A decrease in the activity of gamma-glutamyl transpeptidase and the level of proinflammatory cytokines was observed in patients with nonalcoholic steatohepatitis (NASH) after 4 weeks of L-tryptophan (the precursor of melatonin) administration [63]. The gene discussed is GGTLC1; the disease is metabolic dysfunction-associated steatohepatitis.