Hyperhomocysteinemia (HHcy), Oxidative Stress, Extracellular and Intracellular Matrix Metalloproteinase, Tissue Inhibitors of Metalloproteinases and Mitophagy: Matrix metalloproteinases (MMPs) and membrane-bound, zinc-dependent endoproteinases are known as collagenases (MMPs-1, -8, and 13), stromelysins (MMP-3 and 10), matrilysins (MMP-7 and -26), membrane-type MMPs (MT-MMPs, MMP-1 to MMP-8), and gelatinases (MMP-2 and 9), and the disintegrin metalloproteinase (including the ADAM). The gene discussed is MMP2; the disease is hyperhomocysteinemia.