Hypothesis

Enteroendocrine AMPK activation drives neuronal AMPK signaling via CGRP release and vagal afferents, establishing a gut‑to‑brain axis that initiates systemic longevity programs.

Mechanistic rationale

1. Intestinal AMPK activation (e.g., by AICAR or genetic upregulation) increases phosphorylation of AMPK in enteroendocrine cells, enhancing exocytosis of calcitonin gene‑related peptide (CGRP) [1].
2. CGRP released into the lamina propria binds to CGRP receptors on vagal afferent terminals, triggering action potentials that travel to the nucleus tractus solitarius (NTS) and then to the hypothalamus [2].
3. Vagal‑mediated CGRP signaling activates AMPK in hypothalamic neurons through a CaMKKβ‑dependent pathway, which concurrently inhibits mTORC1 and upregulates SIRT1‑FOXO transcriptional activity [3].
4. Neuronal AMPK activation orchestrates autonomic output that upregulates intestinal barrier function, modulates microbiota‑derived bile acid signaling (via TGR5), and promotes hepatic ketogenesis, creating a positive feedback loop that sustains systemic autophagy and mitochondrial biogenesis [4].

Testable predictions

• Prediction 1: Intestine‑specific AMPK knockout (using Villin‑Cre;AMPKα1/2 floxed mice) will abolish the increase in hypothalamic p‑AMPK and SIRT1 normally seen after systemic AICAR treatment, without affecting liver or muscle AMPK phosphorylation.
• Prediction 2: Pharmacological blockade of CGRP receptors (with olcegepant) or vagotomy will prevent the hypothalamic AMPK response to intestinal AMPK activation, yet peripheral AMPK activation in muscle will remain intact.
• Prediction 3: Oral administration of a gut‑restricted AMPK activator (e.g., colonic‑targeted metformin formulation) will extend lifespan in wild‑type mice, an effect that is lost in mice lacking enteroendocrine CGRP (Calca‑KO) or with severed vagal afferents.
• Prediction 4: Elevated plasma CGRP and increased hypothalamic p‑AMPK will correlate with improved autophagy markers (LC3‑II/I ratio, p62 degradation) in brain tissue, measurable by immunoblotting.

Falsifiability

If intestinal AMPK activation fails to raise hypothalamic p‑AMPK or SIRT1, or if blocking CGRP/vagal signaling does not diminish the neuronal response while peripheral AMPK targets remain unchanged, the hypothesis is refuted. Conversely, confirmation of the predicted cascade would support a bottom‑up gut‑brain axis as a primary driver of AMPK‑mediated longevity.

References

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6941559/ [2] https://www.science.org/doi/10.1126/sciadv.aaw7824 [3] https://doi.org/10.1101/2025.04.25.650677 [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC4287273/