To evaluate the effect of oat processing on bi-accessibility of oat avenanthramides (AV), establish the role of oat AV in modulating postprandial blood glucose response using a pilot acute human feeding trial, and determine the molecular mechanism through which AV exert its anti-glycemic properties.
In the current project, we explored the effects of avenanthramides (AV), a unique polyphenol present in oats on glucose release and transport using well established molecular biochemistry tools. Secondly, we investigated the effect of different processing techniques on the bio-accessibility of AV. After the initial studies and screening, we examined the effects of varying levels of AV on post-prandial glycemic response in humans using an acute human feeding study.
In this study we used Xenopus laevis oocytes expressing GLUT2 or SGLT1and human Caco-2 cells models to investigate the effect of oat avenanthramides on human intestinal glucose transporters. The presence of avenanthramide reduced the glucose uptake in a dose-dependent manner in Caco-2 cells. Glucose uptake in oocytes injected to express either GLUT2 or SGLT1 was nullified by oat avenanthramide. There was no significant difference between the inhibition potencies of avenanthramide C and B. Overall, our results suggest that avenanthramides may contribute to the antidiabetic properties of oat. The outcomes from this part of the study have been written up as a manuscript and submitted to journal “Frontiers in Nutrition” for publication, which is under review.
During this period, a sensitive UPLC based method to profile the polyphenols in oats has been developed. The quantification of the polyphenol bio-availability after each processing step was measured.
For the evaluation of AV in Canadian oats, we received oat cultivars from breeder Dr. Jennifer Mitchel Fetch, AAFC Brandon Research and Development Centre grown under different environmental conditions to obtain various levels of AVs. Oat materials received were dehulled, milled and phenolics were extracted and analyzed using UPLC.
A human feeding study evaluating the effects of AV on post-prandial glucose response was conducted. It was an acute double-blind cross-over design, took place at Richardson Centre for Functional Food and Nutraceuticals (RCFFN) in University of Manitoba, Winnipeg, Canada. This trial followed the standard of Good Clinical Practice (GCP) and all local and national guidelines.
Participants participated in 2 acute sessions over 2 weeks. Participants were randomized to one of the two groups:
- Consume oatmeal contains high avenanthramides (treatment A) at their first study visit, then consume oatmeal contains low avenanthramides (treatment B) at their second study visit.
The study outcomes showed that there was no significant difference on the glycemic response curve between the high and low AV oat varieties. This could be due to the level of AV present naturally in oats may not be enough to impart a physiological change or it could be due to the presence of beta-glucan, which could be inhibiting the bio-accessibility of phenolics in the GI tract.