Study Finds HAEE Peptide May Serve as Alzheimer's Biomarker

Engineered Molecule Matches a Natural Human Peptide

A synthetic peptide designed to treat Alzheimer's disease exists naturally in human blood.

Researchers led by Sergey A. Kozin published findings in the journal PNAS Nexus showing that the tetrapeptide Ac-His-Ala-Glu-Glu-NH₂ (HAEE) circulates in the human bloodstream. The authors originally synthesized the molecule in the laboratory to prevent amyloid-beta (Aβ) plaques from accumulating in brain tissue.

During early testing, the team identified the exact matching sequence in human blood samples.

Peptide Blocks Zinc Binding in Amyloid Monomers

The HAEE peptide directly disrupts the primary zinc-binding center in amyloid-beta (Aβ) monomers.

Abnormal interactions between zinc ions and amyloid-beta (Aβ) are considered a central step in the formation of brain plaques. Preventing plaque buildup remains an active research target because plaque accumulation is believed to precede and potentially trigger the spread of toxic tau protein.

Testing showed positive initial responses in mice while revealing that healthy human biology produces the identical compound independently.

Blood Levels Correlate with Clinical Disease Status

Concentrations of HAEE in blood decline as cognitive impairment advances.

The authors observed that HAEE levels track clinical disease stage, whereas circulating amyloid-beta (Aβ) levels stay indistinguishable between healthy volunteers and patients diagnosed with Alzheimer's disease.

Because baseline amyloid-beta (Aβ) measurements in blood often fail to separate healthy adults from affected individuals, tracking HAEE could provide a more distinct diagnostic signal.

Current Evidence and Research Caveats

The published evidence remains in the preliminary research phase and does not establish a proven diagnostic test.

The laboratory work demonstrated mechanistic activity in mice, but the study authors have not established whether low HAEE levels directly cause Alzheimer's disease or merely reflect ongoing neurodegeneration. Clinical diagnostic validation requires larger, prospective human cohort studies to confirm sensitivity and specificity across diverse populations.

The molecule is not an approved medication, so readers should discuss cognitive assessments and existing diagnostic options directly with a neurologist or primary care clinician.