Butyrate

Butyrate is a four-carbon short-chain fatty acid (SCFA) produced in the colon when anaerobic bacteria — principally Faecalibacterium prausnitzii and Roseburia intestinalis (Firmicutes) — ferment dietary fibre via the butyryl-CoA:acetate CoA-transferase route and butyrate kinase. Luminal butyrate enters colonocytes via monocarboxylate transporters (MCT1/4) and undergoes mitochondrial β-oxidation, supplying roughly 70–80% of colonocyte ATP — the dominant epithelial energy source. Beyond fuel, butyrate inhibits class I/II histone deacetylases (HDACs), raising histone acetylation at promoters of tight-junction genes (claudin-1, occludin) and anti-inflammatory mediators, reinforcing the mucosal barrier and dampening NF-κB-driven cytokines (IL-6, TNF-α, IL-1β). Chang et al. (2014, PNAS) demonstrated in cell and murine models that butyrate blocks intestinal macrophage HDAC activity, markedly reducing LPS-induced pro-inflammatory mediators. In aging, gut dysbiosis depletes butyrate-producing taxa, lowering luminal butyrate and fuelling inflammaging. Rees et al. (2025, Aging Cell) classified butyrate as a senomorphic: in aged human T cells in vitro it suppressed SASP markers and attenuated IL-6 and IL-8 secretion. Trials in inflammatory bowel disease indicate tolerability and modest mucosal benefit; randomised evidence for longevity endpoints in healthy adults is absent as of 2026. Butyrate is best characterised as a plausible mechanistic link between dietary fibre, microbiome composition, and healthspan — not a proven anti-aging therapy.