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NutrInsight • Satiety: News Insights
Satiety: new inSightS
4 MECHANISMS oF APPETITE REguLATIoN: A RoLE FoR THE guT MICRoBIoTA?
Pr Nathalie Delzenne, Head of the Research Group in Metabolism and Nutrition, Louvain Drug Research Institute, Université Catholique de Louvain, Belgium
In ideal conditions, the 1014 bacteria that colonize our gut, called the gut microbiota, live in symbiosis with the host, and regulate important physiological functions, such as immunity and interactions of the gut-brain axis. They are classified into phyla, inside which are included several bacterial family, genders, and species: Firmicutes (including Lactobacilli), Bacteroidetes (including Prevotella or Bacteroides), Actinobacteria (including Bifidobacterium).
Bacteroidetes and firmicutes constitute over 90% of the known phylogenetic categories and dominate the distal gut microbiota. There is substantial diversity of the gut microbiome between healthy individuals. This difference is especially large among infants but the gut microbiome converges to more similar phyla in later life [Qin et al., 2010]. The enterotypes (variants of gut microbial communities) are strongly associated with long- term diets, particularly with the intake of protein and animal fat (Bacteroides) vs. carbohydrates (Prevotella) [Wu et al., 2011]. Individual host properties, such as body mass index, age, or gender cannot explain the total enterotypes but marker genes or functional modules can be identified for each of these characteristics [Arumugam et al., 2011].
4.1 gut microbiota and appetite
Is there a link between the gut microbiota and appetite?
Recent experimental data reveal the existence of links between the gut microbiota and expressions of appetite. For example, it has been shown that evening meals rich in dietary fibres containing non-digestible/fermentable carbohydrates (CHO), such as whole grain barley kernel, reduce appetite on the following day in human consumers [Johansson et al., 2013]. This effect is associated with an increase in the satiety peptide GLP-1 and a decrease in fasting serum free fatty acids (FFA). These effects are possibly mediated through gut microbial fermentation of the indigestible CHO. In rats, serum ghrelin (a hormone that stimulates food intake) levels correlate negatively, whereas serum leptin (a hormone positively associated with long-term satiety) levels correlate positively with Bifidobacterium and Lactobacillus [Queipo-Ortuno et al., 2013]. These associations between gut microbiota and appetite-regulating hormones may be important in terms of satiety and host metabolism.
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