MTHFR and folate deficiency: We found that folate deficiency can simultaneously increase the expression of miR-22 and miR-149, while miR-22 and miR-149 regulate MTHFR levels, and may act as an indirect methyl donor in the one carbon metabolism cycle and play an important role in maintaining methylation levels throughout the genome by regulating MTHFR, thereby regulating methylation level in the entire genome and genes.