Peptides studied for gut lining repair, barrier integrity, inflammation and bowel function

Human trials and regulatory labelling report that linaclotide increases intestinal fluid secretion and motility and relieves constipation symptoms.

Linaclotide is a small 14-amino-acid peptide taken by mouth that mimics natural gut hormones. It stays inside the intestine and switches on a receptor on the lining that causes cells to pump salt and fluid into the bowel. The extra fluid softens stool and speeds movement through the gut, which relieves constipation, and the same signalling appears to reduce gut pain.

• It binds the GC-C receptor, raising cGMP and stimulating secretion of chloride and bicarbonate into the intestinal lumen, which increases intestinal fluid and accelerates transit.^1,3

• It works by increasing intestinal fluid secretion, easing passage of stool and relieving constipation symptoms, and is taken on an empty stomach at least 30 minutes before the first meal.²

• In neonatal mice, age-dependent elevated GC-C agonism increased fluid secretion and was associated with increased mortality from dehydration within the first 24 hours; the drug is contraindicated in patients less than 2 years of age.¹

Human trials report that plecanatide significantly improved abdominal pain, bloating and bowel movement frequency in patients with constipation-predominant IBS.

Plecanatide is a synthetic 16-amino-acid peptide that copies a natural human hormone called uroguanylin. It acts locally in the gut, switching on the same lining-cell receptor as linaclotide to draw fluid into the bowel, soften stool and speed transit. In human trials it also reduced abdominal pain and bloating.

• Over 12 weeks, plecanatide 3 mg significantly improved abdominal pain and bloating in IBS-C patients compared with placebo.⁴

• In pooled phase 3 data, 23.3% of plecanatide patients versus 13.4% on placebo achieved ≥30% improvement in pain and bloating plus at least one more complete spontaneous bowel movement per week (p=0.002).⁴

• It stimulates fluid secretion and increases intestinal transit in animal models and significantly reduced the severity of straining, stool consistency and bloating in chronic constipation.^5,6

Human trials are underway — larazotide has been studied in phase III clinical trials as an oral adjunct in celiac disease — with supporting mechanistic work from rodent and porcine animal studies.

Larazotide acetate is a small 8-amino-acid peptide taken by mouth that stays in the gut and is not absorbed into the blood. It is described as helping the tight seals between the cells lining the intestine close and reassemble, so the barrier stays intact. In celiac disease, gluten loosens these seals and lets fragments slip through to spark an immune reaction; larazotide is thought to counter that.

• It is a single-chain peptide of eight amino acids that acts as a tight junction regulator to restore intestinal barrier function, taken orally as an adjunct in adult celiac disease.^7,8,9

• It has been associated with the redistribution and rearrangement of tight junction proteins and actin filaments to restore barrier function.^7,8,9

• Rodent and porcine animal studies demonstrate its role as a tight junction regulator in conditions beyond celiac disease, including collagen-induced arthritis in mice and intestinal ischemic injury in pigs.^7,9,8

Animal and laboratory studies suggest BPC-157 protects gut tissue and exerts anti-inflammatory effects, but human data are minimal.

BPC-157 is a synthetic 15-amino-acid peptide originally isolated from stomach juice. In animal and laboratory studies it protects the lining of the digestive tract, calms inflammation and helps tissue repair itself. It is notably stable and resists being broken down by stomach acid.

• It exerts significant protective effects on tissues including the esophagus, stomach, duodenum and colorectal mucosa, and has demonstrated cytoprotective and anti-inflammatory properties with a role in maintaining epithelial integrity.¹⁰

• It stimulates mRNA of the growth factor EGR-1 in Caco-2 intestinal cells and is stable in stomach acid ex vivo for at least 24 hours.¹¹

• A narrative review reports it exerts anti-inflammatory effects, though only three pilot studies in humans exist.¹²

Human trials support teduglutide: it is approved in the US and EU for short bowel syndrome, with phase III evidence of reduced parenteral support requirements.

Teduglutide is a lab-made, longer-lasting copy of a natural gut hormone called GLP-2. It tells the cells lining the intestine to grow, repair themselves and resist dying off, making the surface healthier and better at absorbing fluid and nutrients. It is used in people with short bowel syndrome, who have lost much of their functional intestine, to help the remaining bowel absorb more.

• It is approved in the US and EU for short bowel syndrome-associated intestinal failure and improves intestinal adaptation following resection.^13,14

• In a 3-week phase 2 metabolic balance study it increased intestinal wet weight absorption by approximately 700 g/day.¹³

• In a phase III trial in adults dependent on parenteral support, significantly more teduglutide 0.05 mg/kg/day than placebo recipients achieved and maintained a ≥20% reduction in weekly parenteral support volume.¹⁴

• GLP-2 promotes repair of damaged intestinal mucosa, enhances intestinal blood supply and regulates mucosal barrier function.¹⁵

Human trials and reviews report that lactoferrin enhances iron absorption and may exert anti-inflammatory effects, with additional animal and laboratory support for its intestinal actions.

Lactoferrin is a natural iron-binding defence protein found in milk, tears, saliva and immune cells. Researchers describe it as fighting microbes, calming inflammation and helping the gut lining grow. It works partly by locking away the iron that many harmful bacteria need to grow while sparing beneficial gut bacteria.

• It can stimulate intestinal cell proliferation and differentiation, causing expansion of tissue mass and absorptive capacity, and oral treatment may have an anti-inflammatory effect in pregnant women.¹⁶

• It enhances intestinal absorption of iron and improves hemoglobin production.¹⁸

• In simulated digestion, peptides released from human and recombinant human lactoferrin correlated in the intestinal phase (r between 0.63 and 0.70), and intact protein retention was similar across lactoferrin types.¹⁷

Animal and laboratory studies suggest KPV reduces intestinal inflammation and colitis severity through PepT1-mediated cytokine suppression.

KPV is a three-amino-acid fragment (Lys-Pro-Val) taken from the tail of a natural hormone, and most sources describe it as calming inflammation. In laboratory and animal studies it enters gut cells through a transporter and quiets inflammatory signals, reducing the severity of colitis. It also appears to help protect the intestinal barrier.

• It reduces pro-inflammatory cytokine secretion in human intestinal epithelial cells and T cells, acting via PepT1, and oral administration reduced the incidence of DSS- and TNBS-induced colitis in mice.¹⁹

• In TNBS-induced ulcerative colitis rats, a KPV hydrogel attenuated body weight loss and disease activity, with recovery of the colonic epithelial barrier, crypt and goblet cells.²⁰

• PepT1 is overexpressed in the colonic epithelial cells of chronic ulcerative colitis, enabling KPV-targeted delivery into these cells.²¹

Animal and laboratory studies suggest elafin protects the gut mucosa in inflammatory and gluten-sensitization conditions, and mucosal delivery is being considered therapeutically.

Elafin is a human protein made naturally at the body's surfaces, including the gut lining, that protects tissue from being destroyed during inflammation. It blocks destructive enzymes released by immune cells and has direct antimicrobial activity. Researchers are investigating delivering extra elafin to the gut to calm inflammation and support tissue repair.

• Accumulating evidence demonstrates protective effects of trappin-2/elafin in gut disorders associated with acute or chronic inflammation, or with gluten sensitization.^22,23

• Therapeutic delivery of trappin-2/elafin at the intestinal mucosal surface is being considered to ensure intestinal tissue repair.^22,23

• It reduces collagen synthesis in intestinal fibroblasts by inhibiting cathepsin S and protease-activated receptor 2 activities.²⁴