Effects of metformin or rosiglitazone on serum concentrations of homocysteine, folate, and vitamin B12 in patients with type 2 diabetes mellitus

Objectives: Metformin is widely used in patients with type 2 diabetes but may decrease vitamin 1312 levels and increase levels of homocysteine (Hey), a cardiovascular risk factor. Rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist, may reduce markers of inflammation. We investigated whether 6 weeks' treatment with metformin or rosiglitazone affects serum concentrations of Hey, folate, or vitamin B-12 in subjects with newly diagnosed type 2 diabetes compared with controls. Methods: We examined 165 patients with type 2 diabetes. Fasting blood samples, a physical examination, and a complete medical history were performed at the beginning and at the end of the treatment. All blood samples were obtained after a 12-h fast. Results: After treatment, metformin use was associated with an increase in levels of Hey by 2.36 mu mol/l and decreases in folate and vitamin B-12 concentrations by -1.04 ng/ml and -20.17 pg/ml. During rosiglitazone treatment, Hey levels decreased by -0.92 mu mol/l; folate and vitamin B-12 levels remained unchanged. Metformin and rosiglitazone significantly decreased levels of triglyceride (TG), low-density lipoprotein (LDL), total cholesterol (total-C), HbAlc, insulin, and homeostasis model assessment (HOMA). Metformin also significantly decreased body weight. In controls, there was no change in Hey, folic acid, vitamin B-12, TG, LDL, total-C, HbAlc, insulin, or HOMA levels. Homocysteine change did not correlate with insulin, folate, or vitamin B-12 changes in the metforinin and rosiglitazone groups. Conclusions: In patients with type 2 diabetes, metformin reduces levels of folate and vitamin B-12 and increases Hey Conversely, rosiglitazone decreases Hey levels in this time period. The clinical significance of these findings remains to be investigated. (c) 2007 Elsevier Inc. All rights reserved.