Comparative study of enzymatic hydrolysis of α/β- and γ-gliadins

Digestion of whey peptide induces antioxidant and anti-inflammatory bioactivity on glial cells: Sequences identification and structural activity analysis

Whey derived peptides have shown potential activity improving brain function in pathological condition. However, there is little information about their mechanism of action on glial cells, which have important immune functions in brain. Astrocytes and microglia are essential in inflammatory and oxidative defense that take place in neurodegenerative disease. In this work we evaluate antioxidant and anti-inflammatory potential bioactivity of whey peptide in glial cells. Peptides were formed during simulated gastrointestinal digestion (Infogest protocol), and low molecular weight (<5kDA) peptides (WPHf) attenuated reactive oxygen species (ROS) production induced by hydrogen peroxide stimulus in both cells in dose-dependent manner. WPHf induced an increase in the antioxidant glutathione (GSH) content and prevented GSH reduction induced by lipopolysaccharides (LPS) stimulus in astrocytes cells in a cell specific form. An increase in cytokine mRNA expression (TNFα and IL6) and nitric oxide secretion induced by LPS was attenuated by WPHf pre-treatment in both cells. The inflammatory pathway was dependent on NFκB activation. Bioactive peptide ranking analysis showed positive correlation with hydrophobicity and negative correlation with high molecular weights. The sequence identification revealed 19 peptides cross-referred with bioactive database. Whey peptides were rich in leucine, valine and tyrosine in the C-terminal region and lysine in the N-terminal region. The anti-inflammatory and antioxidant potential of whey peptides were assessed in glia cells and its mechanisms of action were related, such as modulation of antioxidant enzymes and anti-inflammatory pathways. Features of the peptide structure, such as molecular size, hydrophobicity and types of amino acids present in the terminal region are associated to bioactivity.

Digestion-resistant whey peptides promote antioxidant effect on Caco-2 cells

Enteric endothelial cells are the first structure to come in contact with digested food and may suffer oxidative damage by innumerous exogenous factors. Although peptides derived from whey digestion have presented antioxidant potential, little is known regarding antioxidant pathways activation in Caco-2 cell line model. Hence, we evaluated the ability to form whey peptides resistant to simulated gastrointestinal digestive processes, with potential antioxidant activity on gastrointestinal cells and associated with sequence structure and activity. Using the INFOGEST method of simulated static digestion, we achieved 35.2% proteolysis, with formation of peptides of low molecular mass (<600 Da) evaluated by FPLC. The digestion-resistant peptides showed a high proportion of hydrophobic and acidic amino acids, but with average surface hydrophobicity. We identified 24 peptide sequences, mainly originated from β-lactoglobulin, that exhibit various bioactivities. Structurally, the sequenced peptides predominantly contained the amino acids lysine and valine in the N-terminal region, and tyrosine in the C-terminal region, which are known to exhibit antioxidant properties. The antioxidant activity of the peptide digests was on average twice as potent as that of the protein isolates for the same concentration, as evaluated by ABTS, DPPH and ORAC. Evaluation of biological activity in Caco-2 intestinal cells, stimulated with hydrogen peroxide, showed that they attenuated the production of reactive oxygen species and prevented GSH reduction and SOD activity increase. Caco-2 cells were not responsive to nitric oxide secretion. This study suggests that whey peptides formed during gastric digestion exhibit biological antioxidant activity, without the need for previously hydrolysis with exogenous enzymes for supplement application. The study's primary contribution was demonstrating the antioxidant activity of whey peptides in maintaining the gastrointestinal epithelial cells, potentially preventing oxidative stress that affects the digestive system.

In vitro inhibition of glucose gastro-intestinal enzymes and antioxidant activity of hydrolyzed collagen peptides from different species

The growing value of industrial collagen by-products has given rise to interest in extracting them from different species of animals. Intrinsic protein structure variation of collagen sources and its hydrolysis can bring about different bioactivities. This study aimed to characterize and evaluate the differences in vitro biological potential of commercial bovine (BH), fish (FH), and porcine hydrolysates (PH) regarding their antioxidant and hypoglycemic activities. All samples showed percentages above 90% of protein content, with high levels of amino acids (glycine, proline, and hydroxyproline), responsible for the specific structure of collagen. The BH sample showed a higher degree of hydrolysis (DH) (8.7%) and a higher percentage of smaller than 2 kDa peptides (74.1%). All collagens analyzed in vitro showed inhibition of pancreatic enzymes (α-amylase and α-glucosidase), with the potential to prevent diabetes mellitus. The PH sample showed higher antioxidant activities measured by ORAC (67.08 ± 4.23 μmol Trolox Eq./g) and ABTS radical scavenging (65.69 ± 3.53 μmol Trolox Eq./g) methods. For the first time, DNA protection was analyzed to hydrolyzed collagen peptides, and the FH sample showed a protective antioxidant action to supercoiled DNA both in the presence (39.51%) and in the absence (96.36%) of AAPH (reagent 2,2'-azobis(2-amidinopropane)). The results confirmed that the source of native collagen reflects on the bioactivity of hydrolyzed collagen peptides, probably due to its amino acid composition. PRACTICAL APPLICATIONS: Our data provide new application for collagen hydrolysates with hypoglycemiant and antioxidant activity. These data open discussion for future studies on the additional benefits arising from collagen peptide consumption for the prevention of aging complications or hyperglycemic conditions as observed in chronic diseases such as diabetes mellitus type II (DM 2). The confirmation of these results can open new market areas for the use of collagen with pharmacological applications or to produce new supplements. Furthermore, provides a solution for waste collagen from meat industries and adds value to the product.

Ultrafiltration to fractionate wheat polypeptides

An ultrafiltration process allowing the fractionation of two kinds of polypeptides issued from limited chymotryptic hydrolysis of wheat gliadins was applied to wheat gluten hydrolysates. Hydrophilic and poorly charged polypeptides were well transmitted through an inorganic ZrO2-based membrane at acidic pH, whereas hydrophobic and positively charged polypeptides were highly retained. By combining reversed-phase and cation-exchange chromatography (CEC), it was proved that the fractionation of the polypeptides was based on electrostatic repulsion of the charged polypeptides by the positively charged membrane. After a continuous diafiltration process, retentates containing 75 to 88% of hydrophobic polypeptide and permeates containing 84 to 90% of hydrophilic polypeptides were recovered, depending on the size of membrane used. Even if the ultrafiltration fractions were less purified than fractions issued from CEC, it was shown that they exhibited very different foaming properties: permeate did not produce nor stabilize foams, whereas retentate was more efficient than the whole hydrolysates and BSA.