Blood Glucose-attenuating Effects of Pea-derived Fractions: Exploration of Mechanisms of Action in a Rat Model of Glucose Intolerance

• Author / Creator

  Hashemi, Seyede Zohre

• Pulses, including dried peas, are nutrient-dense foods rich in fibre that have shown efficacy in improving glucose control in diabetic subjects. The seed coats, in spite of being the highly fibrous part, are sometimes discarded as a food-processing by-product. We hypothesized that supplementing high fat diets (HFD) with pea seed coats (PSC) would improve glucose tolerance mainly by modifying gut responses to glucose and reducing HFD-induced stress on pancreatic islets. A secondary hypothesis was that the glucose-lowering effects of these fractions would be retained following cooking. HFD-induced glucose intolerant Sprague Dawley rats were fed a HFD supplemented with raw or cooked PSC for 4 weeks. HFD and low fat diet with inclusion of cellulose as the fibre source were used as control diets. The results showed that, compared to HFD, cooked PSC diet improved glucose response, decreased postprandial insulin secretion and enhanced fasting GLP-1 and GIP response to glucose. Cooked PSC feeding also decreased fasting glucagon, which was associated with reduced alpha-cell mass. Microbial analysis revealed that PSC diets significantly altered the overall composition of gut microbiota and resulted in increased population of Lachnospiraceae, a butyrate-producing family of bacteria. Additionally, cooked PSC was found to increase the expression of mRNA encoding mucin proteins in the ileum and induce a trend toward decreased expression of ileal TLR2. The effect of pea/bean consumption on the B vitamin status was examined in normoglycemic humans, showing that blood concentrations of thiamine and folate were not affected by pulse-containing diets. Overall, our results demonstrated that cooked PSC feeding can reverse adverse effects of HFD on glucose homeostasis via gut- and islet-mediated mechanisms. In particular, cooked PSC feeding is associated with enhanced incretin secretion, reduced alpha-cell abundance and glucagon concentrations, beneficial alterations in the gut microbiota and finally up-regulated expression of protective genes involved in gut barrier function. The higher effectiveness of the cooked PSC as compared to raw PSC showed that cooking treatment enhanced beneficial impacts of these components on glucose homeostasis.

• Subjects / Keywords

  • Glucagon
  • Incretins
  • Pancreatic islets
  • Glycemia
  • Pulse grains
  • Gut microbiota
  • Insulin resistance

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3GQ6R72X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.