Alyami, Jaber
(2019)
Magnetic resonance imaging studies of gastrointestinal, metabolic and appetitive responses to isoenergetic breakfasts of different plant grain origin.
PhD thesis, University of Nottingham.
Abstract
Introduction: Cereal grain based porridges are commonly consumed throughout the world. Cereal types that are popular in the Western world, such as oats and rye, have been characterised with respect to health related variables such as glycaemic response and suppression of hunger. However, other ‘ancient grains’ consumed in the Asia and in Africa, such as millets, have been studied minimally although they are believed to offer health benefits. Consuming these grains may be advantageous in the control of obesity and type 2 diabetes, the incidence of which are increasing globally. They are also a sustainable food, due to their tolerance of extreme weather and harsh growing conditions. It is thus timely to consider whether they should be exploited to a greater extent as a human food, both from a health and environmental perspective. Concurrently the development of novel magnetic resonance imaging (MRI) techniques enable a deeper understanding to be gained of the impact on health of the interaction between the GI tract and specific food. The aim of this project was thus to investigate the glycaemic, gastrointestinal, hormonal and appetitive response ratings to breakfast porridge made from different grains in healthy subjects (HVs) whilst exploiting and developing MRI.
Methods: Firstly, a cross-over pilot study (AMORE) was undertaken in sixteen healthy participants [ten female and six male, 20.9 (SD 0.9) years old, BMI 22.1 (SD 2.9) kg/m2 ] to produce data on postprandial glucose levels (using finger prick), gastric emptying, small bowel water contents (using MRI) and satiety (using VAS scales and food diaries) following consumption of isoenergetic breakfast porridges made from oats, rye (both in flakes form), and finger (ragi) millet and pearl (bajri) millet grains (in flour form).
Secondly, a cross-over study (MOM) was undertaken in twenty six healthy subjects (17 females and 9 males, aged 28.5 (SD 9.6) years old, and with a BMI of 23.4 (SD 3.2) kg/m2) who consumed two iso-energetic/iso-volumetric PMP or SOP breakfast meals, provided with a drink of water. At baseline and for two hours postprandially, MRI measurements were taken of gastric volume. Blood samples were collected to measure glucose, insulin, GLP-1, GIP and PYY. An ad libitum test meal was offered at lunch. Self-reported appetite ratings were collected over the visit and food intake records were kept for the remainder of the day.
Lastly, a MRI developmental study (Tagging study) was undertaken to investigate the feasibility of using a continuously tagged magnetic resonance imaging sequence to monitor and assess gastric handling (such as flow and mixing) of breakfast porridge meals in HVs.
Key results: Seven participants completed the entire protocol in the pilot study and were included in the final analysis. A subgroup analysis with the n =10 paired comparison between the same individuals that completed the oats, rye and pearl millet was also considered. The study showed that the gastric volume AUC was higher for pearl millet than oats and rye (n =10, P < 0.001). The incremental area under the curve (iAUC) for blood glucose was not significantly different between the meals although this showed a trend to be lower for pearl millet. Hunger VAS was lower for pearl millet compared to oats and rye (n= 10, P = 0.01). There was a significant correlation between total gastric volume AUC and average appetite AUC (r =−0.47, P < 0.010).
The MOM study showed iAUC2h blood glucose was not significantly different between the porridges (P ˃ 0.05). The iAUC2h gastric volume was larger for PMP compared with SOP (P = 0.045). The iAUC2h GIP concentration was significantly lower for PMP compared with SOP (P = 0.001). The other hormones and appetite responses were similar between meals.
The tagging study showed that the shorter delay time resulted in higher coefficient of variation (CoV) across the proximal and distal part of the stomach and whole stomach regions. Tagged cine-MRI can be used to assess dynamic intragastric handling of breakfast meals.
Conclusions: Pearl millet porridge elicited glycaemic and appetite responses comparable to oats, a known health-promoting grain. GIP is an incretin hormone that has been linked to triacylglycerol absorption in adipose tissue, therefore the lower GIP response for PMP, may be an added health benefit. PMP could represent a sustainable, alternative breakfast intervention.
The tagging method developed is relatively easy to implement and could provide an additional parameter to add to the scan card for future studies.
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