A key point to have in mind is the need for metabolic markers to elucidate which patients with early steatosis will suffer NAFLD and which will progress to an advanced form of liver disease; in this regard, phosphoglucose isomerase, a protein secreted in serum/plasma described in preclinical and clinical studies, is a promising fatty liver disease marker to discern between NAFLD and NASH [54,55]. The gene discussed is GPI; the disease is metabolic dysfunction-associated steatotic liver disease.