Effects Of Tea Catechins Research Articles

Effects of tea catechins on uncoupling proteins mRNA expressions in rat brown adipose tissues

Effects of tea catechins on uncoupling proteins mRNA expressions in rat brown adipose tissues

Identification of a PKCε-dependent regulation of myocardial contraction by epicatechin-3-gallate

In this study, the effects of tea catechins and tea theaflavins on myocardial contraction were examined in isolated rat hearts using a Langendorff-perfusion system. We found that both tea catechins and theaflavins had positive inotropic effects on the myocardium. Of the tested chemicals, epicatechin-3-gallate (ECG) and theaflavin-3,3'-digallate (TF(4)) appear to be the most effective tea catechin and theaflavin, respectively. Further studies of ECG-induced positive inotropy revealed the following insights. First, unlike digitalis drugs, ECG had no effect on intracellular Ca(2+) level in cultured adult cardiac myocytes. Second, it activated PKCepsilon, but not PKCalpha, in the isolated hearts as well as in cultured cells. Neither a phospholipase C (PLC) inhibitor (U73122) nor the antioxidant N-acetyl cysteine (NAC) affected the ECG-induced activation of PKCepsilon. Third, inhibition of PKCepsilon by either chelerythrine chloride (CHE) or PKCepsilon translocation inhibitor peptide (TIP) caused a partial reduction of ECG-induced increases in myocardial contraction. Moreover, NAC was also effective in reducing the effects of ECG on myocardial contraction. Finally, pretreatment of the heart with both CHE and NAC completely abolished ECG-induced inotropic effects on the heart. Together, these findings indicate that ECG can regulate myocardial contractility via a novel PKCepsilon-dependent signaling pathway.

Effect of tea catechins on the structure of lipid membrane and beta-ray induced lipid peroxidation

Inhibiting effect of four tea catechins, (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), on the lipid peroxidation induced by β-ray in tritiated water was examined using a spin probe method. 16-Doxylstearic acid (16NS) was incorporated into the liposome prepared from egg yolk phosphatidylcholine and the rate of the decrease of ESR intensity of 16NS was used as a measure of the inhibiting effect. In the low concentration region below 10−5M, catechins showed their inhibitions on the lipid peroxidation according to the order of ECG>EGCG>EC>EGC. This result was explained by a model that the initiator of the peroxidation is the hydroxyl radical (·OH) and the catechins adsorbed on the lipid membrane surface acting as scavengers of ·OH. In the high concentration range, however, the effect was diverse and it decreased with the increase of it in the case of EGCG. EGCG in this range was considered to enter into the interior of the membrane and break the structure, which causes the decrease of 16NS. Observation with transmission electron microscope (TEM) revealed that the size of the liposome became larger with the increasing concentration of EGCG and finally it was broken into fragments, showing that EGCG broadened the area of the liposome as expected from the result of ESR.

Effects of tea catechins on lipolysis and UCP1 mRNA expression in rat adipose tissues

Effects of tea catechins on lipolysis and UCP1 mRNA expression in rat adipose tissues

Inhibitory Effects of Tea Catechins on Lipid Peroxidation Induced by Rose Bengal and Blue Light Exposure in Porcine Retinal Homogenate

Inhibitory Effects of Tea Catechins on Lipid Peroxidation Induced by Rose Bengal and Blue Light Exposure in Porcine Retinal Homogenate

Effect of tea catechins on mitochondrial DNA 4977-bp deletions in human leucocytes

The catechins in green tea have antioxidative and antimutagenic effects. We examined the effect of green tea enriched with catechins on the presence of mitochondrial DNA (mtDNA) with a common 4977-bp deletion mutation (mtDNA 4977) in human leucocytes. Ten healthy females [aged 20.80 ± 1.03 years] drank 350 ml of catechin-rich tea daily after supper for 5 weeks. Blood samples were collected twice before, and twice after 5 weeks of consuming the tea. Deletions in mtDNA were analyzed using the nested polymerase chain reaction (PCR). We identified a common mtDNA 4977 deletion in nine participants before drinking the tea. However, this mtDNA 4977 deletion was not evident in leucocytes from most of the participants 5 weeks after drinking the tea. Catechins found in tea might contribute to the maintenance of health status by reducing damage to mtDNA and by maintaining the capacity of mtDNA for oxidative phosphorylation.

Effect of tea catechins on intracellular lipolysis in 3T3-L1 cells.

Effect of tea catechins on intracellular lipolysis in 3T3-L1 cells.

Effects of Tea Catechins on Fecal Odor and Odorous Compounds in Cats

Effects of Tea Catechins on Fecal Odor and Odorous Compounds in Cats

Effect of tea catechins on the change of glutathione levels caused by Pb(++) in PC12 cells.

Our previous research showed that tea catechins could significantly increase the viability of lead-exposed PC12 cells. Whereas the cellular thiol status is known to be responsible for protecting against lead-induced toxicity, whether the role of tea catechins on lead-induced PC12 cell toxicity is related to the metabolism of intracellular thiol compounds remained vague. In the present study, it was found that Pb(2+) significantly decreased reduced glutathione (GSH)/oxidative glutathione (GSSG) and protein sulfhydryl groups (PSH)/glutathione-protein mixed disulfide (GSSP) ratios as well as glutathione reductase activities in a concentration-dependent manner. Both (-)-epicatechin and (-)-epicatechin gallate (ECG) supplementation resulted in an increased GSH/GSSG ratio and glutathione reductase activities. The galloylated catechins (ECG or (-)-epigallocatechin gallate) treatment significantly decreased the GSSP levels and increased the intracellular PSH/GSSP ratio in lead-exposed PC12 cells. To our surprise, as compared with the group treated by lead acetate, 100 microM EGC treatment following lead exposure significantly decreased GSH/GSSG and PSH/GSSP ratios, as well as glutathione reductase activities. The results suggested that the effect of tea catechins on the intracellular thiols status in PC12 cells was different, which may be related to their chemical structures and/or regulation of special gene expression properties.

Effect of tea catechins on lipogenesis in adipocytes

Effect of tea catechins on lipogenesis in adipocytes

Effects of tea catechins on lipid metabolism and body fat accumulation

Long-term feeding of tea catechins suppressed body fat accumulation in high-fat diet-induced obesity in mice, and that their effects might be attributed, at least in part, to the activation of hepatic lipid metabolism. Consecutive intake of tea catechins (588 mg/day) reduced body fat, especially abdominal fat in humans. These results demonstrate that intake of tea catechins is beneficial for body fat accumulation.

Protective Effect of Tea Catechins on the DNA Scission Induced in Tritiated Water

ABSTRACTThe protecting effect of (−)-epicatechin (EC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCg) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) on the DNA strand scission induced in tritiated water was analyzed. The scission with the hydroxyl radical produced by the decomposition of water molecules was decreased by the addition of above reagents. Protective effect of EGCg, EC and DMPO was dependent on their concentrations, but that of ECg and EGC was independent. Therefore, it was considered that certain amounts of ECg, EGC molecules might locate around DNA molecules, interacting with DNA.

Effect of tea catechins on cellular lipid peroxidation and cytotoxicity in HepG2 cells.

Tea catechins inhibited TBARS accumulation in HepG2 cells, the order of effectiveness being (-)-epigallocatechin gallate (EGCG) > (-)-epigallocatechin (EGC) > or = (-)-epicatechin gallate (ECG) > (-)-epicatechin (EC). EGCG and EGC protected the depletion of alpha-tocopherol in the cells, and the glutathione content was enhanced by all four catechins. Moreover, all four catechins suppressed the formation of glutathione disulfide and the activation of glutathione peroxidase induced by tert-butylated hydroperoxide.

A comparative study of tea catechins and α-tocopherol as antioxidants in cooked beef and chicken meat

The effects of tea catechins (TC) on improving oxidative stability of cooked chicken meat and beef compared with those of α-tocopherol (VE) were investigated. Fresh meats, purchased from a local market, were trimmed to remove skin and visible fat and minced through a 4 mm plate. The ground meat from each species was treated with 1% NaCl (S), 300 mg TC kg–1 minced meat (TC300), 1% NaCl plus 300 mg TC kg–1 minced meat (TCS), 300 mg VE kg–1 minced meat (VE300) and 1% NaCl plus 300 mg VE kg–1 minced meat (VES), respectively. Patties (50 g), prepared from treated and untreated minced meat, were cooked until the core temperature reached 75 °C, cooled to room temperature and held in a refrigerated (4 °C) illuminated (616 lux) display cabinet for 10 days. Oxidative stability (TBARS) was measured on days 1, 3, 6 and 10. The susceptibility of cooked meat to lipid oxidation was species dependent. Chicken meat was more susceptible to oxidative deterioration than beef. NaCl promoted lipid oxidation in cooked chicken meat and beef in this study. The lipid oxidation in cooked chicken meat was more effectively controlled by TC, compared to cooked beef. Both VE and TC significantly (p<0.05) improved oxidative stability for cooked beef and chicken meat. However, the inhibition of lipid oxidation resulting from TC was more effective than that for VE. Both VE and TC inhibited the pro-oxidant effect of NaCl, but the synergistic action was only found between salt and TC.

マウスにおける食事性肥満に対する茶カテキン類の効果（原標題は英語）

マウスにおける食事性肥満に対する茶カテキン類の効果（原標題は英語）

Differences in Antioxidative Efficiency of Catechins in Various Metal-Induced Lipid Peroxidations in Cultured Hepatocytes.

The effects of tea catechins, including (‐)-epicatechin (EC), (‐)-epigallocatechin (EGC), (‐)-epicatechingallate (ECg) or (‐)-epigallocatechingallate (EGCg) on the lipid peroxidation induced by either ferrous (Fe), copper (Cu) or vanadium (V ) ions were examined in normal and α-linolenic acid-loaded (LNA-loaded) cultured rat hepatocytes. The order of antioxidative activity was almost similar and ranked as follows: EGCg > ECg > EGC > EC against the three metal-induced lipid peroxidations in both groups of cultured hepatocytes. However, each catechin displayed a marked variation in its antioxidative potency depending on the added metal ion species, whereas dibutyl hydroxy toluene (BHT), a typical lipid radical scavenger, exhibited a similar antioxidative potency with all metal ions. The half inhibition concentration (IC50) values of the catechins for Fe ion-induced lipid peroxidation were 2 to 3 times and 5 to 14 times higher than those for V ion and Cu ion, respectively in normal hepatocytes. Only in LNA-loaded hepatocytes, was EC antioxidative at 20 µM Fe concentration but it became prooxidative above 50 µM Fe concentration. Catechins such as (+)-catechin, (+)-epicatechin and (±)-catechin also acted as prooxidants at high Fe concentrations in LNA-loaded hepatocytes. The antioxidative efficiency of EGC, ECg or EGCg decreased with the increase in Fe ion concentrations from 20 µM up to 500 µM in LNA-loaded hepatocytes. These findings suggest that the metal-chelating property of catechins may play a major role in determining antioxidative activity in cultured hepatocytes.

Effects of tea catechins on the ERE-regulated estrogenic activity.

Tea catechins exert many biological effects, including anticancer and antibacterial activities. Also, it is reported that some plant flavonoids exhibit estrogenic activity. In this study, we investigated estrogenic or antiestrogenic activities of catechins in HeLa cells transiently transfected with an estrogen response element (ERE)-regulated luciferase reporter and an estrogen receptor (ER) alpha or ERbeta expression vector. Catechins alone did not induce luciferase (luc) activity in either of the ERs. Addition of 17beta-estradiol (E2) plus epicatechin gallate (ECG) or epigallocatechin gallate (EGCG) at 5 x 10(-6) M resulted in significant decreases in the ERalpha-mediated luc activity compared with that of E2 alone. On the contrary, lower concentrations significantly increased the E2-induced luc activity. Similar effects were observed with tamoxifen. The ERbeta-mediated estrogenic activities were stimulated by catechins. In conclusion, some catechins, particularly EGCG, were antiestrogenic for ERalpha at higher doses, and co-estrogenic for ERalpha at lower doses and for ERbeta. The lower doses were found in human plasma after tea-drinking. In addition, some catechins may be antiendocrine disruptors because they suppressed bisphenol A-induced luc activities.

Scavenging effect of tea catechins and their epimers on superoxide anion radicals generated by a hypoxanthine and xanthine oxidase system

Scavenging effect of tea catechins and their epimers on superoxide anion radicals generated by a hypoxanthine and xanthine oxidase system

Effects of tea catechin and specific antibody of influenza viruses

Effects of tea catechin and specific antibody of influenza viruses

Effect of green tea catechins on plasma cholesterol level in cholesterol-fed rats.

Effects of tea catechins (tannins) on lipid metabolism were studied in male weanling rats fed a 25% casein diet containing 15% lard and 1% cholesterol for 28 days. Crude tea catechins prepared from green tea powder were supplemented at a 1% and 2% of the lard-cholesterol diet. The addition of 2% tea catechins slightly depressed growth but at the 1% level was without effect. Tea catechins decreased plasma total cholesterol, cholesterol ester, total cholesterol--HDL-cholesterol (VIDL-+LDL-cholesterol) and atherogenic index (VLDL-+LDL-cholesterol/HDL-cholesterol). Hematocrit and plasma glucose were not altered by the addition of tea catechins. The liver weight, liver total lipids and cholesterol concentrations in rats fed the lard-cholesterol diet increased more than in the control rats, but the addition of tea catechins to the lard-cholesterol diet decreased those parameters. Tea catechin supplementation increased fecal excretion of total lipids and cholesterol. The results demonstrate that tea catechins exert a hypocholesterolemic effect in cholesterol-fed rats.