In type 2 diabetic patients, abnormality in secretion or action of incretin(GLP-1, GIP) is observed. Although controversy still exists, the secretion of GLP-1 is thought to be reduced by 20-30% while GIP secretion is normal or slightly elevated, in type 2 diabetic patients. Various parameters such as the duration of diabetes, the amount of meal and their constitution, gastric bypass surgery, and some antidiabetic drugs affect the secretion of incretin. However, the secretion of GLP-1 and GIP in glucotoxic condition and whether they recover after improvement of glycemic status is not known. The investigators aim to study the effect of intensive insulin treatment in uncontrolled diabetic patients.

Inclusion Criteria:

• type 2 diabetic patients with disease duration of less than 15years

• age of 20-70 years

• BMI 22-27

• HbA1c 9-13%

• patients willing to receive intensive glucose control

• patients who are able to monitor their glucose level at home

  • for normal glucose tolerance group : NGT subjects with same range of age and BMI
  • for early diabetes group : patients with diabetic duration of less than 5 years and HbA1c level less than 7.5% for at least last 6 months

Exclusion Criteria:

• previous history of insulin treatment
• patients taking alpha-glucosidase inhibitor or thiazolidinedione
• serum creatinine >= 1.5 mg/dL
• hemoglobin < 10 g/dL
• AST/ALT greater than 3 times normal range
• ischemic heart disease, congestive heart failure (NYHA grade >=2)
• chronic renal failure, proliferative diabetic retinopathy, CVA
• patients with gastroparesis or taking medications altering gastric motility
• usage of steroid or other agents affecting glucose metabolism
• pregnant or breast-feeding women

1. Subjects with normal glucose tolerance
2. Early diabetic patients with disease duration of less than 5years
3. Uncontrolled diabetic patients