The Cognitive benefits of nitrate in patients with alcohol use disorder: unraveling the oral microbiome ectopic colonization pathway.

Our prior research revealed that dietary nitrate (NO₃⁻) may mitigate alcohol-induced cognitive impairment through oral microbiota modulation and attenuation of inflammatory responses in mice. While alcohol use disorder (AUD) is known to associate with cognitive decline and gut dysbiosis, the therapeutic potential of nitrate supplementation in ameliorating these effects remains to be elucidated. In this randomized, double-blind, placebo-controlled pilot trial (NCT05963659), 70 AUD patients received either nitrate-rich beetroot juice or placebo for 14 days. Primary outcomes were spatial memory measured by Cambridge Neuropsychological Test Battery. Oral and gut microbiota were analyzed before and after intervention by 16S rRNA sequencing. To establish causality, germ-free (GF) mice were colonized with pre- and post-nitrate intervention saliva samples from AUD patients, followed by microbiota profiling across gastrointestinal regions. The mean difference in Delayed Matching to Sample (all delays) change between the nitrate consumption group and the placebo group after intervention was 9.784 (95%[CI], 1.85-17.72, P = 0.016), as analyzed using a generalized linear mixed model. Nitrate supplementation induced distinct shifts in oral microbiota, while gut microbiota exhibited less pronounced changes. GF mice receiving pre-intervention microbiota exhibited elevated Klebsiella abundance throughout the gut. Mechanistically, nitrate attenuated systemic inflammation, enhanced intestinal barrier integrity, and improved cognitive performance in mice. Dietary nitrate enhances cognitive function in AUD patients, partially mediated by ectopic colonization of oral microbiota. Our findings identify specific oral bacteria (e.g., Klebsiella) as key contributors to alcohol-induced cognitive impairment and suggest promising therapeutic potential for microbiota-targeted interventions in AUD.