{"version":"v1","chain":{"id":"h2s-shared-driver-chain","title":"Excess H₂S → colonocyte energy stall → SIBO + MCAS amplification","question":"How could a single metabolite plausibly drive both SIBO-pattern and MCAS-pattern symptoms?","summary":"Hydrogen sulfide inhibits short-chain acyl-CoA dehydrogenase and complex IV in colonocytes, stalling β-oxidation and OXPHOS, plausibly producing the same downstream oxygen-leak cascade *and* sensitising mucosal mast cells via TRPA1.","steps":[{"nodeId":"molecule:hydrogen-sulfide","rationale":"Sulfate-reducing bacteria expand; faecal/colonic H₂S rises.","evidence":"established"},{"nodeId":"process:beta-oxidation","rationale":"H₂S inhibits SCAD and complex IV, stalling colonocyte β-oxidation.","evidence":"strong-mechanistic-inference","claimIds":["h2s-inhibits-colonocyte-beta-oxidation"]},{"nodeId":"concept:colonocyte-bioenergetics","rationale":"Epithelial ATP and oxygen consumption fall.","evidence":"mechanistic-inference"},{"nodeId":"concept:oxygen-gradient-failure","rationale":"Mucosal O₂ rises; facultative-anaerobe expansion follows.","evidence":"mechanistic-inference"},{"nodeId":"concept:mcas-histamine-patterns","rationale":"Sensory afferents and mucosal mast cells are sensitised in parallel via TRPA1.","evidence":"hypothesis","claimIds":["h2s-as-shared-driver-of-sibo-and-mcas"]}],"competingChains":["independent-cooccurrence-chain"],"relatedConcepts":["mcas-histamine-patterns","colonocyte-bioenergetics"],"relatedArticles":["the-single-molecule-driving-both-your-sibo-and-your-mcas-and"],"evidenceFloor":"hypothesis","lastReviewed":"2026-05-11"}}