Vitamin B-6 Deficiency Induces Anxiety-Like Behavior in Sprague-Dawley Rats by Disrupting Gut Homeostasis.

Background: Vitamin B-6 (VB-6) is essential for numerous metabolic pathways, including neurotransmitter synthesis, and its deficiency has been linked to neurologic disorders. Emerging evidence suggests that B vitamin deficiencies can disturb the gut microbiome. Although the gut-brain axis is well recognized, the influence of VB-6 deficiency on behavior via gut-mediated mechanisms remains poorly understood.

Objectives: This study aimed to investigate the role of VB-6 in modulating the gut-brain axis and its impact on neurobehavioral outcomes.

Methods: Sixty-four Sprague-Dawley rats were fed an AIN-93G-based diet with either optimal [optimum vitamin B-6 (OB-6)] or deficient [deficient vitamin B-6 (DB-6)] amounts of VB-6 for 7 wk. Half of the rats received antibiotics in drinking water (ampicillin, 1 g/L; metronidazole, 1 g/L; and neomycin, 1 g/L) plus weekly gavage (vancomycin, 500 mg/L, and amphotericin B, 0.1 mg/mL). Plasma VB-6, neurotransmitters, short-chain fatty acids (SCFAs), behavioral assessments, gut microbiome composition, and gut histology were assessed. Data were analyzed using 2-way or 3-way analysis of variance with Fisher's least significant difference post hoc test (P ≤ 0.05).

Results: DB-6 rats showed ≤96% reduction in plasma VB-6 (P < 0.001), 22% decrease in brain γ-aminobutyric acid (P < 0.01), and 32% increase in glutamic acid (P < 0.01) compared with OB-6 animals. In the open-field maze, DB-6 animals reduced center-zone entries by 42% in males and 20% in females (P < 0.05), indicating anxiety-like behavior. Gut microbiota profiling revealed significant increases in Lachnospiraceae sp. (+385%), Mucispirillum schaedleri (+174%), and Harryflintia sp. (+848%) and decreases in Muribaculaceae sp. (-36%), Bacteroides vulgatus (-69%), and Bilophila sp. (-81%; P < 0.50). Cecal SCFA concentrations declined in DB-6 animals (P = 0.01), including propionate (-18%) in males and isobutyrate (-37%) and isovalerate (-63%) in females. Significant correlations (P < 0.05) were found between these taxa and neurochemicals and behavioral changes.

Conclusions: VB-6 deficiency alters gut microbiota composition, SCFA synthesis, and neurotransmitter balance, leading to anxiety-like behavior. These findings underscore the role of the gut microbiota in mediating VB-6-dependent gut-brain interactions.