DKK1 and Alzheimer disease: The bone density of patients with AD was lower than that of the control group.257 Fourteen bone-related biomarkers in elderly people with memory problems were not clinically diagnosed with asymptomatic AD, and the expression of TRAIL and DKK1 was elevated in the brain.257,258 Wnt signalling has a neuroprotective effect, and DKK1, as an antagonist of the canonical Wnt signalling pathway, is negatively correlated with changes in cognitive function.259 Therefore, TRAIL and DKK1 most likely predict cognitive decline and may become potential biomarkers for the diagnosis of AD.260