In Vitro Characterization of the Impact of Different Substrates on Metabolite Production, Energy Extraction and Composition of Gut Microbiota from Lean and Obese Subjects

Abstract

The aim of this study was to investigate the effect of galacto-oligosaccharides, lactulose, apple fiber and sugar beet pectin on the composition and activity of human colonic microbiota of lean and obese healthy subjects using an in vitro model of the proximal colon: TIM-2. Substrate fermentation was assessed by measuring the production of short-chain and branched-chain fatty acids, lactate and ammonia and by studying the composition of the bacterial communities over time. The results suggest that energy harvest (in terms of metabolites) of lean and obese microbiotas is different and may depend on the fermentable substrate. For galacto-oligosaccharides and lactulose, the cumulative amount of short-chain fatty acids plus lactate produced in TIM-2 was lower in the fermentation experiments with the lean microbiota (123 and 155 mmol, respectively) compared to the obese (162 and 173 mmol, respectively). This was reversed for the pectin and the fiber. The absolute amount produced of short-chain fatty acids including lactate was higher after 72 h in the fermentation experiments with apple fiber-L (108 mmol) than with apple fiber-O (92 mmol). Sugar beet-L was also higher (130 mmol) compared to sugar beet-O (103 mmol). Galacto-oligosaccharides and lactulose boosted the balance of health-promoting over toxic metabolites produced by the microbiota from obese subjects. Firmicutes were more predominant in the inoculum prepared from feces of obese subjects compared to lean subjects. The average abundance at time zero was 92% and 74%, respectively. On the other hand, Bacteroidetes were more dominant in the microbiota prepared with homogenates from lean subjects with an average abundance of 22% compared with the microbiota prepared with homogenates from obese subjects (3.6%). This study brings evidence that different fermentable carbohydrates are fermented differently by lean and obese microbiotas, which contributes to the understanding of the role of diet and the microbiota in tackling obesity.

The intestinal microbiota, energy balance, and malnutrition: emphasis on the role of short-chain fatty acids

“…It showed that substrate type determined which of the two microbial compositions had the highest fermenting capacity. Whereas the obesity-associated microbiota produced more SCFAs in response to galacto-oligosaccharides and lactulose, the opposite was true for pectin and fibers [28].…”

Selection of fast and slow growing bacteria from fecal microbiota using continuous culture with changing dilution rate

“…The fecal samples were diluted with protectant-containing solution 1:4 as described in Adamberg et al [23] and kept at −80°C until use. Before cultivation experiment, the fecal slurries were thawed, and pooled in equal volumes as also reported earlier by Aguirre et al [24] The OW pool for inoculation consisted of seven fecal slurries of the OW children (4 boys, 3 girls) and the NW pool consisted of six fecal slurries of the NW children (2 boys, 4 girls). The average age and range of the fecal donors were 10.6 ± 2.4 (range 7–14 years) and 9.4 ± 4.7 (range 4.5–15 years) for OW and NW fecal pools, respectively.…”

The art of targeting gut microbiota for tackling human obesity

“…Interestingly, increasing evidence suggests that the gut microbiota plays an important role in human obesity (Harris et al 2012;Aguirre et al 2014;Guida and Venema 2015). Several important discoveries have been made from which we highlight: (i) the impact of dietary components on the composition of gut microbiota.…”

“…Nearly 1.5 kg of bacteria reside in the human gut (Nicholson et al 2005), and approximately 50 % of the wet weight of fecal biomass in humans is estimated to come from bacterial cells (Zhao 2013). The identification and analysis of the metabolic capacity and phylogeny from these gut microbial communities unfold specific characteristics in healthy and unhealthy subjects (Ramakrishna 2013;Aguirre et al 2014). Therefore, it has been possible to propose a potential causative role for the microbiota in several types of disorders (Faith et al 2014).…”