P1967 - Body Mass Index and Diabetes Impact Small Intestinal Bacterial Overgrowth Caused by Hydrogen-Producing Bacteria, But Not Methane-Producing Archaea

Katelyn Madigan, MD, Richard B. Weinberg, MD
Wake Forest Baptist Health, Winston-Salem, NC

Introduction: The human gut microbiome is a complex ecosystem of around 100 trillion bacteria that resides in the lumen of the intestinal tract. In the healthy gut, the vast majority of these bacteria inhabit the colon. However, in small intestinal bacterial overgrowth (SIBO), the bacterial population of the small bowel lumen can increase many log-fold. The majority of patients with SIBO produce hydrogen (H₂); however, around 33% are colonized with methanogenic Archaea – anaerobic organisms that produce methane (CH₄) and are often resistant to standard antibiotics. Although the microbiome has been implicated in the etiologies of obesity and type 2 diabetes (DM), the impact of obesity and DM on SIBO is not well defined.

Methods: We queried a database of breath tests conducted for suspected SIBO at our tertiary medical center. All patients had undergone a standard testing protocol that involved administering a 50g oral glucose load; obtaining breath samples at 15-min intervals for 2 hours; and analyzing them for H₂ and CH₄ gas concentration. Gas production, a surrogate measure of bacterial colonization density, was determined by area under the time-concentration curves (AUC). The presence of SIBO was determined using established consensus criteria. Body mass index (BMI) and DM ICD-10 codes were obtained from medical records.

Results: In the cohort of 1126 patients, mean age was 54.8 ± 0.6 years; 840 (74.6%) were female; 390 (34.6%) were SIBO(+), of whom 245 (62.8%) produced H₂ and 145 (37.2%) produced only CH₄; and 283 patients (25.1%) had DM, of whom 260 (92%) had type 2 DM, and 23 (8%) had type 1 DM. The frequency of DM was significantly higher in patients who were H₂-SIBO(+) (79/245, 32.2%) vs. CH₄-SIBO(+) (38/145, 26.2%) or SIBO(-) (166/736, 22.6%) at p=0.010 by Chi². DM frequency progressively increased across BMI classes in each SIBO status group and trended higher in H₂-SIBO(+) patients in the 35-40 BMI range (Table 1). H₂ production (as AUC) in H₂-SIBO(+) patients displayed a U-shaped relationship across BMI classes, with the lowest values in the 30-35 BMI range (p=0.014 by ANOVA), whereas CH₄ production in CH₄-SIBO(+) patients was unaffected by BMI (Figure 1).

Discussion: These data reveal that BMI and DM have a significant impact on small intestine bacterial colonization caused by H₂-producing bacteria, but not by methane-producing Archaea. Future investigations into the cause-effect relationships of these findings could further elucidate the etiologic mechanisms of SIBO.


Figure: Mean gas production (as areas-under-the-curves of breath gas concentration in ppm versus time) for patients with hydrogen-producing SIBO (H2) and methanogenic SIBO (CH4) by BMI class. Values for H2-SIBO are significantly different from one another across BMI classes at p=0.014 by ANOVA.

Table:
Values in each row indicate the percent of subjects in the indicated BMI range. P-values indicate the significance of differences among SIBO phenotypes within each BMI range.


Disclosures:
Katelyn Madigan indicated no relevant financial relationships.
Richard Weinberg indicated no relevant financial relationships.


Katelyn Madigan, MD, Richard B. Weinberg, MD. P1967 - Body Mass Index and Diabetes Impact Small Intestinal Bacterial Overgrowth Caused by Hydrogen-Producing Bacteria, But Not Methane-Producing Archaea, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.