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. 2017 Oct 24;61(1):1391666.
doi: 10.1080/16546628.2017.1391666. eCollection 2017.

Antihypertensive properties of tilapia (Oreochromis spp.) frame and skin enzymatic protein hydrolysates

Hsin-Chieh Lin  1 , Adeola M Alashi  2 , Rotimi E Aluko  2 , Bonnie Sun Pan  1 , Yu-Wei Chang  1
Affiliations

Antihypertensive properties of tilapia (Oreochromis spp.) frame and skin enzymatic protein hydrolysates

Hsin-Chieh Lin et al. Food Nutr Res. .

Abstract

Proteins from tilapia frame and skin can potentially be precursors of antihypertensive peptides according to the result of BIOPEP analyses. The aim was to generate peptides with inhibitory effects against angiotensin-converting enzyme (ACE) and renin from tilapia frame and skin protein isolates (FPI and SPI). The most active hydrolysate was then tested for blood pressure-lowering ability in spontaneously hypertensive rats (SHRs). Tilapia frame and skin protein hydrolysates (FPHs and SPHs) were respectively produced from FPI and SPI hydrolysis using pepsin, papain, or bromelain. The ACE-inhibitory activities of tilapia protein hydrolysates with varying degree of hydrolysis (DH) were evaluated. In order to enhance the activity, the hydrolysate was fractionated into four fractions (<1 kDa, 1-3 kDa, 3-5 kDa, and 5-10 kDa) and the one with the greatest ability to inhibit in vitro ACE and renin activities was subjected to oral administration (100 mg/kg body weight) to SHRs. Systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), and heart rates (HR) were subsequently measured within 24 h. The pepsin-hydrolyzed FPH (FPHPe) with the highest DH (23%) possessed the strongest ACE-inhibitory activity (IC50: 0.57 mg/mL). Its <1 kDa ultrafiltration fraction (FPHPe1) suppressed both ACE (IC50: 0.41 mg/mL) and renin activities more effectively than larger peptides. In addition, FPHPe1 significantly (p < 0.05) reduced SBP (maximum -33 mmHg), DBP (maximum -24 mmHg), MAP (maximum -28 mmHg), and HR (maximum -58 beats) in SHRs. FPHPe1 showed both in vitro and in vivo antihypertensive effects, which suggest tilapia processing coproducts may be valuable protein raw materials for producing antihypertensive peptides.

Keywords: Tilapia; angiotensin I-converting enzyme; frame protein hydrolysate; renin; skin protein hydrolysate; spontaneously hypertensive rats.

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Conflict of interest statement

No potential conflict of interest was reported by the authors.

Figures

Figure 1.
Figure 1.
(a) Degree of hydrolysis (DH) of tilapia frame protein isolate (FPI) during enzymatic hydrolysis. (b) DH of tilapia skin protein isolate (SPI) during enzymatic hydrolysis.
Figure 2.
Figure 2.
SDS-PAGE of samples from tilapia frame protein isolate (FPI, lane A), frame protein hydrolysates generated by pepsin (FPHPe, lane B), papain (FPHPa, lane C) and bromelain (FPHBr, lane D), skin protein isolate (SPI, lane E), and skin protein hydrolysates generated by pepsin (SPHPe, lane F), papain (SPHPa, lane G) and bromelain (SPHBr, lane H).
Figure 3.
Figure 3.
(a) In vitro Angiotensin-I converting enzyme (ACE) inhibitory activities of frame protein hydrolysates (FPHs: FPHPe, FPHPa, and FPHBr) and skin protein hydrolysates (SPHs: SPHPe, SPHPa, and SPHBr) generated by pepsin, papain, or bromelain. Bars with different letters are significantly different (p < 0.05). (b) The correlation plot between degree of hydrolysis (DH) and ACE inhibitory activities for FPHs (●) and SPHs (▲). The Pearson’s r value is 0.9607 and p < 0.05 represents the correlation is significant.
Figure 4.
Figure 4.
(a) In vitro angiotensin-I converting enzyme (ACE) inhibitory activities of the ultrafiltration fractions of pepsin-hydrolyzed frame protein hydrolysate (FPHPe) at of 0.6 mg/mL. (b) In vitro renin inhibitory activities of the fractions from FPHPe at of 1 mg/mL. Bars with different letters have significantly (p < 0.05) different mean values.
Figure 5.
Figure 5.
The effect of the < 1 kDa ultrafiltration fraction from pepsin-hydrolyzed frame protein hydrolysate (FPHPe1) on (a) systolic blood pressure (SBP), (b) diastolic blood pressure (DBP), (c) mean arterial pressure (MAP), and (d) heart rate (HR) of spontaneously hypertensive rats (SHRs) after oral gavage. Different letters above the bars indicate significant differences (p < 0.05).
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