Abstract
Few studies have evaluated in vivo the impact of food structure on digestion, absorption of nutrients and on microbiota composition and metabolism. In this study we evaluated in rat the impact of two structures of protein emulsion in food on gut microbiota, luminal content composition, and intestinal characteristics. Rats received for 3 weeks two diets of identical composition but based on lipid-protein matrices of liquid fine (LFE) or gelled coarse (GCE) emulsion. LFE diet led to higher abundance, when compared to the GCE, of Lactobacillaceae (Lactobacillus reuteri) in the ileum, higher β-diversity of the caecum mucus-associated bacteria. In contrast, the LFE diet led to a decrease in Akkermansia municiphila in the caecum. This coincided with heavier caecum content and higher amount of isovalerate in the LFE group. LFE diet induced an increased expression of (i) amino acid transporters in the ileum (ii) glucagon in the caecum, together with an elevated level of GLP-1 in portal plasma. However, these intestinal effects were not associated with modification of food intake or body weight gain. Overall, the structure of protein emulsion in food affects the expression of amino acid transporters and gut peptides concomitantly with modification of the gut microbiota composition and activity. Our data suggest that these effects of the emulsion structure are the result of a modification of protein digestion properties.
Highlights
A substantial fraction of western diet incorporates processed or reconstituted food, which may alter the ingredient structure without substantially changing the composition of the food
The present study is among the first ones demonstrating that the structure of protein emulsion impacts microbiota and nutrient handling all along the distal gastro intestinal tract in rats
In intra-duodenal infusion experiments in humans, an increase in the fat emulsion droplet size induced a decrease in the lipid absorption rate together with an increase in the release of the gut peptides cholecystokinin (CCK) and peptide YY (PYY) associated with satiety increase [4]
Summary
A substantial fraction of western diet incorporates processed or reconstituted food, which may alter the ingredient structure without substantially changing the composition of the food. The spatial arrangement of food constituents (food structure) is notably determined by food processing and regulates digestion mostly through modifications of the accessibility of digestive enzymes [1]. Food structure has been mostly studied by in vitro digestion, few in vivo published studies showed that food structure may regulate transit time, nutrient sensing and absorption in the gastrointestinal tract as well as satiety and post-prandial metabolism [2]. In humans a coarse fat emulsion delivered intra-gastrically, decreased lipolysis in the duodenum relatively to a fine fat emulsion [3]. In intra-duodenal infusion experiments in humans, an increase in the fat emulsion droplet size induced a decrease in the lipid absorption rate together with an increase in the release of the gut peptides cholecystokinin (CCK) and peptide YY (PYY) associated with satiety increase [4]. Mice fed for 18 weeks a standard powder diet display increased body weight and fat mass owing to an increased food intake relative to mice fed an identical diet in pellets, indicating a crucial role of diet macrostructure on food consumption [6]
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