Benefits of metformin add-on insulin therapy (MAIT) for HbA1c and lipid profile in adolescents with type 1 diabetes mellitus: preliminary report from a double-blinded, placebo-controlled, randomized clinical trial

Objectives Metabolic control during puberty is impaired in Type 1 Diabetes Mellitus (T1DM) patients due to increased insulin resistance. Metformin is one of the oral medications typically used in type 2 diabetes mellitus to reduce insulin resistance. We aimed to examine the effect of metformin on glycemic indices and insulin daily dosage in adolescents with T1DM. Methods The present clinical trial was carried out on 50 adolescents aged 10-20 years with T1DM referred to the Endocrinology Clinic of Mofid Children's Hospital in Tehran for nine months. The patients were randomly divided into two groups. In the first group, metformin was added to insulin therapy, while the second group continued routine insulin therapy combined with placebo. Hemoglobin A1c (HbA1c), weight, BMI, insulin dosage, and blood pressure were measured at the beginning of the study and repeated every three months. Serum lipid profile, creatinine, blood urea nitrogen, and liver enzymes were also measured twice: At the beginning and end of the study (after nine months). Results The HbA1c level (p<0.001) and insulin dosage (p=0.04) were lower in the metformin group than in the placebo group after nine months. Daily insulin dosage variability was significantly lower in the metformin recipient group (p=0.041). Serum triglyceride, cholesterol, and creatinine were significantly lower in the metformin arm than in the placebo arm (p<0.05). However, metformin did not affect LDL, HDL, liver enzymes, and BUN. Conclusions Adjunctive metformin therapy reduces insulin dosage by inhibiting insulin resistance and weight gain. It helps decrease daily insulin dosage variability, which may prevent hypoglycemia. Also, metformin reduces creatinine, preventing renal failure in the long term.