KLK6 and Alzheimer disease: Previous studies have shown that NPTXR levels are reduced in the CSF and plasma of individuals with AD compared to cognitively normal individuals.60,61 NPTXR is a protein primarily found in neurons and plays a key role in synapse organization, and altered levels can also be detected in plasma, making it a potential biomarker for distinguishing AD from controls, as demonstrated in a recent study.37 KLK6 is involved in the regulation of neuronal function and the breakdown of amyloid-beta plaques in Alzheimer’s disease37,40.