Research Database

Author: Borzelleca JF, and Peters D, and Hall W

This study was conducted to evaluate the safety of l-theanine (Suntheanine®) when administered as a dietary admixture to male and female Crl:CD® (SD)GS BR rats at concentrations providing doses of 0, 1500, 3000 or 4000 mg/kg bw/day for 13 weeks. The study design was consistent with OECD Guideline 408 and USFDA Redbook II (1993) and GLP. There were no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, hematology, or urinalysis. There were no consistent treatment-related adverse effects in gross pathology, organ weights or ratios or histopathology. The increased incidence of renal tubular cell adenomas in high-dose females only were not consistent with the characteristics of a renal carcinogen (due to early onset and low number of animals affected) but were more consistent with a genetic predisposition than with direct organ toxicity. The no-observed-adverse-effect-level (NOAEL) was 4000 mg/kg bw/day, the highest dose tested.

 

Get the whole article here

Identification of the Mitochondrial Glutamate Transporter BACTERIAL EXPRESSION, RECONSTITUTION, FUNCTIONAL CHARACTERIZATION, AND TISSUE DISTRIBUTION OF TWO HUMAN ISOFORMS

Author: Giuseppe Fiermonte‡, and Luigi Palmieri‡, and Simona Todisco‡, and Gennaro Agrimi‡, and Ferdinando Palmieri‡§ and John E. Walker

The mitochondrial carriers are a family of transport proteins in the inner membranes of mitochondria. They shuttle substrates, metabolites, and cofactors through this membrane and connect cytoplasm functions with others in the matrix. Glutamate is co-transported with H⁺ (or exchanged for OH⁻), but no protein has ever been associated with this activity. Two human expressed sequence tags encode proteins of 323 and 315 amino acids with 63% identity that are related to the aspartate-glutamate carrier, a member of the carrier family. They have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties demonstrate that the two proteins are isoforms of the glutamate/H⁺ symporter described in the past in whole mitochondria. Isoform 1 is expressed at higher levels than isoform 2 in all the tissues except in brain, where the two isoforms are expressed at comparable levels. The differences in expression levels and kinetic parameters of the two isoforms suggest that isoform 2 matches the basic requirement of all tissues especially with respect to amino acid degradation, and isoform 1 becomes operative to accommodate higher demands associated with specific metabolic functions such as ureogenesis.

 

 

Get the whole article here

Author: Wiley W. Souba and Ming Pan and Bruce R. Stevens

Transmural Potential Changes Associated with the in Vitro Absorption of Theanine in the Guinea Pig Intestine

Author: Sachie Kitaoka, and Hisayoshi Hayashi, and Hidehiko Yokogoshi and Yuichi Suzuki

Theanine, L-N-ethylglutamine, is one of the major components of amino acids in Japanese green tea. To characterize the mode for intestinal absorption of theanine, the ionic dependency and kinetic properties of the theanine- and glutamine-evoked transmural electrical potential difference changes (ΔPD) were investigated in vitro by using everted sacs prepared from the guinea pig ileum. Both theanine and glutamine applied to the luminal side induced dose-dependent increases in ΔPD (increase in serosal positive value). The theanine- and glutamine-evoked ΔPD values conformed to the Michaelis-Menten relationship, with ΔPDmax not being different, whereas the half-saturation concentration was lower for glutamine (3.1 ± 0.2 mM) than for theanine (21.4 ± 0.6 mM). The theanine-evoked ΔPD value was much smaller when theanine was applied in the presence of glutamine than when applied alone. The theanine- and glutamine-evoked ΔPD values were both inhibited by removing Na+ from the luminal solution. These results suggest that the intestinal absorption of theanine and glutamine is mediated by a common Na+-coupled co-transporter in the brush-border membrane, the affinity of which is lower for theanine than for glutamine.

 

 

Get the whole article here

Author: Desai MJ, and Gill MS, and Hsu WH, and Armstrong DW

Theanine, first discovered in tea, is a chiral nonproteinic amino acid that has been reported to have cardiovascular, neurological, and oncological effects. It is being considered as a therapeutic/medicinal agent and additive in consumer products. The present study evaluated the pharmacokinetics of d-theanine, l-theanine, and d,l-theanine in plasma and urine using LC-ESI/MS in rats after oral (p.o.) and intraperitoneal (i.p.) administration. Oral administration data indicated that gut absorption of d-theanine was far less than that of l-theanine. However, after i.p. administration, plasma theanine concentrations of l- and d-theanine were similar. This indicated that d- and l-theanine may exhibit a competitive effect with respect to intestinal absorption. Regardless of the route of administration, p.o. or i.p., the presence of the other enantiomer always decreased theanine plasma concentrations, indicating d,l-theanine competition with respect to urinary reabsorption. Data on urinary concentrations of d-theanine suggested that the d-isomer may be eliminated with minimal metabolism. l-Theanine appeared to be preferentially reabsorbed and metabolized by the kidney while d-theanine was preferentially excreted. Clearly, the bioequivalencies of d,l-theanine and its enantiomers were found to be quite different from one another. Consequently, the efficacy of commercial theanine products containing d-theanine, l-theanine, or d,l-theanine may be quite different. 

 

Get the whole article here

Author: K. Helen Ekborg-Ott, and Andre Taylor, and Daniel W. Armstrong

Theanine is the main amino acid component in tea. It usually constitutes between 1 and 2% of the dry weight of the tea leaves. It is as prevalent in tea as all other free amino acids combined. Both enantiomers of theanine were found to have a similar sweet taste, with little or no aftertaste. It was found that black and half-green teas (except for Formosa Oolong) contained as much, or more, theanine as green teas. No correlation was found between the absolute concentration of theanine in tea and its enantiomeric composition. An inverse correlation was found between certain grades of tea (e.g., pekoe, Flowery Orange Pekoe, etc.) and the percent of d-theanine present. This could provide the basis for a reproducible, scientific method to grade and/or evaluate teas. Theanine slowly racemizes in aqueous solution. It also undergoes hydrolysis, particularly at basic pH values. By monitoring these processes, information may be gleaned on the production, storage, handling, and shipping of tea and tea products.

 

 

Get the whole article here

Author: Yaning Lu and Jinsong Zhang and Xiaochun Wan and Men Long and Daxiang Li and Pandeng Lei and Zhengzhu Zhang

Theanine, an amino acid contained in green tea, is known to possess many pharmacological functions. In this paper, we investigated the absorption of theanine in the human intestinal epithelium, using a Caco-2 monolayer model. Different concentrations of either pure theanine or green tea extracts were administered to Caco-2 cells. The theanine content in the samples was analysed by high-performance liquid chromatography, coupled with fluorescence detection. Cell permeation was also measured. The data revealed that the transport of pure theanine occurred in a manner consistent with passive diffusion. Surprisingly, pure theanine showed good absorption, whereas theanine in the green tea extract was poorly absorbed in the Caco-2 cell model. Furthermore, the transport of theanine in green tea extract in the basolateral (BL) to apical (AP) direction was much greater than that in the AP–BL direction, suggesting that green tea components profoundly affect the trans-epithelial transport of theanine in this Caco-2 cell model.

 

 

Get the whole article here

Author: Einöther SJ, and Martens VE, and Rycroft JA, and De Bruin EA

Author: Haskell CF, and Kennedy DO, and Milne AL, and Wesnes KA, and Scholey AB

L-Theanine is an amino acid found naturally in tea. Despite the common consumption of l-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of l-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. l-Theanine increased ‘headache’ ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported ‘mental fatigue’. In addition to improving RVIP accuracy and ‘mental fatigue’ ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. ‘Headache’ and ‘tired’ ratings were reduced and ‘alert’ ratings increased. There was also a significant positive caffeine × l-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing l-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.

 

Get the whole article here

Author: Foxe JJ, and Morie KP, and Laud PJ, and Rowson MJ, and de Bruin EA, and Kelly SP

Caffeine and l-theanine, both naturally occurring in tea, affect the ability to make rapid phasic deployments of attention to locations in space as reflected in behavioural performance and alpha-band oscillatory brain activity (8–14 Hz). However, surprisingly little is known about how these compounds affect an aspect of attention that has been more popularly associated with tea, namely vigilant attention: the ability to maintain focus on monotonous tasks over protracted time-periods. Twenty-seven participants performed the Sustained Attention to Response Task (SART) over a two-hour session on each of four days, on which they were administered caffeine (50 mg), theanine (100 mg), the combination, or placebo in a double-blind, randomized, cross-over fashion. Concurrently, we recorded oscillatory brain activity through high-density electroencephalography (EEG). We asked whether either compound alone, or both in combination, would affect performance of the task in terms of reduced error rates over time, and whether changes in alpha-band activity would show a relationship to such changes in performance. When treated with placebo, participants showed a rise in error rates, a pattern that is commonly observed with increasing time-on-task, whereas after caffeine and theanine ingestion, error rates were significantly reduced. The combined treatment did not confer any additional benefits over either compound alone, suggesting that the individual compounds may confer maximal benefits at the dosages employed. Alpha-band oscillatory activity was significantly reduced on ingestion of caffeine, particularly in the first hour. This effect was not changed by addition of theanine in the combined treatment. Theanine alone did not affect alpha-band activity.

 

Get the whole article here