CHI3L1 and Alzheimer disease: They found that age was associated with increases in three CSF markers of glial activation, glial fibrillary acidity protein (GFA), chitinase-3-like protein (YKL-40), and soluble triggering receptor expressed on myeloid cell 2 (sTREM2), two biomarkers of AD (total and phosphorylated tau), and measures of synaptic (α-synuclein [16]) and axonal integrity (neurofilament light chain [NfL]).