The epigenetic consequences and mechanisms of dysregulated histone methylation, mTOR signaling, and autophagy caused by Hcy and related metabolites, and their roles in Hcy-related diseases, including AD, will provide a fertile field for future systematic studies that are needed to elucidate the roles of Hcy-thiolactone-detoxifying enzymes— PON1, BLMH, and BPHL—in human health and disease. Here, BLMH is linked to Alzheimer disease.