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Find video protocols related to scientific articles indexed in Pubmed.
Prenylation modulates the bioavailability and bioaccumulation of dietary flavonoids.
Arch. Biochem. Biophys.
PUBLISHED: 02-21-2014
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Prenylflavonoids are distributed widely in the plant kingdom and have attracted appreciable attention because of their potential benefits for human health. Prenylation may be a promising tool for applying the biological functions of flavonoids to clinical uses. The bioavailability and bioaccumulation of prenylflavonoids have not been clarified, but extensive studies have been accomplished on their biological functions. This review provides current knowledge on the bioavailability of prenylflavonoids, including their absorption and metabolism in the intestine, as well as their bioaccumulation in specific tissues. Despite higher uptake into epithelial cells of the digestive tract, the bioavailability of single-dose prenylflavonoids seems to be lower than that of the parent flavonoids. Efflux from epithelial cells to the blood circulation is likely to be restricted by prenyl groups, resulting in insufficient increase in the plasma concentration. Rodent studies have revealed that prenylation enhances accumulation of naringenin in muscle tissue after long-term feeding; and that prenylation accelerates accumulation of quercetin in liver tissue. Efflux from hepatocytes to blood and enterohepatic circulations may be restricted by prenyl groups, thereby promoting slow excretion of prenylflavonoids from the blood circulation and efficient uptake to tissues. The hepatotoxicity and other deleterious effects, taken together with beneficial effects, should be considered because unexpectedly high accumulation may occur in some tissues after long-term supplementation.
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Specific localization of quercetin-3-O-glucuronide in human brain.
Arch. Biochem. Biophys.
PUBLISHED: 01-17-2014
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In recent years, many papers have suggested that dietary flavonoids may exert beneficial effects in the brain tissue for the protection of neurons against oxidative stress and inflammation. However, the bioavailability of flavonoids across the blood-brain barrier and the localization in the brain remain controversial. Thus, we examined the localization of quercetin-3-O-glucuronide (Q3GA), a major phase-II metabolite of quercetin, in the human brain tissues with or without cerebral infarction by immunohistochemical staining using anti-Q3GA antibody. A significant immunoreactivity was observed in the epithelial cells of the choroid plexus, which constitute the structural basis of the blood-cerebrospinal fluid (CSF) barrier, and in the foamy macrophages of recent infarcts. The cellular accumulation of Q3GA was also reproduced in vitro in macrophage-like RAW264, microglial MG6, and brain capillary endothelial RBEC1. It is of interest that a common feature of these cell lines is the deconjugation of Q3GA, resulting in the cellular accumulation of non-conjugated quercetin and the methylated forms. We then examined the anti-inflammatory activity of Q3GA and the deconjugated forms in the lipopolysaccharide-stimulated macrophage cells and revealed that the deconjugated forms (quercetin and a methylated form isorhamnetin), but not Q3GA itself, exhibited inhibitory effects on the inflammatory responses through attenuation of the c-Jun N-terminal kinase pathway. These results suggested that a quercetin glucuronide can pass through the blood-brain barrier, perhaps the CSF barrier, accumulate in specific types of cells, such as macrophages, and act as anti-inflammatory agents in the brain through deconjugation into the bioactive non-conjugated forms.
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Location of ?-tocopherol and ?-tocotrienol to heterogeneous cell membranes and inhibition of production of peroxidized cholesterol in mouse fibroblasts.
Springerplus
PUBLISHED: 01-01-2014
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?-Tocopherol (?-T) and ?-tocotrienol (?-T3) are well recognized as lipophilic antioxidants. Nevertheless, there is limited knowledge on their location in heterogeneous cell membranes. We first investigated the distribution of ?-T and ?-T3 to the cholesterol-rich microdomains (lipid rafts and caveolae) of heterogeneous cell membranes by incubating these antioxidants with cultured mouse fibroblasts.
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Cholesterol hydroperoxides and their degradation mechanism.
Subcell. Biochem.
PUBLISHED: 01-01-2014
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Cholesterol is one of the oxidizable lipids constituting biomembranes and plasma lipoproteins. Cholesterol hydroperoxides (Chol-OOH) are the primary products if cholesterol is subjected to attack by reactive oxygen species. In particular, singlet molecular oxygen reacts with cholesterol to yield cholesterol 5?-hydroperoxide as the major hydroperoxide species. Chol-OOH may accumulate in biological systems because of its resistance to glutathione-dependent enzymatic detoxification reactions. Their degradation products (including hydroxycholesterol and 7-ketocholesterol) participate in the pathophysiological functions of oxysterols. Highly reactive cholesterol 5,6-secosterol present in atherosclerotic lesions can be derived from the degradation of cholesterol 5?-hydroperoxide. Chol-OOH themselves may affect the lipid rafts of biomembranes, thereby leading to the modification of signal transduction pathways.
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Isoflavones derived from soy beans prevent MuRF1-mediated muscle atrophy in C2C12 myotubes through SIRT1 activation.
J. Nutr. Sci. Vitaminol.
PUBLISHED: 09-26-2013
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Proinflammatory cytokines are factors that induce ubiquitin-proteasome-dependent proteolysis in skeletal muscle, causing muscle atrophy. Although isoflavones, as potent antioxidative nutrients, have been known to reduce muscle damage during the catabolic state, the non-antioxidant effects of isoflavones against muscle atrophy are not well known. Here we report on the inhibitory effects of isoflavones such as genistein and daidzein on muscle atrophy caused by tumor necrosis factor (TNF)-? treatment. In C2C12 myotubes, TNF-? treatment markedly elevated the expression of the muscle-specific ubiquitin ligase MuRF1, but not of atrogin-1, leading to myotube atrophy. We found that MuRF1 promoter activity was mediated by acetylation of p65, a subunit of NF?B, a downstream target of the TNF-? signaling pathway; increased MuRF1 promoter activity was abolished by SIRT1, which is associated with deacetylation of p65. Of interest, isoflavones induced expression of SIRT1 mRNA and phosphorylation of AMP kinase, which is well known to stimulate SIRT1 expression, although there was no direct effect on SIRT1 activation. Moreover, isoflavones significantly suppressed MuRF1 promoter activity and myotube atrophy induced by TNF-? in C2C12 myotubes. These results suggest that isoflavones suppress myotube atrophy in skeletal muscle cells through activation of SIRT1 signaling. Thus, the efficacy of isoflavones could provide a novel therapeutic approach against inflammation-related muscle atrophy.
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Prenylation enhances quercetin uptake and reduces efflux in Caco-2 cells and enhances tissue accumulation in mice fed long-term.
J. Nutr.
PUBLISHED: 07-31-2013
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Prenyl flavonoids are widely distributed in plant foods and have attracted appreciable attention in relation to their potential benefits for human health. Prenylation may enhance the biological functions of flavonoids by introducing hydrophobic properties in their basic structures. Previously, we found that 8-prenyl naringenin exerted a greater preventive effect on muscle atrophy than nonprenylated naringenin in a mouse model. Here, we aimed to estimate the effect of prenylation on the bioavailability of dietary quercetin (Q). The cellular uptake of 8-prenyl quercetin (PQ) and Q in Caco-2 cells and C2C12 myotube cells was examined. Prenylation significantly enhanced the cellular uptake by increasing the lipophilicity in both cell types. In Caco-2 cells, efflux of PQ to the basolateral side was <15% of that of Q, suggesting that prenylation attenuates transport from the intestine to the circulation. After intragastric administration of PQ or Q to mice or rats, the area under the concentration-time curve for PQ in plasma and lymph was 52.5% and 37.5% lower than that of Q, respectively. PQ and its O-methylated form (MePQ) accumulated at much higher amounts than Q and O-methylated Q in the liver (Q: 3400%; MePQ: 7570%) and kidney (Q: 385%; MePQ: 736%) of mice after 18 d of feeding. These data suggest that prenylation enhances the accumulation of Q in tissues during long-term feeding, even though prenylation per se lowers its intestinal absorption from the diet.
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Non-selective distribution of isomeric cholesterol hydroperoxides to microdomains in cell membranes and activation of matrix metalloproteinase activity in a model of dermal cells.
Chem. Phys. Lipids
PUBLISHED: 04-11-2013
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Cholesterol hydroperoxides (ChOOHs) are included as lipid peroxidation products in the skin exposed to ultraviolet (UV) light irradiation. They may exert physicochemical actions affecting biomembrane rigidity because cholesterol is one of the major components of cell membranes. We investigated the distribution of isomeric ChOOHs in heterogeneous cell membranes with different lipid profiles using mouse fibroblast NIH-3T3 cells as a model of the dermis. Before and after UVA irradiation in the presence of hematoporphyrin, cell membranes were partitioned to microdomains (lipid rafts and caveolae) containing a higher amount of cholesterol and non-microdomains (containing a lower amount of cholesterol) by ultracentrifugation. By a combination of diphenylpyrenylphosphine-thin-layer chromatography blotting analyses and gas chromatography-electron ionization-mass spectrometry/selected ion monitoring analyses, ChOOH isomers were determined as their trimethylsilyloxyl derivatives. Cholesterol 5?-, 7?- and 7?-hydroperoxide were found as isomeric ChOOHs before irradiation. The amounts of the three ChOOH isomers increased significantly after photoirradiation for 2h. No difference was observed between microdomains and non-microdomains with regard to the ratio of the amounts of isomeric ChOOHs to that of cholesterol, suggesting that these ChOOH isomers were distributed equally in both parts depending on cholesterol content. When cells were treated with a purified mixture of ChOOH isomers, cell membranes incorporated ChOOHs into microdomains as well as non-microdomains evenly. Cellular matrix metalloproteinase-9 (MMP-9) activity was elevated by treatment with the purified mixture of ChOOH isomers. These results strongly suggest that ChOOHs accumulate in cell membranes irrespective of the heterogeneous microstructure and promote MMP activity if dermal cells are exposed to photodynamic actions.
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Soy Glycinin Contains a Functional Inhibitory Sequence against Muscle-Atrophy-Associated Ubiquitin Ligase Cbl-b.
Int J Endocrinol
PUBLISHED: 04-07-2013
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Background. Unloading stress induces skeletal muscle atrophy. We have reported that Cbl-b ubiquitin ligase is a master regulator of unloading-associated muscle atrophy. The present study was designed to elucidate whether dietary soy glycinin protein prevents denervation-mediated muscle atrophy, based on the presence of inhibitory peptides against Cbl-b ubiquitin ligase in soy glycinin protein. Methods. Mice were fed either 20% casein diet, 20% soy protein isolate diet, 10% glycinin diet containing 10% casein, or 20% glycinin diet. One week later, the right sciatic nerve was cut. The wet weight, cross sectional area (CSA), IGF-1 signaling, and atrogene expression in hindlimb muscles were examined at 1, 3, 3.5, or 4 days after denervation. Results. 20% soy glycinin diet significantly prevented denervation-induced decreases in muscle wet weight and myofiber CSA. Furthermore, dietary soy protein inhibited denervation-induced ubiquitination and degradation of IRS-1 in tibialis anterior muscle. Dietary soy glycinin partially suppressed the denervation-mediated expression of atrogenes, such as MAFbx/atrogin-1 and MuRF-1, through the protection of IGF-1 signaling estimated by phosphorylation of Akt-1. Conclusions. Soy glycinin contains a functional inhibitory sequence against muscle-atrophy-associated ubiquitin ligase Cbl-b. Dietary soy glycinin protein significantly prevented muscle atrophy after denervation in mice.
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Extracellular metabolism-dependent uptake of lysolipids through cultured monolayer of differentiated Caco-2 cells.
Biochim. Biophys. Acta
PUBLISHED: 04-01-2013
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Glycerophospholipids are known to be hydrolyzed in the intestinal lumen into free fatty acids and lysophospholipids that are then absorbed by the intestinal epithelial cells. A monolayer of enterocyte-differentiated Caco-2 cell is often used to assess the intestinal bioavailability of nutrients. In this study, we examined how differentiated Caco-2 cells process lysoglycerolipids such as lysophosphatidylcholine (LPC). Our findings were twofold. (1) Caco-2 cells secreted both a lysophospholipase A-like enzyme and a glycerophosphocholine-phosphodiesterase enzyme into the apical, but not basolateral, lumen, suggesting that food-derived LPC is converted to a free fatty acid, sn-glycerol-3-phosphate, and choline through two sequential enzymatic reactions in humans. The release of the latter enzyme was differentiation-dependent. (2) Fatty acid-releasing activities toward exogenous fluorescent LPC, lysophosphatidic acid and monoacylglycerol were shown to be higher on the apical membranes of Caco-2 cells than on the basolateral membranes. These results suggest that human intestinal epithelial cells metabolize lysoglycerolipids by two distinct mechanisms involving secreted or apical-selective expression of metabolic enzymes.
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Plasma metabolites of dietary flavonoids after combination meal consumption with onion and tofu in humans.
Mol Nutr Food Res
PUBLISHED: 03-30-2013
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The effect of food combination on metabolic profile in postprandial plasma has hardly been reported. We investigated the absorption and metabolism of quercetin and soy isoflavones in humans after combination meal consumption.
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Plasma HDL reduces nonesterified fatty acid hydroperoxides originating from oxidized LDL: a mechanism for its antioxidant ability.
Lipids
PUBLISHED: 02-15-2013
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The antioxidant property of plasma high-density lipoprotein (HDL) is thought to be involved in potential anti-atherogenic effects but the exact mechanism is not known. We aimed to reveal the contribution of HDL on the elimination of lipid hydroperoxides (LOOH) derived from oxidized low-density lipoprotein (LDL). Oxidized LDL prepared by copper ion-induced oxidation contained nonesterified fatty acid hydroperoxides (FFA-OOH) and lysophosphatidylcholine (lysoPtdCho), in addition to cholesteryl ester hydroperoxides (CE-OOH) and phosphatidylcholine hydroperoxides (PtdCho-OOH). A platelet-activating factor-acetylhydrolase (PAF-AH) inhibitor suppressed formation of FFA-OOH and lysoPtdCho in oxidized LDL. Among LOOH species, FFA-OOH was preferentially reduced by incubating oxidized LDL with HDL. HDL exhibited selective FFA-OOH reducing ability if it was mixed with a liposomal solution containing FFA-OOH, CE-OOH and PtdCho-OOH. Two-electron reduction of the hydroperoxy group to the hydroxy group was confirmed by the formation of 13-hydroxyoctadecadienoic acid from 13-hydroperoxyoctadecadienoic acid in HPLC analyses. This reducing effect was also found in apolipoprotein A-1 (apoA-1). FFA-OOH released from PtdCho-OOH due to PAF-AH activity in oxidized LDL undergo two-electron reduction by the reducing ability of apoA1 in HDL. This preferential reduction of FFA-OOH may participate in the mechanism of the antioxidant property of HDL.
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Non-specific protein modifications by a phytochemical induce heat shock response for self-defense.
PLoS ONE
PUBLISHED: 02-05-2013
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Accumulated evidence shows that some phytochemicals provide beneficial effects for human health. Recently, a number of mechanistic studies have revealed that direct interactions between phytochemicals and functional proteins play significant roles in exhibiting their bioactivities. However, their binding selectivities to biological molecules are considered to be lower due to their small and simple structures. In this study, we found that zerumbone, a bioactive sesquiterpene, binds to numerous proteins with little selectivity. Similar to heat-denatured proteins, zerumbone-modified proteins were recognized by heat shock protein 90, a constitutive molecular chaperone, leading to heat shock factor 1-dependent heat shock protein induction in hepa1c1c7 mouse hepatoma cells. Furthermore, oral administration of this phytochemical up-regulated heat shock protein expressions in the livers of Sprague-Dawley rats. Interestingly, pretreatment with zerumbone conferred a thermoresistant phenotype to hepa1c1c7 cells as well as to the nematode Caenorhabditis elegans. It is also important to note that several phytochemicals with higher hydrophobicity or electrophilicity, including phenethyl isothiocyanate and curcumin, markedly induced heat shock proteins, whereas most of the tested nutrients did not. These results suggest that non-specific protein modifications by xenobiotic phytochemicals cause mild proteostress, thereby inducing heat shock response and leading to potentiation of protein quality control systems. We considered these bioactivities to be xenohormesis, an adaptation mechanism against xenobiotic chemical stresses. Heat shock response by phytochemicals may be a fundamental mechanism underlying their various bioactivities.
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Cbl-b is a critical regulator of macrophage activation associated with obesity-induced insulin resistance in mice.
Diabetes
PUBLISHED: 01-24-2013
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We previously reported the potential involvement of casitas B-cell lymphoma-b (Cbl-b) in aging-related murine insulin resistance. Because obesity also induces macrophage recruitment into adipose tissue, we elucidated here the role of Cbl-b in obesity-related insulin resistance. Cbl-b(+/+) and Cbl-b(-/-) mice were fed a high-fat diet (HFD) and then examined for obesity-related changes in insulin signaling. The HFD caused recruitment of macrophages into adipose tissue and increased inflammatory reaction in Cbl-b(-/-) compared with Cbl-b(+/+) mice. Peritoneal macrophages from Cbl-b(-/-) mice and Cbl-b-overexpressing RAW264.7 macrophages were used to examine the direct effect of saturated fatty acids (FAs) on macrophage activation. In macrophages, Cbl-b suppressed saturated FA-induced Toll-like receptor 4 (TLR4) signaling by ubiquitination and degradation of TLR4. The physiological role of Cbl-b in vivo was also examined by bone marrow transplantation and Eritoran, a TLR4 antagonist. Hematopoietic cell-specific depletion of the Cbl-b gene induced disturbed responses on insulin and glucose tolerance tests. Blockade of TLR4 signaling by Eritoran reduced fasting blood glucose and serum interleukin-6 levels in obese Cbl-b(-/-) mice. These results suggest that Cbl-b deficiency could exaggerate HFD-induced insulin resistance through saturated FA-mediated macrophage activation. Therefore, inhibition of TLR4 signaling is an attractive therapeutic strategy for treatment of obesity-related insulin resistance.
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Mitochondrial dysfunction leads to deconjugation of quercetin glucuronides in inflammatory macrophages.
PLoS ONE
PUBLISHED: 01-01-2013
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Dietary flavonoids, such as quercetin, have long been recognized to protect blood vessels from atherogenic inflammation by yet unknown mechanisms. We have previously discovered the specific localization of quercetin-3-O-glucuronide (Q3GA), a phase II metabolite of quercetin, in macrophage cells in the human atherosclerotic lesions, but the biological significance is poorly understood. We have now demonstrated the molecular basis of the interaction between quercetin glucuronides and macrophages, leading to deconjugation of the glucuronides into the active aglycone. In vitro experiments showed that Q3GA was bound to the cell surface proteins of macrophages through anion binding and was readily deconjugated into the aglycone. It is of interest that the macrophage-mediated deconjugation of Q3GA was significantly enhanced upon inflammatory activation by lipopolysaccharide (LPS). Zymography and immunoblotting analysis revealed that ?-glucuronidase is the major enzyme responsible for the deglucuronidation, whereas the secretion rate was not affected after LPS treatment. We found that extracellular acidification, which is required for the activity of ?-glucuronidase, was significantly induced upon LPS treatment and was due to the increased lactate secretion associated with mitochondrial dysfunction. In addition, the ?-glucuronidase secretion, which is triggered by intracellular calcium ions, was also induced by mitochondria dysfunction characterized using antimycin-A (a mitochondrial inhibitor) and siRNA-knockdown of Atg7 (an essential gene for autophagy). The deconjugated aglycone, quercetin, acts as an anti-inflammatory agent in the stimulated macrophages by inhibiting the c-Jun N-terminal kinase activation, whereas Q3GA acts only in the presence of extracellular ?-glucuronidase activity. Finally, we demonstrated the deconjugation of quercetin glucuronides including the sulfoglucuronides in vivo in the spleen of mice challenged with LPS. These results showed that mitochondrial dysfunction plays a crucial role in the deconjugation of quercetin glucuronides in macrophages. Collectively, this study contributes to clarifying the mechanism responsible for the anti-inflammatory activity of dietary flavonoids within the inflammation sites.
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Tissue distribution of hesperetin in rats after a dietary intake.
Biosci. Biotechnol. Biochem.
PUBLISHED: 08-07-2011
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Hesperetin, the aglycone of hesperidin present in citrus fruits, possesses various biological activities. We assessed the tissue distribution of hesperetin in rats fed with a 0.2% hesperetin diet for 4 weeks. Its highest concentration was found in the liver, and the second highest was in the aorta. The aorta is assumed to be one of the main target tissues of hesperetin for exerting its functions.
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Accumulation of orally administered quercetin in brain tissue and its antioxidative effects in rats.
Free Radic. Biol. Med.
PUBLISHED: 06-04-2011
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Quercetin is widely distributed in vegetables and herbs and has been suggested to act as a neuroprotective agent. Here, we demonstrate that quercetin can accumulate enough to exert biological activity in rat brain tissues. Homogenates of perfused rat brain without detectable hemoglobin contaminants were treated with ?-glucuronidase/sulfatase and the released quercetin and its methylated form were analyzed using high-performance liquid chromatography (HPLC) with three different detection methods. Both quercetin and the methylated form were detected in the brain of quercetin-administered rats using HPLC-UV and HPLC with electrochemical detection and were further identified using HPLC-tandem mass spectrometry. Oral administration of quercetin (50mg/kg body wt) attenuated the increased oxidative stress in the hippocampus and striatum of rats exposed to chronic forced swimming. The possible transport of quercetin derivatives into the brain tissue was reproduced in vitro by using a rat brain capillary endothelial cell line, a model of the blood-brain barrier. These results show that quercetin could be a potent nutrient that can access the brain and protect it from disorders associated with oxidative stress.
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Dietary flavonoids as cancer-preventive and therapeutic biofactors.
Front Biosci (Schol Ed)
PUBLISHED: 05-31-2011
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Flavonoids are present in many plants, and hence, in foods and ingredients derived from them. These polyphenolic compounds have attracted renewed attention as potential anticarcinogens, and the molecular mechanisms of their anticarcinogenic effects and their bioavailability have been extensively explored. In this review, we focus on the major dietary flavonoids; flavones, flavonols, and flavan-3-ols (catechins), and evaluate their roles in cancer prevention. After absorption with or without metabolic conjugation, flavonoids are transported to target organs where they exert their anticarcinogenic activity. The molecular mechanisms of the anticarcinogenic effects of flavonoids include their antagonistic effect on the aryl hydrocarbon receptor (AhR), and regulation of phase I and II drug metabolizing enzymes and phase III transporters. Experimental evidence suggests that flavonoids modulate signal transduction pathways at each stage of carcinogenesis. The interactions between flavonoids and biomolecules in vivo must be investigated in detail to identify specific targets. In addition, the potential side effects should be considered when flavonoid supplements are used for cancer prevention. Therefore, the use of flavonoids as chemopreventive agents should be further investigated to establish safe levels of flavonoid intake.
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Pharmacology in health food: metabolism of quercetin in vivo and its protective effect against arteriosclerosis.
J. Pharmacol. Sci.
PUBLISHED: 03-24-2011
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Quercetin, a member of the bioflavonoids family, has been proposed to have anti-atherogenic, anti-inflammatory, and anti-hypertensive properties leading to the beneficial effects against cardiovascular diseases. It was recently demonstrated that quercetin 3-O-?-D-glucuronide (Q3GA) is one of the major quercetin conjugates in human plasma, in which the aglycone could not be detected. Although most of the in vitro pharmacological studies have been carried out using only the quercetin aglycone form, experiments using Q3GA would be important to discover the preventive mechanisms of cardiovascular diseases by quercetin in vivo. Therefore we examined the effects of the chemically synthesized Q3GA, as an in vivo form, on vascular smooth muscle cell (VSMC) disorders related to the progression of arteriosclerosis. Platelet-derived growth factor-induced cell migration and proliferation were inhibited by Q3GA in VSMCs. Q3GA attenuated angiotensin II-induced VSMC hypertrophy via its inhibitory effect on JNK and the AP-1 signaling pathway. Q3GA scavenged 1,1-diphenyl-2-picrylhydrazyl radical measured by the electron paramagnetic resonance method. In addition, immunohistochemical studies with monoclonal antibody 14A2 targeting the Q3GA demonstrated that the positive staining specifically accumulates in human atherosclerotic lesions, but not in the normal aorta. These findings suggest Q3GA would be an active metabolite of quercetin in plasma and may have preventative effects on arteriosclerosis relevant to VSMC disorders.
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Development of singlet oxygen absorption capacity (SOAC) assay method. 2. Measurements of the SOAC values for carotenoids and food extracts.
J. Agric. Food Chem.
PUBLISHED: 03-23-2011
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Recently a new assay method that can quantify the singlet oxygen absorption capacity (SOAC) of antioxidants was proposed. In the present work, kinetic study of the reaction of singlet oxygen ((1)O(2)) with carotenoids and vegetable extracts has been performed in ethanol/chloroform/D(2)O (50:50:1, v/v/v) solution at 35 °C. Measurements of the second-order rate constants (k(Q)(S)) and the SOAC values were performed for eight kinds of carotenoids and three kinds of vegetable extracts (red paprika, carrot, and tomato). Furthermore, measurements of the concentrations of the carotenoids included in vegetable extracts were performed, using a HPLC technique. From the results, it has been clarified that the total (1)O(2)-quenching activity (that is, the SOAC value) for vegetable extracts may be explained as the sum of the product {? k(Q)(Car-i)(S) [Car-i](i)} of the rate constant (k(Q)(Car-i)(S)) and the concentration ([Car (i)]) of carotenoids included in vegetable extracts.
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Effect of quercetin and glucuronide metabolites on the monoamine oxidase-A reaction in mouse brain mitochondria.
Nutrition
PUBLISHED: 03-03-2011
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Quercetin is a flavonoid found in plant foods and herbal medicines. It possesses antidepressant-like effects in forced swimming test-loaded rodents. We wanted to clarify the mechanism of action of dietary quercetin for exerting antidepressant-like effects. The effect of quercetin and its antioxidative metabolite quercetin 3-glucuronide (Q3GA) on the activity of mouse brain mitochondrial monoamine oxidase-A (MAO-A) was evaluated by measuring the deamination product of serotonin, 5-hydroxyindole acetaldehyde (5-HIAL).
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Intragastrically administered lysophosphatidic acids protect against gastric ulcer in rats under water-immersion restraint stress.
Dig. Dis. Sci.
PUBLISHED: 01-21-2011
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Lysophosphatidic acid exerts important physiological effects on many types of animal cells through its specific binding to several G protein-coupled receptors. In particular, its potent wound-healing effect has attracted much attention. To determine whether lysophosphatidic acids in a foodstuff and Chinese medicine are effective in protecting against gastric ulcer, we subjected rats to water-immersion restraint stress.
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Conjugated quercetin glucuronides as bioactive metabolites and precursors of aglycone in vivo.
Food Funct
PUBLISHED: 11-17-2010
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Quercetin is a typical anti-oxidative flavonoid ubiquitously distributed in vegetables. It is likely to act as a bioactive compound by exerting reactive oxygen species (ROS)-scavenging activity and/or binding to specific proteins such as oxidative enzymes and transcriptional factors in signal transduction pathways. Its absorption and metabolism (as well as its molecular targets) have been extensively explored from the viewpoint of its potential for disease prevention. It is known that glucuronide and/or sulfate conjugates with or without O-methylation exclusively circulate in the human bloodstream after intake of a quercetin-containing diet. We propose that glucuronide conjugates of quercetin function not only as detoxified metabolites but hydrophilic bioactive agents to various ROS-generating systems and precursors of hydrophobic aglycone. Quercetin aglycone is assumed to emerge in the target site by the action of ?-glucuronidase activity under oxidative stress such as inflammation. The cardiovascular system and central nervous system seem to be the major targets of conjugated quercetin glucuronides circulating in the human bloodstream.
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Quercetin Prevents Unloading-Derived Disused Muscle Atrophy by Attenuating the Induction of Ubiquitin Ligases in Tail-Suspension Mice.
J. Nat. Prod.
PUBLISHED: 09-20-2010
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The effects of quercetin (1) were investigated on disused muscle atrophy using mice that underwent tail suspension. Periodic injection of 1 into the gastrocnemius muscle suppressed muscle weight loss and ubiquitin ligase expression. Compound 1 reduced the enhancement of lipid peroxidation in the muscle. Injection of N-acetyl-l-cysteine, but not flavone (2), also prevented muscle weight loss and enhancement of lipid peroxidation. These findings demonstrate that 1 can prevent disused muscle atrophy by attenuating the expression of ubiquitin ligases and that such prevention originates from its antioxidant activity.
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Singlet molecular oxygen-quenching activity of carotenoids: relevance to protection of the skin from photoaging.
J Clin Biochem Nutr
PUBLISHED: 09-13-2010
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Carotenoids are known to be potent quenchers of singlet molecular oxygen [O(2) ((1)?(g))]. Solar light-induced photooxidative stress causes skin photoaging by accelerating the generation of reactive oxygen species via photodynamic actions in which O(2) ((1)?(g)) can be generated by energy transfer from excited sensitizers. Thus, dietary carotenoids seem to participate in the prevention of photooxidative stress by accumulating as antioxidants in the skin. An in vivo study using hairless mice clarified that a O(2) ((1)?(g)) oxygenation-specific peroxidation product of cholesterol, cholesterol 5?-hydroperoxide, accumulates in skin lipids due to ultraviolet-A exposure. Matrix metalloproteinase-9, a metalloproteinase family enzyme responsible for the formation of wrinkles and sagging, was enhanced in the skin of ultraviolet-A -irradiated hairless mice. The activation of metalloproteinase-9 and the accumulation of 5?-hydroperoxide, as well as formation of wrinkles and sagging, were lowered in mice fed a ?-carotene diet. These results strongly suggest that dietary ?-carotene prevents the expression of metalloproteinase-9 (at least in part), by inhibiting the photodynamic action involving the formation of 5?-hydroperoxide in the skin. Intake of ?-Carotene therefore appears to be helpful in slowing down ultraviolet-A -induced photoaging in human skin by acting as a O(2) ((1)?(g)) quencher.
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Kinetic study of the quenching reaction of singlet oxygen by carotenoids and food extracts in solution. Development of a singlet oxygen absorption capacity (SOAC) assay method.
J. Agric. Food Chem.
PUBLISHED: 08-24-2010
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A kinetic study of the quenching reaction of singlet oxygen (1O2) with eight kinds of carotenoids and ?-tocopherol was performed in ethanol/chloroform/D2O (50:50:1, v/v/v) solution at 35 °C. The overall rate constants, kQ (=kq+kr, physical quenching+chemical reaction), for the reaction of carotenoids with 1O2 were measured, using the competition reaction method, where endoperoxide was used as a singlet oxygen generator, 2,5-diphenyl-3,4-benzofuran (DPBF) as an UV-vis absorption prove, and ?-tocopherol as a standard compound. The rate constants, kQ (S) and kQ (t1/2), were determined by analyzing the first-order rate constant (S) and the half-life (t1/2) of the decay curve of DPBF with carotenoids, respectively, showing good accordance with each other. Similar measurements were performed for tomato and carrot extracts. From the results, a new assay method that can quantify the singlet oxygen absorption capacity (SOAC) of antioxidants, including carotenoids, ?-tocopherol, and vegetable extracts, has been proposed.
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Rantes secreted from macrophages disturbs skeletal muscle regeneration after cardiotoxin injection in Cbl-b-deficient mice.
Muscle Nerve
PUBLISHED: 07-06-2010
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Deficiency of the Cbl-b ubiquitin ligase gene activates macrophages in mice. This study aimed to elucidate the pathophysiological roles of macrophages in muscle degeneration/regeneration in Cbl-b-deficient mice. We examined immune cell infiltration and cytokine expression in cardiotoxin-injected tibialis anterior muscle of Cbl-b-deficient mice. Ablation of the Cbl-b gene expression delayed regeneration of cardiotoxin-induced skeletal muscle damage compared with wild-type mice. CD8-positive T cells were still present in the damaged muscle on day 14 after cardiotoxin injection in Cbl-b-deficient mice, but there was dispersal of the same cells over that time-frame in wild-type mice. Infiltrating macrophages in Cbl-b-deficient mice showed strong expression of RANTES (regulated-on-activation, normal T cell expressed and secreted), a chemokine for CD8-positive T cells. In turn, a neutralizing antibody against RANTES significantly suppressed the infiltration of CD8-positive T cells into the muscle, resulting in restoration of the disturbed muscle regeneration. Cbl-b is an important regulatory factor for cytotoxic T-cell infiltration via RANTES production in macrophages.
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Association of serum carotenoids and tocopherols with atopic diseases in Japanese children and adolescents.
Pediatr Allergy Immunol
PUBLISHED: 04-30-2010
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The present study assessed whether serum carotenoids and tocopherols are associated with atopic diseases (eczema and asthma) in 10- and 13-yr-olds in a Japanese community. Of 2796 students attending schools in Shunan, Japan, in 2006, 396 students were randomly selected for this study using nested case-control design. Atopic diseases and dietary food intake were assessed using self-administered questionnaires, and serum antioxidants were analyzed using high-performance liquid chromatography. We found no associations between serum carotenoids and atopic diseases. However, odds ratios (OR)s for the third and fourth quartiles of serum alpha-tocopherol with atopic eczema were 0.33 (95% confidence interval: 0.15-0.73) and 0.36 (0.14-0.89), respectively, and the trend was negatively significant (P(trend) = 0.048). We did not find a significant association for asthma. In conclusion, serum alpha-tocopherol was negatively associated with the prevalence of eczema. Serum carotenoids did not show definitive protective effects in Japanese youth.
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Ingested quercetin but not rutin increases accumulation of hepatic beta-carotene in BALB/c mice.
Mol Nutr Food Res
PUBLISHED: 04-08-2010
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Beta-carotene is a carotenoid with a range of reported health benefits besides vitamin A activity. If the enzymatic conversion of beta-carotene to retinal is suppressed in the digestive tract, residual beta-carotene that reaches the tissues increases. We evaluated the function of quercetin and rutin (quercetin-3-rutinoside) to increase the accumulation of beta-carotene in vitro and in vivo in BALB/c mice. When the conversion of beta-carotene by a preparation of the murine small intestine was measured in vitro, the addition of quercetin or rutin considerably inhibited the conversion. When the levels of hepatic beta-carotene and retinoids were measured among three groups of mice fed a diet supplemented with beta-carotene plus quercetin or rutin or beta-carotene alone (four to six mice per group), quercetin increased the level of beta-carotene and decreased the level of retinol, whereas rutin did not. These results demonstrate that quercetin can suppress the conversion of beta-carotene which develops in the cytosol of small intestinal epithelial cells, and that rutin whose rutinose-moiety prevents being absorbed in the small intestine cannot suppress the conversion in vivo. This study offers a novel insight into the interaction between flavonoids and carotenoids with respect to the health benefits from the latter.
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Consultation clinics for complementary and alternative medicine at Japanese university hospitals: An analysis at Tokushima University Hospital.
Exp Ther Med
PUBLISHED: 02-02-2010
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Here, we report on a Consultation Clinic for Complementary and Alternative Medicine (CAM) which we established at Tokushima University Hospital in July of 2007 with the aim of providing person-to-person information on CAM, though not CAM therapy itself. In December of 2008, we received 55 applications for consultation, 37% concerning health foods, 37% Japanese herbal medicine (Kampo), and 26% various other topics. The consultants (nutritionists and pharmacists) communicated individually with 38 applicants; malignancies (26%) and cardiovascular disease (24%) were the main underlying concerns. To promote the quality of consultation, data was collected by means of focus group interviews concerning the perspective of the consultants. Safe and effective use of CAM requires a network of communication linking individuals, consultation teams, physicians, primary care institutions and university hospitals. To advance this goal, we plan to broaden the efforts described herein. Our findings indicate that the specific role of the consultation clinic in promoting the scientific use of CAM merits further study.
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alpha-Oligoglucosylation of a sugar moiety enhances the bioavailability of quercetin glucosides in humans.
Arch. Biochem. Biophys.
PUBLISHED: 01-30-2010
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Dietary intake of quercetin is suggested to be potentially beneficial for the prevention of various diseases. We examined the effect of alpha-oligoglucosylation of the sugar moiety of quercetin monoglucoside on its bioavailability in humans. Enzymatically modified isoquercitrin (EMIQ) was prepared by enzymatic deglycosylation and the subsequent of alpha-oligoglucosylation of quercetin 3-O-beta-rutinode (rutin). The plasma level of quercetin metabolites was instantly increased by oral intake of EMIQ and its absorption efficiency was significantly higher than that of isoquercitrin (quercetin 3-O-beta-glucoside; Q3G), and rutin. The profile of plasma quercetin metabolites after EMIQ consumption did not differ from that after Q3G consumption. The apparent log P of EMIQ indicated that EMIQ is more hydrophilic than Q3G but less than quercetin 3,4-O-beta-diglucoside. These data indicated that enzymatic alpha-oligoglucosylation to the sugar moiety is effective for enhancing the bioavailability of quercetin glucosides in humans.
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Evaluation of tolerable levels of dietary quercetin for exerting its antioxidative effect in high cholesterol-fed rats.
Food Chem. Toxicol.
PUBLISHED: 01-21-2010
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The tolerable level of dietary quercetin for exerting its antioxidative effect was evaluated in high cholesterol-fed rats, using quercetin-containing diets (31-1260 mg quercetin/kg body weight/day) and onion diets (19-94 mg quercetin aglycone equivalent/kg body weight/day), from the viewpoint of a safety assessment. After feeding for 4 weeks, the urinary 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxodG) levels of the quercetin-containing diet groups fed more than 157 mg quercetin/kg body weight/day were higher than the group fed a quercetin-free diet, although the plasma quercetin metabolite levels and plasma antioxidative activity were elevated depending on the amounts of quercetin or onion diet intake. No significant effect on body weight gain by quercetin-containing diets or onion diets was observed. However, ratios of the liver and kidney weights to the body weight were significantly increased in the quercetin-containing diet groups fed more than 314 mg and 157 mg quercetin/kg body weight/day, respectively, and in the onion diet groups fed more than 47 mg quercetin aglycone equivalent/kg body weight/day. These results indicated that the tolerable level for dietary quercetin for exerting its antioxidative effect was between 126 and 157 mg/kg/day for the quercetin diet and between 19 and 34 mg/kg/day for the onion diet.
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Quercetin metabolites and protection against peroxynitrite-induced oxidative hepatic injury in rats.
Free Radic. Res.
PUBLISHED: 08-06-2009
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Quercetin has strong antioxidant potency. Quercetin-3-O-sulphate (Q3S) and quercetin-3-O-glucuronide (Q3GA) are the main circulating metabolites after consumption of quercetin-O-glucoside-rich diets by humans. However, information about how these quercetin metabolites function in vivo is limited. Hence, this study evaluated the efficacy of Q3S and Q3GA for the protection of oxidative injury using in vitro and in vivo experiments. Peroxynitrite-mediated hepatic injury in rats was induced by administration of galactosamine/lipopolysaccharide (GalN/LPS). Twenty-four hours after GalN/LPS treatment, plasma ALT and AST levels delta increased significantly. However, pretreatment with 4(G)-alpha-D-glucopyranosyl rutin, a quercetin glycoside (30 mg/kg body weight), prevented these increases and reduced nitrotyrosine formation, indicating that consumption of quercetin glycosides prevent oxidative hepatotoxicity. Moreover, physiological levels of Q3S and Q3GA (1 microM) effectively prevented peroxynitrite-induced nitrotyrosine formation in human serum albumin in in vitro experiments. These findings indicate peroxynitrite-induced oxidative hepatotoxicity is protected by the in vivo metabolites of quercetin, Q3S and Q3GA.
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Carotenoid, tocopherol, and fatty acid biomarkers and dietary intake estimated by using a brief self-administered diet history questionnaire for older Japanese children and adolescents.
J. Nutr. Sci. Vitaminol.
PUBLISHED: 07-16-2009
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We investigated the association between nutrient biomarkers and dietary intake estimated using a brief self-administered dietary history questionnaire (BDHQ) for Japanese children and adolescents. Blood samples were collected from 398 subjects (5th graders of elementary school aged 10-11 y, and 2nd graders of secondary schools aged 13-14 y) randomly selected from among students in Shunan City, Japan, who were then required to answer two questionnaires. Spearman correlations were calculated between dietary intake and the corresponding biomarkers (serum carotenoids, tocopherols, and erythrocyte fatty acids). Correlations with beta-carotene and beta-cryptoxanthin were significant in the 13- and 14-y age group (r=0.220-0.333, p<0.030) and the 10- and 11-y age subgroup who answered the questionnaire with assistance (r=0.295-0.299, respectively, p=0.006). Consumption of green-yellow vegetables and fruits was significantly correlated with beta-carotene and beta-cryptoxanthin levels (r=0.205-0.341, p<0.047). In the 13- and 14-y age group, correlations with eicosapentaenoic and docosahexaenoic acids were between 0.215 and 0.473 (p<0.040). Total seafood intake was significantly correlated with marine n-3 polyunsaturated fatty acids (PUFAs; r=0.239-0.420, p<0.023). In the 10- and 11-y age subgroup who completed the questionnaire with assistance, seafood intake was significantly correlated with marine n-3 PUFAs (r=0.239-0.243, p<0.032). In conclusion, dietary intake assessed using the BDHQ reflects the corresponding biomarkers for 13- and 14-y-olds; however, when used for elementary school children, caution is necessary in interpreting the results.
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Peroxidized cholesterol-induced matrix metalloproteinase-9 activation and its suppression by dietary beta-carotene in photoaging of hairless mouse skin.
J. Nutr. Biochem.
PUBLISHED: 06-26-2009
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The activation of matrix metalloproteinase (MMP)-9 leading to the formation of wrinkle and sagging of skin is an essential step in the skin photoaging on exposure to ultraviolet A (UVA). This study attempted to elucidate the role of peroxidized cholesterol including cholesterol hydroperoxides (Chol-OOHs), primary products of lipid peroxidation in biomembranes, in MMP-9 activation and the effect of dietary beta-carotene in MMP-9 activation. Hairless mice were subjected to periodic UVA irradiation for 8 weeks. The amount of peroxidized cholesterol detected as total hydroxycholesterol in the skin was increased significantly by the exposure. The activity and protein level of MMP-9 were elevated with wrinkling and sagging formation. MMP-9 activity was also enhanced by the intracutaneous injection of Chol-OOHs into the mouse skin. Adding beta-carotene to the diet of the mice during the period of irradiation suppressed the activity and expression of MMP-9 as well as the wrinkling and sagging formation. The amount of cholesterol 5alpha-hydroperoxide, a singlet molecular oxygen oxygenation-specific peroxidized cholesterol, was significantly lowered by the addition of beta-carotene to the diet. These results strongly suggest that Chol-OOHs formed on exposure to UVA contribute to the expression of MMP-9, resulting in photoaging. Dietary beta-carotene prevents the expression of MMP-9, at least partly, by inhibiting photodynamic action involved in the formation of Chol-OOHs.
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Dietary flavonoids as antioxidants.
Forum Nutr
PUBLISHED: 04-07-2009
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Flavonoids are ubiquitously present in fruits and vegetables. They have attracted much attention in relation to prevention of degenerative diseases such as atherosclerosis. Their antioxidant activity should be at least partly responsible for such prevention. The mechanism of antioxidant activity of flavonoids can be characterized by direct scavenging or quenching of oxygen free radicals or excited oxygen species as well as inhibition of oxidative enzymes that generate these reactive oxygen species. The essential part of the free radical-scavenging activity of flavonoids is attributed to the o-dihydroxyl group in the B ring (catechol group) in their diphenylpropane structure. Catechol typeflavonoids therefore possess powerful antioxidant activity. Conjugation of glucuronide/sulfate during intestinal absorption attenuates their antioxidant activity, but some metabolites containing an o-dihydroxyl structure, such as quercetin 3-O-beta-d-glucuronide (Q3GA), retain considerable antioxidant activity. Q3GA was found to be effective in the inhibition of lipid hydroperoxide-induced oxidative stress in the nerve cell model PC-12. Our in vivo study using high cholesterol-fed rabbits also showed accumulation of quercetin metabolites in aortic tissue, and inhibition of deposition of cholesteryl ester hydroperoxide. It is evident that quercetin metabolites are distributed in human atherosclerotic lesions, particularly the macrophage-derived foam cell. The specific target should therefore be taken into account when evaluating the antioxidant activity of dietary flavonoids in vivo.
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Dietary quercetin inhibits bone loss without effect on the uterus in ovariectomized mice.
J. Bone Miner. Metab.
PUBLISHED: 03-30-2009
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Quercetin is a major dietary flavonoid found in onions and other vegetables, and potentially has beneficial effects on disease prevention. In the present study, we demonstrate for the first time the effects of dietary quercetin on bone loss and uterine weight loss by ovariectomy in vivo. Female mice were ovariectomized (OVX) and were randomly allocated to 3 groups: a control diet or a diet with 0.25% (LQ) or 2.5% quercetin (HQ). After 4 weeks, dietary quercetin had no effects on uterine weight in OVX mice, but bone mineral density of the lumbar spine L4 and femur measured by peripheral quantitative computed tomography (pQCT) was higher in both the sham and the HQ groups than in the OVX group. Histomorphometric analysis showed that the HQ group restored bone volume (BV/TV) completely in distal femoral cancellous bone, but did not reduce the osteoclast surface area and osteoclast number when compared with the OVX group. In in-vitro experiments using mouse monocyte/macrophage cell line RAW264.7 cells, however, quercetin and its conjugate, quercetin-3-O-beta-D: -glucuronide dose-dependently inhibited the receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclast differentiation, and the RANKL-stimulated expression of osteoclast related genes was also inhibited by quercetin. The luciferase reporter assay showed that quercetin did not appear to have estrogenic activity through estrogen receptors. These results suggest that dietary quercetin inhibits bone loss without effect on the uterus in OVX mice and does not act as a potent inhibitor of osteoclastogenesis or as a selective estrogen receptor modulator in vivo.
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Different profiles of quercetin metabolites in rat plasma: comparison of two administration methods.
Biosci. Biotechnol. Biochem.
PUBLISHED: 03-07-2009
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The bioavailability of polyphenols in human and rodents has been discussed regarding their biological activity. We found different metabolite profiles of quercetin in rat plasma between two administration procedures. A single intragastric administration (50 mg/kg) resulted in the appearance of a variety of metabolites in the plasma, whereas only a major fraction was detected by free access (1% quercetin). The methylated/non-methylated metabolites ratio was much higher in the free access group. Mass spectrometric analyses showed that the fraction from free access contained highly conjugated quercetin metabolites such as sulfo-glucuronides of quercetin and methylquercetin. The metabolite profile of human plasma after an intake of onion was similar to that with intragastric administration in rats. In vitro oxidation of human low-density lipoprotein showed that methylation of the catechol moiety of quercetin significantly attenuated the antioxidative activity. These results might provide information about the bioavailability of quercetin when conducting animal experiments.
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Polyphenols prevent clinorotation-induced expression of atrogenes in mouse C2C12 skeletal myotubes.
J. Med. Invest.
PUBLISHED: 03-06-2009
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Oxidative stress is a key factor in stimulating the expression of atrogenes, which are muscle atrophy-related ubiquitin ligases, in skeletal muscle, and it induces muscle atrophy during unloading. However, the effects of antioxidative nutrients on atrogene expression have not been demonstrated. We report on the inhibitory effects of polyphenols, such as epicatechin (EC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg) and quercetin, on atrogene expression up-regulated by three dimensional (3D)-clinorotation or glucocorticoid. These treatments markedly elevated the expression of atrogenes, including atrogin-1 and MuRF-1, in mouse C2C12 myoblasts and myotubes. Interestingly, EC, ECg, EGCg and quercetin significantly decreased the expression of atrogin-1 and MuRF-1 up-regulated by 3D-clinorotation, whereas they hardly affected atrogene expression induced by dexamethasone. ERK signaling is a well known MAPK pathway to mediate oxidative stress. Therefore, we also investigated the effect of these polyphenols on phosphorylation of ERK in C2C12 myotubes. As expected, EC, ECg, EGCg, and quercetin significantly suppressed phosphorylation of ERK, corresponding to the up-regulation of atrogenes induced by 3D-clinorotation. These results suggest that antioxidative nutrients, such as catechins and quercetin, suppress atrogene expression in skeletal muscle cells, possibly through the inhibition of ERK signaling. Thus, catechins and quercetin may prevent unloading-mediated muscle atrophy.
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Suppressive effect of quercetin on acute stress-induced hypothalamic-pituitary-adrenal axis response in Wistar rats.
J. Nutr. Biochem.
PUBLISHED: 01-06-2009
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The flavonoid quercetin is considered to have beneficial effects on human health. We recently have shown that quercetin-enriched foods reduced the duration of immobility time in a rat forced swimming test, indicating that dietary quercetin is promising as an antidepressant-like factor, whereas its mechanism of action is poorly understood. The aim of this study is to investigate the effects of quercetin on water immersion-restraint (WIR), stress-induced hypothalamic-pituitary-adrenal (HPA) axis activation, which is a major component of stress response and plays an important role in the pathology of depression. Quercetin administration to rats significantly suppressed WIR stress-induced increase of plasma corticosterone and adrenocorticotropic hormone levels as well as the mRNA expression of corticotropin-releasing factor (CRF) in the hypothalamic region. In addition, quercetin modulated the DNA binding activities of glucocorticoid receptor and phosphorylated cyclic adenosine 3,5-monophosphate (cAMP) response element binding protein as well as the phosphorylation of extracellular signal-regulated kinase 1/2 in the hypothalamic region, all of which are known to regulate the expression of CRF mRNA. Taken together, these results suggest that dietary quercetin attenuates the HPA axis activation by the suppression of the CRF mRNA expression.
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Influence of fatty acid patterns on the intestinal absorption pathway of quercetin in thoracic lymph duct-cannulated rats.
Br. J. Nutr.
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Since it is known that dietary fats improve the bioavailability of the flavonol quercetin, we purposed to investigate whether this effect is due to increased lymphatic transport of quercetin. In rats with implanted catheters in the thoracic lymph duct, we administered quercetin into the duodenum with TAG emulsions containing either long-chain fatty acids (LCT) or medium-chain fatty acids (MCT). Controls received quercetin together with a glucose solution. LCT administration increased the lymphatic output of quercetin (19.1 (SEM 1.2) nmol/8 h) as well as the lymph-independent bioavailability of the flavonol, determined as area under the plasma concentration curve (1091 (SEM 142) microM x min). Compared with glucose administration, MCT neither increased the lymphatic output (12.3 (SEM 1.5) nmol/8 h) nor the bioavailability of quercetin (772 (SEM 99) microM x min) significantly (glucose group: 9.8 (SEM 1.5) nmol/8 h and 513 (SEM 55) microM x min, respectively). Because LCT are released within chylomicrons into the intestinal lymph while MCT are mainly released into the portal blood, we conclude from the present results that dietary fats that are mainly composed of LCT improve quercetin bioavailability by increasing its transport via the lymph, thereby circumventing hepatic first-pass metabolism of the flavonol. In addition, LCT could enhance quercetin absorption by improving its solubility in the intestinal tract.
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Blueberry intervention improves vascular reactivity and lowers blood pressure in high-fat-, high-cholesterol-fed rats.
Br. J. Nutr.
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Growing evidence suggests that intake of flavonoid-containing foods may exert cardiovascular benefits in human subjects. We have investigated the effects of a 10-week blueberry (BB) supplementation on blood pressure (BP) and vascular reactivity in rats fed a high-fat/high-cholesterol diet, known to induce endothelial dysfunction. Rats were randomly assigned to follow a control chow diet, a chow diet supplemented with 2 % (w/w) BB, a high-fat diet (10 % lard; 0·5 % cholesterol) or the high fat plus BB for 10 weeks. Rats supplemented with BB showed significant reductions in systolic BP (SBP) of 11 and 14 %, at weeks 8 and 10, respectively, relative to rats fed the control chow diet (week 8 SBP: 107·5 (SEM 4·7) v. 122·2 (SEM 2·1) mmHg, P= 0·018; week 10 SBP: 115·0 (SEM 3·1) v. 132·7 (SEM 1·5) mmHg, P< 0·0001). Furthermore, SBP was reduced by 14 % in rats fed with the high fat plus 2 % BB diet at week 10, compared to those on the high-fat diet only (SBP: 118·2 (SEM 3·6) v. 139·5 (SEM 4·5) mmHg, P< 0·0001). Aortas harvested from BB-fed animals exhibited significantly reduced contractile responses (to L-phenylephrine) compared to those fed the control chow or high-fat diets. Furthermore, in rats fed with high fat supplemented with BB, aorta relaxation was significantly greater in response to acetylcholine compared to animals fed with the fat diet. These data suggest that BB consumption can lower BP and improve endothelial dysfunction induced by a high fat, high cholesterol containing diet.
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Prevention of disuse muscle atrophy by dietary ingestion of 8-prenylnaringenin in denervated mice.
PLoS ONE
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Flavonoids have attracted considerable attention in relation to their effects upon health. 8-Prenylnaringenin (8-PN) is found in the common hop (Humulus lupulus) and assumed to be responsible for the health impact of beer consumption. We wanted to clarify the effects of prenylation on the physiological functions of dietary flavonoids by comparing the effects of 8-PN with that of intact naringenin in the prevention of disuse muscle atrophy using a model of denervation in mice. Consumption of 8-PN (but not naringenin) prevented loss of weight in the gastrocnemius muscle further supported by the lack of induction of the protein content of a key ubiquitin ligase involved in muscle atrophy, atrogin-1, and by the activation of Akt phosphorylation. 8-PN content in the gastrocnemius muscle was tenfold higher than that of naringenin. These results suggested that, compared with naringenin, 8-PN was effectively concentrated into skeletal muscle to exert its preventive effects upon disuse muscle atrophy. It is likely that prenylation generates novel functions for 8-PN by enhancing its accumulation into muscle tissue through dietary intake.
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Evaluation of the inhibitory effects of quercetin-related flavonoids and tea catechins on the monoamine oxidase-A reaction in mouse brain mitochondria.
J. Agric. Food Chem.
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Quercetin, a typical dietary flavonoid, is thought to exert antidepressant effects by inhibiting the monoamine oxidase-A (MAO-A) reaction, which is responsible for regulation of the metabolism of the neurotransmitter 5-hydroxytryptamine (5-HT) in the brain. This study compared the MAO-A inhibitory activity of quercetin with those of O-methylated quercetin (isorhamnetin, tamarixetin), luteolin, and green tea catechins ((-)-epicatechin, (-)-epicatechin gallate, (-)-epigallocatechin, and (-)-epigallocatechin gallate) by measuring the formation of the oxidative deamination product of 5-HT, 5-hydroxyindole aldehyde (5-HIAL), in mouse brain mitochondria. Quercetin was inferior to luteolin in the inhibition of MAO-A activity, whereas isorhamnetin, tamarixetin, and tea catechins scarcely exerted inhibitory activity. Quercetin did not affect MAO-A activity in mouse intestinal mitochondria, indicating that it does not evoke side effects on the metabolism of dietary monoamines in the gut. These data suggest that quercetin is a weak (but safe) MAO-A inhibitor in the modulation of 5-HT levels in the brain.
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Development of singlet oxygen absorption capacity (SOAC) assay method. 3. Measurements of the SOAC values for phenolic antioxidants.
J. Agric. Food Chem.
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Measurements of the singlet oxygen ((1)O(2)) quenching rates (k(Q) (S)) and the relative singlet oxygen absortpion capacity (SOAC) values were performed for 16 phenolic antioxidants (tocopherol derivatives, ubiquinol-10, caffeic acids, and catechins) and vitamin C in ethanol/chloroform/D(2)O (50:50:1, v/v/v) solution at 35 °C. It has been clarified that the SOAC method is useful to evaluate the (1)O(2)-quenching activity of lipophilic and hydrophilic antioxidants having 5 orders of magnitude different rate constants from 1.38 × 10(10) M(-1) s(-1) for lycopene to 2.71 × 10(5) for ferulic acid. The logarithms of the k(Q) (S) and the SOAC values for phenolic antioxidants were found to correlate well with their peak oxidation potentials (E(p)); the antioxidants that have smaller E(p) values show higher reactivities. In previous works, measurements of the k(Q) (S) values for many phenolic antioxidants were performed in ethanol. Consequently, measurements of the k(Q) (S) and relative SOAC values were performed for eight carotenoids in ethanol to investigate the effect of solvent on the (1)O(2)-quenching rate. The k(Q) (S) values for phenolic antioxidants and carotenoids in ethanol were found to correlate linearly with the k(Q) (S) values in ethanol/chloroform/D(2)O solution with a gradient of 1.79, except for two catechins. As the relative rate constants (k(Q)(AO) (S)/k(Q)(?-Toc) (S)) of antioxidants (AO) are equal to the relative SOAC values, the SOAC values do not depend on the kinds of solvent used, if ?-tocopherol is used as a standard compound. In fact, the SOAC values obtained for carotenoids in mixed solvent agreed well with the corresponding ones in ethanol.
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Effect of quercetin and its glucuronide metabolite upon 6-hydroxydopamine-induced oxidative damage in Neuro-2a cells.
Free Radic. Res.
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Quercetin is ubiquitously distributed in plant foods. This antioxidative polyphenol is mostly converted to conjugated metabolites in the body. Parkinson disease (PD) has been suggested to be related to oxidative stress derived from abnormal dopaminergic activity. We evaluated if dietary quercetin contributes to the antioxidant network in the central nervous system from the viewpoint of PD prevention. A neurotoxin, 6-hydroxydopamine (6-OHDA), was used as a model of PD. 6-OHDA-induced H?O? production and cell death in mouse neuroblastoma, Neuro-2a. Quercetin aglycone suppressed 6-OHDA-induced H?O? production and cell death, although aglycone itself reduced cell viability at higher concentration. Quercetin 3-O-?-D-glucuronide (Q3GA), which is an antioxidative metabolite of dietary quercetin, was little incorporated into the cell resulting in neither suppression of 6-OHDA-induced cell death nor reduction of cell viability. Q3GA was found to be deconjugated to quercetin by microglial MG-6 cells. These results indicate that quercetin metabolites should be converted to their aglycone to exert preventive effect on damage to neuronal cells.
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Unloading stress disturbs muscle regeneration through perturbed recruitment and function of macrophages.
J. Appl. Physiol.
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Skeletal muscle is one of the most sensitive tissues to mechanical loading, and unloading inhibits the regeneration potential of skeletal muscle after injury. This study was designed to elucidate the specific effects of unloading stress on the function of immunocytes during muscle regeneration after injury. We examined immunocyte infiltration and muscle regeneration in cardiotoxin (CTX)-injected soleus muscles of tail-suspended (TS) mice. In CTX-injected TS mice, the cross-sectional area of regenerating myofibers was smaller than that of weight-bearing (WB) mice, indicating that unloading delays muscle regeneration following CTX-induced skeletal muscle damage. Delayed infiltration of macrophages into the injured skeletal muscle was observed in CTX-injected TS mice. Neutrophils and macrophages in CTX-injected TS muscle were presented over a longer period at the injury sites compared with those in CTX-injected WB muscle. Disturbance of activation and differentiation of satellite cells was also observed in CTX-injected TS mice. Further analysis showed that the macrophages in soleus muscles were mainly Ly-6C-positive proinflammatory macrophages, with high expression of tumor necrosis factor-? and interleukin-1?, indicating that unloading causes preferential accumulation and persistence of proinflammatory macrophages in the injured muscle. The phagocytic and myotube formation properties of macrophages from CTX-injected TS skeletal muscle were suppressed compared with those from CTX-injected WB skeletal muscle. We concluded that the disturbed muscle regeneration under unloading is due to impaired macrophage function, inhibition of satellite cell activation, and their cooperation.
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Bioavailability of orally administered water-dispersible hesperetin and its effect on peripheral vasodilatation in human subjects: implication of endothelial functions of plasma conjugated metabolites.
Food Funct
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Hesperetin is an aglycone of citrus flavonoids and is expected to exert a vasodilatation effect in vivo. We developed water-dispersible hesperetin by the process of micronization to enhance the bioavailability of hesperetin. This study aimed to assess the effect of this process on the bioavailability of hesperetin and to estimate its efficiency on vasodilatation-related functions using endothelial cells in vitro and a human volunteer study at a single dose in vivo. We found that water-dispersible hesperetin was absorbed rapidly, with its maximum plasma concentration (C(max)) being 10.2 ± 1.2 ?M, and that the time to reach C(max), which is within 1 h if 150 mg of this preparation was orally administered in humans. LC-MS analyses of the plasma at C(max) demonstrated that hesperetin accumulated in the plasma as hesperetin 7-O-?-D-glucuronide (Hp7GA), hesperetin 3-O-?-D-glucuronide (Hp3GA) and hesperetin sulfate exclusively. Similar to hesperetin, Hp7GA enhanced nitric oxide (NO) release by inhibiting nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) activity in a human umbilical vein endothelial cell culture system, indicating that plasma hesperetin metabolites can improve vasodilatation in the vascular system. A volunteer study using women with cold sensitivity showed that a single dose of water-dispersible hesperetin was effective on peripheral vasodilatation.These results strongly suggest that rapid accumulation with higher plasma concentration enables hesperetin to exert a potential vasodilatation effect by the endothelial action of its plasma metabolites. Water-dispersible hesperetin may be useful to improve the health effect of dietary hesperetin.
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