ラットにおける食餌性脂質酸化に対する茶カテキンの影響（原文標題は英語）

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.

Antioxidative effect of added tea catechins on susceptibility of cooked red meat, poultry and fish patties to lipid oxidation

Dietary tea catechins and iron-induced lipid oxidation in chicken meat, liver and heart

Effects of added tea catechins on colour stability and lipid oxidation in minced beef patties held under aerobic and modified atmospheric packaging conditions

Tea catechins, rich in (-)-epigallocatechin gallate and (-)-epicatechin gallate, or heat-treated tea catechins in which about 50% of the (-)-epigallocatechin gallate and (-)-epicatechin gallate in tea catechins was epimerized to (-)-gallocatechin gallate and (-)-catechin gallate, were fed to rats at 1% level for 23 d. Visceral fat deposition and the concentration of hepatic triacylglycerol were significantly lower in the tea catechin and heat-treated tea catechin groups than in the control group. The activities of fatty acid synthase and the malic enzyme in the liver cytosol were significantly lower in the two catechin groups than in the control group. In contrast, the activities of carnitine palmitoyltransferase and acyl-CoA oxidase in the liver homogenate were not significantly different among the three groups. These results suggest that the reduction in activities of enzymes related to hepatic fatty acid synthesis by the feeding of tea catechins or heat-treated tea catechins can cause reductions of hepatic triacylglycerol and possibly of visceral fat deposition.

The body fat reducing effect of tea catechins was previously confirmed in humans. The effects of tea catechins for reducing body fat were thus studied as basis for actual application. Three experiments on healthy male adults (n=82) were conducted to determine the effects of long-term tea catechins administration on body fat and biochemical blood parameters. First experiment: tea catechins were given as oolong tea-like beverage for 12 weeks. In 600 and 900 mg groups, visceral fat was significantly loss than in the control (600 mg group p=0.0317, 900 mg group p=0.0098). The effects were more pronounced at greater of tea catechins administration. No significant changes in biochemical blood parameters including fat-soluble vitamins were detected. Second experiment : oolong tea-like beverage containing tea catechins at nearly same amounts on in the 600 mg group was given for 20 weeks. Abdominal fat, including visceral fat, was significantly loss than in the control (total fat area p<0.0001, visceral fat area p=0.0004, subcutaneous fat area p=0.0001). Plasma PAI-1 was also significantly decreased (p=0.0080). Third experiment : green tea-like (GT group) and oolong tea-like (OT group) beverages containing approximately 540 mg tea catechins were given for 12 weeks. In the two groups, visceral fat was significantly loss than in the control (GT group p=0.0284, OT group p=0.0095) and the effects of two beverages were similar. Long-term tea catechins administration at 500 to 600 mg/day in humans would thus appear to reduce body fat without influencing fat-soluble vitamins, of which the absorption may be inhibited, and various serum and plasma indices regardless of the kind of beverages.

Background In vivo studies using rodents have shown that green tea extract (GT) and catechins isolated from green tea can induce a variety of health effects, including antiobesity, hypoglycemic and hypolipidemic activities. However, we and others observed that serum cholesterol levels were increased by GT and tea catechins in rats and mice [1]. In this study, we examined whether dietary GT affects the expression of genes involved in cholesterol synthesis. Materials and methods Catechin-rich (30% catechin) GT was used for the in vivo studies. Male Sprague-Dawley rats (average weight 237.7 g) were divided into six groups. The first group was fed a normal diet (ND, 10% calories from fat); the second group a high-fat diet (HFD, 40% calories from fat); the third group a ND containing 1% GT (ND + 1% GT); the fourth group a HFD + 1% GT; the fifth group a ND + 3% GT; and the sixth group a HFD + 3% GT. After 4 weeks of feeding, rats were euthanized by whole blood collection under anesthesia. Serum metabolites were determined using a dry chemistry analyzer. Total RNA samples extracted from the liver were used for microarray and quantitative real-time PCR (qPCR) analyses. Hepatic lipids were extracted with chloroform-methanol 2:1, and liver triglyceride (TG) and cholesterol (Cho) levels were determined. Results As reported previously, GT increased the serum levels of total cholesterol (T-Cho) and high-density lipoprotein cholesterol (HDL-Cho) in a concentration-dependent manner in both ND- and HFD-fed rats. Conversely, GT lowered hepatic TG and T-cho levels. Microarray analysis data suggested that GT increased more than two-fold the mRNA expression of nine hepatic genes involved in cholesterol synthesis out of 21 analyzed in ND-fed rats. qPCR analysis revealed that GT significantly increased the mRNA levels of six genes involved in cholesterol synthesis in ND-fed rats. Similar but smaller effects of GT also were observed in HFD-fed rats. Conclusions The results suggested that GT increased serum cholesterol levels, at least in part, through the increased expression of genes in the cholesterol synthetic pathways in the liver. GT also increased the mRNA levels of Srebf2 and Insig1, which are positively regulated by SREBP2. Therefore, dietary GT may increase expression of these genes by SREBP2 activation.

Much attention has been paid to the beneficial health effect of tea catechins as one of the effective strategies to prevent obesity. The current study was carried out to investigate the role of tea catechins on the utilization of dietary energy sources in rats. The addition of 1% (w/w) tea catechins, mostly in gallate forms, to the diet brought about significant reductions in body weight gains and abdominal adipose tissue weights after 4-wk feeding periods compared to the control. A 2-d output of feces collected at the third week of feeding was significantly increased by a tea catechin diet (average dry weight+/-SD of 7.2+/-1.5 g) over that with a control diet (3.8+/-0.4 g). Only 0.1% of ingested starch appeared in the feces of rats fed the control diet, whereas 4.8% was excreted in the feces of the tea catechin group. Moreover, both apparent digestibility values for lipid and protein in the rats fed tea catechins were also lower than those of the control, suggesting that tea catechins increased the fecal excretion of these energy nutrients. Of the gross energy that the rats consumed from their respective diets during the fecal collection period, 1.6% (for control diet) and 5.8% (for tea catechin diet) were estimated to be excreted in feces. The energy loss originating from carbohydrate should contribute to the overall amount of energy in the feces, followed by protein. Intake of tea catechins suppressed the intestinal absorption of energy nutrients via the inhibition of digestive enzymes, which may at least partially influence the body fat reduction by tea catechins.

Addition of tea catechins and vitamin C on sensory evaluation, colour and lipid stability during chilled storage in cooked or raw beef and chicken patties

Green tea catechins (TC) have anti-obesity effects on atherosclerosis-susceptible mice fed atherogenic diet, but the antioxidant effect of the catechins at these conditions is not studied. Our aim is to show that green tea catechins have a favorable effect on plasma and organs lipid peroxidation parameters. For the purpose we have fed atherosclerosis-susceptible mice HF (30 %) diet containing TC (0.5 %). We have measured body weight, food intake, ferric-reducing ability of plasma (FRAP), total cholesterol and α-tocopherol concentrations in plasma, and lipid hydroperoxides concentrations in liver and small intestine, and compared them with these in control group fed HF diet. Also we have measured ECG and EGCG concentrations in plasma, liver, and small intestine of the mice fed TC. Our results show that green tea catechins′ feeding reduces the body weight without affecting the food intake. TC group FRAP values are significantly different from these in the control group at all investigated periods. α-Tocopherol plasma concentrations in TC group have greater values than these in the control group. TC group liver and small intestine lipid hydroperoxides concentrations are lower than these in HF group. In conclusion, our results show that green tea catechins′ feeding leads to catechins accumulation in plasma, liver, and small intestine which causes anti-lipid peroxidation effects in atherosclerosis-susceptible mice.

Tea Catechins with a Galloyl Moiety Suppress Postprandial Hypertriacylglycerolemia by Delaying Lymphatic Transport of Dietary Fat in Rats

The comparative anti-oxidative effects of added tea catechins (TC) and α-tocopherol to raw minced red meat (beef and pork), poultry (chicken, duck and ostrich) and fish (whiting and mackerel) muscle on susceptibility to lipid oxidation were investigated during 10 days of refrigerated (4 °C) display. Fresh meats, poultry and fish, purchased from a local market, were trimmed to remove bones, skin and surface fat and minced through a 4 mm plate. The minced muscle of each species was treated with either the addition of 300 mg TC kg–1 minced muscle (TC300) or 300 mg α-tocopherol kg–1 minced muscle (VE300). Minced muscle without any additives served as control (C). Oxidative stability (TBARS) was measured at 3-day intervals. Total lipids, fatty acid composition, total iron and haem iron from minced muscle for each species were also analysed. The susceptibility of untreated minced muscle to lipid oxidation was in the decreasing order: mackerel &amp;gt; beef &amp;gt; duck &amp;gt; ostrich &amp;gt; pork ≥ chicken &amp;gt; whiting. This may be because of the different content of total fat, iron and fatty acid composition between species. The TC300 significantly (P &amp;lt; 0.05) reduced lipid oxidation compared with controls for all seven species as shown by lower TBARS values. The anti-oxidant potential of TC was two to fourfold greater than that of α-tocopherol at the same concentration and this potential was species dependent. The VE300 showed limited capacity in inhibiting lipid oxidation for pork, chicken, duck and whiting. The results obtained show that TCs are powerful natural antioxidants when used in minced muscle food.

The properties of plants with food preservation potential are well known since the antiquity. In recent years,the use of herbs and spices to improve the sensory characteristics and to extend the shelf-life of foods has been growing.Antioxidant effect of adding rosemary extract (RE), sage extract (SE), oregano extract (OE), ginger extract (GE), cloveextract (CE), tea catechins (TC) compared to BHA/BHT, on lipid oxidation and beef burger quality were investigated.The proximate composition, TBARS values, antioxidant activity (AOA%), colour parameters (Hunter L*, a*, b* values,redness index and total colour difference), and sensory attributes of the beef burgers contained RE, SE, OE, GE, CE, TCand BHR/BHT during refrigerated storage at 4±􀀛°C for 􀀛5 days were determined and calculated. Significant reductionin TBARS values and colour changes for all treated beef burgers was observed during storage compared to control.TBARS values were significantly low in TC, followed by RE, CE, BHA/BHT, OE, SE and GE beef burgers.Antioxidant activity of the tested beef burgers was in the order TC > RE > CE > BHA/BHT > OE > SE > GE, sensoryscores were in agreement with these results. So, TC, RE and CE prevent lipid oxidation in beef burgers, and could beused in place of synthetic antioxidants, which have proved for their negative health implications.

Obesity is a risk factor for the development of chronic health problems, including heart disease, liver disease, diabetes, cancer, and arthritis. Tea catechins are a group of polyphenolic compounds present in the unfermented dried leaves of the tea plant (Camellia sinensis). The results of randomized controlled intervention trials suggest that daily ingestion of tea catechins (&gt;540 mg/day) reduces body weight and body fat, and the results of in vivo studies in animal and human suggest that continued ingestion of tea catechins increases energy expenditure and lipid oxidation in liver and muscle. Thus, tea catechins likely reduce body fat by promoting the use of lipids as an energy source and therefore may be a useful means of treating obesity.

Tea catechins, a class of flavonoids, are suggested to have biological effects, possibly mediated through their antioxidative properties. Recent data indicated that tea catechins suppressed proliferative changes in glomeruli and inhibited the development of glomerulosclerosis in partially nephrectomized rats. We thus sought to determine whether tea catechins may protect against renal dysfunction in streptozotocin-induced diabetic rats. Four groups of male Sprague-Dawley rats (n=11-15 per group), with and without streptozotocin-induced diabetes, were treated with and without catechins (5 mg/day) administered in the drinking water for 12 weeks. At the end of the treatment period, 24-hour urinary albumin excretion rate (AER), serum lipid peroxides as thiobarbituric acid reactive substrates (TBARS) and blood pressure were measured. Renal glomerular volume and interstitial fibrosis were assessed morphologically. Albuminuria developed progressively in untreated diabetic rats, resulting in a mean AER of 559+/-124 (mean+/-SE) versus 63+/-7 microg/day/100 g body weight in non-diabetic rats at 12 weeks (P<0.001). Catechin treatment significantly reduced AER to 287+/-56 microg/day/100 g body weight in diabetic rats (P=0.017 versus untreated diabetic rats). Increased interstitial fibrosis in the kidney, observed in untreated diabetic rats, was completely normalized with catechin treatment. Serum levels of TBARS and blood pressure were comparable among the four groups. In conclusion, administration of tea catechin retards the progression of functional and morphological changes in the kidney of streptozotocin-induced diabetic rats.