Production of egg yolk phosphopeptides and the cellular mechanism of intestinal oxidative stress reduction
Bibliographic record
Abstract
Oxidative stress in the gastrointestinal tract has been implicated in the initiation and propagation of inflammatory bowel diseases and other chronic intestinal pathologies. Antioxidants have limited efficacy and are sometimes pro-oxidant. An alternative, novel approach lies in the upregulation of endogenous antioxidative stress mechanisms which can combat oxidative stress and re-establish a stable cellular redox balance. Hen egg yolk-derived phosvitin phosphopeptides have been shown to exert this biological activity; however the preparation of these peptides was not suited to large-scale production. The goal of this work was to prepare bioactive peptides from delipidated egg yolk proteins with industry scale-up potential. In addition, the antioxidative stress activity of the peptides was evaluated, the bioactive fraction was identified and characterized, and the cell signaling pathways involved in influencing bioactivity was elucidated. Egg yolk peptides (EYP) were produced by Alcalase and Protease N digestion of defatted egg yolk proteins. This hydrolysate contained 1.00 ± 0.02% phosphate and significantly reduced (P<0.001) the oxidative stress biomarker, interleukin-8 (IL-8), in hydrogen peroxide-stimulated Caco-2 intestinal cells. EYP significantly (P<0.05) increased glutathione (GSH) and [gamma]-glutamylcysteine synthetase activity and mRNA expression, elevated the activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase, glutathione S-transferase), and lowered malondialdehyde and protein carbonyl concentrations in the duodenum, jejunum, ileum, and colon of piglets subjected to oxidative stress. GSH concentrations in red blood cells were also significantly (P<0.05) elevated in EYP-supplemented animals. Anion separation of EYP resulted in 4 fractions with the last fraction, EYP-F4, having 0.72 ± 0.06% phosphate. EYP-F4 significantly decreased (P<0.001) IL-8 in H202-stimulated cells and this bioactivity was maintained after pepsin and pancreatin digestion of EYP-F4 but not after dephosphorylation. Serine and phosphoserine did not reduce oxidative stress, but [Ser(PO3)]2 and [Ser(PO3)]3 significantly reduced (P<0.001) IL-8. Using mass spectrometry analysis, one of the peptides in the EYP bioactive fraction was identified as SKDSSSSSSKSNSK. This identified peptide is found in the phosvitin portion of vitellogenin-1, a yolk precursor protein. These results suggest a minimum of two contiguous phosphoserines in EYP-F4 peptides influence bioactivity. EYP-F4 and [Ser(PO3)]2 cell treatments increased the mRNA expression of antioxidant genes including glutathione reductase and glutathione peroxidase, and lowered the expression of pro-inflammatory genes such as myeloperoxidase and lactoperoxidase in an oxidative stress and antioxidant defense microarray. It is likely that EYP-F4 and [Ser(PO3)]2 increased antioxidant gene expression by activating the nuclear factor-E2-related factor 2-antioxidant response element pathway and decreased inflammatory gene expression by inhibiting the nuclear factor kappa B pathway. Egg yolk phosphopeptides influence the activation of protective antioxidative stress mechanisms which contribute to the prevention of intestinal oxidative stress.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".