Non-gastrointestinal-hydrolysis enhances bioavailability and antioxidant efficacy of casein as compared with its in vitro gastrointestinal digest

Screening of Novel Bioactive Peptides from Goat Casein: In Silico to In Vitro Validation

Food-derived bioactive peptides are of great interest to science and industry due to evolving drivers of food product innovation, including health and wellness. This study aims to draw attention through a critical study on how bioinformatics analysis is employed in the identification of bioactive peptides in the laboratory. An in silico analysis (PeptideRanker, BIOPEP, AHTpin, and mAHTPred) of a list of peptides from goat casein hydrolysate was performed to predict which sequences could potentially be bioactive. To validate the predictions, the in vitro antihypertensive potential of the five peptides with the highest potential was first measured. Then, for three of these, gastrointestinal digestion was simulated in vitro, followed by the analysis of the resulting ACE inhibitory activity as well as antioxidant capacity. We thus observed that the use of new computational biology technologies to predict peptide sequences is an important research tool, but they should not be used alone and complementarity with various in vitro and in vivo assays is essential.

Measuring the oral bioavailability of protein hydrolysates derived from food sources: A critical review of current bioassays

BACKGROUND

Food proteins are a source of hydrolysates with potentially useful biological attributes. Bioactive peptides from food-derived proteins are released from hydrolysates using exogenous industrial processes or endogenous intestinal enzymes. Current in vitro permeability assays have limitations in predicting the oral bioavailability (BA) of bioactive peptides in humans. There are also difficulties in relating the low blood levels of food-derived bioactive peptides detected in preclinical in vivo models to pharmacodynamic read-outs relevant for humans.

SCOPE AND APPROACH

In this review, we describe in vitro assays of digestion, permeation, and metabolism as indirect predictors of the potential oral BA of hydrolysates and their constituent bioactive peptides. We discuss the relationship between industrial hydrolysis processes and the oral BA of hydrolysates and their peptide by-products.

KEY FINDINGS

Hydrolysates are challenging for analytical detection methods due to capacity for enzymatic generation of peptides with novel sequences and also new modifications of these peptides during digestion. Mass spectrometry and peptidomics can improve the capacity to detect individual peptides released from complex hydrolysates in biological milieu.

Potential applications of ficin in the production of traditional cheeses and protein hydrolysates

Using proteolytic enzymes extracted from plant materials is a promising way to ensure the sustainability of the food industry. This is particularly true for the dairy industry, especially in cheesemaking and the production of different milk protein hydrolysates for special food applications, particularly nutrition for infants, older adults, and people with food allergies. Ficin, a cysteyl protease isolated from the latex of the fig tree (Ficus carica), is characterized by strong enzymatic activity and can be used for milk clotting and protein hydrolysis for application in different foods. In particular, it can be used for milk protein hydrolysis to produce ingredients with reduced or eliminated allergenicity and improved bioavailability. Ficin can also be used as an active and effective replacement for calf rennet in cheesemaking, such as in traditional Cacioricotta and Teleme cheeses. It can also be used to produce protein hydrolysates with low or no allergenicity for application in infant formula and geriatric nutrition. This work provides an overview of ficin, a plant-derived protease, with an emphasis on its potential application in the production of some traditional cheeses and milk protein hydrolysates for special food applications.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Gastrointestinal Digestion of Food Proteins under the Effects of Released Bioactive Peptides on Digestive Health

The gastrointestinal tract represents a specialized interface between the organism and the external environment. Because of its direct contact with lumen substances, the modulation of digestive functions by dietary substances is supported by a growing body of evidence. Food-derived bioactive peptides have demonstrated a plethora of activities in the organism with increasing interest toward their impact over the digestive system and related physiological effects. This review updates the biological effects of food proteins, specifically milk and soybean proteins, associated to gastrointestinal health and highlights the study of digestion products and released peptides, the identification of the active form/s, and the evaluation of the mechanisms of action underlying their relationship with the digestive cells and receptors. The approach toward the modifications that food proteins and peptides undergo during gastrointestinal digestion and their bioavailability is a crucial step for current investigations on the field. The recent literature on the regulation of digestive functions by peptides has been mostly considered in terms of their influence on gastrointestinal motility and signaling, oxidative damage and inflammation, and malignant cellular proliferation. A final section regarding the actual challenges and future perspectives in this scientific topic is critically discussed.

The in vitro bioavailability of anti-platelet peptides in collagen hydrolysate from silver carp (Hypophthalmichthys molitrix) skin

Previous animal experiments indicated collagen hydrolysates (CHs) intake decreased platelet release indicators in plasma and highlight potential applications as healthcare supplements to combat cardiovascular disease. The oligopeptides (GPR, GPRG, and GPRGP) have anti-platelet activities. However, it is still unclear whether they are bioactive compounds in CHs from silver carp skin. We investigated the bioavailability of oligopeptides using simulated gastrointestinal digestion and Caco-2 model. Anti-thrombotic activities, in vitro platelet aggregation and formation of platelet thrombus, were evaluated. They resisted gastrointestinal digestion and could be absorbed by Caco-2. Oligopeptides inhibited platelet aggregation induced by adenosine diphosphate and thrombin with IC₅₀ of 0.160, 0.283, 0.251 mg/ml and 0.714, 1.008, 0.917 mg/ml for GPR, GPRG, and GPRGP, respectively. Oligopeptides prolonged the time of platelet thrombus and inhibited coagulation cascades, but CHs performed no bleeding side effect. These results confirmed that oligopeptides could be used as bioactive compounds of dietary supplements for pre-thrombotic to prevent thrombosis. PRACTICAL APPLICATIONS: Oligopeptides, GPR, GPRG, and GPRGP, derived from silver carp (Hypophthalmichthys molitrix) skin collagen, performed anti-thrombotic activities from their anti-platelet aggregation and anticoagulation activities. But the collagen hydrolysates containing these peptides had no side effect of bleeding in the mice model. Furthermore, this study investigated the bioavailability of these three bioactive peptides by the Caco-2 cells model. Thus, oligopeptides GPR, GPRG, and GPRGP are a potential index of bioactive compounds in the preparation of anti-thrombotic functional foods or healthcare supplements for people at the pre-thrombotic state.

Characterization, evaluation of nutritional parameters of Radix isatidis protein and its antioxidant activity in D-galactose induced ageing mice

BACKGROUND

Radix isatidis (Isatis indigotica Fort.) is an ancient medicinal herb, which has been applied to the prevention and treatment of influenza virus since ancient times. In recent years, the antioxidant activity of Radix isatidis has been widely concerned by researchers. Our previous studies have shown that Radix isatidis protein (RIP) has good antioxidant activity in vitro. In this study, the composition of the protein was characterized and its antioxidant activity in vivo was evaluated.

METHODS

The model of oxidative damage in mice was established by subcutaneous injection of D-galactose for 7 weeks. Commercially available kits were used to determine the content of protein and several oxidation indexes in different tissues of mice. The tissue samples were stained with hematoxylin and eosin (H&E) and the pathological changes were observed by optical microscope. The molecular weight of RIP was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The amino acid composition of RIP was determined by a non-derivative method developed by our research group.

RESULTS

RIP significantly increased the activities of antioxidant enzymes such as SOD, CAT, GSH-Px and total antioxidant capability (TAOC) but decreased the MDA level in the serum, kidney and liver. H&E stained sections of liver and kidney revealed D-galactose could cause serious injury and RIP could substantially attenuate the injury. The analysis of SDS-PAGE showed that four bands with molecular weights of 19.2 kDa, 21.5 kDa, 24.8 kDa and 40.0 kDa were the main protein components of RIP.

CONCLUSIONS

The results suggested that RIP had excellent antioxidant activity, which could be explored as a health-care product to retard aging and a good source of protein nutrition for human consumption.

Effect of the Plastein Reaction in Presence of Extrinsic Amino Acids on the Protective Activity of Casein Hydrolysate against Ethanol-Induced Damage in HHL-5 Cells

Casein hydrolysates (CH) were prepared using papain and modified by the plastein reaction (CH-P) in the presence of extrinsic phenylalanine (CH-P-Phe) or tryptophan (CH-P-Trp). The in vitro protective activity of CH and its modified products against ethanol-induced damage in HHL-5 cells was investigated. The results showed that the modification by the plastein reaction reduced the amino group content of CH. However, the modification by the plastein reaction in the presence of extrinsic amino acids could enhance the antioxidant, proliferative, cell cycle arresting, and anti-apoptosis activity of CH. Biological activities of CH and its modified products in the HHL-5 cells varied depending on the hydrolysate concentration (1, 2, and 3 mg/mL) and treatment time (24, 48, and 72 h). Generally, higher biological activities were found after cell treatment with CH or its modified products at concentration of 2 mg/mL for 48 h compared to other treatments. In addition, CH modified in the presence of tryptophan (CH-P-Trp) showed higher biological activity than that modified in the presence of phenylalanine (CH-P-Phe). Based on the obtained results, it can be concluded that casein hydrolysates with enhanced biological activity and potential health benefits can be produced by papain and the plastein reaction with the incorporation of extrinsic amino acids.

Charge and hydrophobicity of casein peptides influence transepithelial transport and bioavailability

Antioxidant casein peptides were separated by SP-Sephadex C-25 and C 18 columns. The transepithelial transport and bioavailability including the transport ratio and the remaining ratios of antioxidant activity (RRAA) of these peptide absorbates, were then investigated using a Caco-2 cell monolayer. The results indicate that both the negatively charged peptide fractions (CF1, CF2 and CF3) and the more hydrophilic fraction (HF1) were mainly transported via PepT1 and paracellular routes. The positively charged fractions (CF4 and CF5) and hydrophobic fractions (HF2, HF3 and HF4) were transported via PepT1 and transcytosis. The strongly negatively charged and more hydrophobic fractions showed a higher transport ratio, which ranged from 9.5 to 12.5%; however, the transport ratio of positively charged and hydrophilic fractions ranged from 4.0 to 8.5%. The positively charged and hydrophilic fractions showed a higher RRAA.

Antioxidant potential of buffalo and cow milk Cheddar cheeses to tackle human colon adenocarcinoma (Caco-2) cells

Objective

The aim of present study was to assess the anti-oxidant potential of water-soluble peptides (WSPs) extract derived from buffalo and cow milk Cheddar cheeses at different stages of ripening.

Methods

The antioxidant potential of WSPs extract was assessed through 2,2’-azinobis-3-ethylbenzothiazoline-6sulfonic acid (ABTS)-radical scavenging activity. In addition, impact of WSPs extract on cell viability and production of reactive oxygen species (ROS) in human colon adenocarcinoma Caco-2 (tert-butylhydroperoxide-induced) cell lines was also evaluated.

Results

The ABTS-radical scavenging activity increased progressively with ripening period and dose-dependently in both cheeses. However, peptide extract from buffalo milk Cheddar cheese demonstrated relatively higher activity due to higher contents of water-soluble nitrogen. Intracellular ROS production in Caco-2 cells decreased significantly (p<0.05) till 150th day of cheese ripening and remained constant thereafter. Additionally, dose-dependent response of WSPs extract on antioxidant activity was noticed in the Caco-2 cell line.

Conclusion

On the basis of current in vitro study, the Cheddar cheese WSPs extract can protect intestinal epithelium against oxidative stress due to their antioxidant activity.

Charge properties of peptides derived from casein affect their bioavailability and cytoprotection against H2O2-induced oxidative stress

The effects of charge properties of casein peptides on absorption stability, antioxidant activity, and cytoprotection were evaluated. Alcalase hydrolysates of casein were separated into 4 fractions by cation-exchange chromatography according to charge properties. After simulated digestion and Caco-2 cell transmembrane transport, we determined the total antioxidant capacity (Trolox equivalent antioxidative capacity and oxygen radical antioxidant activity) and nitrogen content of peptide fractions to estimate available antioxidant efficacy and bioavailability (BA) of peptides. Results showed that negatively charged peptide fractions had greater BA and antioxidant activities after digestion and absorption. The peptide permeates were used to test the cytoprotective effect against H2O2-induced oxidative damage in HepG-2 cells. All peptide permeates increased cell viability, elevated catalase activity, and decreased superoxide dismutase activity. However, negatively charged peptide fractions preserved cell viability to a greater degree. Therefore, the negatively charged peptides from casein may be potential antioxidants and could be used as ingredients in functional foods and dietary supplements.