Altered Gut Microbiota in ALS Patients Could Drive Digestive Problems, Study Suggests

People with amyotrophic lateral sclerosis (ALS) have an altered composition of their gut microbial community, with an increase in harmful microbes and a decrease in beneficial microorganisms, according to a new small study.

This altered gut microbiota could drive digestive problems in those with ALS, the researchers said.

The study, “Intestinal microbiota composition in patients with amyotrophic lateral sclerosis,” appeared in the Chinese Medical Journal.

Crosstalk between the brain and the gut has been increasingly shown in neurological diseases, including Parkinson’s and multiple sclerosis.

People with ALS experience weight loss, along with digestion disturbances and intestinal barrier dysfunction, or impairment of the natural boundary layer in the gut. Research has indicated that these patients have increased amounts of harmful bacteria and lower levels of beneficial microbes in the gastrointestinal tract, which leads to impaired metabolism. However, a thorough evaluation of the interaction between the microbial community and metabolites in the gut of people with ALS remains to be done.

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To address this gap, a team from Fudan University and Guangzhou Dongsheng Hospital, in China, examined fecal samples of people with ALS. The scientists determined the composition of bacteria and archaea — single-cell microorganisms, with similar structure to bacteria. They also assessed the concentration of bacteria-derived endotoxin, short-chain fatty acids (SCFA), nitrite-nitrogen (NO₂-N)/nitrate-nitrogen (NO₃-N) — constituents of the nitrogen cycle — and GABA, produced by gut microbes and implicated in motility and inflammation.

Eight patients and eight healthy people (controls) were recruited from November 2017 to April 2018. The participants had not used antibiotics in the month prior to the study.

Using genetic analysis, the scientists found that the ALS patients had a different bacterial and archaeal composition than the controls.

Specifically, those with ALS had a higher relative abundance of the phylum Firmicutes — a category between class and kingdom — but a lower abundance of Bacteroidetes. Importantly, a higher Firmicutes/Bacteroidetes ratio has been proposed as an indicator of poor gastrointestinal health, the team said.

The classes Negativicutes and Bacilli also were less abundant in ALS patients than in the controls. As for the archaeal community, the phylum Euryarchaeota, the class Methanobacteria, and the genus — above species and below family — Methanobrevibacter (which uses short-chain fatty acids, and has been associated with weight loss) were more abundant in patients than in controls.

No statistically significant differences were seen in the average concentrations of the metabolites — all “considered as the important elements for nutrient consumption in daily diet.” However, the people with ALS showed a trend toward higher levels of SCFA, NO₂-N/NO₃-N, and GABA, “indicating that the digestion and metabolism functions of gastrointestinal tract of patients might decline,” the researchers said.

“In summary, the biodiversity and composition of intestinal microflora in patients with ALS were generally on the decline compared with healthy individuals,” they added.

The scientists also highlighted that, in those with ALS, beneficial micro-organisms were less abundant, while those harmful to the gut were more abundant.