St Petersburg University doctors find new potential biomarkers of Alzheimer’s disease

The research findings are published in Neurology, Neuropsychiatry, Psychosomatics.

Alzheimer’s disease, according to the World Health Organization, is the most common cause of dementia in elderly people. Early diagnosis ensures timely drug therapy, prevents deterioration, and significantly improves the quality of life of patients. However, Alzheimer’s disease often develops latently for a long time. This makes timely diagnosis difficult.

Informative biomarkers, i.e. so-called labels or characteristics, enable us to find deviations from the norm and draw a conclusion about the presence of pathologies. They are indicators of biological processes in the human body, including pathological ones that lead to the development of diseases. These characteristics can be obtained from various sources. Among there are: molecular or histological examination; radiography; and physiology or psychological tests. Today, there are several ways to detect Alzheimer’s disease. They reflect protein metabolism disorders and neuronal degeneration, i.e. deterioration of neurons and a decrease in cognitive functions. However, for early diagnosis of the disease, the search for more accurate markers is important. This will ensure that we can mark other links of neurodegenerative diseases that are characterised by progressive cell death that leads to degeneration of the nervous tissue.

The scientists from St Petersburg University identified biomarkers that characterise changes in patients with Alzheimer’s disease. In future, they can be used as an auxiliary diagnostic criterion for assessing the severity of the disease. Additionally, the scientists found differences in the concentrations of biomarkers in patients with different severity of cognitive deficits. This may show various biological processes caused by the progression of the disease. In future, they may serve as a potential indicator of the presence of an active neurodegenerative process.

In medicine, there are three stages of Alzheimer’s disease. They are: asymptomatic preclinical stage; pre-dementia; and dementia.

The use of biomarkers enables us to detect the causes of deviations from the norm in patients with no symptoms or with their mild manifestations even at the first asymptomatic stage, said Sergey Shcherbak, Head of the Department of Postgraduate Medical Education at St Petersburg University.

Today, biomarkers obtained from cerebrospinal fluid are used to diagnose Alzheimer’s disease. Yet the accuracy of the results largely depends on the research centres and the equipment used. Additionally, the process of taking a sample of cerebrospinal fluid, i.e. lumbar puncture, is an invasive and demanding procedure, especially for elderly people who are most susceptible to Alzheimer’s disease.

World Alzheimer’s Day is celebrated on 21 September each year. It was established by organisations that research the disease in 1994.

The study of biomarkers for the detection of Alzheimer’s disease was carried out by scientists at St Petersburg University together with specialists from the Kirov Military Medical Academy and North-Western State Medical University named after I.I. Mechnikov at City Hospital No 40 of the Kurortny District of St Petersburg.

The doctors from St Petersburg University suggest studying blood test to determine biomarkers. The relationship between their concentration in blood plasma and cerebrospinal fluid has already been discovered and it is also in line with the results of neuropsychological texts. This simplifies the diagnosis, because blood test is a much simpler way to search for biomarkers of Alzheimer’s disease compared to lumbar puncture.

According to the results of the studies, the doctors identified the most promising biomarker in blood plasma, i.e. sICAM-1. It is a soluble cell adhesion molecule and an indicator of endothelial dysfunction. It is also found in older adults with vascular cognitive impairment. This marker reflects the disruption of the endothelium in patients not only with vascular cognitive impairment, but also with an active neurodegenerative process at the stage of dementia.

The scientists found other biomarkers that were also promising for detecting specific abnormalities. For example, IL-IRA scores can be considered as a diagnostic marker in the early stages of the disease. The G-CSF biomarker, in its turn, can be considered as a potential diagnostic biomarker for Alzheimer’s disease at the stage of dementia.

‘There are stereotypes that the brain is divided from blood flow by the blood-brain barrier, i.e. a system that protects the brain from the action of foreign and toxic substances and participates in the transport of substances from the blood to the brain. Yet in neurodegenerative diseases, the inflammatory processes in the brain can not only worsen and intensify neurodegeneration, but also protect brain cells from damaging effects. In other words, they perform a neuroprotective function,’ said Sergei Shcherbak, Head of the Department of Postgraduate Medical Education at St Petersburg University.

If this happens regularly, the efficiency of splitting amyloid plaques in the body decreases. Formation of amyloid plaques is considered the main cause of neuronal death in Alzheimer’s disease.

At City Hospital No 40, the scientists examined 52 patients with Alzheimer’s disease. Among there were 39 women aged 64 to 80 and 13 men aged 58 to 79. The scientists performed positron emission tomography of the brain using deoxyglucose. The results of the study confirmed disturbances in the functioning of brain structures. These results are in line with the results of blood tests.

All participants underwent neuropsychological studies using seven tests to detect cognitive impairment. The scientists assessed visuospatial and control functions, attention, speed of thought processes, and hand-eye coordination. All patients had cognitive disorders of varying degrees. This, with further development of Alzheimer’s disease, leads to gradual deterioration of cognitive functions and motor impairment.

Today, the diagnosis of Alzheimer’s disease by the results of blood test is not a common practice. The biomarkers in blood serum isolated by the group of doctors were studied in several tests and proved to be effective. In future, they can be used for simple diagnosis of Alzheimer’s disease in the early stages. However, as the scientists said, additional studies are needed for the method to be applied in real clinical practice.