Vitreous Humor Biomarkers Show Strong Link to Alzheimer's Disease

A recent study conducted at Boston Medical Center has uncovered a significant connection between biomarkers present in the vitreous humor of the eye and confirmed cases of Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE) in post-mortem brain and eye tissue. This groundbreaking research suggests that biomarkers in the vitreous humor could serve as an indicator for neuropathological diseases.

The prevalence of dementias like AD continues to rise, with 6.2 million individuals aged 65 and above in North America affected by AD as of 2021, and projections estimate this number to reach 13.2 million by 2060. Currently, the diagnosis of AD and CTE relies on symptoms, clinical examinations, and cognitive tests, with confirmation only possible through post-mortem brain examinations.

Neuropathological changes associated with Alzheimer's disease occur decades before the onset of symptoms, limiting the therapeutic effects by the time a patient is diagnosed. Therefore, the identification of biomarkers that can predict the disease before symptoms manifest is a crucial focus in AD research.

Individuals with eye diseases face an elevated risk of developing neurodegenerative diseases, and previous studies have established a connection between neurodegenerative disorders and ophthalmic conditions like glaucoma, diabetic retinopathy, age-related macular degeneration, and cataracts. It is known that patients with these eye conditions have an increased likelihood of developing AD, underscoring the importance of investigating biomarkers in this at-risk population to understand their role in early diagnosis.

Dr. Manju Subramanian, an ophthalmologist at Boston Medical Center and an associate professor in ophthalmology at Boston University Chobanian & Avedisian School of Medicine, commented, "To our knowledge, this is the first study to investigate the role of vitreous fluid biomarkers and link it to confirmed post-mortem brain tissue pathological examination of AD. In addition, this is the first study to find a link between vitreous fluid biomarkers and confirmed CTE. Our findings provide further evidence to support the potential role of vitreous biomarkers in early diagnosis and prognostication of diseases like AD and CTE."

The research team identified a correlation between biomarkers, including total Tau and neurofilament light-chain (NfL), and pathologically confirmed AD and CTE. The presence of altered levels of these neurodegenerative proteins in the vitreous fluid indicates that the eye reflects neuropathological changes occurring in the brain. These findings reinforce the importance of investigating the eye's potential role in diagnosing these diseases.

The study's findings build upon the authors' previous research, which demonstrated a link between biomarkers in vitreous fluid and cognitive function in individuals with both normal cognition and mild cognitive impairment. These findings provide a solid foundation for future studies aiming to explore the role of biomarkers and other eye fluids in the diagnosis, prognosis, and management of diseases such as AD and CTE.

The research paper detailing these findings has been published in the Journal of Alzheimer's Disease.

Reference

Viha Vig et al, Vitreous Humor Biomarkers Reflect Pathological Changes in the Brain for Alzheimer's Disease and Chronic Traumatic Encephalopathy, Journal of Alzheimer's Disease (2023). DOI: 10.3233/JAD-230167