Are intact peptides absorbed from the healthy gut in the adult human?

Abstract

For over 100 years it was believed that dietary protein must be completely hydrolysed before its constituent amino acids could be absorbed via specific amino acid transport systems. It is now known that the uptake of di- and tripeptides into the enterocyte is considerable, being transported across the intestinal endothelium by the PepT1 H+/peptide co-transporter. There is also evidence that some di- and tripeptides may survive cytosolic hydrolysis and be transported intact across the basolateral membrane. However, other than antigen sampling, the transport of larger intact macromolecules across the intestinal endothelium of the healthy adult human remains a controversial issue as there is little unequivocal in vivo evidence to support this postulation. The aim of the present review was to critically evaluate the scientific evidence that peptides/proteins are absorbed by healthy intestinal epithelia and pass intact into the hepatic portal system. The question of the absorption of oliogopeptides is paramount to the emerging science of food-derived bioactive peptides, their mode of action and physiological effects. Overall, we conclude that there is little unequivocal evidence that dietary bioactive peptides, other than di- and tripeptides, can cross the gut wall intact and enter the hepatic portal system in physiologically relevant concentrations.

Preparation, Bioavailability, and Mechanism of Emerging Activities of Ile‐Pro‐Pro and Val‐Pro‐Pro

“…The absorption of peptides from the intestinal lumen is via three different pathways: transcytosis via endocytosis, paracellular pathways via the tight junctions (TJs), and transporters mediated transcellular route (Miner‐Williams, Stevens, & Moughan, ). The H + ‐coupled peptide transporter 1 (PepT1), located on the apical membrane of enterocytes, is a bidirectional transporter, which contributes to the absorption of most di‐ and tripeptides (Miguel et al., ).…”

Bioactive peptides and proteins as alternative antiplatelet drugs

“…Peptides have very short biological half‐lives in vivo due to their rapid digestion in gastrointestinal system by proteolytic enzymes, protein‐modifying chemicals or through other clearance mechanisms. Therefore, peptides have uncertain therapeutic potential, which leaves room for several question marks in the process of drug design …”

Protein Kinetics and Metabolic Effects Related to Disease States in the Intensive Care Unit

“…In the gut lumen, the epithelial transporters are all noted to be limited by the extent of mucosal compromise. The luminal protein transporter PepT1 is primarily responsible for the majority of luminal protein uptake and is noted to be the first transporter system to be influenced by mucosal compromise 21 , 22 . Interestingly, it is also the first transporter to return when function is restored.…”