No Long Term Benefit to Adjuvant Metformin in Type 1 Diabetes

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Adjuvant metformin produced a small but nonsignificant decrease in body mass index and insulin dose, but by year 10, no beneficial effects were evident.

Despite providing small short-term decreases in body mass index (BMI) and insulin dose, metformin as an adjunct to intensive insulin therapy failed to produce long-term benefits in patients with type 1 diabetes, concluded recent findings.

The 10-year retrospective study included 2 cohorts with type 1 diabetes: group 1 received adjuvant metformin for ≥6 months (n=186), and group 2 either refused metformin (n=25) or adhered to the therapy <6 months (n=37). The 2 cohorts had their BMIs, hemoglobin A1c (HbA1c) levels, and daily insulin doses registered on an annual basis.

As a reference for baseline comparison, researchers used a third cross-sectional group of 961 patients with type 1 diabetes who were not offered adjuvant metformin.

Baseline data indicated that BMI was significantly higher and insulin dose lower for patients in group 1; HbA1c levels did not significantly differ.

During the first years of metformin therapy, patients in group 1 experienced a small but nonsignificant decrease in BMI and insulin dose. However, by year 10, no effects were reported in BMI, insulin dose, or HbA1c levels.

According to researchers, study limitations included the heterogeneousness of groups 1 and 2 at start; the lack of registration during follow-up concerning concomitant medication use, intercurrent disease, sports activity, or dietician contact; and the absence of hard end point evaluation.

“We conclude that metformin is not associated with long-term beneficial effects on BMI, HbA1C, or daily insulin disease when added as adjunct therapy to intensive insulin therapy in patients [with type 1 diabetes],” the researchers wrote.

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Staels F, Moyson C, Mathieu C. Metformin as add-on to intensive insulin therapy in type 1 diabetes mellitus [published online March 20, 2017]. Diabetes Obes Metab. doi:10.1111/dom.12948