Increase in food-derived liner and cyclic peptide levels in human blood by ingestion of porcine elastin peptides

Elastin is an extracellular matrix protein that contributes to the elasticity of tissues such as blood vessels and dermis, and mainly consists of four amino acids: Pro, Gly, Ala, and Val. The ingestion of elastin peptides, which are enzymatic hydrolysates of elastin, improves the elasticity of human skin and blood vessels, and discomfort in human knees. Our previous studies revealed that elastin peptide ingestion increases Pro-Gly concentrations in human blood at the micromolar level, indicating that Pro-Gly may mediate the beneficial effects by elastin peptide ingestion. In contrast, no increase in the concentrations of dipeptides containing Ala or Val was detected. In addition, we previously detected an increase in cyclic peptide concentrations in human blood after collagen peptide ingestion. The objective of this study was to identify active component candidates for clarification of the beneficial effects mechanisms by detecting linear and cyclic dipeptides consisting of Pro, Gly, Ala, and Val using liquid chromatography-mass spectrometry with stable isotope-labeled internal standards. Seven healthy male subjects fasted for 12 h before ingesting 0.4 g/kg body weight porcine elastin peptides and blood was collected 0.25, 0.5, 1, 1.5, 2, and 4 h after ingestion.

Similar to our previous results, approximately 14 nmol/mL of Pro-Gly was detected in the plasma of the subjects after ingestion. In addition, significant increases in Pro-Ala and Gly-Pro were detected at 1/50 lower concentration than Pro-Gly in the plasma samples. Moreover, plasma cyclic Gly-Ala, Gly-Pro, Pro-Ala, and Pro-Val concentrations significantly increased after ingestion, with a maximum concentration of approximately 1–4 nmol/mL. Except for Pro-Gly, the dipeptides showed higher plasma concentrations in the cyclic form than the linear form. Our results indicate that these linear and cyclic dipeptides may be involved in the mechanisms underlying the beneficial effects of elastin peptide ingestion.