If you have MTHFR , or think you might , this is the most important connection in this series. MTHFR is a gene mutation that impairs methylation. And methylation is the APLB Glutathione Niacinamide Facial Toner New Mercari MTHFR and Digestion: Methylation Impacts Gallbladder Function Beyond MTHFR PDF) Analysis of MTHFR, CBS, Glutathione, Taurine, and Hydrogen Sulfide Levels in Retinas of Hyperhomocysteinemic Mice