To investigate the expression of serum S-adenosylhomocysteine (SAH), interleukin-1β (IL-1β), serum homocysteine (Hcy), tumor necrosis factor-α (TNF-α) and brain derived neurotrophic factor (BDNF) in coronary heart disease and their relationship with the degree of coronary artery disease. Here, BDNF is linked to coronary artery disorder.