P0389 - Presence of Methane in the Fasting Breath Is Associated With a Lower Rise in Pancreatic Polypeptide After Modified Sham-Feeding: An Insight into the Connection Between Vagal Dysfunction and Methane

Will Takakura, MD¹, Mark Pimentel, MD², Ruchi Mathur, MD¹, Ali Rezaie, MD^3
1Cedars-Sinai Medical Center - MAST Program, Los Angeles, CA; ²Cedars-Sinai Medical Center, West Hollywood, CA; ³Cedars Sinai Medical Center - MAST Program, West Hollywood, CA

Introduction: The vagus nerve as a key part of the parasympathetic system regulates gut motility and is implicated in numerous diseases. Pancreatic Polypeptide modified sham-feeding test (PP MSF) is an indirect method to measure vagal tone by measuring serum pancreatic polypeptide levels after chewing but not swallowing food (Balaji et al. JAMA surgery 2002). Excess intestinal methane (CH₄) is associated with constipation and is thought to act as a gasotransmitter via the cholinergic pathway. We aimed to evaluate the association between fasting exhaled CH₄ and vagal dysfunction as measured by the PP MSF.

Methods: Utilizing a natural-language processor, patients with a lactulose breath test (LBT) and PP MSF were identified from Jan 2010 to Oct 2020. Patient demographics, medical history known to affect vagal dysfunction, and a history of esophagectomy or fundoplication were collected. For LBT, patients were asked to eat a low-fermentable diet and fasted for 12 hours prior to the test. Baseline (fasting) CH₄ measurements corrected to breath CO₂ levels were collected for this study. For the PP MSF, patients fasted for 12 hours then were asked to chew and spit out a hamburger without swallowing. Serum PP levels were measured before and after MSF in 5-minute intervals for 30 minutes. Percent rise in PP from baseline were calculated and compared between patients that had detectable (CH₄ > 0 ppm) vs undetectable (CH₄ = 0 ppm) CH₄ on their baseline LBT.

Results: Forty-three patients (27.9% males, median age = 51 ± 17.8 years) were included in the cohort. Eighteen patients (41.8%) had detectable fasting CH₄ (median CH₄ = 3.0 ± 12.4 ppm). There was no difference in baseline characteristics or prespecified risk factors affecting vagal dysfunction between those who had detectable and undetectable CH₄ (table 1). Patients with CH₄ had a significantly lower rise in PP after MSF (4.9% ± 49.0 vs 42.2% ± 96.1, p = 0.01) (Figure 1). Subgroup analysis for patients without esophagectomy or fundoplication showed that detectable CH₄ is associated with numerically lower rise in PP (13.4% ± 38.0 vs 39.6% ± 49.9, p = 0.07).

Discussion: This is the first study to show that a detectable CH₄ in the breath is associated with a lower rise in PP MSF. We hypothesize that CH₄ may be altering vagal tone by affecting the cholinergic pathway. Mechanistic animal models and prospective human studies without esophagectomy or fundoplication are needed to confirm these findings.




Disclosures:


Will Takakura, MD¹, Mark Pimentel, MD², Ruchi Mathur, MD¹, Ali Rezaie, MD³. P0389 - Presence of Methane in the Fasting Breath Is Associated With a Lower Rise in Pancreatic Polypeptide After Modified Sham-Feeding: An Insight into the Connection Between Vagal Dysfunction and Methane, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.