Hypothesis\n\nPrecision modulation of the gut microbiome with butyrate‑producing strains reduces telomere informational entropy, thereby preserving hippocampal-dependent cognition in aging.\n\n## Mechanistic rationale\n\n- Butyrate as an epigenetic modulator: Sodium butyrate inhibits histone deacetylases (HDACs), increasing acetylation of histones H3 and H9 at subtelomeric chromatin. This relaxes nucleosome positioning, facilitating transcription of telomere repeat‑containing RNA (TERRA) and promoting homologous recombination‑based telomere maintenance (see [2]).\n- TERRA and telomere entropy: Elevated TERRA levels buffer the loss of telomeric repeats by forming RNA‑DNA hybrids that protect chromosome ends from exonucleolytic erosion, effectively lowering the Shannon entropy of telomere sequence information.\n- Microbiome‑cognition link: Specific strains such as Clostridium butyricum and Blautia spp. raise colonic butyrate concentrations, which cross the gut‑vascular barrier and reach the brain via the vagus nerve and systemic circulation, enhancing BDNF expression and synaptic plasticity ([1]).\n- Pathogen counteraction: Parabacteroides goldsteinii accumulates with age and produces metabolites that inhibit HDAC activity, opposing butyrat‑mediated chromatin opening and increasing telomere entropy ([3]).\n\n## Testable predictions\n\n1. Intervention arm: Older adults receiving a daily dose of 5×10^10 CFU B. longum BB68S combined with a defined butyrate‑producing consortium (e.g., C. butyricum + Blautia sp.) for 12 weeks will show:\n - ↑ fecal butyrate (measured by GC‑MS).\n - ↑ peripheral blood TERRA levels (RT‑qPCR).\n - ↓ telomere entropy calculated from telomere‑seq Shannon diversity.\n - Improved RBANS scores vs. placebo.\n2. Depletion arm: Participants given a targeted phage or narrow‑spectrum antibiotic reducing P. goldsteinii abundance will exhibit the inverse changes (↓ butyrate, ↑ telomere entropy, worsened cognition) unless rescued by the butyrate‑producing probiotic.\n3. Causality test: In germ‑free mice colonized with either the butyrate‑producing consortium or P. goldsteinii, telomere entropy in hippocampal neurons will be assessed via single‑cell telomere sequencing; cognitive performance in the Morris water maze will correlate inversely with entropy measures.\n\n## Falsifiability\n\nIf the butyrate‑producing probiotic fails to raise fecal butyrate, TERRA, or lower telomere entropy, or if cognitive improvements occur without these molecular changes, the hypothesis is refuted. Conversely, if P. goldsteinii depletion does not increase telomere entropy or worsen cognition, the pathogen‑entropy link is unsupported.\n\n## Broader implication\n\nFraming telomeres as an information‑theoretic clock positions microbiome‑derived metabolites as tunable parameters that can reset or stabilize biological computation, offering a mechanistic bridge between precision psychobiotics and the thermodynamic constraints of aging.\n\n### References\n- [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC10912297/\n- [2] https://academic.oup.com/biomedgerontology/article/78/12/2187/7280345\n- [3] https://med.stanford.edu/news/all-news/2026/03/gut-brain-cognitive-decline.html\n- [4] https://spj.science.org/doi/10.34133/research.0658