Antihypertensive Effect of Peptides Obtained from Enterococcus faecalis-Fermented Milk in Rats

Abstract 

Previous studies have demonstrated that milk fermented with Enterococcus faecalis decreases the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of spontaneously hypertensive rats. In this study, we evaluated the antihypertensive activity of the following peptide sequences: LHLPLP, LHLPLPL, LVYPFPGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV. These peptides isolated from E. faecalis-fermented milk showed in vitro angiotensin I-converting enzyme-inhibitory activity. Because the most potent angiotensin I-converting enzyme-inhibitory sequences were LHLPLP and LVYPFPGPIPNSLPQ-NIPP, we administered different doses of these peptides to spontaneously hypertensive rats. High doses of the remaining sequences were also administered to these animals. Water served as a negative control and captopril as a positive control. All products were administered orally. The SBP and DBP were measured before administration and also at 2, 4, 6, 8, and 24h after administration. Before administration of the different products, spontaneously hypertensive rats showed SBP and DBP values of 218±2.5 and 157±5.9mmHg, respectively (n=30). The sequences LHLPLP, LVYPF-PGPIPNSLPQNIPP, VLGPVRGPFP, and VRGPFPIIV caused clear and significant decreases in SBP, DBP, or both in the animals. In particular, the antihypertensive effect could be clearly established when 2 or 3mg/kg of LHLPLP was administered. These 2 doses of LHLPLP showed similar antihypertensive properties. Four hours after administration of captopril or the highest doses of the different peptides, the decreases in the SBP and the DBP (mmHg) were as follows: captopril (SBP=52±5.8, DBP=38.8±3.8), 3mg/kg of LHLPLP (SBP=25.3±8.2, DBP=29.5±7.6), 6mg/kg of LVYPFPGPIP-NSLPQNIPP (SBP=14.9±3.7, DBP=8.7±4.4), 10mg/kg of LHLPLPL (SBP=7.7±4.1, DBP=9.4±3.1), 10mg/kg of VLGPVRGPFP (SBP=16.2±5.8, DBP=21.64±3.2), and 10mg/kg of VRGPFPIIV (SBP=16.05±2.74, DBP=9.19±3.49). The results obtained suggest that the sequences LHLPLP, LVYPFPGPIPNSLPQ-NIPP, VLGPVRGPFP, and VRGPFPIIV could be responsible, at least in part, for the antihypertensive properties described for E. faecalis-fermented milk.

Key words: angiotensin I-converting enzyme inhibitory peptide, antihypertensive peptide, arterial blood pressure, spontaneously hypertensive rat