MAT2B and congenital secretory chloride diarrhea 1: In conclusion, as an important part of one-carbon metabolism, methionine metabolism is closely related to diverse pathophysiological processes.19 Accumulating preclinical evidence indicates that alterations in the methionine cycle play a pathogenetic role in CLD.38 The switch of MAT1A to MAT2A/MAT2B reduces the levels of SAM, which is an essential factor in fibrosis and liver cancer.129 Preventing or even reversing this transformation will be the direction of future research.