Short Insulin Tolerance Test Can Determine the Effects of Thiazolidinediones Treatment in Type 2 Diabetes

PURPOSE The short insulin tolerance test is a simple and reliable method of estimating insulin sensitivity. This study was designed to compare the insulin sensitizing effects of thiazolidinediones (TZDs) on the degree of insulin resistance, determined by a short insulin tolerance test (Kitt) in type 2 diabetic patients. PATIENTS AND METHODS Eighty-three subjects (mean age = 57.87 +/- 10.78) with type 2 diabetes mellitus were enrolled and received daily one dose of rosiglitazone (4 mg) or pioglitazone (15 mg). The mean follow-up duration was 25.39 +/- 9.66 months. We assessed insulin sensitivity using HOMA-IR and the short insulin tolerance test before and after TZDs treatment. RESULTS When we compared patients' characteristics before and after TZDs treatment, the mean fasting glucose level was significantly decreased (183.27 +/- 55.04 to 137.35 +/- 36.42 mg/dL, p < 0.001) and the mean HbA1C level was significantly decreased (9.24 +/- 1.96 to 8.11 +/- 1.39%, p < 0.001). Also, Kitt values were significantly increased (2.03 +/- 1.14 to 2.67 +/- 0.97%/min, p = 0.003), whereas HOMA-IR was significantly decreased (2.98 +/- 0.68 to 1.04 +/- 0.24, p < 0.05). When classifying insulin resistance by Kitt values, insulin resistant subjects' values were increased (< 2.5%/min; 1.51 +/- 0.53%/min to 2.63 +/- 0.88, p < 0.001), whereas the values decreased in insulin sensitive subjects (>or= 2.5%/min; 3.50 +/- 0.75%/min to 2.75 +/- 1.12%/min, p = 0.002). CONCLUSION The glucose lowering effects of TZDs by improving insulin resistance could be determined by using Kitt. However, Kitt may be a beneficial tool to determine TZDs' effects only when patients' Kitt values are less than 2.5%/min.