PNPLA3 and fatty liver disease: Several genes and related pathways are involved in the choline/1-carbon metabolism and have been associated with increased risk of NAFLD and liver steatosis, including, methyl-tetrahydrofolate (MTHFR), choline dehydrogenase (CHDH), betaine-homocysteine methyltransferase (BHMT), PEMT, solute carrier family 44 member 1 (SLC44A1), PNPLA3, and ATP-binding cassette subfamily B member 4 (ABCB4) [22].