The chalcones cardamonin and flavokawain B inhibit the differentiation of preadipocytes to adipocytes by activating ERK

Enhanced detection of ligand-PPARγ binding based on surface plasmon resonance through complexation with SRC1- or NCOR2-related polypeptide

A previous study reported the use of a biosensing technique based on surface plasmon resonance (SPR) for the ligand binding detection of peroxisome proliferator activator receptor gamma (PPARγ). This detection was designed based on the structural properties of PPARγ. Because of cross-linked protein inactivation and the low molecular weight of conventional ligands, direct ligand binding detection based on SPR has low stability and repeatability. In this study, we report an indirect response methodology based on SPR technology in which anti-His CM5 chip binds fresh PPARγ every cycle, resulting in more stable detection. We developed a remarkable improvement in ligand-protein binding detectability in vitro by introducing two coregulator-related polypeptides into this system. In parallel, a systematic indirect response methodology can reflect the interaction relationship between ligands and proteins to some extent by detecting the changes in SA-SRC1 and GST-NCOR2 binding to PPARγ. Rosiglitazone, a PPARγ agonist with strong affinity, is a potent insulin-sensitizing agent. Some ligands may be competitively exerted at the same sites of PPARγ (binding rosiglitazone). We demonstrated using indirect response methodology that selective PPARγ modulator (SPPARM) candidates of PPARγ can be found by competing for the binding of the rosiglitazone site on PPARγ, although they may have no effect on polypeptides and PPARγ binding.

Antioxidant and Anti-Obesity Effects of Juglans mandshurica in 3T3-L1 Cells and High-Fat Diet Obese Rats

Juglans mandshurica Maxim. walnut (JMW) is well-known for the treatment of dermatosis, cancer, gastritis, diarrhea, and leukorrhea in Korea. However, the molecular mechanism underlying its anti-obesity activity remains unknown. In the current study, we aimed to determine whether JMW can influence adipogenesis in 3T3-L1 preadipocytes and high-fat diet rats and determine the antioxidant activity. The 20% ethanol extract of JMW (JMWE) had a total polyphenol content of 133.33 ± 2.60 mg GAE/g. Considering the antioxidant capacity, the ABTS and DPPH values of 200 μg/ml of JMWE were 95.69 ± 0.94 and 79.38 ± 1.55%, respectively. To assess the anti-obesity activity of JMWE, we analyzed the cell viability, fat accumulation, and adipogenesis-related factors, including CCAAT-enhancer-binding protein alpha (C/EBPα), sterol regulatory element-binding protein-1c (SREBP1c), peroxisome proliferator-activated receptor-gamma (PPARγ), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC). We found that total lipid accumulation and triglyceride levels were reduced, and the fat accumulation rate decreased in a dose-dependent manner. Furthermore, JMWE suppressed adipogenesis-related factors C/EBPα, PPARγ, and SREBP1c, as well as FAS and ACC, both related to lipogenesis. Moreover, animal experiments revealed that JMWE could be employed to prevent and treat obesity-related diseases. Hence, JMWE could be developed as a healthy functional food and further explored as an anti-obesity drug.

Natural Chalcones for the Management of Obesity Disease

In the last decade, the incidence of obesity has increased dramatically worldwide, reaching a dangerous pandemic spread. This condition has serious public health implications as it significantly increases the risk of chronic diseases such as type 2 diabetes, fatty liver, hypertension, heart attack, and stroke. The treatment of obesity is therefore the greatest health challenge of our time. Conventional therapeutic treatment of obesity is based on the use of various synthetic molecules belonging to the class of appetite suppressants, lipase inhibitors, hormones, metabolic regulators, and inhibitors of intestinal peptide receptors. The long-term use of these molecules is generally limited by various side effects and tolerance. For this reason, the search for natural alternatives to treat obesity is a current research goal. This review therefore examined the anti-obesity potential of natural chalcones based on available evidence from in vitro and animal studies. In particular, the results of the main in vitro studies describing the principal molecular therapeutic targets and the mechanism of action of the different chalcones investigated were described. In addition, the results of the most relevant animal studies were reported. Undoubtedly, future clinical studies are urgently needed to confirm and validate the potential of natural chalcones in the clinical prophylaxis of obesity.

Current Status and Future Perspectives on Therapeutic Potential of Apigenin: Focus on Metabolic-Syndrome-Dependent Organ Dysfunction

Metabolic syndrome and its associated disorders such as obesity, insulin resistance, atherosclerosis and type 2 diabetes mellitus are globally prevalent. Different molecules showing therapeutic potential are currently available for the management of metabolic syndrome, although their efficacy has often been compromised by their poor bioavailability and side effects. Studies have been carried out on medicinal plant extracts for the treatment and prevention of metabolic syndrome. In this regard, isolated pure compounds have shown promising efficacy for the management of metabolic syndrome, both in preclinical and clinical settings. Apigenin, a natural bioactive flavonoid widely present in medicinal plants, functional foods, vegetables and fruits, exerts protective effects in models of neurological disorders and cardiovascular diseases and most of these effects are attributed to its antioxidant action. Various preclinical and clinical studies carried out so far show a protective effect of apigenin against metabolic syndrome. Herein, we provide a comprehensive review on both in vitro and in vivo evidence related to the promising antioxidant role of apigenin in cardioprotection, neuroprotection and renoprotection, and to its beneficial action in metabolic-syndrome-dependent organ dysfunction. We also provide evidence on the potential of apigenin in the prevention and/or treatment of metabolic syndrome, analysing the potential and limitation of its therapeutic use.

Possible Participation of Ionotropic Glutamate Receptors and l-Arginine-Nitric Oxide-Cyclic Guanosine Monophosphate-ATP-Sensitive K+ Channel Pathway in the Antinociceptive Activity of Cardamonin in Acute Pain Animal Models

The perception of pain caused by inflammation serves as a warning sign to avoid further injury. The generation and transmission of pain impulses involves various pathways and receptors. Cardamonin isolated from Boesenbergia rotunda (L.) Mansf. has been reported to exert antinociceptive effects in thermal and mechanical pain models; however, the precise mechanism has yet to be examined. The present study investigated the possible mechanisms involved in the antinociceptive activity of cardamonin on protein kinase C, N-methyl-d-aspartate (NMDA) and non-NMDA glutamate receptors, l-arginine/cyclic guanosine monophosphate (cGMP) mechanism, as well as the ATP-sensitive potassium (K⁺) channel. Cardamonin was administered to the animals intra-peritoneally. Present findings showed that cardamonin significantly inhibited pain elicited by intraplantar injection of phorbol 12-myristate 13-acetate (PMA, a protein kinase C activator) with calculated mean ED₅₀ of 2.0 mg/kg (0.9–4.5 mg/kg). The study presented that pre-treatment with MK-801 (NMDA receptor antagonist) and NBQX (non-NMDA receptor antagonist) significantly modulates the antinociceptive activity of cardamonin at 3 mg/kg when tested with glutamate-induced paw licking test. Pre-treatment with l-arginine (a nitric oxide precursor), ODQ (selective inhibitor of soluble guanylyl cyclase) and glibenclamide (ATP-sensitive K⁺ channel inhibitor) significantly enhanced the antinociception produced by cardamonin. In conclusion, the present findings showed that the antinociceptive activity of cardamonin might involve the modulation of PKC activity, NMDA and non-NMDA glutamate receptors, l-arginine/nitric oxide/cGMP pathway and ATP-sensitive K⁺ channel.

Antioxidant and Anti-Obesity Activities of Polygonum cuspidatum Extract through Alleviation of Lipid Accumulation on 3T3-L1 Adipocytes

Natural products are widely used due to their various biological activities which include antiinflammatory, antioxidant, and anti-obesity effects. In this study, we determined the antioxidative and anti-obesity effects of Polygonum cuspidatum 50% ethanol extract (PEE). The antioxidative effect of PEE was evaluated using its radical scavenging activity, total phenolic content, and reducing power. The anti-obesity effect of PEE was investigated using 3T3-L1 adipocytes. The antioxidative activity of PEE was progressively increased in various concentrations, mainly due to the presence of phenolic compounds. PEE also alleviated lipid accumulation on 3T3-L1 adipocytes and downregulated the mRNA and protein production of adipogenesis-related (SREBP-1c, PPARγ, C/EBPα) and lipogenesis-related (aP2, FAS, ACC) markers. Furthermore, we found that the inhibitory effect on lipid accumulation via PEE was caused by the alleviation of NF-κB, p38 MAPK, ERK1/2, and JNK at the protein level. Taken together, our results imply that PEE is a potential antioxidant that can prevent obesityassociated disorders.

Effects of Propolis Extract and Propolis-Derived Compounds on Obesity and Diabetes: Knowledge from Cellular and Animal Models

Propolis is a natural product resulting from the mixing of bee secretions with botanical exudates. Since propolis is rich in flavonoids and cinnamic acid derivatives, the application of propolis extracts has been tried in therapies against cancer, inflammation, and metabolic diseases. As metabolic diseases develop relatively slowly in patients, the therapeutic effects of propolis in humans should be evaluated over long periods of time. Moreover, several factors such as medical history, genetic inheritance, and living environment should be taken into consideration in human studies. Animal models, especially mice and rats, have some advantages, as genetic and microbiological variables can be controlled. On the other hand, cellular models allow the investigation of detailed molecular events evoked by propolis and derivative compounds. Taking advantage of animal and cellular models, accumulating evidence suggests that propolis extracts have therapeutic effects on obesity by controlling adipogenesis, adipokine secretion, food intake, and energy expenditure. Studies in animal and cellular models have also indicated that propolis modulates oxidative stress, the accumulation of advanced glycation end products (AGEs), and adipose tissue inflammation, all of which contribute to insulin resistance or defects in insulin secretion. Consequently, propolis treatment may mitigate diabetic complications such as nephropathy, retinopathy, foot ulcers, and non-alcoholic fatty liver disease. This review describes the beneficial effects of propolis on metabolic disorders.

Cardamonin suppresses lipogenesis by activating protein kinase A-mediated browning of 3T3-L1 cells

BACKGROUND

Obesity develops when dietary energy intake exceeds energy expenditure, and can be associated with metabolic syndrome. Recent studies have shown that dietary phytochemicals can promote energy expenditure by inducing the browning of white adipose tissue (WAT).

PURPOSE

This study investigated whether cardamonin induces the browning of 3T3-L1 adipocytes through the activation of protein kinase A (PKA).

METHODS

Anti-obesity potential of cardamonin was evaluated in 3T3-L1 adipocytes. Adipocyte-specific genes were observed using western blot, qPCR analysis and immunocytochemistry.

RESULTS

Cardamonin treatment inhibited lipid droplet accumulation and reduced the expression of the adipogenic proteins C/EBPα and FABP4, and the lipogenic proteins LPAATθ, lipin 1, DGAT1, SREBP1, and FAS. Cardamonin also induced the expression of the browning marker genes PRDM16, PGC1α, and UCP1 at the mRNA and protein levels, and induced mRNA expression of CD137, a key marker of beige adipocytes. It also increased the expression of the β-oxidation genes CPT1 and PPARα at the mRNA and protein levels. In addition, cardamonin increased PKA phosphorylation and the mRNA and protein expression of the downstream lipolytic enzymes adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL).

CONCLUSION

Our findings demonstrate novel effects of cardamonin to stimulate adipocyte browning, suppress lipogenesis, and promote lipolysis, implying it may have potential as an anti-obesity agent.

Cyclization of flavokawain B reduces its activity against human colon cancer cells

Chalcones are naturally occurring compounds exhibiting biological activity through multiple mechanisms. Flavokawain B is one of chalcones found in kava plant. In our studies, we focused on the anticancer activity of flavokawain B in colorectal cancer cells LoVo and its resistant to doxorubicin subline-LoVo/Dx. Strong cytotoxic activity of flavokawain B and its ability to inhibit the proliferation in both cell lines was detected. These effects accompanied with induction cell cycle arrest in G2/M phase and the presence of SubG1 fraction. Flavokawain B at low concentration led to increase of caspase-3 activity. The chalcone-induced apoptosis was also confirmed by DNA fragmentation. In our work, the conversion of flavokawain B to corresponding flavanone-5,7-dimetoxyflavanone-was shown to be more extensive in cancer than in non-cancer cells. We found that the cyclization of the chalcone was related to the significant decrease in the cytotoxicity. Cell proliferation and cell cycle progression were not impaired significantly in the studied cancer cells incubated with 5,7-dimethoxyflavanone. We did not observe apoptosis in the cells incubated with flavanone. The results from biological studies agreed with the theoretical activity that emerges from structural parameters.

Cardamonin attenuates chronic inflammation and tumorigenesis in colon

Cardamonin (CAD) is a member of the aromatic ketones family that is closely related to anti-bacterial, anti-inflammatory and anti-cancer effects. Nevertheless, the physiological function of cardamonin in chronic colitis and colon cancer has not been well verified. We found that cardamonin treatment alleviates intestinal disease, including recurring colitis and colitis-associated tumorigenesis, along with the reduced secretion of IL-1β and TNF-α. Further, cardamonin inhibits cell viability and inflammation factors of colorectal cancer cells in vitro. In tumor cells, the inhibitory effect of cardamonin on cell proliferation is closely related to decreased phosphorylation of signal transducers and activators of transcription (STAT) signals. This study reveals the crucial role of cardamonin in sustaining gastrointestinal homeostasis and offers a new strategy for colon cancer therapy.

Enzymatically modified isoquercitrin promotes energy metabolism through activating AMPKα in male C57BL/6 mice

Quercetin possesses various health beneficial functions, but its poor bioavailability limits these functions. Enzymatically modified isoquercitrin (EMIQ) is a quercetin glycoside with a greater bioavailability than quercetin. In this study, we investigated whether EMIQ regulates energy metabolism in mice and its underlying molecular mechanism. Male C57BL/6 mice were fed a normal diet with different doses of EMIQ or quercetin (0.02%, 0.1% and 0.5%) for two weeks. Supplementation with 0.1% EMIQ significantly decreased white adipose tissue (WAT) weight. Supplementation with 0.02% and 0.1% EMIQ promoted phosphorylation of adenosine monophosphate activated protein kinase (AMPK) in the WAT, liver, and muscle. In the WAT, 0.1% EMIQ downregulated peroxisome proliferator-activated receptor (PPAR)γ, CCAAT-enhancer-binding protein (C/EBP)α, C/EBPβ, and sterol regulatory element-binding protein 1 expression, as well as upregulated mitochondrial uncoupling protein (UCP) 2 and carnitine palmitoyltransferase-1 expression. Supplementation with 0.1% EMIQ also promoted the expression of thermogenesis-associated factors including PPARγ coactivator α (PGC-1α), UCP1, PR-domain containing protein 16, and sirtuin 1 in the WAT. In the liver, EMIQ promoted the phosphorylation of acetyl-CoA carboxylase, and increased the expression of PPARα, constitutive androstane-receptor, and farnesoid X receptor. Furthermore, supplementation with 0.02% or 0.1% EMIQ suppressed the plasma glucose level accompanied by the translocation of glucose transporter 4 to the plasma membrane of the muscle. Our results suggest that EMIQ is a potential food additive for the regulation of energy metabolism through AMPK phosphorylation.

Antinociceptive Effects of Cardamonin in Mice: Possible Involvement of TRPV₁, Glutamate, and Opioid Receptors

Pain is one of the most common cause for hospital visits. It plays an important role in inflammation and serves as a warning sign to avoid further injury. Analgesics are used to manage pain and provide comfort to patients. However, prolonged usage of pain treatments like opioids and NSAIDs are accompanied with undesirable side effects. Therefore, research to identify novel compounds that produce analgesia with lesser side effects are necessary. The present study investigated the antinociceptive potentials of a natural compound, cardamonin, isolated from Boesenbergia rotunda (L) Mansf. using chemical and thermal models of nociception. Our findings showed that intraperitoneal and oral administration of cardamonin (0.3, 1, 3, and 10 mg/kg) produced significant and dose-dependent inhibition of pain in abdominal writhing responses induced by acetic acid. The present study also demonstrated that cardamonin produced significant analgesia in formalin-, capsaicin-, and glutamate-induced paw licking tests. In the thermal-induced nociception model, cardamonin exhibited significant increase in response latency time of animals subjected to hot-plate thermal stimuli. The rota-rod assessment confirmed that the antinociceptive activities elicited by cardamonin was not related to muscle relaxant or sedative effects of the compound. In conclusion, the present findings showed that cardamonin exerted significant peripheral and central antinociception through chemical- and thermal-induced nociception in mice through the involvement of TRPV₁, glutamate, and opioid receptors.

Potential miRNA involvement in the anti-adipogenic effect of resveratrol and its metabolites

OBJECTIVE

Scientific research is constantly striving to find molecules which are effective against excessive body fat and its associated complications. Taking into account the beneficial effects that resveratrol exerts on other pathologies through miRNA, the aim of the present work was to analyze the possible involvement of miRNAs in the regulation of adipogenic transcription factors peroxisome proliferator-activated receptor γ (pparγ), CCAAT enhancer-binding proteins α and β (cebpβ and cebpα) induced by resveratrol and its metabolites.

METHODS

3T3-L1 maturing pre-adipocytes were treated during differentiation with 25 μM of trans-resveratrol (RSV), trans-resveratrol-3-O-sulfate (3S), trans-resveratrol-3'-O-glucuronide (3G) and trans-resveratrol-4'-O-glucuronide (4G). After computational prediction and bibliographic search of miRNAs targeting pparγ, cebpβ and cebpα, the expression of microRNA-130b-3p (miR-130b-3p), microRNA-155-5p (miR-155-5p), microRNA-27b-3p (miR-27b-3p), microRNA-31-5p (miR-31-5p), microRNA-326-3p (miR-326-3p), microRNA-27a-3p (miR-27a-3p), microRNA-144-3p (miR-144-3p), microRNA-205-5p (miR-205-5p) and microRNA-224-3p (miR-224-3p) was analyzed. Moreover, other adipogenic mediators such as sterol regulatory element binding transcription factor 1 (srebf1), krüppel-like factor 5 (klf5), liver x receptor α (lxrα) and cAMP responding element binding protein 1 (creb1), were measured by Real Time RT-PCR. As a confirmatory assay, cells treated with RSV were transfected with anti-miR-155 in order to measure cebpβ gene and protein expressions.

RESULTS

Of the miRNAs analyzed only miR-155 was modified after resveratrol and glucuronide metabolite treatment. In transfected cells with anti-miR-155, RSV did not reduce cebpβ gene and protein expression. 3S decreased gene expression of creb1, klf5, srebf1 and lxrα.

CONCLUSIONS

While RSV and glucuronide metabolites exert their inhibitory effect on adipogenesis through miR-155 up-regulation, the anti-adipogenic effect of 3S is not mediated via miRNAs.

Maturation of Adipocytes is Suppressed by Fluid Shear Stress

Preadipocytes are mechano-responsive cells and their differentiation to adipocytes may be regulated by various types of physical stimulation. Understanding the mechanism of differentiation, which increases the number of adipocytes and lipid accumulation is important in the study of obesity-related diseases. In this study, we investigated the effects of physical stimulation at different stages of adipogenic differentiation using physiological levels of fluid shear stress. Preadipocytes were treated with dexamethasone, 3-isobutyl-1-methylxanthine and insulin for 3 days (induction period) and incubated for additional 6 days for maturation. Fluid shear stress of 1 Pa at 1 Hz was applied for 1 h at different stages of differentiation. Fluid shear stress applied at the maturation period significantly reduced the expressions of C/enhancer binding protein (EBP)α and peroxisome proliferator-activated receptor (PPAR)γ2 leading to reduced lipid accumulation. Fluid shear stress applied at the early or late stages of the induction period only decreased peroxisome proliferator-activated receptor γ2 expression without any significant changes in lipid accumulation. Stimulation at multiple days during the induction period did not result in changes in lipid accumulation compared to stimulation at a single day. These results suggest that lipid droplet accumulation is effectively decreased by fluid shear stress applied during the cell maturation period. Understanding the cellular response to physical stimulation throughout the entire adipocyte differentiation period may be important in controlling adipogenesis by physical stimulation.

The effects of COST on the differentiation of 3T3-L1 preadipocytes and the mechanism of action

The objectives of this study were to explore the effect of COST (one thousand Da molecular weight chitosan oligosaccharide) on the differentiation of 3T3-L1 preadipocytes and to determine the mechanism of action. 3T3-L1 preadipocytes were used as the target cells, and the induction of the methods for the differentiation of 3T3-L1 preadipocytes was based on classic cocktails. The MTT assay was used to filtrate the concentration of COST. On the 6th day of induced-differentiation, the differentiation of 3T3-L1 cells was detected by Oil Red O staining. The expression of PPARγ and C/EBPα mRNA was determined using real-time fluorescence quantitative PCR (Q-PCR). COST inhibited 3T3-L1 preadipocyte differentiation in a dose-dependent manner and decreased lipid accumulation. At the molecular level, the expression of the transcription factors, PPARγ and C/EBPα, was reduced by COST during adipogenesis. These results indicate that COST effectively inhibited the differentiation of 3T3-L1 preadipocytes. The mechanism is related to the down-regulation expression of PPARγ and C/EBPα.

Nutritional regulation of fibroblast growth factor 21: from macronutrients to bioactive dietary compounds

Obesity is a worldwide health problem mainly due to its associated comorbidities. Fibroblast growth factor 21 (FGF21) is a peptide hormone involved in metabolic homeostasis in healthy individuals and considered a promising therapeutic candidate for the treatment of obesity. FGF21 is predominantly produced by the liver but also by other tissues, such as white adipose tissue (WAT), brown adipose tissue (BAT), skeletal muscle, and pancreas in response to different stimuli such as cold and different nutritional challenges that include fasting, high-fat diets (HFDs), ketogenic diets, some amino acid-deficient diets, low protein diets, high carbohydrate diets or specific dietary bioactive compounds. Its target tissues are essentially WAT, BAT, skeletal muscle, heart and brain. The effects of FGF21 in extra hepatic tissues occur through the fibroblast growth factor receptor (FGFR)-1c together with the co-receptor β-klotho (KLB). Mechanistically, FGF21 interacts directly with the extracellular domain of the membrane bound cofactor KLB in the FGF21- KLB-FGFR complex to activate FGFR substrate 2α and ERK1/2 phosphorylation. Mice lacking KLB are resistant to both acute and chronic effects of FGF21. Moreover, the acute insulin sensitizing effects of FGF21 are also absent in mice with specific deletion of adipose KLB or FGFR1. Most of the data show that pharmacological administration of FGF21 has metabolic beneficial effects. The objective of this review is to compile existing information about the mechanisms that could allow the control of endogenous FGF21 levels in order to obtain the beneficial metabolic effects of FGF21 by inducing its production instead of doing it by pharmacological administration.

Interplay between the chalcone cardamonin and selenium in the biosynthesis of Nrf2-regulated antioxidant enzymes in intestinal Caco-2 cells

Selenoenzymes and nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated phase II enzymes comprise key components of the cellular redox and antioxidant systems, which show multiple interrelations. Deficiency of the micronutrient selenium (Se) and impaired biosynthesis of selenoproteins have been reported to result in induction of Nrf2 target genes. Conversely, transcription of the selenoenzymes glutathione peroxidase 2 (GPx2) and thioredoxin reductase 1 (TrxR1) is up-regulated upon Nrf2 activation. Here, we have studied the interplay between Se and the secondary plant metabolite cardamonin, an Nrf2-activating chalcone, in the regulation of Nrf2-controlled antioxidant enzymes. Se-deficient and Se-repleted (sodium selenite-supplemented) human intestinal Caco-2 cells were exposed to cardamonin. Uptake of cardamonin by the Caco-2 cells was independent of their Se status. Cardamonin strongly induced gene expression of GPx2 and TrxR1. However, cardamonin treatment did not result in elevated GPx or TrxR activity and protein levels, possibly relating to a concomitant down-regulation of O-phosphoseryl-tRNA(Sec) kinase (PSTK), an enzyme involved in translation of selenoprotein mRNAs. On the other hand, induction of the Nrf2-regulated enzyme heme oxygenase 1 (HO-1) by cardamonin was diminished in Se-replete compared to Se-deficient cells. Our findings suggest that cardamonin interferes with the biosynthesis of Nrf2-regulated selenoenzymes, in contrast to the Nrf2-activating isothiocyanate compound sulforaphane, which has been shown earlier to synergize with Se-mediated cytoprotection. Conversely, the cellular Se status apparently affects the cardamonin-mediated induction of non-selenoprotein antioxidant enzymes such as HO-1.