Table 2.

Common biomarkers linked to Alzheimer’s disease pathology. This table summarizes the widely examined biomarkers associated with AD and reflects the different methods of pathogenesis [42,43]. Abbreviations: T-tau, total tau; P-tau, phosphorylated tau; NfL, neurofilament light; GFAP, glial cell line-derived neurotrophic factor.

Biomarker		Importance
Amyloid biomarkers	APP	APP cleavage by γ- and β-secretases results in Aβ formation
	Aβ42/Aβ40	Reduced Aβ42/Aβ40 ratio is observed in AD
Tau biomarkers	T-tau	Elevated in prodromal and dementia AD
	P-tau	Hyperphosphorylation of tau leads to NFT formation Elevated in prodromal and dementia AD High P-tau in CSF is only observed in AD
Neural damage biomarkers	NfL	Marker for acute brain damage and neurodegeneration, but not specific for AD
	S100β	High levels correlate with greater brain atrophy
Neuroinflammation biomarkers	GFAP	Marker of astrocyte activation Observed to be higher in preclinical AD cases
	TNF-α	Pro-inflammatory cytokine frequently reported to be elevated in blood plasma and CSF of AD patients
	IL-β	Promotes Aβ plaque and NFT formation
Synaptic biomarkers	α-synuclein	Elevated in CSF of MCI and AD patients
	Neurogranin	High neurogranin is observed in AD and reflects synaptic (dendritic) degeneration
Metabolic biomarkers	ApoE	Major lipid transporter in the brain May lead to synaptic defects and cognitive impairments
	GDNF	Promotes dopamine uptake in dopaminergic neurons Significant decrease reported in AD patients