New Delhi: A new laboratory-based study has revealed that early warning signs of Alzheimer’s develop in nerve-muscle connections, long before any changes in the brain or spinal cord.
The study was published in Alzheimer’s and Dementia by researchers at the University of Central Florida (UCF). They used a ‘human-on-a-chip’ technology, through which scientists can recreate biological functions of an actual human in controlled laboratory conditions using human cells.
The researchers, from UCF’s Hybrid Systems Lab and the Michigan State University College of Human Medicine, focused on familial Alzheimer’s, which is a rare, genetic disease that develops in the later stages of life. They found that certain genetic mutations that are associated with Alzheimer’s can transform how muscles send signals to each other. These mutations, found in motor neurons, change muscle control in people, leading to difficulty in walking, sensation, and other physical movements.
“You can’t move unless the motor circuit works. When a doctor taps your knee to check your reflex, they’re testing that exact connection,” James Hickman, one of the authors of the study, said in a press release.
According to the study, these motor difficulties are often the first “early warning signs” of the disease, and they develop outside the normal confines of Alzheimer’s — the brain and the spinal cord.
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The neuro-muscular connection in Alzheimer’s
Alzheimer’s is a neurodegenerative disorder most commonly associated with the loss of memory, thinking skills. It is a major healthcare challenge with nearly 34 million to 40 million people globally living with the disease, according to the World Health Organisation.
In the experiment, scientists recreated a model of the neuromuscular junction on a chip. This junction is where motor neurons communicate with muscle cells and transfer directions to the cells to act a certain way. The scientists ensured that they created a model that did not include the brain or the spinal cord, and used both healthy stem cells and cells that carried the Alzheimer’s genetic mutation.
They found that the Alzheimer’s genetic mutation could interfere with the normal function of the neuromuscular junction, even without a signal from the brain. This, the study said, indicates that the peripheral nervous system is also independently affected by Alzheimer’s, which causes motor deficits.
This contradicts the theory that all Alzheimer’s related deficiencies arise due to “upstream” or “central” circuits like the brain. Moreover, the study also pointed out that the diagnosis of Alzheimer’s needs to move beyond brain, memory and cognitive symptoms.
It is not yet clear whether these motor deficiencies and problems in the neuromuscular system arise before or during the memory loss phase of Alzheimer’s. While this requires further research, the USF scientists showed that the disease and the genetic mutation associated with it can manifest itself across the body, and is not limited to the brain.
(Edited by Janaki Pande)