Thus, we identified a predictive gene signature in human liver that could be used in patient clinical follow-up, as well as in clinical trials focused on the development of drugs to treat NASH patients, including two main genes, FABP4 and MMP9, the proteins of which could be quantified in the serum and used as non-invasive prognostic markers for NAFL and NASH progression. Here, FABP4 is linked to non-alcoholic fatty liver.