Systematic review of metformin versus vitamin E in treatment of nonalcoholic fatty liver disease

ObjectiveTo compare the clinical efficacy and adverse effects of metformin versus vitamin E in the treatment of nonalcoholic fatty liver disease (NAFLD). MethodsRandomized controlled trials (RCTs) of NAFLD treatment with metformin and vitamin E, which were published before April 10, 2014, were retrieved from international and domestic biomedical databases including the PubMed, EMbase, Cochrane Library, Web of Science, CNKI, WANFANG, VIP, and CBM. Clinical trials that met the inclusion criteria were chosen for meta-analysis. ResultsFour RCTs were included, of which three were published in English and one in Chinese. Meta-analysis data showed that metformin had a significantly higher effective rate than vitamin E in terms of serum alanine aminotransferase (ALT) alternation post oral treatment (P＜0.0001). There were no significant differences in body mass index (BMI) and serum aspartate aminotransferase (AST), fasting blood glucose (FBG), and triglyceride (TG) levels post oral treatment (P=0.30, 0.39, 0.82, and 0.74, respectively). Liver biopsy showed that after metformin treatment, the alterations in fatty degeneration and lobular inflammation scores, as well as balloon-like changes, were less than those post vitamin E treatment. Regarding clinical safety, metformin effectively reduced serum ALT and gamma-glutamyl transferase levels without causing hepatocyte damage (P=0.008 and 0.01, respectively). Only one RCT mentioned the occurrence of mild diarrhea and abdominal pain or discomfort in the metformin group, but there was no significant difference from the vitamin group. ConclusionAmong NAFLD patients, metformin reduces serum ALT levels more significantly than vitamin E, while the latter has its advantage in improving the results of liver biopsy. However, these two drugs have no significant differences in reducing BMI and AST, FBG, and TG levels. This study included limited numbers of original references and patients, and it might involve selection and implementation biases. RCTs of higher quality are expected to provide more effective evidence for assessing the clinical efficacy and adverse reactions of metformin versus vitamin E