Guidelines recommend off-label use of metformin in type 1 diabetes to reduce insulin dosages and improve glycaemic control. However, it is not known whether it has any cardiovascular benefits.
In an international study published in Lancet Diabetes Endocrinol
(online, 11 June 2017), researchers randomly assigned 428 patients with type 1 diabetes to either metformin (1,000mg) twice-daily or placebo and assessed common carotid artery intima-media thickness (cIMT) — a surrogate measurement for atherosclerosis — annually for three years.
They found no sustained improvement in glycaemic control, no reduction in insulin dosage or in the progression of mean cIMT in the metformin group compared with the placebo group. However, patients assigned to metformin saw significant reductions in body weight, low-density lipoprotein cholesterol, insulin dose and atherosclerosis progression.
The researchers conclude that the results do not support the use of metformin in type 1 diabetes to improve glycaemic control but suggest the treatment could still have a role in cardiovascular risk management.
 Petrie J, Chaturvedi N, Ford I et al. Cardiovascular and metabolic effects of metformin in patients with type 1 diabetes (REMOVAL): a double-blind, randomised, placebo-controlled trial. Lancet Diabetes Endocrinol 2017; doi: 10.1016/S2213-8587(17)30194-8