Dietary Vitamin B6 Deficiency and Gut Microbiota Depletion Can Lead to Anxiety-Like Behavior in Rats

Objectives: Vitamin B6 is an essential micronutrient for myriad metabolic pathways, including neurotransmitter biosynthesis. The gut microbiota can regulate gut-derived neuroactive compound levels. However, the impact of B6 deficiency on the gut-mediated regulation of neurotransmitters and host behavior through the gut-brain axis is unknown. We aim to assess whether dietary B6 deficiency-induced gut microbiome alteration can modulate host behavior by controlling gut-derived neurotransmitters and neuroactive metabolite synthesis. Methods: Sixty-four Sprague-Dawley rats were fed either an AIN93G-based control (B6 7 mg/kg diet) or a vitamin B6 deficient (B6 0.07 mg/kg diet) diet for 6 weeks. In each diet group, half of the animals received an antibiotic cocktail through drinking water and weekly gavage, while the others received normal water. During the 6th week, the behavior of the rats was assessed. The cecal microbiome was profiled using 16s rRNA full-length amplicon sequencing (PacBio-Sequel2). The sequence data were analyzed using QIIME2 to visualize the relative taxonomic abundance. Histomorphology assessments were performed in the jejunum and colon. Data were analyzed using 2-way ANOVA. Results: Antibiotic treatment increased the relative abundance of Proteobacteria and decreased the Firmicutes and Bacteroidota, while B6 deficiency increased Deferribacterota, Actinobacteriota and decreased Desulfobacterota. Both villous height (p=0.002) and crypt depth (p=0.001) were lowered in the jejunum with microbiota-depleted (MD) B6 deficiency. The open field maze showed a lower distance traveled (p< 0.0001) and rearing time (p=0.0351) in MD-B6-deficient rats compared to the other groups. In the elevated plus maze, MD-B6 deficient female rats showed significantly lower head dips (p=0.028) than others. Also, B6-deficient male rats showed significantly higher entries to the closed arm (p=0.017). The sucrose preference test showed the lowest preference over 24 hours (p=0.0183) in MD female rats. Conclusions: The microbiota-depleted, B6-deficient conditions affect intestinal morphology and bacterial diversity, while also inducing anxiety-like behavior in rats. Our study suggests that dietary B6 deficiency regulates host behavior through the microbiota-gut-brain axis. Funding Sources: Natural Sciences and Engineering Research Council of Canada.