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TOPLINE:

The microbial makeup of the small bowel is significantly and specifically altered in adults with overweight or obesity, which may represent therapeutic targets for future development, new research suggested.

METHODOLOGY:

• Imbalances in microbial populations have previously been observed in stool samples of patients with obesity-related diseases. This is the first study to fully examine the small bowel microbiome in different weight categories.
• Duodenal aspirates and serum samples were obtained from 214 adults (105 with normal weight, 67 with overweight, and 42 with obesity) undergoing routine esophagogastroduodenoscopy without colon preparation.
• Microbial analysis included both 16S ribosomal RNA and shotgun sequencing. Inflammatory and metabolic biomarkers were assessed in blood samples.

TAKEAWAY:

• Overweight-specific duodenal microbial features include a lower relative abundance of Bifidobacterium species and Escherichia coli strain K-12 and a higher abundance of Lactobacillus intestinalis, Lactobacillus johnsonii, and Prevotella loescheii.
• Obesity-specific features include higher Lactobacillus gasseri and lower Limosilactobacillus reuteri, Alloprevotella rava, and Leptotrichia spp. relative abundance.
• "Escalation" features (progressive changes from normal weight through obesity) include decreasing relative abundance of Bacteroides pyogenes, Staphylococcus hominis, and unknown Faecalibacterium species; increasing abundance of unknown Lactobacillus and Mycobacterium species; and decreasing microbial potential for biogenic amine metabolism.
• "De-escalation" features (direction of change altered in normal weight to overweight and overweight to obesity) include changes in Lactobacillus acidophilus, Lactobacillus hominis, and Lactobacillus iners, as well as Bifidobacterium dentium — consistent with its known anti-obesity effects.
• Specific Lactobacillus species are linked to type IIa dyslipidemia and overweight, and A rava is linked to type IIb and IV dyslipidemias.

IN PRACTICE:

"We identify small bowel microbial species associated with overweight and obesity, as well as escalation and de-escalation features that could potentially be selected as therapeutic targets. These findings illustrate that, although stool studies can and have provided very valuable data, direct analysis of the small bowel has yielded specific targets for further study," the authors wrote.

SOURCE:

The study, with first author Gabriela Leite, PhD, with the Medically Associated Science and Technology program, Cedars-Sinai, Los Angeles, was published online in the American Journal of Gastroenterology.

LIMITATIONS:

The population was heterogeneous, with different indications for upper endoscopy, and the diet was not standardized. Samples were obtained at a single timepoint, and cause-and-effect relationships cannot be established.

DISCLOSURES:

This research was partially funded by the Monica Lester Charitable Trust and the Elias Genevieve and Georgianna Atol Charitable Trust. The authors have declared no conflicts of interest related to this study.