Gender-specific gut microbiota alterations in adolescent C57BL/6 mice following prenatal alcohol exposure.

Fetal Alcohol Spectrum Disorder (FASD), caused by prenatal alcohol exposure (PAE), produces lasting physical, cognitive, and behavioral impairments. The present study examined effects of early PAE on the gut microbiome (GM) in adolescent mice to identify targets for early intervention. Female C57Bl/6 dams received 10 % ethanol during the first 10 days of gestation while controls received water. Fecal and blood samples from adolescent offspring were profiled by 16S rRNA sequencing and gas chromatography-mass spectrometry to characterize microbial composition and short-chain fatty acids (SCFAs). PAE reduced microbial alpha diversity and produced distinct beta diversity patterns versus controls. Metabolomic profiling revealed increased fecal acetate and reduced anti-inflammatory SCFAs in PAE mice, though circulating SCFA levels remained unchanged. Sex-stratified analyses showed that these alterations were driven predominantly by males, who exhibited greater microbial and metabolic disruptions, enrichment of pro-inflammatory genera (Parasutterella, Parabacteroides, Clostridioides), and elevated serum medium-chain fatty acids. Cluster analysis of PAE males identified a dysbiotic subgroup with severe alpha diversity loss, increased pro-inflammatory taxa, diminished beneficial SCFAs, and enrichment of catabolic and fatty acid biosynthesis pathways. Together, the results reveal sex- and individual-specific susceptibility to PAE-induced GM dysbiosis and justify further mechanistic studies to develop sex-tailored microbiota-targeted strategies for FASD.