Improving Insulin Resistance to Treat Non-Alcoholic Fatty Liver Disease: A Pilot Study

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the United States and a common cause of unexplained mildly elevated serum aminotransferase levels. NAFLD, initially felt to be benign, is now known to potentially progress to cirrhosis and its complications, including the development of liver cancer. NAFLD is strongly correlated with Type 2 Diabetes, insulin resistance, and the metabolic syndrome (1-6). It is hypothesized that the pathogenesis of hepatic injury in NAFLD is due to insulin resistance and the oxidative stress associated with obesity and metabolic syndrome (7). No adequate medical treatment has been shown to be effective for the treatment of NAFLD. Several studies (8-22) have evaluated the effect of metformin in patients with NAFLD in relation to insulin resistance, Homeostatic Model Assessment Insulin Resistance Index (HOMA-IR) values, aminotransferase levels, liver morphology, and histological improvement with treatment. These studies however have shown discrepant results with relation to aminotransferase levels and only a few studies have been able to evaluate histological improvement with follow-up biopsies. There have been no studies focusing specifically on the pre-diabetic population. These patients who are at an increased risk of progressing to diabetes may exhibit a different response to treatment with metformin than non-diabetic or diabetic patients. All the studies support the fact that metformin has a beneficial effect on improving insulin resistance and decreasing the incidence of metabolic syndrome, but there is no consensus thus far on its influence on NAFLD. The majority of published studies were limited by small sample size. Randomized controlled trials with adequate sample size and of longer duration are needed as well as studies assessing endpoints such as liver morphology and histology. The results of this pilot study are significant in that metformin may be a relatively safe and inexpensive way, in addition to lifestyle modifications, to treat NAFLD. The results of this pilot study will pave the way for the larger power, longer duration study required to answer this question.