Metformin is the first-line drug for type 2 diabetes (T2D) while acarbose is suggested as a viable alternative in Chinese patients with newly diagnosed T2D. However, few biomarkers have been established to guide the choice between these two agents. Mitochondrial DNA (mtDNA) copy number (mtDNA-CN) is a biomarker of mitochondrial function, which is associated with various metabolic outcomes. Using data from the trial of Metformin and Acarbose in Chinese as the Initial Hypoglycaemic Treatment (MARCH) (metformin n = 214; acarbose n = 198), we examined whether mtDNA-CN was associated with response to the drugs in terms of glycemic response and β-cell function protection response. The glycemic response is defined as the maximum glucose reduction of glycated hemoglobin A1c , fasting plasma glucose, or postprandial blood glucose during 48 weeks. β-cell function protection response is defined as the maximum increment of insulinogenic index (IGI) or disposition index (DI). For all three glycemic responses, mtDNA-CN was not significantly associated with either metformin or acarbose. Importantly, for β-cell function protection response, we found the increased mtDNA-CN was significantly associated with more IGI increment (beta: 0.84; 95% confidence interval (CI), 0.02 to 1.66) in the metformin group, but less IGI increment (beta: -1.38; 95% CI, -2.52 to -0.23) in the acarbose group. A significant interaction (P = 0.008) between mtDNA-CN and the treatment group was observed. Consistent results were also obtained when DI increment was used as a measure of β-cell function response. This study demonstrated the potential application of mtDNA-CN in guiding the treatment choice between metformin and acarbose based on β-cell protection.
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