Understanding the interplay between food structures, ileum and appetite regulation
File(s)
Author(s)
Dagbasi, Aygul
Type
Thesis
Abstract
Evidence suggests that the ileum is an important player in appetite regulation. The ileum
contains a high density of L-cells that secrete appetite suppressing hormones Glucagon Like
Peptide-1 and Peptide YY (PYY) in response to luminal nutrients and bacterial fermentation
products, short chain fatty acid (SCFAs). Processing of foods may change their structures and
reduce the amount of carbohydrates reaching the ileum, which may reduce appetite hormone
release. However, access to the human ileum is difficult and little is known about the interplay
between food, ileum environment and appetite hormone release.
This thesis aimed to understand the impact of food structures on the levels of carbohydrate
reaching the ileum and their effect on SCFA production and appetite hormone release. A
nasoenteric tube was placed in the distal ileum of healthy participants (n=10) who consumed
one of the three intervention diets for four days: High fibre, intact structures (I-HF) High fibre,
disrupted structures (D-HF) or Low fibre, disrupted structures (LF). Blood and ileal samples
were collected on day 4 in fasted and fed states (hourly for 8h).
Disrupting the food structures of a high fibre diet (D-HF) reduced the amount of reducing
sugars and bile acids, but not starch, in the ileal space compared to a high fibre intact diet (IHF). The numbers of bacteria and the concentrations of SCFAs in the ileum dramatically
dropped from fasted to postprandial states, and this effect was not different between the groups.
Postprandial PYY release was higher in D-HF in comparison to LF. Metabolomic analysis of
ileal contents identified dynamic changes in several metabolites which were different between
groups, including aspartate which was higher in D-HF compared to I-HF and LF. In addition,
D-HF had higher serum SCFAs compared to I-HF and LF groups. Therefore a difference in
ileal metabolites and/or colonic fermentation may be playing a part in the observed PYY
difference. Further studies are needed to better understand the role of food structures and ileal
metabolites in appetite hormone release.
contains a high density of L-cells that secrete appetite suppressing hormones Glucagon Like
Peptide-1 and Peptide YY (PYY) in response to luminal nutrients and bacterial fermentation
products, short chain fatty acid (SCFAs). Processing of foods may change their structures and
reduce the amount of carbohydrates reaching the ileum, which may reduce appetite hormone
release. However, access to the human ileum is difficult and little is known about the interplay
between food, ileum environment and appetite hormone release.
This thesis aimed to understand the impact of food structures on the levels of carbohydrate
reaching the ileum and their effect on SCFA production and appetite hormone release. A
nasoenteric tube was placed in the distal ileum of healthy participants (n=10) who consumed
one of the three intervention diets for four days: High fibre, intact structures (I-HF) High fibre,
disrupted structures (D-HF) or Low fibre, disrupted structures (LF). Blood and ileal samples
were collected on day 4 in fasted and fed states (hourly for 8h).
Disrupting the food structures of a high fibre diet (D-HF) reduced the amount of reducing
sugars and bile acids, but not starch, in the ileal space compared to a high fibre intact diet (IHF). The numbers of bacteria and the concentrations of SCFAs in the ileum dramatically
dropped from fasted to postprandial states, and this effect was not different between the groups.
Postprandial PYY release was higher in D-HF in comparison to LF. Metabolomic analysis of
ileal contents identified dynamic changes in several metabolites which were different between
groups, including aspartate which was higher in D-HF compared to I-HF and LF. In addition,
D-HF had higher serum SCFAs compared to I-HF and LF groups. Therefore a difference in
ileal metabolites and/or colonic fermentation may be playing a part in the observed PYY
difference. Further studies are needed to better understand the role of food structures and ileal
metabolites in appetite hormone release.
Version
Open Access
Date Issued
2021-12
Date Awarded
2022-08
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Frost, Gary
Sponsor
Biotechnology and Biological Sciences Research Council (Great Britain)
Publisher Department
Department of Metabolism, Digestion and Reproduction
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)