Alzheimer’s disease is one of the most common causes of dementia in older adults. It is a progressive brain disorder that slowly damages memory, thinking ability, and everyday functioning.
Over time, people with Alzheimer’s disease may struggle to remember recent events, recognize loved ones, or carry out simple daily tasks.
As the disease advances, it can lead to severe mental decline and loss of independence.
For many years, scientists have tried to understand what causes Alzheimer’s disease and how it develops inside the body. One of the most important clues involves a protein called amyloid-beta, often shortened to Aβ.
In people with Alzheimer’s disease, this protein builds up in the brain and forms sticky clumps called amyloid plaques. These plaques interfere with communication between nerve cells and eventually lead to the death of neurons.
Researchers believe that amyloid-beta begins to accumulate in the brain many years before obvious symptoms appear. By the time memory problems are noticeable, significant damage may have already occurred. Because of this, scientists are searching for early signs of the disease and ways to slow down or stop the buildup of amyloid-beta before it causes serious harm.
Interestingly, some earlier studies have shown that people who later develop Alzheimer’s disease often experience digestive problems many years before their memory declines.
Symptoms such as constipation and difficulty moving food through the digestive system are commonly reported. This observation has led scientists to wonder whether Alzheimer’s disease may also affect the gut, not just the brain.
A new study conducted by researchers at Nantes University in France explored this idea in greater detail. Their findings were published in the scientific journal Molecular Psychiatry. The researchers investigated whether amyloid-beta might accumulate not only in the brain but also in the gut, and whether this buildup could damage the nervous system that controls digestion.
The digestive system contains its own network of nerves known as the enteric nervous system, or ENS. Sometimes this system is called the “second brain” because it controls many digestive processes, including the movement of food through the intestines. If the ENS becomes damaged, digestion may slow down or become irregular.
In their research, the scientists used a special strain of mice known as SAMP8 mice. These animals naturally develop symptoms similar to Alzheimer’s disease as they age, making them a useful model for studying the condition. The researchers measured levels of amyloid-beta in the mice’s brains, blood, and digestive systems.
They also examined enzymes that either produce or break down amyloid-beta. One enzyme, called BACE1, helps create amyloid-beta, while another enzyme, called neprilysin, helps remove it from the body. The balance between these enzymes plays an important role in controlling how much amyloid-beta accumulates.
The researchers found that the Alzheimer’s-like mice had high levels of amyloid-beta in their gut even before clear memory problems appeared. At the same time, the enzyme that produces amyloid-beta was more active, while the enzyme that breaks it down was less active. This imbalance led to increased amyloid buildup in the digestive system.
The study also showed that this buildup damaged the nerve connections inside the enteric nervous system. As these connections weakened, the mice developed digestive problems similar to those seen in people with Alzheimer’s disease. These findings suggest that amyloid-beta may disrupt gut function long before it causes major memory loss.
To explore possible treatments, the researchers tested a molecule called butyrate. Butyrate is a short-chain fatty acid that is naturally produced by beneficial bacteria in the gut when they break down dietary fiber. It has already been studied for its anti-inflammatory and protective effects in the body.
When the scientists gave butyrate to the mice, they observed several positive changes. The treatment reduced the production of amyloid-beta and helped protect the nerve connections in the digestive system. It also lowered inflammation in the brain and prevented the memory problems that usually develop in these mice.
In other words, butyrate appeared to protect both the gut and the brain in this Alzheimer’s disease model. The treated mice showed fewer digestive issues and better memory compared with untreated animals.
The research team also tested the effects of amyloid-beta in laboratory-grown models of human gut tissue. These experiments showed similar results. Amyloid-beta damaged nerve connections in the gut, supporting the idea that the protein can harm both brain and digestive systems.
These findings highlight the possibility that Alzheimer’s disease may involve a complex interaction between the brain and the gut. If amyloid-beta can travel between these organs, the gut might play an important role in how the disease develops.
The study also suggests that molecules produced by gut bacteria, such as butyrate, could potentially help protect against the buildup of harmful proteins. Because butyrate is created when gut bacteria digest fiber-rich foods, diet and gut health may play an important role in brain health.
However, it is important to note that this research was conducted mainly in mice and laboratory models. More studies involving human patients will be necessary before scientists can determine whether similar treatments might work in people.
One strength of the study is that it examined several different systems at once, including the brain, blood, and digestive tract. This broader approach provides new insights into how Alzheimer’s disease might affect the body beyond the brain alone.
At the same time, researchers caution that the results should be interpreted carefully. Animal studies do not always translate directly to human treatments. More clinical research will be required to confirm whether butyrate or other gut-related therapies could slow Alzheimer’s disease in humans.
Even so, the findings open an interesting new direction for Alzheimer’s research. Instead of focusing only on the brain, scientists may need to consider the role of the gut and the microbiome in the early stages of the disease.
If future studies confirm these results, therapies that support healthy gut bacteria or increase beneficial molecules like butyrate could one day help prevent or slow the development of Alzheimer’s disease.
If you care about Alzheimer’s, please read studies about Vitamin D deficiency linked to Alzheimer’s, vascular dementia, and Oral cannabis extract may help reduce Alzheimer’s symptoms.
For more information about brain health, please see recent studies about Vitamin B9 deficiency linked to higher dementia risk, and results showing flavonoid-rich foods could improve survival in Parkinson’s disease.
The study was published in the journal Molecular Psychiatry.
