This thesis investigated the bioactivity of a crude and depolymerised polysaccharide rich extract from summer harvested Irish Laminaria digitata (LD). An in vitro human colonic model was employed to test the extracts in comparison with cellulose and fructooligosaccharides as respective negative and positive controls, on the composition (16S rDNA sequencing) and metabolic activity (short chain fatty acids (SCFA)) of the gut microbiota (GM). Furthermore, the effect of the crude LD extract on the composition and metabolic activity of the GM along with its effect on markers of bone health were assessed using murine models. Both extracts demonstrated fermentability by human faecal bacterial populations with significant increases in Lachnospiraceae and Parabacteroides and Dialister species, acetate, propionate, butyrate and total SCFA noted. In-vivo supplementation with the crude LD extract (5%) in the standard diet mouse model resulted in significant changes to the composition of the GM including: increased diversity, significant reductions in the Firmicutes to Bacteroidetes ratio, with division wide reductions in Firmicutes and a number of increases in Bacteroidetes, including Prevotella, Bacteroides and Parabacteroides species. Modulation of bone remodeling (increases in osteocalcin, reductions in TRACP-5b), reduced body weight and reduced serum cholesterol was also found with LD supplementation. In the diet induced obese murine model, LD (5%) increased the proportion of Akkermansia species by 150 fold, reduced Firmicutes to Bacteroidetes ratio, increased colonic and caecal butyrate concentrations in young adult mice and reduced total SCFA in mature adult mice. Anti-obesogenic effects were found including: significantly reduced fat mass, serum cholesterol, leptin and lipopolysaccharide binding protein concentrations. These results highlight the potential of the fibre component of LD as a beneficial GM modulating functional food ingredient to promote bone health and protect against obesity. Further work is required to assess whether such effects occur in humans.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:706473 |
| Date | January 2016 |
| Creators | Strain, Conall Reamonn |
| Publisher | Ulster University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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