| Outcome Measures: |
Primary: To study the effect of Linagliptin on insulin sensitivity by performing euglycemic hyperinsulinemic clamp in patients with type 2 diabetes mellitus., Hyperinsulinemic euglycemic clamp of 2 hours duration will be done at baseline and after 6 months of treatment in all patients. Medications taken by the patient will be omitted on the day of test.After an overnight fast of 10 hours, intravenous catheter will be inserted, under sterile precautions, into the antecubital vein for infusion of insulin and dextrose solutions, while another catheter will be inserted in an anti-flow direction into the dorsal vein of the contralateral hand for arterialized blood sampling. An insulin infusate of 300 mU/ml will be administered at a constant rate, after an initial priming dose, while a 25 percent dextrose solution is administered at varying rates to maintain blood glucose at 90 mg/dl. Blood glucose will be analyzed by a bedside glucose analyzer every 5 minutes. M value, a measure of glucose utilisation will be calculated during the steady state (last 30 minutes of the test), 6 months | Secondary: To study the effects of Linagliptin on glycemic control and beta cell function in patients with type 2 diabetes mellitus 6 months, Fasting and 2 hour postprandial blood glucose will be at baseline and after 6 months of treatment. HbA1C will be done at baseline and after 3 and 6 months. HOMA-IR and HOMA-β will be done at baseline and after 6 months. Patients will also be subjected to a mixed meal test at baseline and at 6 months. Mixed meal test will be done 3-7 days after clamp study. After an overnight fast of 10 hours, patients will be given standardized mixed meal, 2.5 g/ kg. (Ensure, Abbott Nutrition, Abbott Laboratories) Medications normally taken by the subject in the morning will be administered 20 min prior to the start of the test meal. Samples for glucose, insulin, C-peptide and glucagon-like peptide-1 (GLP-1) will be taken at 0,30,60,90,120,150 and 180 minutes following the ingestion of meal. Total area under curves for glucose, insulin, C-peptide and GLP-1 from pre meal to 180 min will be calculated using the trapezoidal rule., 6 months | Other: To study the effect of voglibose on glucagon like peptide1 (GLP1) secretion and insulin resistance in patients with type 2 diabetes mellitus 6 months, Patients will be subjected to mixed meal test and a hyperinsulinemic euglycemic clamp study at baseline and after 6 months of treatment., 6 months
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