More recently, in 2020, Gu et al. [114] measured the levels of Aβ42, P-T181-tau, P-S396-tau, and other inflammatory biomarkers, including interleukin 6 (IL-6) and matrix metalloproteinase-9 (MMP-9), in the plasma NDEs of AD and control patients. Here, MMP9 is linked to Alzheimer disease.