It is well known that Long-term hyperglycemia (also known as glucose toxicity) contribute to impairment in islet β-cell function and development of insulin resistance. A growing body of evidence also indicates that this impairment inβ-cell function and insulin action could be restored after hyperglycemia is corrected by short-term intensive insulin therapy. In this study, we are determined to use the golden standard of insulin sensitivity evaluation in vivo-hyperinsulinemia euglycemic glucose clamp-to estimate insulin resistance improvement in patients before and after intensive insulin therapy, investigate first phase insulin secretion to evaluate β-cell function, examine the changes in insulin resistance and insulin secretion resulting from normalization of plasma glucose levels in both lean and obese patients by insulin pump therapy.

Inclusion Criteria:

• Age: 25 to 60 years old
• Duration of diabetes: newly diagnosed type 2 diabetes (duration of diabetes less than 1 year) and haven't taken any antidiabetic medication.
• Fasting blood glucose is above 11.0mmol/L.
• Half of the patients with BMI below 24 and the other half with BMI above 24.

Exclusion Criteria:

• type 1 diabetes mellitus
• type 2 diabetes patients with intercurrent illness (ketoacidosis, infection or any other acute stress)
• Presence of auto-immune disease, hepatic or renal disease or any concomitant disease is not allowed.
• Women who are pregnant, breast feeding or have the intention of becoming pregnant within next 12 months.