Pentamethylquercetin improves adiponectin expression in differentiated 3T3-L1 cells via a mechanism that implicates PPARγ together with TNF-α and IL-6

A cross-talk between sestrins, chronic inflammation and cellular senescence governs the development of age-associated sarcopenia and obesity

The rapid increase in both the lifespan and proportion of older adults is accompanied by the unprecedented rise in age-associated chronic diseases, including sarcopenia and obesity. Aging is also manifested by increased susceptibility to multiple endogenous and exogenous stresses enabling such chronic conditions to develop. Among the main physiological regulators of cellular adaption to various stress stimuli, such as DNA damage, hypoxia, and oxidative stress, are sestrins (Sesns), a family of three evolutionarily conserved proteins, Sesn1, 2, and 3. Age-associated sarcopenia and obesity are characterized by two key processes: (i) accumulation of senescent cells in the skeletal muscle and adipose tissue and (ii) creation of a systemic, chronic, low-grade inflammation (SCLGI). Presumably, failed SCLGI resolution governs the development of these chronic conditions. Noteworthy, Sesns activate senolytics, which are agents that selectively eliminate senescent cells, as well as specialized pro-resolving mediators, which are factors that physiologically provide inflammation resolution. Sesns reveal clear beneficial effects in pre-clinical models of sarcopenia and obesity. Based on these observations, we propose a novel treatment strategy for age-associated sarcopenia and obesity, complementary to the conventional therapeutic modalities: Sesn activation, SCLGI resolution, and senescent cell elimination.

Pentamethylquercetin Regulates Lipid Metabolism by Modulating Skeletal Muscle-Adipose Tissue Crosstalk in Obese Mice

Irisin is an exercise-induced hormone that regulates lipid metabolism. The present study investigates whether the anti-obesity effect of the natural flavonoid pentamethylquercetin (PMQ) is related to irisin secretion from skeletal muscle in whole animals and cultured cells. Obese mice induced by monosodium glutamate were administered oral PMQ to determine blood irisin level and in vivo parameters of lipid metabolism, and cultured mouse C2C12 myoblasts and 3T3-L1 preadipocytes were employed to investigate the related molecular identities. PMQ increased circulating irisin and decreased bodyweight, insulin, and lipid levels accompanied with increasing brown-like adipocyte formation in obese mice. The brown adipocyte marker uncoupling protein 1 (UCP-1) and other brown-like adipocyte-specific genes and/or markers were increased in mouse white fat tissue, while PMQ treatment reversed the above changes. PMQ also dose-dependently increased the reduced levels of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and fibronectin type III domain-containing 5 (FNDC5) signal molecules in obese mice. Interestingly, the irisin level was increased in the culture medium of C2C12 cells treated with PMQ, and the conditioned medium stimulated the brown-like transition of 3T3-L1 preadipocytes with the increased expression of PGC-1α, FNDC5, UCP-1, and other brown-like adipocyte-specific genes. The effects of conditioned culture medium were abolished in C2C12 cells with silenced PGC-1α. On the other hand, PMQ-induced upregulation of PGC-1α and FNDC5 expression was reduced by AMPK inhibitor Compound C in C2C12 cells. Our results demonstrate the novel information that PMQ-induced irisin secretion from skeletal muscle involves the improvement of metabolic dysfunction in obese mice via activating the AMPK/PGC-1α/FNDC5 signal pathway, suggesting that PMQ modulates skeletal muscle-adipose tissue crosstalk and may be a promising drug candidate for treating obesity and obesity-related metabolic diseases.

Quercetin regulates skeletal muscle fiber type switching via adiponectin signaling

This study aimed to investigate the role and underlying molecular mechanism of quercetin in regulating skeletal muscle fiber type transition. We found that dietary quercetin supplementation in mice significantly increased oxidative fiber-related gene expression, slow-twitch fiber percentage and succinic dehydrogenase (SDH) activity. By contrast, quercetin decreased lactate dehydrogenase (LDH) activity, fast MyHC protein expression, fast-twitch fiber percentage, and MyHC IIb mRNA expression. Furthermore, quercetin significantly increased serum adiponectin (AdipoQ) concentration, and the expression levels of AdipoQ and AdipoR1. However, inhibition of adiponectin signaling by AdipoR1 siRNA significantly attenuated the effects of quercetin on muscle fiber type-related gene expression, the percentages of slow MyHC-positive and fast MyHC-positive fibers, and metabolic enzyme activity in C2C12 myotubes. Together, our data indicated that quercetin could promote skeletal fiber switching from glycolytic type II to oxidative type I through AdipoQ signaling.

Association between Plasma Adipocytokines Levels and Intracranial versus Extracranial Atherosclerotic among Chinese Patients with Stroke

BACKGROUND

To detect the levels of plasma Adipocytokines, TNF-α, IL-6 and PAI-1 in patients with intracranial and extracranial arteriosclerosis.

METHODS

From September 2015 to September 2017, 318 patients aged ≥60 years were enrolled. Overall, 192 patients were included in the case group (intracranial and extracranial arteriosclerosis group). The 196 outpatients who matched the case groupware selected as the control group. The levels of plasma APN, TNF-α, IL-6 and PAI-1 were measured and their inter- and intra-group comparisons were performed using t-test or analysis of variance. Multivariate logistic regression analysis was used to study the correlation between intracranial arteriosclerosis and extracranial arteriosclerosis.

RESULTS

The level of plasma APN in the intracranial and extracranial arteriosclerosis group was significantly lower than that in the control group (P=0.025). The plasma levels of PAI-1, TNF-α and IL-6 were obviously higher than those in the control group (P=0.003, P=0.008, P=0.043). In the intracranial arteriosclerosis group, the level of plasma APN in patients with arterial stenosis ≥70% was significantly lower than that in patients with stenosis 30%-69% (P=0.028).

CONCLUSION

Plasma APN, PAI-1, IL-6 and TNF-α levels can be used as monitoring indicators of intracranial and extracranial arteriosclerosis. Intracranial arteriosclerosis is significantly associated with the decrease of plasma APN level and the increase of plasma PAI- 1, IL-6 and TNF-α levels.

Methylated Flavonols from Amomum koenigii J.F.Gmel. and Their Antimicrobial and Antioxidant Activities

Methylated flavonols form a special group with modulating biological activities in comparison with kaempferol and quercetin. The present study isolated ten compounds including two kaempferol methyl ethers: 5-hydroxy-3,7,4′-trimethoxyflavone (1), 3-hydroxy-5,7,4′-trimethoxyflavone (6); four quercetin methyl ethers: retusin (5-hydroxy-3,7,3′,4′-tetramethoxyflavone) (4), 3,5-dihydroxy-7,3′,4′-trimethoxyflavone (5), 3,4′-dihydroxy-5,7,3′-trimethoxyflavone (7), and 3,5,7,3′,4′-pentamethoxyflavone (9); β-sitosterol (2); 5-hydroxy-1-(4′-hydroxyphenyl)eicosan-3-one (3); p-hydroquinone (8); and vanillic acid (10) from the rhizomes and fruit of Amomum koenigii J.F.Gmel. (Zingiberaceae). Their structures were determined by MS, NMR, and X-ray spectroscopic techniques. Among the methylated flavonols, 1, 4–7, and 9 were isolated for the first time from the rhizomes, while 1, 4, and 5 were isolated from the fruit. Compounds 2, 3, 7, 8, and 10 were reported for the first time from the species. Three main methylated flavonols 1, 4, and 5 were quantitatively analyzed in the rhizomes of A. koenigii by RP-HPLC-DAD; their contents were determined to be 1.81% (1), 1.38% (4), and 1.76% (5). The antimicrobial assay against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Aspergillus niger, Fusarium oxysporum, Candida albicans, and Saccharomyces cerevisiae and antioxidant DPPH scavenging test were performed for the isolated methylated flavonols.

Flavone of Hippophae (H-flavone) lowers atherosclerotic risk factors via upregulation of the adipokine C1q/tumor necrosis factor-related protein 6 (CTRP6) in macrophages

In this study, we examined the mechanism of Flavone of Hippophae (H-flavone) in regulating macrophage foaming and atherosclerosis (AS) plaque formation. H-flavone treatment increased the secretion of C1q/tumor necrosis factor-related proteins 6 (CTRP6) in Ox-LDL-treated mouse peripheral blood macrophage cells (PBMC) and significantly reduced the percentage of cholesteryl ester (CE) in PBMC. Additionally, H-flavone suppressed Ox-LDL-induced cell foaming and the production of inflammatory cytokines through upregulating CTPR6 expression. Next, we further validated the inhibitory effect of H-flavone on plaque formation and inflammation in a mouse AS model. A substantial reduction in the secretion of inflammatory cytokines was observed in apoE-/- mice by H-flavone. Immunohistochemistry and Oil Red O staining results showed that H-flavone suppressed macrophage infiltration and the development of AS plaque. These effects were more pronounced in early administration. Our results suggest that H-flavone effectively inhibits macrophage foaming, inflammation and vascular plaque formation by upregulating CTRP6 and may be used to reduce AS risk.

Anti-Diabetic Effect of a Shihunine-Rich Extract of Dendrobium loddigesii on 3T3-L1 Cells and db/db Mice by Up-Regulating AMPK-GLUT4-PPARα

The stems of Dendrobium loddigesii, a Chinese herb, are often used to treat diabetes and its polar extract is rich in shihunine, a water-soluble Orchidaceae alkaloid, but little is known about the anti-diabetes effects and mechanism of shihunine. This study investigated the anti-diabetic effect of a shihunine-rich extract of D. loddigesii (DLS) based on 3T3-L1 cells and db/db mice. The underlying mechanisms were primarily explored using Western blot analysis and immunohistochemical staining. The 3T3-L1 cell experiments showed that DLS can reduce the intracellular accumulation of oil droplets as well as triglycerides (p < 0.001) and promote the 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2deoxyglucose (2-NBDG) uptake of 3T3-L1 cells (p < 0.001). The animal experiments confirmed that after 8 weeks of DLS treatment, the body weight, fasting blood sugar, and serum lipid levels of mice were significantly lowered, and the oral glucose tolerance test and serum insulin level were significantly improved compared to the no-treatment diabetes mellitus group. Further histomorphology observation led to the conclusion that the quantities of islet cells were significantly increased and the increase in adipose cell size was significantly suppressed. The immunohistochemical test of pancreatic tissue revealed that DLS inhibited the expression of cleaved cysteine aspartic acid-specific protease 3 (cleaved caspase-3). Western blot experiments showed that DLS had agonistic effects on adenosine monophosphate (AMP)-activated protein kinase phosphorylation (p-AMPK) and increased the expression levels of peroxisome proliferator-activated receptor α (PPARα) and glucose transporter 4 (GLUT4) in liver or adipose tissues. These data suggest that the shihunine-rich extract of D. loddigesii is an anti-diabetic fraction of D. loddigesii. Under our experimental condition, DLS at a dose of 50 mg/kg has good anti-diabetic efficacy.

Pentamethylquercetin protects against cardiac remodeling via activation of Sestrin2

Oxidative stress is widely involved in pathophysiological processes of cardiac remodeling. Molecules associated with antioxidant functions may be ideal targets for reversing cardiac remodeling. Sestrin2 is the important component of endogenous antioxidant defense, while there is little information on the pathophysiological roles of it in cardiac remodeling. The aim of this study was to investigate whether Sestrin2 is closely involved in cardiac remodeling, and whether the protective effect of pentamethylquercetin (PMQ) on cardiac remodeling is related to upregulation of the Sestrin2 endogenous antioxidant system. We generated a transverse aorta constriction (TAC)-induced pressure-overload cardiac-remodeling model in mice, and also established an isoproterenol (ISO)-induced neonatal rat cardiomyocyte (NRCM) hypertrophy model. The data showed Sestrin2 expression was downregulated significantly, and Nrf2 and HO-1 expression was also reduced in myocardial tissue or NRCM of model group, whereas keap1 expression was upregulated. PMQ significantly ameliorated cardiac remodeling and rectified the abnormal expression of Sestrin2/Nrf2/keap1. Sestrin2 small interfering RNA (SiRNA) reduced the protective effect of PMQ on NRCMs, as well as abolished its regulating effect on the Nrf2/keap1 pathway. In conclusion, Sestrin2 may be an important target in the anti-myocardial remodeling of PMQ.

A simple and effective preparation of quercetin pentamethyl ether from quercetin

Among the five hydroxy (OH) groups of quercetin (3,5,7,3',4'-pentahydroxyflavone), the OH group at 5 position is the most resistant to methylation due to its strong intramolecular hydrogen bonding with the carbonyl group at 4 position. Thus, it is generally difficult to synthesize the pentamethyl ether efficiently by conventional methylation. Here, we describe a simple and effective per-O-methylation of quercetin with dimethyl sulfate in potassium (or sodium) hydroxide/dimethyl sulfoxide at room temperature for about 2 hours, affording quercetin pentamethyl ether (QPE) quantitatively as a single product. When methyl iodide was used in place of dimethyl sulfate, the C-methylation product 6-methylquercetin pentamethyl ether was also formed. A computational study provided a rationale for the experimental results.

Chemical Constituents from the Root Bark of Calophyllum inophyllum

A new chromanone derivative, namely caloinophyllin B (1), along with seventeen known compounds 2–18 were isolated from the root bark of Calophyllum inophyllum. The structures of all isolated compounds (1–18) were determined by spectroscopic methods as well as comparison with previous reports in the literature. To the best of our knowledge, compounds 1, 3, 6, 8, 11–14 and 16 were isolated from this plant for the first time. Moreover, all isolated compounds (1–18) were evaluated for their cytotoxicity against KB and Hela S-3 cell lines. Compound 8 exhibited moderate activity toward KB and Hela S-3cells with the IC50 values of 25.8 and 18.1μM, respectively.

Caloinophyllin A, a new chromanone derivative from Calophyllum inophyllum roots

A new chromanone derivative, namely caloinophyllin A (1), along with eight known compounds (2-9), nobiletin (2), pentamethylquercetin (3), 3,5,7,4'-tetramethoxyflavone (4), 5,7,4'-trimethoxyflavone (5), 1,5-dihydroxyxanthone (6), 1,8-dimethoxy-2-hydroxyxanthone (7), 1,6-dihydroxy-7-methoxyxanthone (8) and 4-methoxycaffeic acid (9) were isolated from the roots of Calophyllum inophyllum. The structures of all the isolated compounds (1-9) were fully characterised using spectroscopic data, as well as comparison with the previous literature data. In addition, the quantum chemical calculation has been used to confirm the conformation of 1. Moreover, all isolated compounds were assessed for their in vitro cytotoxicity against five human cancer cell lines.

Pentamethylquercetin induces adipose browning and exerts beneficial effects in 3T3-L1 adipocytes and high-fat diet-fed mice

Browning white adipocytes may be a new target in anti-obesity therapy. Pentamethylquercetin (PMQ) has been shown to have anti-obesity effects in monosodium glutamate-induced obese mice. Here, we aimed to study the anti-obesity effects of PMQ in vitro and in vivo and to determine if adipose browning is involved in the mechanism underlying the anti-obesity effects of PMQ. We evaluated the effects of PMQ on cell proliferation, cell differentiation, glucose consumption, cellular lipid metabolism, and related brown gene expression in 3T3-L1 adipocytes. We also investigated the effects of PMQ in a mouse model of high-fat diet (HFD)-induced obesity. Our results demonstrated that PMQ increased the consumption of glucose, inhibited the accumulation of cellular triglycerides (TGs), and induced the expression of brown adipocyte-specific genes, such as uncoupling protein 1 (UCP-1), during the early stage of differentiation in 3T3-L1 adipocytes. In HFD mice, PMQ treatment reduced waist circumference, LEE index, white adipose tissue (WAT) weight and white adipocyte size and increased brown adipose tissue (BAT) weight. Moreover, PMQ treatment induced mitochondrial biogenesis and upregulated UCP-1 expression in WAT. These findings suggest that PMQ may induce browning of adipose tissue, a phenomenon that is at least partly related to its anti-obesity effects.

Nutrigenomic Functions of PPARs in Obesogenic Environments

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that mediate the effects of several nutrients or drugs through transcriptional regulation of their target genes in obesogenic environments. This review consists of three parts. First, we summarize current knowledge regarding the role of PPARs in governing the development of white and brown/beige adipocytes from uncommitted progenitor cells. Next, we discuss the interactions of dietary bioactive molecules, such as fatty acids and phytochemicals, with PPARs for the modulation of PPAR-dependent transcriptional activities and metabolic consequences. Lastly, the effects of PPAR polymorphism on obesity and metabolic outcomes are discussed. In this review, we aim to highlight the critical role of PPARs in the modulation of adiposity and subsequent metabolic adaptation in response to dietary challenges and genetic modifications. Understanding the changes in obesogenic environments as a consequence of PPARs/nutrient interactions may help expand the field of individualized nutrition to prevent obesity and obesity-associated metabolic comorbidities.

Flavonols in the Prevention of Diabetes-induced Vascular Dysfunction

As flavonols are present in fruits and vegetables, they are consumed in considerable amounts in the diet. There is growing evidence that the well-recognized antioxidant, anti-inflammatory, and vasorelaxant actions of flavonols may, at least in part, result from modulation of biochemical signaling pathways and kinases. It is well established that diabetes is associated with increased cardiovascular morbidity and mortality. Despite clinical management of blood glucose levels, diabetes often results in cardiovascular disease. There is good evidence that endothelial dysfunction contributes significantly to the progression of diabetic cardiovascular diseases. This review describes the biological actions of flavonols that may ameliorate adverse cardiovascular events in diabetes. We discuss evidence that flavonols may be developed as novel pharmacological agents to prevent diabetes-induced vascular dysfunction.

Search for new type of PPARγ agonist-like anti-diabetic compounds from medicinal plants

Potent ligands of peroxisome proliferator-activated receptor γ (PPARγ) such as thiazolidinediones (pioglitazone, troglitazone, etc.) improve insulin sensitivity by increasing the levels of adiponectin, an important adipocytokine associated with insulin sensitivity in adipose tissue. Several constituents from medicinal plants were recently reported to show PPARγ agonist-like activity in 3T3-L1 cells, but did not show agonistic activity at the receptor site different from thiazolidinediones. Our recent studies on PPARγ agonist-like constituents, such as hydrangenol and hydrangeic acid from the processed leaves of Hydrangea macrophylla var. thunbergii, piperlonguminine and retrofractamide A from the fruit of Piper chaba, and tetramethylkaempferol and pentamethylquercetin from the rhizomes of Kaempferia parviflora, are reviewed.

Pentamethylquercetin generates beneficial effects in monosodium glutamate-induced obese mice and C2C12 myotubes by activating AMP-activated protein kinase

AIMS/HYPOTHESIS

Pentamethylquercetin (PMQ) has recently been shown to have glucose-lowering properties. Here, we aimed to characterise the effectiveness and underlying mechanisms of PMQ for ameliorating metabolic disorders in vivo and vitro.

METHODS

We generated a mouse model of obesity by neonatal administration of monosodium glutamate (MSG) and used it to assess the properties of PMQ as a treatment for metabolic disorders. We also investigated the possible underlying mechanisms of PMQ in the prevention of metabolic disorders.

RESULTS

Compared with normal mice, MSG mice had metabolic disorders, including central obesity, hyperinsulinaemia, insulin resistance, hyperglycaemia, hyperlipidaemia, decreased phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), and downregulated levels of GLUT4 in gastrocnemius muscles. In MSG mice, PMQ treatment (5, 10, 20 mg/kg daily) reduced body weight gain, waist circumference, adipose tissue mass, serum glucose, triacylglycerol and total cholesterol, while improving insulin resistance, activating AMPK and increasing ACC phosphorylation and GLUT4 abundance. In C2C12 myotubes, PMQ (10 μmol/l) increased glucose consumption by ∼65%. PMQ treatment (1-10 μmol/l) also activated AMPK, increased ACC phosphorylation and GLUT4 abundance, and upregulated the expression of some key genes involved in fatty acid oxidation.

CONCLUSIONS/INTERPRETATION

These findings suggest that PMQ can ameliorate metabolic disorders at least in part via stimulation of AMPK activity.

Adiponectin: regulation of its production and its role in human diseases

Adiponectin is a white and brown adipose tissue hormone, also known as gelatin-binding protein-28 (GBP28), AdipoQ, adipocyte complement-related protein (ACRP30), or apM1. Adiponectin circulates in the bloodstream in trimeric, hexameric, and high-molecular-mass species, while different forms of adiponectin have been found to play distinct roles in the balance of energy homoeostasis. Adiponectin is an insulin sensitizing hormone that exerts its action through its receptors AdipoR1, AdipoR2, and T-cadherin. AdipoR1 is expressed abundantly in muscle, whereas AdipoR2 is predominantly expressed in the liver. Adiponectin is inversely proportional to obesity, diabetes, and other insulin-resistant states. In this review we present the current findings regarding the regulation of its production and several new findings pertaining to its biological effects. Adiponectin enhances AMPK and the PPARα pathway in the liver and skeletal muscle. Adiponectin increases fatty acids oxidation, which lowers circulating free fatty acids and prevents insulin resistance. Adiponectin has been reported to exert an antiatherosclerotic effect. It inhibits macrophage activation and foam cell accumulation, while it also augments endothelial nitrous oxide production and protects the vasculature by reducing platelet aggregation and vasodilation. Apart from causing metabolic dysfunction, adiponectin deficiency may also contribute to coronary heart disease, steatohepatitis, insulin resistance, nonalcoholic fatty liver disease, and a wide array of cancers. In this study, we present ample evidence that adiponectin mediates multiple molecular pathways. We therefore support the concept that it shows distinct potential for being of therapeutic value in the treatment of obesity related diseases, ranging from metabolic syndrome to malignancies.

Anti-inflammatory activity of alkaloids: an update from 2000 to 2010

Many natural substances with proven anti-inflammatory activity have been isolated throughout the years. The aim of this review is to review naturally sourced alkaloids with anti-inflammatory effects reported from 2000 to 2010. The assays were conducted mostly in vivo, and carrageenan-induced pedal edema was the most used experimental model. Of the 49 alkaloids evaluated, 40 demonstrated anti-inflammatory activity. Of these the most studied type were the isoquinolines. This review was based on NAPRALERT data bank, Web of Science and Chemical Abstracts. In this review, 95 references are cited.