Beta-cell function in type 2 diabetic patients who failed to maintain good glycemic status with a combination of maximum dosages of metformin and sulfonylurea.

The aim of this study was to investigate beta-cell function and examine whether sulfonylureas (SUs) are still useful in patients with type 2 diabetes (T2DM) who failed to maintain optimal glycemic control with a combination of maximum dosages of metformin and SU. T2DM who had Hb >8% during treatment with a combination of maximum dosages of metformin and SU were studied. After enrollment, the patients were assigned to continue maximum dosages of SU and metformin for 2 weeks and then underwent the first oral glucose tolerance test (OGTT), the Max-SU OGTT. After the Max-SU OGTT, SUs were discontinued for 4 weeks and the second OGTT, the Discont-SU OGTT, was performed. After the Discont-SU OGTT, the same SU was restarted at 25% of the maximum dosage (25%Max-SU). After taking 25%Max-SU for 4 weeks, the third OGTT, the 25%Max-SU OGTT, was performed. Metformin at the same dosage was continued throughout the study. Normal OGTT (NGT) subjects, matched for age and body mass index (BMI), were also studied. There were 25 T2DM and 28 NGT subjects. There was no difference in age and BMI between the two groups. The beta-cell function during Max-SU was 0.1, which was higher than 0.06 during Discont-SU (<0.001) and also higher than 0.09 during 25%Max-SU (=0.269). The beta-cell function during 25%Max-SU was higher than during Discont-SU (<0.001). The beta-cell function of the NGT group was 0.34 and higher than during Max-SU (<0.001). Fasting capillary blood glucose (FCBG) levels during Discont-SU (14.2±3.7 mmol/L) were higher than during 25%Max-SU (12.3±3.4 mmol/L) and during Max-SU (10.3±2.4 mmol/L) (<0.05). In addition, the FCBG during Discont-SU was higher than that during 25%Max-SU (<0.05). In T2DM patients who failed to achieve glycemic control with a combination of maximum dosages of metformin and SU, the beta-cell function declined compared to NGT subjects. However, the beta-cells were still responsive to SUs, which play a significant role in glycemic control.