Objective Protective effect of theanine on alcohol-induced liver injury in mice was investigated.

Method Male Kunming mice were randomly divided into groups of blank control, injury model, positive control, and theanine treatments. Other than the control group, an alcohol-induced liver injury model was included in each group. In the treatment groups, low-, medium-, and high doses of theanine were administered to determine the protective effect on the alcohol-induced injuries in the mice. Conditions of the skin, fur, vitality, and movements of the mice were observed. Serum liver function indices, i.e., alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as blood lipid indices, i.e., triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), were monitored. Changes in liver morphology were examined by means of pathological sections. And liver tissue antioxidant indices including superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) were determined.

Result Compared with the control group, the mice in the injury model group showed deteriorated general conditions and significantly increased serum ALT and AST activities and TG, TC, and LDL-C contents (P＜0.01) but significantly decreased HDL-C content (P＜0.01), as well as in the liver, apparent hepatic steatosis and inflammatory cell infiltration, declined SOD activity, escalated MDA, and lowered GSH (P＜0.01). In comparison with the model group, the mice in both the treatment and the positive control groups exhibited improved general conditions with significantly decreased activities on serum ALT and AST and contents of TG, TC, and LDL-C, significantly elevated HDL-C (P＜0.05 for the treatment group and P＜0.01 for the positive control group), alleviated hepatic steatosis and inflammatory liver cell infiltration to varying degrees, increased SOD activity and MDA content, and reduced GSH (significantly at P＜0.05 for the treatment group and at P＜0.01 for the positive control group).

Conclusion Theanine exerted a protective effect against the alcohol-induced liver injury with the enhancement of antioxidant capacity, alleviation of oxidative damage, and amelioration of lipid metabolism disorders in mice.