MAPT and tauopathy: Here, we demonstrated that P. gingivalis-derived PGDHC increased the expression of APP protein and production of soluble Aβ42 peptide in CHO7W10 cells (Figure 1) as well as hyperphosphorylation of tau protein in SH-5Y-SY cells in vitro (Figure 2), indicating a potential contribution of oral bacterial-derived dihydroceramides in amyloidogenesis and tauopathy.