Gut Microbiota Composition in Maintenance Hemodialysis Patients: Associations with Sex, Age, and Body Composition

Background/Objectives: Patients receiving maintenance hemodialysis (HD) commonly exhibit malnutrition, chronic low-grade inflammation, and metabolic disturbances. Gut dysbiosis may contribute to these abnormalities through the gut-kidney axis. This study aimed to characterize gut microbiota composition in HD patients and examine its associations with demographic, clinical, and body composition parameters. Methods: This cross-sectional study included 96 patients with end-stage kidney disease on maintenance HD. Clinical, laboratory, inflammatory, nutritional, and bioimpedance-derived body composition data were collected, including Malnutrition-Inflammation Score (MIS). Stool samples were analyzed for gut microbiota composition. Associations with host-related variables were assessed using alpha- and beta-diversity analyses, subgroup comparisons, and Mantel testing. Results: Gut microbiota showed marked inter-individual heterogeneity at the genus level, with dominant taxa including Blautia, Faecalibacterium, Streptococcus, Gemmiger, Ruminococcus, Escherichia-Shigella, and Enterococcus. Chao1 richness was higher in men than in women. Shannon entropy and Chao1 richness were positively associated with age and visceral adipose tissue (VAT), while Faith’s phylogenetic diversity increased with age. In contrast, the Gini index was negatively associated with age and VAT, indicating a more even microbial structure in older individuals and those with higher visceral adiposity. Beta-diversity differed between men and women and across categories within the female subgroup. Mantel testing showed a modest but significant correlation between microbiota and metadata distances. Conclusions: Gut microbiota in maintenance HD patients is highly heterogeneous and associated mainly with sex, age, visceral adiposity, and overall host phenotype. These findings suggest that microbiota variation in HD reflects multidimensional host-related factors rather than a single clinical feature.