Oat beta glucan: Multiple roles in the gut. A.R. Mackie, B.H. Bajka, B. Kirkhus

Transcription

1 Oat beta glucan: Multiple roles in the gut A.R. Mackie, B.H. Bajka, B. Kirkhus

2 Introduction Food is consumed Food resides in the stomach Chyme is gradually emptied into the duodenum Can oat beta glucan have an effect on gastric behaviour? Viewed from the back

3 Introduction Chyme is digested and nutrients released Nutrients diffuse through the intestinal mucus to the enterocytes for absorption Nutrients are detected by endocrine cells that secrete CCK, GIP, GLP-1, etc CCK decreases gastric emptying and increases enzyme secretion

4 Introduction Can mucus permeability have Controlling rates of digestion through gastric retention. (Fuller for longer) an effect on any of this? Controlling rates of digestion in the small intestine (ileal brake, etc) Altering intestinal mucus permeability Sensing nutrients in the small intestine

5 Particle size and polymer release The aim of this study was to determine the extent to which oat particle size and beta glucan release in a porridge could alter: Glucose response Gastric behavior Gastrointestinal hormone response Subjective feelings of appetite and satiety.

6 The study design Cross-over study measuring parameters: MRI VAS Blood Gastric volume, Structure of gastric contents Hunger, Fullness, Satisfaction, Desire to eat and Thirst Insulin, glucose and GI hormones; (cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), gastric inhibitory polypeptide (GIP) and peptide YY (PYY))

7 Porridges Energy Oat flake porridge Oat flour porridge Kcal/100 g Kcal for 264 g portion Nutrition g/100g g/ 264 g g/100g g/ 264 g Fat Carbohydrate Fiber Protein Salt Calorie density ~ 0.54 kcal/ml consumed

8 MRI

9 Phase separation After 5 mins After 25 mins

10 Gastric volume data Mean +/- standard error oat flakes (continuous line) oat flour (dashed line). Mean emptying times (T 1/2 )are 74 +/- 17 min and 84 +/- 11 min for the flour and flake porridge, respectively. Giving mean emptying rate of 3.3 +/- 0.7 and 2.7 +/- 0.5 (p=0.175) ml/minute.

11 Appetite scores Mean difference from baseline +/- standard error

12 Glycaemic response oat flakes (continuous line) oat flour (dashed line). Mean difference from baseline +/- standard error

13 Conclusions The oat porridge emptied at about 1.5 kcal/min. The oat flake porridge emptied slightly more slowly The subjective satiety scores were the same including a crossover at ~100 mins Plasma glucose response was similar for both samples Plasma insulin and GIP responses were reduced for the flakes

14 Conclusions The glucose peaks were not significantly different in the Healthy participants The GIP and GLP-1 both showed a reduced peak in response after consumption of the flakes indicating lower intestinal glucose concentrations The flakes give a lower glycaemic response but the crossover at ~100 mins suggests the reason is not simple.

15 Intestinal mucosa interactions Part 2 Flake structure or soluble beta glucan? β-glucan release was significantly different: Flour porridge was /-1.8% Flake porridge was /- 1.5% Viscosity of the extracts was similar: Flour porridge was / mpas Flake porridge was / mpas Mw = 1.1 MDa

16 Intestinal mucosa: A pig study Pigs were fed for 3 days Control diet Control diet + 10% oat bran Pigs were slaughtered and the intestines collected Viscosity and permeability of intestinal mucus was determined

17 Introduction: Intestinal Mucus Structure AFM images The mean pore diameter in purified jejunal MUC2 mucin was ~100 nm Johansson, M. E. V. et al. Nat. Rev. Gastroenterol. Hepatol. 10(6) 352 (2013) Round Mackie, Biomacromolecules 13(10) 3253 (2012)

18 Introduction Mucus is negatively charged and full of holes Charge plays a key role in mucus penetration Size is important (polymers and self-assembled lipid structures) Bajka, Mackie, Colloids and Surf. B (2015)

19 Intestinal Mucus permeability Measuring particle diffusion Micro-viscosity of porcine mucus Mean square displacement (MSD) <Δr 2 (Δt)> = <Δx 2 + Δy 2 > D eff = MSD/4Δt = kt/6π r viscosity

20 CONFOCAL MICROSCOPY The effect of Bile Salts on the diffusion of lipid digesta Gastro-duodenal emulsions 15 minutes 3 hours 30 minutes MUCUS MUCUS

21 The role of endogenous polymers Water mucin ex vivo mucus DNA Diffusion coefficient of 500nm latex beads plotted as a function of polymer concentration.

22 Increasing dietary oat fibre decreases the permeability of intestinal mucus The data from this study showed for the first time that reducing mass transfer of bile and lipid through the intestinal mucus layer may be one way in which this decrease in bile reabsorption by soluble fibre is enabled. Journal of Functional Foods 26 ( )

23 Conclusions Oat fibre has been shown to have a range of effects but is soluble beta-glucan effective at lowering GI? Oat bran can increase the microviscosity of intestinal mucus The oat bran also decreased the diffusion of digesta through the mucus Can soluble fibre decrease duodenal hormone secretion?

24 17 th Food Colloids Conference: Application of Soft Matter Concepts 8 th -11 th April 2018 The University of Leeds, UK Themes The main theme of this conference is Application of Soft Matter Concepts and the following scientific sessions will cover a series of topics illustrating the interplay between fundamental colloid science research and more applied soft matter research. Interfacial design Relating structure to properties (macro-meso-micro-nano) Biopolymer interactions Colloidal aspects of eating and digestion Processing of novel structures for functionality Key Dates and Information Abstract Submission Open: 4 th September 2017 Early Bird Registration Ends 16 th February 2018 Speakers Dr. Paul Clegg Prof. Francisco M. Goycoolea Dr. Yoav D. Livney Prof. Harjinder Singh Prof. Raffaele Mezzenga Organisers Dr. Anwesha Sarkar Prof. Brent S. Murray fc2018@leeds.ac.uk