Abstract
Gastric cancer (GC) and Parkinson’s disease (PD) are age-associated diseases that have been linked to gut microbiome dysbiosis. Despite the significance of the gut microbiome in the onset of these two diseases, no study to date has compared them with each other to identify unique or shared effects on the microbiome. In this study, we analyzed 16S rRNA amplicon sequencing data derived from gastric mucosal samples for GC and stool samples for PD to indirectly assess potential shared microbial profiles. Here, we examined alpha diversity differences between GC and PD groups and their relative controls, revealing significant Shannon diversity changes associated with GC, but not with PD. Further, there were no shared taxa between the core microbiome of GC and PD. Indicator species analysis identified several genera that showed strong associations with GC, whereas no genera were significantly associated with PD, indicating distinct microbial signatures between the two disease states. In our differential abundance analysis, we found distinct, non-overlapping patterns of gut microbial dysbiosis in PD and GC, with PD showing relatively limited taxonomic shifts. In contrast, GC was associated with more extensive alterations in microbial composition, characterized by a greater number of significantly changed taxa and larger fold changes. Additionally, through our functional profiling, we observed significantly enriched metabolic signatures that were only revealed in the GC group. Overall, our findings suggest that GC and PD drive divergent changes to the microbiome, with GC exhibiting more severe dysbiosis than PD. These data show that each condition is characterized by a highly specific and non-overlapping microbial profile. Our work in this area suggests the need for a specialized and standardized dataset directly comparing the microbiome of GC and PD patients for further investigation.