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L-Theanine reduces psychological and physiological stress responses

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Abstract

L-Theanine is an amino acid contained in green tea leaves which is known to block the binding of L-glutamic acid to glutamate receptors in the brain. Because the characteristics of L-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took L-Theanine at the start of an experimental procedure, one in which they took L-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.

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... epigallocatechin gallate [EGCG]) and L-theaninehave demonstrated a range of functional benefits of acute consumption on subjective, physiological and cognitive states under conditions of acute stress provocation. These include increased subjective relaxation and calmness [19], improved subjective mood [20], and attenuated subjective stress [19,21,22], anxiety [22], cortisol [21] and heart-rate [22] responses. Oscillatory brain activity measured by electroencephalogram (EEG) is an emerging marker for assessing the functional benefits of nutrient intake. ...
... epigallocatechin gallate [EGCG]) and L-theaninehave demonstrated a range of functional benefits of acute consumption on subjective, physiological and cognitive states under conditions of acute stress provocation. These include increased subjective relaxation and calmness [19], improved subjective mood [20], and attenuated subjective stress [19,21,22], anxiety [22], cortisol [21] and heart-rate [22] responses. Oscillatory brain activity measured by electroencephalogram (EEG) is an emerging marker for assessing the functional benefits of nutrient intake. ...
... epigallocatechin gallate [EGCG]) and L-theaninehave demonstrated a range of functional benefits of acute consumption on subjective, physiological and cognitive states under conditions of acute stress provocation. These include increased subjective relaxation and calmness [19], improved subjective mood [20], and attenuated subjective stress [19,21,22], anxiety [22], cortisol [21] and heart-rate [22] responses. Oscillatory brain activity measured by electroencephalogram (EEG) is an emerging marker for assessing the functional benefits of nutrient intake. ...
Article
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Background: Magnesium (Mg), green tea and rhodiola extracts have, in isolation, been shown to possess stress and anxiety relieving effects. Green tea and rhodiola have been shown to modulate EEG oscillatory brain activity associated with relaxation and stress perception. The combined capacity of these ingredients to confer protective effects under conditions of acute stress has yet to be examined. We tested the hypothesis that a combination of Mg (with B vitamins) + green tea + rhodiola would acutely moderate the effects of stress exposure. Methods: A double blind, randomised, placebo controlled, parallel group design was employed (Clinicaltrials.gov:NCT03262376; 25/0817). One hundred moderately stressed adults received oral supplementation of either (i) Mg + B vitamins + green tea + rhodiola; (ii) Mg + B vitamins + rhodiola; (iii) Mg + B vitamins + green tea; or (iv) placebo. After supplementation participants were exposed to the Trier Social Stress Test. The effects of the study treatments on electroencephalogram (EEG) resting state alpha and theta, subjective state/mood, blood pressure, heart rate variability and salivary cortisol responses after acute stress exposure were assessed. Results: The combined treatment significantly increased EEG resting state theta (p < .02) - considered indicative of a relaxed, alert state, attenuated subjective stress, anxiety and mood disturbance, and heightened subjective and autonomic arousal (p < .05). Conclusions: Mg, B vitamins, rhodiola and green tea extracts are a promising combination of ingredients that may enhance coping capacity and offer protection from the negative effects of stress exposure.Trial registration: ClinicalTrials.gov identifier: NCT03262376.
... high temperatures and changes in Explor Res Hypothesis Med pH) can reduce the functionality of L-THE, while its combination with some ingredients (such as caffeine and other amino acids) may interfere with its absorption. 3 Various studies report stress lowering effects (post-200 mg consumption in its pure form), demonstrated physiologically as reductions in heart rate (HR) 8 as well as reductions in salivary cortisol that indicate the potential interaction between L-THE and hypothalamic-pituitary-adrenal (HPA) axis system responses. 8,9 Moreover, consumption of L-THE (250 mg) is reported to halt the increase in blood pressure (BP) 10 that is thought to occur due to L-THE's effect on blood vessels in the peripheral nervous system via the mechanism of vasodilation, which could highlight the effect of L-THE on cardiovascular structures and the interaction between vascular tone and the BP response. ...
... 3 Various studies report stress lowering effects (post-200 mg consumption in its pure form), demonstrated physiologically as reductions in heart rate (HR) 8 as well as reductions in salivary cortisol that indicate the potential interaction between L-THE and hypothalamic-pituitary-adrenal (HPA) axis system responses. 8,9 Moreover, consumption of L-THE (250 mg) is reported to halt the increase in blood pressure (BP) 10 that is thought to occur due to L-THE's effect on blood vessels in the peripheral nervous system via the mechanism of vasodilation, which could highlight the effect of L-THE on cardiovascular structures and the interaction between vascular tone and the BP response. 3 These stress-related responses are heavily regulated by the autonomic nervous system (ANS), comprising the parasympathetic nervous systems (PNS) and sympathetic nervous system (SNS) that are key to maintaining allostasis, the process of achieving homeostatic stability through change. ...
... 1 Due to its effect on the stress response, we hypothesize that L-THE will influence the physiological outcomes of the ANS, including but not limited to HR, HRV, BP and the HPA stress response via the salivary biomarker cortisol. 3,5, 8 The consumption of L-THE has also been reported to have a profound effect on concentration and increasing alertness, which may improve the speed and accuracy of eye movements, and due to its effects on glutamatergic neurotransmission, may also alter neurophysiological responses in the retina. 13 Furthermore, L-THE is proposed to affect cognitive performance and increase alertness 14 ; therefore, investigating saccadic eye movements (SEMs; the shift in rapid eye movements between objects of visual interest), as well as contrast sensitivity (CS) and visual acuity (VA), which are markers of retinal function, may further the understanding of neurophysiological responses in humans post-L-THE consumption. ...
... To our knowledge, however, only its acute effects have been investigated in healthy individuals. The anti-stress effects of L-theanine (200 mg/day) have been observed following once- [33,34] and twice daily [35] administration, while its attention-improving effects have been observed in response to treatment of 100 mg/day on four separate days [36] and 200 mg/day single administration [37], which was further supported by decreased responses in functional magnetic resonance imaging [38]. Moreover, L-theanine has been suggested to have potential therapeutic effects in psychiatric disorders [39]. ...
... Placebo tablet was the same as L-theanine tablet in terms of appearance and taste. This dose was chosen because it was found to be effective in a previous study [48], which was normal dose as also used in other studies [33][34][35]37]. However, the dose was relatively high compared to the median amount of L-theanine per cup of green tea (8-30 mg) [49]. ...
... For stress-related symptoms, SDS, STAI-T, and PSQI scores decreased after four weeks Ltheanine administration. These findings are consistent with previous studies in rodents [6,[22][23][24][25][26][27], acute effects reported in healthy humans [31][32][33][34][35], and chronic effects in patients with MDD [40]. Additionally, this trial suggests, for the first time, that 4 weeks L-theanine administration is effective in improving stress-related symptoms in healthy adults. ...
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This randomized, placebo-controlled, crossover, and double-blind trial aimed to examine the possible effects of four weeks L-theanine administration on stress-related symptoms and cognitive functions in healthy adults. Participants were 30 individuals (nine men and 21 women; age: 48.3 ± 11.9 years) who had no major psychiatric illness. L-theanine (200 mg/day) or placebo tablets were randomly and blindly assigned for four-week administration. For stress-related symptoms, Self-rating Depression Scale, State-Trait Anxiety Inventory-trait, and Pittsburgh Sleep Quality Index (PSQI) scores decreased after L-theanine administration (p = 0.019, 0.006, and 0.013, respectively). The PSQI subscale scores for sleep latency, sleep disturbance, and use of sleep medication reduced after L-theanine administration, compared to the placebo administration (all p < 0.05). For cognitive functions, verbal fluency and executive function scores improved after L-theanine administration (p = 0.001 and 0.031, respectively). Stratified analyses revealed that scores for verbal fluency (p = 0.002), especially letter fluency (p = 0.002), increased after L-theanine administration, compared to the placebo administration, in individuals who were sub-grouped into the lower half by the median split based on the mean pretreatment scores. Our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.
... Following removal of duplicates (n = 40), reviews, letters to the editor and articles not written in English (n = 177), the number of articles was reduced to 44. Nine articles [38,44,[46][47][48][49][50][51][52] met the inclusion criteria ( Fig. 1). Seven studies recruited participants with no known preexisting mental health issues, while two studies used participants with an existing mental health condition [44,49]. ...
... The total number of participants for all included studies was 270 with 134 males and 88 females ( Table 1). Two studies were conducted in males only [46,47], and one study did not provide the genders of its 48 participants [38]. ...
... The other three studies were designed to test for chronic effects and involved interventions over periods between seventeen days [50] to eight weeks [44,49]. In the acute single day intervention trials, participants consumed 200 mg/day [46][47][48]52], while in the chronic trials, Primary database search: n=261 ...
Article
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The green tea amino acid, L-theanine (L-THE) is associated with several health benefits, including improvements in mood, cognition and a reduction of stress and anxiety-like symptoms. This systematic review evaluated the effect of pure L-THE intake, in the form of orally administered nutritional supplements, on stress responses and anxiety levels in human randomised controlled trials. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, 9 peer-reviewed journal articles were identified where L-THE as a supplement was compared to a control. Our findings suggest that supplementation of 200-400 mg/day of L-THE may assist in the reduction of stress and anxiety in people exposed to stressful conditions. Despite this finding, longer-term and larger cohort clinical studies, including those where L-THE is incorporated into the diet regularly, are needed to clinically justify the use of L-THE as a therapeutic agent to reduce stress and anxiety in people exposed to stressful conditions.
... In addition, the consumption of L-THE is associated with antihypertensive [12,13], anti-inflammatory properties [8] as well as improvements in cognitive functioning in healthy adults [14] and when consumed in combination with caffeine [10]. Studies report stress lowering effects, expressed physiologically in the form of reductions in heart rate (HR), observed post-completion of a stress-inducing mental arithmetic task after the consumption of L-THE (200 mg) in its relatively pure form [15]. Furthermore, reductions in salivary cortisol post L-THE consumption indicate the putative involvement of L-THE in hypothalamic-pituitary-adrenal (HPA) axis responses have also been reported [15,16]. The autonomic nervous system (ANS), consisting of the sympathetic nervous system (SNS) and parasympathetic nervous systems (PNS) [17,18], are of central importance to the homeostatic stress response. ...
... In addition, the consumption of L-THE is associated with antihypertensive [12,13], anti-inflammatory properties [8] as well as improvements in cognitive functioning in healthy adults [14] and when consumed in combination with caffeine [10]. Studies report stress lowering effects, expressed physiologically in the form of reductions in heart rate (HR), observed post-completion of a stress-inducing mental arithmetic task after the consumption of L-THE (200 mg) in its relatively pure form [15]. Furthermore, reductions in salivary cortisol post L-THE consumption indicate the putative involvement of L-THE in hypothalamic-pituitary-adrenal (HPA) axis responses have also been reported [15,16]. The autonomic nervous system (ANS), consisting of the sympathetic nervous system (SNS) and parasympathetic nervous systems (PNS) [17,18], are of central importance to the homeostatic stress response. ...
... As such, these results fall in line with the study by Dodd et al. [10], who also reported no significant differences in HR when pure L-THE was consumed via capsule intake (50 mg); however, this may have occurred due to the low dose provided to participants. In comparison, our results were not on par with those reported by Kimura et al. [15], where consumption of 200 mg L-THE dissolved in water actively resulted in the reduction of HR in response to an acute mental arithmetic stressor task. In the design of our current study, we did not implement a mental stressor task to alter HR, and in future, may benefit from adding a mentally stressing intervention such as arithmetic task. ...
Article
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Consumption of L-Theanine (L-THE) has been associated with a sensation of relaxation, as well as a reduction of stress. However, these physiological responses have yet to be elucidated in humans where L-THE is compared alongside food or as a functional ingredient within the food matrix. The aim of this study was to determine the physiological responses of a single intake of a potential functional food product (mango sorbet) containing L-THE (ms-L-THE; 200 mgw/w) in comparison to a flavour and colour-matched placebo (ms). Eighteen healthy male participants were recruited in this randomised, double-blind, placebo-controlled trial. The participants were required to consume ms-L-THE or placebo and their blood pressure (BP) (systolic and diastolic), heart rate (HR), and heart rate variability (HRV) were monitored continuously over 90 minutes. Eleven males (age 27.7 ± 10.8 years) completed the study. Changes in area under the curve for systolic and diastolic blood pressure and HRV over the 90 minute observation period indicated no differences between the three conditions (all p > 0.05) or within individual groups (all p > 0.05). The values for heart rate were also not different in the placebo group (p = 0.996) and treatment group (p = 0.066), while there was a difference seen at the baseline (p = 0.003). Based on the findings of this study, L-THE incorporated in a food matrix (mango sorbet) demonstrated no reduction in BP or HR and showed no significant parasympathetic interaction as determined by HRV high-frequency band and low-frequency/high-frequency ratio. Further studies should be focussed towards the comparison of pure L-THE and incorporation within the food matrix to warrant recommendations of L-THE alongside food consumption.
... It is important to highlight that this potential activation of the central nervous system was not accompanied by an increase in the HR or decrease in the HRV (as a proxy of physiological stress) in our study participants. Indeed, this could be explained by the inclusion of L-theanine as a dietary ingredient in the nootropic because it can counteract the potential effects derived from a high dose of caffeine on anxiety (42), psychological stress (43), blood pressure (42), and HR (43), which completely agrees with our results. ...
... It is important to highlight that this potential activation of the central nervous system was not accompanied by an increase in the HR or decrease in the HRV (as a proxy of physiological stress) in our study participants. Indeed, this could be explained by the inclusion of L-theanine as a dietary ingredient in the nootropic because it can counteract the potential effects derived from a high dose of caffeine on anxiety (42), psychological stress (43), blood pressure (42), and HR (43), which completely agrees with our results. ...
Article
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Aim To study the acute effect of a dietary multi-ingredient nootropic on cognitive performance in young healthy adults. We also analyzed the influence of the dietary multi-ingredient nootropic on emotional state, heart rate (HR), and heart rate variability (HRV). Methods This is a randomized, triple-blinded, placebo-controlled, crossover trial. In total, 26 young healthy adults (50% women; 24.9 ± 3.3 years old) ingested 10 g of a dietary multi-ingredient nootropic [Evo-Gamers ® ; Harrison Sport Nutrition (HSN), Granada, Spain] or placebo (maltodextrin) in a randomized order ( clinicaltrials.gov No. NCT04790188). After 30 min of the ingestion, participants performed a battery of cognitive performance tests to measure the processing speed, inhibitory control, working memory, cognitive flexibility, creativity, and verbal fluency. The emotional status was assessed through questionnaires, and HR and HRV were measured using a heart rate monitor. Results In comparison with placebo, the acute ingestion of the nootropic showed a significantly better response time in several cognitive tests (i.e., processing speed, inhibitory control, spatial working memory, and cognitive flexibility, all P < 0.05 and effect size range of 0.4–0.6). It also displayed a higher accuracy in the processing speed, the inhibitory control, and cognitive flexibility tests (all P < 0.05; effect size ranged from 0.4 to 0.6). Furthermore, the nootropic showed a higher creativity and positive emotions and lower sadness-depression emotions, whereas HR and HRV remained similar between placebo vs. nootropic conditions. However, there were no differences between the nootropic and placebo in verbal fluency, motivation, or anxiety (all P > 0.05). Conclusion An acute ingestion of a dietary multi-ingredient nootropic enhances cognitive performance in comparison with placebo without negatively influencing HR or HRV in young healthy adults.
... Animal studies on theanine have shown improved behavior under stressful conditions [11] and improved learning ability under socially stressful conditions [12]. Human studies demonstrated a decrease in heart rate and salivary secretory immunoglobulin A (s-IgA), a type of immunoglobulin in the mucous membrane, when participants were exposed to acute stress [13]. Theanine also has beneficial effects on cognitive function. ...
... Theanine is a green tea ingredient that exhibits anti-stress activity. Animal studies have reported that cortisol is reduced after stress loading [13] and that the increase in heart rate and s-IgA caused by restraint stress is suppressed [55]. Theanine acts as a partial agonist to the N-methyl-D-aspartate receptor, a glutamine receptor [56]. ...
Article
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Matcha, a type of green tea, has a higher amino acid content than other types of tea. We previously examined the ability of matcha to improve cognitive function in older adults and determined that continuous matcha intake improves attention and executive function. This study aimed to compare the effects of matcha and caffeine and clarify the differences between these effects. The study was registered at the University Hospital Medical Information Network (UMIN000036578). The effect of single and continuous intake was compared, and the usefulness of continuous intake was evaluated under the stress condition. The Uchida–Kraepelin test (UKT) was used to induce mild acute stress, and the Cognitrax was used to evaluate cognitive function. A single dose of caffeine improved attentional function during or after stress loading. The reduced reaction time in the Cognitrax, observed following a single dose of matcha, was likely due to caffeine. The matcha group showed an increase in the amount of work after continuous intake, whereas the caffeine group only showed an increase in the amount of work for the UKT after a single dose. Ingesting matcha with caffeine improves both attention and work performance when suffering from psychological stress compared with caffeine alone.
... We have previously reported that theanine (l-theanine, N-ethyl-glutamine), a nonprotein amino acid that is specific to tea, suppressed stress-derived malfunctions in aged mice that had been chronically stressed under confrontational housing (Unno et al., 2011). Furthermore, the intake of theanine suppressed excessive tension in students (Unno et al., 2013b;Kimura et al., 2007). Since theanine has been reported to have various beneficial effects besides antistress effect (e.g., Türközü and Şanlier, 2017), industrially produced theanine has been marketed as tablets or powder supplements (Mu et al., 2015). ...
... In tea leaves, theanine (l-theanine, N-ethyl-l-glutamine) is the most abundant amino acid, and is followed by Arg and glutamic acid (Glu). Theanine has shown a positive effect on stress reduction (Unno et al., 2013a,b, 2011, Yin et al., 2011Kimura et al., 2007), relaxation (Weeks, 2009), cognitive function (Lardner, 2014;Kakuda, 2011), emotional status (Garay et al., 2015;Arroll et al., 2014), and sleep quality (Rao et al., 2015;Barrett et al., 2013). The tests of acute and chronic toxicity on the safety of theanine have shown that theanine is reliable even if it is consumed in excess in a diet (Türközü and Şanlier, 2017). ...
... The state of relaxation is conducive to the acquisition of knowledge and improves cognitive performance (Juneja et al., 1999). It greatly minimizes stress and the excessive stimulation it causes and regulates the frequency of heart rate (HR) (Juneja et al., 1999;Kimura, Ozeki, Juneja, & Ohira, 2007). The number of salivary immunoglobulins (s-IgA), which are commonly associated with the body's response to a threat, is also reduced (Kimura et al., 2007). ...
... It greatly minimizes stress and the excessive stimulation it causes and regulates the frequency of heart rate (HR) (Juneja et al., 1999;Kimura, Ozeki, Juneja, & Ohira, 2007). The number of salivary immunoglobulins (s-IgA), which are commonly associated with the body's response to a threat, is also reduced (Kimura et al., 2007). It also has a lowering effect on blood pressure and helps to fight obesity (Juneja et al., 1999). ...
Article
One of the most popular edible species of wild mushrooms in many countries is Imleria badia (Fr.) Vizzini. It is a species valued due to its taste, intense aroma after drying and dietary, medicinal properties. Significant amounts of carbohydrates, proteins, polyunsaturated fatty acids and β-tocopherol, but also γ-tocopherol were determined in I. badia fruiting bodies. The presence of low molecular weight organic acids: malic, citric, fumaric and oxalic acids, and phenolic compounds with antioxidant properties, such as p-hydroxybenzoic acid, cinnamic acid and protocatechuic acid, were also found. This species is high in another antioxidant compound – theanine. Recent reports indicated that I. badia fruiting bodies’ extracts showed favorable therapeutic and health-promoting benefits and showed their anti-inflammatory, anti-cancer and antioxidant potential, consisting mainly in an inhibition of lipid peroxidation. Biological properties were also determined and confirmed for mycelium obtained from in vitro cultures of I. badia.
... Theanine, the most abundant free amino acid in green tea, has been found to relieve stress and have a relaxing effect [22][23][24][25][26]. In addition, arginine, which is the second most abundant free amino acid in Japanese green tea, has an anti-stress effect similar to theanine [27,28]. ...
... Furthermore, it has been reported that theanine's effects on neurotransmitters in the brain, such as dopamine [66], suppress excitation by caffeine [69], improve memory [70], have a high affinity for the glutamine transporter [70], and enact a neurogenic effect [71]. As regards the actions of theanine in humans, a relaxing effect [26], stress reduction [24,25], and a reduction in depression and schizophrenia [72] have been reported. On the other hand, little attention has been paid to the functionality of arginine in green tea, but it has been revealed to have an excellent stress-reducing effect, similar to that of theanine [27,28]. ...
Article
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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.
... It is present in matcha and has antistress effects [22][23][24]. In human studies, theanine reduced heart rate and salivary immunoglobulin A (s-IgA) responses to acute stress [25]. Theanine was also reported to improve cognitive function in senescence-accelerated mice [26] and to facilitate neurogenesis in the hippocampus of developing rats [27]. ...
Article
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Tea is a beverage commonly consumed worldwide. Matcha is a type of green tea produced by drying and grinding tea leaves (Camellia sinensis L.) into a fine powder. Matcha contains catechin, theanine, and caffeine, which affect cognitive function. Epidemiological studies conducted in Japan have shown that green tea consumption improves cognitive impairment. Previously, we found that daily matcha intake improves attention and executive function in middle-aged and older people. However, its effect on cognitive function in younger adults remains unclear. Moreover, it is unclear which cognitive functions are impaired by stress. This study aimed to clarify whether the administration of matcha improves the attentional function of young adults after mild acute stress and which cognitive function is improved. We included 42 participants aged 25–34 years who consumed 2 g of matcha daily for two weeks. The Uchida–Kraepelin test was used to induce mild acute psychological stress and evaluated memory, attention, facial expression recognition, working memory, visual information, and motor function. Reaction times on the Stroop test for attentional function were significantly lower in the matcha group than in the placebo group. Correct hits in the emotion perception test increased significantly for participants in the matcha group compared to those in the placebo group. We found no significant between-group differences in the other tests. In conclusion, after 2 weeks of matcha intake, the attentional function was maintained after mild acute psychological stress. Thus, matcha might improve cognitive function during or after stress conditions in young adults.
... Tryptophan works with vitamin B6, niacin and magnesium to synthesize serotonin. (Kimura et al., 2007). Thus consumption of tryptophan rich diet has somehow helped in maintaining the stress level of body. ...
Article
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It is generally recognized that there is a relationship between nutrition and immunity or health. From past 20 years onwards, the relationship of immunity with psychological and neurological factors is also becoming clear. In the last 20 years, it has become much clearer that psychological and neurological factors also influence immunity. A healthy diet, not deficient in energy, nutrients and micronutrients is essential to prevent and fight off diseases. Through various researches it can be said that nutrition affects the immune system of our body directly and indirectly. During inflammation, the release of pro-inflammatory cytokines not only leads to activation of immune cells but also to a decrease in appetite and increased catabolism of muscle tissue. In conclusion, there is an intricate relationship between stress, nutrition and immunity.
... Vitamin P (Ruthin) is an equally important biochemical component of tea plants, it increases the absorption of ascorbic acid. [23,24] Studies have shown depending on the season of tea leaf collection, the content of Ruthin in green tea ranges from 36 mg. 100g -1 to 41 mg. ...
Article
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A complete biochemical evaluation of raw materials (3-leaf sprouts) and finished (black, green) tea was performed. The content of the vitamin C by cultivars and forms was from 100 to 148 mg. 100g-1. We determined increase ascorbic acids (AA) from May to August. The plants with a relatively stable content of vitamin C in sprouts are more valuable. Our research show, that during processing raw materials (fresh sprouts) to finished tea, there are significant losses of AA (up to 90%). Studies have shown that depending on the season of tea leaf collection, the content of Ruthin in green tea ranges from 36 mg. 100g-1 to 41 mg. 100g-1 , and in black tea-in the range of 17 mg.100g-1-20 mg.100g-1 , which is lower than in green tea. The content of Ruthin in black and green tea was similar content of ascorbic acid. On average Ruthin in green tea is 3 times more than in black tea. The variation of vitamins in both sprouts and ready-made tea has been established, which is due to both varietal characteristics and the influence of weather conditions of vegetation. Varieties and forms with a high content of ascorbic acid and Ruthin were determined, which increases the nutritional value of the finished beverage. It is important to research the rules about accumulation and distribution of biological substances in tea plants, which will provide scientific ideas about how to control contents and will increase biological active substances in new tea cultivar.
... Theanine also provides relief of PMS symptoms, blood pressure regulation and enhancement of memory and concentration [9] . Kimura et.al (2007) showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress condition [10] . Bryan et al.(2008) suggests that caffeinated tea when ingested at regular intervals may maintain alertness, focused attention accuracy and may modulate the more acute effects of higher doses of caffeine [11] . ...
Research
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Food and mood are regular consistent part of our lives and they inevitably get tangled up together. This review study aims to find out the physiochemical and biochemical relationships and the exact mechanism that binds food with mood. Results showed that caffeine improves vigilance, alertness, mood and cognitive processes during and after exercise. L-theanine a major component of tea, has anxiolytic and calming effect due to its up-regulation of inhibitory neurotransmitters and possible modulation of serotonin and dopamine in selected areas. Antidepressant-like effect of chocolate can most likely be attributed to the antioxidant potential of cocoa polyphenol which reduces hunger and elevates mood.n-3 PUFA present in fish oil exerts anti-depressant effect. Folic acid and Vitamin C is beneficial for the reduction of Childhood Depression.
... Many studies have shown that Thea exhibits an excellent antistress effect [5][6][7][8]. In addition, arginine (Arg), which is the next most abundant amino acid after Thea, also exhibits an excellent antistress effect, similar to the effect theanine has on mice [9]. ...
Article
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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.
... As one of the most popular beverages worldwide, tea (Camellia sinensis) contains a variety of bioactive components that are beneficial to human health, e.g. polyphenols, proteins, polysaccharides, caffeine and amino acids (theanine) (Chen et al., 2009;Kimura et al., 2007;Tenore et al., 2015;Vidyasagar et al., 2013;Wang et al., 2014). Protein is one of the major macromolecular components of tea infusion, influencing the bioactivity, sensory quality and stability of tea beverages typically via protein-polyphenol interactions (Lin et al., 2014;Xu et al., 2012;Yin et al., 2009). ...
Article
Polyphenols are important active components of tea. Tea polyphenol oxidase (PPO) catalyzes polyphenols oxidation, hence it is vitally important to the quality and function of black tea. The enzyme was believed to be mostly deactivated during the thermal processing. Here we report the macromolecular fraction of a Chinese black tea (Camellia. sinensis var. Lapsang souchong) infusion oxidized pyrocatechol even at the enzyme's deactivation temperature. Utilizing urea-assisted extraction and ion-exchange chromatography, the PPOs and/or co-enzymes were isolated from the tea infusion and the cold water extracts of fresh tea leaves. The isolates were found to exhibit PPO activities after removing urea by dialysis. A 66.0 kDa PPO with specific activity of 1200 U/mg (Km = 6.973 mM and Vmax = 15.79 U/min) was purified and characterized to be a glycoprotein with isoelectric point of 4.82. The efficiency of four inhibitors against this PPO are cysteine > EDTA > sodium sulfite > ascorbic acid. The PPOs isolated from black tea infusion reserved 40–80% of activities of their aliquots from fresh tea leaves. It reveals the PPOs can survive the thermal processing of the black tea, possibly in form of PPO-polyphenol complex. Exploring the biochemistry and oxidation mechanism of tea infusion, this study may empower the future development of tea and plant-based beverages.
... Non-proteinogenic amino acid, found to relieve stress and improve sleep quality related to fatigue [72] L-Theanine Amino acid analogue of the proteinogenic amino acids L-glutamate and L-glutamine, constituent of green tea; decreased anxiety, along with benefits to sleep quality in attention deficit hyperactivity disorder (ADHD) [73,74] L-Tryptophan Amino acid that is used in the biosynthesis of proteins; converted into 5-hydroxytryptophan (5-HTP) which is then converted into serotonin and melatonin; dietary supplement used antidepressant, anxiolytic, and sleep aid with limited evidence for depression [75] Melatonin Hormone of the pineal gland which regulates the sleep-wake cycle with antioxidant properties; improves sleep and has an anti-depressant effect [76] Methylsulfonylmethane (MSM) Organosulfur compound; used in alternative medicine with no known medical benefits for psychiatric disorders, which crosses the blood-brain-barrier [77,78] ...
... Oral ingestion of theanine has been shown to be beneficial for brain wellness in healthy humans as well as patients suffering from particular neurodegenerative diseases and neuropsychiatric disorders for years. In healthy human subjects, oral ingestion of theanine led to protection against different responses to psychological and physiological stressors [67]. Oral intake of theanine was more effective in alleviating the elevations of both anxiety and blood pressure than caffeine in human adults with stressful tasks [68]. ...
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Theanine is an amino acid abundant in green tea with an amide moiety analogous to glutamine (GLN) rather than glutamic acid (Glu) and GABA, which are both well-known as amino acid neurotransmitters in the brain. Theanine has no polyphenol and flavonoid structures required for an anti-oxidative property as seen with catechins and tannins, which are more enriched in green tea. We have shown marked inhibition by this exogenous amino acid theanine of the uptake of [3H]GLN, but not of [3H]Glu, in rat brain synaptosomes. Beside a ubiquitous role as an endogenous amino acid, GLN has been believed to be a main precursor for the neurotransmitter Glu sequestered in a neurotransmitter pool at glutamatergic neurons in the brain. The GLN transporter solute carrier 38a1 (Slc38a1) plays a crucial role in the incorporation of extracellular GLN for the intracellular conversion to Glu by glutaminase and subsequent sequestration at synaptic vesicles in neurons. However, Slc38a1 is also expressed by undifferentiated neural progenitor cells (NPCs) not featuring a neuronal phenotype. NPCs are derived from a primitive stem cell endowed to proliferate for self-renewal and to commit differentiation to several daughter cell lineages such as neurons, astrocytes, and oligodendrocytes. In vitro culture with theanine leads to the marked promotion of the generation of new neurons together with selective upregulation of Slc38a1 transcript expression in NPCs. In this review, we will refer to a possible novel neurogenic role of theanine for brain wellness through a molecular mechanism relevant to facilitated neurogenesis with a focus on Slc38a1 expressed by undifferentiated NPCs on the basis of our accumulating findings to date.
... Diğer bir kohort çalışmada, yeşil çay tüketimi ile ilgili olarak yaşlılarda depresif belirtilerin görülme sıklığının daha düşük olduğu saptanmıştır [91]. Bunların yanında theanine'in, kortikal nöron uyarılmasının önleyerek psikolojik ve fizyolojik stres tepkilerini azaltması sonucu anti-stres etkilerine neden olabileceği düşünülmektedir [92]. Antiobesity effects of green tea catechins: a ...
... Die Aktivität der Gehirnwellen gibt Aufschluss über das Bewusstsein eines Menschen: Alpha-Wellen werden vermehrt in entspannenden Situationen (Schlaf-Wach Übergang) ausgeschüttet, Beta-Wellen (13 -über 100 Hz) im wachen und gespannten Zustand, Theta-Wellen (4 -7 Hz) entstehen überlicherweise im Schlaf und Deltawellen (1 -3 Hz) treten hauptsächlich im Tiefschlaf auf. Sowohl die regenerativen, als auch die anregenden Eigenschaften von Theanin können durch die die Modulierung des Stresslevels erklärt werden.127,128 Kaum verwunderlich also, dass Theanin entspannend wirkt.• ...
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... L-theanine, the main amino acid in tea, is also said to ease the symptoms of cognitive impairment and assisted in the hippocampal long-term potentiation of Alzheimer's disease in mice [41]. Its role in anxiety and stress relief and improving sleep quality is commonly known [42,43], and it has been suggested to possess the ability to prevent stress-induced brain atrophy by modifying early stress responses [44]. Caffeine, which is abundant in tea, strengthens the effect of theanine on the enhancement of neurophysiological performance, such as attention [45]. ...
Article
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Matcha Green Tea Powder contains a variety of active ingredients beneficial to health, such as tea catechins, lutein and vitamin K. It is also known that these ingredients confer benefits upon cognitive functions of elderly people. Therefore, we aimed to investigate the relationship between a daily supplementation of Matcha and the change in cognitive functions of community-dwelling elderly people. A randomized, double-blind, placebo-controlled 12-week trial was performed. Sixty-one participants were recruited and randomly assigned to receive test drink containing 3 g powder from fresh Matcha or placebo powder per day. Changes in cognitive function were assessed utilizing a psychometric test battery. Daily food intake was assessed by a Brief-type Self-administered Diet History Questionnaire (BDHQ). In the gender-specific analysis, a significant cognitive enhancement was observed in the Montreal Cognitive Assessment (MoCA) score in the active group of women. In dietary analysis, we found a significant inverse correlation between consumption of vitamin K in daily diet, excluding test drinks, and change in MoCA. The present study suggests that daily supplementation of Matcha Green Tea Powder has protective effects against cognitive decline in community-dwelling elderly women.
... Given that hyperarousal may be exacerbated by many factors such as work or financial stress, the aim of this study was to investigate whether four weeks of oral daily intake of the supplement would improve various sleep factors in Malaysians suffering from poor sleep quality. Numerous studies were conducted either on CTH [15,30] or L-theanine [16,21,31,32], or with other supplement combinations [25], and they showed mixed effects. To our knowledge, this is the first clinical trial that studied the possible effect of the combination of CTH and L-theanine on alpha power and salivary cortisol concentration besides sleep quality. ...
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This randomized, placebo-controlled, crossover and double-blind study investigates the effects of RLX2™ containing alpha-s1-casein tryptic hydrolysate and L-theanine in working adults affected by poor sleep quality. The supplement or placebo was randomly and blindly assigned to 39 subjects for four weeks and the changes in the subjective sleep assessment via the Pittsburgh Sleep Quality Index (PSQI), heart rate, blood pressure, salivary cortisol by high-performance liquid chromatography method and alpha power of awake electroencephalogram (EEG) were studied. The data were analyzed in two ways, by crossover and crossover summed up. The latter depicted that RLX2™ improved PSQI total score, sleep latency, sleep duration, sleep habitual efficiency, daytime dysfunction, and increased total and frontal alpha power significantly (p < 0.05). The supplement prolonged the total sleeping time by 45 min in the supplement receiving group compared to the placebo group (p < 0.001). However, only sleep duration and sleep habitual efficiency showed a profound effect in both analyses (p < 0.05). In conclusion, being given its beneficial effects without notable adverse events, it would be advantageous to use these nutraceutical ingredients to promote better sleep quality. Further studies with a larger number participants are warranted to support these findings.
... Green tea is comprised of flavonoids, including L-theanine, and its acute intake in the form of tea or supplements is associated with functional benefits on subjective, physiological, and psychological states in acute stress conditions [6,12,39,41]. These include enhanced subjective relaxation, calmness, mood, reduced vigilance and stress, anxiety, cortisol, and heart-rate responses [6,12,[42][43][44]. Rhodiola has been used as a traditional medicine to relieve stress, anxiety, and fatigue. ...
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The effect of a combination of magnesium, vitamins B6, B9, B12, rhodiola and green tea/L-theanine (Mg-Teadiola) on stress was evaluated in chronically stressed, otherwise healthy individuals. Effects on stress-related quality-of-life parameters (sleep and perception of pain) were also explored. Adults with stress for ≥1 month, scoring ≥14 points on the Depression Anxiety Stress Scale (DASS)-42 questionnaire, were randomized (1:1) to receive oral Mg-Teadiola (n = 49) or a placebo (n = 51), for 28 days, with a follow-up assessment on Day 56 (NCT04391452). The primary endpoint was the change in the DASS-42 stress score from baseline to Day 28 with Mg-Teadiola versus placebo. The DASS-42 stress scores significantly decreased from baseline to Day 28 with Mg-Teadiola versus placebo (effect size, 0.29; 95% CI [0.01, 0.57]; p = 0.04). Similar reductions were observed on Day 14 (p = 0.006) and Day 56 (p = 0.02). A significant reduction in sensitivity to cold pain (p = 0.01) and a trend for lower sensitivity to warm pain was observed (p = 0.06) on Day 28. Improvements in daytime dysfunction due to sleepiness (Pittsburgh Sleep Quality Index-7 component score) were reported on Day 28, and were significant on Day 56 (p < 0.001). Mg-Teadiola is effective in managing stress in otherwise healthy individuals. Its beneficial effects on sleep and pain perception need further investigation.
... L-theanine stimulates the generation of dopamine and serotonin in the brain (Yokogoshi et al., 1998) and produces relaxation by increasing alpha wave activity in the brain (Adhikary et al., 2017). It has the ability to pass the blood-brain barrier and enhance the release of gammaaminobutyric acid, thereby controlling dopamine and serotonin secretion in the brain, resulting in brain relaxation and enhanced learning behavior (Kimura et al., 2007). Figure 2 shows the basic metabolic pathway of green tea and theanine. ...
Article
Theanine is a naturally occurring amino acid, including two forms: D-theanine and L-theanine. L-theanine is the most common nonprotein amino acid and is soluble in water. Theanine can be found in some plants, such as green tea and some mushrooms. Under stress conditions, theanine is proposed to be a naturally effective additive in preventing reactive oxygen species, thus reducing oxidative stress. In addition, as an immune booster in animal bodies, L-theanine can be applied in the diet to help animals improve their performance, especially their immunity during stress conditions. The digestion of L-theanine improves γδ T cell growth and development. Thus, it is considered an essential compound in boosting the immune function. Moreover, the immune function of L-theanine is also shown in immune-related organs through increasing their weights. Theanine seems to be widely used in pigs, mice, and humans. However, the study of theanine in poultry species is scarce. Therefore, to fill the knowledge gap regarding the use of theanine in enhancing poultry immunity, this study aims to synthesize all information on the application of theanine in poultry, focusing on its immune-boosting role.
... Theanine also provides relief of PMS symptoms, blood pressure regulation and enhancement of memory and concentration [9] . Kimura et.al (2007) showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress condition [10] . Bryan et al.(2008) suggests that caffeinated tea when ingested at regular intervals may maintain alertness, focused attention accuracy and may modulate the more acute effects of higher doses of caffeine [11] . ...
Article
Food and mood are regular consistent part of our lives and they inevitably get tangled up together. This review study aims to find out the physiochemical and biochemical relationships and the exact mechanism that binds food with mood. Results showed that caffeine improves vigilance, alertness, mood and cognitive processes during and after exercise. L-theanine a major component of tea, has anxiolytic and calming effect due to its up-regulation of inhibitory neurotransmitters and possible modulation of serotonin and dopamine in selected areas. Antidepressant-like effect of chocolate can most likely be attributed to the antioxidant potential of cocoa polyphenol which reduces hunger and elevates mood.n-3 PUFA present in fish oil exerts anti-depressant effect. Folic acid and Vitamin C is beneficial for the reduction of Childhood Depression.
... Randomize, doubleblind, placebocontrolled, crossover Williams et al. [46] No task stressor; high consumption of caco-content increase blood pressure. Montopoli et al. [45] the trials of acute single day intervention have been conducted; studies performed by Yoto et al. [25] and Kimura et al. [31] have shown that 200 mg/day of L-theanine manage to provide the anti-stress effect in the mental arithmetic task (Table 2). ...
Article
Tea (Camellia sinensis) is widely considered to promote feelings of calming and soothing. This effect is attributed to L-theanine (L-γ-glutamylethylamide) in tea, a non-protein amino acid mainly derived from tea leaves. As a naturally occurring structural analogue of glutamate, L-theanine competes for the receptors with glutamate and is able to pass the blood-brain barrier to exert its relaxation effect. This review focuses on the relaxation effect of L-theanine, including animal models and the latest human trials as well as the potential molecular mechanisms regarding neuron stem cells. The biological efficacy of dietary L-theanine in the food matrix has been further discussed in this review in relation to the physiological changes in the gastrointestinal tract and bindings of L-theanine with other food components.
... L-Theanine (γ-L-glutamylethylamide) is a nonproteinogenic amino acid occurring naturally in tea. Besides imparting the characteristic umami flavor to tea, L-theanine has various neurophysiological benefits on human health like regulating high blood pressure (Yokogoshi et al., 1995), improving cognition power (Haskell et al., 2008), reducing stress and promoting relaxation (Lu et al., 2004;Kimura et al., 2007), strengthening the immune system (Miyagawa et al., 2008), and enhancing antitumor activity (Sadzuka et al., 2000;Liu et al., 2009) and antiobesity effects (Zheng et al., 2004). ...
Article
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Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a variety of roles in diverse organisms. Higher eukaryotes mainly utilize GGT for glutathione degradation, and mammalian GGTs have implications in many physiological disorders also. GGTs from unicellular prokaryotes serve different physiological functions in Gram-positive and Gram-negative bacteria. In the present review, the physiological significance of bacterial GGTs has been discussed categorizing GGTs from Gram-negative bacteria like Escherichia coli as glutathione degraders and from pathogenic species like Helicobacter pylori as virulence factors. Gram-positive bacilli, however, are considered separately as poly-γ-glutamic acid (PGA) degraders. The structure–function relationship of the GGT is also discussed mainly focusing on the crystallization of bacterial GGTs along with functional characterization of conserved regions by site-directed mutagenesis that unravels molecular aspects of autoprocessing and catalysis. Only a few crystal structures have been deciphered so far. Further, different reports on heterologous expression of bacterial GGTs in E. coli and Bacillus subtilis as hosts have been presented in a table pointing toward the lack of fermentation studies for large-scale production. Physicochemical properties of bacterial GGTs have also been described, followed by a detailed discussion on various applications of bacterial GGTs in different biotechnological sectors. This review emphasizes the potential of bacterial GGTs as an industrial biocatalyst relevant to the current switch toward green chemistry.
... In human and murine models, L-theanine has been applied using various acute and chronic stress conditions [113]. L-Theanine elicits anti-stress effects by attenuating the activation of the sympathetic nervous system [114]. Serum corticosterone level was lowered in Ltheanine treated rats subjected to water immersion stress [115]. ...
Article
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Heat stress (HS) is an important environmental stress factor affecting poultry production on a global scale. With the rise in ambient temperature and increasing effects of global warming, it becomes pertinent to understand the effects of HS on poultry production and the strategies that can be adopted to mitigate its detrimental impacts on the performance, health, welfare, immunity, and survival of birds. Amino acids (AAs) have been increasingly adopted as nutritional modifiers in animals to ameliorate the adverse effects of HS. They are essential for protein synthesis, growth, maintenance, reproduction, immunity, stress response, and whole-body homeostasis. However, HS tends to adversely affect the availability, transport, absorption, and utilization of these AAs. Studies have investigated the provision of these AAs to poultry during HS conditions, and variable findings have been reported. Taurine, L-theanine, and L-citrulline are non-essential amino acids that are increasingly gaining attention as nutritional supplements in HS animals. Similarly, betaine is an amino acid derivative that possesses favorable biological properties which contributes to its role as a functional additive during HS. Of particular note, taurine is negligible in plants, while betaine, L-theanine, and L-citrulline can be found in selected plants. These nutrients are barely found in feed ingredients, but their supply has been shown to elicit important physiological roles including anti-stress effects, anti-oxidative, anti-inflammatory, gut promoting, and immunomodulatory functions. The present review provides information on the use of these nutritionally and physiologically beneficial nutrients as functional additives to poultry diets during HS conditions. Presently, although several studies have reported on the positive effects of these additives in human and murine studies, however, there is limited information regarding their utilization during heat stress in poultry nutrition. Therefore, this review aims to expound on the functional properties of these nutrients, their potentials for HS alleviation, and to stimulate further researches on their biological roles in poultry nutrition.
Article
L-theanine is used as an additive in food industry due to its unique health benefits to human being. Using γ-glutamyltranspeptidase (GGT) for L-theanine biosynthesis is one of the most effective methods. Fifty putative Bacillus strains were isolated from tea plant rhizosphere soil and could produce GGT but differed in GGT-producing activity. The capacity of forming L-theanine activity catalyzed by the GGTs from different strains was consistent with their activity of producing GGTs. Strain BSFT-42 was identified as Bacillus subtilis based on biochemical properties and 16S rDNA sequence alignment. The GGT produced by this strain had the highest L-theanine-forming activity. Under the optimized conditions, the GGT from the fermentation broth of strain BSFT-42 at 32 h could convert 87.45% of Gln to L-theanine and produced 17.49 mM of L-theanine. This study indicated the possibility to use GGT excreted by B. subtilis BSFT-42 for L-theanine production.
Article
The current study investigated the angiotensin-converting enzyme (ACE) inhibitory activity of 4 synthetic tripeptides. All the peptides showed enzyme inhibitory activity, especially two promising ones, TTP (Thea-Thea-Pro) and gAgAP (GABA-GABA-Pro), with IC50 values of 0.92 and 3.4⿿μmol/L, respectively. Enzyme inhibition kinetics determined by Lineweaver-Burk plots revealed that TTP and gAgAP were competitive inhibitors with Ki values of 0.87 and 3.12⿿μmol/L, respectively. Molecular docking experiments confirmed that the higher inhibitory potency of TTP and gAgAP might be attributed to the formation of several critical hydrogen bonds with the active site residues in ACE. We further demonstrated that TTP and gAgAP initiated a rapid and significant decrease in systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs). TTP treatment lowered SBP to the same extent as captopril, although the duration of anti-hypertensive effect was shorter in TTP group than that observed in captopril group. Moreover, the transcription levels of angiotensin II receptor type 1 (agtr1) and miR-132/-212 were downregulated in SHRs after administration of TTP and gAgAP. In particular, TTP treatment caused a comparable reduction of agtr1 levels compared to captopril treatment, while miR-132/212 expression were significantly decreased. These results showed that compound TTP might be served as a potential antihypertensive candidate.
Article
In this investigation, Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) together with its two transpeptidase-specialized mutants (N450D and N450Q) were employed for the biocatalytic synthesis of L-theanine. A high-pressure liquid chromatographic method coupled with ultraviolet detection (HPLC/UV) was used to quantify L-theanine content in the reaction mixture. Through a series of experiments, the perfect conditions for the biocatalytic synthesis were found to be an operational pH of 10.5, a reaction time of 4 h, L-glutamine and ethanolamine in a 1:2.4 M ratio, and enzymes at a working concentration of 25 μg/mL. In a batch process for N450D-mediated synthesis of L-theanine at 37 °C, a conversion rate of ~94% was achieved from 250 mM l-glutamine and 600 mM ethylamine. Successful synthesis of the desired product was further verified by mass spectrometry analysis. Conclusively, the experimental results suggest a high potential application in the production of L-theanine by BlGGT-mediated biocatalysis.
Article
L-Theanine Reduces Epileptiform Activity In Brain Slices ABSTRACT Objective: L-theanine is one of the main amino acid of tea plant which can cross the blood brain barrier. In the central nervous system, L-theanine has certain effects on a number of neurotransmitter systems. In this study we tested whether acute application of L-theanine could induce any seizure like or inhibitory activity in the brain slice. Materials and Methods: Effects of L-theanine on epileptiform activity were investigated in two different brain regions. Horizontal hippocampal-entorhinal cortex slices were obtained from 30-35 days old C57BL/6 mice. Extracellular field potentials were recorded from medial entorhinal cortex (EC) and CA3 region of hippocampus. Epileptiform activity was induced by application of 4 Aminopyridine (4AP, 100 µM) in the brain slices and 50 µM L-theanine was applied. From the recordings, the duration and frequencies of ictal like events as well as frequency and amplitude of inter-ictal like activities were calculated. Results: L-theanine alone did not initiate any synchronized activity. Although, bath application of L-theanine after 4AP induces epileptiform acitivities, did not significantly alter the duration and frequency of ictal discharges, L-theanine attenuated the interictal discharges. In EC the frequencies of interictal discharges were significantly decreased. In CA3, the amplitudes of interictal activities were significantly reduced. Conclusion: The present findings suggest that L-theanine do not induce any seizure like event but rather had a suppressive effect on ongoing epileptiform activity. Key Words: Theanine, 4 Aminopyridine, Brain Slice, Epileptiform activity, CA3, Entorhinal cortex
Article
Background The prospective studies on the effect of particular type of tea consumption, especially green tea, on depressive symptoms are limited. Objective The aim of this study is to investigate the prospective association between green tea consumption and depressive symptoms in a large general adult population. Methods This prospective cohort study investigated 7524 participants aged 25 to 90 years from May 2013 to December 2018 and they were free of cardiovascular disease, cancer, and depressive symptoms at baseline. Green tea consumption was obtained through a validated food frequency questionnaire. Depressive symptoms were assessed by using the Self-Rating Depressive Scale (SDS). The association between green tea consumption and depressive symptoms was analyzed by Cox proportional hazards regression models. Results A total of 1064 first incident cases of depressive symptoms (SDS ≥45) occurred during 14,661 person-years of follow-up (median follow-up of 2.0 years). In the crude model, the hazard ratios (95% confidence intervals) were 1.00 (reference), 0.95 (0.81, 1.12), 0.97 (0.83, 1.14) and 0.95 (0.79, 1.14), respectively. After adjusting for demographic characteristics, lifestyle factors, and dietary intake, the multivariable adjusted hazard ratios (95% confidence intervals) were 1.00 (reference), 0.88 (0.74, 1.05), 0.84 (0.69, 1.02) and 0.78 (0.63, 0.97), respectively. Conclusions The prospective study suggests that frequent green tea consumption is associated with a decreased risk of depressive symptoms in the general Chinese population.
Article
Gyokuro is a style of Japanese green tea produced by employing agricultural shading in the weeks before harvest. This method results in a tea product with different organoleptic and chemical properties than common Japanese green tea. In an effort to yield the highest quality and commercially valuable green tea product, the present study explores the influence of shading treatments and the duration of shading on the natural biochemistry of the green tea plant. This study applied shading treatments at light intensity conditions of 40%, 16%, 10% and 1% of available ambient light and the application of a red-colored shade cloth of 60% opacity. The Quality Index Tool was used to measure the quality and commercial value of the green tea, using individual target constituents (theanine, caffeine and the catechins) quantified from HPLC analysis. This study shows that very high levels of total visible spectrum light shading (~99%) is required to achieve improvements in quality and commercial value. Specifically, this improvement is a direct result of changes in the mood- modifying bioactive metabolites theanine and caffeine. This study concludes that in green tea growing regions with more hours of sunlight per year, such as on the Central Coast of Australia, more intense shading will achieve products with improved quality and commercial value, which has more potential to be marketed as a functional ingredient.
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This book covers all areas of agricultural sciences and other related fields. The contributions by the authors include tomatoes, genetic transformation, GUS gene, tea, Camellia sinensis, flower, honey, biopesticides, efficacy, food production, neem, pesticides, banana, postharvest life, green tea, Hausa potato, roots, hydroponics, leaf scald, smut, pokkah boeng, agro-ecology, erosion, soil conservation, abiotic stress, root system, Saccharum spp., Zucchini, attacked fruits, coastal forests, forest ecosystem, nitrogen load, nutrient etc. This book contains various materials suitable for students, researchers and academicians in the field of agricultural sciences.
Article
l -Theanine is a nonproteinogenic amino acid present almost exclusively in tea plants and is beneficial for human health. For industrial production, l -theanine is enzymatically or chemically synthesized from glutamine/glutamate (or a glutamine/glutamate derivative) and ethylamine. Ethylamine is extremely flammable and toxic, which complicates and increases the cost of operational procedures. To solve these problems, we developed an artificial biosynthetic pathway to produce l -theanine in the absence of supplemental ethylamine. For this purpose, we identified and selected the novel transaminase AAN70747 from Pseudomonas putida KT2440, which catalyzes the transamination of acetaldehyde to produce ethylamine, as well as γ-glutamylmethylamide synthetase AAY37316 from Pseudomonas syringae pv. syringae B728a, which catalyzes the condensation of l -glutamate and ethylamine to produce l -theanine. Expressing these genes in Escherichia coli W3110S3GK and enhancing the production capacity of acetaldehyde and l -alanine achieved successful production of l -theanine without ethylamine supplementation. Furthermore, the deletion of ggt , which encodes γ-glutamyltranspeptidase (EC 2.3.2.2), achieved large-scale production of l -theanine by attenuating its decomposition. We show that an alanine decarboxylase-utilizing pathway represents a promising route for the fermentative production of l -theanine. To our knowledge, this is the first report of efficient methods to produce l -theanine in the absence of supplemental ethylamine. IMPORTANCE l -Theanine is widely used in food additives and dietary supplements. Industrial production of l -theanine uses the toxic and highly flammable precursor ethylamine, raising production costs. Here we used Escherichia coli to engineer two biosynthetic pathways that produce l -theanine from glucose and ammonia in the absence of supplemental ethylamine. This study establishes a foundation for safely and economically producing l -theanine.
Conference Paper
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Autism is a neuropsychiatric disease; one of the causes of autism is damage to neurons. L-Theanine is a bioactive compound in Camellia sinensis L.which is analogous to L-Glutamate Acid structure and its neuroprotective effect. This study aimed to analyze the binding side of L-Theanine and L-Glutamate Acid to the kainate of glutamate receptor protein to determine and the effectiveness of its inhibitor function. Toxicity analysis is also used to determine the suitability of compounds as bioactive components to be consumed orally. The method used to analyze the interaction of compounds with target proteins is reverse docking. Toxicity analysis using the Toxtree 2.6.13 and collection of information from the Human Metabolome Database. The docking shows that L-Glutamate Acid and L-Theanine have the same site in the ionotropic Glutamate receptor protein, kainate1. The residual groups of the two compounds when binding to the similar glutamate receptor protein are THR (A: 91), GLU (A: 191), and ARG (A: 96). The binding affinity of the two compounds is almost the same, namely -5.0 kcal/mol for L-Glutamate Acid and -4.9 kcal/mol for L-Theanine. This allows L-Theanine to act as an inhibitor that blocks L-Glutamate Acid from binding to glutamate receptors on prostsynap membranes. The compound docking results show that L-Theanine has four bond side residues that are the same as the same L-Glutamate Acid and binding affinity of -5.0 kcal/mol. Analysis with the principle of RO5 Lipinski is known that L-Theanine compounds have the potential if taken orally. Therefore, the C. sinensis L. potential as an anti-autism substance.
Article
Polyphenols, a category of plant compounds that contain multiple phenol structural units, are widely distributed throughout the plant kingdom and have multiple benefits for human health including anti-obese, anti-hyperglycemic, and anti-hyperlipidemic effects. Additionally, polyphenols have recently gained attention for their anti-stress effects. In this review article, we summarize physiological responses against exposure to stressors and discuss biomarkers for exposure to stressors that are widely used in animal studies and human trials. We also review commonly used animal models for evaluating anti-stress effects. Finally, we discuss recent findings related to the anti-stress effects of polyphenols evaluated in animal models and human trials, and their putative mechanisms. These emerging data require further investigation in scientific studies and human trials to evaluate the anti-stress effects of polyphenols and their potential use for the prevention of stress-related health problems.
Article
L-Theanine, an active ingredient in the tea plant (Camellia sinensis) associated with calming, is widely used as a functional ingredient and dietary supplement. In this study, a heat stress mouse model was used to evaluate the anti-heat stress effect of L-theanine and its possible mechanism of action. Mice subjected to heat stress (40 °C) that were administered L-theanine at various doses (100, 200, and 400 mg kg-1 d-1) had reduced oxidative stress and inflammatory factors when L-theanine was administered both long-term and as a preventative treatment. Our L-theanine intervention countered the reduction in growth and feed intake of mice under heat stress and reversed liver and jejunum tissue damage. Moreover, L-theanine countered the increase in inflammatory factors TNF-α, IL-6, and IL-1β and antioxidant enzymes SOD and CAT; it also counteracted GSH-Px inactivation, the upregulation of AST and ALT enzyme activity, and MDA production. The mechanism of action may involve mediation of the P38 signaling pathway, inhibition of MK2 overexpression, and downregulation of p-P65/P65 caused by the overexpression of downstream HSP27. This would inhibit the heat stress-induced imbalance in oxidative stress and inflammatory responses.
Article
L-theanine, a unique amino acid in green tea with health benefits, can be enzymatically synthesized by γ-glutamyltranspeptidase (γ-GT; EC 2.3.2.2). Here, a salt-tolerant γ-glutamyltranspeptidase from a marine bacterium Bacillus amyloliquefaciens was expressed in Escherichia. coli BL21 (DE3) and was shown to be optimally active at 55 °C, pH 8.5 and alkali stable. A mutant, with higher transpeptidation activity, was obtained following two rounds of directed evolution using error-prone PCR and site-saturation mutagenesis. The mutation increased the ratio of transpeptidation to hydrolysis from 1.6 to 35.6. Additionally, Kinetic analysis exhibited 17.5% decrease of Km, 13.0-fold increase of Kcat, and 16.3-fold increase of Kcat/Km in mutant V319A/S437 G versus the wild-type. The 3-D modelling analysis revealed a tighter binding pocket in mutant V319A/S437 G. The frequency of hydrogen bond between donor substrate and two residues in the catalytic pocket (Gly437 and Thr375) was enhanced, which stabilized the ligand binding and thus improved the catalytic efficiency. The optimal conditions for the biocatalytic synthesis were determined as pH 10.0, 20 μg mL⁻¹ BaGT, 200 mM L-glutamine, 2 M ethylamine, and a reaction time of 5 h. The V319A/S437 G mutant was shown to increase the percentage yield of L-theanine from 58% to 83%. These results indicate the great potential of V319A/S437 G in L-theanine production after further study.
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L-theanine (γ-Glutamylethylamide) is a non-protein water soluble amino acid (AA) mostly occurred in leaves of Camellia sinensis (green tea). This is a key component of green tea, and is considered as the most abundant form of total amino acids in green tea (i.e. about 50%). L-theanine is an exclusive taste ingredient of tea producing an attractive flavor and aroma in tea. It has worth notice biological effects like antioxidant, growth promoter, immune booster, anti-stresser, hepactoprotective, antitumor, anti-aging, antimicrobial, anti-inflammatory and anti-anxiety activities. It could reduce the oxidative impairment by reducing the synthesis of reactive oxygen species (ROS), oxidative parameters and lipid damage as well as increasing the activity of antioxidant enzymes. The oral ingestion of L-theanine enhanced γδ T-cell proliferation. Therefore, it is being considered an essential compound of green tea’ that has ability to improve immune function. The L-theanine can be used as a potential treatment for hepatic injury and immune-related liver diseases via the downregulation of the inflammatory response through the initiation of nitric oxide (NO) synthesis and glutathione (GSH) production are likely to be critical for the control of hepatic diseases as well as for the improvement of immune function. In addition it could be used as a best natural feed additive with potent anti-stressor via decreasing the levels of corticosterone (CORT), dopamine (DA) and noradrenaline (NA). After systematically reviewed the literature it is noticed that, mostly studies done on mice, pig, human and butterfly; while dietary supplementation studies of L-theanine in animal and poultry especially among broilers is very limited due to less awareness of this amino acid. So, the aim of this review is to encourage the veterinarian and poultry researchers to conduct more research at the molecular level about this amino acid to expose its’ more beneficial effects and its’ mechanism of absorption for potential use of this unique green tea amino acid in poultry nutrition.
Article
Tea is the most consumed beverage worldwide, and l-theanine in tea leaves significantly affects their flavor and market quality. We have developed and validated a fast and reliable gas chromatographic method with flame ionization detection (GC-FID) to quantify l-theanine after its extraction from Camellia sinensis (tea plant) and derivatization. The procedure was completed in 40 min, from extraction to chromatographic analysis, with a recovery rate of more than 93% and allowing a high sample throughput. The GC-FID intraday precision was within 0.57-2.28%, while the interday precision ranged from 1.57 to 13.48%. The intraday accuracy ranged from -6.84 to 5.26%, while the interday accuracy ranged from -1.08 to 3.12%. The limit of detection was 2.28 μg/mL, and the limit of quantification was 6.47 μg/mL. The GC-FID method was validated by high-performance liquid chromatography with UV detection (HPLC-UV) and was used to investigate the biosynthesis and regulation of l-theanine in tea plants. We found that plants fed with ethylamine significantly increased l-theanine concentrations in roots, while exogenous supplementation of glutamic acid, carbamide, and glutamine did not significantly affect the l-theanine level in roots. Our results also indicated that roots were not indispensable for the biosynthesis of l-theanine, which was detected in undifferentiated embryonic calluses in concentrations (g/100 g dry weight) as high as in leaves of whole plants (1.67 and 1.57%, respectively) and without any exogenous theanine precursor supplementation.
Article
Tea is the second most consumed beverage around the world after water. Apart from other tea preparations, approximately 98% of peoples drink tea with milk. The essential bioactive component, i.e., L-theanine present in tea along with catechins, tannin, and polyphenols, which has prominent health benefits, including relaxation. L-theanine is proteionic amino acid present only in tea, and which is safe for daily intake. This review focused on L-theanine present in different types of tea, commercially available tea powders, extraction methods for L-theanine isolation, characterization, and health benefits of L-theanine.
Article
Prostate cancer (PCa) is a very prevalent male-specific malignancy; most PCa patients eventually die as a result of metastasis. L-theanine (C7H14N2O3), a nonprotein amino acid derivative from green tea leaves, has been demonstrated to act as an anticarcinogen through proapoptotic and antiproliferative effects. However, the antimetastatic effect of L-theanine in tumor cells and its underlying mechanism are still unclear. Here, we found that L-theanine could suppress invasion, migration, and increase cell-cell adhesion of prostate cancer cells in vitro and in vivo. We also found that L-theanine could inhibit the epithelial-mesenchymal transition process in PCa. Our study revealed that L-theanine could downregulate MMP9, N-cadherin, Vimentin, Snail, and upregulate E-cadherin. Furthermore, L-theanine suppressed the transcription of MMP9 and Snail by significantly inhibiting the ERK/NF-κB signaling pathway and the binding activity of p65 to the promoter regions of MMP9 and Snail. All of these findings suggest that L-theanine has therapeutic potential for metastatic PCa and may be considered a promising candidate for antimetastatic therapy of prostate cancer.
Article
Background: Exposure to stressful experiences is often accompanied by suppressing pain perception, referred to as stress-induced analgesia. The neuropeptides orexins are essential in regulating the mechanism that responds to stressful and painful stimuli. Meanwhile, the ventral tegmental area (VTA), as a part of descending pain inhibitory system, responds to noxious stimuli. The present study aimed to investigate the role of intra-VTA administration of orexin receptor antagonists on stress-induced antinociceptive responses in the animal model of acute pain. Method: Ninety-three adult Wistar rats weighing 230-250 g were unilaterally implanted by a cannulae above the VTA. Animals were pretreated with different doses (1, 3, 10, and 30 nM/0.3 μl) of SB334867 as the orexin-1 receptor antagonist and TCS OX2 29 as the orexin-2 receptor antagonist into the VTA, just 5 min before 6 min exposure to forced swim stress (FSS). Nociceptive threshold was measured using the tail-flick test as a model of acute pain. Results: The results showed that exposure to FSS could significantly increase analgesic responses. Moreover, intra-VTA administration of SB334768 and TCS OX2 29 blocked the antinociceptive effect of FSS in the tail-flick test. Conclusion: The findings suggest that OX1 and OX2 receptors in the VTA might modulate the antinociceptive behaviors induced by FSS in part.
Chapter
In recent decades, preclinical research into natural products has focused on the identification of pharmacologically active secondary metabolites produced by plants, often traditionally used as medicinal remedies. Beyond vitamins and minerals, plants contain other secondary metabolites recently defined as “nutraceuticals,” which are at the center of important scientific studies. The term nutraceutical is a portmanteau word, a combination of “nutrition” and “pharmaceutical,” and refers to “naturally derived bioactive compounds that are found in foods, dietary supplements, and herbal products and have health-promoting, disease-preventing, and/or medicinal properties.” Several nutraceuticals exhibit antiaging features by acting on the inflammatory status and on the prevention of oxidative reaction. This results in a significant reduction of all risk factors for age-related diseases, enhancing the attainment of healthy aging. In this context, the chapter will summarize the available clinical evidence supporting the use of selected botanicals and phytochemicals with confirmed activity on the human central nervous system and demonstrated effects in modulating cognitive decline as an example of age-related disease. In particular, the chapter will focus on data supporting the potential usefulness of Ginkgo biloba, Vitis vinifera, Camellia sinensis, Theobroma cacao, Bacopa monnieri, Crocus sativus, and Curcuma longa.
Chapter
Adaptogens are agents which protect against stress and stress-related disorders. They act in a nonspecific manner and rejuvenate the body systems in a holistic manner by complex and interactive mechanisms. The ability to cope with the stressful experience maintains the physiological homeostasis and the lack of such adaptive mechanisms results in pathophysiological states, which can involve cardiovascular organs, the immunological system, neuroendocrinal axis, gastrointestinal system, central nervous system, etc. Conventional antistress agents used for such conditions, while being effective, have a plethora of undesirable effects which limit their long-term use, and thus there is a constant search for more effective and safer agents. Nutraceuticals are food additives and/or nutritional supplements used for the prevention and treatment of many diseases as well as for maintenance of normal wellbeing. Some such nutraceuticals with adaptogenic potential are primarily obtained from herbal sources (medicinal plants), and, in recent years, have gained considerable attention because of their safety, efficacy, and cost-effectiveness. Experimental and clinical studies have validated their uses in a plethora of human diseases and scientific research has clarified their efficacy and safety issues. In addition, several dietary supplements which provide potential adaptogenic molecules after chemical transformation in the body are also being increasingly recommended for stress and stress-related conditions. With the evolving scenario, and increasing general awareness about health and disease, the use of such nutraceuticals may revolutionize the management of some of these excruciating and debilitating disease states. Such adaptogens, in view of their holistic effectiveness and well known safety, could not only help to counteract stress effects on the biological system but also increase nonspecific resistance to a variety of threatening/aversive conditions. The outcome could be attenuation of stress-related disorders and improvement of the quality of life.
Article
Tea (Camelliasinensis) is the world’s most widely consumed non-alcoholic beverage with essential economic and health benefits since it is an excellent source of polyphenols, catechins, amino acids, flavonoids, carotenoids, vitamins, and polysaccharides. The aim of this review is to summarize the main secondary metabolites in tea plants, and the content and distribution of these compounds in six different types of tea and different organs of tea plant were further investigated. The application of these secondary metabolites on food processing, cosmetics industry, and pharmaceutical industry was reviewed in this study. With the rapid advancements in biotechnology and sequencing technology, omics analyses, including genome, transcriptome, and metabolome, were widely used to detect the main secondary metabolites and their molecular regulatory mechanisms in tea plants. Numerous functional genes and regulatory factors have been discovered, studied, and applied to improve tea plants. Research advances, including secondary metabolites, applications, omics research, and functional gene mining, are comprehensively reviewed here. Further exploration and application trends are briefly described. This review provides a reference for basic and applied research on tea plants.
Article
In an investigation of the mechanisms of the neuroprotective effects of theanine (gamma-glutamylethylamide) in brain ischemia, inhibition by theanine of the binding of [H-3](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), [H-3]kainate, and [H-3](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.
Article
L-Theanine is an amino acid found in green tea leaf and in its infusion, and is known to control excitement caused by caffeine. It is also known that the oral administration of L-theanine to rats results in a decrease of serotonin and increase of catecholamines in their brain. L-Theanine has been confirmed to be safe in animal experiments. We found recently that oral intake of L-theanine caused a feeling of relaxation among the human volunteers examined. These observations led us to do experiments on the effects of administration of L-theanine on the brain electric waves. Eight female university students were selected as volunteers. Four of them were ranked to be Grade I (the highest anxiety) and the remaining four, Grade V (the lowest anxiety) in an investigation done by the manifest anxiety scale method. A dose of oral administration of 200 mg of L-theanine dissolved in 100 ml of water resulted in the generation of α-electric waves in the occipital and parietal regions of the brains of the subjects. The emission intensity of α-brain waves (integrated as a function of investigation times and area) was significantly greater in the group of Grade I than that of Grade V. These results indicate the possibility for L-theanine to be applied to foods and beverages as a new type of functional food ingredient for its relaxation effect.
Article
— Glucocorticoids and stress have deleterious effects on hippocampal cell morphology and survival. It has been hypothesized that these effects are mediated via an excitatory amino acid mechanism. The present study was designed to evaluate the effects of acute stress on the extracellular levels of glutamate in the hippocampus and to determine if adrenalectomy modifies this response. Rats were adrenalectomized or sham-adrenalectomized and implanted with microdialysis probes in the CAS region of the hippocampus. Three days later rats were subjected to an acute 1 -h period of immobilization stress. Stress significantly increased extracellular glutamate levels in the sham-operated rats, which peaked at 20 min following the initiation of stress. Extracellular glutamate levels also increased immediately following the termination of stress. In the adrenalectomized rats there was a 30% decrease in basal extracellular concentrations of glutamate and a marked attenuation (-70%) of the stress-induced increase in extracellular glutamate levels. Extracellular concentrations of taurine were not modified by adrenalectomy and did not change in response to stress. These results suggest that glucocorticoid-in-duced elevations in extracellular glutamate concentrations may contribute to the deleterious effects of stress on hippocampal neurons.
Article
This study examined the acute immunological effects of two laboratory stressors, expected to evoke distinct patterns of cardiac autonomic activity; namely an “active coping” time-paced memory test, and a “passive coping” stressful video showing surgical operations. We measured salivary S-IgA, IgA-subclasses (IgA1, IgA2), and secretory component (SC). SC is responsible for the transport of S-IgA across the epithelium, and thus a rate-determining step in S-IgA secretion. Thirty-two male undergraduates were subjected to both stressors and a control video (a didactic television program). The memory test induced a typical “fight-flight” response, characterized by increases in heart rate and blood pressure in association with a decrease in cardiac preejection period (PEP) and vagal tone. The surgical video produced a “conservation-withdrawal”-like response, characterized by an enhanced vagal tone, a decrease in heart rate, and a moderate sympathetic coactivation (as indicated by a shortened PEP and an increased systolic pressure). The memory test induced an increase in the concentration and, to a lesser extent, in the output of S-IgA, IgA1, and SC. The output of IgA2 was not significantly affected. For the surgical video, a different pattern emerged: During stressor exposure S-IgA remained unaffected, against the background of a small increase in SC output. However, 10 min after the surgical video S-IgA levels had decreased. This decrease in S-IgA was paralleled by a decrease in IgA1, but not IgA2. We conclude that acute stress can have both enhancing and suppressive effects on secretory immunity, the IgA1 subclass in particular. The mechanisms that underlie these divergent responses may include stressor-specific patterns of autonomic activation.
Article
To evaluate effects of acute mental stress on aspects of cellular immunity, lymphocyte populations and phytohemagglutinin (PHA)-stimulated T-cell mitogenesis were measured in 33 healthy young men, both before and immediately following subjects' performance of a frustrating, 21-minute laboratory task (Stroop test). Relative to baseline evaluations, post-task measurements showed a significant reduction in mitogenesis and alterations in various circulating lymphocyte populations; the latter included a diminished T-helper/T-suppressor cell ratio and an elevation in the number of natural killer cells. Eleven subjects assigned to a control (unstressed) condition exhibited no changes in lymphocyte populations, but did show an increase in T-cell proliferation, compared with pretask measurements.
Article
The effect of green tea polyphenol fraction (GTP) on azoxymethane(AOM)-induced colon carcinogenesis was investigated in male Fischer rats. The rats were given AOM (7.4 mg/kg body weight) s.c. once a week for 10 weeks. A week after the treatment, they were divided into three groups: AOM-control (26 rats), AOM-GTP1 (26 rats) and AOM-GTP2 (25 rats). AOM-GTP1 and AOM-GTP2 groups respectively received 0.01 and 0.1% GTP in drinking water from week 11 to 26. AOM-control group received tap water throughout this experiment. Autopsy on week 26 showed that tumor incidence and average numbers of tumors per rat in the AOM-GTP1 and AOM-GTP2 groups were significantly lower than those of the AOM-control group: 38.1% and 47.6% versus 77.3%; 0.6 and 0.7 versus 1.5. Thus, it was concluded that GTP inhibited the development of AOM-induced colon carcinogenesis. The inhibition by GTP did not show significant dose dependence.
Article
The effects of i.p. administered theanine (L-N-ethylglutamine), a constituent of Japanese green tea, on the levels of norepinephrine (NE) and serotonin (5-HT) in the brain of rats with or without coadministration of caffeine were investigated, and compared with those of glutamine.Theanine decreased the NE level, whereas no change was observed with glutamine or caffeine.The decrease of NE induced by theanine was reversed by caffeine. In rats pretreated with pargline, a monoamine oxidase inhibitor, theanine significantly increased the NE level compared with the control. However, it did not enhance the NE levels increased by caffeine. Thus, theanine may decrease the NE levels by releasing this neurotransmitter.Theanine did not alter the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in rats pretreated with or without pargyline, indicating that this amide affects neither 5-HT synthesis nor its degradation. Caffeine increased the levels of 5-HT and 5-HIAA in normal rats to similar extents.This effect was depressed by theanine. In rats pretreated with pargyline, the levels of 5-HT and 5-HIAA were not altered by caffeine, and theanine did not modify the outcome. It may be concluded that the action of theanine is related to the possible inhibition of 5-HT release by caffeine. The effect of glutamine on the levels of 5-HT was somewhat different form that of theanine.
Article
The effect of theanine, one of the components of green tea, on the blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) was investigated by intraperitoneally administering theanine. The effect of glutamine, which is structurally similar to theanine, was also examined. When SHR were injected with various amounts of theanine (0, 500, 1000, 1500, and 2000 mg/kg), the change was dose-dependent, and a significant decrease in blood pressure was observed with the high doses (1500 and 2000 mg/kg). A dose of 2000 mg/kg of theanine did not alter the blood pressure of WKY, while the same dose to SHR decreased it significantly. On the other hand, glutamine administration to SHR did not change either the blood pressure or the heart rate. The brain 5-hydroxyindole level was significantly decreased by theanine administration to both WKY and SHR, the decrease being dose-dependent.
Article
Glucocorticoids and stress have deleterious effects on hippocampal cell morphology and survival. It has been hypothesized that these effects are mediated via an excitatory amino acid mechanism. The present study was designed to evaluate the effects of acute stress on the extracellular levels of glutamate in the hippocampus and to determine if adrenalectomy modifies this response. Rats were adrenalectomized or sham-adrenalectomized and implanted with microdialysis probes in the CA3 region of the hippocampus. Three days later rats were subjected to an acute 1-h period of immobilization stress. Stress significantly increased extracellular glutamate levels in the sham-operated rats, which peaked at 20 min following the initiation of stress. Extracellular glutamate levels also increased immediately following the termination of stress. In the adrenalectomized rats there was a 30% decrease in basal extracellular concentrations of glutamate and a marked attenuation (-70%) of the stress-induced increase in extracellular glutamate levels. Extracellular concentrations of taurine were not modified by adrenalectomy and did not change in response to stress. These results suggest that glucocorticoid-induced elevations in extracellular glutamate concentrations may contribute to the deleterious effects of stress on hippocampal neurons.
Article
This study evaluated the temporal nature of cellular immune responses, as well as the effects of cardiovascular reactivity on immune responses after exposure to an acute psychological stressor. Lymphocyte subsets and lymphocyte proliferative response to phytohemagglutinin were assessed at baseline and at 5 and 21 minutes after stressor onset in the experimental group and at the same time points in a nonstressor control group. By 5 minutes after stressor onset, the number of CD8 suppressor/cytotoxic T and CD16/56 natural killer cells increased and proliferative response to phytohemagglutinin decreased. These changes were maintained at 21 minutes. Those subjects showing the greatest cardiovascular reactivity had the largest immune alterations. These data did not indicate that gender significantly moderated immune responses. Results are consistent with the hypothesis that sympathetic activation mediates stressor-induced quantitative alterations of peripheral blood lymphocyte subpopulations and nonspecific mitogen stimulated proliferation.
Article
The technique of intracerebral microdialysis was used to assess the effect of stress on the extracellular concentrations of excitatory amino acids, glutamate and aspartate, in the rat medial prefrontal cortex, hippocampus, striatum, and nucleus accumbens. A 20-min restraint procedure led to an increase in extracellular glutamate in all regions tested. The increase in glutamate levels was significantly higher in the prefrontal cortex than that observed in other regions. With the exception of the striatum, extracellular levels of aspartate were increased in all regions. Furthermore, the increase in aspartate levels was significantly higher in prefrontal cortex compared to hippocampus and nucleus accumbens. Local perfusion of tetrodotoxin during the restraint procedure significantly decreased the stress-induced increase in extracellular excitatory amino acids. In order to ensure that the above results were not an artifact of restraint not associated with stress (e.g., decreased mobility), we also examined the effect of swimming stress on the extracellular levels of excitatory amino acids in selected regions, i.e., striatum and medial prefrontal cortex. Both regions displayed a significant increase in extracellular levels of aspartate and glutamate following 20 min of swimming in room temperature water. This study provides direct evidence that stress increases the neuronal release of excitatory amino acids in a regionally selective manner. The implications of the present findings for stress-induced catecholamine release and/or hippocampal degeneration are discussed.
Article
Secretory immunoglobulin A (sIgA) in saliva and cardiovascular reactions to mental arithmetic and cold pressor tasks were recorded in 16 healthy young men on two sessions, 4 weeks apart. Both tasks elicited significant increases in sIgA secretion rate, reflecting increases in both salivary volume and sIgA concentration. Whereas mental arithmetic elicited a mixed pattern of alpha- and beta-adrenergic cardiovascular reactions, the pattern of reactions to cold pressor was predominantly alpha-adrenergic. Task levels of sIgA secretion rate, sIgA concentration, and saliva volume showed moderate to high test-retest reliability (r = .52-.83), although test-retest correlations were less impressive for change scores (r = -.19-.53). The pattern of correlations between change in sIgA secretion rate and cardiovascular reactivity variables was inconsistent.
Article
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.
Article
The present research investigated the effects of controlled experimental manipulations of stress on biological and psychological reactions. Fifty young adult male volunteers were exposed to a 12-min period of stress induced by the threat of an unavoidable, painful electric shock. A 12-min period without this threat preceded or followed the stress period. Blood was drawn during the 4th and the 12th minute of each period. Anticipatory threat led to significant elevations in the proportions and cytotoxic activity of natural killer (NK) lymphocytes, plasma epinephrine levels, pulse rate, and reported level of tension, and to a reduction in the CD4/CD8 ratios. The no-threat period induced a return to baseline values for epinephrine, pulse rate, and tension, and lower than baseline levels for cytotoxic activity of NK lymphocytes, within a similarly short time span. The findings underline the rapidity with which physiological changes may transpire in the course of a brief and acute period of psychological stress, and the rapidity of their reversal upon relief from the stressor.
Article
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.
Article
Time-dependent changes of theanine (gamma-glutamylethylamide) and other amino acids in various tissues of rats were investigated during the 24 hrs after theanine administration. When theanine (4 g/kg of body weight) was intragastrically administered to rats, the concentrations of theanine in the serum, liver and brain were significantly increased 1 hr after its administration, and thereafter gradually decreased, but reached the maximum level in the brain after 5 hrs. Theanine in these tissues had completely disappeared 24 hrs after its administration. In contrast, the administration of theanine resulted in the concentrations of theanine, urea, ethylamine and glutamic acid in the urine being significantly enhanced. These results suggest that theanine might be degraded via glutamic acid.
Article
We investigated the influence of sympathetic nervous system processes on mucosal immunity by comparing the effects of beta-adrenoceptor blockade with 40 mg propranolol and placebo on secretory immunoglobulin A (sIgA) at rest and during paced serial arithmetic, cold pressor, and submaximal cycling. These tasks produced patterns of cardiovascular activity indicative of combined alpha- and beta-adrenergic, alpha-adrenergic, and beta-adrenergic activation, respectively. The effectiveness of the beta blockade was confirmed by the attenuation under propranolol of the shortening of the cardiac preejection period and the tachycardia elicited by mental arithmetic and exercise. The cold pressor test did not affect sIgA under either the placebo or the propranolol. Mental arithmetic increased sIgA concentration, and this increase was not blocked by propranolol. Exercise elicited increases in both sIgA concentration and sIgA secretion rate, which were not diminished by beta blockade. These data suggest that sIgA is not regulated by beta-adrenergic mechanisms.
Article
Secretory immunoglobulin A (sIgA) in saliva and cardiovascular activity were measured at rest and during mental arithmetic. Task difficulty was manipulated by presenting easy, hard, and impossible versions of the mental arithmetic task in counterbalanced order, while task novelty was operationalised as order of presentation (i.e. first, second, third). Mental arithmetic elicited significant increases in sIgA concentration and sIgA secretion rate, as well as significant cardiovascular effects. Performance decreased and rated difficulty increased with increasing task difficulty. However, sIgA and cardiovascular activity, with the exception of diastolic blood pressure, were insensitive to variations in task difficulty. In contrast, sIgA concentration and a broad range of cardiovascular variables were influenced by task novelty, with more pronounced activity characterising the task version presented first, irrespective of its level of difficulty. Task novelty would seem to be a more important determinant of sIgA and cardiovascular activity than task difficulty.
Article
In this study, the inhibiting action of theanine on the excitation by caffeine at the concentration regularly associated with drinking tea was investigated using electroencephalography (EEG) in rats. First, the stimulatory action by caffeine i.v. administration at a level higher than 5 micromol/kg (0.970 mg/kg) b.w. was shown by means of brain wave analysis, and this level was suggested as the minimum dose of caffeine as a stimulant. Next, the stimulatory effects of caffeine were inhibited by an i.v. administration of theanine at a level higher than 5 micromol/kg (0.781 mg/kg) b.w., and the results suggested that theanine has an antagonistic effect on caffeine's stimulatory action at an almost equivalent molar concentration. On the other hand, the excitatory effects were shown in the rat i.v. administered 1 and 2 micromol/kg (0.174 and 0.348 mg/kg) b.w. of theanine alone. These results suggested two effects of theanine, depending on its concentration.
Article
Salivary secretion of proteins from rat submandibular glands was studied using graded stimulation of the parasympathetic nerve in isolation, and then at a fixed rate in combination with graded sympathetic nerve stimulation. Increasing the frequency of parasympathetic nerve stimulation per se caused a gradual increase in the secretion of peroxidase (from acini) but only small increases in proteinase (from ductal cells) and IgA outputs. Dual stimulations, with an increasing frequency of sympathetic nerve stimulation on a background of low frequency parasympathetic nerve stimulation, showed that maximal acinar secretion of peroxidase required only a low frequency of additional sympathetic stimulation, whereas ductal secretion of kallikrein was greatest with the highest frequency of additional sympathetic stimulation (20 Hz in bursts). IgA secretion also required high frequency additional sympathetic stimulation in bursts for greatest output. Although a synergism occurred with parasympathetic plus sympathetic nerve stimulation for the secretion of both peroxidase and kallikrein it was not evident for the secretion of IgA. This presumably reflects a difference for exocytosis of proteins stored in granules (e.g. peroxidase and kallikrein) compared to those proteins continuously transported across the plasma membrane in vesicles by transcytosis. This work confirms that vesicular movement of secretory IgA can be increased by both parasympathetic and sympathetic nerve stimulation, but the frequency parameters differ for each nerve.
Article
The mechanism underlying acute changes in secretory immunoglobulin A (sIgA) remains to be determined. In this experiment, sIgA and cardiovascular activity were monitored at rest and while participants performed a mental arithmetic task, cold pressor, and submaximal cycle exercise following placebo or 1 mg of the alpha-adrenergic blocker, doxazosin. Under placebo, the tasks produced patterns of cardiovascular activity indicative of combined alpha- and beta-adrenergic, alpha-adrenergic, and beta-adrenergic activation, respectively. Doxazosin was associated with reduced blood pressure during cold pressor, but not during arithmetic or exercise. Mental arithmetic elicited increases in sIgA concentration and exercise produced increases in both sIgA concentration and secretion rate; these changes were unaffected by alpha blockade. In contrast, the cold pressor was associated with decreases in both sIgA concentration and secretion rate, which were blocked by doxazosin. These data suggest that acute decreases, but not increases, in sIgA are mediated by alpha-adrenergic mechanisms.
Article
This study examined the acute immunological effects of two laboratory stressors, expected to evoke distinct patterns of cardiac autonomic activity; namely an "active coping" time-paced memory test, and a "passive coping" stressful video showing surgical operations. We measured salivary S-IgA, IgA-subclasses (IgA1, IgA2), and secretory component (SC). SC is responsible for the transport of S-IgA across the epithelium, and thus a rate-determining step in S-IgA secretion. Thirty-two male undergraduates were subjected to both stressors and a control video (a didactic television program). The memory test induced a typical "fight-flight" response, characterized by increases in heart rate and blood pressure in association with a decrease in cardiac preejection period (PEP) and vagal tone. The surgical video produced a "conservation-withdrawal"-like response, characterized by an enhanced vagal tone, a decrease in heart rate, and a moderate sympathetic coactivation (as indicated by a shortened PEP and an increased systolic pressure). The memory test induced an increase in the concentration and, to a lesser extent, in the output of S-IgA, IgA], and SC. The output of IgA2 was not significantly affected. For the surgical video, a different pattern emerged: During stressor exposure S-IgA remained unaffected, against the background of a small increase in SC output. However, 10 min after the surgical video S-IgA levels had decreased. This decrease in S-IgA was paralleled by a decrease in IgA1, but not IgA2. We conclude that acute stress can have both enhancing and suppressive effects on secretory immunity, the IgA1 subclass in particular. The mechanisms that underlie these divergent responses may include stressor-specific patterns of autonomic activation.
Article
Very little is known about the effects of acute psychological stress on the production of reactive oxygen species (ROS) by human phagocytic cells and the interplay between subjectively perceived stress, mediating hormones, variations in the number of peripheral leukocytes and ROS production. We measured psychological reactions, cardiovascular parameters, plasma catecholamines, plasma prolactin and cortisol as well as peripheral lymphocyte subsets in 13 experimental subjects undergoing a brief psychological stressor, and production of ROS, as indicated by chemiluminescence (CL), in stressed subjects and in healthy controls. The stressor elevated anger (p<0.01) and cardiovascular activation (p<0.01). There were significant changes in plasma levels of cortisol (p<0.01) and prolactin (p<0.001). During psychological stress natural killer (NK) cells (p<0.01) and CD8/CD38 cells (p<0.05) increased and returned to baseline only 25 minutes later. Significant changes in the number of naive CD4+/CD45RA+ (p<0.01) and antigen-experienced CD8+/CD45RO+ T cells (p<0.05) occurred. Subjects with stronger cardiovascular reaction showed higher stress-related plasma levels of norepinephrine (p<0.05) and were mainly responsible for the increase in NK cells. We observed a significantly reduced production of ROS following the stress test (p<0.05). Our results show that psychological stress is expressed simultaneously on psychological, hormonal and immunological levels of the organism. We show the existence of a circadian rhythm leading to a pronounced increase in CL during the morning hours. This first study taking this circadian rhythm in account revealed a significant suppressive effect of stress on ROS production.
Article
To examine gender differences in immune reactions to stress and relationships between immune and cardiovascular reactivity, measures of cellular and mucosal immunity and cardiovascular activity were recorded in 77 men and 78 women at rest and in response to active (mental arithmetic) and passive (cold pressor) stress tasks. Both tasks reduced CD4+ T cells and the CD4/8 ratio. Total lymphocytes, NK cells, CD8+ T cells, and secretory immunoglobulin A (sIgA) increased with active stress. Passive stress decreased sIgA. At rest, men had more NK cells, less CD4+ T cells, and fewer neutrophils than women. Mental stress increased sIgA in men but not women. Cardiovascular reactivity to active stress was associated with increases in NK cells. The data support the hypothesis that stress-related increases in lymphocytes are beta-adrenergically mediated, and suggest that the fall in CD4+ T cells may be alpha-adrenergically driven. Mechanisms underlying sIgA reactions are more difficult to determine. Men and women differed in some cell counts, but not in reactivity, although gender influenced sIgA reactions to arithmetic.
Article
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.
Article
Most infections begin at mucosal surfaces. These surfaces are covered by the secretory proteins of the exocrine glands (eg, the salivary, respiratory, and gastrointestinal glands), which provide a first line of innate defense. The release of these secretory proteins is under neuroendocrine control and thus, in theory, sensitive to modulation by psychosocial stress. This was empirically tested by measuring the salivary secretion of cystatin S, lactoferrin, alpha-amylase, the mucins MUC5B and MUC7, and total salivary protein in response to stressors known to evoke distinct patterns of cardiac autonomic activity. Thirty-two undergraduate volunteers were each subjected to two laboratory stressors and a control condition. Stressors were an active coping memory test and a passive coping video presentation showing surgical procedures. In the control condition participants viewed a didactic video presentation. The stressors evoked the expected distinct patterns of cardiac autonomic activity. The memory test produced a strong increase in sympathetic activity (evidenced by a shortened preejection period), and a decrease in cardiac parasympathetic activity (evidenced by a decrease in heart rate variability). This active coping response was associated with an enhanced secretion ( microg/min, controlling for salivary flow rate) of MUC7, lactoferrin, alpha-amylase, and total salivary protein. Conversely, the surgical video produced an increase in cardiac vagal tone and a modest increase in sympathetic activity. This passive coping response was associated with an enhanced secretion of all proteins studied. These secretory responses were generally larger than the secretory responses during the active coping memory test. Correlation analyses indicated that for both stressors autonomic and cardiovascular reactivity was positively associated with an enhanced and prolonged secretory activity. Stress-induced modulation of innate secretory immunity may be a contributing factor in the observed relationship between stress and susceptibility to infectious diseases. We further propose a more differentiated approach to acute stress by distinguishing among stressors with distinct autonomic nervous system effects.
Article
This study clarified associations among immune, autonomic, and endocrine activities during mental arithmetic and cold pressor stress tasks in 26 women in the follicular phase. Both tasks decreased CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas they increased lymphocytes, granulocytes, NK cells, and NK cell activity (NKCA). The mental arithmetic task had a greater impact than the cold pressor task on changes in CD3+ T cells and in NK cells. Cardiovascular reactivity to active stress was associated with increased NK cells and decreased CD3+ T cells. Reduced cortisol levels during passive stress were associated with decreased CD19+ B cells and with increased NK cells. The merits of this study are that it controlled the following factors. Perceived stress during the two tasks was matched; both tasks lasted long enough to elicit high-magnitude responses; and the length of the intervening rest period minimized probable carryover effects between tasks.
Article
We investigated the molecular mechanism underlying the neuroprotective effect of theanine, a green tea component, using primary cultured rat cortical neurons, focusing on group I metabotropic glutamate receptors (mGluRs). Theanine and a group I mGluR agonist, DHPG, inhibited the delayed death of neurons caused by brief exposure to glutamate, and this effect of theanine was abolished by group I mGluR antagonists. Although the administration of glutamate alone decreased the neuronal expression of phospholipase C (PLC)-beta1 and -gamma1, which are linked to group I mGluRs, their expression was equal to the control levels on cotreatment with theanine. Treatment with theanine or DHPG alone for 5-7 days resulted in increased expression of PLC-beta1 and -gamma1, and the action of theanine was completely abolished by group I mGluR antagonists. These findings indicate that group I mGluRs might be involved in neuroprotective effect of theanine by increasing the expression levels of PLC-beta1 and -gamma1.
Article
Sympathetic nervous activity plays a prominent role in acute stress responses in the immune system, enhancement of innate immunity and suppression of specific immunity. The present study was conducted to examine the temporal characteristics of such immune responses to acute stress and to determine their association with sympathetic activity in detail. For this purpose, 15 female undergraduates engaged in a continuous mental arithmetic task for 14 min, and we collected their blood samples for immune indices (CD3+ T cells, CD4+ T cells, NK cells) each 3 min during the task and saliva samples before and after the task. Our results showed that the proportion of Natural Killer cells (NK cells) increased even 2 min after initiation of the task, whereas proportions of CD3+ and CD4+ lymphocytes decreased 8 min after initiation of the task. Moreover, we found significant correlations between cardiovascular activity and the variations of immune indices.
Article
Currently there is wide interest in the medicinal benefits of green tea (Camellia sinensis). Tea is one of the most widely consumed beverages in the world, and extracts of tea leaves are also sold as dietary supplements. Green tea extracts contain a unique set of catechins that possess biologic activity in antioxidant, antiangiogenesis, and antiproliferative assays that are potentially relevant to the prevention and treatment of various forms of cancer. With the increasing interest in the health properties of tea and a significant rise in their scientific investigation, it is the aim of this review to summarize recent findings on the anticancer and medicinal properties of green tea, focusing on the biologic properties of the major tea catechin, (-)-epigallocatechin and its antitumor properties.
Stress preferentially increase extraneuronal levels of excitatory amino acids in the prefrontal cortex: comparison to hippocampus and basal ganglia
  • K Kimura
K. Kimura et al. / Biological Psychology xxx (2006) xxx-xxx Moghaddam, B., 1993. Stress preferentially increase extraneuronal levels of excitatory amino acids in the prefrontal cortex: comparison to hippocampus and basal ganglia. Journal of Neuroscience 60, 1650-1657.
  • K Kimura
K. Kimura et al. / Biological Psychology xxx (2006) xxx-xxx
Cellular and mucosal immune reactions to mental and cold stress: associations with gender and cardiovascular reactivity
  • Willemsen