There were no significant differences in the mean concentrations of occludin, claudin 5, and ZO-1 between patients with diabetes mellitus, lipid disorders, atrial fibrillation, myocardial infarction, coronary heart disease, and ipsilateral internal carotid artery stenosis (>70%) and not suffering from the above diseases. The gene discussed is CLDN5; the disease is atrial fibrillation.