Metformin in patients with non-alcoholic fatty liver disease: a randomized, controlled trial

The antidiabetic agent metformin is regularly discussed as a promising treatment for non-alcoholic fatty liver disease (NAFLD), which is characterized by insulin resistance. However, the evidence for its beneficial effects is limited, and conflicting reports have been published. The purpose of this study was to conduct a randomized, double-blind, placebo-controlled trial to test whether metformin improves liver histology in patients with non-alcoholic fatty liver disease.

Forty-eight patients with biopsy-proven NAFLD were randomized to treatment with metformin (n=24) or placebo (n=24) for 6 months. A second liver biopsy was obtained in all subjects who completed the trial (n=44). Data analyses are restricted to this group (per-protocol analyses). The primary outcome was changes in histologically assessed liver steatosis. Secondary outcomes were changes in NAFLD activity (NAS)-score, liver steatosis assessed by computed tomography (CT), liver transaminases, body-weight, metabolic variables and inflammatory markers.

No significant differences between treatment with metformin or placebo were observed for changes in liver steatosis, assessed either histologically or by CT, NAS-score, liver transaminases or on markers of insulin resistance or inflammation. In contrast, beneficial effects of metformin were observed on changes in body-weight (p<0.001), serum levels of cholesterol (p=0.004), LDL-cholesterol (p<0.001), glucose (p=0.032) and on HbA1c (p=0.020).

Treatment with metformin for 6 months was no better than placebo in terms of improvement in liver histology in patients with NAFLD. Nevertheless, the use of metformin could still be beneficial in this group as it is associated with a reduction in serum levels of lipids and glucose. (ClinicalTrials.gov number, NCT00303537).