Reserpine-FM microbiome metabolites — FM-direct mechanism with acetate intervention

One-paragraph summary

Primary mechanism paper using the reserpine-induced rodent FM model. Acetate-producing diet (acetylated high-amylose maize starch) shifts gut microbiome toward acetate-producing bacteria, elevates systemic acetate, and reduces FM-like pain hypersensitivity. Mechanism dissection: reduced spinal microglial activation, elevated IL-10 mRNA in DRG, elevated IL-10/IL-2/IL-6 mRNA in spinal cord, reduced dorsal-horn hyperexcitability, increased inhibitory activity. Causal mechanism identified: reduced PGE2-mediated suppression of glycinergic inhibition as the direct consequence of maintaining microglia in quiescent state. This is FM-direct gut-brain mechanism work with a dietary intervention chain, not a generic gut-brain review — the B2 cooldown is appropriately overridden because within-FM mechanism papers are the cooldown exception. Closes a key piece of B2 bridge with within-FM evidence.

Claims as triples

• acetate_producing_diet — shifts → gut_microbiome_composition_toward_acetate_producers [evidence: primary 16S; confidence: established]
• systemic_acetate — elevated_by → acetate_producing_diet [evidence: primary measurement; confidence: established]
• reserpine_induced_fm_pain_hypersensitivity — reduced_by → acetate_producing_diet [evidence: primary behavioral; confidence: emerging — single rodent model]
• spinal_microglial_activation — reduced_by → systemic_acetate [evidence: primary IHC/molecular; confidence: emerging]
• IL_10 — elevated_in_DRG_by → systemic_acetate [evidence: primary qPCR; confidence: emerging]
• dorsal_horn_hyperexcitability — reduced_by → systemic_acetate [evidence: primary electrophysiology; confidence: emerging]
• glycinergic_inhibition — restored_by → microglial_quiescence [evidence: primary mechanism dissection; confidence: emerging]
• PGE2 — suppresses → glycinergic_inhibition [evidence: primary; confidence: established (replicates known PGE2-mediated disinhibition pathway)]

Methods note

Reserpine-induced rodent FM model (standard FM model with monoamine depletion driving widespread hyperalgesia). Dietary intervention: acetylated high-amylose maize starch vs control diet. Outcome measures: behavioral pain (mechanical/cold allodynia), 16S rRNA gut microbiome sequencing, serum/SCFA measurements, spinal cord and DRG IHC for microglial activation, qPCR for cytokines (IL-10, IL-2, IL-6), dorsal-horn electrophysiology, PGE2/glycinergic inhibition mechanism testing. Comprehensive mechanism-to-behavior chain.

Limitations

• Rodent model only; the reserpine model is widely used for FM but is not a perfect substrate model (no IgG autoantibody features, no MC degranulation features)
• Single intervention type (dietary); no comparison with isolated acetate supplementation, or with non-acetate SCFA (butyrate, propionate)
• Dietary effects could include non-acetate mechanisms (fiber, prebiotic effects on other taxa)
• Cohort size not specified in abstract
• Reserpine model captures central-sensitization aspect of FM but not the autoimmune-subtype aspect (FM-IgG / anti-SGC IgG)

Open questions raised

• Q-FM-microbiome-1 (new): Does acetate supplementation alone (without dietary shift) replicate the effect? Tests whether acetate is the necessary-and-sufficient mediator vs whether the microbiome shift itself matters.
• Q-FM-microbiome-2 (new): Does the acetate-PGE2-glycinergic-inhibition mechanism operate in FM patients? PGE2 measurement in FM CSF/serum is available; glycinergic-inhibition measurement is harder but accessible via spinal reflex paradigms.
• Q-FM-microbiome-3 (new): Are there FM patients whose microbiome is acetate-depleted vs acetate-replete? If so, acetate replenishment becomes an N-of-1 stratifiable intervention.

Triangulation notes

• Closes within-FM evidence gap for B2 (gut-brain axis): the project's B2 framework was strongly built on AD, MS, and depression literature with B2-cooldown applied because of duplicate gut-brain-review yield. This paper is the FM-direct mechanism work the cooldown was specifically not blocking. Should be cited as the within-FM closing anchor for B2.
• Compatible with Tian 2026 + Tatai 2026 (FMT in AD model + tissue-AAb LC methodology): Tian's AD-FMT shows TREM2/SYK/NF-κB axis; this paper shows acetate→microglial quiescence→glycinergic restoration in FM. Both implicate microglial polarization but at different molecular endpoints. Possible reconciliation: TREM2/SYK is the M1-polarization arm (AD), acetate/SCFA is the M1→M2 polarization arm (FM), with PGE2/glycinergic-inhibition the FM-specific dorsal-horn endpoint.
• Reinforces dietary intervention as candidate cure-path arm: Mediterranean diet + acetate-producing diet + prebiotic supplementation should be evaluated jointly. Already partially captured in synthesis but FM-direct mechanism justification is now strengthened.

Bridges

• B2 status update: bridge has its within-FM mechanism anchor. The bridge can be promoted from "bridging" → "emerging-closing" with this evidence. Update synthesis/bridges.md.
• No new bridges.

Cure-path-arm implications

• Acetate-rich diet / acetate supplementation as candidate cure-path arm. Currently absent from cure-path-arm-decisions document. Should be added at watchlist tier pending FM-direct trial evidence.
• PGE2-pathway interventions (COX-2 inhibitors, etc.) as candidates — but FM trials of NSAIDs have been historically negative, suggesting PGE2 pathway is downstream and not the rate-limiting step in unselected FM. Reserpine-model mechanism may not generalize at the systemic-NSAID level.

Confidence-tier framing

• Reserpine-model acetate effect: established (within the rodent model context)
• Mechanism dissection (microglial quiescence → glycinergic restoration): emerging (well-supported but single study, single model)
• FM-patient extrapolation: inferred (mechanism is reasonable, awaits FM-direct measurement)