Brain Integration Therapies

Imaging Reveals Gut-Brain Connection in Alzheimer’s Disease

Researchers have used advanced X-ray imaging to study the connection between gut health and Alzheimer’s disease.

The study found structural changes in gut tissues of Alzheimer’s-affected mice, including abnormalities in intestinal cells and neurons.

These changes suggest that gut dysbiosis may allow harmful bacteria to escape into circulation and trigger brain inflammation.

Scientists say Alzheimer’s might not be a brain disease after all:

The common theory that Alzheimer's disease is caused by the buildup of beta-amyloid plaques in the brain is now being challenged by a new theory. Scientists say Alzheimer's may be an autoimmune disease.

This theory is based on 30 years of research. It suggests that beta-amyloid, rather than being an abnormal protein, is actually a component of the brain's immune system.

Its role is to protect the brain from injury and infection, but due to the similarity between the fat molecules in bacterial membranes and brain cell membranes, beta-amyloid mistakenly attacks the brain cells it's meant to defend. This leads to a chronic, progressive loss of brain function, ultimately resulting in dementia.

This autoimmune misfire redefines Alzheimer’s as a disorder of the immune system. The autoimmune theory opens up new avenues for treatment by focusing on immune-regulating pathways in the brain, rather than solely targeting beta-amyloid. It offers a promising new direction for research and treatment, potentially leading to more effective therapies for Alzheimer's disease.

Autoimmune diseases occur when your immune system mistakenly attacks your body's own tissues, leading to inflammation and damage. There are over 80 recognized types, including rheumatoid arthritis, lupus, and multiple sclerosis. Common symptoms include fatigue, joint pain, skin rashes, and fever. While the exact causes are unclear, factors like genetics, infections, and environmental exposures may contribute.

The gut–brain connection

“The gut is often described as a ‘second brain’. In fact, the walls of our gut are lined with about 10 million neurons. Known as the enteric nervous system, our gut can work independently of the central nervous system, the processing centre that includes the brain and spinal cord. That means your brain doesn’t have to get involved with the messy daily grind of digestion and excretion. Our two ‘brains’ communicate via the vagus nerve, one of the 12 major nerves that link the body to the brain. Messages from the gut to the brain (and vice versa) travel through this information superhighway, and research is ongoing into this gut–brain connection.

A growing body of research suggests that our microbes also communicate with our brain. Gut bacteria could influence brain chemistry through various pathways. Gut microbes produce neurotransmitters—chemicals such as serotonin, dopamine and GABA that transmit messages to the brain. Our microbiome also influences the immune system, which itself impacts mood and behaviour.”

Communication happens many different ways. A few ways the gut and brain communicate are as follows:

1. Microbes interact with immune cells in the gut. This prompts the cells to make cytokines (proteins used in cell signalling) that circulate to the brain through the bloodstream.

2. Microbes also interact with gut cells called enteroendocrine cells that produce neuroactive molecules. These molecules interact with the vagus nerve, which sends signals to the brain.

3. Microbes produce neurotransmitters and chemical compounds called metabolites (such as butyrate) that circulate to the brain. If they are small enough, they can cross the blood–brain barrier, while others alter cell activity at the barrier.

From: https://www.science.org.au/curious/people-medicine/secret-world-your-microbiome