A peptidomic analysis of human milk digestion in the infant stomach reveals protein-specific degradation patterns.

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However, it remains unclear to what degree protein degradation occurs in vivo in the infant stomach and whether peptides previously annotated for bioactivity are released. This study combined nanospray LC separation with time-of-flight mass spectrometry, comprehensive structural libraries, and informatics to analyze milk from 3 human mothers and the gastric aspirates from their 4- to 12-d-old postpartum infants. Milk from the mothers contained almost 200 distinct peptides, demonstrating enzymatic degradation of milk proteins beginning either during lactation or between milk collection and feeding. In the gastric samples, 649 milk peptides were identified, demonstrating that digestion continues in the infant stomach. Most peptides in both the intact milk and gastric samples were derived from β-casein. The numbers of peptides from β-casein, lactoferrin, α-lactalbumin, lactadherin, κ-casein, serum albumin, bile salt-associated lipase, and xanthine dehydrogenase/oxidase were significantly higher in the gastric samples than in the milk samples (P < 0.05). A total of 603 peptides differed significantly in abundance between milk and gastric samples (P < 0.05). Most of the identified peptides have previously identified biologic activity. Gastric proteolysis occurs in the term infant in the first 2 wk of life, releasing biologically active milk peptides with immunomodulatory and antibacterial properties of clinical relevance to the proximal intestinal tract. Data are available via ProteomeXchange (identifier PXD000688).", "claims": [{"id": "claim-target-result", "statement": "The study found that gastric proteolysis in term infants during the first 2 weeks of life releases biologically active milk peptides; significance was assessed using P < 0.05, although the statistical test is not named, and the source data are available through ProteomeXchange under identifier PXD000688.", "kind": "quantitative", "target": {"value": 0.05, "unit": "p-value", "tolerance": null, "source": "The numbers of peptides from β-casein, lactoferrin, α-lactalbumin, lactadherin, κ-casein, serum albumin, bile salt–associated lipase, and xanthine dehydrogenase/oxidase were significantly higher in the gastric samples than in the milk samples (P < 0.05)."}, "evidence": [{"asset": "source:pmid:24699806", "locator": "sections[0] \"Abstract\" paragraph 1", "quote": "Gastric proteolysis occurs in the term infant in the first 2 wk of life, releasing biologically active milk peptides with immunomodulatory and antibacterial properties of clinical relevance to the proximal intestinal tract."}, {"asset": "source:pmid:24699806", "locator": "sections[0] \"Abstract\" paragraph 1", "quote": "The numbers of peptides from β-casein, lactoferrin, α-lactalbumin, lactadherin, κ-casein, serum albumin, bile salt–associated lipase, and xanthine dehydrogenase/oxidase were significantly higher in the gastric samples than in the milk samples (P < 0.05)."}, {"asset": "source:pmid:24699806", "locator": "sections[0] \"Abstract\" paragraph 1", "quote": "A total of 603 peptides differed significantly in abundance between milk and gastric samples (P < 0.05)."}, {"asset": "source:pmid:24699806", "locator": "sections[0] \"Abstract\" paragraph 1", "quote": "Data are available via ProteomeXchange (identifier PXD000688)."}], "state": "complete"}], "gaps": []}, "experiment": {"state": "partial", "objective": "The study found that gastric proteolysis in term infants during the first 2 weeks of life releases biologically active milk peptides; significance was assessed using P < 0.05, although the statistical test is not named, and the source data are available through ProteomeXchange under identifier PXD000688.", "steps": [{"id": "read_published_estimate", "order": 1, "name": "Read the published estimate from the source", "kind": "other", "state": "complete", "blocked_on": null, "description": "The claim, method and evidence span published with the source article.", "duration_hours": null, "parameters": {}, "inputs": ["source:pmid:24699806"], "outputs": ["the published estimate and its evidence"], "instruments": [], "reagents": []}, {"id": "obtain_source_data", "order": 2, "name": "Obtain the source data from the named repository", "kind": "data-preparation", "state": "blocked", "blocked_on": "data:accession_absent", "description": "The GEO series accession resolves and its sample accessions are listed. 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