Metformin added to intensive insulin therapy improves metabolic control in patients with type 1 diabetes and excess body fat.

INTRODUCTION Bad nutritional habits and administration of insulin in supraphysiological doses lead to the development of insulin resistance and poor metabolic control in patients with type 1 diabetes. Accumulation of visceral fat is the main cause of the decrease in insulin sensitivity. OBJECTIVES We aimed to evaluate changes in anthropometric parameters, indirect measures of insulin resistance, and safety of treatment with metformin added to intensive insulin therapy in patients with type 1 diabetes and excess body fat. PATIENTS AND METHODS We analyzed 114 patients (60 women and 54 men; median age, 31 years [range, 18-60 years]), with a median diabetes duration of 14 years (range, 10-20 years). Metformin was administered for at least 6 months in 74 patients, while 40 patients did not receive metformin. The study group was randomized in a 2:1 ratio. Total body fat assessment and laboratory tests were performed before the study and at 6-month follow-up. RESULTS At 6 months, in the metformin group, compared with the non-metformin group, an improvement was noted for adiposity parameters (reduction in body mass index, -0.4 kg/m2 vs 0.6 kg/m2, P = 0.006; waist circumference, -5 cm vs 3.5 cm, P = 0.02; and total body fat, -1.7 kg vs 1.4 kg; P <0.001; glycated hemoglobin A1c: -0.6% vs 0.2%, P <0.001), as well as for lipid parameters and blood pressure. An increase in the estimated glomerular filtration rate was greater in the metformin compared with the non-metformin group: 0.9 mg/kg/min vs -0.2 mg/kg/min, P <0.001). CONCLUSIONS In patients with type 1 diabetes and excess body fat, treated with intensive functional insulin therapy, the addition of metformin improves metabolic control of diabetes at 6 months. Metformin added to insulin therapy in patients with type 1 diabetes and excess body fat appears to be safe.