Metformin improves glycemic variability in adults with type 1 diabetes mellitus: an open-label randomized control trial

INTRODUCTION: Metformin has been demonstrated to enhance cardioprotective benefits in type 1 diabetes (T1DM). Although glycemic variability (GV) is associated with increased risk of CVD in diabetes, there is a scarcity of research evaluating the effect of metformin on GV in T1DM. OBJECTIVES: In the present study, the effects of adjuvant metformin therapy on GV and metabolic control in T1DM were explored. PATIENTS AND METHODS: A total of 65 adults with T1DM were enrolled and subjected to physical examination, fasting laboratory tests, and continuous glucose monitoring, and subsequently randomized 1:1 to 3 months of 1000–2000 mg metformin daily add-on insulin (MET group, n = 34) or insulin (non-MET group, n = 31). After, baseline measurements were repeated. RESULTS: The mean amplitude of glycemic excursions was substantially reduced in MET group, compared with non-MET group (–1.58 (–3.35, 0.31) mmol/L vs 1.36 (–1.12, 2.24) mmol/L, P = 0.004). In parallel, the largest amplitude of glycemic excursions (–2.83 (–5.47, –0.06) mmol/L vs 0.45 (–1.29, 4.48) mmol/L, P = 0.004), the s.d. of blood glucose (–0.85 (–1.51, 0.01) mmol/L vs –0.14 (–0.68, 1.21) mmol/L, P = 0.015), and the coefficient of variation (–6.66 (–15.00, 1.50)% vs –1.60 (–6.28, 11.71)%, P = 0.012) all demonstrated improvement in the MET group, compared with the non-MET group. Significant reduction in insulin dose, BMI, and body weight was observed in patients in MET, not those in non-MET group. CONCLUSION: Additional metformin therapy improved GV in adults with T1DM, as well as improving body composition and reducing insulin requirement. Hence, metformin as an adjunctive therapy has potential prospects in reducing the CVD risk in patients with T1DM in the long term.