A green tea extract high in catechins reduces body fat and cardiovascular risks in humans

Objective: The body fat reducing effect and reduction of risks for cardiovascular disease by a green tea extract (GTE) high in catechins was investigated in humans with typical lifestyles. Research Methods and Procedures: Japanese women and men with visceral fat‐type obesity were recruited for the trial. After a 2‐week diet run‐in period, a 12‐week double‐blind parallel multicenter trial was performed, in which the subjects ingested green tea containing 583 mg of catechins (catechin group) or 96 mg of catechins (control group) per day. Randomization was stratified by gender and body mass index at each medical institution. The subjects were instructed to maintain their usual dietary intake and normal physical activity. Results: Data were analyzed using per‐protocol samples of 240 subjects (catechin group; n = 123, control group; n = 117). Decreases in body weight, body mass index, body fat ratio, body fat mass, waist circumference, hip circumference, visceral fat area, and subcutaneous fat area were found to be greater in the catechin group than in the control group. A greater decrease in systolic blood pressure (SBP) was found in the catechin group compared with the control group for subjects whose initial SBP was 130 mm Hg or higher. Low‐density lipoprotein (LDL) cholesterol was also decreased to a greater extent in the catechin group. No adverse effect was found. Discussion: The continuous ingestion of a GTE high in catechins led to a reduction in body fat, SBP, and LDL cholesterol, suggesting that the ingestion of such an extract contributes to a decrease in obesity and cardiovascular disease risks.     

Green tea as inhibitor of the intestinal absorption of lipids: potential mechanism for its lipid-lowering effect

Animal and epidemiological studies suggest that green tea catechins may reduce the risk of cardiovascular diseases [e.g., coronary heart disease (CHD)]. The health benefit of green tea has been attributed to its antioxidant and anti-inflammatory properties; however, considerable evidence suggests that green tea and its catechins may reduce the risk of CHD by lowering the plasma levels of cholesterol and triglyceride. Although the mechanism underlying such effect of green tea is yet to be determined, it is evident from in vitro and in vivo studies that green tea or catechins inhibit the intestinal absorption of dietary lipids. Studies in vitro indicate that green tea catechins, particularly (-)-epigallocatechin gallate, interfere with the emulsification, digestion, and micellar solubilization of lipids, critical steps involved in the intestinal absorption of dietary fat, cholesterol, and other lipids. Based on the observations, it is likely that green tea or its catechins lower the absorption and tissue accumulation of other lipophilic organic compounds. The available information strongly suggests that green tea or its catechins may be used as safe and effective lipid-lowering therapeutic agents.     

Dietary gallate esters of tea catechins reduce deposition of visceral fat, hepatic triacylglycerol, and activities of hepatic enzymes related to fatty acid synthesis in rats

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.     

Body Fat Accumulation in Zebrafish Is Induced by a Diet Rich in Fat and Reduced by Supplementation with Green Tea Extract

Fat-rich diets not only induce obesity in humans but also make animals obese. Therefore, animals that accumulate body fat in response to a high-fat diet (especially rodents) are commonly used in obesity research. The effect of dietary fat on body fat accumulation is not fully understood in zebrafish, an excellent model of vertebrate lipid metabolism. Here, we explored the effects of dietary fat and green tea extract, which has anti-obesity properties, on body fat accumulation in zebrafish. Adult zebrafish were allocated to four diet groups and over 6 weeks were fed a high-fat diet containing basal diet plus two types of fat or a low-fat diet containing basal diet plus carbohydrate or protein. Another group of adult zebrafish was fed a high-fat diet with or without 5% green tea extract supplementation. Zebrafish fed the high-fat diets had nearly twice the body fat (visceral, subcutaneous, and total fat) volume and body fat volume ratio (body fat volume/body weight) of those fed low-fat diets. There were no differences in body fat accumulation between the two high-fat groups, nor were there any differences between the two low-fat groups. Adding green tea extract to the high-fat diet significantly suppressed body weight, body fat volume, and body fat volume ratio compared with the same diet lacking green tea extract. 3-Hydroxyacyl-coenzyme A dehydrogenase and citrate synthase activity in the liver and skeletal muscle were significantly higher in fish fed the diet supplemented with green tea extract than in those fed the unsupplemented diet. Our results suggest that a diet rich in fat, instead of protein or carbohydrate, induced body fat accumulation in zebrafish with mechanisms that might be similar to those in mammals. Consequently, zebrafish might serve as a good animal model for research into obesity induced by high-fat diets.     

The protective activity of tea catechins against experimental infection by Vibrio cholerae O1.

Tea catechins inhibited the fluid accumulation induced by cholera toxin in sealed adult mice. The catechins also reduced fluid accumulation by Vibrio cholerae O1 in ligated intestinal loops of rabbits. These findings suggest that tea catechins may possess protective activity against V. cholerae O1.     

Antiobesity effects of green tea catechins: a mechanistic review

Green tea catechins (GTC) are polyphenolic compounds present in the unfermented dried leaves of the plant, Camellia sinensis. Results from a number of randomized, controlled intervention trials have shown that consumption of GTC (270 mg to 1200 mg/day) may reduce body weight and fat. There are several proposed mechanisms whereby GTC may influence body weight and composition. The predominating hypothesis is that GTC influences sympathetic nervous system (SNS) activity, increasing energy expenditure and promoting the oxidation of fat. Caffeine, naturally present in green tea, also influences SNS activity, and may act synergistically with GTC to increase energy expenditure and fat oxidation. Other potential mechanisms include modifications in appetite, up-regulation of enzymes involved in hepatic fat oxidation, and decreased nutrient absorption. This article reviews the evidence for each of these purported mechanisms, with particular reference to studies in humans.     

Plasma and lipoprotein levels of tea catechins following repeated tea consumption

Epidemiological studies suggest that antioxidant flavonoids in tea may reduce the risk of cardiovascular disease, possibly via protection of low-density lipoproteins (LDL) against oxidation. However, the extent of absorption of tea flavonoids and their accumulation in LDL during regular consumption of tea is not clear. Therefore we investigated plasma and lipoprotein levels of catechins during tea consumption and the impact on LDL oxidizability ex vivo. Eighteen healthy adults consumed, in an incomplete balanced cross-over design, green tea, black tea, black tea with milk or water, one cup every 2 hr (eight cups/day) for three days. Blood samples were obtained in the mornings and evenings of each day. Plasma total catechin concentration was determined in all blood samples, and the distribution of catechins among lipoproteins was determined at the end of the third day (t = 60 hr). The resistance of LDL to copper-induced oxidation ex vivo was assessed before tea consumption and at t = 60 hr. Repeated tea consumption during the day rapidly increased plasma total catechin levels whereas they declined overnight when no tea was consumed. There was a gradual increase in plasma levels in the mornings (respectively, 0.08 microM vs. 0.20 microM on first and last day of black tea consumption) and evenings (respectively, 0.29 microM vs. 0.34 microM on first and last day of black tea consumption). Green tea catechins were mainly found in the protein-rich fraction of plasma (60%) and in high-density lipoproteins (23%). Although present in LDL, the concentration of catechins in LDL was not sufficient to enhance the resistance of LDL to oxidation ex vivo. Addition of milk to black tea did not affect any of the parameters measured. In conclusion, the present study shows that catechin levels in blood rapidly increase upon repeated tea consumption. The accumulation of catechins in LDL particles is not sufficient to improve the intrinsic resistance of LDL to oxidation ex vivo.     

Tea catechins enhance the mRNA expression of uncoupling protein 1 in rat brown adipose tissue

The aim of the present study was to determine whether the antiobesity effects of tea catechins (TCs) are associated with the expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT). Male Sprague–Dawley rats were fed a high-fat (HF; 35% fat) diet for 5 weeks, then divided into four groups and fed an HF, HF with 0.5% TC (HFTC), normal-fat (NF; 5% fat) or NF with 0.5% TC (NFTC) diet for 8 weeks. At the end of the experimental period, perirenal and epididymal white adipose tissues (WATs) and interscapular BAT were isolated. The NFTC group had significantly lower perirenal WAT weights than the NF group (NF: 12.7±0.53 g; NFTC: 10.2±0.43 g; P<.01), but the HF and HFTC groups did not differ significantly. TC intake had no effects on epididymal WAT weights. The NFTC and HFTC groups had significantly lower BAT weights than the NF and HF groups, respectively. The NFTC group had significantly higher UCP1 mRNA levels in BAT than the NF group (NF: 0.35±0.02; NFTC: 0.60±0.11; P<.05), but the HF and HFTC groups did not differ significantly. Thus, TC intake in the context of the NF diet reduced perirenal WAT weight and up-regulated UCP1 mRNA expression in BAT. These results suggest that the suppressive effect of TC on body fat accumulation is associated with UCP1 expression in BAT.     

Effects of intake of a mixture of thiamin, arginine, caffeine, and citric acid on adiposity in healthy subjects with high percent body fat

We assessed the effects of intake of thiamin, arginine, caffeine, and citric acid (TACC) on lipid metabolism in healthy subjects. Thirty-one subjects with high percent body fat (> or = 25.0%) were randomly assigned to a 12-wk intervention with daily intake of TACC-supplemented tea (1.1, 1240, 52, and 540 mg, respectively; n=16) or control tea (n=15). The percent body fat decreased significantly during the intervention in both groups, especially in the TACC group. A percentage decrease in triceps skinfold was significantly greater in the TACC group than in the control group. The decrease in abdominal visceral fat in obese subjects was significantly greater in the TACC group than in the control group. Serum triglyceride was significantly lower during intervention than that during the non-intervention period in the TACC group. These results suggest that TACC may be effective in reducing body fat in obese subjects.     

Effects of Catechin Enriched Green Tea on Body Composition

Obesity is a major health problem in the developed and developing world. Many “functional” foods and ingredients are advocated for their effects on body composition but few have consistent scientific support for their efficacy. However, an increasing amount of mechanistic and clinical evidence is building for green tea (GT). This experiment was therefore undertaken to study the effects of a high‐catechin GT on body composition in a moderately overweight Chinese population. In a randomized placebo‐controlled trial, 182 moderately overweight Chinese subjects, consumed either two servings of a control drink (C; 30 mg catechins, 10 mg caffeine/day), one serving of the control drink and one serving of an extra high‐catechin GT1 (458 mg catechins, 104 mg caffeine/day), two servings of a high‐catechin GT2 (468 mg catechins, 126 mg caffeine/day) or two servings of the extra high‐catechin GT3 (886 mg catechins, 198 mg caffeine/day) for 90 days. Data were collected at 0, 30, 60, and 90 days. We observed a decrease in estimated intra‐abdominal fat (IAF) area of 5.6 cm² in the GT3 group. In addition, we found decreases of 1.9 cm in waist circumference and 1.2 kg body weight in the GT3 group vs. C (P < 0.05). We also observed reductions in total body fat (GT2, 0.7 kg, P < 0.05) and body fat % (GT1, 0.6%, P < 0.05). We conclude that consumption of two servings of an extra high‐catechin GT leads to improvements in body composition and reduces abdominal fatness in moderately overweight Chinese subjects.     

Effects of black tea consumption on plasma catechins and markers of oxidative stress and inflammation in patients with coronary artery disease

We previously demonstrated that black tea consumption reverses endothelial dysfunction in patients with coronary artery disease. To investigate potential mechanisms of this effect, we examined plasma catechins and systemic markers of oxidation, inflammation, and antioxidant protection from 66 subjects enrolled in that study. We collected samples at baseline, 2 h after 450 ml of black tea (acute), after 4 weeks of 900 ml of black tea per day (chronic), and after acute and chronic consumption of water. Total catechins increased 33% after acute tea (P < 0.05) and 29% after chronic tea (P < 0.05). Of individual catechins, plasma epicatechin gallate (ECG) concentration significantly increased with acute tea consumption, and plasma epicatechin (EC) increased with chronic tea consumption. Tea consumption did not improve plasma antioxidant capacity and did not reduce urinary 8-hydroxy-2'-deoxyguanosine, or urinary 8-isoprostane levels. Changes in catechin levels did not correlate with changes in endothelial function, plasma markers of oxidative stress, or C-reactive protein. In contrast, endothelial function at baseline correlated with dietary flavonoid intake (beta = 0.32, P = 0.02) and with baseline plasma EC concentration after adjusting for confounding variables (beta = 0.39, P = 0.03). These findings suggest that the benefits of black tea consumption on endothelial function may not be attributable to tea catechins or a systemic antioxidant or anti-inflammatory effect. Chronic dietary flavonoid status appears to relate to endothelial function, possibly suggesting that other flavonoids or polyphenolic components of tea favorably influence vascular health and risk for cardiovascular disease.     

Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green tea

The global prevalence of obesity has increased considerably in the last decade. Tools for obesity management, including caffeine, ephedrine, capsaicin, and green tea have been proposed as strategies for weight loss and weight maintenance, since they may increase energy expenditure and have been proposed to counteract the decrease in metabolic rate that is present during weight loss. A combination of caffeine and ephedrine has shown to be effective in long-term weight management, likely due to different mechanisms that may operate synergistically, e.g., respectively inhibiting the phosphodiesterase-induced degradation of cAMP and enhancing the sympathetic release of catecholamines. However, adverse effects of ephedrine prevent the feasibility of this approach. Capsaicin has been shown to be effective, yet when it is used clinically it requires a strong compliance to a certain dosage, that has not been shown to be feasible yet. Also positive effects on body-weight management have been shown using green tea mixtures. Green tea, by containing both tea catechins and caffeine, may act through inhibition of catechol O-methyl-transferase, and inhibition of phosphodiesterase. Here, the mechanisms may also operate synergistically. In addition, tea catechins have antiangiogenic properties that may prevent development of overweight and obesity. Furthermore, the sympathetic nervous system is involved in the regulation of lipolysis, and the sympathetic innervation of white adipose tissue may play an important role in the regulation of total body fat in general.     

Dose-Dependent Suppression of Tea Catechins with a Galloyl Moiety on Postprandial Hypertriglyceridemia in Rats

Tea has long been believed to be a healthy beverage, and its beneficial effects are almost all attributed to catechins. The effect of catechins on postprandial hypertriglyceridemia in rats was investigated in this study. A lipid emulsion administered orally to rats with (?)-epigallocatechin gallate at a dose of 100 mg/kg resulted in the increase in plasma triacylglycerol being significantly inhibited after 1 and 2 h compared to the case without (?)-epigallocatechin gallate. The effect of (?)-epigallocatechin was weaker than that of (?)-epigallocatechin gallate. A tea extract (THEA-FLAN 90S), mainly composed of catechins with a galloyl moiety, dose-dependently suppressed postprandial triacylglycerol after the administration of a lipid emulsion at doses of 50–200 mg/kg. The administration of the tea extract alone at a dose of 200 mg/kg had no effect on the plasma triacylglycerol level. These results strongly suggest that catechins with a galloyl moiety would be promising agents for suppressing dietary fat absorption through the small intestine.     

黑线仓鼠断乳后能量代谢和脂肪累积的适应性调节

小型哺乳动物能量代谢和脂肪累积的适应性调节是其应对自然环境变化的主要能量学策略,但在不同的生活史阶段,脂肪组织适应性调节的特征和能量机理尚不清楚。为探讨不同繁殖阶段能量代谢和脂肪累积的变化及其内分泌机理,本文测定了黑线仓鼠哺乳期和断乳后摄食量、脂肪重量,以及血清瘦素水平、下丘脑瘦素受体(Ob-Rb)和相关神经肽的基因表达。结果显示,哺乳高峰期黑线仓鼠的脂肪重量几乎降低至零,断乳后显著增加;与非繁殖对照组相比,皮下脂肪、肾周脂肪与腹腔脂肪重量分别增长了1.5倍、37.1倍和1.9倍。断乳后摄食量、血清瘦素水平显著高于非繁殖对照组,Ob-Rb基因表达显著下调,而促食与抑食神经肽的基因表达均未发生显著变化。哺育不同胎仔数的黑线仓鼠在断乳后能量摄入、静止代谢率、身体组分未出现显著差异。研究表明,在不同的繁殖阶段脂肪累积呈现显著的适应性调节,瘦素抵抗是断乳后脂肪累积补偿性增长的重要内分泌机制之一。这对迅速恢复脂肪累积,以应对将来的能量需求增加或者食物资源短缺的环境,进而提高自身的适合度具有重要意义。     

Green tea extract improves endurance capacity and increases muscle lipid oxidation in mice

Green tea contains a high level of polyphenolic compounds known as catechins. We investigated the effects of green tea extract (GTE), which is rich in catechins, on endurance capacity, energy metabolism, and fat oxidation in BALB/c mice over a 10-wk period. Swimming times to exhaustion for mice fed 0.2-0.5% (wt/wt) GTE were prolonged by 8-24%. The effects were dose dependent and accompanied by lower respiratory quotients and higher rates of fat oxidation as determined by indirect calorimetry. In addition, feeding with GTE increased the level of beta-oxidation activity in skeletal muscle. Plasma lactate concentrations in mice fed GTE were significantly decreased after exercise, concomitant with increases in free fatty acid concentrations in plasma, suggesting an increased lipid use as an energy source in GTE-fed mice. Epigallocatechin gallate (EGCG), a major component of tea catechins, also enhanced endurance capacity, suggesting that the endurance-improving effects of GTE were mediated, at least in part, by EGCG. The beta-oxidation activity and the level of fatty acid translocase/CD36 mRNA in the muscle was higher in GTE-fed mice compared with control mice. These results indicate that GTE are beneficial for improving endurance capacity and support the hypothesis that the stimulation of fatty acid use is a promising strategy for improving endurance capacity.     

Effects of CH-19 sweet, a non-pungent cultivar of red pepper, in decreasing the body weight and suppressing body fat accumulation by sympathetic nerve activation in humans

'CH-19 Sweet' is a non-pungent red pepper and enhances the energy expenditure in humans in like manner to the pungent red pepper. We investigated in this study the effects of a repeated intake of CH-19 Sweet for two weeks on the body weight and body fat in humans. Changes in the autonomic nervous activity after ingesting CH-19 Sweet were also measured by a power spectral analysis. We established a new protocol which allows the precise detection of weight change in humans by using fewer subjects. These methods were used to show that the repeated intake of CH-19 Sweet reduced the body weight and suppressed body fat accumulation. Furthermore, the body weight loss due to the repeated intake of CH-19 Sweet was significantly correlated with the sympathetic nervous response after its ingestion. We propose that the repeated intake of CH-19 Sweet reduced the body weight and suppressed body fat accumulation by sympathetic nervous activation in humans.     

Effects of CH-19 Sweet,a Non-Pungent Cultivar of Red Pepper,in Decreasing the Body Weight and Suppressing Body Fat Accumulation by Sympathetic Nerve Activation in Humans

‘CH-19 Sweet’ is a non-pungent red pepper and enhances the energy expenditure in humans in like manner to the pungent red pepper. We investigated in this study the effects of a repeated intake of CH-19 Sweet for two weeks on the body weight and body fat in humans. Changes in the autonomic nervous activity after ingesting CH-19 Sweet were also measured by a power spectral analysis. We established a new protocol which allows the precise detection of weight change in humans by using fewer subjects. These methods were used to show that the repeated intake of CH-19 Sweet reduced the body weight and suppressed body fat accumulation. Furthermore, the body weight loss due to the repeated intake of CH-19 Sweet was significantly correlated with the sympathetic nervous response after its ingestion. We propose that the repeated intake of CH-19 Sweet reduced the body weight and suppressed body fat accumulation by sympathetic nervous activation in humans.     

Heat-epimerized tea catechins have the same cholesterol-lowering activity as green tea catechins in cholesterol-fed rats

Tea catechins are known to be epimerized by heat treatment. The effect of heat-epimerized tea catechins on serum cholesterol concentration was compared with that of green tea catechins. Our observations strongly suggest that both tea catechins and heat-epimerized tea catechins lower serum cholesterol concentration by inhibiting cholesterol absorption in the intestine. There was no differential effect between the two catechin preparations.     

(-)-Epicatechin gallate accumulates in foamy macrophages in human atherosclerotic aorta: implication in the anti-atherosclerotic actions of tea catechins

The localization and target sites of tea catechins underlying their biological activity including anti-atherosclerotic activity have not yet been fully understood. To identify the target sites of catechins in vivo, we have developed a novel monoclonal antibody (mAb5A3) specific for (−)-epicatechin-3-gallate (ECg), one of the major tea catechins. The immunoreactive materials with mAb5A3 were detected in the human atherosclerotic lesions but not in the normal aorta, and were specifically localized in the macrophage-derived foam cells. In vitro experiments using macrophage-like cell lines also showed the significant accumulation of ECg in the cells. We also demonstrated that ECg could suppress the gene expression of a scavenger receptor CD36, a key molecule for foam cell formation, in macrophage cells. These results, for the first time, showed the target site of a tea component ECg in the aorta and might provide a mechanism for the anti-atherosclerotic actions of the catechins.     

温度和高脂食物对黑线仓鼠代谢产热和体脂累积的影响

能量代谢的适应性调节是小型哺乳动物应对环境季节性变化的主要策略之一。为探讨不同温度下动物在代谢产热能量支出与脂肪累积之间的权衡策略,以成年雄性黑线仓鼠为研究对象开展了3 个实验:实验1 将动物驯化于高脂和低脂食物;实验2 将动物暴露于低温(5℃)和暖温(30℃);实验3 将饲喂高脂食物的动物暴露于低温。以食物平衡法测定摄食量、摄入能和消化率,以开放式氧气分析仪测定代谢产热,以索氏抽提法测定脂肪含量。结果发现,取食高脂食物的黑线仓鼠摄食量显著减少,但脂肪累积显著增加;暖温下摄食量显著减少,但体脂含量显著增加,低温下摄食量显著升高,但体脂含量显著减少;饲喂高脂食物的黑线仓鼠在低温下摄入能显著增加,非颤抖性产热增强,但体脂含量显著降低。结果表明高脂食物对黑线仓鼠体脂累积的影响与环境温度有关,低温诱导脂肪动员,暖温促进脂肪贮存;低温下黑线仓鼠增加能量摄入不能完全补偿用于产热的能量支出,导致脂肪动员增加;暖温下代谢产热降低是脂肪累积的主要因素;与能量摄入相比代谢产热的能量支出在体脂累积的适应性变化中发挥更重要的作用。