INS and early-onset autosomal dominant Alzheimer disease: From a pragmatic standpoint, these biomarkers can be used as predictive or diagnostic tools in various diseases with impaired insulin signaling, such as Parkinson's (Blommer et al., 2023) and Alzheimer's disease (Kapogiannis et al., 2015, 2019), but also as probes for studying neuronal cell physiology and its response to interventions in living humans (Kapogiannis et al., 2024), which is the main purpose of the present study.