Diabetic Cardiomyopathy (DCM) is disease of myocardial structure and function which is independent of hypertension, coronary heart disease, heart valve abnormalities, and other types of heart disease. DCM affects approximately 12% of diabetics and also appeared in some patients with well-controlled blood glucose. There is no specific and effective diagnostic method of DCM currently. Since it is well known that the dysfunction of myocardial metabolism caused by hyperglycemia and insulin resistance induces DCM, the method of evaluation of the metabolism will assist the diagnosis of DCM.

Nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) is one of important coenzymes involved in biological metabolism. Fluorescence lifetime microscopy (FLIM) can detect the metabolic status based on the fluorescence characteristics of NAD(P)H. Previous studies have reported that NAD(P)H fluorescence lifetime can be used to assess the metabolic status of living cardiomyocytes cultured in vitro, and metabolism changes related to myocardial infarction and heart failure in rats. the investigators detected the metabolic status by label-free FLIM on the myocardial tissues and blood plasma in a rat model of type 2 diabetic cardiomyopathy, and found FLIM could provide valuable information about the myocardial metabolism by detecting the NAD(P)H fluorescence lifetime of blood plasma.

Recently, The investigators have explored the method of the FLIM in clinical study. The investigators used FLIM to compare the NAD(P)H fluorescence lifetime of blood plasma in healthy participants, type 2 diabetic patients with normal diastolic function and with diastolic dysfunction. The results showed that the NAD(P)H fluorescence life parameter of a2 was lower in type 2 diabetic patients with diastolic dysfunction (30.5±2.7%) than in healthy participants (41.5±4.8%) and type 2 diabetic patients with normal diastolic function (37.8±3.7%). Therefore, The investigators propose FLIM can provide valuable information about the myocardial metabolism, and it can be used as a non-invasive, label-free, and rapid screening method of diagnosis of DCM.

In this study, the investigators will recruit 243 patients with type 2 diabetes and divide them into two groups: normal diastolic function group (DM Group) and diastolic dysfunction group (DCM Group), based on the symptoms, laboratory examination and echocardiographic results. Then FLIM will be applied to detect the NAD(P)H fluorescence characteristics of venous blood of all patients. After that, the correlation between the parameters of diastolic function (E peak, E/E' ratio, left atrial volume, NT-proBNP) and the parameters of metabolism status (NAD(P)H fluorescence life parameter of a2 and the ratio of bound state/free state NAD(P)H) will be analyzed. This study will verify FLIM is helpful to diagnose DCM.

Inclusion Criteria:

1. Male or female, aged 18-80 years old;
2. Echocardiography showed that the cardiac structure was normal and the left ventricular ejection fraction was more than 50%;
3. patients with type 2 diabetes mellitus;
4. Body mass index (BMI) was 20-25 kg / m2 in male and 19-24 kg / m2 in female;
5. No other drugs except hypoglycemic drugs were taken in one month;
6. Sign informed consent form before entering this study.

Exclusion Criteria:

1. Patients with type 1 diabetes mellitus;
2. Patients with diabetic ketoacidosis in the past;
3. Patients with coronary heart disease or with myocardial ischemia indicated by ECG;
4. EGFR < 60ml / min / 1.73m2 in recent one month;
5. Chronic liver disease, or the levels of alanine aminotransferase and glutamic oxaloacetic transaminase were more than 3 times of the upper limit of the normal before enrollment;
6. Abnormal thyroid function;
7. Abnormal tumor index;
8. Dyslipidemia;
9. Pregnant and lactating women;
10. Allergy to contrast media.

type 2 diabetes patients, divided into two groups, based on the diastolic funciton