South Korea – A research team led by Professor Moon Cheil of the Department of Brain and Cognitive Sciences at Daegu Gyeongbuk Institute of Science and Technology (DGIST) has identified the reason why patients with the early stage of Alzheimer’s fail to smell.
The research team conducted a joint research with teams led by Professor Suh Yoo-Hun and Chang Keun-A at Gachon Medical School, which has revealed the relationship between the initial progression of Alzheimer’s and the olfactory dysfunction.
Alzheimer’s disease (AD) is the most representative degenerative brain disease, accounting for sixty to eighty percent of all dementia cases. The greatest known risk factor is aging as the majority of people with Alzheimer’s are 65 and older. In particular, Alzheimer’s disease is becoming a serious social problem in Korea as the number of patients with degenerative brain disease increases with the country entering an aging phase at an unprecedented rate.
Currently, there is no underlying cure for dementia, but early detection of dementia may help ameliorate or delay the onset of symptoms. Some of the drugs available in the market are also focused on relief or delay of symptoms rather than direct treatment of dementia. Since those treatments are effective only when administered in a timely manner, it is important to diagnose Alzheimer’s at an early stage.
In the initial stage of Alzheimer’s disease, it is known that a toxic protein called “beta- amyloid” is abnormally overexpressed, and accumulates in the brain and adversely affect neuronal cells.
The sooner Alzheimer’s is diagnosed, the greater the chance for perfect cure. Hence, there has been a worldwide effort underway to find an inexpensive, but accurate way to detect early-stage AD. In particular, recent studies have reported the association between Alzheimer’s and olfactory deterioration by suggesting that the initial symptoms of Alzheimer’s can be simply checked in the olfactory test using peanut butter. However, the specific mechanism was not clearly revealed.
Professor Moon’s research team paid attention to the olfactory dysfunction in the early stage of Alzheimer’s dementia and studied not only the brain, the central nervous system, but also the peripheral nervous system, the olfactory nervous system. The researchers carried out a behavioural experiment using an animal model with Alzheimer’s and have confirmed that the initial olfactory dysfunction, which is found in Alzheimer’s disease, is progressed in the six-month-old, earlier than in the fourteen-month-old when brain cognitive dysfunction occurs.
The AD brain has been histologically characterised by the presence of neuritic plaques – inflammatory lesion of nerves – and tangles of neuro-fibril, which are composed of protein aggregates of amyloid βß (Aß, beta-amyloid) and tau; the Aß is known to be expressed only in the central nervous system. However, the research team also detected direct expression of Aß in the olfactory epithelium, a peripheral nervous system, itself. Furthermore, it has also been proved that Aß has a fatal effect on the olfactory nerve cell in olfactory epithelium and directly induces the failure of olfactory function.
Professor Mon Cheil said: “We have discovered an important clue to predict the onset of Alzheimer’s disease in the early stage by identifying the mechanism of beta-amyloid expression in the initial stage of Alzheimer’s that was unknown until now. We will carry out the follow-up research that can be used for the development of early detection of dementia, dementia treatment technology, and more.”
Implemented by the Biomedical Technology Development Project which is supported by the Korea Research Foundation, the study was published in the online edition of Cell Death and Disease, the sister journal of Nature, on 10 August.