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Group rearing is a common housing condition, but group-housed older mice show increased adrenal hypertrophy, a marker of stress. However, the ingestion of theanine, an amino acid unique to tea leaves, suppressed stress. We aimed to elucidate the mechanism of theanine's stress-reducing effects using group-reared older mice. The expression of repressor element 1 silencing transcription factor (REST), which represses excitability-related genes, was increased in the hippocampus of group-reared older mice, whereas the expression of neuronal PAS domain protein 4 (Npas4), which is involved in the regulation of excitation and inhibition in the brain, was lower in the hippocampus of older group-reared mice than in same-aged two-to-a-house mice. That is, the expression patterns of REST and Npas4 were found to be just inversely correlated. On the other hand, the expression levels of the glucocorticoid receptor and DNA methyltransferase, which suppress Npas4 transcription, were higher in the older group-housed mice. In mice fed theanine, the stress response was reduced and Npas4 expression tended to be increased. These results suggest that Npas4 expression was suppressed by the increased expression of REST and Npas4 downregulators in the group-fed older mice, but that theanine avoids the decrease in Npas4 expression by suppressing the expression of Npas4 transcriptional repressors. [ABSTRACT FROM AUTHOR]

Being in a prolonged depressed state increases the risk of developing depression. To investigate whether green tea intake is effective in improving depression-like moods, we used an experimental animal model of depression with lipopolysaccharide (LPS) and clarified the effects of green tea on the biological stress response and inflammation in the brain. Regarding the stress reduction effect of green tea, we found that the sum of caffeine (C) and epigallocatechin gallate (E) relative to the sum of theanine (T) and arginine (A), the major components of green tea, or the CE/TA ratio, is important. The results showed that depression-like behavior, adrenal hypertrophy as a typical stress response, and brain inflammation were suppressed in mice fed green tea components with CE/TA ratios of 2 to 8. In addition, the expression of Npas4, which is reduced in anxiety and depression, was maintained at the same level as controls in mice that consumed green tea with a CE/TA ratio of 4. In clinical human trials, the consumption of green tea with CE/TA ratios of 3.9 and 4.7 reduced susceptibility to subjective depression. These results suggest that the daily consumption of green tea with a CE/TA ratio of 4–5 is beneficial to improving depressed mood. [ABSTRACT FROM AUTHOR]

Background: Theanine, an amino acid in tea, has significant anti-stress effects on animals and humans. However, the anti-stress effects of drinking green tea have not yet been elucidated.Hypothesis/purpose: The present study aimed to explore anti-stress effects of green tea and roles of tea components in a mouse model of psychosocial stress.Study Design: We examined anti-stress effects of three types of green teas, theanine-rich "Gyokuro", standard "Sencha", and Sencha with lowered caffeine (low-caffeine green tea). Furthermore, the roles of tea components such as caffeine, catechins, and other amino acids in anti-stress effects were examined.Methods: To prepare low-caffeine green tea, plucked new tea leaves were treated with a hot-water spray. Mice were psychosocially stressed from a conflict among male mice under confrontational housing. Mice consumed each tea that was eluted with room temperature water ad libitum. As a marker for the stress response, adrenal hypertrophy was compared with mice that ingested water.Results: Caffeine was significantly lowered by spraying hot-water on tea leaves. While epigallocatechin gallate (EGCG) is the main catechin in tea leaves, epigallocatechin (EGC) was mainly infused into water at room temperature. Adrenal hypertrophy was significantly suppressed in mice that ingested theanine-rich and low-caffeine green tea that were eluted with water at room temperature. Caffeine and EGCG suppressed the anti-stress effects of theanine while EGC and arginine (Arg) retained these effects.Conclusion: These results suggest that drinking green tea exhibits anti-stress effects, where theanine, EGC and Arg cooperatively abolish the counter-effect of caffeine and EGCG on psychosocial stress induced adrenal hypertrophy in mice. [ABSTRACT FROM AUTHOR]

Epidemiological studies have demonstrated that the intake of green tea is effective in reducing the risk of dementia. The most important component of green tea is epigallocatechin gallate (EGCG). Both EGCG and epigallocatechin (EGC) have been suggested to cross the blood–brain barrier to reach the brain parenchyma, but EGCG has been found to be more effective than EGC in promoting neuronal differentiation. It has also been suggested that the products of EGCG decomposition by the intestinal microbiota promote the differentiation of nerve cells and that both EGCG and its degradation products act on nerve cells with a time lag. On the other hand, the free amino acids theanine and arginine contained in green tea have stress-reducing effects. While long-term stress accelerates the aging of the brain, theanine and arginine suppress the aging of the brain due to their anti-stress effect. Since this effect is counteracted by EGCG and caffeine, the ratios between these green tea components are important for the anti-stress action. In this review, we describe how green tea suppresses brain aging, through the activation of nerve cells by both EGCG and its degradation products, and the reductions in stress achieved by theanine and arginine. [ABSTRACT FROM AUTHOR]

By comprehensively measuring changes in metabolites in the hippocampus of stress-loaded mice, we investigated the reasons for stress vulnerability and the effect of theanine, i.e., an abundant amino acid in tea leaves, on the metabolism. Stress sensitivity was higher in senescence-accelerated mouse prone 10 (SAMP10) mice than in normal ddY mice when these mice were loaded with stress on the basis of territorial consciousness in males. Group housing was used as the low-stress condition reference. Among the statistically altered metabolites, depression-related kynurenine and excitability-related histamine were significantly higher in SAMP10 mice than in ddY mice. In contrast, carnosine, which has antidepressant-like activity, and ornithine, which has antistress effects, were significantly lower in SAMP10 mice than in ddY mice. The ingestion of theanine, an excellent antistress amino acid, modulated the levels of kynurenine, histamine, and carnosine only in the stress-loaded SAMP10 mice and not in the group-housing mice. Depression-like behavior was suppressed in mice that had ingested theanine only under stress loading. Taken together, changes in these metabolites, such as kynurenine, histamine, carnosine, and ornithine, were suggested to be associated with the stress vulnerability and depression-like behavior of stressed SAMP10 mice. It was also shown that theanine action appears in the metabolism of mice only under stress loading. [ABSTRACT FROM AUTHOR]

The young leaves of green tea become lighter in color than usual when protected from sunlight by a shading net for about two weeks while growing. These leaves are called "shaded white leaf tea" or SWLT. In the eluate of SWLT, the amount of amino acids (361 mg/L) was significantly higher than that in regular tea (53.5 mg/L). Since theanine and arginine, the first and second most abundant amino acids in SWLT, have significant antistress effects, we examined the antistress effect of SWLT on humans. SWLT or placebo green tea (3 g) was eluted with room-temperature water (500 mL). Participants consumed the tea for one week prior to pharmacy practice and continued for 10 days in the practice period. The state-trait anxiety inventory, an anxiety questionnaire, tended to be scored lower in the SWLT group than the placebo, but other stress markers showed no differences. The effect of the difference in SWLT components examined with mice showed that aspartic acid and asparagine, which are abundant in SWLT, counteracted the antistress effects of theanine and arginine. Large amounts of caffeine also interfered with SWLT's antistress effect. Thus, SWLT, which is high in caffeine and amino acids, suppressed depressant behavior in mice. [ABSTRACT FROM AUTHOR]

Chronic stress can impair the health of human brains. An important strategy that may prevent the accumulation of stress may be the consumption of functional foods. When senescence-accelerated mice prone 10 (SAMP10), a stress-sensitive strain, were loaded with stress using imposed male mouse territoriality, brain volume decreased. However, in mice that ingested theanine (6 mg/kg), the main amino acid in tea leaves, brain atrophy was suppressed, even under stress. On the other hand, brain atrophy was not clearly observed in a mouse strain that aged normally (Slc:ddY). The expression level of the transcription factor Npas4 (neuronal PAS domain protein 4), which regulates the formation and maintenance of inhibitory synapses in response to excitatory synaptic activity, decreased in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but increased in mice that ingested theanine. Lipocalin 2 (Lcn2), the expression of which increased in response to stress, was significantly high in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but not in mice that ingested theanine. These data suggest that Npas4 and Lcn2 are involved in the brain atrophy and stress vulnerability of SAMP10 mice, which are prevented by the consumption of theanine, causing changes in the expression of these genes. [ABSTRACT FROM AUTHOR]

Theanine, a major amino acid in green tea, exhibits a stress-reducing effect in mice and humans. Matcha, which is essentially theanine-rich powdered green tea, is abundant in caffeine. Caffeine has a strong antagonistic effect against theanine. The stress-reducing effect of matcha was examined with an animal experiment and a clinical trial. The stress-reducing effect of matcha marketed in Japan and abroad was assessed based on its composition. The stress-reducing effect of matcha in mice was evaluated as suppressed adrenal hypertrophy using territorially-based loaded stress. High contents of theanine and arginine in matcha exhibited a high stress-reducing effect. However, an effective stress-reducing outcome was only possible when the molar ratio of caffeine and epigallocatechin gallate (EGCG) to theanine and arginine was less than two. Participants (n = 39) consumed test-matcha, which was expected to have a stress-reducing effect, or placebo-matcha, where no effect was expected. Anxiety, a reaction to stress, was significantly lower in the test-matcha group than in the placebo group. To predict mental function of each matcha, both the quantity of theanine and the ratios of caffeine, EGCG, and arginine against theanine need to be verified. [ABSTRACT FROM AUTHOR]