Protein released from muscles during exercise may serve as an “early warning” indicator of dementia risk, according to a domestic research finding. Observers say this opens the way to identify the risk of Alzheimer’s disease before symptoms appear, using only a simple blood test. In particular, there is growing academic interest in whether this could lead to a new diagnostic method that complements expensive brain imaging tests costing in the KRW 1 million range.

According to Korea University Guro Hospital on the 17th, a research team led by Professor Kang Sung-hoon of the Department of Neurology has, through joint research with Professor Jung Young-hee of the Department of Neurology at Hallym University Pyeongchon Sacred Heart Hospital, Professor Lee Eun-sung of the Department of Nuclear Medicine at Korea University Guro Hospital, and Professor Kim Hyun-soo of the Department of Anatomy at Korea University College of Medicine, identified the association between the muscle protein “irisin” and the onset of Alzheimer’s disease.

Alzheimer’s disease is a representative degenerative brain disorder in which a toxic protein called “amyloid beta” abnormally aggregates in the brain, destroys nerve cells, and impairs memory. Previous animal experiments reported that irisin promotes the clearance of amyloid protein, but studies that closely tracked the correlation between the two substances in humans have been rare.

The research team conducted brain positron emission tomography (PET), neuropsychological tests, and blood tests on 100 older adults ranging from the asymptomatic preclinical stage of Alzheimer’s disease to severe dementia. Subjects were classified into four groups according to the presence of amyloid accumulation in the brain and the degree of cognitive decline. Analysis showed that in all three groups with amyloid accumulation in the brain, blood irisin levels were significantly lower than in the healthy group. A clear inverse relationship was also confirmed in which the higher the irisin level, the lower the “Centiloid” index, a quantified measure of brain amyloid burden. The results indicate that reduced irisin in the body is closely associated with brain amyloid accumulation and cognitive decline.

What the medical community is paying close attention to is the pathological changes identified even before dementia symptoms become outwardly apparent. Even among older adults in the “asymptomatic” stage, whose cognitive function is still normal but in whom amyloid has begun to accumulate gradually in the brain, irisin concentrations were significantly lower. This suggests the possibility that a simple blood test could identify the risk of Alzheimer’s disease long before patients become aware of any memory decline. However, larger-scale follow-up studies and clinical validation are required before irisin can be used as an early screening biomarker.

At present, a definitive diagnosis of Alzheimer’s disease in clinical practice requires cerebrospinal fluid testing or brain imaging examinations costing in the KRW 1 million range, which impose a significant physical and financial burden on patients. If a testing method using blood irisin is introduced into clinical practice, it would be possible to first identify high-risk individuals and narrow down the group requiring confirmatory testing, thereby reducing patient burden and improving medical accessibility.

Professor Kang stated, “This research confirms in actual human subjects that irisin, which increases with exercise, is closely linked not only to muscle health but also to the core pathology of Alzheimer’s disease,” adding, “It is expected to provide important evidence for developing blood-based biomarkers using irisin in the future, as well as for establishing dementia prevention strategies through exercise and improvement of muscle function.” The research findings were recently published in an international journal of the Alzheimer’s Association.

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