ALDH1A1 and metabolic dysfunction-associated steatohepatitis: Following the oxidation of retinol to retinaldehyde, ALDH1A1, ALDH1A2 and ALDH1A3 are the enzymes responsible for the second and irreversible step in the oxidation of retinaldehyde to retinoic acid.[7] The downregulation of ALDH1A1 and ALDH1A3 in patients with SS and NASH compared to LD may reduce the amounts of retinoic acid in the liver and consequently alter interactions with RAR and RXR.