Four of these genes [i.e., the ACE gene, methylenetetrahydrofolate reductase (MTHFR) gene, glutathione peroxidase-1 (GPx-1) gene, and catalase (CAT) gene] have received greater attention, and even meta-analyses are available, with their polymorphisms possibly involved in the increased renin–angiotensin system activity, hyperhomocysteinemia, and reduced defense against oxidative stress [20]. Here, MTHFR is linked to hyperhomocysteinemia.