Food-Derived ACE and DPP-4 Inhibitory Peptides Survive Digestion but Struggle to Cross the Intestinal Wall

Bioactive dipeptides YA, VL, and IY from poultry hydrolysates resisted simulated gastrointestinal digestion. However, Caco-2 cell monolayer absorption tests showed peptide concentrations decreased on the apical side but were not detected basolaterally — indicating cellular uptake/metabolism rather than transcellular transport. The peptides downregulated peptide transporter expression, CDX2 transcription factor, and tight junction protein TJP1.

In vitro study using INFOGEST static digestion model for gastrointestinal stability and Caco-2 cell monolayers for intestinal absorption. Peptide identification by LC-MS. Gene expression analysis of Caco-2 cells after peptide stimulation. 4-hour incubation period for transport studies.

Many food-derived peptides show impressive activity in lab tests but fail to deliver benefits when consumed orally because they can't reach the bloodstream in sufficient quantities. This study provides an important reality check: even peptides that survive digestion face a second major barrier — crossing the intestinal wall. Understanding this bottleneck is essential for developing effective nutraceutical peptide products.

The bioactive peptide field is booming with thousands of peptides showing enzyme-inhibiting activity in vitro. However, this study highlights the critical gap between test tube activity and real-world bioavailability. The food and nutraceutical industry needs to address intestinal absorption, not just enzyme inhibition, to deliver on the promise of bioactive peptide ingredients.

Caco-2 cells, while the gold standard for intestinal absorption studies, are cancer-derived cells that may not perfectly represent normal intestinal epithelium. The 4-hour timeframe may be insufficient to capture slow transcellular transport. The study used individual dipeptides rather than the complete hydrolysate, which may behave differently. No in vivo absorption data was collected.