Plasma beta-amyloid, tau, neurodegeneration biomarkers and inflammatory factors of probable Alzheimer's disease dementia in Chinese individuals

BackgroundPlasma-derived beta-amyloid, tau, and neurodegeneration (ATN) biomarkers can accurately diagnose Alzheimer's disease (AD) and predict its progression. Few studies have investigated the relationship between plasma biomarkers and changes in plasma inflammatory markers in clinically diagnosed AD. MethodsSeventy-four participants were recruited, including 30 mild-to-moderate AD dementia patients and 44 normal controls (NC). All participants underwent neuropsychological testing and blood sampling for biomarker testing. AD was clinically diagnosed according to the National Institute on Aging-Alzheimer's Association (NIA-AA) core criteria and required age-mismatched hippocampal atrophy. We performed Single Molecule Array (Simoa), an ultra-sensitive enzyme-linked immunosorbent assay (ELISA), to examine plasma ATN markers, including beta-amyloid (A beta) 40, A beta 42, p-tau181, total (t)-tau, neurofilament protein light chain (NfL), and inflammatory factors (TNF-alpha, IL-1 beta, IL-6, and IL-8). ResultsThe level of the plasma A beta 42/A beta 40 ratio was significantly declined and the levels of the plasma p-tau181, NfL and TNF-alpha were significantly higher in the AD group than the NC group, but there was no significant difference in the levels of plasma t-tau, IL-1 beta, IL-6, and IL-8 between the AD and NC groups. The levels of plasma p-tau181, NfL, A beta 42/A beta 40 ratio, and TNF-alpha were all associated with impairments in multiple cognitive domains. Among them, the plasma A beta 42/A beta 40 ratio, and the p-tau181 and TNF-alpha levels were associated with impairments in global cognition, memory, and visuospatial abilities, but not with executive function, only plasma NfL level was associated with executive function. Plasma NfL showed higher diagnostic performance in AD than in NC individuals (AUC = 0.833). A combined diagnostic prediction model of plasma A beta 42/A beta 40 ratio, p-tau 181, and NfL had the highest value than each factor alone (AUC = 0.902),with a sensitivity and specificity of 0.867 and 0.886, respectively. ConclusionThe levels of plasma ATN biomarkers (A beta 42/A beta 40 ratio, p-tua181, and NfL) were significantly changed in clinically diagnosed AD patients and they all associated with different domains of cognitive impairment. Plasma ATN biomarkers better differentiate mild-to-moderate AD dementia from NC when they are incorporated into diagnostic models together rather than individually. Plasma ATN biomarkers have the potential to be a screening tool for AD. However, the expression of inflammatory factors in AD patients requires further research.