Microbes in the gut could play a role in the development of ALS, early studies suggest.
Research in mice indicates there is a change in some bacteria before symptoms of motor neuron dysfunction appear.
Enhanced levels of certain bacterial species were found to exacerbate disease progression.
Whereas the abundance of others, such as Akkermansia muciniphila, were reduced during disease progression.
Scientists found that replenishing the levels of this bacteria improved symptoms and prolonged survival in the mouse model of amyotrophic lateral sclerosis (ALS).
In the study, published in Nature, the researchers pinpointed a number of genes that were altered by A. muciniphila or nicotinamide – the chemical it produced.
Researchers from the Weizmann Institute of Science in Israel stress their findings are preliminary and that much more work is needed.
In a small-scale human study of 37 patients with ALS and 29 controls, the authors also observed a change in the composition of gut microbes, and reduced levels of nicotinamide.
They say these preliminary human findings are not sufficient to constitute a treatment recommendation and require validation in a larger prospective cohort of patients.
ALS, a form of the disease that affected Stephen Hawking, is a neurodegenerative disease with an average survival rate of three to five years from diagnosis.
Dr Brian Dickie, director of research development at the Motor Neurone Disease Association, said: “There is increasing evidence from a wide variety of sources that the bacteria in our gut can play a role in a wide-range of neurological conditions, though ALS has not been as widely studied as other conditions such as multiple sclerosis, Parkinson’s disease, Alzheimer’s disease and stroke.
“These are important new findings, which support the theory that certain bacteria may play a disease-modifying role in ALS and that this may occur though changes in a particular metabolic pathway.
“This adds to an emerging, but still fuzzy, picture of a different metabolism that seems to occur in people with ALS. Diet and exercise are also being studied as potential factors associated with the disease.”