Effects of Theanine on Alcohol Metabolism and Hepatic Toxicity

Hepatoprotective effects and mechanisms of l-theanine and epigallocatechin gallate combined intervention in alcoholic fatty liver rats

BACKGROUND

Chronic excessive alcohol consumption can lead to alcoholic fatty liver, posing substantial health risks. l-Theanine (LTA) and epigallocatechin gallate (EGCG) in tea exert antioxidant and hepatoprotective effects. However, the combined effects of LTA and EGCG on rats with alcoholic fatty liver, and the underlying mechanisms of such effects, remain unclear. In this study, Sprague Dawley (SD) rats were fed with alcohol for 6 weeks to induce alcoholic fatty liver. Subsequently, for another 6 weeks, the rats were administered LTA (200 mg kg-1 day-1), EGCG (200 mg kg-1 day-1), or a combination of LTA with EGCG (40 mg kg-1 day-1 l-Thea +160 mg kg-1 day-1 EGCG), respectively.

RESULTS

The combined use of LTA and EGCG for alcoholic fatty liver disease had more significant effects than their individual administration. This combination reduced the activity of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) as well as the levels of hepatic triglyceride (TG), malondialdehyde (MDA), and reactive oxygen species (ROS) in the rats. The combined intervention also increased hepatic superoxide dismutase (SOD) and glutathione peroxidase activity. Reductions in hepatic fat accumulation and inflammatory responses were observed. The mechanism underlying these effects primarily involved the inhibition of fatty acid synthesis and the alleviation of lipid peroxidation through the downregulation of the mRNA and protein expression of TNF-α, SREBP1c, and CYP2E1 and the upregulation of the mRNA and protein expression of ADH1, ALDH2, Lipin-1, PPARαPPARα, AMPK, and PGC-1α, thereby promoting the oxidative decomposition of fatty acids and reducing the synthesis of cholesterol and glucose.

CONCLUSION

l-Theanine and EGCG appear to be able to alleviate alcoholic fatty liver by modulating lipid metabolism and ameliorating oxidative stress, indicating their potential as natural active ingredients in anti-alcoholic fatty liver food products. © 2024 Society of Chemical Industry.

L-Theanine Protects H9C2 Cells from Hydrogen Peroxide-Induced Apoptosis by Enhancing Antioxidant Capability

BACKGROUND L-theanine is a non-protein amino acid in green tea, and its hepatoprotection and neuroprotection have been verified. However, whether L-theanine can prevent cardiomyocytes from apoptosis is unclear yet. This study evaluated the protective effects of L-theanine on H2O2-induced heart injury in vitro. MATERIAL AND METHODS The certified H9C2 cells were pretreated with L-theanine (0 mM, 4 mM, 8 mM, and 16 mM) for 24 h, followed by 160 µM H2O2 solution for 4 h. The cell viability and antioxidant indices were assayed. Quantitative evaluation of apoptosis was performed by flow cytometric analysis. Nuclear morphology of the cells was monitored by 4',6-diamidino-2-phenylindole staining. Expression of Caspase-3, poly ADP-ribose polymerase (PARP), c-Jun N-terminal kinase (JNK), and mitogen-activated protein kinase p38 was assayed by Western blot. RESULTS Compared to the H2O2 treatment, all doses of L-theanine treatments increased the cell viability, glutathione level, and the activities of glutathione peroxidase and superoxide dismutase (P<0.001). The contents of reactive oxygen species, nitric oxide, and oxidized glutathione were decreased by L-theanine treatments (P<0.001). Meanwhile, L-theanine treatments decreased the apoptosis ratio of H2O2-induced H9C2 cells (P<0.001). Pro-Caspase-3 expression was upregulated and cleavaged-PARP expression was inhibited by L-theanine (P<0.001). However, the phosphorylation of JNK and p38 was not affected by L-theanine treatments (P>0.05). CONCLUSIONS These data indicate that L-theanine pretreatment prevents H2O2-induced apoptosis in H9C2 cells, probably via antioxidant capacity improvement. Therefore, it might be a promising potential drug candidate for prophylaxis of ischemia/reperfusion-induced heart diseases.

Green tea extract therapy diminishes hepatic fibrosis mediated by dual exposure to carbon tetrachloride and ethanol: A histopathological study

The aim of the present study was to investigate the hepatoprotective effect of green tea extract (GTE) against the hepatic fibrosis induced by carbon tetrachloride (CCl₄), ethanol, and dual exposure to CCl₄ plus ethanol in rats. In particular, an investigation of the three-dimensional architecture was conducted using scanning electron microscopy. Various techniques revealed that hepatic fibrosis with intermingled fibers was located between cells in the CCl₄, ethanol and combined CCl₄ plus ethanol groups. The hepatic fibrosis differed among the ethanol, CCl₄ and CCl₄ plus ethanol groups in terms of the type, thickness and distribution of fibers. The fibrotic lesions virtually disappeared in all the groups after 25 days of treatment with GTE, returning the architecture of the liver tissue to its normal status. The rats were also found to regain normal body weight and fur color, which had earlier been discolored due to weight loss. The autopsy results also showed that the animal livers returned to the normal shape and color. GTE demonstrated the same clear action in attenuating the hepatofibrosis for all three inducing treatments, by impairing collagen fibers, eliminating lipid peroxidation and returning the liver architecture to normal. GTE presents a safe therapeutic strategy for hepatic fibrosis.

Protective effect of L-theanine on carbon tetrachloride-induced acute liver injury in mice

We studied effects of L-theanine, a unique amino acid in tea, on carbon tetrachloride (CCl(4))-induced liver injury in mice. The mice were pre-treated orally with L-theanine (50, 100 or 200 mg/kg) once daily for seven days before CCl(4) (10 ml/kg of 0.2% CCl(4) solution in olive oil) injection. L-theanine dose-dependently suppressed the increase of serum activity of ALT and AST and bilirubin level as well as liver histopathological changes induced by CCl(4) in mice. L-theanine significantly prevented CCl(4)-induced production of lipid peroxidation and decrease of hepatic GSH content and antioxidant enzymes activities. Our further studies demonstrated that L-theanine inhibited metabolic activation of CCl(4) through down-regulating cytochrome P450 2E1 (CYP2E1). As a consequence, L-theanine inhibited oxidative stress-mediated inflammatory response which included the increase of TNF-α and IL-1β in sera, and expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in livers. CCl(4)-induced activation of apoptotic related proteins including caspase-3 and PARP in mouse livers was also prevented by L-theanine treatment. In summary, L-theanine protects mice against CCl(4)-induced acute liver injury through inhibiting metabolic activation of CCl(4) and preventing CCl(4)-induced reduction of anti-oxidant capacity in mouse livers to relieve inflammatory response and hepatocyte apoptosis.

l-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes

l-Theanine is a unique amino acid in green tea. We here evaluated the protective effects of l-theanine on ethanol-induced liver injury in vitro and in vivo. Our results revealed that l-theanine significantly protected hepatocytes against ethanol-induced cell cytotoxicity which displayed by decrease of viability and increase of LDH and AST. Furthermore, the experiments of DAPI staining, pro-caspase3 level and PARP cleavage determination indicated that l-theanine inhibited ethanol-induced L02 cell apoptosis. Mechanically, l-theanine inhibited loss of mitochondrial membrane potential and prevented cytochrome c release from mitochondria in ethanol-treated L02 cells. l-Theanine also prevented ethanol-triggered ROS and MDA generation in L02 cells. l-Theanine restored the antioxidant capability of hepatocytes including GSH content and SOD activity which were reduced by ethanol. In vivo experiments showed that l-theanine significantly inhibited ethanol-stimulated the increase of ALT, AST, TG and MDA in mice. Histopathological examination demonstrated that l-theanine pretreated to mice apparently diminished ethanol-induced fat droplets. In accordance with the in vitro study, l-theanine significantly inhibited ethanol-induced reduction of mouse antioxidant capability which included the activities of SOD, CAT and GR, and level of GSH. These results indicated that l-theanine prevented ethanol-induced liver injury through enhancing hepatocyte antioxidant abilities.

Inhibition property of green tea extract in relation to reserpine-induced ribosomal strips of rough endoplasmic reticulum (rER) of the rat kidney proximal tubule cells

The aim of this study was to evaluate the effect of green tea in inhibiting and reversing the nephrotoxicity of reserpine--a potent oxidative stress inducer--which induced cellular kidney damage. Serum biochemical parameters, antioxidant enzyme levels, thiobarbituric acid reactive substances (TBARS) and serum transaminases (glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT)) values and histopathology were systematically evaluated. Reserpine exposure led to increase the oxidative stress and organ injury was significantly observed through biochemical parameters and ultrastructural evaluation. Sprague-Dawely (S.D.) rats were intraperitonealy administered reserpine to induce oxidative kidney damage. Experimental rats were given green tea extract according to the protocol given below. Sixty rats were randomly divided into six groups, with 10 rats in each group. Reserpine was found to cause kidney proximal tubule damage, such as stripping and clustering of ribosomes from the rough endoplasmic reticulum (rER) and demolishing of mitochondrial christae with elevated level of oxidative stress markers, such as TBARS. While the ultrastructural study showed a revival of kidney proximal tubule cells as a result of the administration of green tea extract to rats. We suggest that green tea might elevate antioxidant defense system, clean up free radicals, lessen oxidative damages and protect kidney against reserpine-induced toxicity and thus had a potential protective effect.

Effect of dietary epigallocatechin-3-gallate on cytochrome P450 2E1-dependent alcoholic liver damage: enhancement of fatty acid oxidation

This study was designed to determine whether dietary epigallocatechin-3-gallate (EGCG), the most abundant catechin polyphenol in green tea, can protect the liver from cytochrome P450 2E1 (CYP2E1)-dependent alcoholic liver damage. Compared with an ethanol group, when EGCG was present in the ethanol diet, the formation of a fatty liver was significantly reduced and the serum aspartate transaminase (AST) and alanine transaminase (ALT) levels were much lower. Ethanol treatment significantly elevated hepatic CYP2E1 expression while simultaneously reducing hepatic phospho-acetyl CoA carboxylase (p-ACC) and carnitine palmitoyl-transferase 1 (CPT-1) levels. While EGCG markedly reversed the effect of ethanol on hepatic p-ACC and CPT-1 levels, it had no effect on the ethanol-induced elevation in CYP2E1 expression. EGCG prevents ethanol-induced hepatotoxicity and inhibits the development of a fatty liver. These effects were associated with improvements in p-ACC and CPT-1 levels. The use of EGCG might be useful in treating patients with an alcoholic fatty liver.

Efficacy of theanine is connected with theanine metabolism by any enzyme, not only drug metabolizing enzymes

Theanine increases the antitumor effect of doxorubicin (DOX) with decreasing adverse reaction. We clarified the mechanism by which theanine decreases the adverse reaction of DOX on any metabolizing enzymes of theanine. There was no change in the activity of any CYPs and the cytochrome P450 content by theanine treatment. Namely, it was considered that the decrease of DOX adverse reactions by theanine was not connected with CYP activity. In other words, it is shown that theanine has no effect on the metabolism of other medicines and is safe as a food (tea) or supplement. Glutathione S-transferase activity did not change in the theanine-alone group whereas increased in the theanine and DOX-combined group. These results suggested that theanine combination increased the conjugate with DOX and GSH, promoted the efflux of GS-DOX conjugates from the liver, and decreased DOX concentration in the liver. In medium containing theanine with glutaminase in vitro, glutamate gradually generated, showing that glutaminase reacted with theanine. Furthermore, the generation of glutamate increased by reaction of theanine and gamma-glutamyltranspeptidase (gamma-GTP), showed that gamma-GTP converted theanine to glutamate. It is expected that theanine metabolism occurred by hydrolysis and rearrangement reaction by gamma-GTP in the liver. Namely, it is suggested that the metabolism of theanine mediated by glutaminase and gamma-GTP and the increase of glutamate mediated GSH is important for theanine-induced action. In conclusion, it appeared that theanine does not change the biodistribution of combined drugs but it modulates biodistribution or damage to the relative site of GSH, and shows preventive effects in tissue.