The addition of metformin in type 1 diabetes improves insulin sensitivity, diabetic control, body composition and patient well-being

Aim: As many overweight people with T1DM are insulin resistant, adjuvant therapy with insulin sensitising agents, such as metformin, may be beneficial. This study evaluated the effect of adjuvant metformin in T1DM on insulin sensitivity, diabetic control, body composition, quality of life (QOL) and treatment satisfaction. Materials and Methods: A 3-month prospective open-labelled pilot study of 16 patients aged 18-40 with T1DM and body mass index (BMI) > 25 kg/m(2) was performed. The patients received 500-850 mg metformin twice daily. Insulin sensitivity, assessed by a frequently sampled intravenous glucose tolerance test [n=5], body composition, HbA(1c) and quality of life (QOL) were measured before and after treatment. A retrospective review of 30 patients with T1DM treated with metformin for at least 4 months was also performed. BMI, HbA(1c) and insulin requirements during metformin treatment was compared to pre-metformin data, and to patients treated with insulin only. Results: In the pilot study, insulin sensitivity increased significantly from 0.86 +/- 0.33 x 10(-4)/min/(mu U/ml) to 1.17 +/- 0.48 x 10(-4)/min/(mu U/ml) after 3 months adjuvant therapy (p = 0.043). This was associated with a decreased insulin requirement and mean daily blood glucose. There were no significant changes in HbA(1c) or body composition. QOL significantly improved (p < 0.002). The retrospective review revealed an initial reduction in HbA(1c) (0.8 +/- 1.4%, p = 0.001). This effect diminished with prolonged treatment. BMI decreased in patients remaining on metformin for a 2-year period (0.5 +/- 0.5kg/m(2), p = 0.042). Conclusion: Adjuvant metformin can improve QOL, insulin sensitivity and glycaemic control in overweight adults with T1DM.