Excessive endoplasmic reticulum (ER) stress has also been implicated in this process, as transplantation of microbiota from AD patients or APP/PS1 mice into recipient mice leads to dysbiosis and heightened ER stress in the cerebral cortex, mediated by trimethylamine-N-oxide (TMAO) (Wang et al., 2022). This evidence concerns the gene APP and Alzheimer disease.