Miglitol, an α-glucosidase inhibitor, prevents the metformin-induced fall in serum folate and vitamin B12 in subjects with type 2 diabetes

Since folate and vitamin B12 absorption may be increased by colonic bacterial activity, their status may be improved by miglitol, an α-glucosidase inhibitor of potential use in the treatment of diabetes. To test this, subjects with type 2 diabetes were treated for 9 months in a double-blind, randomized controlled fashion with either placebo (n=45), miglitol (n=45), metformin (n=62), or a combination of miglitol and metformin (n=47). Glycated hemoglobin (HbA1c), serum and red cell folate and serum vitamin B12 were measured and 3-day dietary records obtained before and after therapy. Compared to placebo, all 3 active treatments significantly reduced HbA1c, metformin to a greater extent than miglitol and the combination to a greater extent than metformin. Dietary folate intake did not change on any treatment. Serum folate and vitamin B12, respectively, did not change on placebo, but fell by 14% and 15% on metformin and rose by 12% and 23% on miglitol. The changes in folate and vitamin B12 concentrations on metformin were significantly different from those on miglitol. On combination therapy, both folate and vitamin B12 tended to rise, but the difference from metformin was only significant for folate. These data support the hypothesis that increased carbohydrate delivery to the colon increases intestinal biosynthesis of folate. The combination of miglitol with metformin may prevent the metformin-induced fall in serum folate and vitamin B12.