Investigating the Effects of High Amylose Wheat on Metabolic, Gastrointestinal and Reproductive Outcomes Using A Mouse Model

Abstract

High amylose wheat (HAW) is a novel wheat variety with markedly higher levels of amylose, resistant starch and nutrients and a lower glycaemic index compared to commercial standard amylose wheat (SAW) and therefore may confer additional health benefits. While a few studies have indicated that HAW can improve some aspects of metabolic and gastrointestinal health, there was a limited understanding of whether and to what extent these effects varied according to the level of HAW consumed. Furthermore, no studies had determined whether these effects differed between males and females. While improved dietary quality, including increased whole grain intake, has been associated with improved reproductive parameters, the potential impact of HAW on reproductive health had also not been determined. Therefore, the central aim of this thesis was to determine the effects of HAW on metabolic, gastrointestinal and reproductive health outcomes in healthy lean male and female mice. In Chapter 2, consumption of HAW (35-65% w/w) for eight weeks was associated with a sex-specific effect on several metabolic parameters, including food intake, respiratory quotient (RQ), growth and fat mass. Importantly, these effects were appeared to be dependent on the level of HAW consumed. Specifically, consumption of the lowest level of HAW (35% w/w) was associated with a higher food intake and RQ in female mice whereas consumption of the highest level of HAW (65% w/w) reduced fat mass, particularly abdominal fat mass, in male mice. There was no clear evidence that HAW improved blood glucose or lipid control. The results presented in Chapter 3 indicated that increased consumption of HAW had effects on several gastrointestinal measures, and these effects were more pronounced in female mice compared to their age-matched male counterparts. The effects observed included increased gastrointestinal weights, enhanced gastric motility and increased mRNA expression of the intestinal barrier marker Ocln and the gut hormone Pyy. In both sexes, consumption of higher levels of HAW (50-65% w/w) was associated with increased faecal bacteria load and diversity and a shift in the gut microbiota composition in a manner consistent with improved gastrointestinal health, including increased relative abundance of Bacteroidetes phylum and decreased relative abundance of Firmicutes phylum. In Chapters 2 and 4, consumption of HAW was associated with positive effects on reproductive health in both male and female mice, including increased testicular weights and an altered pattern of vaginal cytology parameters towards a longer time in estrus/metestrus and less time in diestrus. The positive effects of HAW for female reproductive health were further confirmed by the findings in Chapter 4 where the intake of HAW before and during pregnancy was associated with significantly improved pregnancy rates compared to those consuming SAW diet (94% vs 61%). Overall, this thesis has provided evidence that consumption of HAW may have benefits on metabolic and gastrointestinal health with dose-dependent and sex-specific effects, and consumption of HAW may improve reproductive function in both males and females. While further studies are required, these results support the potential application of HAW as a functional food to improve health in human consumers.