Antihypertensive peptides derived from egg proteins

The antihypertensive effect of peptides: a novel alternative to drugs?

Many types of bioactive peptides that inhibit angiotensin I, angiotensin I converting enzyme (ACE) and Ang II type 1 receptor (AT1) in the cardiovascular system contribute to the prevention and treatment of hypertension. These inhibitory peptides are derived from many food proteins or artificial synthetic products. Further research examining the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods. Our research also demonstrates that ACE inhibitory peptide LAP may lower blood pressure with no adverse effects.

The chicken egg white proteome

Using 1-D PAGE and LC-MS/MS and MS(3) we identified 78 chicken egg white proteins, 54 of which were identified in egg white for the first time. All proteins were quantitated by calculating their exponentially modified protein abundance index (emPAI). Some previously known egg white components not characterized by amino acid sequences before, such as alpha-2-macroglobulin, were associated to a sequence for the first time. The predicted sequence was confirmed by MS-sequenced peptides covering 42% of the entire sequence. alpha-2-Macroglobulin occurred in egg white at the same concentration as ovostatin with which it showed 35% identity. For other proteins, which were previously only characterized by partial sequences, such as beta-ovomucin or ovalbumin X, we identified and confirmed predicted complete sequences with a high coverage by MS-sequenced peptides. New proteins included a 7 kDa protein consisting of a single secretoglobin sequence (ovosecretoglobin), a 7 kDa protein with similarity to black swan cygnin and turkey meleagrin (gallin) and proteins involved in binding, modification, and possibly detoxification, of bacterial lipopolysaccaride. The list of egg white proteins provided is by far the most comprehensive at present and is intended to serve as a starting point for the isolation and functional characterization of interesting new proteins.

Vascular effects, angiotensin I-converting enzyme (ACE)-inhibitory activity, and antihypertensive properties of peptides derived from egg white

In this study, we have identified novel antihypertensive peptides derived from egg-white proteins. The sequences YRGGLEPINF and ESIINF produced an acute blood-pressure-lowering effect in spontaneously hypertensive rats upon a single oral administration. Our results suggest that the antihypertensive action could be attributed to a vascular-relaxing mechanism that would occur in vivo independently of angiotensin I-converting enzyme (ACE) inhibition, because neither these peptides nor their main digestion fragments, except for the dipeptide YR, acted as ACE inhibitors in vitro. The vasodilator and antihypertensive activity of the sequences ESI and NF would explain the blood-pressure-lowering effect of ESIINF. With regard to YRGGLEPINF, in addition to NF, YR appeared as the main fragment responsible for its activity. The dipeptide YR, named kyotorphin and previously identified as an endogenous analgesic neuropeptide in the central nervous system, showed strong vasodilator and antihypertensive properties. The structure-activity features of the vasodilator peptides are discussed.

Vasodilator effects of peptides derived from egg white proteins

The aim of this work was to investigate the effect of several peptides, identified before and after simulated gastrointestinal digestion of an egg white hydrolysate, on the vascular function, in rat aorta. The sequences IVF, RADHPFL and YAEERYPIL (0.1 mM) induced vasodilatation in intact aortic rings, with the maximum percentage of dilation corresponding to RADHPFL (40.5+/-7.0%). Two of the end products of the gastrointestinal digestion, RADHP and YPI, also showed vasodilator activity with degrees of relaxation higher than 50%. However, all these peptides failed to induce relaxation in endothelium-denuded aortic rings. The relaxation induced by RADHP was concentration-dependent and it was partially blocked by the nitric oxide synthase inhibitor L-NAME (100 microM) and by the B(1) bradykinin receptor antagonist Des-HOE 140 (30 nM), thus showing that it was mediated by NO production through the activation of B(1) bradykinin receptors. These findings suggest that these peptides could reduce the vascular resistance and could be used as functional food ingredients in the prevention and treatment of hypertension.

Food-derived peptides with biological activity: from research to food applications

Many peptides that are released in vitro or in vivo from animal or plant proteins are bioactive and have regulatory functions in humans beyond normal and adequate nutrition. Different health effects have been attributed to food-derived peptides, including antimicrobial properties, blood pressure-lowering (ACE inhibitory) effects, cholesterol-lowering ability, antithrombotic and antioxidant activities, enhancement of mineral absorption and/or bioavailability, cyto- or immunomodulatory effects, and opioid activities. Numerous products are already on the market or under development by food companies that exploit the potential of food-derived bioactive peptides and which ascribe scientifically evidenced health claims to consumption of these functional foods.