Etiology-associated differences in the gut microbiome and metabolome in hepatocellular carcinoma: an exploratory study of alcohol-related and HBV-related cases.

Hepatocellular carcinoma (HCC) arises in heterogeneous etiological contexts, but direct cross-omics comparisons between HCC subgroups defined by different etiologies remain limited. In this exploratory study, we combined fecal 16S rRNA gene sequencing and untargeted serum metabolomics with exploratory cross-omics analyses to compare gut microbial composition, serum metabolic profiles, and microbiome-metabolite association patterns between hepatitis B virus-related HCC (HBV-HCC) and alcohol-related HCC (ALD-HCC). Forty patients who underwent primary tumor resection were included, comprising 26 with HBV-HCC and 14 with ALD-HCC. Alpha diversity indices did not differ significantly between groups, whereas within-group Bray-Curtis dissimilarity was greater in ALD-HCC and genus-level beta-diversity ordination showed only modest separation between the two groups. LEfSe-based screening suggested the enrichment of candidate taxa, including Faecalibacterium, Roseburia, Lachnospira, Turicibacter, and Butyribacter in HBV-HCC, whereas Allisonella and Coprobacillus were enriched in ALD-HCC. Untargeted metabolomics showed group separation in supervised models and identified exploratory candidate metabolic features mainly involving glycerophospholipid metabolism, primary bile acid biosynthesis, aminoacyl-tRNA biosynthesis, and central carbon metabolism in cancer; however, these metabolite-level findings did not remain significant after multiple-testing correction. Procrustes and O2PLS analyses indicated limited global concordance between the microbiome and metabolome, although exploratory associations were observed between several phosphatidylcholine-related features and microbial taxa. Overall, HBV-HCC and ALD-HCC may be associated with different gut microbial and serum metabolic patterns, and these findings should be considered exploratory and hypothesis-generating.