Indirect evidence of increased CD38 expression is provided by the observation of decreased levels of NAD (Sonntag et al., 2017), as well as by a decline in CD38 expression-inhibiting miRNAs in the CSF of AD patients compared to age-matched controls (Denk et al., 2015; Guerreiro et al., 2020). This evidence concerns the gene CD38 and Alzheimer disease.