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Small Bowel Microbiome Changes in Individuals With Overweight or Obesity
abstract
This abstract is available on the publisher's site.
Access this abstract nowOBJECTIVES
Gut microbiome changes are linked to obesity, but findings are based on stool data. Here, we analyzed the duodenal microbiome and serum biomarkers in subjects with normal weight, overweight, and obesity.
METHODS
Duodenal aspirates and serum samples were obtained from subjects undergoing standard-of-care esophagogastroduodenoscopy without colon preparation. Aspirate DNAs were analyzed by 16S rRNA and shotgun sequencing. Predicted microbial metabolic functions and serum levels of metabolic and inflammatory biomarkers were also assessed.
RESULTS
Subjects with normal weight (N=105), overweight (N=67) and obesity (N=42) were identified. Overweight-specific duodenal microbial features include lower relative abundance (RA) of Bifidobacterium species and Escherichia coli strain K-12, and higher Lactobacillus intestinalis, L. johnsoni, and Prevotella loeschii RA. Obesity-specific features include higher Lactobacillus gasseri RA and lower L. reuteri (subspecies rodentium), Alloprevotella rava and Leptotrichia spp RA. Escalation features (progressive changes from normal weight through obesity) include decreasing Bacteroides pyogenes, Staphylococcus hominis, and unknown Faecalibacterium species RA, increasing RA of unknown Lactobacillus and Mycobacterium species, and decreasing microbial potential for biogenic amines metabolism. De-escalation features (direction of change altered in normal-to-overweight and overweight-to-obesity) include Lactobacillus acidophilus, L. hominis, L. iners, and Bifidobacterium dentium. An unknown Lactobacillus species is associated with Type IIa dyslipidemia and overweight, whereas Alloprevotella rava is associated with Type IIb and IV dyslipidemias.
CONCLUSIONS
Direct analysis of the duodenal microbiome has identified key genera associated with overweight and obesity, including some previously identified in stool, e.g. Bifidobacterium and Lactobacillus. Specific species and strains exhibit differing associations with overweight and obesity, including escalation and de-escalation features that may represent targets for future study and therapeutics.
Additional Info
Disclosure statements are available on the authors' profiles:
Characterization of the Small Bowel Microbiome Reveals Different Profiles in Human Subjects who are Overweight or have Obesity
Am. J. Gastroenterol 2024 Apr 08;[EPub Ahead of Print], G Leite, GM Barlow, M Rashid, A Hosseini, D Cohrs, G Parodi, W Morales, S Weitsman, A Rezaie, M Pimentel, R MathurFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
The small bowel microbiome has only recently gained attention in the past 10 years related to its potential importance in regulating host physiological processes and metabolic health. Evidence has been lacking from human subjects to characterize differences in small bowel microbial ecology between individuals with normal weight versus those with obesity. One major limitation in this field is the accessibility of small bowel samples from human participants, particularly from generally healthy individuals undergoing upper endoscopy.
Leite et al surveyed an impressive number of subjects for small bowel microbiome assessment including 214 total subjects following exclusion. This study provided strong evidence that the small bowel microbiome greatly differs among individuals with normal weight (n = 105), overweight (n = 67), and obesity (n = 42). Notably, the sample population reflects current prevalence rates of overweight and obesity in the US. Small intestinal lumen contents were collected via esophagogastroduodenoscopy and 16S rRNA and shotgun metagenomic sequencing were performed. Plasma inflammatory markers and plasma lipids were measured to establish correlations to alterations in the microbiome. Changes in the small bowel microbiome composition and functional potential were categorized based on differences among normal weight, overweight, and obesity status and as escalation (associated with a change in relative abundance from normal weight to overweight and obesity) or de-escalation features (associated with a change in overweight vs normal weight but not between normal weight and obesity). Relative abundance changes for many species found using 16S rRNA sequencing were confirmed using shotgun metagenomic sequencing; the latter performed on a subset of individuals from each group. Certain microbes, including several species of Bifidobacterium including Bifidobacterium dentium, were found to be decreased in individuals with obesity, which is consistent with the literature. Alternatively, other microbes, such as Lactobacillus gasseri, were found to be associated with obesity. L acidophilus and L hominis were classified as de-escalation features. No changes were identified based on plasma inflammatory markers except an association between TNF-α and obesity. Related to dyslipidemia assessment, type IIa dyslipidemia was associated with several Lactobacillus species, and type IIb and IV dyslipidemia were associated with Alloprevotella rava.
These findings draw attention to the need to further characterize the small bowel microbiome in human populations and, more importantly, begin to understand how small bowel–specific microbes, such as those identified here, interact with the host to alter physiological and important host processes, such as nutrient absorption and enteroendocrine production, that occur in the small intestine.