Abstract

Background: Both first and second phase insulin secretion (FPIS, SPIS, respectively) are important underlying factors for glucose metabolism. However, their responses to the treatment of diabetes have not been studied. This randomized, prospective study evaluated the change of FPIS and SPIS in newly diagnosed type 2 diabetes (T2DM).

Methods: Twenty-seven drug naive T2DM patients were enrolled. They received both frequent sample intravenous glucose tolerance test (FSIGT) and a modified low-graded glucose infusion test (M-LDGGI) before and after a 24-week treatment randomly. The acute insulin response derived from FSIGT and the insulin-to-glucose slope during the M-LDGGI test were regarded as FPIS and SPIS, respectively. Subjects with the upper 50% SPIS were defined as responders and lower 50% were non-responders.

Results: Insulin secretion, predominantly SPIS, improved significantly after treatment while the insulin sensitivity remained unchanged. Compared to the non-responders, responders were younger (46.9 ± 6.7, 56±9.6 years, p=0.003), had lower body mass index (25.0±3.2, 25.7±3.8 kg/m2, p=0.012), higher fasting plasma glucose (181±68,123±44 mg/dl, p=0.044), higher glycated hemoglobin (11.1±2.3, 8.1±1.5 %, p=0.004), and lower SPIS (0.006 v.s 0.082, p=0.0019) in the baseline. In multivariate regression model, the changes of SPIS before and after treatment (d-SPIS) is negatively correlated to age, baseline SPIS and positively to serum triglyceride.

Conclusion: In drug naive type 2 diabetes, SPIS could be better improved in subjects with younger age, lower baseline SPIS and higher triglycerides.