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Guanylin

✓ Endogenous; analog (linaclotide) FDA approved
Guanylin (GC-C Receptor Agonist)
Also known as: GUC2C agonist (guanylin), Natriuretic gut peptide, Uroguanylin precursor analog
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Quick Summary

Guanylin is a 15-amino acid peptide, the first endogenous intestinal GC-C receptor agonist identified, acting as the physiological counterpart of bacterial heat-stable enterotoxin STa in regulating intestinal fluid and electrolyte balance. Produced predominantly by goblet cells and colonocytes, guanylin activates GC-C receptors in a luminal, paracrine manner (primarily colon) to increase cGMP, activate CFTR chloride channels, and promote secretion of.

GI Hormone / Secretory Research / Endogenous Hormone
Guanylin is a 15-amino acid peptide, the first endogenous intestinal GC-C receptor agonist identified, acting as the physiological counterpart of bacterial heat-stable enterotoxin STa in regulating intestinal fluid and electrolyte balance. Produced predominantly by goblet cells and colonocytes, guanylin activates GC-C receptors in a luminal, paracrine manner (primarily colon) to increase cGMP, activate CFTR chloride channels, and promote secretion of water, bicarbonate, and chloride into the gut lumen. Guanylin works in concert with uroguanylin (more proximal, more hormonally active) to regulate intestinal fluid homeostasis. The pharmaceutical validation of this pathway comes from linaclotide (a guanylin analog) and plecanatide (a uroguanylin analog) -- both FDA-approved GC-C agonists for constipation and IBS-C.
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Storage Stability
Lyophilized
1–2 years (-20°C)
Reconstituted
~30 days (2–8°C)
Room temp
Avoid

Mechanism of Action

Colonic GC-C Activation

Unlike uroguanylin (more proximal small intestine, endocrine effects), guanylin primarily acts in the colon in a paracrine/luminal manner. GC-C receptor activation by guanylin raises cGMP, which activates protein kinase G (PKG) to phosphorylate CFTR, opening chloride channels and triggering secondary water secretion (secretory laxative effect). cGMP also activates NHE2/3 inhibition, reducing sodium-coupled water absorption.

Visceral Analgesia via cGMP

Elevated intracellular cGMP diffuses from epithelial cells to subepithelial sensory neurons (via gap junctions or extracellular cGMP), inhibiting nociceptive signaling by activating PKG in dorsal root ganglion neurons. This visceral analgesic mechanism, independent of motility effects, explains why GC-C agonists reduce IBS abdominal pain as well as constipation symptoms.

Research Summary

IBS-C and Constipation (via Linaclotide)

Clinical Validation (Analog)

Linaclotide (a 14-aa guanylin analog) FDA-approved 2012 for IBS-C and CIC. Phase 3 trials: significant improvement in abdominal pain scores (primary IBS-C endpoint) and complete spontaneous bowel movements vs placebo. Minimally absorbed from gut lumen, limiting systemic exposure. Confirms GC-C agonism as a validated therapeutic mechanism for functional bowel disorders.

Colorectal Cancer Prevention

Active Research

GC-C signaling suppresses intestinal epithelial proliferation and promotes differentiation and apoptosis. Guanylin expression is markedly reduced in colorectal adenomas and cancers (epigenetic silencing). Restoration of GC-C signaling via oral GC-C agonists may suppress adenoma formation -- Phase 2 chemoprevention trials have been conducted.

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Research Protocols

GoalDoseFrequencyRoute
Intestinal secretion research10-100 nM luminal perfusion in intestinal loop modelsPer experimentLuminal
Cancer prevention researchOral linaclotide analog in rodent adenoma models (1-10 mg/kg/day)DailyOral

Guanylin is a luminal paracrine hormone; systemic injection poorly replicates physiological action. Research using linaclotide or uroguanylin captures most pharmacological territory.

Interactions

Complementary
Uroguanylin
Guanylin (colon-predominant) and uroguanylin (small intestine, systemic) provide complementary GC-C activation throughout the gut
Synergistic
cGMP-PDE inhibitors
Phosphodiesterase inhibitors that degrade cGMP (PDE5 inhibitors) would prolong GC-C-mediated cGMP signals

Safety Profile

Minimal systemic absorption limits adverse effects to GI: diarrhea at high doses (mechanism-based). Linaclotide has black box warning against use in pediatric patients <6 years old due to severe dehydrating diarrhea risk. In adults, diarrhea (16% linaclotide vs 5% placebo) is the main adverse effect, usually dose-dependent and manageable. No hepatic, renal, or cardiovascular toxicity. Minimal systemic bioavailability means essentially no systemic adverse effect profile for luminal GC-C agonists.

References

  • [1]de Sauvage FJ, et al. Cloning and functional expression of the mucosal epithelial receptor for Escherichia coli heat-stable enterotoxin. Cell. 1991;65(2):219-226.
  • [2]Lembo AJ, et al. Linaclotide for irritable bowel syndrome with constipation. N Engl J Med. 2011;365(6):527-536.
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See Also

uroguanylincholecystokininvasoactive-intestinal-peptidepeptide-yy
Categories: GI HormoneGC-C AgonistColonicIBS-CColorectal Cancer Prevention
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Verified Scientific Data Last audited:
Data Sources & External References
⬡ PubMed / NCBI, Research Literature ⬡ NCBI, Full-Text Articles ⬡ PubChem, Chemical Database
Source: peer-reviewed literature  ·  Domain: ascendpeptide.org

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