Bacteroides ovatus accelerates metformin-induced vitamin B12 deficiency in type 2 diabetes patients by accumulating cobalamin

Abstract

Vitamin B12 (VB12) deficiency, which may lead to hematologic and neurologic symptoms, has been associated with metformin use, but the underlying mechanism is unclear. Here we report the B. ovatus as an effective VB12 catcher which was enriched in the type 2 diabetes patients suffered from VB12 deficiency after 3 to 6 months of metformin treatment. Colonization of B. ovatus increased the plasma levels of methylmalonic acid and homocysteine in high-fat diet (HFD)-fed mice treated with metformin, and compromised the efficacy of metformin against the HFD-induced metabolic disorders. Mechanistically, metformin increased the intracellular accumulation of VB12 in B. ovatus via btuB upregulation and promoted ATP production for energy-dependent translocation of VB12 transporters at the inner membrane, leading to an enhanced colonization of B. ovatus to compete for VB12 with hosts and subsequently an aggravated VB12 deficiency in the host. Our findings illustrate a previously unappreciated mechanism of metformin leads to host VB12 deficiency by acting directly on gut bacteria to increase their VB12 uptake and consumption, and suggest that inter-host-microbe competition for nutrients may broadly impact human health and drug safety.

Human gut microbes express functionally distinct endoglycosidases to metabolize the same N-glycan substrate

“…7 ), an apparent conserved phenomenon widespread amongst bacterial species that prominently colonize the human gut (Supplementary Fig. 17 ), some of which are currently being used as probiotics or postbiotics (e.g., B. xylanisolvens 75 , 76 and B. ovatus 77 – 79 ). Moreover, it was recently proposed that carbohydrate metabolism by Bacteroidales (mainly A. indistinctus , A.finegoldii and B. thetaiotamicron ) has a potential therapeutic role in ameliorating diet-induced obesity and insulin resistance 74 .…”

4-Ethylphenol—fluxes, metabolism and excretion of a gut microbiome derived neuromodulator implicated in autism

“…This is important as B12 administration improves metabolic abnormalities in autistic individuals along with clinical symptoms ( Rossignol and Frye, 2021 ). B. ovatus sequesters B12 from the host via btuB upregulation and ATP production promoting energy-dependant translocation of vitamin B12 transporters at the inner membrane, enhancing B. ovatus colonisation in the gut ( Chen et al, 2023 ). Increased B. ovatus may impact autistic individuals through aiding production of neurotoxins and reducing beneficial metabolites (e.g., B12).…”