Scientists have long searched for simple ways to detect Alzheimer’s disease early. In recent years, a protein found in the blood called phosphorylated tau, often shortened to pTau, has gained attention as a promising early indicator of the disease.
However, new research suggests that this protein may not only be linked to Alzheimer’s. It may also appear in other illnesses that affect completely different organs.
Researchers from the German Center for Neurodegenerative Diseases (DZNE) and the Hertie Institute for Clinical Brain Research at the University of Tübingen have discovered that high levels of pTau can also occur in two lesser-known diseases that mainly affect the heart and kidneys.
Their findings suggest that this blood marker may reflect a broader biological response in the body rather than being specific to Alzheimer’s disease alone. The study was published in the scientific journal Nature Medicine.
The research team examined medical data and blood samples from 280 older adults from Germany, Italy, and the Netherlands. Some of the participants were diagnosed with a group of rare conditions known as systemic amyloidosis.
These diseases occur when certain proteins in the body fold incorrectly and build up in tissues. When proteins lose their normal shape, they can form sticky clumps called amyloids. These deposits can damage organs and interfere with their normal function.
Two particular forms of systemic amyloidosis were investigated in this study: transthyretin amyloidosis and immunoglobulin light-chain amyloidosis. These are the most common types of systemic amyloidosis. Although they are rare compared with many other diseases, they can have serious health effects.
Unlike Alzheimer’s disease, which mainly affects the brain, systemic amyloidosis usually damages organs such as the heart and kidneys. In transthyretin amyloidosis, a protein called transthyretin forms amyloid deposits that can weaken the heart and cause nerve damage.
In immunoglobulin light-chain amyloidosis, abnormal proteins produced by immune cells accumulate in organs and may lead to heart failure, kidney damage, and other complications.
Even though these diseases involve different organs and different proteins than Alzheimer’s disease, the researchers noticed something surprising. People with systemic amyloidosis often showed increased levels of pTau in their blood.
This protein is normally associated with nerve cells and has been widely studied as a marker for Alzheimer’s disease. Its presence in people with heart and kidney diseases suggests that the body may release pTau in response to stress caused by amyloid deposits, regardless of where they occur.
Professor Mathias Jucker, a scientist at DZNE and the University of Tübingen, explained that this discovery changes how scientists should interpret pTau levels. According to him, the results show that high levels of this protein are not unique to Alzheimer’s disease. Instead, they may occur in several conditions that involve abnormal protein buildup.
This insight could be useful for improving the diagnosis of systemic amyloidosis. Detecting these diseases early is often difficult because symptoms can vary widely and may resemble those of other conditions. A simple blood test that measures pTau could help doctors identify patients who may need further testing for amyloidosis.
At the same time, the findings also highlight an important limitation of using pTau as a diagnostic marker for Alzheimer’s disease.
Some researchers have suggested that blood tests for pTau could eventually be used to diagnose Alzheimer’s quickly and easily. However, the new study shows that elevated levels of this protein alone do not necessarily mean a person has Alzheimer’s.
Doctors will still need to consider other medical information, such as cognitive tests, brain imaging, and additional biomarkers, when evaluating patients. This is especially important for people who show no clear signs of memory loss or cognitive decline.
The discovery may also help doctors diagnose another condition called polyneuropathy. This disorder affects the peripheral nerves and can cause symptoms such as tingling, numbness, weakness, and pain in the hands and feet. Polyneuropathy has many possible causes, including diabetes, infections, and autoimmune diseases.
In some patients, systemic amyloidosis is responsible for the nerve damage. The researchers believe that measuring pTau levels could help doctors determine whether polyneuropathy is related to amyloid diseases or caused by something else.
Scientists are still trying to understand exactly why pTau levels rise in these different conditions. Professor Jucker believes that the increase may be part of a stress response in the body. When organs are exposed to abnormal protein deposits, cells may release pTau as a signal of damage or stress.
Interestingly, similar temporary increases in pTau have been observed in animals that hibernate. During hibernation, certain brain processes slow down, and elevated pTau may help protect nerve cells during this unusual state. This suggests that the protein may sometimes play a protective role rather than only being a sign of disease.
Overall, the study suggests that pTau may be part of a general biological reaction to protein-related stress in the body. Instead of being limited to Alzheimer’s disease, this response may occur in several disorders involving abnormal protein deposits.
The findings provide valuable insight for both neurologists and other medical specialists. Understanding when and why pTau levels increase could help doctors interpret blood test results more accurately and avoid misdiagnosis.
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The research findings were published in the journal Nature Medicine.
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