The GUT-BRAIN study: Short-term effect of a high-fiber diet on gut-brain communication

Background. Based on recent experimental neuroscientific studies, it has been suggested that high-fiber diets, rich in naturally occurring prebiotics such as soluble fibers, might affect brain structure and functions through changes in the gut microbiome. However, due to a lack of evidence from randomized controlled trials in humans, it remains to be shown whether fibers affect brain structure and cognitive function through “bottom-up” metabolic mechanisms via the gut-brain axis. Aim. We therefore aim to elucidate whether there is a causal link between diet, gut microbial signalling and the brain. To do so, we are conducting a double-blind within-subject cross-over dietary intervention study with inulin as high-fiber supplement versus placebo. This study includes the analysis of blood-based biomarkers and stool-derived microbiota composition, as well as the assessment of task-based brain activation in food decision making and memory performance. Hypotheses. We hypothesize that supplementary high-fiber compared to placebo intake modulates food wanting and memory performance and its neuronal correlates. We further presume that changes in the gut microbial composition (e.g. higher α- and β-diversity) and in carbohydrate-specific metabolic pathways (e.g. short-chain fatty acid synthesis) may mediate potential effects of the high-fiber diet. Methods. Each participant (ntotal = 60, 18-45 years old) takes part in five experiment days out of which four include MRI sessions (Siemens Magnetom Prisma 3T) directly before and after the dietary intervention/placebo period. As dietary intervention, participants take 30g of inulin supplement (extracted from the chicory plant) daily for two weeks or a calorie-matched placebo supplement (maltodextrin) while maintaining their usual omnivorous diet. Food wanting and memory performance and related brain activity are assessed using functional magnetic resonance imaging (fMRI, 3T, TR 2000ms, 2mm³ isotropic). Briefly, participants have to indicate wanting of different food and, as contrast condition, art stimuli on an 8-point Likert scale. Memory performance is assessed after a delay of 20 minutes (fMRI) and after 12 weeks (behaviour). We further collect structural and diffusion-weighted images. Besides brain imaging, participants perform the Attentional Network Test. In addition, we monitor anthropometry, metabolic and emotional health makers with blood samples and questionnaires (e.g. WHO 5, BDI-II, GQLI, PANAS) as well as fecal samples to characterize microbial diversity (16S rRNA gene sequencing) and metabolic activity. Conclusions. This randomized controlled trial comprehensively determines the effects of a high-fiber dietary intervention on food wanting and neuronal correlates and whether these effects are mediated by changes in gut microbial composition and metabolism. Advantages of the study design are the within-subject contrasts which account for the large inter-individual differences in gut microbial composition and in the evaluation of food items. Further, we thoroughly control for hunger state, personal characteristics and other confounders. Art pictures as non-food control stimuli showed consistent activation of brain-areas related to wanting evaluation. Therefore, we propose our fMRI task as a robust and reliable tool to evaluate specific aspects of food wanting against other reward dimensions. This study will help to elucidate whether high-fiber diets affect body and brain and which underlying mechanisms mediate these effects

Metabolomics reveals effects of maternal smoking on endogenous metabolites from lipid metabolism in cord blood of newborns

Introduction: A general detrimental effect of smoking during pregnancy on the health of newborn children is well-documented, but the detailed mechanisms remain elusive. Objectives: Beside the specific influence of environmental tobacco smoke derived toxicants on developmental regulation the impact on the metabolism of newborn children is of particular interest, first as a general marker of foetal development and second due to its potential predictive value for the later occurrence of metabolic diseases. Methods: Tobacco smoke exposure information from a questionnaire was confirmed by measuring the smoking related metabolites S-Phenyl mercapturic acid, S-Benzyl mercapturic acid and cotinine in maternal urine by LC–MS/MS. The impact of smoking on maternal endogenous serum metabolome and children’s cord blood metabolome was assessed in a targeted analysis of 163 metabolites by an LC–MS/MS based assay. The anti-oxidative status of maternal serum samples was analysed by chemoluminiscence based method. Results: Here we present for the first time results of a metabolomic assessment of the cordblood of 40 children and their mothers. Several analytes from the group of phosphatidylcholines, namely PCaaC28:1, PCaaC32:3, PCaeC30:1, PCaeC32:2, PCaeC40:1, and sphingomyelin SM C26:0, differed significantly in mothers and children’s sera depending on smoking status. In serum of smoking mothers the antioxidative capacity of water soluble compounds was not significantly changed while there was a significant decrease in the lipid fraction. Conclusion: Our data give evidence that smoking during pregnancy alters both the maternal and children’s metabolome. Whether the different pattern found in adults compared to newborn children could be related to different disease outcomes should be in the focus of future studies

Microbial community functioning during plant litter decomposition

International audienceAbstract Microbial life in soil is fueled by dissolved organic matter (DOM) that leaches from the litter layer. It is well known that decomposer communities adapt to the available litter source, but it remains unclear if they functionally compete or synergistically address different litter types. Therefore, we decomposed beech, oak, pine and grass litter from two geologically distinct sites in a lab-scale decomposition experiment. We performed a correlative network analysis on the results of direct infusion HR-MS DOM analysis and cross-validated functional predictions from 16S rRNA gene amplicon sequencing and with DOM and metaproteomic analyses. Here we show that many functions are redundantly distributed within decomposer communities and that their relative expression is rapidly optimized to address litter-specific properties. However, community changes are likely forced by antagonistic mechanisms as we identified several natural antibiotics in DOM. As a consequence, the decomposer community is specializing towards the litter source and the state of decomposition (community divergence) but showing similar litter metabolomes (metabolome convergence). Our multi-omics-based results highlight that DOM not only fuels microbial life, but it additionally holds meta-metabolomic information on the functioning of ecosystems

Differences in cortical contractile properties between healthy epithelial and cancerous mesenchymal breast cells

Cell contractility is mainly imagined as a force dipole-like interaction based on actin stress fibers that pull on cellular adhesion sites. Here, we present a different type of contractility based on isotropic contractions within the actomyosin cortex. Measuring mechanosensitive cortical contractility of suspended cells among various cell lines allowed us to exclude effects caused by stress fibers. We found that epithelial cells display a higher cortical tension than mesenchymal cells, directly contrasting to stress fiber-mediated contractility. These two types of contractility can even be used to distinguish epithelial from mesenchymal cells. These findings from a single cell level correlate to the rearrangement effects of actomyosin cortices within cells assembled in multicellular aggregates. Epithelial cells form a collective contractile actin cortex surrounding multicellular aggregates and further generate a high surface tension reminiscent of tissue boundaries. Hence, we suggest this intercellular structure as to be crucial for epithelial tissue integrity. In contrast, mesenchymal cells do not form collective actomyosin cortices reducing multicellular cohesion and enabling cell escape from the aggregates

Metaproteomics and metabolomics analyses of chronically petroleum-polluted sites reveal the importance of general anaerobic processes uncoupled with degradation

Crude oil is one of the most important natural assets for humankind, yet it is a major environmental pollutant, notably in marine environments. One of the largest crude oil polluted areas in the word is the semi-enclosed Mediterranean Sea, in which the metabolic potential of indigenous microbial populations towards the large-scale chronic pollution is yet to be defined, particularly in anaerobic and micro-aerophilic sites. Here, we provide an insight into the microbial metabolism in sediments from three chronically polluted marine sites along the coastline of Italy: the Priolo oil terminal/refinery site (near Siracuse, Sicily), harbour of Messina (Sicily) and shipwreck of MT Haven (near Genoa). Using shotgun metaproteomics and community metabolomics approaches, the presence of 651 microbial proteins and 4776 metabolite mass features have been detected in these three environments, revealing a high metabolic heterogeneity between the investigated sites. The proteomes displayed the prevalence of anaerobic metabolisms that were not directly related with petroleum biodegradation, indicating that in the absence of oxygen, biodegradation is significantly suppressed. This suppression was also suggested by examining the metabolome patterns. The proteome analysis further highlighted the metabolic coupling between methylotrophs and sulphate reducers in oxygen-depleted petroleum-polluted sediments

Combining metagenomics with metaproteomics and stable isotope probing reveals metabolic pathways used by a naturally occurring marine methylotroph

A variety of culture-independent techniques have been developed that can be used in conjunction with culture-dependent physiological and metabolic studies of key microbial organisms, in order to better understand how the activity of natural populations influences and regulates all major biogeochemical cycles. In this study, we combined DNA-stable isotope probing with metagenomics and metaproteomics to characterize an as yet uncultivated marine methylotroph that actively incorporated carbon from 13C-labeled methanol into biomass. By metagenomic sequencing of the heavy DNA, we retrieved virtually the whole genome of this bacterium and determined its metabolic potential. Through protein-stable isotope probing, the RuMP cycle was established as the main carbon assimilation pathway, and the classical methanol dehydrogenase-encoding gene mxaF, as well as three out of four identified xoxF homologues were found to be expressed. This proof-of-concept study is the first in which theculture-independent techniques of DNA- and protein-stable isotope probing have been used to characterize the metabolism of a naturally-ocurring Methylophaga-like bacterium in the marine environment (i.e. M. thiooxydans L4) and thus provides a powerful approach to access the genome and proteome of uncultivated microbes involved in key processes in the environment

Mapping interactions with the chaperone network reveals factors that protect against tau aggregation.

A network of molecular chaperones is known to bind proteins ('clients') and balance their folding, function and turnover. However, it is often unclear which chaperones are critical for selective recognition of individual clients. It is also not clear why these key chaperones might fail in protein-aggregation diseases. Here, we utilized human microtubule-associated protein tau (MAPT or tau) as a model client to survey interactions between ~30 purified chaperones and ~20 disease-associated tau variants (~600 combinations). From this large-scale analysis, we identified human DnaJA2 as an unexpected, but potent, inhibitor of tau aggregation. DnaJA2 levels were correlated with tau pathology in human brains, supporting the idea that it is an important regulator of tau homeostasis. Of note, we found that some disease-associated tau variants were relatively immune to interactions with chaperones, suggesting a model in which avoiding physical recognition by chaperone networks may contribute to disease