Oxidized polyunsaturated fatty acid promotes colitis and colitis-associated tumorigenesis in mice

Background and aims: Human studies suggest that a high intake of polyunsaturated fatty acid (PUFA) is associated with an increased risk of inflammatory bowel disease (IBD). PUFA is highly prone to oxidation. To date, it is unclear whether unoxidized or oxidized PUFA is involved in the development of IBD. Here, we aim to compare the effects of unoxidized PUFA vs. oxidized PUFA on the development of IBD and associated colorectal cancer.

Methods: We evaluated the effects of unoxidized and oxidized PUFA on dextran sodium sulfate (DSS)- and IL-10 knockout-induced colitis, and azoxymethane (AOM)/DSS-induced colon tumorigenesis in mice. Additionally, we studied the roles of gut microbiota and Toll-like receptor 4 (TLR4) signaling involved.

Results: Administration of a diet containing oxidized PUFA, at human consumption-relevant levels, increases the severity of colitis and exacerbates the development of colitis-associated colon tumorigenesis in mice. Conversely, a diet rich in unoxidized PUFA doesn't promote colitis. Furthermore, oxidized PUFA worsens colitis-associated intestinal barrier dysfunction and leads to increased bacterial translocation, and it fails to promote colitis in Toll-like receptor 4 (TLR4) knockout mice. Finally, oxidized PUFA alters the diversity and composition of gut microbiota, and it fails to promote colitis in mice lacking the microbiota.

Conclusions: These results support that oxidized PUFA promotes the development of colitis and associated tumorigenesis in mouse models via TLR4- and gut microbiota-dependent mechanisms. Our findings highlight the potential need to update regulation policies and industrial standards for oxidized PUFA levels in food.