Modeling microbiota-mediated risk for alcohol use disorder: a preclinical study of fecal transplantation from ethanol-exposed mice

<i>Background:</i> Alcohol use during adolescence and early adulthood promotes the development of alcohol use disorder (AUD). Emerging evidence suggests that ethanol-induced gut microbiota alterations may contribute to AUD vulnerability; however, it remains unclear whether microbiota imbalances are a causal risk factor or a consequence of alcohol exposure.<i>Objectives:</i> This preclinical study assessed if fecal microbiota transplantation (FMT) from donors exposed to ethanol during adolescence/early adulthood would alter ethanol drinking and other behaviors, in unrelated naïve mice.<i>Methods:</i> Forty-two (31 males and 11 females) C57BL/6J mice were exposed to a repeated 2-days-on, 2-days-off ethanol access protocol from postnatal day 43 to 80. Fecal microbiota from ethanol-exposed (or control) donors was transplanted into antibiotic-pretreated naïve male (<i>n</i> = 26) and female (<i>n</i> = 16) recipients. These were assessed for ethanol intake, including compulsive-like drinking (i.e. after quinine adulteration). Anxiety and repetitive behavior were measured in the light-dark box, elevated plus maze and marble-burying tests.<i>Results:</i> Female, but not male, recipients of FMT from ethanol-exposed donors showed significantly increased ethanol consumption (n²<i>p</i> = .32) and preference (n²<i>p</i> = .36) compared to controls (<i>p</i> < .05). This included sustained intake despite quinine adulteration (<i>p</i> < .05), suggestive of compulsive-like drinking. Ethanol-exposed male mice showed a significant increase in marble-burying (<i>p</i> < .05), consistent with compulsive-like tendencies. Additionally, both male (n²<i>p</i> = .30) and female (n²<i>p</i> = .28) donor mice exhibited behavioral disinhibition (<i>p</i> < .05).<i>Conclusions:</i> These findings provide preclinical evidence that microbiota alterations after ethanol exposure at late adolescence can transmit vulnerability to alcohol intake, with sex-specific effects. The results highlight the potential of microbiota-targeted interventions in prevention and treatment strategies for AUD.