To investigate the effect of Dipeptidyl Peptidase 4 Inhibition on wound healing in patients with diabetic foot ulcers, the investigators randomly divided the participants into two groups: saxagliptin with regular treatment group，placebo with regular treatment group. The clinical data are collected at the given time point. This study aimed to observe the potential protective effect of DPP4i on diabetic ulcers.

Groups:

Diabetic ulcers, saxagliptin + Regular treatment.

Diabetic ulcers, placebo + Regular treatment.

Time Point:

Initial treatment;

Post-treatment ( 1w );

Post-treatment ( 2w );

Post-treatment ( 4w );

Completely healed.

Inclusion Criteria:

• Diagnosis of diabetes mellitus according to World Health Organization criteria ( treatment with insulin or an oral hypoglycemic agent, twice random glucose measurements major than 200 mg/dl, or a fasting glucose major than 140 mg/dl)
• Ulcer located on the legs or feet, stage III or IV (Wagner Classification System)
• The subject agrees to comply with study protocol requirements and all follow up visit requirements.

Exclusion Criteria:

• Uncontrolled diabetes
• Ulcer infection
• Non-diabetic ulcers Orthopedic or neuromuscular pathologic conditions

age，the grade of the diabetic ulcers, sex, diabetes duration, healing time, treatment. ect