Recent Research Papers on
Author: Hea Jin Park, Ji-Young Lee, Min-Yu Chung, Young-Ki Park, Allyson M. Bower, Sung I. Koo, Charles Giardina and Richard S. Bruno
Nonalcoholic steatohepatitis (NASH) is characterized by oxidative stress and inflammatory responses that exacerbate liver injury. The objective of this study was to determine whether the antioxidant and antiinflammatory activities of green tea extract (GTE) would protect against NASH in a model of diet-induced obesity. Adult Wistar rats were fed a low-fat (LF) diet or high-fat (HF) diet containing no GTE or GTE at 1% or 2% (HF+2GTE) for 8 wk. The HF group had greater (P ≤ 0.05) serum alanine (ALT) and aspartate aminotransferases and hepatic lipids than the LF group. Both GTE groups had lower ALT and hepatic lipid than the HF group. In liver and epididymal adipose, the HF group had lower glutathione as well as greater mRNA and protein expression of TNFα and monocyte chemoattractant protein-1 (MCP-1) and NFκB binding activity than the LF group. Compared to the HF group, the HF+2GTE group had greater glutathione and lower protein and mRNA levels of inflammatory cytokines in both tissues. NFκB binding activities at liver and adipose were also lower, likely by inhibiting the phosphorylation of inhibitor of NFκB. NFκB binding activities in liver and adipose (P ≤ 0.05; r = 0.62 and 0.46, respectively) were correlated with ALT, and hepatic NFκB binding activity was inversely related to liver glutathione (r = −0.35). These results suggest that GTE-mediated improvements in glutathione status are associated with the inhibition of hepatic and adipose inflammatory responses mediated by NFκB, thereby protecting against NASH.
Author: Jennifer M. Loftis, Clare J. Wilhelm, Marilyn Huckans
Objectives: Strategies that focus on the reduction of oxidative stress and inflammation may have therapeutic benefit for the treatment of schizophrenia. This clinical trial sought to determine, in a double-blind study, whether epigallocatechin gallate (EGCG), a green tea extract, is a useful adjunct to maintenance antipsychotic medication. Methods: Adults with schizophrenia, schizoaffective disorder or bipolar disorder who were maintained on antipsychotic and other psychotropic medications were randomized to supplemental EGCG or placebo. Study participants completed clinical assessments and blood draws to evaluate supplemental treatment effects on psychiatric symptoms and plasma inflammatory markers. Results: A total of 34 participants (17 EGCG, 17 placebo) were randomized and 25 participants (14 EGCG, 11 placebo) completed the study. Both treatment groups showed significant reductions in psychotic, depressive and anxiety symptoms from baseline to end of treatment. However, EGCG did not significantly affect psychiatric symptoms or inflammatory markers, as compared with placebo. Adverse effects were mild and comparable between groups. Conclusion: There was no signal for a therapeutic effect of the green tea extract EGCG on psychiatric symptoms in this placebo-controlled pilot study.
Author: Hae-Suk Kim, Vedrana Montana, Hyun-Ju Jang, Vladimir Parpura and Jeong-a Kim
Epigallocatechin gallate (EGCG) is a major polyphenol in green tea that has beneficial effects in the prevention of cardiovascular disease. Autophagy is a cellular process that protects cells from stressful conditions. To determine whether the beneficial effect of EGCG is mediated by a mechanism involving autophagy, the roles of the EGCG-stimulated autophagy in the context of ectopic lipid accumulation were investigated. Treatment with EGCG increased formation of LC3-II and autophagosomes in primary bovine aortic endothelial cells (BAEC). Activation of calmodulin-dependent protein kinase kinase β was required for EGCG-induced LC3-II formation, as evidenced by the fact that EGCG-induced LC3-II formation was significantly impaired by knockdown of calmodulin-dependent protein kinase kinase β. This effect is most likely due to cytosolic Ca(2+) load. To determine whether EGCG affects palmitate-induced lipid accumulation, the effects of EGCG on autophagic flux and co-localization of lipid droplets and autophagolysosomes were examined. EGCG normalized the palmitate-induced impairment of autophagic flux. Accumulation of lipid droplets by palmitate was markedly reduced by EGCG. Blocking autophagosomal degradation opposed the effect of EGCG in ectopic lipid accumulation, suggesting the action of EGCG is through autophagosomal degradation. The mechanism for this could be due to the increased co-localization of lipid droplets and autophagolysosomes. Co-localization of lipid droplets with LC3 and lysosome was dramatically increased when the cells were treated with EGCG and palmitate compared with the cells treated with palmitate alone. Collectively, these findings suggest that EGCG regulates ectopic lipid accumulation through a facilitated autophagic flux and further imply that EGCG may be a potential therapeutic reagent to prevent cardiovascular complications.
Author: Yumei Chen, Bo Zhu, Hongping Zhang, Xishi Liu, Sun-Wei Guo
In an effort to search for novel therapeutics for adenomyosis, we sought to determine whether treatment with epigallocatechin-3-gallate (EGCG) would suppress the myometrial infiltration, improve pain behavior, lower stress level, and reduce uterine contractility in a mice model of adenomyosis. Adenomyosis was induced in 28 female ICR mice neonatally dosed with tamoxifen, while another 12 (group C) were dosed with solvent only, which served as a blank control. Starting from 4 weeks after birth, hot plate test was administrated to all mice every 4 weeks. At the 16th week, all mice induced with adenomyosis were randomly divided into 3 groups: low-dose EGCG (5 mg/kg), high-dose EGCG (50 mg/kg), and untreated. Group C received no treatment. After 3 weeks of treatment, the hot plate test was administered again, a blood sample was taken to measure the plasma corticosterone level by enzyme-linked immunosorbent assay, and then all mice were sacrificed. The depth of myometrial infiltration and uterine contractility were also evaluated. We found that the induction of adenomyosis resulted in progressive generalized hyperalgesia, along with elevated amplitude and frequency of uterine contractions as well as elevated plasma corticosterone levels. The EGCG treatment dose dependently suppressed myometrial infiltration, improved generalized hyperalgesia, reduced uterine contractility, and lowered plasma corticosterone levels. These results suggest that induced adenomyosis causes pain and elevates stress levels in mice. Uterine hyperactivity may contribute to dysmenorrhea in women with adenomyosis who might also have elevated stress level due to pain. The EGCG appears to be a promising compound for treating adenomyosis.
Author: Federica Rizzi, Valeria Naponelli, Alessandro Silva, Alice Modernelli, Ileana Ramazzina, Martina Bonacini, Saverio Tardito, Rita Gatti, Jacopo Uggeri and Saverio Bettuzzi
Increasing doses of Polyphenon E®, a standardized green tea extract, were given to PNT1a and PC3 prostate epithelial cells mimicking initial and advanced stages of prostate cancer (PCa), respectively. Cell death occurred in both cell lines, with PNT1a being more sensitive [half-maximal inhibitory concentration (IC50) = 35 μg/ml] than PC3 (IC50 = 145 μg/ml) to Polyphenon E®. Cell cycle arrest occurred at G0/G1 checkpoint for PNT1a, and G2/M for PC3 cells. Endoplasmic reticulum stress (ERS) and unfolded protein response (UPR) occurred in both cell lines, with each exhibiting different timing in response to Polyphenon E®. Autophagy was transiently activated in PNT1a cells within 12 h after treatment as a survival response to overcome ERS; then activation of caspases and cleavage of poly (ADP ribose) polymerase 1 occurred, committing cells to anoikis death. Polyphenon E® induced severe ERS in PC3 cells, causing a dramatic enlargement of the ER; persistent activation of UPR produced strong upregulation of GADD153/CHOP, a key protein of ERS-mediated cell death. Thereafter, GADD153/CHOP activated Puma, a BH3-only protein, committing cells to necroptosis, a programmed caspase-independent mechanism of cell death. Our results provide a foundation for the identification of novel targets and strategies aimed at sensitizing apoptosis-resistant cells to alternative death pathways.
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 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: David O. Kennedy
Flavonoids and other polyphenols are ubiquitous plant chemicals that fulfill a range of ecologic roles for their home plant, including protection from a range of biotic and abiotic stressors and a pivotal role in the management of pathogenic and symbiotic soil bacteria and fungi. They form a natural part of the human diet, and evidence suggests that their consumption is associated with the beneficial modulation of a number of health-related variables, including those related to cardiovascular and brain function. Over recent years, the consensus as to the mechanisms responsible for these effects in humans has shifted away from polyphenols having direct antioxidant effects and toward their modulation of cellular signal transduction pathways. To date, little consideration has been given to the question of why, rather than how, these plant-derived chemicals might exert these effects. Therefore, this review summarizes the evidence suggesting that polyphenols beneficially affect human brain function and describes the current mechanistic hypotheses explaining these effects. It then goes on to describe the ecologic roles and potential endogenous signaling functions that these ubiquitous phytochemicals play within their home plant and discusses whether these functions drive their beneficial effects in humans via a process of “cross-kingdom” signaling predicated on the many conserved similarities in plant, microbial, and human cellular signal transduction pathways.
Author: Binbin Chen and Guangyi Liu and Peimei Zou and Xing Li and Qiufa Hao and Bei Jiang and Xiangdong Yang and Zhao Hu
Cisplatin (CP)-induced nephrotoxicity hampers its application in clinic. Green tea, particularly its predominant polyphenolic constituent epigallocatechin-3-gallate (EGCG), possesses anti-inflammatory, antioxidant, and anti-apoptotic properties. The present study was designed to investigate the protective effects of EGCG against CP-induced nephrotoxicity in mice. Male C57/BL6 mice in different groups received single injection of CP (20 mg/kg) and EGCG (100 mg/kg) in various sets and kidney tissues and blood were collected after killing. Then, samples were used for biochemical and immunohistochemical assay. Our results showed EGCG decreased biochemical factors and immunohistochemical damage induced by CP. Besides, expression of phosphorylated-extracellular signal-regulated kinase (p-ERK), glucose-regulated protein 78 (GRP78), caspase-12, and apoptosis of kidney were decreased by EGCG via inhibition of endoplasmic reticulum (ER) stress-induced apoptosis.
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.