Metforminalleviates Acetamionphen-induced Toxic Hepatitis

Objective: Metformin is one of the most frequently used drugs for the treatment of type Ⅱ diabetes. Recent studies also found that metformin(MET) had anti-oxidative and anti-inflammatory activities. MET performs its hypoglycemic, anti-oxidative and anti-inflammatory effects mainly through AMP activated protein kinase(AMPK). The toxic hepatitis induced by acetaminophen(APAP) is a widely used animal model. Toxic hepatitis induced by APAP is initiated with the metabolism of APAP and the formation of toxic production N-acetyl-p-benzo-quinone imine(NAPQI) in hepatic cell. NAPQI causes oxidative stress, activates inflammatory response and finally, leads to toxic hepatitis. The present study investigated the potential protective effects of MET on APAP-induced toxic hepatitis and its relationship with AMPK.Methods: Acute toxic hepatitis was induced in male Kunming mice(6~7 weeks old and weighted 18~20 g) with intraperitoneal injection of APAP(350 mg/kg, dissolved in pre-warmed PBS, i.p.). In order to investigate the potential protective effects, metformin(400 mg/kg, dissolved in PBS, i.p.) was administered 0.5 h prior to APAP. In order to investigate the relationship between metformin and AMPK, one group of mice received the inhibitor of AMPK Dorsomorphin(15 mg/kg, dissolved in ethylene glycol, i.p.) 0.5 h prior to MET, the other group of mice were administered with the activator of AMPK A-769662(30 mg/kg, dissolved in ethylene glycol, i.p.) 0.5 h prior to APAP. The mice were killed at 8 h after APAP injection. The blood samples were collected for the determination of aminotransferases(AST and ALT) and proinflammatory cytokines(TNF-α and IL-6). The liver tissues were collected for the measurement of malondialdehyde(MDA) content and catalase(CAT) activity. In addition, the formalin-fixed slices were stained with hematoxylin & eosin for morphological evaluation.Result: These experimental data indicated that treatment with MET significantly suppressed the elevation of plasma aspartate transaminase(AST) and alanine transaminase(ALT), reduced the hepatic content of malondialdehyde(MDA), inhibited the production of tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6), attenuated the histopathological abnormalities in APAP-exposed mice. Co-treatment with AMPK inhibitor dorsomorphin could not block the suppressive effects of MET on APAP-induce elevation of ALT and AST. Consistently, treatment with AMPK activator A-769662 could not mimic the suppressive effects of MET on ALT and AST. Recent studies have found the new correlation between MET and CAT, the present study also found that treatment with MET but not A-769662 increased the activity of CAT in liver tissue, the stimulatory effects of MET on CAT could not blocked by dorsomorphin. So MET upregulates the activity of CAT via an AMPK independent manner.Conclusion: Our experimental data indicated that MET protected against APAP-induced acute liver damage in mice. These effects might attribute to its stimulatory effect on CAT and the upregulated anti-oxidative capacity of hepatocyte, these effects did not depend on AMPK. According to the reported literature and our experimental data, oxidative damage plays crucial roles in APAP-induced liver damage. Therefore, MET reduced liver injury by enhancing CAT activity, which has certain enlightenment for acute severe hepatitis prevention.