Inclusion Criteria:  The patient, aged 18-85 years, had undergone coronary angiography and agreed to be enrolled and signed the informed consent.  AMI : according to ST segment elevation myocardial infarction diagnostic criteria.  UAP:  typical chest pain symptoms; negative in markers of myocardial injury; The stenosis of main coronary artery or its main branches is more than 50%  Control:  atypical chest pain symptoms negative in markers of myocardial injury; The stenosis of main coronary artery and its main branches is less than 50%  Exclusion Criteria:  Acute infection or application of antibiotics in the past 3 months; Chronic heart failure; History of inflammatory or absorptive bowel disease and bowel resection; Acute, chronic liver disease or other reasons lead to abnormal liver function (transaminase is more than 5 times of normal value); Renal insufficiency (serum creatinine > 220μml/L or creatinine clearance rate < 30 ml/min); Malignant tumor; Autoimmune diseases; Uninformed patients