Rapeseed peptide inhibits HepG2 cell proliferation by regulating the mitochondrial and P53 signaling pathways.

BACKGROUND: Rapeseed peptide, extracted from rapeseed protein, is known to have a variety of biological activities. In this study, the anti-proliferation effect and molecular mechanism of rapeseed peptide on HepG2 cells were investigated. RESULTS: In vitro anticancer experiments showed that the rapeseed peptide NDGNQPL could inhibit HepG2 cell proliferation in a concentration-dependent manner [half maximal inhibitory concentration (IC50 ), 1.56 mmol L-1 ). HepG2 cells were induced by NDGNQPL at a 0.5 mmol L-1 concentration and exhibited a 28.39 ± 0.80% apoptosis rate and a cell cycle arrest in the G0/G1 phase. Meanwhile, rapeseed peptide induced a decrease in mitochondrial membrane potential, an increase in reactive oxygen species (ROS) release, and changes in the nuclear morphology of HepG2 cells, indicating that rapeseed peptide could induce cell apoptosis through the mitochondrial pathway. In addition, rapeseed peptide activated the proliferation-related P53 signaling pathway, in which the expression levels of P53, P21, and cleaved-caspase3 were up-regulated, while the expression levels of murine double minute 2 (MDM2) were down-regulated. In molecular docking simulations, NDGNQPL exhibited a good affinity for the MDM2 molecule, which supported the notion that the rapeseed peptide is able to inhibit MDM2, a negative regulator of P53. CONCLUSION: The current results indicate that the rapeseed-derived NDGNQPL peptide has the potential to inhibit the proliferation of HepG2 cells and promote human health. © 2022 Society of Chemical Industry.

Enzyme-catalyzed acylation improves gel properties of rapeseed protein isolate.

BACKGROUND: Although rapeseed protein isolate (RPI) possessed some good functional properties, the use of RPI as an ingredient in the food industry is restricted mainly due to its inferior gelation. The purpose of this study was to improve the heat-induced gel properties of RPI using double processes of acylation and additional transglutaminase catalysis. RESULTS: Scanning electron microscopy showed that the gel formed by native RPI exhibited randomly aggregated particulate network structures whereas transglutaminase (TG)-assisted RPI gels significantly improved gelation properties. More importantly, the combined modifications of RPI using TG-assisted acylation can form a gel with unique percolating and small porous structure. Furthermore, TG-catalyzed 5% acylated RPI gel (100 U g-1 , protein basis) exhibited excellent gel properties in terms of gel strength, thermal stability, surface roughness and apparent viscosity compared to non-treated or single modification of RPI gel as determined by texture analyzer, atomic force microscopy and rheometer. Mechanistically, Fourier-transform infrared spectra and gel dissociation test revealed that TG-catalyzed acylation extensively unfolded the hydrophobic and sulfhydryl residues of RPI, in turn, reinforced re-assembly of protein molecules via hydrophobic interactions and disulfide bonds during gel formation. CONCLUSION: Combined processes of acylation and additional TG catalysis improved the thermal gelation properties by altering inter- and intra-protein structures. Such sequential processes will provide a promising approach to improve the protein gelation that could be potentially applied in the food industry. © 2020 Society of Chemical Industry.

Effect of static-state fermentation on volatile composition in rapeseed meal.

BACKGROUND: Fermented rapeseed meal has been used as an alternative protein source for animal feed, but the volatile compounds and how their contents change during fermentation have not been reported. To clarify the effect of static-state fermentation on its aroma, the volatile compounds of rapeseed meal during different stages of fermentation were analyzed using an electronic nose system and headspace solid-phase microextraction-gas chromatography-mass spectrometry. RESULTS: The results suggested that the volatile compounds in the raw rapeseed meal, mostly hydrocarbons and some aldehydes, were lost. The levels of the volatile compounds resulting from microbial metabolism, especially pyrazines, greatly increased during fermentation. Nonanal was the dominant volatile measured in the headspace of raw rapeseed meal. However, the volatile compounds found at high concentrations in rapeseed meal after 5 days of fermentation were tetramethylpyrazine, followed by butanoic acid, benzenepropanenitrile, 2-methylbutanoic acid, trimethylamine, 2,3,5-trimethyl-6-ethylpyrazine, and 2,3,5-trimethylpyrazine. CONCLUSION: The fermentation process could significantly change the composition and content of volatile compounds in rapeseed meal. The results may provide reference data for studies on the choice of fermentation period and formation mechanism of flavor substances in fermented rapeseed meal. © 2020 Society of Chemical Industry.

Storage characteristics of infrared radiation stabilized rice bran and its shelf-life evaluation by prediction modeling.

BACKGROUND: Rice bran is a nutrient-dense and resource-rich byproduct produced from the rice milling. The limitation of rice bran utilization is mainly caused by oxidative deterioration. Improvement of stability to prolong rice bran shelf-life has thus become an urgent requirement. RESULTS: The present study aimed to determine the characteristics of infrared radiation heat treatment of rice bran (IRRB) and raw rice bran stored under different temperatures. The effects of heating and storage time on physicochemical, microbial, storage stability and structural properties were investigated. Additionally, the prediction model for the shelf-life of rice bran was established based on free fatty acids and the peroxide value by fitting the curve of bran lipid oxidation. The results obtained demonstrated that infrared radiation heating at 300 °C for 210 s resulted in decreased lipase activity and peroxidase activity of 73.05% and 81.50%, respectively. The free fatty acids and peroxide value of IRRB stored at 4 and 25 °C for 8 weeks were only reached at 2.35% and 3.17% and 2.53 and 3.64 meq kg-1 , respectively. The shelf-life prediction model showed the the shelf-life of infrared radiation-treated samples increased to 71.6 and 25.8 weeks under storage at 4 and 25 °C, respectively. CONCLUSION: The stabilizing process could effectively suppress microbial growth and had no prominent effect on the physicochemical and microstructure properties of rice bran and, simultaneously, storage life was greatly extended. © 2020 Society of Chemical Industry.

Characterization and analysis of an oil-in-water emulsion stabilized by rapeseed protein isolate under pH and ionic stress.

BACKGROUND: Presently, identifying natural compounds as emulsifiers is a popular topic in the food industry. Rapeseed protein isolate (RPI) is a natural plant protein with excellent emulsifying properties, but it has not been systematically developed and utilized. RESULTS: This study investigated the surface hydrophobicity, wettability, and protein solubility of RPI to further explain its emulsifying behavior in emulsion systems. Nanoemulsions stabilized by RPI at varying protein concentration, pH, and ionic strength were prepared. The size distribution, zeta potential, flocculation index, creaming index, microstructure, rheology, and protein secondary structure of emulsions were measured. The emulsion stabilized by 20 g L-1 RPI at pH 10.0, 200 mmol L-1 ionic strength revealed an appropriate droplet size of 555 nm and the most internal gel strength without creaming phenomenon. Circular dichroism spectroscopy showed a positive correlation between emulsion stability and α-helix ratio, indicating the environment factors affected emulsion stability by acting on its hydrogen bonds. CONCLUSIONS: This study demonstrates that RPI is a practical emulsifier for stabilizing nanoemulsions. About 20 g L-1 RPI can stabilize 100 mL L-1 oil in water; stable emulsions can be formed at most pH conditions (except 7.0); ion addition will aggravate the emulsion flocculation, but also increase the internal gel strength. © 2020 Society of Chemical Industry.

Production of Bacterial Ghosts from Gram-Positive Pathogen Listeria monocytogenes.

INTRODUCTION: The Gram-positive bacterium Listeria monocytogenes is a ubiquitous intracellular pathogen, which has been implicated within the past decade as the causative organism in several outbreaks of foodborne disease. Bacterial ghosts (BGs) are nonliving and vacant cell envelopes of bacteria generated by releasing the bacterial cytoplasm through a channel in the cell envelope. This study attempted to produce Gram-positive pathogenic L. monocytogenes ghosts (LMGs) with simple chemicals. MATERIALS AND METHODS: The generation of LMGs was based on minimum inhibition concentrations of 1.10 mg/mL NaOH, 0.0675 mg/mL SDS, and 0.035% (v/v) H2O2. The potential efficacy of LMGs as vaccines and their ability to induce protective immune responses against virulent L. monocytogenes challenge through multipoint subcutaneous injection were also evaluated. RESULTS: The detected activity and viability of LMGs showed that nonliving LMGs could be induced. The detected LMG DNA and protein, as well as its morphological features, indicated that the produced LMGs were empty cells with the correct morphological structure. The subcutaneous vaccination of LMGs through multipoint injection conferred effective protection, with an antibody titer that reached 104 U. CONCLUSIONS: These findings strongly suggested that this chemical method can be used to produce LMGs and could be useful in future vaccine development against this foodborne pathogen.

Phenotypic and Genotypic Alterations of Durancin GL-Resistant Enterococcus durans Strains.

The emergence and spread of bacteriocin-resistant bacteria threaten the efficiency of bacteriocin usage as food preservatives. In this experiment, 19 selected Enterococcus durans strains acquired resistance after exposure to durancin GL, and the mutants had similar intermediate levels of resistance. One wild-type E. durans KLDS 6.0603 and its two resistant mutants, E. durans KLDS 6.0603-2 and E. durans KLDS 6.0603-3, were used to characterize phenotypic and genotypic differences. Approximately 100 µg/mL of durancin GL can penetrate the cytoplasmic membrane of E. durans KLDS 6.0603, causing damage to bacterial cells, but cannot penetrate E. durans KLDS 6.0603-2 and KLDS 6.0603-3 membranes. Unsaturated fatty acid content in resistant strains was significantly increased compared with wild-type strains, indicating that the former has more fluidity of cell membrane than the latter. Decreased mannose phosphotransferase system gene expression (mptD) was observed in the two resistant strains. Results showed that the factors, including the increased unsaturated fatty acid and decreased mptD expression, could contribute to durancin GL resistance.

Enhanced emulsification performance and interfacial properties of Janus-like rapeseed cruciferin through asymmetric acylation modification.

Plant protein emulsifiers, particularly rapeseed protein isolate with its superior amino acid composition and predominantly globular protein, have captured significant interest in the food industry. Nonetheless, the application of these proteins has been stymied by their lackluster emulsification properties. Addressing this challenge, our study implements an innovative asymmetric acylation technique to modify the surface of rapeseed cruciferin (RC), morphing it into a structure resembling Janus nanoparticles. This alteration amplifies the emulsification prowess of RC by a remarkable 2.7 times compared to its natural form, and 1.43 times over its conventionally acylated counterpart. The asymmetrically acylated RC, marked by a distinctive three-phase contact angle of 90.4°, manifests an outstanding amphiphilic character. Moreover, it surpasses both the natural and conventionally acylated RC in terms of diffusion, penetration, and rearrangement rates, as well as protein concentration at the oil-water interface. Compared to commonly used emulsifiers in the food industry, such as lecithin and soy protein, the asymmetrically acylated RC stands out, stabilizing emulsions with the tiniest particle size and effectively staving off emulsion stratification over a longer duration. This study underscores that asymmetric acylation serves as a reliable methodology for producing efficient plant protein emulsifiers, considerably amplifying their utility in the food industry.

Inhibitory Effects of Royal Jelly and Its Functional Components on the Proliferation of MKN-28 Gastric Cancer Cells.

Royal jelly (RJ) is a natural food product with nutritional value and anticancer activity. However, their effects on gastric cancer are unclear. Here, we show that treatment with 5-320 µg/mL of RJ, ethanol extract (RJEE), and protein hydrolyzate (RJPH) decreased the viability of MKN-28 gastric cancer cells, with a half-maximal inhibitory concentration of 123.22 µg/mL for RJEE. RJ, RJEE, and RJPH increase the lactate dehydrogenase release rate and change the morphology of the cells, resulting in cell shrinkage, nucleoplasm condensation, and the formation of apoptotic bodies. RJ and its functional components stagnated the cell cycle in the G0/G1 phase, accompanied by the accumulation of reactive oxygen species, decreased mitochondrial membrane potential, and increased expression levels of p53 and p21 proteins, caspase-3 activation, and apoptosis. Therefore, RJ, RJEE, and RJPH have potential inhibitory effects on the proliferation of gastric cancer cells.

Co-encapsulation of rutinoside and ß-carotene in liposomes modified by rhamnolipid: Antioxidant activity, antibacterial activity, storage stability, and in vitro gastrointestinal digestion.

The surfactant rhamnolipid (RL) was used to modify the liposomes. ß-carotene (ßC) and rutinoside (Rts) were utilized to generate co-encapsulated liposomes through an ethanol injection method that used both hydrophilic and hydrophobic cavities to fabricate a novel cholesterol-free composite delivery system. The RL complex-liposomes loaded with ßC and Rts (RL-ßC-Rts) showed higher loading efficiency and good physicochemical properties (size = 167.48 nm, zeta-potential = -5.71 mV, and polydispersity index = 0.23). Compared with other samples, the RL-ßC-Rts showed better antioxidant activities and antibacterial ability. Moreover, dependable stability was uncovered in RL-ßC-Rts with still 85.2% of ßC storage from nanoliposome after 30 days at 4°C. Furthermore, in simulated gastrointestinal digestion, ßC exhibited good release kinetic properties. The present study demonstrated that liposomes constructed from RLs offer a promising avenue for the design of multicomponent nutrient delivery systems using both hydrophilic.

Anti-Inflammatory and Transepithelial Transport Activities of Rapeseed (Brassica napus) Napin-Derived Dipeptide Thr-Leu in Caco-2 and RAW264.7 Cocultures.

This study aimed to investigate the anti-inflammatory molecular activity of rapeseed napin-derived dipeptide Thr-Leu (TL) using Caco-2/RAW264.7 cell cocultures. This in vitro coculture intestinal inflammation model was used to assess the absorption, evolution, and anti-inflammatory effects of peptides. TL was absorbed by the intestinal epithelial cells with an apparent permeability of (2.48 ± 0.18) × 10-6 cm/s, primarily through the PepT1 pathway. TL treatment exerted anti-inflammatory and restorative effects on the impaired intestinal barrier function by enhancing the expression levels of occludin and ZO-1 in lipopolysaccharide (LPS)-induced Caco-2 cells. No significant change (P < 0.05) was detected in claudin-1 expression levels; however, the occludin expression levels were upregulated through the protein kinase C (PKC) signaling pathway. Compared with the LPS-induced group, TL (2.0 mM) reduced the levels of intracellular inflammation-related enzymes (iNOS: by 50.84%; COX-2: by 49.64%) on the coculture cell model. In addition, the interleukin (IL)-1ß, IL-6, and TNF-α levels in RAW264.7 cells were significantly (P < 0.05) downregulated following TL treatment (2.0 mM) due to the suppression of the phosphorylation of the JNK-independent pathway on the basolateral side of the coculture cell model. These findings highlight the potential use of TL in functional foods or nutraceuticals to prevent intestinal inflammation.

Impact of exopolysaccharides-producing lactic acid bacteria on the chemical, rheological properties of buckwheat sourdough and the quality of buckwheat bread.

Exopolysaccharides (EPS) produced in situ by lactic acid bacteria (LAB) during sourdough fermentation have the potential to replace hydrocolloids in gluten-free sourdoughs. This study investigated effects of an EPS-producing Weissella cibaria NC516.11 fermentation on chemical, rheological properties of sourdough and the quality of buckwheat bread. Results indicate that the buckwheat sourdough fermentation by W. cibaria NC516.11 had lower pH (4.47) and higher total titrable acidity (8.36 mL) compared with other groups, and the polysaccharide content reached 3.10 ± 0.16 g/kg. W. cibaria NC516.11 can significantly improve the rheological properties and viscoelastic properties of sourdough. Compared with control group, the baking loss of NC516.11 group bread decreased by 19.94%, specific volume increased by 26.03%, and showed good appearance and cross-sectional morphology. Scanning electron micrograph revealed an intact and less porous cell structure. Meanwhile, W. cibaria NC516.11 significantly improved the texture of the bread and reduced the hardness and moisture loss during storage.

Study on the hypolipidemic activity of rapeseed protein-derived peptides.

Hyperlipidaemia, a common chronic disease, is the cause of cardiovascular diseases such as myocardial infarction and atherosclerosis. Generally, drugs for lowering blood lipids have disadvantages such as short or poor efficacy, high toxicity, and side effects. Rapeseed active peptides are excellent substitutes for lipid-lowering drugs because of their high biological safety, strong penetration, and easy absorption by the human body. This study separated and purified the rapeseed peptides using gel chromatography and mass spectrometry. Rapeseed peptides amino acid sequences were determined to obtain Glu-Phe-Leu-Glu-Leu-Leu (EFLELL) peptides with good hypolipidaemic activity and IC50 values of 0.1973 ± 0.05 mM (sodium taurocholate), 0.375 ± 0.03 mM (sodium cholate), and 0.203 ± 0.06 mM (sodium glycine cholate). The EFLELL hypolipidaemic activity was evaluated, and its mechanism of action was investigated using cell lines. Rapeseed peptide treatment significantly decreased the total cholesterol (T-CHO), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels, and the protein and gene expression levels of proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein cholesterol (LDLR) suggested the mechanism. Molecular docking revealed that the binding energy between rapeseed peptide and LDLR-PCSK9 molecules was -6.3 kcal/mol and -8.1 kcal/mol. In conclusion, the rapeseed peptide EFLELL exerts a favourable hypolipidaemic effect by modulating the LDLR-PCSK9 signalling pathway.

Protective effect of polyphenols extract of adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) on hypercholesterolemia-induced oxidative stress in rats.

The present study examines the effect of polyphenols extract of adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) (APE) on high cholesterol diet fed rats (HCD). APE was orally administrated by gavage at doses of 10, 40 and 200 mg total phenolics/kg body weight of rats once a day for 28 days. At the end of four weeks, serum triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C), and markers of oxidative stress viz., malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the serum and liver of HCD and normal rats were assessed and compared. The results showed that administration of APE was significantly effective in decreasing the serum levels of TC, LDL-C and MDA, increasing the serum level of HDL-C and antioxidant capacity. In addition, oral gavage of APE could also increase the antioxidant capacity, CAT and GSH-Px activities in liver. These results suggested that APE exerted a high hypocholesterolemic and antioxidant activities, which might be characterized by a protective effect on cardiovascular health in vivo.

Synergistic growth-inhibition effect of quercetin and N-Acetyl-L-cysteine against HepG2 cells relying on the improvement of quercetin stability.

In this study, N-Acetyl-l-cysteine (NAC) as a widely-used antioxidant was first applied to improve the stability of Que in medium. The stability of Que in medium was analyzed, and the growth-inhibition effect of Que and NAC against HepG2 cells was estimated. The results showed NAC could significantly improve the stability of Que in medium (more than 80%), while Que alone in medium was totally degraded within 4 h. Besides, it was found that Que together with NAC could significantly enhance the growth-inhibition effect against HepG2 cells compared with Que alone, with the IC50 value of 40 µM and 200 µM for Que together with NAC and Que alone. Moreover, NAC could inhibit the depletion of GSH induced by Que. The synergistic growth-inhibition effect of Que and NAC against HepG2 cells was attributed to NAC improving Que stability in medium accompanied by NAC inhibiting the depletion of GSH induced by Que. The results showed that NAC could improve the stability of Que and reduce the degradation rate of Que in culture medium. This study can provide a reference for the further study of the mechanism of NAC enhancing the stability of quercetin and the development of broad-spectrum stabilizers.

Anti-inflammatory activity of peptides derived from millet bran in vitro and in vivo.

Various food-derived bioactive peptides have been found with potential anti-inflammatory effects. Millet bran peptide is a food-derived bioactive peptide extracted from millet bran, a by-product of millet processing. In this study, the anti-inflammatory effect of millet bran peptides was investigated. A lipopolysaccharide (LPS)-induced RAW264.7 cell and an animal experiment model were established to test the anti-inflammatory activity of millet bran peptides in vitro. As indicated by the results, millet bran peptides could significantly reduce the levels of inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and prostaglandin E2 (PGE2), in the LPS-induced RAW264.7 cell. As demonstrated by the animal experiment results, millet bran peptides could mitigate the inflammation of spontaneously hypertensive rats (SHRs). According to the western blotting results, millet bran peptides reduced the phosphorylation level of an extracellular signal-related kinase (ERK), I Kappa B (IKB), p65, and p38 of LPS-induced RAW264.7 cells. As indicated by 16S rDNA sequencing analysis results, millet bran peptides could modify the composition of intestinal microbes. In brief, millet bran peptides could have anti-inflammatory activities in vivo and in vitro and mitigate the inflammation of LPS-induced RAW264.7 cells by regulating the signaling pathways of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK). The above research has laid a theoretical basis for the application of plant-derived peptides in health food.

Removal of anti-nutritional factors of rapeseed protein isolate (RPI) and toxicity assessment of RPI.

We prepared a detoxified rapeseed protein isolate (RPI) by phytase/ethanol treatment based on alkaline extraction and acidic precipitation. Contents of protein, fat, ash, moisture, crude fiber, glucosinolates, phytic acid, and phenolics and color were determined. To evaluate the safety of detoxified RPI, five groups of C57 mice (detoxified RPI [10 and 20 g kg-1]; commercial soybean protein isolate (SPI) [10 g kg-1]; non-detoxified RPI [10 g kg-1]; control) were used in the acute-toxicity test. Bodyweight and pathology parameters were recorded at different time points, followed by macroscopic examination, organ-weight measurement and microstructure examination. After pretreatment of rapeseed meals with phytase (enzyme : substrate ratio, 1 : 5 mg g-1) for 1.5 h and two-time ethanol extraction for precipitated protein, the chemical characteristics in RPI were protein (88.26%), fat (0.57%), ash (2.72%), moisture (1.90%), crude fiber (0.77%), glucosinolates (0 µmol g-1), phytic acid (0.17%), phenolics (0.36%) and whiteness (73.38). Treatment resulted in significant removal of anti-nutritional factors (ANFs) and increased whiteness in detoxified RPI compared with non-detoxified RPI, and lower than in cruciferin-rich canola protein isolate (Puratein®). Experimental-related effects on bodyweight, clinical observations, or clinicopathology, in mice treated with detoxified RPI were not observed except for a decreased thyroid gland/parathyroid gland index in mice treated with non-detoxified RPI. Furthermore, the no-observed-effect level (NOEL) was 10 g kg-1 of detoxified RPI, whereas the no-observed-adverse-effect-level (NOAEL) was the highest fed level of 20 g kg-1 of detoxified RPI. Overall, detoxified RPI prepared by the combined treatment of phytase and ethanol was considered safe under the conditions tested, in which the contents of the main ANFs were reduced significantly.

Assessment of Novel Oligopeptides from Rapeseed Napin (Brassica napus) in Protecting HepG2 Cells from Insulin Resistance and Oxidative Stress.

Oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Pro-Leu-Lys (HPLK), Leu-Pro-Lys (LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)) are newly identified from rapeseed napin (Brassica napus) protein-derived hydrolysates with the capability of upregulating glucose transporter-4 (GLUT4) expression and translocation. However, whether each of them enhances GLUT4 expression and translocation and their specific mechanisms remain unclear. Here, we assess the effects of the oligopeptides against insulin resistance (IR) and oxidative stress in hepatocytes and screen out the most antidiabetic one. Specifically, compared with other oligopeptides, LPK not only remarkably elevated glucose consumption to 8.45 mmol/L protein; superoxide dismutase (SOD) activity to 319 U/mg protein; GLUT4 expression and translocation; and phosphorylated level of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) (P < 0.05) but also remarkably attenuated the reactive oxygen species (ROS) level to 2255, lactate dehydrogenase (LDH) activity to 20.5 U/mg protein, malondialdehyde (MDA) content to 241 nmol/mg protein, and NO content to 1302 µmol/mL protein (P < 0.05). These findings demonstrated that antidiabetic oligopeptide LPK possessed the most potential to protect HepG2 cells from IR and oxidative stress via activating IRS-1/PI3K/Akt/GLUT4 and regulating common oxidative markers in vitro.

Screening and identification of high bioavailable oligopeptides from rapeseed napin (Brassica napus) protein-derived hydrolysates via Caco-2/HepG2 co-culture model.

Rapeseed napin (Brassica napus) protein-derived hydrolysates (RNPHs, 1-4) are mixtures of peptides, prior to reaching liver tissue and playing their antidiabetic role, at least being absorbed and metabolized by the intestinal barrier. The study aims at screening and identifying high bioavailable rapessed napin-derived oligopeptides via simulated gastrointestinal digestion and absorption. Specifically, RNPHs were obtained using a novel ultrasound-assisted digestive device. The potential capacity of treating type 2 diabetes mellitus (T2DM) was evaluated preliminarily via enhancing glucose transporter 4 (GLUT4) expression and translocation. Also, absorbable rapeseed napin-derived oligopeptides were screened and identified in a Caco-2/HepG2 co-culture model using liquid chromatography coupled with electrospray ionisation and quadrupole time of flight tandem mass spectrometry (LC-ESI-QTOF-MS). The results involved mainly two aspects. First, absorbable oligopeptides from RNPH-1 (Molecular weight, Mw ≤ 3 kDa) with the highest degree of hydrolysis (DH) were the optimal ones to enhance GLUT4 expression and translocation (P < 0.05). Secondly, oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Leu-Pro-Lys (HLPK), (Ile) Leu-Pro-Lys ((I)LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)), identified from both RNPH-1 and RNPH-2 which significantly enhanced GLUT4 expression and translocation, could be absorbed intact and reached HepG2 cells. These findings indicated that high bioavailable oligopeptides from RNPHs were the potential usefulness to treat T2DM in vitro.

Enhancement of DPP-IV inhibitory activity and the capacity for enabling GLP-1 secretion through RADA16-assisted molecular designed rapeseed peptide nanogels.

The potential of pentapeptide IPQVS (RAP1) and octapeptide ELHQEEPL (RAP2) derived from rapeseed napin as natural dipeptidyl-peptidase IV (DPP-IV) inhibitors is promising. The objective was to develop a nanogel strategy to resist the hydrolysis of digestive and intestinal enzymes to enhance the DPP-IV inhibitory activity of RAP1 and RAP2, and stimulate glucagon-like peptide 1 (GLP-1) secretion of RAP2 by a RADA16-assisted molecular design. The linker of double Gly was used in the connection of RADA16 and the functional oligopeptide region (RAP1 and RAP2). Compared to the original oligopeptides, DPP-IV IC50 of the nanogels RADA16-RAP1 and RADA16-RAP2 decreased by 26.43% and 17.46% in Caco-2 cell monolayers, respectively. The results showed that the two nanogel peptides with no toxicity to cells had higher contents of stable ß-sheet structures (increased by 5.6-fold and 5.2-fold, respectively) than the original oligopeptides, and a self-assembled fibrous morphology. Rheological results suggested that the nanogels RADA16-RAP1 and RADA16-RAP2 exhibit good rheological properties for potential injectable applications; the storage modulus (G') was 10 times higher than the low modulus (G''). Furthermore, the RAP2 and its RADA16-assisted nanogel peptide at the concentration of 250 µM significantly (P < 0.05) increased the release of GLP-1 by 35.46% through the calcium-sensing receptor pathway in the enteroendocrine STC-1 cells. Hence, the innovative and harmless nanogels with the sequence of RADA16-GG-Xn have the potential for use by oral and injection administration for treating or relieving type 2 diabetes.