Bioavailability of the antihypertensive peptide LHLPLP: Transepithelial flux of HLPLP

The β-casein peptide f(133-138), with the sequence LHLPLP, was responsible for the angiotensin converting enzyme (ACE)-inhibitory and antihypertensive activity of fermented milk produced with different Enterococcus faecalis strains. The aim of this study was to investigate if the ACE-inhibitory peptide LHLPLP is resistant to brush border peptidases and to examine its mechanism for transepithelial transport using Caco-2 cells. LHLPLP was hydrolysed by cellular peptidases to HLPLP prior to transport across the intestinal epithelium. The effect of some inhibitors on the transport of HLPLP indicated that paracellular passive diffusion is likely the main mechanism of transport across the cell layer. This was confirmed by measuring the flux of the peptide after reversion of the flux from the basolateral to the apical chamber. In vitro incubation HLPLP in human plasma showed that the peptide remained practically intact 1 h after incubation, and degradation to one half was observed at 2 h of incubation.