The purpose of this study is to explore the changes of fasting and postprandial cerebral blood flow in patients with type 2 diabetes mellitus. Some studies have proved that non-fasting blood glucose concentration is an independent predictor of ischemic stroke and lacunar infarction. At present, there are differences in cerebral blood flow velocity between diabetic patients and healthy controls. Therefore, it is of certain significance to explore the changes of fasting and postprandial cerebral blood flow in patients with type 2 diabetes mellitus.

In China, due to the aging population and the increase in obesity, the incidence of diabetes is on the rise. Diabetes is the main independent risk factor for cerebrovascular diseases, especially ischemic stroke. Some studies have proved that non-fasting blood glucose concentration is an independent predictor of ischemic stroke and lacunar infarction. Transcranial Doppler (TCD) can evaluate intracranial blood flow patterns real-time and reliably, and provide information about cerebral hemodynamics, cerebrovascular reactivity and various pathological changes. At present, there are some differences in the study of cerebral blood flow velocity in diabetic patients. The purpose of our study is to determine the changes of cerebral blood flow on an empty stomach and 1 hour after meal in patients with type 2 diabetes. In this study, 20 patients with type 2 diabetes mellitus will be selected as the experimental group. 20 healthy volunteers whose sex and age and BMI matched with the experimental group will be selected as the control group. Fasting blood glucose and TCD will be measured in the two groups, and the data of mean flow velocity (Vm), Gosling's pulsatility index (PI) and cerebrovascular reactivity of cerebral artery will be obtained. One hour after drinking 300ml lukewarm water which has dissolved 75g glucose powder, the blood glucose will be detected again and TCD examination will be performed again. Finally, the data will be collected for statistical analysis.

Inclusion Criteria:

• Trial group

  1. Study time: June 1, 2021, to January 1, 2022;
  2. Study site: The First Affiliated Hospital of Shandong First Medical University;
  3. 25-65 years old (including upper and lower limits), male or female;
  4. Meeting the diagnostic criteria of type 2 diabetes (according to 1997 WHO's diagnostic criteria for type 2 diabetes);
  5. Fasting blood glucose < 10 mmol/L;
  6. HbA1c ≤ 11.0%.

• Control group

  1. Study time: June 1, 2021, to January 1, 2022;
  2. Study site: The First Affiliated Hospital of Shandong First Medical University;
  3. Relatively healthy people without type 2 diabetes mellitus diagnosis;
  4. Participants whose sex and age and BMI matched with the experimental group.

Exclusion Criteria:

• Trial group and Control group

  1. Participants with diabetic retinopathy;
  2. Participants with diabetic neuropathy;
  3. Participants with diabetic nephropathy;
  4. Participants have unilateral or bilateral carotid plaque;
  5. Participants have a history of cardio-cerebrovascular disease;
  6. Participants have a history of respiratory disease;
  7. Participants complicated with hypertension;
  8. Participants complicated with hyperlipidemia;
  9. Participants have a smoking history (including previous smoking history);
  10. Participants complicated with malignant tumor.
  11. Participants are currently taking anticoagulants or vasodilators;
  12. Participants do not sign a written informed consent form.

Patients with type 2 diabetes mellitus and healthy volunteers