Background: Exogenous and endogenous polyamines are critical for gastrointestinal (GI) barrier integrity, of which putrescine, spermidine and spermine are most well studied. Our recent work shows n-acetylputrescine, a putrescine derivative, correlates with increased intestinal permeability and loss of microbial diversity. Despite this, bacterial mechanisms of n-acetylputrescine production or direct effects on barrier integrity are unknown. Aim: Determine the role of microbiota in shaping n-acetylputrescine abundance and the effect on barrier integrity. Methods: N-acetylputrescine effects on barrier were assessed both in vitro using Caco-2 and ex vivo in Ussing using colonic strips from conventional mice. Germ-free (GF) mice were monocolonized with wild-type E. coli (SK929) or E.coli SK930 (2-weeks, n=4mice/group), strains given by Dr. Shin Kurihara. E. coli SK930 is deficient in SpeC, SpeF and SpeB, genes generating putrescine, required for n-acetylputrescine production. Untargeted metabolomics (Metabolon) was performed on fecal pellets. Targeted isotope tracing with 13C6, 15N4-arginine delivered via enema was done to track bacterial production of n-acetylputrescine by Fusobacterium varium, a known producer, in vivo with isotopolog labeling measured by LC/HRMS. Results: In vitro n-acetylputrescine (100mM) addition to Caco-2 monolayers caused significant barrier disruption compared to controls (%Baseline TER, 13.7±6.7 vs 102.8±9.4, 3h postexposure, n=3 p=0.0002), not seen at lower (10mM) concentration. N-acetylputrescine caused increased flux of 300Da fluorescein (12.6±2.0 vs 6.0±0.2 mg/mL, n=3 p=0.004) and 4kDa FITC-Dextran flux on Ussing compared to untreated controls (999±94 vs 562±121 ng/hr/cm2, n=3 p= 0.01). Mutant E. coli SK930 monocolonized mice had similar fecal n-acetylputrescine to GF animals. In contrast, wild type E. coli SK929 monocolonization led to significantly greater n-acetylputrescine (5-fold, FDR< 0.001) compared to SK930, indicating a bulk of n-acetylputrescine production is driven by bacterial mechanisms. Pathway enrichment analysis predicted decreased spermidine and spermine biosynthesis in SK930 monocolonization, indicative of impaired polyamine metabolism, compared to SK929 (FDR< 0.01). Targeted metabolomics on fecal pellets showed a shift in the production of isotopolog 13C1, 15N0-N-acetylputrescine to increased isotopolog 13C4, 15N2-N-acetylputrescine concentration after monocolonization with F. varium compared to GF mice (5.9±5.0 vs. 2.1±3.6 pg/mg stool, n=3mice/group p=0.05) suggesting microbiota driven shifts in n-acetylputrescine metabolism. Conclusion: Luminal n-acetylputrescine production and profile is driven by bacteria in the GI tract. Concentration dependent effects of n-acetylputrescine suggest insufficient regulation by intestinal microbiota can lead to accumulation of n-acetylputrescine and the intestinal barrier disruption seen in human studies. Ongoing studies aim to identify bacterial taxa critical for n-acetylputrescine suppression, the mechanisms involved, and impact on GI health. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Edwinson et al. (Fri,) studied this question.