Adiponectin, an adipokine secreted by adipocytes, is a well-known homeostatic factor for regulating glucose levels, lipid metabolism, and insulin sensitivity through its anti-inflammatory, anti-fibrotic, and antioxidant effects. Adiponectin is one of the hormones with the highest plasma concentrations. Weight loss or caloric restriction leads to increasing adiponectin levels, and this increase is associated with increased insulin sensitivity.

Aβ is a peptide derived from amyloid precursor protein (APP) by proteolytic cleavage of beta and gamma secretases. APP is a glycoprotein that plays a significant role in maintaining neuronal homeostasis like signaling, neuronal development, and intracellular transport. Aβ is reported to have both protective and toxic effects in neurons.

Aβ is a peptide derived from amyloid precursor protein (APP) by proteolytic cleavage of beta and gamma secretases. APP is a glycoprotein that plays a significant role in maintaining neuronal homeostasis like signaling, neuronal development, and intracellular transport. Aβ is reported to have both protective and toxic effects in neurons.

The HE4 gene encodes a WAP-type four disulphide core domain containing protein with a presumptive role in natural immunity. HE4 gene expression is highest in normal human trachea and salivary gland, but also active in lung, prostate, pituitary gland, thyroid and kidney.

Krebs von den Lungen-6 (KL-6) is a type of human MUC1 glycoprotein, whose glycopeptide sequence is recognized by a specific murine monoclonal antibody. KL-6 has a high expression by regenerating type II pneumocytes after epithelial injury.

Neurofilament light chain (NfL) is an intermediate filament protein that constitutes intermediate filaments, a part of the cytoskeleton, of neurons (intermediate filaments are sometimes referred to as nanofilaments). Together with the other four neuronal intermediate filament proteins, namely neurofilament heavy chain, neurofilament medium chain, alpha-internexin and peripherin, NfL assembles into neurofilaments, which are important for dendritic branching and growth and stability of axons in both central and peripheral nerves and for post-traumatic axonal regeneration. Axonal damage leads to NfL release into the extracellular space.

Parathyroid hormone is a peptide hormone secreted by the parathyroid glands, which are located adjacent to the thyroid gland. Parathyroid hormone alters serum calcium via actions on three target organs: bone, intestinal mucosa, and kidney.

Hyperphosphorylation of tau proteins is a characteristic pathological change in AD. There are many sites on the tau protein that may be phosphorylated at various disease stages from preclinical AD to mild cognitive impairment due to AD (MCI-AD) to clinical AD. P-tau181 has been extensively studied and has seen clinical applications such as the use of CSF p-tau181 in the prediction of cognitive decline in patients with MCI.

Hyperphosphorylation of tau proteins is a characteristic pathological change in AD. There are many sites on the tau protein that may be phosphorylated at various disease stages from preclinical AD to mild cognitive impairment due to AD (MCI-AD) to clinical AD. P-tau217 accumulation may differentiate AD from related diseases. The spread of p-tau217 in postmortem brain tissue has shown a correlation with antemortem plasma p-tau217 in those with amyloid plaques but not in those without, suggesting that plasma p-tau217 may reflect the presence of Aβ plaques.