Gut Bacteria Found to Trigger ALS and Dementia in Major New Research

Researchers at Case Western Reserve University have identified a specific mechanism by which gut bacteria may trigger or accelerate the neurodegenerative diseases ALS and frontotemporal dementia, opening a pathway toward potential treatments that target the gut-brain axis rather than the brain itself. The study found that 70% of ALS and FTD patients carried elevated levels of a harmful form of glycogen — a type of sugar — produced by gut bacteria, compared to roughly one-third of individuals without the diseases. Reducing these bacterial sugars in experimental models improved brain health and extended lifespan, raising hopes for clinical interventions that could be tested within the next year.

ALS, or amyotrophic lateral sclerosis, and frontotemporal dementia are both associated in their most common genetic form with a mutation in the C9ORF72 gene — the most frequent known genetic cause of either disease. Prior research has shown that individuals with this mutation also tend to have altered gut microbiome compositions, but the causal chain connecting gut bacteria to brain cell death has been unclear. The Case Western team, led by Aaron Burberry in the Department of Pathology and Alex Rodriguez-Palacios of the Digestive Health Research Institute, identified a specific class of bacterial glycogen as the likely culprit.

"We found that harmful gut bacteria produce inflammatory forms of glycogen, and that these bacterial sugars trigger immune responses that damage the brain," Burberry said. The study involved analysis of 23 ALS and FTD patients carrying the C9ORF72 mutation. In those patients, elevated gut bacterial glycogen levels correlated with markers of neuroinflammation — the chronic, low-grade immune activation in the nervous system that is increasingly recognized as a driver of neurodegeneration across multiple diseases, including Alzheimer's disease and Parkinson's.

The mechanistic model the researchers propose runs as follows: certain gut bacteria with the C9ORF72 genetic background overproduce inflammatory glycogen forms; those sugars leak from the gut environment into systemic circulation; the immune system mounts a response that, in genetically susceptible individuals, triggers inflammation in the central nervous system; and that neuroinflammation contributes to the death of motor neurons in ALS or the death of frontal lobe neurons in FTD. The finding suggests that the gut is not merely a passive bystander in these diseases but an active contributor to their progression.

Fabrizio Cominelli, the Distinguished University Professor who directs Case Western's Digestive Health Research Institute and is a co-author of the study, said the results could have broad implications beyond the C9ORF72-associated forms of ALS and FTD. "Many neurodegenerative diseases involve neuroinflammation, and many patients with these conditions also show gut microbiome dysregulation," Cominelli noted. "Whether inflammatory bacterial glycogen is a shared mechanism across those conditions is a question we're actively investigating."

The practical implications of the research are significant. Unlike interventions targeting the brain directly — where the blood-brain barrier makes drug delivery notoriously difficult — the gut is far more accessible. Approaches that reduce the population of glycogen-overproducing bacteria, neutralize the inflammatory sugars themselves, or reinforce the gut lining to prevent leakage could all potentially be developed as therapies. Rodriguez-Palacios said his team hopes to begin designing a clinical trial within one year, pending additional preclinical validation in larger animal models.

ALS affects approximately 30,000 Americans at any given time and kills most patients within two to five years of diagnosis. FTD, the most common form of dementia in people under 65, is similarly devastating and has few treatment options. The Case Western research, funded in part by the National Institutes of Health and the ALS Association, adds to a growing body of evidence that the gut microbiome is a viable therapeutic target for diseases previously thought to be strictly neurological — and offers fresh hope to patients and families who have had few reasons for optimism.