Uroguanylin / Guanylin

Guanylin is secreted mainly by colonic goblet cells and uroguanylin by proximal small intestinal enterochromaffin cells, both binding guanylate cyclase-C on the apical enterocyte surface to raise cGMP, activate CFTR and move fluid into the lumen. Uroguanylin is the more acid-tolerant of the two, active in the duodenum where guanylin is not, which is the property plecanatide preserves. Beyond fluid handling, prouroguanylin released after a meal is processed and reaches the hypothalamus, where GUCY2C activation on POMC neurons suppresses appetite — an endogenous gut-brain satiety axis that is blunted in obesity and is being explored as a non-incretin weight target. Uroguanylin also has renal effects, forming an enteric-renal axis that links dietary sodium intake to natriuresis.

Targets: Guanylate cyclase-C (GUCY2C), CFTR chloride channel, Hypothalamic POMC neurons, Renal sodium handling

• · There is no dosing regimen for uroguanylin or guanylin as therapeutics. The clinically useful versions of this biology are plecanatide and linaclotide. Anyone selling you 'uroguanylin' to inject is selling a research reagent.

Work out your exact syringe units →

• commonSecretory diarrhoea at supraphysiological exposure— The predictable consequence of over-activating GC-C, and the same mechanism by which E. coli heat-stable enterotoxin causes travellers' diarrhoea.
• commonUnknown in humans as an administered agent— There is no human safety profile because there is no human drug.

• Not a usable therapeutic — if you want this biology, use plecanatide or linaclotide, which are approved, stable and orally active.

• redundantplecanatide — Plecanatide is a stabilised uroguanylin analogue — it is this molecule, made druggable.
• redundantlinaclotide — Same receptor, reached by a bacterial-enterotoxin-derived scaffold instead.

• · Not applicable clinically. In research settings, faecal and plasma cGMP and stool water content are the standard readouts.

Endogenous human hormones with no approved therapeutic form. Sold only as research reagents.

• Valentino et al., GUCY2C hormone-receptor axis and appetite regulation (review)
• Forte, uroguanylin and guanylin peptides in intestinal and renal physiology (review)

The guanylin family is worth understanding not as a compound you would take but as the physiology that two approved drugs were reverse-engineered from, plus one genuinely underappreciated gut-brain axis. The secretory arm is the familiar one. Guanylin is produced mainly by colonic goblet cells; uroguanylin by proximal small intestinal enterochromaffin cells. Both bind guanylate cyclase-C on the apical enterocyte membrane, raise cGMP, activate protein kinase G II and open CFTR, moving chloride, bicarbonate and water into the lumen. The pH partition is the elegant part: uroguanylin retains activity in acidic proximal duodenum where guanylin does not, and guanylin works in the more alkaline colon. Evolution built a two-peptide system covering the whole pH gradient of the bowel. Plecanatide preserves uroguanylin's acid tolerance; linaclotide, derived from a bacterial toxin instead, sidesteps the question entirely by being pH-insensitive. The second arm is the interesting one and is not what these peptides are usually described as doing. Prouroguanylin released from the gut after a meal reaches the hypothalamus, where GUCY2C activation on pro-opiomelanocortin neurons suppresses appetite. This is a genuine endocrine gut-to-brain satiety axis — food in the small bowel producing a centrally acting hormonal signal that reduces further intake. It was demonstrated in mice by Valentino and colleagues, and it is blunted in obesity. It has been proposed as a non-incretin weight-regulation target, and given how crowded the GLP-1 space has become, it remains one of the more interesting unexploited pathways in gut endocrinology. The third arm is renal. Uroguanylin links dietary sodium intake to natriuresis — the enteric-renal axis — which is why an oral salt load produces more natriuresis than an equivalent intravenous one. This is a genuine physiological phenomenon that most people, including most clinicians, have never heard of. What you should take from this: the practical legacy of these hormones is plecanatide and linaclotide. If you want this biology, that is how you get it. Buying research-grade uroguanylin to inject is buying a reagent that cannot survive long enough to do anything useful and whose conformational isomer ratio you have no way of controlling.

The failure mode here is purely commercial. Research-grade uroguanylin and guanylin are sold as reagents, and people occasionally buy them believing they are getting a natural version of linaclotide. Three things are wrong with that. First, the natives are degraded rapidly by luminal proteases — that is the specific problem plecanatide's single amino acid substitution was designed to solve. Second, both peptides exist as two slowly interconverting topological isomers and only one is active. A research reagent has no specification for isomer ratio, so you have no idea what fraction of what you bought is even the active conformer. Third, the routes listed for these peptides in the research literature are intravenous and subcutaneous, which are exactly the wrong routes for a luminally acting hormone. Injecting a GC-C agonist bypasses the compartment where the receptor faces. The other thing that goes wrong is conceptual: because these are 'natural' hormones, they get marketed as safer than the analogues. Over-activating GC-C is the mechanism by which E. coli heat-stable enterotoxin causes travellers' diarrhoea. There is nothing gentle about this pathway when it is pushed.

• Guanylate cyclase-C (GUCY2C), intestinal — Not resolved to a published number in this session for either native peptide.

  Raises enterocyte cGMP, opens CFTR, drives chloride, bicarbonate and water secretion. Uroguanylin is active in acidic proximal small bowel; guanylin in the more alkaline colon.

• GUCY2C on hypothalamic POMC neurons — Not resolved.

  Appetite suppression. Prouroguanylin released postprandially is processed and acts centrally — a genuine gut-brain satiety axis, demonstrated in mice, blunted in obesity, and proposed as a non-incretin weight target.

• Renal GUCY2C and sodium handling — Not resolved.

  Natriuresis following an enteral sodium load. This enteric-renal axis explains why oral and intravenous salt loads produce different renal responses.

• GUCY2C as a colorectal tumour suppressor pathway — Not applicable.

  Loss of guanylin and uroguanylin expression is one of the earliest and most consistent events in colorectal carcinogenesis, and GUCY2C signalling has a demonstrated role in maintaining epithelial homeostasis. This is an active research area and is a large part of why the axis attracts attention beyond constipation.

• No human therapeutic trial of native uroguanylin or guanylin exists None

  Stated explicitly. These peptides have been used in human physiology studies but have never been developed as administered therapeutics, because their instability and conformational isomerism make them undruggable. Their entire clinical legacy is plecanatide and linaclotide.

Physiological and meal-linked. Secretion rises within an hour of eating, which is what makes the postprandial satiety signalling coherent. There is no therapeutic onset timeline because there is no therapeutic.

There is nothing to stack, because there is nothing to take. The only meaningful statement here is directional: if the biology you want is guanylate cyclase-C agonism, plecanatide is the stabilised uroguanylin and linaclotide is the enterotoxin-derived alternative. Both are approved, orally active and evidenced. Neither should be combined with the other. If what interests you is the satiety arm rather than the secretory arm, understand that no drug currently exploits it. GLP-1 agonists work through a completely different pathway. There is no product on the market or in late-stage development that targets the GUCY2C-POMC axis for weight.

The whole point of this entry is the comparison. Uroguanylin and guanylin are the templates; plecanatide and linaclotide are the products. Plecanatide is uroguanylin with a single Asp3-to-Glu3 change — arguably the smallest edit separating any endogenous hormone from a marketed drug in this entire corpus. It preserves the pH-dependent proximal activity that defines uroguanylin. Linaclotide came from the opposite direction entirely: it is modelled on E. coli heat-stable enterotoxin, with three disulfide bonds instead of two, greater rigidity, greater protease resistance, and no pH dependence. It is more potent, acts more distally, and causes substantially more diarrhoea. So the family gives you a natural experiment. Copy the hormone closely and you get plecanatide: modest, regionally restricted, low diarrhoea rate, one strength. Copy the pathogen instead and you get linaclotide: more potent, active throughout the bowel, more diarrhoea, three strengths to manage it. Both are approved and both work. The unexploited part of this family is the hypothalamic satiety axis, which no marketed drug currently touches.

Research reagent pricing only, which is per-milligram laboratory pricing and bears no relationship to a therapeutic cost. There is no monthly cost because there is no protocol.

• ?No published binding affinity for native uroguanylin or guanylin at GUCY2C was resolved in this session, so all affinity fields are qualitative.
• ?Blood-brain barrier penetration is entered as 'partial' on the basis of the demonstrated hypothalamic satiety axis; whether the peptide itself crosses, acts at a circumventricular organ, or signals via afferent routes was not established in what I could verify.
• ?The Forte review on uroguanylin and guanylin in intestinal and renal physiology referenced in the Core record was not resolved to a specific PMID in this session and is therefore not cited here.
• ?Half-life figures for the mature peptides were not resolved to numbers; 'very short' is qualitative.
• ?The two-topological-isomer property is well established for this peptide family in the structural literature, but I did not resolve a primary citation for it in this session.
• ?The claim that the satiety axis is blunted in obesity comes from the mouse work and its associated literature; the extent to which it holds in humans was not verified.

• A uroguanylin-GUCY2C endocrine axis regulates feeding in mice Valentino MA, Lin JE, Snook AE, et al., The Journal of Clinical Investigation, 2011 · PMID 21865642

  The paper establishing the gut-to-brain satiety arm. This is the most interesting and least known thing about the guanylin family.

• UniProt Q16661 (GUC2B_HUMAN) — guanylate cyclase activator 2B precursor; mature uroguanylin residues 97-112 UniProtKB

  Sequence verification for uroguanylin: NDDCELCVNVACTGCL, with disulfide bonds Cys4-Cys12 and Cys7-Cys15 in mature numbering.

• UniProt Q02747 (GUC2A_HUMAN) — guanylate cyclase activator 2A precursor; mature guanylin residues 101-115 UniProtKB

  Sequence verification for guanylin: PGTCEICAYAACTGC, 15 residues, processed from a high-molecular-weight intermediate.