Antioxidant synergistic anti-inflammatory effect in the MAPK/NF-κB pathway of peptide KGEYNK (KK-6) from giant salamander (Andrias davidianus).

BACKGROUND: Giant salamander protein peptide is a peptide with rich functional properties. Giant salamander protein peptide KGEYNK (KK-6) is a peptide with both antioxidant and anti-inflammatory properties. The antioxidant and anti-inflammatory mechanisms of KK-6 are still unclear. When we studied the functional mechanism of KK-6, we found that the antioxidant property of KK-6 has a synergistic and promoting effect on anti-inflammatory properties. RESULTS: KK-6 enhances cellular resistance to LPS via the MAPK/NF-κB signaling pathway, leading to increased levels of inflammatory factors: interleukin-1ß (764.81 ng mL-1), interleukin-6 (1.06 ng mL-1) and tumor necrosis factor-α (4440.45 ng mL-1). KK-6 demonstrates potent antioxidant properties by activating the Nrf2 signaling pathway, resulting in elevated levels of antioxidant enzymes (glutathione peroxidase: 0.03 µg mL-1; superoxide dismutase: 0.589 µg mL-1) and a reduction in the concentration of the oxidative product malondialdehyde (967.05 µg mL-1). CONCLUSION: Our findings highlight the great potential of KK-6, a peptide extracted from giant salamander protein, as a remedy for intestinal inflammation. Through its dual role as an antioxidant and anti-inflammatory agent, KK-6 offers a promising avenue for alleviating inflammation-related damage and oxidative stress. This study lays the foundation for further exploration of giant salamander products and highlights their importance in health and novel food development. © 2024 Society of Chemical Industry.

Effect of Ca2+ on 3D printing accuracy and antioxidant efficacy of nano starch-lutein surimi: mechanical properties, chemical bonds and release rate.

BACKGROUND: Nano starch-lutein (NS-L) can be used in three-dimensional (3D) printed functional surimi. However, the lutein release and printing effect are not ideal. The purpose of this study was to facilitate the function and printing properties of surimi by adding the combination of calcium ion (Ca2+ ) and NS-L. RESULTS: Printing properties, lutein release and antioxidation of printed Ca2+ -NS-L-surimi were determined. The NS-L-surimi with 20 mM kg-1 Ca2+ had the best printing effects (fine accuracy, 99 ± 1%). Compared to NS-L-surimi, the structure became denser after adding Ca2+ , the gel strength, hardness, elasticity, yield stress (τ), water holding capacity of Ca2+ -NS-L-surimi increased by about 17 ± 4%, 3 ± 1%, 9 ± 2%, 20 ± 4%, 40 ± 5% respectively. These enhanced mechanical strength and self-supporting ability to resist binding deformation and improve printing accuracy. Moreover, salt dissolution and increased hydrophobic force by Ca2+ stimulated protein stretching and aggregation, leading to enhancement of gel formation. Decreased printing effects of NS-L-surimi with excessive Ca2+ (> 20 mM kg-1 ) caused by excessive gel strength and τ, leading to strong extrusion force and low extrudability. Additionally, Ca2+ -NS-L-surimi had higher digestibility and lutein release rate (increased from 55 ± 2% to 73 ± 3%), because Ca2+ made NS-L-surimi structure porous, which promoted contact of enzyme-protein. Furthermore, weakened ionic bonds reduced electron binding bondage that combined with released lutein to provide more electrons for enhancing antioxidation. CONCLUSION: Collectively, 20 mM kg-1 Ca2+ could better promote printing process and function exertion of NS-L-surimi, facilitating the application of 3D printed functional surimi. © 2023 Society of Chemical Industry.

Purification and identification of a novel hypotensive and antioxidant peptide from porcine plasma.

BACKGROUND: Pig plasma contains a large amount of protein. Porcine plasma polypeptide can be prepared by the enzymatic hydrolysis of porcine plasma protein. The present study investigated the function, structure, and mechanisms of porcine plasma peptides. RESULTS: The results showed that WVRQAPGKGL had a major ability to scavenge hydroxyl radical scavenging activity (HRSA) (35.25%), 2,2'-azino-bis (3-ethylbenzothiazo line-6-sulfonic acid) diammonium salt radical scavenging activity (ABTS RSA) (93.09%) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH RSA) (25.72%), as well as in angiotensin converting enzyme (ACE) inhibition (91.64%). WVRQAPGKGL could inactivate ACE by binding to Zn2+ because of the presence of carboxyl in WVRQAPGKGL. The ACE inhibition, HRSA, and DPPH of synthetic WVRQAPGKGL were improved by 12.70%, 16.06%, and 117.11% respectively after in vitro digestion. It (0.1 mg mL-1 ) also increased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) by 59.78%, 69.05%, and 59.06%, and decreased reactive oxygen species (ROS) and malondialdehyde (MDA) by 22.08% and 50.59%, respectively, to protect HepG2 cells induced by H2 O2 . Furthermore, in a spontaneously hypertensive rat (SHR) model, the systolic blood pressure (SBP) and diastolic blood pressure (DBP) of the peptide group (30 mg kg-1 ) both decreased by about 33.33% in comparison with captopril. CONCLUSION: A new difunctional (antioxidant and hypotensive) peptide, WVRQAPGKGL, derived from porcine plasma hydrolyzate was isolated by gel filtration and reverse phase chromatography, and identified by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS)-1 . The difunctional peptide WVRQAPGKGL from porcine plasma could therefore be used in formulating functional foods or pharmaceuticals. © 2022 Society of Chemical Industry.

Enhanced fresh-keeping capacity of printed surimi by Ca2+-nano starch-lutein and its nondestructive freshness monitoring based on 4D printed anthocyanin.

To solve undiscernible freshness changes of printed functional surimi while maintaining printed shape, 4D printable color-changing material were prepared. Firstly, based on results of printing properties and fresh-keeping of Ca2+-NS-L-surimi, it showed better printing effects (enhanced mechanical strength) and good preservation (inhibition of amino acids decomposition, bacterial growth). However, freshness changes of printed Ca2+-NS-L-surimi were not distinguished directly. To avoid that, 4D printable color-changing material-anthocyanin-hydroxypropyl methyl cellulose-xanthan gum-carrageenan (AHXK) was prepared for indicating freshness through discoloration. Printing results showed AHX with 5 % K had the most suitable mechanical strength (appropriate gel strength, texture, rheology) for printing. Based on that, AHXK had stable color (ΔE fluctuation <5) and was sensitive to pH and ammonia (obvious discoloration; ΔE > 10). Actual freshness monitoring results (co-printing of AHXK-surimi) exhibited significant discolorations, especially for HXK with 0.75 % A. It became green during refrigeration of 3-5 d (keeping fresh, ΔE < 4), brighter green at 7 d (decreased freshness, ΔE > 6), turned yellow at 9 d (spoilage, ΔE > 16), which were distinguished significantly with naked eyes rather than traditional freshness determining. In conclusion, printed AHXK-functional surimi exhibited good printing, preservation and nondestructive freshness monitoring, facilitating application of 3D printed functional surimi.

Identification of a novel hypotensive peptide from porcine plasma hydrolysate by in vitro digestion and rat model.

We separated a novel functional peptide IFPPKPKDTL from porcine plasma hydrolysate by chromatography, HPLC, and identified by Q Exactive LC-MS/MS. Results showed that IFPPKPKDTL had a significant ability of ACE inhibition (76.6%) likely due to the presence of hydrophobic, aromatic, and acidic amino acids that can inactivate ACE by binding Zn2+, providing a hydrogen atom to maintain the link between ACE and the peptide. Furthermore, the ACE inhibition of synthetic IFPPKPKDTL was improved by 15.6% after in vitro digestion. Additionally, the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats gavaged by the peptide (30 mg/kg). Thereby, ACE inhibitory peptide IFPPKPKDTL from porcine plasma was stable and has potential functional value.

Identification of novel antioxidant peptide from porcine plasma hydrolysate and its effect in in vitro digestion/HepG2 cells model.

A novel antioxidant peptide EDEQKFWGK from porcine plasma hydrolysate (PPH) was separated by chromatography, HPLC, and identified by LC-MS/MS. Results showed that EDEQKFWGK had better antioxidant ability (Hydroxyl RAS 32.19%, ABTS RAS 92.93% and DPPH RAS 26.76%) compared with glutathione (30.11%, 82.01%, 26.44%) due to the presence of hydrophobic, aromatic acids (F, W) and acidic amino acids (E, D), decreasing ROS by providing hydrogen atom and chelating metal ions. Furthermore, the antioxidant properties of synthetic EDEQKFWGK still significant despite in vitro digestion because of the production of smaller active peptide. Additionally, it could increase SOD, CAT, GSH-Px to resist oxidative damage in HepG2 cells by inhibiting ROS (O2- , OH·), forming complexes to prevent OH· from destroying DNA and binding to ARE to promote antioxidase expression. Thereby, the novel peptide EDEQKFWGK from porcine plasma had much stable antioxidant properties and hade great potential in formulating functional foods. PRACTICAL APPLICATIONS: This research isolated a novel antioxidant peptide. Moreover, the antioxidant effects of peptide were confirmed under the in vitro digestion model and oxidative damage HepG2 cells model. The results showed the antioxidant peptide could play better effect after digestion and protect the cells from oxidative damage. These data could expand the sequence data of antioxidant peptides and promote the high-value utilization of PPH.

Determination of the iron bioavailability, conformation, and rheology of iron-binding proteins from Tegillarca granosa.

The increased interest in achieving, solely through diet, the same effect on iron levels with supplementation, leads to numerous studies on iron absorption of iron binding proteins (IBPs). The characteristics of IBPs from Tegillarca granosa (T. granosa) and its iron utilization were determined to analyze their relationship. The results showed in T. granosa, Fe(ӀӀ) was main iron form in hemoglobin (TH) and that Fe(ӀӀ) and Fe(ӀӀӀ) coexisted in ferritin (TF). After in vitro digestion, TH was easier to be digested than TF, bovine hemoglobin, and bovine ferritin. In caco-2 cells model, iron bioavailability of TH also was the best, which related to TH's superior fluid properties, higher ratios of α-helix to ß-sheet and amide I to amide II. These suggest TH could be used as a good source of organic iron and provide references for application of T. granosa in human nutrition. PRACTICAL APPLICATIONS: This research investigated the iron bioavailability and structural properties of iron-binding proteins from Tegillarca granosa (T. granosa). Moreover, the effects of iron absorption in bovine hemoglobin and ferritin were compared with those from T. granosa. The results showed the hemoglobin in T. granosa had better iron bioavailability and it could be a good source of iron. These data could provide a basic instruction of the application of T. granosa in functional food production.