This study evaluated the efficacy of epalrestat in diabetic peripheral neuropathy and its effects on the central nervous system in diabetic peripheral neuropathy subjects.

Inclusion Criteria:

1. Patients aged 18 to 65 years (to the date of screening)；
2. A clear history of type 2 diabetes (using the 1999 WHO diabetes diagnostic criteria) with a course of disease > 6 months;
3. HbA1c < 7%;
4. Two or more of the following five tests are abnormal: abnormal temperature perception; Nylon wire for hypoesthesia or disappearance of the foot; Abnormal vibration sense; Ankle reflex disappeared; Two or more nerve conduction velocities were reduced;
5. Have not used mecobalamin, epalrestat, lipoic acid or high-dose glucocorticoid in the recent (3 months) period, or have not been involved in other treatment of the same disease within 3 months prior to the study;

Exclusion Criteria:

1. Neuropathy caused by other causes, such as cervical and lumbar lesions, cerebral infarction, etc.;
2. With acute metabolic complications of diabetes, such as ketoacidosis, lactic acidosis, diabetes hyperotonic state, etc;
3. Severe cardiovascular and cerebrovascular diseases , pulmonary heart disease or pulmonary insufficiency, renal failure, severe dyslipidemia, poorly controlled hypertension, severe hepatitis.
4. Those with a history of malignant tumor or wasting diseases such as tuberculosis;
5. Contraindications to MRI scanning: such as internal (especially oral) metal implants, claustrophobia, etc;
6. Poor compliance or serious side effects;
7. pregnant female.