ALLERGY: EUROPEAN JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY, cilt.79, sa.S113, ss.102-103, 2024 (SCI-Expanded)
Background: Bovine beta-casein A2 milk is becoming
increasingly popular, with both producers and consumers demonstrating a rising
inclination towards its production. In the beta-casein locus, alleles A1 and A2
exhibit disparity at amino acid position 67, wherein A1 codes for histidine and
A2 codes for proline. The breakdown of A1 beta-casein leads to the generation
of beta-casomorphin (BCM)-7, a bioactive peptide possessing morphine-like
properties. The increasing preference for A2 milk is often attributed to its
perceived benefits, particularly its potential to elicit fewer inflammatory
responses compared to A1 milk. However, the understanding of this subject
remains limited. This study aims to comprehensively examine the effects of
BCM-7 and BCM-9, bioactive peptides resulting from the digestion of A1 and A2
milk, respectively, on the integrity of the gut epithelial barrier.
Method: A microfluidic gut-on-a-chip plate was
employed to form a tubular barrier utilizing Caco-2 cells, enabling the
assessment of the impacts of BCMs on gut epithelial cells and their barrier
function. The concentrations of peptides utilized in the study were selected
based on their relevance in vivo, considering the presence of these compounds
in raw milk or cheese. Following cytotoxicity assessment, transepithelial
electrical resistance (TER) measurement, paracellular permeability assay, wound
healing assay, targeted proteomics using proximity extension assay, untargeted
proteomics, and RNA sequencing were performed.
Results: Monolayer cultures did not exhibit
cytotoxicity upon exposure to bovine BCM-7 and BCM-9. In addition, no
significant findings were observed in the targeted proteomics assessment. Based
on RNA sequencing results, alterations in the expression profile of 231 genes
were identified with BCM-7 (20 ug/ml), while BCM-9 did not show any significant
transcriptome changes. Among these, KLHDC7B, HOOK3, PKD1P2, G6PC1, L3MBTL1,
IDI2-AS1, and DDX60L genes showed the highest upregulation (2.27 to 3.50 fold),
while TFDP2, ANAPC13, and CXCL8 genes demonstrated the most significant
downregulation (−2.47 to −2.61 fold). Pathway analysis highlighted pathways
associated with cellular metabolism and biogenesis, encompassing signal
transduction, organelle organization and biogenesis, cytoskeleton, and
microtubule organization, as well as cell cycle checkpoints.
Conclusion: Taken together, while BCM-7 showed
significant differences in transcriptomic profiling, BCM-9 displayed an
inactive nature to Caco2 cells. Conflicts of interest: The authors did not
specify any links of interest.