It is generally recognised that the diet has implications for colonic health, i.e. inflammatory bowel diseases and colorectal cancer. The incidences of non-infectious diseases such as inflammatory bowel diseases and colorectal cancer are increasing in Denmark and other western countries. Regulation of the number and composition of gut bacteria by dietary means is in this respect considered crucial for the prevention of gut disease in general. A western sedentary lifestyle with an almost constant access to easily digested food with a high energy and fat density and low in dietary fibre is considered the main factor responsible for this development. The same dietary and lifestyle factors, however, are also considered responsible for the undesired development in overweight, obesity and type 2 diabetes (T2DM) seen in the adult population in most western societies.
The overall objective of the project is to improve colonic health, peripheral insulin sensitivity and glucose homeostasis by increased colonic butyrate production brought about by pre-, pro- and synbiotic concepts.
The project is organised in three work packages (WP): a WP addressing prebiotics and diet formulation and two cluster WPs addressing different aspects related to gut health and insulin sensitivity, respectively, with the following specific aims:
1. Quantify the implication of pre- and probiotics on colonic butyrate production
2. Develop novel synbiotic concepts for improved butyrate production
3. Document the impact of enhanced butyrate production on colonic health parameters expresses by:
a) oxidative stress of colonic mucosa
b) maintained gut barrier function
c) inflammatory response
4. Document the impact of increased butyrate production on insulin sensitivity and glucose homeostasis expressed by:
a) improved whole body insulin sensitivity
b) altered metabolism in skeletal muscle and adipose tissue
Outline of the project
Schematic project overview
WP1: Prebiotics and diets
The aim of this WP is to (1) produce and formulate the WSD diet and two model diets with increased levels of RS and AX and (2) produce and characterise novel prebiotics based on RS and AX.
A Western Style Diet (WSD) formulated to mimic the risk factors for colon diseases and T2DM (high fat, high protein, low fibre) will be developed and used as reference in all intervention studies. Bread and breakfast cereals enriched in AX and RS and with different physical forms will be produced.
WP2: Gut health
The objective of this cluster WP is to substantiate the implication of butyrate on gut health and to develop novel synbiotic concepts.
WP2.1: Pre- and probiotics - in vitro
The aim of this WP is to develop novel synbiotic concepts for enhanced butyrate production using an in vitro cultural system. A four-stage continuous culture system for colonic microbes simulating the colon fermentation proceeding from the proximal to the distal part of colon will be used for production of fermentation products with selected bacterial strains and prebiotic substances (RS and AX). The fermentation products will be tested on human colonic epithelium in a physiological 2-compartment cell system with polarised, apical-basolateral oriented human colonic cells.
WP2.2: Pre- and probiotics mechanisms - in vivo animals
The aim of this WP is to test novel synbiotic concepts under in vivo conditions. Pre-, pro- and synbiotics selected on basis of the in vitro screening will be studied. The WSD diet without or with pre-, pro- or synbiotics will be fed to pigs for 3-4 weeks. During the experimental period, peripheral blood, urine and faecal samples will be collected weekly. At the end of the study, pigs will be euthanised, and digesta and tissue will be obtained from various parts of the gastrointestinal tract. Faecal samples will also be used for quantification of selected bacterial strains.
WP2.3: Colonic health – in vivo humans (Coordinator: Hendrik Vilstrup, AUH1)
The aim of this WP is to study the influence of colonic butyrate levels on parameters related to oxidative stress in the colonic mucosa. The study will be performed with healthy humans as a randomised double-blind placebo controlled crossover design with two test periods separated by a washout period. During the test periods, faecal, urine and blood samples will be taken at run-ins and at the end of the study. At run in, and at the end of each test period, mucosal biopsies will be taken from the rectum and medium sigmoideum.
WP2.4: Molecular biomarkers – gut health
The aim of this WP is to obtain a molecular understanding of enhanced butyrate production on expression of selected genes related to gut health and parameters related to epithelial integrity, immune function, oxidative stress and inflammation. This will provide an overview of functional relationships across matrices and enable the characterisation of compartment-specific metabolic signatures.
WP3: Insulin sensitivity
The objective of this cluster WP is to unravel the implication of butyrate on insulin sensitivity in skeletal muscle and adipose tissue.
WP3.1: Insulin sensitivity and metabolism in skeletal muscle and adipose tissue
The aim of this WP is to study the influence of colonic butyrate production on insulin sensitivity parameters related to the metabolism in adipose tissue and skeletal muscle. Subjects with the metabolic syndrome (MeS) (abdominal obesity, insulin resistance, dyslipidemia, elevated blood pressure) will be on the experimental diet for four weeks during which they will receive the fibre through different food items. We will use a crossover design with a washout period of 4 weeks between the 4 week intervention periods. The insulin sensitivity and a number of metabolic and inflammatory markers will be measured.
WP3.2: Mechanistic studies with multicatheterised pigs
The aim of this WP is to study the mechanism of action of colonic butyrate production on glucose metabolism and insulin economy. The diets to be investigated will be the WSD and two high fibre diets with added RS and AX, respectively. Pigs catheterised in the mesenteric artery, the portal vein and hepatic vein will be used as experimental models.
WP3.3: Molecular mechanistic studies
The aim of this WP is to study the molecular mechanisms related to whole body insulin sensitivity. Preclinical studies with models of diabetes with insulin resistance and impaired beta cell function will be used when exposed to a WSD diet and diets with added fibre from RS and AX.
WP3.4: Molecular biomarkers
The aims of this WP are to identify novel plasma and urine biomarkers for improved insulin sensitivity in response of enhanced butyrate production in the gut. Metabolomic analyses of urine and bloods from the human and animal studies will be performed, and state-of-the-art multiblock methods will be used to integrate the data in one common data modelling approach with the purpose of visualising metabolic events.
