Exercise, APOE Genotype, and Testosterone Modulate Gut Microbiome-Cognition Associations in Prostate Cancer Survivors

Background: Men treated with androgen deprivation therapy (ADT) for prostate cancer are at risk for cognitive decline. Patient genetics and endocrine state may shape gut microbiome features that relate to cognition. Methods: We studied a subsample of 79 prostate cancer survivors with prior ADT exposure previously enrolled in a randomized controlled exercise trial comparing three training modalities (strength training, Tai Chi training, or stretching control) who completed an additional food-frequency questionnaire and remote Montreal Cognitive Assessment (MoCA) and provided saliva and stool for APOE genotyping, salivary testosterone, and 16S rRNA sequencing. We used beta regression for MoCA (scaled 0-1), linear models for testosterone, alpha diversity regressions, PERMANOVA for beta diversity, and DESeq2 for genus-level differential abundance, with false-discovery correction. Results: Compared to post-stretching control, post-strength training testing was associated with higher MoCA scores whereas post-Tai Chi testing was not. APOE ε4 carriers exhibited a greater testosterone increase with strength training than non-carriers. Testosterone, and its interactions with exercise modality and APOE ε2 status, was related to presence/absence-based community structure; APOE ε4 interacted with exercise intervention to influence alpha diversity. At the genus level, exercise was linked to lower levels of Bacteroidota taxa (including Muribaculaceae) and higher levels of Enterobacteriaceae; APOE ε4 status was linked to higher Megamonas and lower Rikenellaceae RC9 levels; and higher salivary testosterone levels were linked to higher Prevotellaceae taxa and Succinivibrio levels. Higher MoCA scores were associated with lower abundances of several Firmicutes genera. Conclusions: Endocrine state and APOE genotype may condition the gut microbiome's response to exercise intervention in ADT-treated prostate cancer survivors, with downstream associations with cognition. These findings could inform precision survivorship strategies pairing strength training with genotype- and hormone-informed microbiome monitoring to optimize cognitive performance.