Impact of amyloid-like ovalbumin fibril consumption on health-related markers: An in vitro approach

Induction of amyloid-like morphology in food proteins offers high potential to induce new techno-functional properties in food products (e.g. use as emulsifier, thickener or gelling agent in e.g. bakery and confectionery products). However, the health impact of amyloid-like fibril (ALF) consumption remains widely understudied and merits additional research. The aim of this study was to (partially) elucidate the general health impact of food-borne ALF consumption, using egg white ovalbumin as a case study. Based on in vitro cell culture models it was demonstrated that ovalbumin ALFs (i) do not induce direct cytotoxic effects on intestinal (Caco-2, IPEC-J2) and neuronal (SH-SY5Y) cell lines, but (ii) are able to induce a Toll-like-receptor-mediated innate immune response, similar to endogenous amyloids, in activated THP-1 cells. Furthermore, the consecutive in vitro digestion and absorption (enterocyte and M-cell) experiments demonstrated that ovalbumin ALFs (i) do not completely lose their ALF morphology upon in vitro gastrointestinal digestion, and that (ii) the ALF core sequences, located at the center of the ALF structure, are transported across Caco-2 based cell models, suggesting aggregate transport. In vivo, intestinal translocation of ingested ALFs would imply potential cross-seeding of endogenous, disease-related precursor proteins. The ability of ovalbumin ALFs to induce aggregation of a disease-related precursor protein, alpha Syn, was evaluated in a precursor overexpressing cell model. Here, it was illustrated that only homologous (alpha Syn) - but not heterologous (ovalbumin) - seeding resulted in intracellular aggregation bodies of (phosphorylated) alpha Syn. The lack of cross-seeding supports the assumption that ovalbumin ALF consumption is not a risk factor for the development of alpha-synucleinopathies like Parkinson's disease.