Table 1- uploaded by Anne Lardner
Content may be subject to copyright.
Effect of L-Theanine on brain neurotransmitter levels 

Effect of L-Theanine on brain neurotransmitter levels 

Source publication
Article
Full-text available
Theanine (n-ethylglutamic acid), a non-proteinaceous amino acid component of green and black teas, has received growing attention in recent years due to its reported effects on the central nervous system. It readily crosses the blood-brain barrier where it exerts a variety of neurophysiological and pharmacological effects. Its most well-documented...

Context in source publication

Context 1
... known effects of theanine on brain neurotrans- mitter activity is summarized in Table 1. Despite its structural similarity to glutamate, there is no evidence of any increase in glutamate levels following theanine injection or administration, thus rendering unlikely the conversion of theanine to glutamate within the CNS. ...

Similar publications

Article
Full-text available
This study describes a fundamental functional difference between the two main polymorphisms of the pro-form of brain-derived neurotrophic factor (proBDNF), providing an explanation as to why these forms have such different age-related neurological outcomes. Healthy young carriers of the Met66 form (present in ∼30% Caucasians) have reduced hippocamp...
Article
Full-text available
Cumulative evidence has indicated that there is an important role for adult hippocampal neurogenesis in cognitive function. With the increasing prevalence of cognitive decline associated with neurodegenerative diseases among the ageing population, physical exercise, a potent enhancer of adult hippocampal neurogenesis, has emerged as a potential pre...
Article
Full-text available
Synaptic plasticity is widely regarded as a putative biological substrate for learning and memory processes. While both decreases and increases in synaptic strength are seen as playing a role in learning and memory, long-term depression (LTD) of synaptic efficacy has received far less attention than its counterpart long-term potentiation (LTP). Nev...

Citations

... The beneficial effectiveness was positively correlated with serum levels of brain-derived neurotrophic factor in schizophrenic and schizoaffective patients orally given theanine for eight weeks [74]. Therapeutic benefits were also predicted for theanine in other psychiatric disorders, including anxiety, panic, and obsessive-compulsive and bipolar disorders [75]. Although a direct positive correlation between experimental promotion of adult neurogenesis and clinical therapeutic benefits is not fully clarified to date as mentioned above, the green tea amino acid theanine seems to alleviate a variety of symptoms and syndromes associated with dysfunctions of harmonization of the intact neuronal network toward brain wellness with guaranteed safety in young to adult humans. ...
Article
Full-text available
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.
... Furthermore, it's been observed in research studies that the phytocompounds of tea (Green/Black) also prevents, the division of mitochondrial layer against iron induced lipid per oxidation and enhanced the survival rate in many in vivo models [42,43]. Hence, it can be concluded from the recent research updates, that the high metal chelating quality of its constituents may provide a unique essential neuroprotection against many neurological disorders [44]. ...
... 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]. In accordance with this, we have reported multiple favourable effects of four weeks L-theanine administration (250 mg/day) in patients with major depressive disorder (MDD), although this was an open-label study [40]. ...
Article
Full-text available
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.
... Structurally, L -theanine is a glutamate analogue, hence binding to the same glutamate receptors and therefore hindering the neuroexcitatory effects triggered by glutamatergic activation [48,49]. It is believed that L -theanine mediation on glutamatergic neurotransmission is the main pathway by which this non-proteinaceous amino acid is able to attenuate anxiety disorders and mitigate the negative outcomes of exposure to acute and chronic stress. ...
Article
Anxiety disorders are highly prevalent in modern societies, and are ranked the sixth most important contributor of non-fatal negative health outcomes. L-theanine is an amino acid naturally found in green tea (Camellia sinensis) and some other plant extracts, and recent clinical studies have proposed promising adjuvant effects of L-theanine for the negative impact of anxiety and psychological stress on health. In this integrative narrative review, we aimed to appraise and further discuss the effects of L-theanine administration on anxiety disorders and psychological stress. Published data suggests that L-theanine administered at daily doses ranging from 200 to 400 mg for up to 8 weeks are safe and induce anxiolytic and anti-stress effects in acute and chronic conditions. L-theanine at doses lower and higher than these may also show promising therapeutic potential; however, a more thorough investigation through randomized double-blind placebo-controlled crossover clinical trials are necessary to elucidate its effects for longer periods, providing further insights for meta-analyses and the development of recommendation guidelines. Additionally, animal studies investigating a higher dosage, its combination with other pharmacological compounds and associated metabolic comorbidities are recommended, as cases of hepatotoxicity associated with the consumption of green tea extract have been reported.
... Extrapolated therapeutic benefits of theanine are discussed in other psychiatric disorders as well. These include anxiety disorders, panic disorder, obsessive compulsive disorder and bipolar disorder (Lardner, 2014). In an open clinical study on patients suffering from major depressive disorder, oral intake of theanine at 250 mg/day for 8 weeks promotes the therapeutic efficacy of the current medication for depressive symptoms, anxiety, sleep disturbance and cognitive impairment as described above (Hidese et al., 2017). ...
Article
Full-text available
The green tea amino acid theanine is abundant in green tea rather than black and oolong teas, which are all made of the identical tea plant “Chanoki” (Camellia sinensis). Theanine has a molecular structure close to glutamine (GLN) compared to glutamic acid (Glu), in terms of the absence of a free carboxylic acid moiety from the gamma carbon position. Theanine efficiently inhibits [3H]GLN uptake without affecting [3H]Glu uptake in rat brain synaptosomes. In contrast to GLN, however, theanine markedly stimulates the abilities to replicate and to commit to a neuronal lineage following prolonged exposure in cultured neural progenitor cells (NPCs) prepared from embryonic and adult rodent brains. Upregulation of transcript expression is found for one of the GLN transporter isoforms, Slc38a1, besides the promotion of both proliferation and neuronal commitment along with acceleration of the phosphorylation of mechanistic target of rapamycin (mTOR) and relevant downstream proteins, in murine NPCs cultured with theanine. Stable overexpression of Slc38a1 similarly facilitates both cellular replication and neuronal commitment in pluripotent embryonic carcinoma P19 cells. In P19 cells with stable overexpression of Slc38a1, marked phosphorylation is seen for mTOR and downstream proteins in a manner insensitive to further additional phosphorylation by theanine. Taken together, theanine would exhibit a novel pharmacological property to up-regulate Slc38a1 expression for activation of the intracellular mTOR signaling pathway required for neurogenesis after sustained exposure in undifferentiated NPCs in the brain. In this review, a novel neurogenic property of the green tea amino acid theanine is summarized for embryonic and adult neurogenesis with a focus on the endogenous amino acid GLN on the basis of our accumulating evidence to date.
... With the consideration that GABA Oolong tea may not cross the BBB a different tea will also be trialled in the study, Gyokuro Green tea, which is high in the compound L-Theanine. L-Theanine is an amino acid analogue of L-glutamate and L-glutamine, readily crosses the BBB, and is thought to increase by proxy the GABA levels within the brain [127][128] by exerting an indirect action on GABA A receptors [129]. GABA and L-Theanine tea are compared to a placebo tea in this double-blind, placebo controlled, repeated measures study. ...
Article
Objective: The research has shown an association with sensorimotor integration and symptomology of Autism Spectrum Conditions (ASC). Specific areas of the brain that are involved in sensorimotor integration, such as the cerebellum and basal ganglia, are pathologically different in individuals with ASC in comparison to typically developing (TD) peers. These brain regions contain GABAergic inhibitory neurons that release an inhibitory neurotransmitter, γ-Aminobutyric acid (GABA). Brain GABA levels are decreased in ASC. This study explored the effect of introducing a non-invasive GABA substitute, in the form of GABA Oolong tea, on sensorimotor skills, ASC profiles, anxieties and sleep of children with ASC. Methods: Nine children took part: (5 male, 4 female). Each child participated in three tea conditions: high GABA, high L-Theanine (a compound that increases GABA), placebo with low GABA. A double-blind, repeated measures design was employed. Measures were taken after each tea condition. Sensory and ASC profiles were scored using parental questionnaires. Motor skills were assessed using a gold standard coordination assessment. Sleep was monitored using an actiwatch and anxiety measured through cortisol assays. Subjective views were sought from parents on ‘best’ tea. Results: The results showed significant improvement in manual dexterity and some large individual improvements in balance, sensory responsivity, DSM-5 criteria and cortisol levels with GABA tea. Improvements were also seen in the L-Theanine condition although they were more sporadic. Conclusions: These results suggest that sensorimotor abilities, anxiety levels and DSM-5 symptomology of children with ASC can benefit from the administration of GABA in the form of Oolong tea.
... In addition to these, natural compounds like huperzine A [127], galanthamine and vinpocetine [128] have been used for their nootropic effects. L-theanine [129,130], which is an amino-acid that is present in green tea (Camelia sinensis), L-tyrosine [131] (an amino acid precursor to catecholamine neurotransmitters such as dopamine and noradrenaline), L-taurine [132,133], a semi-essential, sulphur-containing amino acid and acetyl-l-carnitine [134], an endogenous antioxidant which also acts as a cellular energy carrier at the level of the mitochondrion are also notable compounds. Table 1 shows the specific mechanisms of action of synthetic nootropics as well as herbal and natural nootropic agents that have similar mechanisms, while Table 2 is a tabular presentation of the different preclinical and clinical studies that have examined the probable or confirmed roles and mechanisms (Fig. 2) of a number of herbal and food-derived nootropic agents. ...
Article
Background: Age-related cognitive decline has been suggested to result from an increase in brain neurone loss, which is attributable to continued derangement of the brain's oxidant/antioxidant balance. Increased oxidative stress and a concomitant decrease in the brain's antioxidant defense system have been associated with functional senescence and organismal ageing. However, nature has configured certain foods to be rich sources of nootropic agents, with research showing that increased consumption of such foods or food ingredients may be protective against ageing-related memory decline. This knowledge is becoming increasingly valuable in an era when the boundary that separates food from medicine is becoming blurred. In this review, we examine extant literature dealing with the impact of ageing on brain structure and function, with emphasis on the roles of oxidative stress. Secondly, we review the benefits of food-based antioxidants with nootropic effects and/or food-based nootropic agents in mitigating memory decline; with a view to improving our understanding of likely mechanisms. We also highlight some of the limitations to the use of food-based nootropics and suggest ways in which they can be better employed in the clinical management of age-related cognitive decline. Conclusion: While it is known that the human brain endures diverse insults in the process of ageing, food-based nootropics are likely to go a long way in mitigating the impacts of these insults. Further research is needed before we reach a point where food-based nootropics are routinely prescribed.
... The amino acid in green tea supposedly elevates serotonin (the feel-good chemical) and/or dopamine (the neurohormone) levels in some areas of the brain [9]. It is suggested that, in so doing, it promotes a state of 'attentive relaxation,' by opposing the stimulation and anxiety-causing effects of caffeine. ...
Article
Full-text available
Green tea has achieved a remarkably impressive healing, or curative reputation in the West-more so, in recent times. The herb is replete with a historical legacy as a safe, effective anti-inflammatory, analgesic, and antioxidant agent. Research has shown that green tea has the ability to reduce arthritic pain, including the risk of certain forms of cancer. Other studies suggest that green tea has the ability to stabilise blood lipids-this activity makes it an important component in cardiac healthcare [1]. The difference between green tea and other forms of tea is that the former is not fermented; it, thus, retains all the powerful antioxidants which are otherwise lost in the fermenting process [2]. Green tea, as studies also report, is one of the most potent, also naturally-occurring, anti-inflammatory cyclooxygenase-2 (COX-2), or coxib inhibitors. It contains over 50 anti-inflammatory compounds, including salicylic acid-a naturally occurring COX-2 inhibitor, from which aspirin is synthesised [3]. There is yet another upside to green tea. The healing beverage works in much the same way as anti-inflammatory drugs, or conventional COX-2 inhibitors, but without the former's dangerous side-effects.
... It is mostly found in green tea leaves (Sakato, 1949). L-THE is added to functional foods in a tea form or imbedded in another matrix, related with beneficial properties such as developing cognitive function and relaxation (Williams et al., 2016;Lardner, 2014). In a recent study, 200 mgL-THE was conducted to healthy participants in a beverage, for the determination of useful stress-related effects (White et al., 2016). ...
... A natural ethylamide analogue of glutamate, preclinical studies have found LT to pass freely through the blood-brain barrier, reduce presynaptic glutamate release ( Kakuda et al., 2008), increase inhibitory neurotransmitter GABA, and enhance glycine and dopamine release ( Kakuda et al., 2008;Kimura and Murata, 1971;Shen et al., 2011;Yamada et al., 2007Yamada et al., , 2005. Although the direct effects of LT on GABA pathways is not well understood, a recent study has shown differential decreases of cortical and hippocampal GABA in mouse models ( Schallier et al., 2013 neuropharmacology has also highlighted its neuroprotective effects, as well as the ability to increase alpha wave brain activity (Lardner, 2014). Alpha brain-activity is a measure of wakeful relaxation and has been associated with creativity, improved concentration, and decreased anxiety (Lardner, 2014). ...