Gut Microbiome Differences Between Early Alzheimer Disease and Idiopathic Normal Pressure Hydrocephalus

BACKGROUND: Alzheimer disease (AD) and idiopathic normal pressure hydrocephalus (iNPH) are neurodegenerative diseases causing memory decline. Previous studies have demonstrated an altered gut microbiome (GM) in both conditions. In this study, we compared the GM composition between the groups to find out how if the GM composition differed between the cognitively healthy individuals (CO) and AD groups, as well as between the AD and iNPH groups. METHODS: Thirty-seven CO participants, 21 mild AD patients and 10 participants with shunted iNPH gave fecal samples, which were subjected to 16S amplicon sequencing. Then, genus-level differences were analyzed. Information about comorbidities and diet was collected, and cognitive function was evaluated. RESULTS: Compared with the CO group, Anaerovorax and an unknown genus of the Comamonadaceae family increased, whereas Enterobacter, Absicoccus, Buttiauxella, Raoultella, and Lacticaseibacillus decreased in the AD group. Compared with the iNPH group, Paramuribaculum, an unknown genus of the Desulfovibrionaceae family, Ruficoccus and Mitsuokella increased, whereas Anaeromassilibacillus and Desulfovibrio decreased in the AD group. CONCLUSIONS: We demonstrated differences in the GM composition between the AD and CO groups, as well as between the AD and iNPH groups. To our knowledge, this is the first report to compare the 2 neurodegenerative diseases and demonstrate GM differences.