Некоторый апдейт по теме: похоже, что метформин просто снижает концентрацию кобаламина в крови, усиливая его депонирование в клетках, а не вызывает дефицит В12 в организме, подробнее:
Metformin (Glucophage) is regarded a first-line drug in the treatment of type 2 diabetes mellitus. However, it has been shown that treatment with metformin is associated with a decrease in serum vitamin B12 concentrations, which worsens with increasing dose and length of treatment (Ting et al., 2006; de Jager et al., 2010; Liu et al., 2014). The association has been suggested to be due to interference with the calcium dependent intestinal uptake of the vitamin B12-intrinsic factor complex (Bauman et al., 2000). However, although serum B12 is reduced, metformin treatment has been associated with reduction in plasma MMA and indications of improved intracellular B12 status in diabetics (Obeid et al., 2013). Hence, a vitamin B12 resistance phenomenon was suggested in diabetics, and metformin treatment seemed to improve the intracellular vitamin B12 metabolism, contrary to previous beliefs. Two studies found that patients treated with metformin had reduced levels of both serum vitamin B12 and haptocorrin, but treatment was without effect on the levels of holo-TC, the bioactive form of vitamin B12 that is distributed systemically to all cells in the body (Leung et al., 2010; Greibe et al., 2013c). Another study showed that treatment of rats with metformin increased hepatic accumulation of vitamin B12 (Greibe et al., 2013b). This suggests that metformin may alter the homeostasis and tissue distribution of vitamin B12, the consequences of which remain to be investigated. Because not all cases of low serum vitamin B12 imply deficiency, and normal and high serum levels of vitamin B12 are likewise observed in patients with severe functional vitamin B12 deficiency, concern has been raised regarding the interpretation of the effects of metformin on vitamin B12 status (Obeid, 2014). In terms of prevention, diabetics receiving metformin should be regarded at increased risk, and routine screening and supplementation if necessary, should be recommended (Valdes-Ramos et al., 2015).
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Front Mol Biosci. 2016 Jun 27;3:27.
Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency.
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