneration or breast cancer, have called for attention on this gene. Also, its presence in different tissues, from blood to brain, and different subcellular locations, from HDL lipoparticles to the interior of lysosomes or the surface of extracellular vesicles, poses an interesting challenge in deciphering its physiological function: Is ApoD a moonlighting protein, serving different roles in different cellular compartments, tissues, or organisms? Or does it have a unique biochemical mechanism of action that accounts for such apparently diverse roles in different physiological situations? To answer these questions, we have performed a systematic review of all primary publications where ApoD properties have been investigated in chordates. We conclude that ApoD ligand binding in the Lipocalin pocket, combined with an antioxidant activity performed at the rim of the pocket are properties sufficient to explain ApoD association with different lipid-based structures, where its physiological function is better described as lipid-management than by long-range lipid-transport. Controlling the redox state of these lipid structures in particular subcellular locations or extracellular structures, ApoD is able to modulate an enormous array of apparently diverse processes in the organism, both in health and disease. The new picture emerging from these data should help to put the physiological role of ApoD in new contexts and to inspire well-focused future research.

Metabolic and Epigenetics Action Mechanisms of Antiobesity Medicinal Plants and Phytochemicals

Ever-growing research efforts are demonstrating the potential of medicinal plants and their phytochemicals to prevent and manage obesity, either individually or synergistically. Multiple combinations of phytochemicals can result in a synergistic activity that increases their beneficial effects at molecular, cellular, metabolic, and temporal levels, offering advantages over chemically synthesized drug-based treatments. Herbs and their derived compounds have the potential for controlling appetite, inhibiting pancreatic lipase activity, stimulating thermogenesis and lipid metabolism, increasing satiety, promoting lipolysis, regulating adipogenesis, and inducing apoptosis in adipocytes. Furthermore, targeting adipocyte life cycle using various dietary bioactives that affect different stages of adipocyte life cycle represents also an important target in the development of new antiobesity drugs. In this regard, different stages of adipocyte development that are targeted by antiobesity drugs can include preadipocytes, maturing preadipocytes, and mature adipocytes. Various herbal-derived active compounds, such as capsaicin, genistein, apigenin, luteolin, kaempferol, myricetin, quercetin, docosahexaenoic acid, quercetin, resveratrol, and ajoene, affect adipocytes during specific stages of development, resulting in either inhibition of adipogenesis or induction of apoptosis. Although numerous molecular targets that can be used for both treatment and prevention of obesity have been identified, targeted single cellular receptor or pathway has resulted in limited success. In this review, we discuss the state-of-the-art knowledge about antiobesity medicinal plants and their active compounds and their effects on several cellular, molecular, and metabolic pathways simultaneously with multiple phytochemicals through synergistic functioning which might be an appropriate approach to better management of obesity. In addition, epigenetic mechanisms (acetylation, methylation, miRNAs, ubiquitylation, phosphorylation, and chromatin packaging) of phytochemicals and their preventive and therapeutic perspective are explored in this review.

Promising influences of Scutellaria baicalensis and its two active constituents, baicalin, and baicalein, against metabolic syndrome: A review

Metabolic syndrome is known as a group of metabolic abnormalities with features including central obesity, insulin resistance, hypercholesterolemia, hypertriglyceridemia, and hypertension as well as low level of high-density lipoprotein (HDL)-cholesterol. Previous studies showed the ameliorating effects of Scutellaria baicalensis on metabolic syndrome parameters, including antidiabetic, anti-hyperlipidemic, anti-obesity, and antihypertensive. In this review, we deeply and mechanistically evaluated different studies on the effect of S. baicalensis and its two major bioactive constituents, baicalin, and baicalein, on the critical components of metabolic syndrome, including diabetes, hyperlipidemia, obesity, hypertension, and atherosclerosis. Scientific databases, including PubMed, Scopus, and Google Scholar were searched in the English language until the end of June 2020. Accordingly, S. baicalensis, and its two major bioactive constituents, baicalin and baicalein, represent promising effects on the control of metabolic syndrome and its related disorders such as obesity, hyperlipidemia, atherosclerosis, diabetes, and their following complications. In summary, our findings show that S. baicalensis and its active constituents, baicalin and baicalein, by activation and upregulation of AMPK and PPAR-γ as the main signaling in the hemostasis of glucose and lipid metabolisms may be favorable candidates for the prevention and treatment of the metabolic syndrome.

Insulin-like growth factor 2 promotes the adipogenesis of hemangioma-derived stem cells

Infantile hemangioma (IH), which is the most common tumor in infants, is characterized by rapid proliferation followed by spontaneous regression into fibro-fatty tissue in childhood. However, its specific mechanism has not been clarified. Our previous studies showed that insulin-like growth factor 2 (IGF-2) is increased in the proliferative phase of IH, which is deemed to form from hemangioma-derived stem cells (HemSC). However, it remains unclear whether IGF-2 can promote the adipogenic differentiation of HemSCs and the signaling mechanisms involved require further elucidation. In the present study, CCK-8 assay was used to detect the effect of different concentrations of IGF-2 on the proliferation of HemSCs. Immunohistochemistry was applied to observe the expression of IGF-2 and its receptors in cells. Oil red o-staining of adipogenesis was conducted after cells recevied no treatment or were induced with IGF-2 or IGF-2 plus OSI-906 for 10 days. Cells were cultured in EGM-2/FBS-10% alone or containing IGF-2, IGF-2 plus OSI-906 or IGF-2 plus LY294002 and the protein expression of C/EBPα, C/EBPβ, PPARγ, adiponectin, p-AKT and total AKT was determined using western blot analysis. In another experiment, cells were treated with 25, 50 or 100 μM propranolol, or vehicle. C/EBPα, C/EBPβ, PPARγ and IGF-2 were analyzed using western blot analysis or reverse transcription-quantitative polymerase chain reaction. Results indicated that IGF-2 significantly promoted the cell proliferation and lipid accumulation of HemSCs. The expression of phosphorylated AKT (p-AKT), C/EBPα, C/EBPβ, PPARγ and adiponectin was increased in IGF-2-treated HemSCs culture, whereas these changes were repressed by the inhibition of either the IGF-1 receptor (IGF-1R) or phosphoinositide 3-kinase (PI3K). Our previous research showed that propranolol accelerated adipogenesis in HemSCs and induced the upregulation of IGF-2. The results of the present study indicate that IGF-2 is able to accelerate adipogenesis, and the propranolol-induced promotion of dysregulated adipogenesis may be mediated by the IGF-2 via IGF-1R and PI3K pathways.

Synergistic Effect of Bupleuri Radix and Scutellariae Radix on Adipogenesis and AMP-Activated Protein Kinase: A Network Pharmacological Approach

Obesity has become a major health threat in developed countries. However, current medications for obesity are limited because of their adverse effects. Interest in natural products for the treatment of obesity is thus rapidly growing. Korean medicine is characterized by the wide use of herbal formulas. However, the combination rule of herbal formulas in Korean medicine lacks experimental evidence. According to Shennong's Classic of Materia Medica, the earliest book of herbal medicine, Bupleuri Radix (BR) and Scutellariae Radix (SR) possess the Sangsoo relationship, which means they have synergistic features when used together. Therefore these two are frequently used together in prescriptions such as Sosiho-Tang. In this study, we used the network pharmacological method to predict the interaction between these two herbs and then investigated the effects of BR, SR, and their combination on obesity in 3T3-L1 adipocytes. BR, SR, and BR-SR mixture significantly decreased lipid accumulation and the expressions of two major adipogenic factors, peroxisome proliferator-activated receptor-gamma (PPARγ) and CCAAT/enhancer-binding protein-alpha (C/EBPα), and their downstream genes, Adipoq, aP2, and Lipin1 in 3T3-L1 cells. In addition, the BR-SR mixture had synergistic effects compared with BR or SR on inhibition of adipogenic-gene expressions. BR and SR also inhibited the protein expressions of PPARγ and C/EBPα. Furthermore, the two extracts successfully activated AMP-activated protein kinase alpha (AMPK α), the key regulator of energy metabolism. When compared to those of BR or SR, the BR-SR mixture showed higher inhibition rates of PPARγ and C/EBPα, along with higher activation rate of AMPK. These results indicate a new potential antiobese pharmacotherapy and also provide scientific evidence supporting the usage of herbal combinations instead of mixtures in Korean medicine.

Liposome-Encapsulated Baicalein Suppressed Lipogenesis and Extracellular Matrix Formation in Hs68 Human Dermal Fibroblasts

The dermis of human skin contains large numbers of fibroblasts that are responsible for the production of the extracellular matrix (ECM) that supporting skin integrity, elasticity and wound healing. Previously, an in vivo study demonstrated that dermal fibroblasts siting in the lower dermis are capable to convert into skin adipose layer and hence fibroblast lipogenesis may vary the structure and elasticity of dermis. In the present study, Hs68 human dermal fibroblasts were utilized as an in vitro model to study the lipogenesis via using adipogenic differentiation medium (ADM). Baicalein, isolated from Scutellaria baicalensis, is one of the flavonoids to inhibit adipocyte differentiation due to high antioxidant activity in vitro. In order to develop a suitable formulation for baicalein (a poorly water-soluble drug), soybean phosphatidylcholine (SPC) was used to prepare baicalein-loaded liposomes to enhance drug bioavailability. Our results demonstrated that liposome-encapsulated baicalein protected cell viability and increased cellular uptake efficiency of Hs68 fibroblasts. Lipid accumulation, triglyceride synthesis and gene expressions of lipogenesis enzymes (FABP4 and LPL) were significantly increased in ADM-stimulated Hs68 fibroblasts but subsequently suppressed by liposome-encapsulated baicalein. In addition, ADM-induced TNF-α expression and related inflammatory factors was down-regulated by liposome-encapsulated baicalein. Through ADM-induced lipogenesis, the protein expression of elastin, type I and type III collagens increased remarkably, whereas liposome-encapsulated baicalein can down-regulate ADM-induced ECM protein synthesis. Taken together, we found that liposome-encapsulated baicalein can inhibit ADM-induced lipid accumulation and ECM formation in Hs68 fibroblasts through the suppression of lipogenesis enzymes and inflammatory responses. Liposome-encapsulated baicalein may have the potential to improve wound healing and restore skin structure after skin injury.

Suppression of Very Early Stage Of Adipogenesis by Baicalein, a Plant-Derived Flavonoid through Reduced Akt-C/EBPα-GLUT4 Signaling-Mediated Glucose Uptake in 3T3-L1 Adipocytes

Baicalein has been used as a Chinese medicine, and is an abundant plant flavonoid present in fruits and vegetables. Here, we examined the effects of baicalein in adipogenesis and investigated its molecular mechanism in adipocytes. Baicalein lowered the intracellular lipid accumulation and decreased the transcription levels of the adipocyte-specific genes in mouse 3T3-L1 adipocytes. Glucose uptake mediated by glucose transporter 4 (GLUT4) was reduced, causing down-regulation of the intracellular lipid accumulation. These reductions were also observed even when baicalein was added in only early stage of adipogenesis (0-2 days) of 6-day-adipogenesis. Chromatin immunoprecipitation assay showed that baicalein decreased the binding level of C/EBPα protein to the promoter region of the GLUT4 gene. Phosphorylation of Akt at 1 h after the initiation of adipogenesis was inhibited by the treatment with baicalein. Inhibition during only the first 1.5 h after the initiation of adipogenesis by baicalein or an Akt inhibitor was enough to decrease the lipid contents in the cells undergoing adipocyte differentiation for 6 days. These results indicate that baicalein decreased the intracellular lipid accumulation by down-regulation of glucose uptake via repression of Akt-C/EBPα-GLUT4 signaling in the very early stage of adipogenesis of 3T3-L1 adipocytes.

Molecular mechanisms of flavonoids in melanin synthesis and the potential for the prevention and treatment of melanoma

Flavonoids are becoming popular nutraceuticals. Different flavonoids show similar or distinct biological effects on different tissues or cell types, which may limit or define their usefulness in cancer prevention and/or treatment application. This review focuses on a few selected flavonoids and discusses their functions in normal and transformed pigment cells, including cyanidin, apigenin, genistein, fisetin, EGCG, luteolin, baicalein, quercetin and kaempferol. Flavonoids exhibit melanogenic or anti-melanogenic effects mainly via transcriptional factor MiTF and/or the melanogenesis enzymes tyrosinase, DCT or TYRP-1. To identify a direct target has been a challenge as most studies were not able to discriminate whether the effect(s) of the flavonoid were from direct targeting or represented indirect effects. Flavonoids exhibit an anti-melanoma effect via inhibiting cell proliferation and invasion and inducing apoptosis. The mechanisms are also multi-fold, via ROS-scavenging, immune-modulation, cell cycle regulation and epigenetic modification including DNA methylation and histone deacetylation. In summary, although many flavonoid compounds are extremely promising nutraceuticals, their detailed molecular mechanism and their multi-target (simultaneously targeting multiple molecules) nature warrant further investigation before advancement to translational studies or clinical trials.

Redox modulation of adipocyte differentiation: hypothesis of "Redox Chain" and novel insights into intervention of adipogenesis and obesity

In view of the global prevalence of obesity and obesity-associated disorders, it is important to clearly understand how adipose tissue forms. Accumulating data from various laboratories implicate that redox status is closely associated with energy metabolism. Thus, biochemical regulation of the redox system may be an attractive alternative for the treatment of obesity-related disorders. In this work, we will review the current data detailing the role of the redox system in adipocyte differentiation, as well as identifying areas for further research. The redox system affects adipogenic differentiation in an extensive way. We propose that there is a complex and interactive "redox chain," consisting of a "ROS-generating enzyme chain," "combined antioxidant chain," and "transcription factor chain," which contributes to fine-tune the regulation of ROS level and subsequent biological consequences. The roles of the redox system in adipocyte differentiation are paradoxical. The redox system exerts a "tridimensional" mechanism in the regulation of adipocyte differentiation, including transcriptional, epigenetic, and posttranslational modulations. We suggest that redoxomic techniques should be extensively applied to understand the biological effects of redox alterations in a more integrated way. A stable and standardized "redox index" is urgently needed for the evaluation of the general redox status. Therefore, more effort should be made to establish and maintain a general redox balance rather than to conduct simple prooxidant or antioxidant interventions, which have comprehensive implications.

miR-125a-3p and miR-483-5p promote adipogenesis via suppressing the RhoA/ROCK1/ERK1/2 pathway in multiple symmetric lipomatosis

Multiple symmetric lipomatosis (MSL) is a rare disease characterized by symmetric and abnormal distribution of subcutaneous adipose tissue (SAT); however, the etiology is largely unknown. We report here that miR-125a-3p and miR-483-5p are upregulated in the SAT of MSL patients, promoting adipogenesis through suppressing the RhoA/ROCK1/ERK1/2 pathway. TaqMan microRNA (miR) array analysis revealed that 18 miRs were upregulated in the SAT of MSL patients. Transfection of human adipose-derived mesenchymal stem cells (hADSCs) with the individual agomirs of these 18 miRs showed that miR-125a-3p and miR-483-5p significantly promoted adipogenesis. A dual-luciferase assay showed that RhoA and ERK1 were the targets of miR-125a-3p and miR-483-5p, respectively. Moreover, transfection of hADSCs with mimics of miR-125a-3p and miR-483-5p resulted in a pronounced decrease of ERK1/2 phosphorylation in the nucleus; conversely, transfection of hADSCs with inhibitors of miR-125a-3p and miR-483-5p led to a significant increase of ERK1/2 phosphorylation in the nucleus. Most importantly, we found that miR-125a-3p and miR-483-5p promoted de novo adipose tissue formation in nude mice. These results demonstrated that miR-125a-3p and miR-483-5p coordinately promoted adipogenesis through suppressing the RhoA/ROCK1/ERK1/2 pathway. Our findings may provide novel strategies for the management and treatment of MSL or obesity.

Oroxylin A, a constituent of Oroxylum indicum inhibits adipogenesis and induces apoptosis in 3T3-L1 cells

Oroxylin A (OA) is a flavonoid found in Oroxylum indicum, a medicinal plant with multiple biological activities. This study was taken up to investigate the effect of OA, on adipogenesis, lipolysis and apoptosis in 3T3 L1 cells. Pre-adipocytes were treated with 10-40 μM OA on various days of adipogenesis treatment schedule. Mature adipocytes were treated with OA for lipolysis and apoptosis studies. In maturing pre-adipocytes, 10 μM OA suppressed intracellular lipid accumulation by 42.19% which was confirmed by lipidTox imaging of cells. In addition, OA decreased the nuclear translocation of PPARγ and mRNA expression of its downstream genes (FAS and LPL) along with adiponectin secretion. In mature adipocytes, 40 μM of OA decreased cell viability by 30% of control. Annexin V/PI staining showed induction of apoptosis which was further confirmed by enhanced levels of pro-apoptotic proteins Bax, cyt c, AIF and chromatin condensation. OA enhanced TNF-α secretion, lipolysis and decreased Akt phosphorylation in mature adipocytes. Findings suggest that OA possibly exerts its anti-obesity effect by affecting adipocyte life cycle at critical points of differentiation and maturity. When we compared the potency of OA with non-methoxylated flavonoids morin, naringenin and kaempferol on adipocyte life cycle OA was far more potent. Thus, study clearly indicates a new role for oroxylin A as regulator of adipocyte life cycle. In addition, study also suggested a specific role of methoxylated group in exerting lipolysis and cytotoxic effects in mature adipocytes.

Baicalein inhibits lipid accumulation by regulating early adipogenesis and m-TOR signaling

Baicalein is a type of flavonoid that originates from Scutellaria baicalensis. In this study, we examined how baicalein inhibits lipid accumulation during adipogenesis in 3T3-L1 cells. Our data show that baicalein inhibited lipid accumulation during adipogenesis in a dose-dependent manner. Baicalein inhibition was limited to the early adipogenic stage. Cell cycle analysis showed that baicalein induced cell cycle arrest in the G0/G1 phase through cyclin downregulation. In addition, baicalein suppressed the mRNA expression of early adipogenic factors leading to downregulation of late adipogenic factors at mRNA and protein levels. Inhibition of adipogenic factors by baicalein was correlated with downregulation of lipid synthetic enzymes. Additionally, baicalein negatively regulated the m-TOR signaling pathway involved in lipid accumulation during adipogenesis, thus inhibiting phosphorylation of m-TOR and p70S6K. In a zebrafish study, baicalein significantly reduced lipid accumulation in Nile Red staining. Consistent with a report using cell lines, mRNA expression of adipogenic factors was decreased in a dose-dependent manner by baicalein. This result reflects a reduction in total triglyceride levels based on a triglyceride assay. Our data suggest that baicalein inhibits lipid accumulation by controlling the cell cycle and m-TOR signaling in 3T3-L1 cells, and its anti-adipogenic effect was found in a zebrafish model.

Inhibitory Effects of Hwangryunhaedok-Tang in 3T3-L1 Adipogenesis by Regulation of Raf/MEK1/ERK1/2 Pathway and PDK1/Akt Phosphorylation

Hwangryunhaedok-tang (HRT) has been long used as traditional medicine in Asia. However, inhibitory role of HRT is unclear in early stage of 3T3-L1 adipocyte differentiation related to signaling. In the present study, we investigated the inhibitory effects of HRT on upstream signaling of peroxisome proliferation-activity receptor-γ (PPAR-γ) and CCAAT/enhancer binding protein-β (C/EBP-β) expression in differentiation of 3T3-L1 preadipocytes. We found that HRT significantly inhibited the adipocyte differentiation by downregulating several adipocyte-specific transcription factors including PPAR-γ, C/EBP-α, and C/EBP-β in 3T3-L1 preadipocytes. Furthermore, we observed that HRT markedly inhibited the differentiation media-mediated phosphorylation of Raf/extracellular mitogen-activated protein kinase 1 (MEK1)/signal-regulated protein kinase 1/2 (ERK1/2) and phosphorylation of phosphoinositide-dependent kinase 1 (PDK1)/Akt. These results indicate that anti-adipogenesis mechanism involves the downregulation of the major transcription factors of adipogenesis including PPAR-γ and C/EBP-α through inhibition of Raf/MEK1/ERK1/2 phosphorylation and PDK1/Akt phosphorylation by HRT. Furthermore, high performance liquid chromatography (HPLC) analysis showed HRT contains active antiobesity constituents such as palmatine, berberine, geniposide, baicalin, baicalein, and wogonin. Taken together, this study suggested that anti-adipogenesis effects of HRT were accounted by downregulation of Raf/MEK1/ERK1/2 pathway and PDK1/Akt pathway during 3T3-L1 adipocyte differentiation.

Proteome analysis of rat bone marrow mesenchymal stem cell differentiation

Bone marrow multipotent stromal cells (or mesenchymal stem cells; MSCs) have the capacity for renewal and the potential to differentiate in culture into several cell types including osteoblasts, chondrocytes, adipocytes, cardiomyocytes, and neurons. This study was designed to investigate the protein expression profiles of rat bone marrow MSCs during differentiation into adipogenic (by dexamethasone, isobutylmethylxanthine, insulin, and indomethacin), cardiomyogenic (by 5-azacytidine), chondrogenic (by ascorbic acid, insulin-transferrin-selenous acid, and transforming growth factor-β1), and osteogenic (by dexamethasone, β-glycerophosphate, and ascorbic acid) lineages by well-known differentiation inducers. Proteins extracted from differentiated MSCs were separated using two-dimensional gel electrophoresis (2-DE) and protein spots were detected using Sypro Ruby dye. Protein spots that were determined to be up- or down-regulated when the expression of corresponding spots (between weeks 1 and 2, 1 and 3, 1 and 4) showed an increase (≥2-fold) or decrease (≤0.5-fold) were successfully identified by MALDI-TOF-MS. In summary, 23 new proteins were identified either up- or down-regulated during differentiation experiments.

Platycodin D inhibits adipogenesis of 3T3-L1 cells by modulating Kruppel-like factor 2 and peroxisome proliferator-activated receptor gamma

In this study, platycodin D was found to inhibit intracellular triglyceride accumulation in 3T3-L1 cells with an IC(50) of 7.1 microM. The expression levels of genes involved in lipid metabolism such as fatty-acid-binding protein 4 and lipoprotein lipase were significantly downregulated following treatment with platycodin D. Treatment with platycodin D also resulted in a reduction of Peroxisome proliferator-activated receptor(PPAR)gamma expression and its binding to target DNA sequence. Among the various upstream regulators of PPARgamma, the expression of Kruppel-like factor(KLF)2, an anti-adipogenic factor, was significantly upregulated following platycodin D treatment. When the upregulation of KLF2 was inhibited by KLF2 siRNA, the expression and binding of PPARgamma to its target sequence were significantly recovered under these conditions. The results of this study suggested that anti-adipogenic effect of platycodin D involves the upregulation of KLF2 and subsequent downregulation of PPARgamma.

Isorhamnetin-induced anti-adipogenesis is mediated by stabilization of beta-catenin protein

AIMS

Previous studies have shown that isorhamnetin has anti-adipogenic effects in mouse 3T3-L1 cells. This study was conducted to elucidate the inhibitory mechanisms of isorhamnetin during adipogenic differentiation of human adipose tissue-derived stem cells (hAMSCs).

MAIN METHODS

The effect of isorhamnetin on adipogenic differentiation of hAMSCs was quantified by Oil Red O staining and a triglyceride assay. In addition, real-time PCR and Western blot were used to determine the expression of adipogenesis-related genes.

KEY FINDINGS

Isorhamnetin inhibited the adipocyte differentiation of hAMSCs. Additionally, when the effects of Wnt antagonists that promote adipogenesis were evaluated, isorhamnetin was found to down-regulate the mRNA levels of sFRP1 and Dkk1, but had no effect on the mRNA levels of sFRP2, sFRP3, sFRP4 and Dkk3. Isorhamnetin also inhibited the expression of Wnt receptor and co-receptor genes. Furthermore, isorhamnetin increased the protein levels of beta-catenin, an effector molecule of Wnt signaling, but had no effect on the mRNA levels of beta-catenin. The phosphorylation level of GSK 3beta was also increased by isorhamnetin. These results were confirmed by the fact that the expression of c-myc, cyclin D1 and PPARdelta, which are target genes of beta-catenin, was upregulated by isorhamnetin. Moreover, isorhamnetin reduced the mRNA expression levels of C/EBPalpha and PPARgamma, which are known to be inhibited by c-myc or by cyclin D1 and PPARdelta, respectively.

SIGNIFICANCE

Our results indicate that isorhamnetin inhibits the adipogenic differentiation of hAMSCs and that its mechanisms are mediated by the stabilization of beta-catenin.

Fermented Canadian lowbush blueberry juice stimulates glucose uptake and AMP-activated protein kinase in insulin-sensitive cultured muscle cells and adipocytesThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products

Extracts of the Canadian lowbush blueberry ( Vaccinium angustifolium Ait.) have recently been demonstrated to possess significant antidiabetic potential, in accordance with the traditional use of this plant as an antidiabetic natural health product. Fermentation of blueberry juice with the Serratia vaccinii bacterium is known to modify the phenolic content and increase antioxidant activity. The present study evaluated the effects of fermented blueberry juice on glucose uptake, adipogenesis, and the signaling pathways that regulate glucose transport in muscle cells and adipocytes. A 6-hour treatment with fermented juice potentiated glucose uptake by 48% in C2C12 myotubes and by 142% in 3T3-L1 adipocytes, in the presence or absence of insulin, whereas nonfermented juice had no effect on transport. Fermented juice dramatically inhibited triglyceride content during adipogenesis of 3T3-L1 cells. Chlorogenic acid and gallic acid, both major phenolic components of fermented juice, had no effect on glucose uptake. Western blot analysis of the insulin-independent AMP-activated protein kinase revealed increased phosphorylation resulting from a 6-hour treatment. This activation or the increase in glucose uptake could not be explained by increased cytosolic calcium. Fermentation with S. vaccinii is concluded to confer antidiabetic activities to blueberry juice. Although the active principles and their mechanisms of action remain to be identified, transformed blueberry juice may nevertheless represent a novel complementary therapy and a source of novel therapeutic agents against diabetes mellitus.