PepT1-mediated tripeptide KPV uptake reduces intestinal inflammation
Dalmasso G, Charrier-Hisamuddin L, Nguyen HTT, Yan Y, Sitaraman S, Merlin D
Gastroenterology (2008)
KPV enters epithelial and immune cells through PepT1, suppresses NF-κB at nanomolar concentrations, and reduces colitis severity in two independent mouse models — the foundational paper for the entire current case for KPV in inflammatory bowel disease.
This 2008 *Gastroenterology* paper from the Merlin laboratory at Emory established the mechanistic basis for current interest in KPV as an inflammatory bowel disease therapeutic. Working in human intestinal epithelial cell lines and Jurkat T cells, the authors first showed that KPV inhibits NF-κB and MAP-kinase activation at nanomolar concentrations and suppresses pro-inflammatory cytokine secretion. They then demonstrated that KPV is transported into both epithelial and immune cells via PepT1, an oligopeptide transporter whose expression is upregulated during intestinal inflammation — meaning the tripeptide is preferentially concentrated where inflammation is highest. Crucially, the anti-inflammatory effect was preserved in mice with non-functional MC1R, ruling out melanocortin-receptor-mediated activity. The authors then tested oral KPV via drinking water in two independent mouse colitis models (DSS- and TNBS-induced): the peptide reduced disease severity, decreased pro-inflammatory cytokine expression, and reduced myeloperoxidase-marked neutrophil infiltration by approximately 50%. The paper concludes by framing PepT1-targeted delivery of KPV (and PepT1-transported small peptides more broadly) as a candidate therapeutic strategy for IBD.
The paper is a mechanistic study with rodent confirmation, not a human clinical trial. The two colitis models (DSS and TNBS) are useful but imperfect surrogates for human ulcerative colitis or Crohn's disease — they capture acute mucosal inflammation but not the relapsing-remitting biology, fibrostenotic complications, or extra-intestinal manifestations of human IBD. The study does not address chronic-dosing safety, dose-response across a wide range, or efficacy after established mucosal damage rather than during induction of inflammation. Subsequent human translation has been slow; nanoparticle-delivery follow-up work in the same lineage has expanded the mechanism story but not yet produced a large randomized human trial. The funding and conflict-of-interest disclosures in this paper are routine; the limit of evidence is the mouse-to-human translation, not the rigor of the model itself.