Effect of glycemic control on vitamin B 12 metabolism in diabetes mellitus

Abstract

To determine the effect of glycemic control on vitamin B 12 (B 12) metabolism in diabetes mellitus, we studied B 12 metabolism in 19 diabetic patients with poor glycemic control and 15 normal individuals. The diabetic patients had significantly higher total B 12 binding capacity (3303 ± 963 pg/ml), higher serum B 12 levels (1173 ± 503 pg/ml) and unsaturated B 12 binding capacity (2131 ± 902 pg/ml) when compared with the normal controls, but there was no difference in R-binder levels and the B 12 binding ratio between the two groups. During a 2-week admission to establish glycemic control, the fructosamine levels in the diabetic patients decreased from 556 to 428 μmol/l and the total B 12 binding capacity as well as unsaturated B 12 binding capacity were significantly improved to the normal range ( P < 0.01), but serum B 12 levels, R-binder levels and the B 12 binding ratio were not changed. There was a significant association between serum fructosamine levels and the total B 12 binding capacity in poorly controlled diabetic patients and the decrease of fructosamine was correlated significantly with the change of total B 12 binding capacity and serum B 12 levels in diabetic patients. These results indicate the effects of glycemic control on B 12 metabolism in diabetes mellitus.