APP and Alzheimer disease: Bauerl et al. (2018) analyzed the gut microbiota of APP/PS1 transgenic AD mice and found that the α diversity of APP/PS1 mice aged 24 months and 6 months was lower than that of wild-type mice of the same age, and the gut microbiota structure of the two groups was significantly different. However, Bonfili et al. (2017) and Peng et al. (2018) found that there was no significant difference in α diversity between aging mice and 3 × Tg-AD mice and control mice, while β diversity showed a significant difference in gut microflora structure compared with control mice.