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 (≥ 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.