How do fermentation metabolites of different inulin-derivate products affect gut inflammation, glucose homeostasis and food intake regulation?

Abstract

Consumption of prebiotics such as inulin-type fructans (oligofructose and inulin) are important for the modulation of the gut microbiota. Indeed, oligofructose and inulin selectively stimulate the growth of health-stimulating intestinal bacteria (Bifidobacterium spp. and Lactobacillus spp.). These bacteria ferment oligofructose and inulin to produce short-chain fatty acids (SCFA). These SCFA exert a positive effect on the host, for example positive effects on gut inflammation, food intake and glucose homeostasis. There were several aims to achieve within this master’s thesis. The first was to compare the fermentation capacity of five different oligofructose and inulin-based products provided by BENEO-Orafti, S.A (Orafti®OLX, Orafti®OPS, Orafti®SIPX, Orafti®SIPS and Orafti®IPS). To do this, an in vitro batch fermentation was performed and fermentation juices were collected after 12 hours, 24 hours and 48 hours of fermentation. The second was to study the effects of these products on production of SCFA and modulation of the microbiota. The third objective was to evaluate the immune response induced by the filtered fermentation juice of the studied ingredients. This goal was not achieved due to the circumstances (covid-19). Finally, the fourth objective was to compare the effect of the filtered fermentation juice samples on glucose homeostasis and food intake. In order to this, the capacity of the filtered fermentation juice samples to stimulate the secretion of GLP-1 was studied. The results obtained showed that Orafti®OLX (70% of oligofructose) induced the least gas production compared to the other products and had the fastest fermentation. Butyrate proportion was the highest with Orafti®OPS (95% of oligofructose) and the lowest with Orafti®OPS (70% of oligofructose). Maximum gas production and butyrate were mainly linked to the purity of the products while the rate of fermentation was influenced by degree of polymerization and the purity of the studied ingredients. Concerning food intake and glucose homeostasis, the filtered fermentation juice samples (dilution ½ and ¼) and the filtered samples containing no products (blank mucin) induced the same GLP-1 secretion after 12 hours of fermentation. After 24h of fermentation, only Orafti®IPS at dilution ½ had induced a higher GLP-1 secretion compared to blank mucin. These results are opposite to the current studies, which show a positive impact of inulin-type fructans on GLP-1 secretion. Furthermore, there were contradictions between SCFA production results obtained by HPLC and bacterial communities abundance performed by qPCR. Furthermore, the latter results go against expectations. For those reasons, it would be recommendable that GLP-1 secretion experiment as well as bacterial abundance measurements to be repeated.