title: Kinetics of the inhibition of renin and angiotensin I-converting enzyme by cod (Gadus morhua) protein hydrolysates and their antihypertensive effects in spontaneously hypertensive rats.
abstract: BACKGROUND
  Cod muscle has a balanced protein profile that contains potentially bioactive amino acid sequences. However, there is limited information on release of these peptides from the parent proteins and their ability to modulate mammalian blood pressure.
  
  
  OBJECTIVE
  The aim of this study was to generate cod antihypertensive peptides with potent in vitro inhibitory effects against angiotensin-converting enzyme (ACE) and renin. The most active peptides were then tested for systolic blood pressure (SBP)-reducing ability in spontaneously hypertensive rats (SHRs).
  
  
  METHODS
  Cod protein hydrolysate (CPH) was produced by subjecting the muscle proteins to proteolysis first by pepsin and followed by trypsin+chymotrypsin combination. In order to enhance peptide activity, the CPH was subjected to reverse-phase (RP)-HPLC separation to yield four fractions (CF1, CF2, CF3, and CF4). The CPH and RP-HPLC fractions were each tested at 1 mg/mL for ability to inhibit in vitro ACE and renin activities. CPH and the most active RP-HPLC fraction (CF3) were then used for enzyme inhibition kinetics assays followed by oral administration (200 and 30 mg/kg body weight for CPH and CF3, respectively) to SHRs and SBP measurements within 24 h.
  
  
  RESULTS
  The CPH, CF3, and CF4 had similar ACE-inhibitory activities of 84, 85, and 87%, which were significantly (p<0.05) higher than the values for CF1 (69%) and CF2 (79%). Conversely, the CF3 had the highest (63%) renin-inhibitory activity (p<0.05) when compared to CPH (43%), CF1 (15%), and CF4 (44%). CPH and CF3 exhibited uncompetitive mode of ACE inhibition, whereas renin inhibition was non-competitive. Even at a 6.7-fold lower dosage, the CF3 significantly (p<0.05) reduced SBP (maximum -40.0 mmHg) better than CPH (maximum -19.1 mmHg).
  
  
  CONCLUSIONS
  RP-HPLC fractionation led to enhanced antihypertensive effects of cod peptides, which may be due to a stronger renin-inhibitory activity.
authors.affiliation: Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, Canada.|The Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, Canada.
authors.forename: Abraham T
authors.initials: AT
authors.lastname: Girgih
authors.affiliation: Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, Canada.|The Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, Canada.
authors.forename: Ifeanyi D
authors.initials: ID
authors.lastname: Nwachukwu
authors.affiliation: Department of Process Engineering and Applied Science, Dalhousie University, Halifax, Canada.
authors.forename: Fida
authors.initials: F
authors.lastname: Hasan
authors.affiliation: Department of Food Science and Technology, Federal University of Technology, Akure, Nigeria.
authors.forename: Tayo N
authors.initials: TN
authors.lastname: Fagbemi
authors.affiliation: Department of Process Engineering and Applied Science, Dalhousie University, Halifax, Canada.
authors.forename: Tom
authors.initials: T
authors.lastname: Gill
authors.affiliation: Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, Canada.|The Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, Canada; rotimi.aluko@umanitoba.ca.
authors.forename: Rotimi E
authors.initials: RE
authors.lastname: Aluko
keywords: IC50; angiotensin I-converting enzyme; cod; enzyme inhibition kinetics; protein hydrolysate; renin; spontaneously hypertensive rats; systolic blood pressure