Use of Metformin in Type 1’s

Metformin reduces insulin-dose requirement in Type 1 diabetes. As adding metformin to insulin therapy has been advocated in Type 1 diabetes, researchers at the Universities of Dundee and Aberdeen, U.K., conducted a systematic review of published clinical trials and clinical trial databases to assess the effects on HbA_1c, weight, insulin-dose requirement and adverse effects….

Researchers constructed evidence tables and fitted a fixed-effects model (inverse variance method) in order to assess heterogeneity between studies and give a crude measure of each overall treatment effect.  

The results showed that of 197 studies identified, nine involved randomization with informed consent of patients with Type 1 diabetes to metformin (vs placebo or comparator) in either a parallel or crossover design for at least 1 week. Marked heterogeneity in study design, drug dose, age of participants and length of follow-up was noted. Metformin was associated with reductions in: (1) insulin-dose requirement (5.7–10.1 U/day in six of seven studies); (2) HbA_1c (0.6–0.9% in four of seven studies); (3) weight (1.7–6.0 kg in three of six studies); and (4) total cholesterol (0.3–0.41 mmol/l in three of seven studies). 

Metformin was well tolerated, albeit with a trend towards increased hypoglycemia. Formal estimates of combined effects from the five trials which reported appropriate data indicated a significant reduction in insulin dose (6.6 U/day) but no significant reduction in HbA_1c (absolute reduction 0.11%). No reported trials included cardiovascular outcomes. 

From the results it was concluded that Metformin reduces insulin-dose requirement in Type 1 diabetes but it is unclear whether this is sustained beyond 1 year and whether there are benefits for cardiovascular and other key clinical outcomes.