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Epigenetic effects of casein-derived opioid peptides in SH-SY5Y human neuroblastoma cells.

Trivedi MS, Hodgson NW, Walker SJ, Trooskens G, Nair V, Deth RC. (2015) Nutr Metab (Lond).  12 54. doi: 10.1186/s12986-015-0050-1. eCollection 2015. 

Web URL: View this and related abstracts via PubMed here. Free full text of this article is available online

Abstract:

BACKGROUND:

Casein-free, gluten-free diets have been reported to mitigate some of the inflammatory gastrointestinal and behavioral traits associated with autism, but the mechanism for this palliative effect has not been elucidated. We recently showed that the opioid peptide beta-casomorphin-7, derived from bovine (bBCM7) milk, decreases cysteine uptake, lowers levels of the antioxidant glutathione (GSH) and decreases the methyl donor S-adenosylmethionine (SAM) in both Caco-2 human GI epithelial cells and SH-SY5Y human neuroblastoma cells. While human breast milk can also release a similar peptide (hBCM-7), the bBCM7 and hBCM-7 vary greatly in potency; as the bBCM-7 is highly potent and similar to morphine in it's effects. Since SAM is required for DNA methylation, we wanted to further investigate the epigenetic effects of these food-derived opioid peptides. In the current study the main objective was to characterize functional pathways and key genes responding to DNA methylation effects of food-derived opioid peptides.

METHODS:

SH-SY5Y neuroblastoma cells were treated with 1 μM hBCM7 and bBCM7 and RNA and DNA were isolated after 4 h with or without treatment. Transcriptional changes were assessed using a microarray approach and CpG methylation status was analyzed at 450,000 CpG sites. Functional implications from both endpoints were evaluated via Ingenuity Pathway Analysis 4.0 and KEGG pathway analysis was performed to identify biological interactions between transcripts that were significantly altered at DNA methylation or transcriptional levels (p < 0.05, FDR <0.1).

RESULTS:

Here we show that hBCM7 and bBCM7, as well as morphine, cause epigenetic changes affecting gene pathways related to gastrointestinal disease and inflammation. These epigenetic consequences exhibited the same potency order as opiate inhibition of cysteine uptake insofar as hBCM7 was less potent than bBCM7, which was less potent than morphine.

CONCLUSION:

Our findings indicate that epigenetic effects of milk-derived opiate peptides may contribute to GI dysfunction and inflammation in sensitive individuals. While the current study was performed using SH-SY5Y neuronal cellular models, similar actions on other cells types might combine to cause symptoms of intolerance. These actions may provide a potential contributing mechanism for the beneficial effects of a casein-free diet in alleviating gastrointestinal symptoms in neurological conditions including autism and other conditions. Lastly, our study also contributes to the evolving awareness of a "gut-brain connection".

FAB RESEARCH COMMENT:

This in vitro study found that an opioid-like peptide (BCM-7) arising from the digestion of the A1 milk protein beta-casein (found in ordinary cows' milk) can influence the development of human brain cells in a similar way to morphine.  The same was not true of similar peptides derived from human milk (which contains an A2-like form of beta-casein).

The changes observed in response to A1-derived BCM-7 (and morphine) included increased proliferation of cells, and reduced differentiation. They also build on previous research by the same team showing important effects of peptides derived from both gluten and casein. See:
As the researchers point out, further work is needed to find out if these effects may be generalisable to animals or humans. However, these findings add to the literature linking possible benefits of diets free of casein and gluten (which also yields opioid peptides on digestion) to autism and other neurodevelopmental conditions. 

For more information on this work, see the following FAB Events at which Dr Trivedi presented and discussed this research:
And for more information on differential effects of A1 vs A2 beta-casein, as demonstrated in human and animal studies, see: