Oral vitamin B12 supplement is delivered to the distal gut, altering the corrinoid profile and selectively depleting Bacteroides in C57BL/6 mice

ABSTRACTVitamin B12 is a critical nutrient for humans as well as microbes. Due to saturable uptake, high dose oral B12 supplements are largely unabsorbed and reach the distal gut where they are available to interact with the microbiota. The aim of this study was to determine if oral B12 supplementation in mice alters 1) the concentration of B12 and related corrinoids in the distal gut, 2) the fecal microbiome, 3) short chain fatty acids (SCFA), and 4) susceptibility to experimental colitis. C57BL/6 mice (up to 24 animals/group) were supplemented with oral 3.94 µg/ml cyanocobalamin (B12), a dose selected to approximate a single 5 mg supplement for a human. Active vitamin B12 (cobalamin), and four B12-analogues ([ADE]CN-Cba, [2Me-ADE]CN-Cba, [2MeS-ADE]CN-Cba, CN-Cbi) were analyzed in cecal and fecal contents using liquid chromatography/mass spectrometry (LC/MS), in parallel with evaluation of fecal microbiota, cecal SCFA, and susceptibility to dextran sodium sulfate (DSS) colitis. At baseline, active B12 wa...