Author(s)

Satoru Sumitani, Shinya Morita, Reiko Deguchi, Koichi Hirai, Kosuke Mukai, Yoshihiko Utsu, Shunji Miki, Bunzo Sato, Hideji Nakamura, Soji Kasayama

Center for Preventive Medicine, Nissay Hospital, Osaka, Japan.
Department of Medicine, Nissay Hospital, Osaka, Japan.

β-cell dysfunction and decreased insulin sensitivity are believed to be two chief mechanisms that participate in deterioration of glycemic control in Type 2 diabetes. Meformin is widely accepted as the first-line oral agent in the treatment of Type 2 diabetes. However, the relative contributions of improved β-cell function and increased insulin sensitivity to reduction in hemoglobin A1c (HbA1c) are unclear in newly diagnosed Type 2 diabetic patients treated with metformin. We investigated β-cell function and insulin sensitivity in relation to reduction in HbA1c in 20 newly diagnosed Type 2 diabetic patients (17 men and 3 women, mean age 49.1 ± 10.1 years, mean body mass index 26.4 ± 5.2 kg/m²) treated with metformin for 16 weeks. We used homeostasis model assessment (HOMA) 2%B and HOMA2%S as estimates of β-cell function and insulin sensitivity, respectively. Median HOMA2%B and HOMA2%S significantly increased from 38.8 to 68.8 (p < 0.001) and from 50.2 to 67.1 (p = 0.004), respectively. In univariate regression analysis, reduction in HbA1c was highly correlated with change in HOMA2%B (r = -0.866, p < 0.001), but not with that in HOMA2%S (r = -0.264, p = 0.260). Furthermore, multivariate regression analysis with reduction in HbA1c as a dependent variable showed that increase in HOMA2%B but not that in HOMA2%S was a significant dependent variable (β = -0.847, p < 0.001). In conclusion, our findings demonstrate that improved β-cell function rather than increased insulin sensitivity is associated with reduction in HbA1c. These results suggest that metformin reduces HbA1c chiefly through improved β-cell function rather than increased insulin sensitivity in patients with newly diagnosed Type 2 diabetes.

Metformin; Type 2 Diabetes; β-Cell Function; Insulin Sensitivity

Sumitani, S. , Morita, S. , Deguchi, R. , Hirai, K. , Mukai, K. , Utsu, Y. , Miki, S. , Sato, B. , Nakamura, H. and Kasayama, S. (2014) Improved β-cell function rather than increased insulin sensitivity is associated with reduction in hemoglobin A1c in newly diagnosed Type 2 diabetic patients treated with metformin. Journal of Diabetes Mellitus, 4, 44-49. doi: 10.4236/jdm.2014.41008.