Possible mechanisms of action of amaranth antihypertensive peptides an in vivo, ex vivo and in vitro study

RINALDI, GUSTAVO; SUÁREZ, SANTIAGO ; QUIROGA ALEJANDRA,; APHALO, PAULA ; AÑÓN, M. CRISTINA

Campinas

Congreso; 1st CIAPep Iberoamerican Congress on Bioactive Peptides; 2019

Instituto de Tecnologia de Alimentos (Ital)

Hypertension is characterized by an increased activity of the main enzymes (renin and angiotensin converting enzyme, ACE) belonging to renin-angiotensin system (RAS). Bioactive peptides of animal and vegetal origin exert anti-hypertensive effects mainly through the inhibition of RAS enzymes and the increase of NO levels. Studies carried out in our laboratory have demonstrated the existence of cryptic peptides in amaranth proteins.The aim of this work was to analyze the hypotensive effect of amaranth peptides to inhibit ACE and renin in vitro and study the possible mechanism of action of these peptides in vivo and ex vivo. Samples tested were amaranth protein isolate (API) and hydrolysate (AH), VIKP (synthetic peptide), O/W 20:80 emulsions prepared with sunflower oil and 1:1 protein mixtures of API and AH at pH 2 and with a total protein concentration of 2% with or without the VIKP peptide [E and E+VIKP, respectively]. Commercial ACE and renin inhibitors were employed as positive controls. We also tested the effect of protection against gastrointestinal digestion (GID) exerted by an O:W emulsion on the integrity of the antihypertensive peptides. Peptides present in AH inhibited ACE and renin in vitro (IC50=0.14 mg/ml and 0.6 mg/ml, respectively). O/W 20:80 emulsions inhibited ACE (IC50=0.29 mg/ml) while no activity was detected on renin. All samples tested produced a decrease in blood pressure (SBP). The animals treated with emulsion and emulsion+peptide showed the most significant reduction in SBP (42±2 mmHg and 35±2 mmHg, respectively). The results presented suggest that after GID, a variety of peptides with biological activities were released or were resistant to this process. These peptides play a role in the regulation of the SBP by acting on plasma ACE, plasma renin and the vascular system. These results support the use of amaranth protein/peptides in the elaboration of functional foods for hypertensive individuals.