Less diverse gut microbiome seen in patients with digestive problems
Probiotic therapy may need to be more personalized for autoimmune disorders
People with systemic sclerosis (SSc) who have more severe digestive problems tend to have less diversity in the makeup of bacteria living in their gut, a new study reports.
Certain bacterial species, including Lactobacillus — present in commercially available probiotics — are more abundant in SSc patients with more digestive complaints, results show, which suggests that probiotic therapy may need to be more personalized for people with autoimmune disorders like SSc.
The study, “Gastrointestinal tract involvement in systemic sclerosis: The roles of diet and the microbiome,” was published in the journal Seminars in Arthritis and Rheumatism.
Research suggests gut microbiome is dysregulated in SSc patients
The human gut is home to trillions of bacteria and other microorganisms, collectively known as the gut microbiome. A blossoming field of research has suggested that the gut microbiome is dysregulated in SSc and many other diseases, but the connection between microbiome changes and specific disease manifestations remains poorly understood.
Digestive problems, ranging from heartburn to diarrhea and constipation, are common symptoms of SSc, also called scleroderma. In this study, a team led by scientists in the U.S. set out to test whether gut microbiome changes are associated with digestive symptoms in people diagnosed with SSc.
“The primary aim of the present study was to examine the relationship between GI [gastrointestinal] microbial composition and the severity of GI symptoms in SSc,” the researchers wrote.
The study included 66 people with SSc; most were women and the mean age was 55.4 years. All of the participants completed a standardized assessment of digestive symptom severity in SSc called the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract, or UCLA GIT 2.0. The seven domains of this scale are reflux, distension, diarrhea, fecal soilage, constipation, well-being, and social functioning.
Participants also provided samples of their stools, which the researchers used to conduct analyses of the gut microbiome. To identify bacteria types, the scientists took advantage of a technique called 16S rRNA gene sequencing.
Understanding the relationships between alterations in GI microbial composition and SSc may help identify new therapeutic targets and guide clinical and nutritional management.
More severe digestive symptoms linked to less diverse microbiomes
Results showed that SSc patients with higher (worse) GIT 2.0 scores tended to have less diverse microbiomes, with fewer different types of bacteria living in the microbial community. Higher (worse) scores for distension/bloating and social functioning showed especially strong associations with lower microbiome diversity.
Closer analyses showed that patients with more severe digestive symptoms tended to have a higher abundance of certain groups of bacteria, such as Klebsiella and Enterococcus, that are often associated with disease in people. These patients also had a lower abundance of bacteria like Clostridium and Coprococcus that are generally thought to be a healthy part of the digestive tract.
The researchers also noted that patients with more severe GI symptoms tended to have higher levels of Lactobacillus, a group of bacteria often included in commercially available probiotic supplements. “These study findings suggest that a more personalized probiotic may be beneficial depending on the underlying autoimmune disease,” the team wrote.
Dietary questionnaires were completed by 35 of the participants. Based on their reported dietary habits, they were divided into a low FODMAP or non-low FODMAP group.
FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. The low FODMAP diet, which excludes many foods containing certain sugar molecules, has been used to help manage irritable bowel syndrome.
No significant differences found between patients on the two diets
Results of the analysis generally did not show any significant differences in digestive symptom severity or gut microbiome diversity between the low and non-low FODMAP patients. However, those in the non-low FODMAP group tended to have higher levels of the disease-related bacteria Klebsiella and Enterococcus.
“Although this study did not find differences in GI symptoms between the low and non-low FODMAP groups, there were several differences in the enrichment of bacteria between groups,” the researchers wrote.
The team stressed that this was a small study that relied on patient-reported assessments of dietary habits, so more research will be needed to better understand the effect of diet on digestive symptoms and gut bacteria in SSc.
“Understanding the relationships between alterations in GI microbial composition and SSc may help identify new therapeutic targets and guide clinical and nutritional management,” the scientists concluded. “Larger, prospective studies are warranted to determine whether dietary changes and treatments targeting gut microbial alterations may reduce GI symptoms in SSc.”