In vitro Selection of Probiotics for Microbiota Modulation in Normal-Weight and Severely Obese Individuals: Focus on Gas Production and Interaction With Intestinal Epithelial Cells

The intestinal microbiota plays important roles in the maintenance of health. Strategies aiming at its modulation, such as probiotics, have received a deal of attention. Several strains have been studied in different in vitro models; however, the correlation of results obtained with the in vivo data has been limited. This questions the usefulness of such in vitro selection models, traditionally relying on over-simplified tests, not considering the influence of the accompanying microbiota or focusing on microbiota composition without considering functional traits. Here we assess the potential of six Bifidobacterium, Lactobacillus and Lacticaseibacillus strains in an in vitro model to determine their impact on the microbiota not just in terms of composition but also of functionality. Moreover, we compared the responses obtained in two different population groups: normal-weight and severely obese subjects. Fecal cultures were conducted to evaluate the impact of the strains on specific intestinal microbial groups, on the production of short-chain fatty acids, and on two functional responses: the production of gas and the interaction with human intestinal epithelial cells. The response to the different probiotics differed between both human groups. The addition of the probiotic strains did not induce major changes on the microbiota composition, with significant increases detected almost exclusively for the species added. Higher levels of gas production were observed in cultures from normal-weight subjects than in the obese population, with some strains being able to significantly reduce gas production in the latter group. Moreover, in obese subjects all the Bifidobacterium strains tested and Lacticaseibacillus rhamnosus GG were able to modify the response of the intestinal cells, restoring values similar to those obtained with the microbiotas of normal-weight subjects. Our results underline the need for the screening and selection of probiotics in a target-population specific manner by using appropriate in vitro models before enrolling in clinical intervention trials.The present work was mainly financed by the project AGL2013-43770-R (receiving funds from the Ministry of Economy and Competitiveness—MINECO and the European Union FEDER funds), and partly by projects AGL2017-83653-R (AEI/FEDER, UE), and RTI2018-098288-B-I00 (MCIU/AEI/FEDER, UE) and by a contract with the company Takanashi Milk Products (Yokohama, Japan). AN was the recipient of a predoctoral contract granted by MINECO (reference BES-2014-068796). SA is currently financed by a postdoctoral Juan de la Cierva contract (Ministry of Science, Innovation and Universities, Spain, ref. IJCI-2017-32156) and NS is currently the recipient of a postdoctoral contract awarded by the Fundación para la Investigación y la Innovación Biosanitaria del Principado de Asturias (FINBA)

Probiotic-Induced Modulation of Microbiota Composition and Antibiotic Resistance Genes Load, an In Vitro Assessment

The imbalance of the gut microbiota (GM) is known as dysbiosis and is associated with disorders such as obesity. The increasing prevalence of microorganisms harboring antibiotic resistance genes (ARG) in the GM has been reported as a potential risk for spreading multi-drug-resistant pathogens. The objective of this work was the evaluation, in a fecal culture model, of different probiotics for their ability to modulate GM composition and ARG levels on two population groups, extremely obese (OB) and normal-weight (NW) subjects. Clear differences in the basal microbiota composition were observed between NW and OB donors. The microbial profile assessed by metataxonomics revealed the broader impact of probiotics on the OB microbiota composition. Also, supplementation with probiotics promoted significant reductions in the absolute levels of tetM and tetO genes. Regarding the blaTEM gene, a minor but significant decrease in both donor groups was detected after probiotic addition. A negative association between the abundance of Bifidobacteriaceae and the tetM gene was observed. Our results show the ability of some of the tested strains to modulate GM. Moreover, the results suggest the potential application of probiotics for reducing the levels of ARG, which constitutes an interesting target for the future development of probiotics.The present work was funded by project AGL2017-83653-R (AEI/FEDER, UE), by the project AYUD/2021/ 50981 from the Principality of Asturias, to support the activity of their research groups. The authors declare that this study has also received funding from Takanashi Milk Products (Yokohama, Japan). The funder had the following involvement with the study: metataxonomic analyses and review of the manuscript. S.A. was financed by a postdoctoral Juan de la Cierva contract (Ministry of Science, Innovation and Universities, Spain, ref. IJCI-2017-32156). A.M.N., S.S. and S.A. are currently the recipient of contracts awarded by the Fundación para la Investigación Biosanitaria de Asturias (FINBA).Peer reviewe

Human Lactobacillus Strains from the Intestine can Suppress IgE-Mediated Degranulation of Rat Basophilic Leukaemia (RBL-2H3) Cells

Mast cells play a critical role in immunoglobulin E (IgE)-mediated allergic diseases, and the degranulation of mast cells is important in the pathogenesis of these diseases. A disturbance of the intestinal microflora, especially of endogenous lactic acid bacteria, might be a contributing factor for IgE-mediated allergic diseases. Additional knowledge regarding the interaction of human intestinal Lactobacilli with mast cells is still necessary. Twenty-three strains of Lactobacilli, including commercial and reference strains and strains from the human intestine, were tested for their ability to regulate degranulation of cells from rat basophilic leukemia RBL-2H3 cells (RBL-2H3) in vitro based on a β-hexosaminidase release assay. Each of the tested Lactobacilli characteristically suppressed IgE-mediated degranulation of RBL-2H3 cells, and Lactobacillus GG showed the strongest inhibitory effect on the cells. Furthermore, the bacteria isolated from the human intestine significantly suppressed degranulation of RBL-2H3 cellsin comparison with the reference strains. These results suggest that Lactobacilli, particularly those from the human intestine, can affect the activation of mast cells in a strain-dependent manner. Further study should be conducted to analyse the understanding mechanism

Species- and Age/Generation-Dependent Adherence of Bifidobacterium bifidum to Human Intestinal Mucus In Vitro

Adhesion to intestinal mucus is the first event in the process by which intestinal microbes colonize the intestine. It plays a critical role in the initiation of interactions between gut microbes and host animals. Despite the importance, the adhesion properties of probiotics are generally characterized using porcine mucin; adhesion to human mucus has been poorly characterized. In the present study, human intestinal mucus samples were isolated from 114 fecal samples collected from healthy infants and adults. In initial screening, four out of the 13 beneficial microbes tested, including the type strain of Bifidobacterium bifidum, B. bifidum TMC3115, Lacticaseibacillus rhamnosus GG, and Bifidobacterium animalis subsp. lactis Bb12, showed strong adhesion abilities to human mucus. The type strain of B. bifidum and TMC3115 adhered more strongly to neonatal and infant mucus than to adult mucus, while L. rhamnosus GG and B. lactis Bb12 adhered more strongly to adult mucus than to infant mucus. Similar results were obtained for ten additional strains of B. bifidum. In conclusion, age/generation-related differences were observed in the adhesion properties of B. bifidum and other strains. A deeper symbiotic relationship may exist between infants, particularly neonates, and B. bifidum based on its enhanced adhesion to neonatal intestinal mucus

Effect of Probiotic Bifidobacterium bifidum TMC3115 Supplementation on Psychosocial Stress Using a Sub-Chronic and Mild Social Defeat Stress in Mice

With the accumulation of knowledge on the relation between psychological stress and gut microbiota, there is growing interest in controlling stress and/or mood disorders via probiotic supplementation. We aimed to examine the effect of probiotic Bifidobacterium bifidum TMC3115 (TMC3115) supplementation using a sub-chronic and mild social defeat stress murine model in this study. TM3115 supplementation maintained body weight gain and alleviated a polydipsia-like symptom induced by the stress. In the analyses of fecal and cecal bacterial profiles, expansions of Proteobacteria in stressed mice and increases in Actinobacteria and Bifidobacterium in mice supplemented with TMC3115 were observed. There was no marked difference in the diversity of cecal bacteria between the tested mice. Elevated serum levels of inflammatory markers such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 were observed in the stressed mice, while TMC3115 only reduced the IL-6 level. These findings suggest that TMC3115 supplementation confers tolerance to psychosocial stress in the host through modulation of the gut microbiota and alleviation of stress-induced inflammatory responses. Furthermore, it may be expected to exert prevention and treatment of disorders related to peripheral IL-6, including depression

Human Lactobacillus Strains from the Intestine can Suppress IgE-Mediated Degranulation of Rat Basophilic Leukaemia (RBL-2H3) Cells

Mast cells play a critical role in immunoglobulin E (IgE)-mediated allergic diseases, and the degranulation of mast cells is important in the pathogenesis of these diseases. A disturbance of the intestinal microflora, especially of endogenous lactic acid bacteria, might be a contributing factor for IgE-mediated allergic diseases. Additional knowledge regarding the interaction of human intestinal Lactobacilli with mast cells is still necessary. Twenty-three strains of Lactobacilli, including commercial and reference strains and strains from the human intestine, were tested for their ability to regulate degranulation of cells from rat basophilic leukemia RBL-2H3 cells (RBL-2H3) in vitro based on a β-hexosaminidase release assay. Each of the tested Lactobacilli characteristically suppressed IgE-mediated degranulation of RBL-2H3 cells, and Lactobacillus GG showed the strongest inhibitory effect on the cells. Furthermore, the bacteria isolated from the human intestine significantly suppressed degranulation of RBL-2H3 cellsin comparison with the reference strains. These results suggest that Lactobacilli, particularly those from the human intestine, can affect the activation of mast cells in a strain-dependent manner. Further study should be conducted to analyse the understanding mechanism

Sharing of human milk oligosaccharides degradants within bifidobacterial communities in faecal cultures supplemented with Bifidobacterium bifidum

Gut microbiota of breast-fed infants are generally rich in bifidobacteria. Recent studies show that infant gut-associated bifidobacteria can assimilate human milk oligosaccharides (HMOs) specifically among the gut microbes. Nonetheless, little is known about how bifidobacterial-rich communities are shaped in the gut. Interestingly, HMOs assimilation ability is not related to the dominance of each species. Bifidobacterium longum susbp. longum and Bifidobacterium breve are commonly found as the dominant species in infant stools; however, they show limited HMOs assimilation ability in vitro. In contrast, avid in vitro HMOs consumers, Bifidobacterium bifidum and Bifidobacterium longum subsp. infantis, are less abundant in infant stools. In this study, we observed altruistic behaviour by B. bifidum when incubated in HMOs-containing faecal cultures. Four B. bifidum strains, all of which contained complete sets of HMO-degrading genes, commonly left HMOs degradants unconsumed during in vitro growth. These strains stimulated the growth of other Bifidobacterium species when added to faecal cultures supplemented with HMOs, thereby increasing the prevalence of bifidobacteria in faecal communities. Enhanced HMOs consumption by B. bifidum-supplemented cultures was also observed. We also determined the complete genome sequences of B. bifidum strains JCM7004 and TMC3115. Our results suggest B. bifidum-mediated cross-feeding of HMOs degradants within bifidobacterial communities