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Non-healing chronic diabetic wound treatment remains an unsolved healthcare challenge and still threatens patients' lives. Recently, hydrogel dressings based on natural biomaterials have been widely investigated to accelerate the healing of diabetic wounds. In this study, we introduce a bioactive hydrogel based on fish gelatin (FG) as a candidate for diabetic wound treatments, which is a recently emerged substitute for mammalian derived gelatin. The composite hydrogel simply fabricated with FG and oxidized hyaluronate (OHy) through Schiff base reaction could successfully accelerate wound healing due to their adequate mechanical stability and self-healing ability. In vitro studies showed that the fabricated hydrogels exhibited cytocompatibility and could reduce pro-inflammatory cytokine expression such as NO, IL-1β, TNF-α, and PGE 2 in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. In addition, the production of reactive oxygen species (ROS), a key marker of free radicals producing oxidative stress, was also reduced by fabricated hydrogels. Furthermore, in vivo experiments demonstrated that the hydrogel could promote wound closure, re-epithelialization, collagen deposition, and protein expression of CD31, CD206, and Arg1 in diabetic mice models. Our study highlights the advanced potential of FG as a promising alternative material and indicates that FOHI can be successfully used for diabetic wound healing applications.

The aim of this study was to investigate antihypertensive effect of bioactive peptides from skate (Okamejei kenojei) skin gelatin. The Alcalase/protease gelatin hydrolysate below 1 kDa (SAP) exhibited the highest angiotensin-I converting enzyme (ACE) inhibition compared to other hydrolysates. SAP can decrease systolic blood pressure significantly in spontaneously hypertensive rats. SAP inhibited vasoconstriction via PPAR-γ expression, activation and phosphorylation of eNOS in lungs. Moreover, the expression levels of endothelin-1, RhoA, α-smooth muscle actin, cleaved caspase 3 and MAPK were decreased by SAP in lungs. Vascularity, muscularization and cellular proliferation in lungs were detected by immunohistochemical staining. Finally, two purified peptides (LGPLGHQ, 720Da and MVGSAPGVL, 829Da) showed potent ACE inhibition with IC50 values of 4.22 and 3.09 μM, respectively. These results indicate that bioactive peptides isolated from skate skin gelatin may serve as candidates against hypertension and could be used as functional food ingredients., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Skin gelatin of skate (Okamejei kenojei) was hydrolyzed using Alcalase, flavourzyme, Neutrase and protamex. It was found that the Alcalase hydrolysate exhibited the highest angiotensin-I converting enzyme (ACE) inhibitory activity. Then, Alcalase hydrolysate was further hydrolyzed with protease and separated by an ultrafiltration membrane system. Finally, two peptides responsible for ACE inhibitory activity were identified to be MVGSAPGVL (829Da) and LGPLGHQ (720Da), with IC50 values of 3.09 and 4.22μM, respectively. Moreover, the free radical-scavenging activity of the purified peptides was determined in human endothelial cells. In addition, the antioxidative mechanism of the purified peptides was evaluated by protein and gene expression levels of antioxidant enzymes. The current study demonstrated that the peptides derived from skate skin gelatin could be used in the food industry as functional ingredients with potent antihypertensive and antioxidant benefits., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Gelatin was extracted from the skin of Japanese flounder ( Palatichtys olivaceus ) and was subjected to enzymatic hydrolysis. The peptic hydrolysate resulted in a potent antioxidative peptide Gly-Gly-Phe-Asp-Met-Gly (582 Da), which bears +12.61 kcal/mol hydrophobicity. The antioxidative potential of the peptide was characterized by analyzing the protective effect of the peptide on reactive oxygen species (ROS)-mediated intracellular macromolecule damage. It was found that the peptide is a potent scavenger of intracellular ROS, thereby protecting the radical-mediated damage of membrane lipids, proteins, and DNA. Moreover, the peptide is capable of upregulating the expression of inherent antioxidative enzymes, superoxide dismutase-1, glutathione, and catalase. Collectively, it can be concluded that Japanese flounder skin, a processing byproduct of filleting, can be effectively used to produce a bioactive peptide with potent antioxidant capacity.

Potent antioxidative peptides were purified from Pacific cod (Gadus macrocephalus) skin gelatin using alcalase, neutrase, papain, trypsin, pepsin, and α-chymotrypsin. Among them, the papain hydrolysate exhibited the highest antioxidant activity. Therefore, it was further purified and obtained two peptides with amino acid sequences of Thr-Cys-Ser-Pro (388 Da) and Thr-Gly-Gly-Gly-Asn-Val (485.5 Da). The antioxidant activity of the purified peptides was performed by electron spin resonance technique. Moreover, their intracellular free radical scavenging activity using 2',7'-dichlorofluorescin diacetate and the protective effect against oxidation-induced DNA damage were evaluated in mouse macrophages (RAW 264.7 cells). Furthermore, both peptides have shown potential angiotensin-I converting enzyme inhibitory effect. The present study demonstrated that the peptides derived from Pacific cod (G. macrocephalus) skin gelatin could be used in the food industry as functional ingredients with potent antioxidative and antihypertensive benefits., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A peptide possessing antihypertensive activity was purified from Nile tilapia ( Oreochromis niloticus ) gelatin using alcalase, Pronase E, pepsin, and trypsin. Among them, the alcalase hydrolysate exhibited the highest angiotensin converting enzyme (ACE) inhibitory activity. Therefore, it was further analyzed, and a potent ACE inhibitory peptide of DPALATEPDPMPF (1382 Da) was separated and purified. In addition, the protective effect of the purified peptide against free radical-induced cellular and DNA damage in murine microglial cells (BV-2) was determined. These results suggest that the peptide isolated from Nile tilapia (O. niloticus) gelatin acts as a candidate against hypertension and oxidative stress and could be used in health-functional foods.

BACKGROUND: In order to utilize tilapia skin gelatin hydrolysate protein, which is normally discarded as industrial waste in the process of fish manufacture, we study the in vivo and in vitro angiotensin‐I‐converting enzyme (ACE) inhibitory activity of the peptide Leu‐Ser‐Gly‐Tyr‐Gly‐Pro (LSGYGP). The aim was to provide a pharmacological basis of the development of minimal side effects of ACE inhibitors by comparative analysis with captopril in molecular docking. RESULTS: This peptide from protein‐rich wastes showed excellent ACE inhibitory activity (IC50 = 2.577 μmol L−1) and exhibited a mixed noncompetitive inhibitory pattern with Lineweaver–Burk plots. Furthermore, LSGYGP and captopril groups both showed significant decreases in blood pressure after 6 h and maintained good digestive stability over 4 h. Molecular bond interactions differentiate competitive captopril upon hydrogen bond interactions and Zn(II) interaction. The C‐terminal Pro generates three interactions (hydrogen bonds, hydrophilic interactions and Van der Waals interactions) in the peptide and effectively interacts with the S1 and S2 pockets of ACE. CONCLUSION: LSGYGP, with an IC50 value of 2.577 μmol L−1, has an antihypertensive effect in spontaneously hypertensive rats. Through comparison with captopril, this study revealed that LSGYGP may be a potential food‐derived ACE inhibitory peptide and could act as a functional food ingredient to prevent hypertension. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: In the present study, a peptide possessing antioxidant properties was isolated from Nile tilapia (Oreochromis niloticus) scale gelatin. Gelatin protein was hydrolyzed using alcalase, pronase E, trypsin and pepsin. Antioxidant efficacy of respective hydrolysates were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide radical anion scavenging activities. Moreover, protective effect on DNA damage caused by hydroxyl radicals generated was determined. Further, the level of reactive oxygen species (ROS) was determined using a fluorescence probe, 2′,7′-dichlorofluorescin diacetate (DCFH-DA), which could be converted to highly fluorescent dichlorofluorescein (DCF) with the presence of intracellular ROS on mouse macrophages, RAW 264.7 cells. Among hydrolysates, alcalase-derived hydrolysate exhibited the highest antioxidant activity compared to other enzymatic hydrolysates. Therefore, it was further analyzed and the sequence of an active peptide present in it was identified as Asp-Pro-Ala-Leu-Ala-Thr-Glu-Pro-Asp-Pro-Met-Pro-Phe (1382.57Da). This peptide showed no cytotoxic effect on mouse macrophages (RAW 264.7) and human lung fibroblasts (MRC-5). In addition, it scavenged hydroxyl, DPPH and superoxide radicals at the IC50 values of 7.56, 8.82 and 17.83μM, respectively. These results suggest that the peptide derived from Nile tilapia (O. niloticus) scale gelatin acts as a candidate against oxidative stress and could be used as a potential functional food ingredient. [Copyright &y& Elsevier]

Angiotensin- I- converting enzyme (ACE) is crucial in the control of hypertension and the development of type- 2 diabetes and other diseases associated with metabolic syndrome. The aim of this work was to utilize Pacific cod skin to purify ACE inhibitory peptides. First, gelatin was extracted from Pacific cod skin and hydrolyzed with several enzymes (pepsin, papain, α-chymotrypsin, trypsin, neutrase, and alcalase). The pepsin hydrolysate showed the strongest ACE inhibitory effect and was further fractionated into different ranges of molecular weight (<1, 1–5, 5–10, and >10 kDa) using ultrafiltration (UF) membranes. The peptic hydrolysate below 1 kDa resulted in two potent ACE inhibitory peptides, GASSGMPG (662 Da) and LAYA (436 Da), with IC 50 values (concentration required to decrease the ACE activity by 50%) of 6.9 and 14.5 μM, respectively. Moreover, to explore the interaction between the peptides and ACE molecule, the tertiary structure of ACE and docking simulation to the peptides were predicted using Docking Server. Pacific cod peptides can be used as functional food ingredients to prevent hypertension and its related diseases. [ABSTRACT FROM AUTHOR]

Abstract: Seafood processing by-product, Pacific cod (Gadus macrocephalus) skin, was utilised to purify an active peptide with ACE inhibitory and antioxidant activities. Gelatin was extracted from the skin and it was hydrolysed with gastrointestinal endopeptidases (pepsin, trypsin and α-chymotrypsin). Assay-guided purification of the hydrolysate resulted in an active peptide, Leu-Leu-Met-Leu-Asp-Asn-Asp-Leu-Pro-Pro (1301Da). The peptide showed potent non-competitive ACE inhibition (IC 50 =35.7μM) and effectively protects cellular macromolecules from reactive oxygen species (ROS) mediated damage. The peptide significantly reduced the oxidation levels of membrane lipids, proteins and DNA in RAW264.7 cells by effectively scavenging the intracellular ROS. Moreover, it was found that the peptide treatment upregulated the m-RNA expression of cellular antioxidative enzymes (superoxide dismutase, glutathione and catalase) and thereby enhanced the intracellular antioxidant mechanisms. These findings suggest that Pacific cod skin could be effectively bioconverted to produce a bioactive peptide, which could be used as a functional food ingredient to control ACE activity and oxidative stress. [Copyright &y& Elsevier]