Neurobiological effects of the green tea constituent theanine and its potential role in the treatment of psychiatric and neurodegenerative disorders

Abstract

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 effect has been its apparent anxiolytic and calming effect due to its up-regulation of inhibitory neurotransmitters and possible modulation of serotonin and dopamine in selected areas. It has also recently been shown to increase levels of brain-derived neurotrophic factor. An increasing number of studies demonstrate a neuroprotective effects following cerebral infarct and injury, although the exact molecular mechanisms remain to be fully elucidated. Theanine also elicits improvements in cognitive function including learning and memory, in human and animal studies, possibly via a decrease in NMDA-dependent CA1 long-term potentiation (LTP) and increase in NMDA-independent CA1-LTP. Furthermore, theanine administration elicits selective changes in alpha brain wave activity with concomitant increases in selective attention during the execution of mental tasks. Emerging studies also demonstrate a promising role for theanine in augmentation therapy for schizophrenia, while animal models of depression report positive improvements following theanine administration. A handful of studies are beginning to examine a putative role in attention deficit hyperactivity disorder, and theoretical extrapolations to a therapeutic role for theanine in other psychiatric disorders such as anxiety disorders, panic disorder, obsessive compulsive disorder (OCD), and bipolar disorder are discussed.

Peripheral blood brain-derived neurotrophic factor in bipolar disorder: a comprehensive systematic review and meta-analysis

“…Thirtyfive studies, comprising a total of 2238 bipolar disorder patients and 1560 healthy control subjects, were eligible for review and included in the meta-analysis with a minimum of one pair-wise comparison each. [11][12][13][19][20][21]26, Exclusion of full 63 text articles and reports were based on (a) data on BDNF levels were unavailable, [66][67][68] (b) patients not suffering from bipolar disorder, [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] (c) the study not evaluating peripheral BDNF levels, (d) the study being a review or a comment, [107][108][109][110][111][112][113][114][115][116][117][118][119] (e) the study not comparing states or comparing bipolar patients with healthy control subjects [120][121][122] and/or (f) the study investigated treatment of experimental nature 123,124 and (g) the study presenting duplicate data presented in an included article. …”

What factors are influencing tea consumption among Chinese urban residents? An empirical study

“…Thielecke and Boschmann, 2009;Basu et al, 2010;Sae-Tan et al, 2011;Vernarelli and Lambert, 2013;Yousaf et al, 2014), and prevention of neurodegenerative diseases (e.g. Mandel et al, 2008;Hugel and Jackson, 2012;Lardner, 2014).…”

Remedial Effects of Tea and Its Phytoconstituents on Central Nervous System

“…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].…”