KPV: the C-terminal tripeptide of alpha-MSH and the PepT1 colitis studies

KPV (lysine-proline-valine) is the C-terminal tripeptide of alpha-melanocyte-stimulating hormone (alpha-MSH), a 13-amino-acid hormone made from proopiomelanocortin. Alpha-MSH has strong anti-inflammatory effects but also affects pigmentation. A 2008 review in Endocrine Reviews notes that KPV keeps the anti-inflammatory effect and lacks the pigmentary action, which is why it was singled out as an alternative.

How it is proposed to act

Before 2008 the mechanism was unknown. Dalmasso and colleagues tested KPV in human intestinal epithelial cells and human T cells stimulated with pro-inflammatory cytokines. They found that its effect depended on PepT1 expressed in both cell types, and they measured NF-kappaB activity, protein and RNA levels and cytokine secretion to follow the effect.

Mouse colitis models

A 2008 paper in Inflammatory Bowel Diseases tested KPV in two models, dextran sodium sulfate (DSS) colitis and CD45RBhi transfer colitis. In the DSS model, KPV-treated mice recovered earlier and regained body weight more strongly, with fewer inflammatory infiltrates and lower myeloperoxidase activity in the colon. KPV also led to recovery in the transfer model.

The same paper included mice with a nonfunctional melanocortin-1 receptor (MC1R). KPV rescued all of the treated animals from death during DSS colitis, so its effects appear to be at least partly independent of MC1R signaling.

The delivery problem

A 2017 paper in Molecular Therapy describes a formulation study. The authors loaded KPV into hyaluronic acid-functionalized nanoparticles of about 272 nm and delivered them in a chitosan and alginate hydrogel. The particles reached colonic epithelial cells and macrophages, accelerated mucosal healing, lowered TNF-alpha and worked better in a mouse ulcerative colitis model than nanoparticles without the hyaluronic acid. The authors frame selective delivery to target cells as one of two major challenges in treating ulcerative colitis, together with avoiding adverse effects.

What the evidence covers

Taken together, the studies describe a tripeptide with a proposed uptake route and consistent effects in several mouse models. They do not describe a tested effect in people.

• Chemical colitis models are not the same disease as human inflammatory bowel disease.
• PepT1 is induced in the colon during inflammation, so the uptake route may matter most in inflamed tissue.
• The MC1R-independent effects mean the melanocortin receptor story is incomplete.
• Formulation work on delivery suggests the free tripeptide may not reach target cells efficiently on its own, and the cited papers do not settle that.

A molecule this small is simple to identify by mass, with a calculated average of about 342 Da. Purity is the main thing a certificate for a tripeptide has to demonstrate.