MTRR and coronary artery disorder: Previous studies have pointed out that polymorphisms of genes implicated in the folate–homocysteine pathway were associated with the occurrence of CHD, encompassing methylenetetrahydrofolate reductase (MTHFR) [11,12], cysteine acetylase (CBS) [13], methionine synthase (MTR) [14], and methionine synthase reductase (MTRR) [15].