The Effects of Flaxseed and Its Bioactives on Colon Health and DSS-induced Acute Colitis and Recovery in C57BL/6 Mice
Flaxseed (FS) contains bioactives with gut health promoting potentials, including soluble fibre, α-linolenic acid (ALA), and lignans. It also contains nutritive proteins. FS bioactives are unequally distributed in the seed, with the hull enriched in fibre and lignans, and the kernel enriched in ALA and protein. On account of anticancer and cholesterol lowering effects of FS, currently there is an increasing interest in consumption of FS-based products and supplements; however, their effect on healthy colon and common gastrointestinal disorders, e.g. colitis, is unknown. Thus, this thesis explored the effects of FS, FS hull and kernel, and FS purified bioactives (oil, protein and mucilage) on dextran sodium sulphate (DSS)-induced colitis symptoms in mice. Additionally, the effects of FS and its purified bioactives (oil, protein and mucilage) on some biomarkers of gut health in a healthy state were investigated. The results of this study showed that consumption of 10% FS diet advanced colitis symptoms by increasing disease activity index (DAI), colonic histological damage and myeloperoxidase (MPO) levels, while increased serum and colon inflammatory cytokines. FS adverse effect on colitis was associated with upregulation of seven genes involved in the NF-κB signalling pathway in colon. FS hull and kernel had less influence on colitis symptoms. Purified FS protein and mucilage also aggravated DSS-induced colitis symptoms, while reduced the survival rate during the recovery period. FS oil had fewer effects on colitis symptoms. In healthy animals, FS increased biomarkers of bacterial activity (cecum size, cecal short chain fatty acid levels [SCFAs]), increased crypt length and mucus production, unregulated several genes involved in bacterial defense and immune and inflammatory response, while down-regulated numerous genes involved in cell cycle events. FS mucilage and protein also increased cecum size and SCFA levels, but FS mucilage increased crypt length in colon and FS protein reduced it. FS oil also reduced crypt length in healthy animals, without any other significant changes in cecum or colon. Overall, these findings imply that consumption of FS, FS protein and mucilage influence biomarkers of colon health, such as bacterial activity and mucosal barrier integrity in healthy mice, while aggravating DSS-induced acute colitis symptoms.