RBP4 and metabolic dysfunction-associated steatohepatitis: Clinical studies suggest that serum levels of leptin, resistin, adiponectin, tumor necrosis factor α (TNF α), interleukin-6 (IL-6), visfatin, CK-18, and retinol binding protein 4 (RBP4) differ among patients with NAFLD and NASH and healthy controls [24–26].