heart-health

Author: Yohei Mineharu, and Akio Koizumi, and Yasuhiko Wada, and Hiroyasu Iso, and Yoshiyuki Watanabe, and Chigusa Date, and Akio Yamamoto, and Shogo Kikuchi, and Yutaka Inaba, and Hideaki Toyoshima, and Takaaki Kondo, and Akiko Tamakoshi

Background: The effects of coffee and green, black and oolong teas and caffeine intake on cardiovascular disease (CVD) mortality have not been well defined in Asian countries. Methods: To examine the relationship between consumption of these beverages and risk of mortality from CVD, we prospectively followed 76,979 individuals aged 40-79 y free of stroke, coronary heart disease (CHD), and cancer at entry. Daily consumption of beverages was assessed by questionnaires. Results: We documented 1362 deaths from strokes and 650 deaths from CHD after 1,010,787 person-years of follow-up. Compared with non-drinkers of coffee, the multivariable hazard ratios (HRs) and 95% confidence interval for those drinking 1-6 cups/wk, 1-2 cups/d and a ‰Ψ3 cups/d were 0.78 (0.50-1.20), 0.67 (0.47-0.96) and 0.45 (0.17-0.87) for strokes among men (p=0.009 for trend). Compared with non-drinkers of green tea, the multivariable HRs for those drinking 1-6 cups/wk, 1-2 cups/d, 3-5 cups/d and a ‰Ψ6 cups/d were 0.34 (0.06-1.75), 0.28 (0.07-1.11), 0.39 (0.18-0.85), and 0.42 (0.17-0.88) for CHD among women (p=0.038 for trend). As for oolong tea, the multivariable HRs of those drinking 1-6 cups/wk and a ‰Ψ1 cups/d were 1.00 (0.65-1.55) and 0.39 (0.17-0.88) for total CVD among men (p=0.049 for trend). Risk reduction for total CVD across categories of caffeine intake was most prominently observed in the second highest quintile with a 38% lower risk among men and 22% among women. Conclusions: Consumption of coffee, green tea and oolong tea and total caffeine intake was associated with a reduced risk of mortality from CVD.

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Author: Kakuda T, and Hinoi E, and Abe A, and Nozawa A, and Ogura M, and Yoneda Y

We have previously shown that theanine (=γ-glutamylethylamide), an ingredient of green tea, has a protective effect against ischemic neuronal death in the hippocampal CA1 region of the gerbil brain without affecting ligand binding to ionotropic receptor subtypes of the neurotransmitter glutamate structurally related to theanine. The neurotransmitter pool of glutamate is thought to be fueled by the entry of the other structural analog glutamine (Gln) and subsequent cleavage by glutaminase. Although theanine did not inhibit [3H]glutamate accumulation, [3H]theanine was actively accumulated in a temperature-dependent and saturable manner in rat brain synaptosomal fractions. The accumulation of [3H]theanine was markedly inhibited by Gln in a concentration-dependent manner, whereas [3H]Gln accumulation was inhibited by theanine vice versa. Both [3H]theanine and [3H]Gln accumulations were decreased after the replacement of sodium chloride with choline chloride, along with similarly high distribution profiles in telencephalic structures. A similar equilibrium was observed within 30 min at 30°C for the accumulations of both [3H]theanine and [3H]Gln in cultured rat neocortical astroglia as well as neurons, whereas theanine inhibited [3H]Gln accumulation in a concentration-dependent manner at 0.1–10 mM. Furthermore, sustained exposure to 10 mM theanine led to a significant decrease in the level of extracellular glutamate released from cultured neurons. These results suggest that the green tea ingredient theanine would be an inhibitor of different transporters capable of transporting Gln across plasma membranes toward the modulation of the glutamate/Gln cycle required for the neurotransmitter pool of glutamate in neurons.

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Author: Kakuda, T. and Nozawa, A. and Sugimoto, A. and Niino, H. 

In an investigation of the mechanisms of the neuroprotective effects of theanine (gamma-glutamylethylamide) in brain ischemia, inhibition by theanine of the binding of [3H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), [3H]kainate, and [3H](E)-3-(2-phenyl-2-carboxyethenyl)-4,6-dichloro-1-H-indole-2-carboxylic acid (MDL 105,519) to glutamate receptors was studied in terms of its possible inhibiting effects on the three receptor subtypes (AMPA, kainate, and NMDA glycine), with rat cortical neurons. Theanine bound the three receptors, but its IC50 of theanine was 80- to 30,000-fold less than that of L-glutamic acid.

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Author: Hidehiko YOKOGOSHI, and Mikiko MOCHIZUKI, and Kotomi SAITOH

Following the administration of theanine, the brain tryptophan content significantly increased or tended to increase, but the contents of serotonin and 5-hydroxyindole acetic acid (5HIAA) decreased. The use of inhibitors of serotonin metabolism enable us to speculate that theanine reduced serotonin synthesis and also increased serotonin degradation in the brain.

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Author: Song CH, and Jung JH, and Oh JS, and Kim KS

L-theanine Is an amino acid in green tea and has been known to decrease serotonin and increase norepinephrine in rat brains, and also reported to produce mental relaxation, lower blood pressure and improve learning ability in human beings. But, few studies on these effects for human beings have been conducted so far. This study was conducted to evaluate the effect of L-theanine on the release of brain alpha waves known to be related with mental relaxation and concentration. Twenty healthy male volunteers aged 18 to 30 years without any Physical and Psychological diseases were recruited through written advertisement. Alpha power values of EEG as a surrogate marker of mental relaxation and concentration were measured in frontal and occipital regions for 40 minutes after administration of four placebo or test tablets and 20 minute resting period. The same procedure crossed over at 7-day intervals. We analyzed average alpha power values in frontal and occipital regions at 10 minute intervals. Repeated ANOVA revealed that there were significant differences of occipital alpha power values between placebo and test groups with high anxiety (p<0.05). The mean values at 20,30,40,50 and 60 minute intervals were 0.23, 024, 0.28, 0.25 and 0.34 in placebo, respectively and 0.23, 0.29, 0.40, 0.34, and 0.45 in test, respectively. But there were no significant differences of frontal and occipital alpha power values between placebo and test groups with low anxiety (p>0.05) . The results of this study suggest that L-theanine containing tablets promote the release of alpha waves related to mental relaxation and concentration in young adult males.

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Author: Yokogoshi H, and Kobayashi M, and Mochizuki M, and Terashima T

Theanine, r-glutamylethylamide, is one of the major components of amino acids in Japanese green tea. Effect of theanine on brain amino acids and monoamines, and the striatal release of dopamine (DA) was investigated. Determination of amino acids in the brain after the intragastric administration of theanine showed that theanine was incorporated into brain through blood-brain barrier via leucine-preferring transport system. The concentrations of norepinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5HIAA) in the brain regions were unaffected by the theanine administration except in striatum. Theanine administration caused significant increases in serotonin and/or DA concentrations in the brain, especially in striatum, hypothalamus and hippocampus. Direct administration of theanine into brain striatum by microinjection caused a significant increase of DA release in a dose-dependent manner. Microdialysis of brain with calcium-free Ringer buffer attenuated the theanine-induced DA release. Pretreatment with the Ringer buffer containing an antagonist of non-NMDA (N-methyl-D-aspartate) glutamate receptor, MK-801, for 1 hr did not change the significant increase of DA release induced by theanine. However, in the case of pretreatment with AP-5, (+/-)-2-amino-5-phosphonopentanoic acid; antagonist of NMDA glutamate receptor, the theanine-induced DA release from striatum was significantly inhibited. These results suggest that theanine might affect the metabolism and/or the release of some neurotransmitters in the brain, such as DA.

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Author: RYOHEI KIMURA, and TOSHIRO MURATA

Theanine (N-ethylglutamine), a flavourous constituent of tea leaves, was studied in respect of the influence on the central nervous system in mice.
Theanine was shown to inhibit the convulsive action of caffeine, but was ineffective against pentetrazole, picrotoxin, strychnine, pipradrol and bemegride as well as L-glutamine. Neither theanine nor L-glutamine effected on the prolongation of the sleeping time after the injection of hexobarbital sodium in mice. Using 14C-labeled theanine, it was found that the intraperitoneally administered theanine was taken up by brain tissue with out undergoing the metabolic changes in a 30minutes. The intracerebral level of γaminobutyric acid was shown to increase significantly at 30minutes following the intraperitoneal administration of theanine in mice.

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Author: Kim Zarse and Saskia Jabin and Michael Ristow

Author: Tsuge H, and Sano S, and Hayakawa T, and Kakuda T, and Unno T

Author: Lekh Raj Juneja and Djong-Chi Chu and Tsutomu Okubo and Yukiko Nagato and Hidehiko Yokogoshi

Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ‘green’ tea. It was found that L-theanine administered intraperitoneally to rats reached the brain within 30 min without any metabolic change. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure significantly in hypertensive rats. In general, animals always generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely α,β,δ and θ-waves, based on mental conditions. Generation of α-waves is considered to be an index of relaxation. In human volunteers, α-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50–200 mg), signifying relaxation without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine™ (trade name of L-theanine) which offers a tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress. Taiyo Kagaku Co., Ltd, Japan won the 1998 ‘Food Ingredient Research Award’ for development of Suntheanine™ at Food Ingredients in Europe (Frankfurt). The judges felt it was a particularly well-documented and fascinating piece of research.

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