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1.
Recent evidence strongly suggests that oxidative stress due to redox imbalance is highly associated with metabolic syndrome. The objective of this study was to evaluate the effect of the supplementation of longan flower water extract (LFWE), which showed powerful antioxidative activity in vitro, on markers of metabolic syndrome in a fructose-fed rat model. Male Sprague-Dawley rats were randomly divided into four groups: group C, fed with standard Purina chow; group F, fed with high-fructose diet (HF) alone; group L, fed with HF plus LFWE 125 mg/kg bw per day by gavage; and group H, fed HF plus LFWE 250 mg/kg bw per day by gavage. The dietary manipulation lasted for 14 weeks. Results of our study showed that rats fed with HF resulted in oxidative stress and affected the antioxidant status including plasma thiobarbituric acid and liver antioxidant enzyme activity. Treatment with LFWE significantly augmented the antioxidant system. HF was able to cause insulin resistance and elevation of the blood pressure. The supplementation of LFWE ameliorated insulin resistance by enhancing the expression of insulin signaling pathway related proteins, including insulin receptor substrate-1 and glucose transporter 4. LFWE supplementation was also found to decrease systolic blood pressure. These findings indicate that longan flower water extract may improve the symptoms of metabolic syndrome in fructose-fed rats.  相似文献   

2.
To determine whether green tea polyphenol ameliorates the pathological conditions induced by excessive dietary arginine, green tea polyphenol was administered to rats at a daily dose of 50 or 100 mg/kg body weight for 30 days with a 2% w/w arginine diet. In arginine-fed control rats, urinary and/or serum levels of guanidino compounds, nitric oxide (NO), urea, protein, and glucose increased significantly, while the renal activities of the oxygen species-scavenging enzymes superoxide dismutase (SOD) and catalase decreased, compared with casein-fed rats. However, rats given green tea polyphenol showed significant and dose-dependent decreases in serum levels of creatinine (Cr) and urea nitrogen and urinary excretion of Cr, and they exerted a slight reduction of nitrite plus nitrate, indicating that green tea polyphenol reduced the production of uremic toxins and NO. In addition, in arginine-fed rats the urinary urea, protein, and glucose level increases were reversed by the administration of green tea polyphenol. Moreover, in rats given green tea polyphenol the SOD and catalase activities suppressed by excessive arginine administration increased dose-dependently, implying the biological defense system was augmented as a result of free radical scavenging. These results suggest that green tea polyphenol would ameliorate renal failure induced by excessive dietary arginine by decreasing uremic toxin, and NO production and increasing radical-scavenging enzyme activity.  相似文献   

3.
Green tea has antidiabetic, antiobesity, and anti-inflammatory activities in animal models, but the molecular mechanisms of these effects have not been fully understood. Quantitative real-time polymerase chain reaction (PCR) was used to investigate the relative expression levels and the effects of green tea (1 and 2 g solid extract/kg diet) on the expression of glucose transporter family genes (Glut1/Slc2a1, Glut2/Slc2a2, Glut3/Slc2a3, and Glut4/Slc2a4) and insulin signaling pathway genes (Ins1, Ins2, Insr, Irs1, Irs2, Akt1, Grb2, Igf1, Igf2, Igf1r, Igf2r, Gsk3b, Gys1, Pik3cb, Pik3r1, Shc1, and Sos1) in liver and muscle of rats fed a high-fructose diet known to induce insulin resistance and oxidative stress. Glut2 and Glut4 were the major Glut mRNAs in rat liver and muscle, respectively. Green tea extract (1 g) increased Glut1, Glut4, Gsk3b, and Irs2 mRNA levels by 110, 160, 30, and 60% in the liver, respectively, and increased Irs1 by 80% in the muscle. Green tea extract (2 g) increased Glut4, Gsk3b, and Pik3cb mRNA levels by 90, 30, and 30% but decreased Shc1 by 60% in the liver and increased Glut2, Glut4, Shc1, and Sos1 by 80, 40, 60, and 50% in the muscle. This study shows that green tea extract at 1 or 2 g/kg diet regulates gene expression in the glucose uptake and insulin signaling pathway in rats fed a fructose-rich diet.  相似文献   

4.
Soy glyceollins, induced during stress, have been shown to inhibit cancer cell growth in vitro and in vivo. In the present study, we used prediabetic rats to examine the glyceollins effect on blood glucose. During an oral glucose tolerance test (OGTT), the blood glucose excursion was significantly decreased in the rats treated with oral administration of either 30 or 90 mg/kg glyceollins. Plasma analysis demonstrated that glyceollins are absorbed after oral administration, and duration of exposure extends from 20 min to at least 4 h postadministration. Exposure of 3T3-L1 adipocytes to glyceollins significantly increased both insulin-stimulated and basal glucose uptake. Basal glucose uptake was increased 1.5-fold by exposure to 5 μM glyceollin in a dose-response manner. Coincubation with insulin significantly stimulated maximal glucose uptake above basal uptake levels and tended to increase glucose uptake beyond the levels of either stimulus alone. On a molecular level, polymerase chain reaction showed significantly increased levels of glucose transporter GLUT4 mRNA in 3T3-L1 adipocytes, especially when the cells were exposed to 5 μM glyceollins for 3 h in vitro. It correlated with elevated protein levels of GLUT4 detected in the 5 μM glyceollin-treated cells. Thus, the simulative effect of the glyceollins on adipocyte glucose uptake was attributed to up-regulation of glucose transporters. These findings indicate potential benefits of the glyceollins as an intervention in prediabetic conditions as well as a treatment for type 1 and type 2 diabetes by increasing both the insulin-mediated and the basal, insulin-independent, glucose uptake by adipocytes.  相似文献   

5.
It is known that green tea has the ability to prevent obesity, but the underlying molecular mechanism is not fully understood to date. A preventive mechanism of green tea on obesity in C57BL/6 mice fed a high-fat (HF) diet was investigated by evaluating the expression levels of obesity-related proteins in mesenteric white adipose tissue by using protein array. An increase in the expression level of insulin-like growth factor binding protein (IGFBP)-1 by green tea was found in the white adipose tissues of both control and HF diet-fed mice by protein array and confirmed by Western blot. Moreover, the expression level was negatively correlated with adipose tissue weight. In 3T3-L1 adipocytes, treatment with green tea and its major polyphenol, (-)-epigallocatechin gallate, induced the expression of IGFBP-1 in a dose-dependent manner by Western blot. In conclusion, IGFBP-1 in adipose tissue is a novel molecule target for the prevention of obesity by green tea.  相似文献   

6.
To investigate the preventive effects of tea on hyperglycemia and insulin resistance, male C57BL/6J mice were given a high-fat diet containing 29% lard and also green or black tea ad libitum for 14 weeks. Both teas suppressed body weight gain and deposition of white adipose tissue caused by the diet. In addition, they improved hyperglycemia and glucose intolerance by stimulating glucose uptake activity accompanied by the translocation of glucose transporter (GLUT) 4 to the plasma membrane in muscle. Long-term consumption of the high-fat diet reduced levels of insulin receptor β-subunit, GLUT4 and AMP-activated protein kinase α in muscle, and green and black tea suppressed these decreases. The results strongly suggest that green and black tea suppress high-fat diet-evoked hyperglycemia and insulin resistance by retaining the level of GLUT4 and increasing the level of GLUT4 on the plasma membrane in muscle.  相似文献   

7.
Antioxidative activity of green tea polyphenol in cholesterol-fed rats   总被引：17，自引：0，他引：17  
This study investigated the effects of green tea polyphenol on the serum antioxidative activity and cholesterol levels of cholesterol-fed rats and compared them with those of probucol, an antioxidant hypocholesterolemic agent. To evaluate the antioxidative activity, the susceptibility to oxidative modification of low-density lipoprotein (LDL) isolated from the serum of cholesterol-fed rats was measured, as was the serum antioxidative activity using the spontaneous autoxidation system of brain homogenate. Administration of green tea polyphenol effectively inhibited LDL oxidation and elevated serum antioxidative activity to the same degree as probucol. However, higher amounts of polyphenol than probucol needed to be administered to reduce the total, free, and LDL cholesterol levels. Furthermore, green tea polyphenol increased the levels of high-density lipoprotein (HDL) cholesterol, leading to dose-dependent improvement of the atherogenic index, an effect that was not seen with probucol. Thus, green tea polyphenol may exert an antiatherosclerotic action by virtue of its antioxidant properties and by increasing HDL cholesterol levels.  相似文献   

8.
High content isoflavone soy protein (SBP) (Abalon) has been found in animal studies to possess beneficial effects on a number of the characteristic features of the insulin resistance syndrome. The aim of this study was to investigate whether SBP exerts beneficial effects on metabolism in the diabetic KKAy-mouse. Furthermore, we investigated the long-term in vivo effect of SBP on the expression profile in islets of key insulin regulatory genes. Twenty KKAy-mice, aged 5 weeks, were divided into 2 groups and treated for 9 weeks with either (A) standard chow diet (control) or (B) chow + 50% SBP. Twenty normal C57BL-mice fed with standard chow diet served as nondiabetic controls (C). Blood samples were collected and analyzed before and after intervention. Gene expression was determined in islets by quantitative real-time RT-PCR and Affymetrix microarray. It was demonstrated that long-term treatment with SBP improves glucose homeostasis, increases insulin sensitivity, and lowers plasma triglycerides in diabetic KKAy-mice. SBP reduces fasting plasma glucose, insulin, triglycerides, and total cholesterol. Furthermore, SBP markedly changes the gene expression profile of key insulin regulatory genes GLUT2, GLUT3, Ins1, Ins2, IGF1, Beta2/Neurod1, cholecystokinin, and LDLr, and proliferative genes in islets isolated from KKAy-mice. After 9 weeks of treatment with SBP, plasma glucose and insulin homeostasis was normalized compared to start levels. The results indicate that SBP improves glucose and insulin sensitivity and up-regulates the expression of key insulin regulatory genes.  相似文献   

9.
Tea polyphenol is rich in green tea with diverse biological activities. However, its application in the food industry is limited due to its instability toward oxygen and light. In this study, the preparation of tea polyphenol liposome by the thin film ultrasonic dispersion method was performed in order to enhance the bioavailability of tea polyphenol. The process conditions were optimized using response surface analysis, and the optimal parameters were as follows: ratio of tea polyphenol to lecithin, 0.125:1; ratio of lecithin to cholesterol, 4:1; phosphate buffered saline (PBS) pH, 6.62; ultrasonic time, 3.5 min. The theoretical and practical entrapment efficiency were 60.36% and 60.09 ± 0.69%, respectively. Furthermore, physicochemical properties including size distribution, zeta potential, permeability, infrared spectrum and in vitro release of liposomal formulations were determined. The mean size of tea polyphenol liposome was 160.4 nm, and the ζ-potential value was -67.2. The tea polyphenol liposome was formed by physical interaction, and the in vitro release process followed a first-order equation. The results indicated that the prepared tea polyphenol liposome was stable and suitable for more widespread application.  相似文献   

10.
Five polymeric black tea polyphenol fractions (PBP-1-5) were isolated from a popular brand of black tea. The effect of these PBPs and epigallocatechin gallate (EGCG), a major green tea polyphenol, was studied on the formation of [(3)H]-B(a)P-derived DNA adducts in vitro, employing rat liver microsomes. PBP-1-3 inhibited microsome-catalyzed [(3)H]-B(a)P-derived DNA adduct formation in vitro in a dose-dependent manner. This inhibition was further enhanced on preincubation of microsomes with each of the PBPs. PBP-4 was not effective per se and required preincubation with microsomes to exhibit its inhibitory effect, whereas PBP-5 remained ineffective with or without preincubation with microsomes. Further investigations revealed that the observed decrease in [(3)H]-B(a)P-DNA adduct formation was due to inhibition of isozymes of CYP450s by PBPs. Overall, results suggest that polymeric black tea polyphenol fractions retain one of the chemopreventive effects exhibited by the monomeric green tea polyphenol EGCG in vitro.  相似文献   

11.
为研究超高压处理对提高绿茶汁品质的影响,分别以料液比为1︰15和1︰50的绿茶水为原材料,采用常温常压振摇（冷提）、水浴间隔振摇（热提）和超高压（100、300和500 MPa）3种处理方法提取绿茶汁,比较其品质化学成分,分析表明：以相同料液比比较,超高压提取的绿茶汁中游离氨基酸含量均高于冷提和热提,水溶性糖含量低于冷提和热提,茶多酚得率高于冷提。色差分析表明,超高压提取的绿茶汁黄绿色度比冷提和热提的更深。超高压提取对残留的多酚氧化酶和过氧化物酶活性均具有不同程度的钝化作用。  相似文献   

12.
The purpose of this study was to investigate the distinct roles of advanced glycation end products (AGEs) on insulin-mediated glucose disposal in 3T3-L1 adipocytes and C2C12 skeletal muscle cells. AGE-modified proteins, namely, GO-AGEs, were prepared by incubating bovine serum albumin (BSA) with glyoxal (GO) for 7 days. Glucose utilization rates and the expression of insulin signaling-associated proteins, including Akt, insulin receptor substrate-1, and glucose transporter 4, were determined. GO-AGEs caused insulin resistance (IR) by suppressing insulin-stimulated glucose uptake both in 3T3-L1 adipocytes and C2C12 muscle cells. Interestingly, an unexpected finding was that insulin-stimulated glucose transport in adipocytes was affected by GO-AGEs in a biphasic manner, with an initial steep increase (168%) during the first 8 h of incubation followed by a significantly impaired uptake after extended culture times (24-48 h, p < 0.05). Treatment with GO-AGEs for 24 h markedly accelerated lipid droplet formation compared to the BSA control; however, it was blocked by incubation with an anti-RAGE antibody. Our study suggests that GO-AGEs induce an early dramatic elevation of glucose transport in adipocytes that may be related to the activation of insulin signaling; however, subsequent IR may result from increased oxidative stress and proinflammatory TNF-α production.  相似文献   

13.
Flavonoid consumption via tea drinking has been attributed a number of potential health benefits including cancer prevention, anti-inflammatory action, and cardioprotectant activity. Although the predominant flavonoids in fresh leaf and green tea are known to be flavan-3-ols and flavan-3-O-gallates ("the catechins"), the biochemical effects of tea polyphenol consumption on living systems are generally poorly understood. Metabonomic methods utilizing (1)H NMR spectroscopy of biofluids and principal component analysis (PCA) have been applied to investigate the bioavailability and metabolic responses of rats to a single dose of 22 mg of epicatechin (EC) dissolved in water. Urine samples were collected twice daily (0-8 and 8-24 h) from male Sprague-Dawley rats (n = 10) prior to dosing and for 2 days after dosing. A series of subtle urinary biochemical effects were evident from the (1)H NMR spectra showing that EC was both bioavailable and biochemically active. The identifiable biochemical effects associated with EC dosing included decreased urinary concentrations of taurine, citrate, dimethylamine, and 2-oxoglutarate. These effects were predominately seen within the first 8 h after dosing. EC metabolites were also observed in the urine during this time period. PCA of later time points after dosing (24-32 and 32-48 h) showed that the effects of EC were reversible. This is the first in vivo study demonstrating the overall endogenous metabolic effects of EC consumption and shows the bioavailability of EC via metabolic effects and excretion of EC metabolites.  相似文献   

14.
The effects of a red wine polyphenolic extract (RWPE), ethanol, or both combined were evaluated in insulin resistant rats. Rats were fed for 6 weeks with fructose (60%)-enriched food and force-fed with (a) water only (F group), (b) aqueous solution of RWPE (100 mg/kg, FP group), (c) 10% (v/v) mixture of ethanol and water (FE group), or (d) solution containing the same amount of the RWPE and ethanol (FPE group). Animals fed a standard chow (C group) were used for comparison purpose. After 6 weeks, blood pressure was higher in F (130.0 x b1 1.7 mm Hg) than in C animals (109.6 x b1 0.9 mm Hg) and similar to the C group in all other fructose-fed treatment groups. Relative heart weight was higher in F (3.10 x b1 0.05) than in C (2.78 x b1 0.07) and significantly lower in FP (2.92 x b1 0.04) and FPE (2.87 x b1 0.08 mg/g) than in F animals. Left ventricle and aorta productions of reactive oxygen species (O2*-) were higher in F than in C groups and lowered by the RWPE but not by the ethanol treatment. Ethanol but not the RWPE treatment reduced the degree of insulin resistance in the fructose-fed rats. In summary, our study showed that polyphenols are able to prevent cardiac hypertrophy and production of reactive oxygen species in the insulin resistant fructose-fed rat.  相似文献   

15.
Tea, Camellia sinensis (L.) O. Kuntze (Theaceae) is cultivated in Argentina in the northeastern region (provinces of Misiones and Corrientes), between 26 degrees and 28 degrees south latitude, the southernmost area of the world where tea is cultivated. The objective of this work was to determine the total polyphenol content and the in vitro antioxidant capacity of green and black tea cultivated and industrialized in Argentina. Twelve samples of eight brands were analyzed. The total polyphenol content was determined according to the International Organization for Standardization method (ISO) 14502-1 for the determination of substances characteristic of green and black tea. The antioxidant capacity was determined by the ferric thiocyanate method (FTC) and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging assay. Green tea showed a higher polyphenol content than black tea. The total polyphenol concentration in green tea was found to vary from 21.02 +/- 1.54 to 14.32 +/- 0.45% of gallic acid equivalents (GAE), whereas in black tea, the polyphenol content ranged from 17.62 +/- 0.42 to 8.42 +/- 0.55% of GAE (P < 0.05). A similar profile was observed for the antioxidant capacity determined by both methods. The antioxidant activities were well correlated with the total polyphenol content (r (2) = 0.9935 for the ferric thiocyanate method and r (2) = 0.9141 for the 1,1-diphenyl-2-picrylhydrazyl free-radical scavenging assay). This is the first systematic screening for the quantification of polyphenols and antioxidant activity in tea commercialized in Argentine markets. The results obtained herein allow one to conclude that Argentine tea is of very good quality when compared to teas from other sources.  相似文献   

16.
The four major commercial teas, oolong, black, pu-erh, and green teas, have been manufactured in southeast Asia. In this study, we evaluated the growth suppressive and hypolipidemic effect of these four different tea leaves by oral feeding to male Sprague-Dawley rats for 30 weeks. The results showed that the suppression of body weights of tea leaves-fed groups were in the order: oolong tea > pu-erh tea > black tea > green tea. Pu-erh tea and oolong tea could lower the levels of triglyceride more significantly than that of green tea and black tea, but pu-erh tea and green tea were more efficient than oolong tea and black tea in lowering the level of total cholesterol. In lipoprotein, 4% pu-erh tea could increase the level of HDL-C and decrease the level of LDL-C, but other teas simply decrease the levels of both. The activity of antioxidant enzyme SOD is increased in all tea-fed groups as compared to the basal diet-fed group. Finally, relative weight ratios of liver to epididylmal adipose tissue were lower in feeding oolong tea and pu-erh tea groups. On the basis of these findings, it seemed that the fully fermented pu-erh and black tea leaves and partially fermented oolong tea leaves were more effective on their growth suppressive and hypolipidemic effects as compared to the nonfermented green tea leaves.  相似文献   

17.
Protein oxidation and glycation are posttranslational modifications that are implicated in the pathological development of many age-related disease processes. This study investigated the effects of green tea extract, and a green tea tannin mixture and its components, on protein damage induced by 2,2'-azobis(2-amidinopropane) dihydrochloride (a free radical generator) and glucose in in vitro assay systems. We found that green tea extract can effectively protect against protein damage, and showed that its action is mainly due to tannin. In addition, it was shown that the chemical structures of tannin components are also involved in this activity, suggesting that the presence of the gallate group at the 3 position plays the most important role in the protective activity against protein oxidation and glycation, and that there is also a contribution by the hydroxyl group at the 5' position in the B ring and the sterical structure. These findings demonstrate the mechanisms of the usefulness of green tea in protein oxidation- and glycation-associated diseases.  相似文献   

18.
The antioxidant and antitumor activities (in vitro) of superfine regular and Se-enriched green tea particles with different sizes (3.52 microm and 220 nm) were investigated in this paper. The vitamin C and tea polyphenol contents of green tea in different sizes were significantly different, and amino acid and chlorophyll just changed a little. The antioxidant activity of green tea particles was evaluated by DPPH radical scavenging and linoleic acid peroxidation inhibition methods, and the antitumor activity was evaluated by antiproliferation assay on HepG2, A549, and MGC803 cells. The results indicated that enrichment of selenium endowed green tea with higher antioxidant activity and antitumor activity on HepG2 and A549 cells but not on MGC803 cells. The DPPH radical scavenging rates of regular and Se-enriched green tea of 220 nm (67.87% and 69.49%, respectively) were significantly greater than that of 3.52 microm, but the inhibition of linoleic acid peroxidation for green tea of 220 nm was lower. The inhibitory rates of green tea of 220 nm on HepG2, A549, and MGC803 cells achieved 77.35%, 80.76%, and 87.54% for regular green tea, and 82.51%, 88.09%, and 74.48% for Se-enriched green tea at the dose of 100 microg mL (-1), values that were all significantly higher compared to that of 3.52 microm.  相似文献   

19.
In this study, we evaluated the effect of a highly methoxylated apple pectin (HMAP) on cardiometabolic risk factors in Zucker fatty rats. beta-Glucan, a fiber known for its hypocholesterolemic properties, also was used. The rats fed both fiber-enriched diets exhibited a reduction in body weight and in total cholesterol and triglycerides when compared to the Zucker fatty rats fed the standard diet. The effect on the lipid profile was more remarkable in the HMAP group. A decrease in blood glucose was only noticed in this group. Moreover, a decrease in plasma insulin, HOMA-IR, and HOMA-beta was noticed in the fiber groups, and in particular in the HMAP group, these variables being similar to the lean rats. Blood pressure and endothelial function were similar in all the Zucker fatty rats. These results warrant evaluation in humans to determine if HMAP could be used as a functional ingredient to reduce lipid profile, insulin resistance, and other cardiometabolic risk factors.  相似文献   

20.
Green tea, coffee, and gomchui (Ligularia fischeri) tea, which are rich in polyphenols, may exhibit antiobesity effects by inhibiting pancreatic lipase. However, the bioavailability of some polyphenols is poor due to either degradation or absorption difficulties in the gastrointestinal tract, thus making their beneficial effects doubtful. This study was conducted to evaluate the inhibitory effect of three beverages on lipolysis and the contribution of their major polyphenols during simulated digestion. During simulated digestion, gomchui tea was the most potent at inhibiting gastrointestinal lipolysis, whereas green tea was the least potent. The strongest lipase inhibitor among purified major polyphenols was a green tea polyphenol, (-)-epigallocatechin gallate (EGCG, IC(50) = 1.8 ± 0.57 μM), followed by di-O-caffeoylquinic acid isomers (DCQA, IC(50) from 12.7 ± 4.5 to 40.4 ± 2.3 μM), which are gomchui tea polyphenols. However, the stability of DCQA was greater than that of EGCG when subjected to simulated digestion. Taken together, gomchui tea, which has DCQA as the major polyphenol, showed stronger lipolysis inhibitory activity during simulated digestion compared to both green tea and coffee.  相似文献   

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