GPT and metabolic dysfunction-associated steatotic liver disease: However, even though such evidence is accumulating, only small numbers and scales of clinical trials with NAC have been conducted in patients with NAFLD and showed significant reduction in serum alanine aminotransferase (ALT) levels by NAC treatment (Gulbahar et al., 2000; Pamuk and Sonsuz, 2003; Khoshbaten et al., 2010).