Metagenomic and metabolomic profiling in primary aldosteronism with coexisting obstructive sleep apnea.

Background: Primary aldosteronism (PA) frequently coexists with obstructive sleep apnea (OSA), and this comorbidity is associated with increased cardiometabolic risk. Although both PA and OSA have been individually linked to gut microbiome alterations, it remains unclear which layer of gut microbiome-associated variation best reflects clinical heterogeneity in PA with coexisting OSA. Methods: In this prospective observational study, we performed shotgun metagenomic sequencing and untargeted fecal metabolomic profiling in 29 adults with clinically confirmed PA, who were stratified according to OSA severity (G1-G4) based on overnight polysomnography. Microbial gene richness, taxonomic composition, functional potential based on KEGG annotation, and antibiotic resistance gene profiles were analyzed using standardized bioinformatic workflows. Metabolomic variation was assessed using multivariate analysis, pathway enrichment, and additional exploratory analyses incorporating apnea-hypopnea index (AHI) as a continuous variable. Multiple-testing correction was applied to metabolite-level comparisons. Results: Global gut microbial gene richness, alpha diversity, beta diversity, and broad functional profiles did not show strong group-level separation across OSA severity strata. Additional analyses using AHI as a continuous variable similarly showed no significant association between AHI and overall gene richness or alpha diversity indices. Nevertheless, selective genera showed exploratory associations with AHI, suggesting that localized taxonomic signals may occur despite relative stability of global community structure. Antibiotic resistance gene profiles showed marked inter-individual variability without clear group-level separation, although ARO richness showed an exploratory inverse association with AHI. In contrast, fecal metabolomic profiling revealed nominal phenotype-associated differences, including trehalose-related metabolites and FAHFA species that showed inverse exploratory associations with AHI. However, no individual metabolite remained significant after global Benjamini-Hochberg false discovery rate correction. Conclusions: In PA with coexisting OSA, gut microbiome-associated heterogeneity appears to be more readily reflected by selected taxonomic and metabolic signals than by global microbial diversity or broad functional potential. However, given the small sample size, limited control of clinical and lifestyle confounders, and lack of metabolite-level significance after global FDR correction, these findings should be interpreted as exploratory and hypothesis-generating. Larger controlled cohorts incorporating PA subtype, medication exposure, dietary assessment, and longitudinal validation are needed.