High Dose Of Epigallocatechin-3-gallate Research Articles

Suppression mechanism of L-lysine on the Epigallocatechin-3-gallate-induced loss of myofibrillar protein gelling potential

As a natural antioxidant, Epigallocatechin-3-gallate (EGCG) needed to be added in high doses to maintain the quality of meat products. However, high doses of EGCG caused the excessive aggregation of myofibrillar protein (MP), which damaged the gel properties of MP gels. Therefore, the purpose of this study was to investigate the mitigation of EGCG-induced loss of MP gelling potential by L-Lysine (L-Lys). The results showed that the addition of 20 mM L-Lys induced excessive unfolding and loose aggregation of MP at 10 µmol/g EGCG, and hence, reducing the solubility (14.5%) and the tryptophan fluorescence, and forming a network structure with a large aperture. Therefore, the cooking loss was decreased from 29.20% to 15.13%, and the strength of MP gels was decreased from 0.35 N to 0.17 N. However, L-Lys hindered the hydrogen bonding interactions and hydrophobic interactions between MP and EGCG by competing the binding sites of MP at 50 µmol/g EGCG, which was supported by the Zeta potential, surface hydrophobicity, FTIR and molecular docking analysis. Thus L-Lys mitigated the protein aggregation caused by 50 µmol/g EGCG, improved the solubility (23.02%∼86.99%) and apparent viscosity, which were beneficial for the formation of a continuous network structure in MP gels. Therefore, the cooking loss of MP gels was decreased from 52.40% to 41.30%, and the gel strength was enhanced from 0.13 N to o.22 N with 20 mM L-Lys addition. The present study could provide a new strategy for increasing the amounts of EGCG in meat products without damaging the gel properties of meat products.

Positive effects of Epigallocatechin-3-gallate (EGCG) intervention on insulin resistance and gut microbial dysbiosis induced by bisphenol A

Schematic illustration of ameliorative effects of EGCG on BPA-induced insulin resistance. • EGCG intervention successfully ameliorated insulin resistance and impaired insulin sensitivity induced by BPA exposure. • EGCG intervention restored serious damage of gut tight junctions. • EGCG effectively improved intestinal flora disorder and increased gut short chain fatty acids level. Bisphenol A (BPA), a plasticizer, is widely believed to cause metabolic disorders. However, an effective intervention is still absent. This study investigated the beneficial effects of Epigallocatechin-3-gallate (EGCG) on insulin resistance and microbial disturbance induced by BPA. The serum glucose, insulin, total triglyceride, and total cholesterol were decreased in BPA-treated mice after the intervention of EGCG. The sensitivity of insulin signals in peripheral tissue was improved by modulating the phosphorylation of IRS-1, Akt, and GSK-3β. In addition, 16S rRNA analysis for fecal microbiota showed the relative abundance of Ruminiclostridium , Blautia , unidentified_Ruminococcaceae , and Candidatus_Saccharimonas were restored by the high dose of EGCG. Furthermore, EGCG increased the concentrations of fecal short-chain fatty acids and protected the gut barrier impaired by BPA. Overall, our results demonstrated the positive effects of EGCG on BPA-induced insulin resistance and gut microbial dysbiosis. The current study provides a potential treatment for the chronic metabolic toxicity of BPA.

Increased dosage and treatment time of Epigallocatechin-3-gallate (EGCG) negatively affects skeletal parameters in normal mice and Down syndrome mouse models.

Bone abnormalities affect all individuals with Down syndrome (DS) and are linked to abnormal expression of DYRK1A, a gene found in three copies in people with DS and Ts65Dn DS model mice. Previous work in Ts65Dn male mice demonstrated that both genetic normalization of Dyrk1a and treatment with ~9 mg/kg/day Epigallocatechin-3-gallate (EGCG), the main polyphenol found in green tea and putative DYRK1A inhibitor, improved some skeletal deficits. Because EGCG treatment improved mostly trabecular skeletal deficits, we hypothesized that increasing EGCG treatment dosage and length of administration would positively affect both trabecular and cortical bone in Ts65Dn mice. Treatment of individuals with DS with green tea extract (GTE) containing EGCG also showed some weight loss in individuals with DS, and we hypothesized that weights would be affected in Ts65Dn mice after EGCG treatment. Treatment with ~20 mg/kg/day EGCG for seven weeks showed no improvements in male Ts65Dn trabecular bone and only limited improvements in cortical measures. Comparing skeletal analyses after ~20mg/kg/day EGCG treatment with previously published treatments with ~9, 50, and 200 mg/kg/day EGCG showed that increased dosage and treatment time increased cortical structural deficits leading to weaker appendicular bones in male mice. Weight was not affected by treatment in mice, except for those given a high dose of EGCG by oral gavage. These data indicate that high doses of EGCG, similar to those reported in some treatment studies of DS and other disorders, may impair long bone structure and strength. Skeletal phenotypes should be monitored when high doses of EGCG are administered therapeutically.

Evaluation of (-)-epigallocatechin-3-gallate (EGCG)-induced cytotoxicity on astrocytes: A potential mechanism of calcium overloading-induced mitochondrial dysfunction

(-)-epigallocatechin-3-gallate (EGCG), the main component of green tea, has long been explored in the treatment and/or prevention of central nervous system (CNS) disorders. However, EGCG has been recently shown to exhibit acute and subacute toxicity. Although a lot of work has been done, the mechanisms of EGCG-induced mitochondrial dysfunction has not been delineated in primary astrocyte. Here, the mitotoxic effect of EGCG on primary astrocytes was investigated by measuring Ca2+ overloading-induced mitochondrial dysfunction. As expected, EGCG dose-dependently inhibited astrocytes growth depending on Ca2+ overloading, especially at 50 μM EGCG group. It is interesting to note that Ca2+ influx from the extracellular space was responsible for an increase in the cytosolic Ca2+ level ([Ca2+]i) by opening voltage-gated calcium channels (VGCCs) and, consequently, mitochondrial Ca2+ ([Ca2+]m) overloaded via the mitochondrial Ca2+ uniporter (MCU). As a result, mitochondrial dysfunction was induced, including the opening of the mitochondrial permeability transition pore (mPTP), mitochondrial membrane depolarization, an increasing in reactive oxygen species (ROS), and cytochrosome c (cyt c) releasing. Therefore, more apoptotic cells were observed in 50 μM EGCG group than that of in 1 μM EGCG group. These findings suggested that a high dose of EGCG was toxic to astrocytes partly by targeting mitochondria via calcium pathway, which would extend our understanding of the toxicity of EGCG and the underlying mechanisms.

EGCG: Potential application as a protective agent against grass carp reovirus in aquaculture.

Grass carp reovirus (GCRV) is the primary cause of grass carp haemorrhagic disease. The major catechin in green tea, (-)-epigallocatechin-3-gallate (EGCG), has been found to have anti-GCRV activity in the C.idellus kidney cell line (CIK). The aim of this study was to test the potential application of EGCG as an anti-GCRV agent in aquaculture. Here, we demonstrate that various concentrations (99%, 50% and 35%) of EGCG could inhibit GCRV infectivity. EGCG (50%) + GCRV treatment significantly reduced the number of dead fish at 1-, 2-, 3-, 4 -and 5-day post-challenge compared with the negative control (GCRV challenge without EGCG treatment). The safety of EGCG compound products on cell survival was studied using four fish cell lines; we did not detect a significant change in cell viability within 24hours of EGCG incubation. We also evaluated toxicity and concentrations of malondialdehyde (MDA), glutathione (GSH) and lysozyme (LZM) in the grass carp, and the results showed that even a high dose of EGCG did not induce toxicity. Following EGCG compound injection, the concentration of MDA decreased and the concentration of GSH and LZM increased compared with the control groups. We also detected EGCG concentration in grass carp plasma and kidney using HPLC with electrochemical detection after intraperitoneal injection at a dose of 150mg/kg. The concentration of EGCG in the plasma and kidney reached the highest levels (20μg/ml and 1.5μg/ml) about 12hr after injection and then decreased. Overall, EGCG is a safe, effective product that could inhibit GCRV infection and improve immunoactivity in aquaculture.

The anti-hyperuricemic effect of epigallocatechin-3-gallate (EGCG) on hyperuricemic mice

Epigallocatechin-3-gallate (EGCG), a major constituent of green tea catechin, has been used for antioxidant. This study aimed to evaluate the antihyperuricemic activity of EGCG on hyperuricemic mice. We demonstrated that serum uric acid (UA) level was decreased significantly with dose-dependence by EGCG treated with 10, 20, and 50mg/kg. Compared with the model, data on blood urea nitrogen (BUN) supported that there was significance with high dose of EGCG (50mg/kg). Levels of serum creatinine (Cr) in each EGCG-treated group were decreased but not significant; the activities of hepatic xanthine oxidase (XOD) and adenosine deaminase (ADA) in high dose groups' EGCG were notably lower than those of model group. EGCG could downregulate the renal mRNA expression levels of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) on hyperuricemic mice. These results presented that EGCG had obvious hypouricemic and renal protective effects on hyperuricemic mice. Our data may have a potential value in clinical practice in the treatment of hyperuricemia.

Epigallocatechin-3-gallate enhances key enzymatic activities of hepatic thioredoxin and glutathione systems in selenium-optimal mice but activates hepatic Nrf2 responses in selenium-deficient mice

Selenium participates in the antioxidant defense mainly through a class of selenoproteins, including thioredoxin reductase. Epigallocatechin-3-gallate (EGCG) is the most abundant and biologically active catechin in green tea. Depending upon the dose and biological systems, EGCG may function either as an antioxidant or as an inducer of antioxidant defense via its pro-oxidant action or other unidentified mechanisms. By manipulating the selenium status, the present study investigated the interactions of EGCG with antioxidant defense systems including the thioredoxin system comprising of thioredoxin and thioredoxin reductase, the glutathione system comprising of glutathione and glutathione reductase coupled with glutaredoxin, and the Nrf2 system. In selenium-optimal mice, EGCG increased hepatic activities of thioredoxin reductase, glutathione reductase and glutaredoxin. These effects of EGCG appeared to be not due to overt pro-oxidant action because melatonin, a powerful antioxidant, did not influence the increase. However, in selenium-deficient mice, with low basal levels of thioredoxin reductase 1, the same dose of EGCG did not elevate the above-mentioned enzymes; intriguingly EGCG in turn activated hepatic Nrf2 response, leading to increased heme oxygenase 1 and NAD(P)H:quinone oxidoreductase 1 protein levels and thioredoxin activity. Overall, the present work reveals that EGCG is a robust inducer of the Nrf2 system only in selenium-deficient conditions. Under normal physiological conditions, in selenium-optimal mice, thioredoxin and glutathione systems serve as the first line defense systems against the stress induced by high doses of EGCG, sparing the activation of the Nrf2 system.

Gene regulation mediated by microRNAs in response to green tea polyphenol EGCG in mouse lung cancer.

BackgroundEpigallocatechin-3-gallate (EGCG) has been demonstrated to inhibit cancer in experimental studies through its antioxidant activity and modulations on cellular functions by binding specific proteins. We demonstrated previously that EGCG upregulates the expression of microRNA (i.e. miR-210) by binding HIF-1α, resulting in reduced cell proliferation and anchorage-independent growth. However, the binding affinities of EGCG to HIF-1α and many other targets are higher than the EGCG plasma peak level in experimental animals administered with high dose of EGCG, raising a concern whether the microRNA regulation by HIF-1α is involved in the anti-cancer activity of EGCG in vivo.ResultsWe employed functional genomic approaches to elucidate the role of microRNA in the EGCG inhibition of tobacco carcinogen-induced lung tumors in A/J mice. By analysing the microRNA profiles, we found modest changes in the expression levels of 21 microRNAs. By correlating these 21 microRNAs with the mRNA expression profiles using the computation methods, we identified 26 potential targeted genes of the 21 microRNAs. Further exploration using pathway analysis revealed that the most impacted pathways of EGCG treatment are the regulatory networks associated to AKT, NF-κB, MAP kinases, and cell cycle, and the identified miRNA targets are involved in the networks of AKT, MAP kinases and cell cycle regulationConclusionsThese results demonstrate that the miRNA-mediated regulation is actively involved in the major aspects of the anti-cancer activity of EGCG in vivo.

The activity of catechol-O-methyltransferase (COMT) is not impaired by high doses of epigallocatechin-3-gallate (EGCG) in vivo

Catechol-O-methyltransferase (COMT) inactivates many endogenous and exogenous compounds by O-methylation. Therefore, it represents a major enzyme of the metabolic pathway with important biological functions in hormonal and drug metabolism. The tea catechin epigallocatechin-3-gallate (EGCG) is known to inhibit COMT enzymatic activity in vitro. Based on beneficial in vitro results, EGCG is extensively used in human intervention studies in a variety of human diseases. Owing to its low bioavailability, rather high doses of EGCG are frequently applied that may impair COMT activity in vivo. Enzymatic activities of four functional COMT single-nucleotide polymorphisms (SNPs) were determined in red blood cells (RBCs) in 24 healthy human volunteers (14 women, 10 men). The subjects were supplemented with 750mg of EGCG and EGCG plasma levels and COMT enzyme activities in erythrocytes were measured before and 2h after intervention. The homozygous Val→Met substitution in the SNP rs4680 resulted in significantly decreased COMT activity. Enzymatic COMT activities in RBCs were also affected by the other three COMT polymorphisms. EGCG plasma levels significantly increased after intervention. They were not influenced by any of the COMT SNPs and different enzyme activities. Ingestion of 750mg EGCG did not result in impairment of COMT activity. However, COMT activity was significantly increased by 24% after EGCG consumption. These results indicate that supplementation with a high dose of EGCG does not impair the activity of COMT. Consequently, it may not interfere with COMT-mediated metabolism and elimination of exogenous and endogenous COMT substrates.

Effect of Epigallocatechin-3-Gallate on the In Vitro Developmental Potential of Porcine Oocytes and Embryos Obtained Parthenogenetically and By Somatic Cell Nuclear Transfer

The present study aimed to investigate the effects of epigallocatechin-3-gallate (EGCG) on the in vitro development of porcine oocytes, parthenogenetic activation embryos (PA), and somatic cell nuclear transfer (SCNT) embryos. In Experiment 1, 0 (control), 10, 30, and 50 μg/mL EGCG were added to in vitro maturation (IVM) medium to explore the effect of EGCG on IVM of pig oocytes. The matured oocytes were then used to produce PA and SCNT embryos. Either for nuclear maturation of oocytes or for the rates of cleavage and blastocyst of PA and SCNT embryos, no significant difference was found among all groups. However, the total cell number per cloned blastocyst was significantly lower in blastocysts derived from oocytes matured in 50 μg mL EGCG (P<0.05) as compared with the other groups. In Experiment 2, we cultured pig SCNT and PA embryos in medium containing various concentrations of EGCG to examine the effect of EGCG on preimplantation development. The cleavage and blastocyst rates and the total cell number per blastocyst did not significantly differ between PA and SCNT embryos among all groups. However, the reactive oxygen species level was significantly lower in the PA embryos cultured in 10 μg mL EGCG than the other groups (P<0.05). Our results suggest that high doses of EGCG in IVM are harmful to the oocytes as evidenced by the decreased quality of SCNT embryos, and EGCG has no beneficial effects on in vitro development of pig cloned embryos.

Effect of green tea and its polyphenols on mouse liver

Increased consumption of green tea (GT) without enough scientific data has raised safety concerns. Epigallocatechin 3-gallate (EGCG) is the most prominent polyphenol of GT that has antioxidant activity. However, higher doses of EGCG have been shown to cause liver injury. This study was initiated to determine the effect of GT extracts in a mouse model. We also investigated the effects of EGCG in normal and health-compromised mice. Different doses of GT fractions and EGCG were administered for 5days to mice. Also, a single dose of lipopolysaccharide (LPS) was combined with EGCG in order to investigate its effect in the presence of fever. Plasma ALT and ALP levels were determined along with liver histopathology. Combining a single high IG dose of EGCG with a single IP dose of LPS initiated liver injury. Furthermore, repeated administration of high IG doses of EGCG showed mild liver injury, but it was augmented under febrile conditions induced by LPS. This study confirms the safety of reasonable consumption of GT over a short term. However, it highlights a caution that high doses of EGCG can lead to mild liver injury, and this may be markedly enhanced under febrile conditions.

Inhibition of inducible nitric oxide synthase expression and cell death by (−)-epigallocatechin-3-gallate, a green tea catechin, in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson’s disease

The aim of this study was to investigate the involvement of inducible nitric oxide synthase (iNOS) in the action of (−)-epigallocatechin-3-gallate (EGCG), a potential neuroprotective agent against Parkinson’s disease (PD), and to test for toxicity resulting from high doses of EGCG. EGCG was administered to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice at two different doses (10 mg/kg and 50 mg/kg). EGCG treatment reduced the neuronal death rate to less than 50%. The level of iNOS expression in the MPTP group was 20% higher than that seen in the control group, but in the EGCG groups, iNOS expression was reduced to the level observed in the negative control group. The two doses of EGCG were equally beneficial for cell rescue, and no toxicity was observed with the higher dose. Inhibition of iNOS may be an important mechanism underlying the prevention of MPTP toxicity, and EGCG may potentially be a neuroprotective agent against PD.