Wongkrasant, Preedajit

The intestinal epithelium is exposed to diverse combinations of microbiota-derived compounds; however, the mechanisms by which the host integrates these signals remain poorly defined. Studying two highly abundant microbial metabolites, we identified the purine metabolite hypoxanthine as an effector metabolite that directly drives signaling and the short-chain fatty acid butyrate as a regulatory metabolite that conditions host responsiveness. Specifically, hypoxanthine activates the adenosine A1 receptor–TRPC4 axis in enterochromaffin (EC) cells, triggering calcium influx and serotonin release resulting in accelerated gastrointestinal transit locally and increased platelet activation systemically. In contrast, butyrate epigenetically upregulates specific G protein–coupled receptors and ion channels to enhance response to hypoxanthine and the neurotransmitters norepinephrine and dopamine. These findings define a cooperative signaling framework and highlight the role of EC cells as a distinct epithelial signaling hub that senses and integrates microbial metabolite signals to drive physiological responses. Our findings provide a mechanistic foundation for therapeutic strategies that leverage combinatorial microbial signaling.

Background: As part of the bidirectional gut-brain communication system that influences gastrointestinal function, vagal pathways coordinate with the activity of interstitial cells of Cajal (ICC) to regulate gastric motility. Impairments in ICC slow wave activity and altered vagal tone have been implicated in diabetic gastroparesis and obesity, but technical limitations have restricted our ability to measure integrated and bidirectional activity in vagal-ICC pathways. Furthermore, the influence of physiological and meal-induced stimuli like gastric distension on these pathways is not well understood. We aimed to develop a calcium imaging approach in ex vivo nodose ganglion-vagus nerve-stomach preparations to investigate vagal-ICC pathways and test the effects of gastric distension on vagal activation, ICC network activity, and their functional interactions. Methods: Calcium imaging was performed in ex vivo preparations, in which the stomach and vagus nerves (with or without the ganglion) remain intact. EIIa-GCaMP6 (n=3) and cKit-GCaMP6 (n=3) mice were used to image Ca 2 + signals from both vagal neurons and ICC or ICC alone, respectively. Two-minute recordings were captured in the following stomach conditions: (1) Undistended; (2) Undistended + vagal nerve stimulation (VNS, 20 Hz, 1 s); (3) Distended (0.25 ml volume distension); (4) Distended + VNS. Ca 2 + signals in ICC and neurons, along with tissue displacement, were analyzed using Image J. Data from both GCaMP models were pooled for ICC. Results: Acute gastric distension significantly activated vagal sensory neurons in nodose ganglion compared to baseline (p=0.0193), and VNS evoked Ca 2 + responses in ICC and neurons, confirming intact nerve pathways. Both VNS and gastric distension altered the direction of ICC propagation, significantly increasing retrograde waves (p=0.0025 and p=0.0032, respectively), and VNS had no effect on retrograde waves in distended stomachs. VNS and distension also reduced length of propagation of anterograde ICC waves (p=0.019 and p=0.0004, respectively), and again, VNS effects were not observed during distension. VNS increased the velocity of ICC wave propagation, but only in undistended stomach (p=0.0283). Finally, VNS increased ICC pacemaker frequency regardless of the distension state (p=0.0123). Conclusion: Both acute gastric distension and VNS altered ICC network activity, with similar effects on network parameters. However, most of the VNS effects on ICC were blocked during distension. VNS increased the frequency of ICC network waves in both undistended and distended stomachs, suggesting that VNS can influence ICC pacemakers regardless of distension state. These findings have important implications for designing therapeutic strategies for gastroparesis. 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.