Recent Research Papers on
Synergistic inhibition of lung cancer cell lines by (−)-epigallocatechin-3-gallate in combination with clinically used nitrocatechol inhibitors of catechol- O -methyltransferase
Author: Sarah C. Forester and Joshua D. Lambert
(−)-Epigallocatechin-3-gallate (EGCG) has exhibited been studied for lung cancer inhibitory activity in vitroand in animal models, but it is rapidly methylated and inactivated by catechol- O -methyltransferase (COMT). Entacapone and tolcapone, COMT inhibitors, are used to mitigate the symptoms of Parkinson’s disease. We investigated the synergistic effects of entacapone/tolcapone and EGCG against lung cancer cell lines in culture. EGCG, entacapone and tolcapone inhibited the growth of H1299 human lung cancer cells (IC 50 = 174.9, 76.8 and 29.3 µM, respectively) and CL-13 murine lung cancer cells (IC 50 = 181.5, 50.7 and 19.7 µM, respectively) as single agents following treatment for 72h. Treatment with 1:10, 1:5, 1:2.5 and 1:1 combinations of EGCG and tolcapone or entacapone resulted in synergistically enhanced growth inhibition. The growth inhibitory effect of the combinations was mediated by induction of intracellular oxidative stress, cell cycle arrest and decreased nuclear translocation of nuclear factor-κΒ. Methylation of EGCG was dose dependently inhibited by entacapone and tolcapone (IC 50 = 10 and 20 µM, respectively) in a cell-free system, and both compounds increased the intracellular levels of unmethylated EGCG. Treatment of mice with EGCG in combination with tolcapone increased the bioavailability of EGCG and decreased the methylation of plasma norepinephrine: no apparent liver or behavioral toxicity was observed. In conclusion, the combination of EGCG and entacapone/tolcapone synergistically inhibited the growth of lung cancer cells in culture, and the mechanistic basis for this synergy is likely due in part to inhibition of COMT with resultant increase in the levels of unmetabolized EGCG.
Author: David Heber, Yanjun Zhang, Jieping Yang, Janice E. Ma, Susanne M. Henning, and Zhaoping Li
Green tea (GT) and caffeine in combination were shown to increase energy expenditure and fat oxidation, but less is known about the effects of black tea (BT) and oolong tea (OT). This study investigated whether decaffeinated polyphenol extracts from GT, BT, and OT decrease body fat and inflammation in male C57BL/6J mice fed high-fat/high-sucrose [HF/HS (32% energy from fat, 25% energy from sucrose)] diets. Mice were fed either an HF/HS diet with 0.25% of polyphenol from GT, OT, or BT or a low-fat/high-sucrose [LF/HS (10.6% energy from fat, 25% energy from sucrose)] diet for 20 wk. Monomeric tea polyphenols were found in the liver and adipose tissue of mice fed the HF/HS diet with GT polyphenols (GTPs) and OT polyphenols (OTPs) but not BT polyphenols (BTPs). Treatment with GTPs, OTPs, BTPs, and an LF/HS diet led to significantly lower body weight, total visceral fat volume by MRI, and liver lipid weight compared with mice in the HF/HS control group. Only GTPs reduced food intake significantly by ∼10%. GTP, BTP, and LF/HS-diet treatments significantly reduced serum monocyte chemotactic protein-1 (MCP-1) compared with HF/HS controls. In mesenteric fat, monocyte chemotactic protein-1 (Mcp1) gene expression was significantly decreased by treatment with GTPs, BTPs, OTPs, and an LF/HS diet and in liver tissue by GTP and BTP treatments. Mcp1 gene expression in epididymal fat was significantly decreased by the BTP and LF/HS diet interventions. In epididymal fat, consistent with an anti-inflammatory effect, adiponectin gene expression was significantly increased by GTPs and OTPs. Angiogenesis during adipose tissue expansion is anti-inflammatory by maintaining adipocyte perfusion. We observed significantly increased gene expression of vascular endothelial growth factor A by GTPs and vascular endothelial growth factor receptor 2 by BTPs and the LF/HS diet and a decrease in pigment epithelium-derived factor gene expression by OTPs and BTPs. In summary, all 3 tea polyphenol extracts induced weight loss and anti-inflammatory and angiogenic effects, although the tissue content of polyphenols differed significantly.
Author: David A Camfield , Con Stough , Jonathon Farrimond , Andrew B Scholey
A systematic review and meta-analysis was conducted on 11 randomized placebo-controlled human studies of acute effects of tea constituents L-theanine and epigallocatechin gallate, administered alone or in combination with caffeine, on cognitive function and mood. The outcome measures of mood were alertness, calmness, and contentedness, derived from the Bond-Lader scales, and state anxiety, from the State-Trait Anxiety Inventory. Cognitive measures assessed were attentional switch, intersensory attention, and rapid visual information processing. Standardized mean differences between placebo and treatment groups are presented for each study and outcome measure. Meta-analysis using a random-effects model was conducted when data were available for three or more studies. Evidence of moderate effect sizes in favor of combined caffeine and L-theanine in the first 2 hours postdose were found for outcome measures Bond-Lader alertness, attentional switching accuracy, and, to a lesser extent, some unisensory and multisensory attentional outcomes. Moderator analysis of caffeine and L-theanine doses revealed trends toward greater change in effect size for caffeine dose than for L-theanine dose, particularly during the first hour postdose.
Author: Yi Zeng and Huashuai Chen and Ting Ni and Rongping Ruan and Lei Feng and Chao Nie and Lingguo Cheng and Yang Li and Wei Tao and Jun Gu and Kenneth C. Land and Anatoli Yashin and Qihua Tan and Ze Yang and Lars Bolund and Huanming Yang and Elizabeth Hauser and D. Craig Willcox and Bradley J. Willcox and Xiao-Li Tian and James W. Vaupel
Logistic regression analysis based on data from 822 Han Chinese oldest old aged 92+ demonstrated that interactions between carrying FOXO1A-266 or FOXO3-310 or FOXO3-292 and tea drinking at around age 60 or at present time were significantly associated with lower risk of cognitive disability at advanced ages. Associations between tea drinking and reduced cognitive disability were much stronger among carriers of the genotypes of FOXO1A-266 or FOXO3-310 or FOXO3-292 compared with noncarriers, and it was reconfirmed by analysis of three-way interactions across FOXO genotypes, tea drinking at around age 60, and at present time. Based on prior findings from animal and human cell models, we postulate that intake of tea compounds may activate FOXO gene expression, which in turn may positively affect cognitive function in the oldest old population. Our empirical findings imply that the health benefits of particular nutritional interventions, including tea drinking, may, in part, depend upon individual genetic profiles.
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.
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.
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.
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.
Author: T. Giesbrecht, and J.A. Rycroft, and M.J. Rowson and E.A. De Bruin
The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.