During the natural progression of fatty liver disease, liver enzyme levels also fluctuate, and around 20% of patients with NAFLD have substantial changes in liver enzyme levels, with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels remaining within the normal range or being modestly elevated (1.5–2 times the upper limit of normal) [23]. This evidence concerns the gene GPT and fatty liver disease.