The Fiberdia study: Effects of inulin-type fructans on gut microbiota and regulation of blood glucose and appetite in type 2 diabetes: A randomised, placebo-controlled crossover trial

Abstract

Compared to a healthy population, the gut bacteria in type 2 diabetes appear to present with a deviating composition. However, clinical trials report beneficial effects of prebiotic fibres on the composition of gut bacteria and regulation of gut hormones, blood glucose and appetite in non-diabetic populations. Although such responses could benefit patients with type 2 diabetes in particular, studies of the potential role of prebiotic fibres in this population are scarce. This thesis includes data from a randomised and placebo controlled crossover study investigating the effects of treatment with 16 g inulin-type fructans per day for six weeks in patients with type 2 diabetes. We aimed to investigate changes in faecal gut bacteria and short-chain fatty acids. Furthermore, we wanted to evaluate changes in glycaemic regulation and responses of the gut hormones ghrelin, PYY (peptide YY), glucagon-like peptide-1 (GLP-1), and GLP-2 to a standardised mixed meal. We also aimed to investigate changes in subjective ratings of appetite and energy intake during a test lunch with unrestricted servings of food. The prebiotics induced moderate changes in the composition of faecal bacteria, with the most prominent effect being an increased concentration of bifidobacteria. Faecal concentrations of total short-chain fatty acids, acetic acid, and propionic acid also increased significantly after prebiotic consumption compared to placebo. The prebiotics had no effect on the concentration of butyric acid or the overall bacterial diversity. Moreover, the prebiotics did not positively affect concentrations of glucose, insulin, gut hormones, appetite ratings or energy intake. Our findings suggest a moderate potential of inulin-type fructans to improve the bacterial composition in the gut and to increase bacterial fermentation in type 2 diabetes. However, the results do not support a role for inulin-type fructans in regulation of gut hormones, blood glucose or appetite in this population.