Dietary-based gut flora modulation against Clostridium difficile onset

Clostridium difficile infection is a frequent complication of antibiotic therapy in hospitalised patients, which today is attracting more attention than ever and has led to its classification as a 'superbug'. Disruption of the composition of the intestinal microflora following antibiotic treatment is an important prerequisite for overgrowth of C. difficile and the subsequent development of an infection. Treatment options for antibiotic-associated diarrhoea and C. difficile-induced colitis include administration of specific antibiotics (e.g. vancomycin), which often leads to high relapse rates. More importantly, both the rate and severity of C. difficile-associated diseases are increasing, with new epidemic strains of C. difficile often implicated. For the prevention and treatment of antibiotic-associated diarrhoea and C. difficile infection, several probiotic bacteria such as selected strains of lactobacilli (especially Lactobacillus rhamnosus GG), Bifidobacterium longum, and Enterococcus faecium and the non-pathogenic yeast Saccharomyces boulardii have been used. Controlled trials indicate a benefit of S. boulardii and L. rhamnosus GG as therapeutic agents when used as adjuncts to antibiotics. However, the need for more well designed controlled trials with probiotics is explicit

Nutrition challenges ahead

The breakout session ‘Nutrition challenges ahead’ was held at the EFSA 2nd Scientific Conference ‘Shaping the Future of Food Safety, Together’ (Milan, Italy, 14–16 October 2015) to address the main problems in the area of nutrition to be faced in the 21st Century, both at a global and individual level. The nutrition challenges ahead are diverse and depend on agricultural, socioeconomic and individual factors. At a global level, food security, food sustainability and decreasing the impact of food production on climate change are of paramount importance. Decreasing the prevalence of obesity and related disorders, which may coexist with selected micronutrient deficiencies, is a major challenge for wealthy countries; for developing countries and rural food systems, fighting protein–energy malnutrition and micronutrient deficiencies is a priority. Diets based on a wide variety of nutrient-rich local plant foods (e.g. fruits, vegetables, whole grain cereals, vegetable oils, nuts) that contain moderate amounts of animal protein (preferably in the form of fish) and are low in saturated and trans-fatty acids, added sugars and sodium, are healthy, nutritious, sustainable and climate friendly. Creating an environment where such diets are also economically advantageous and convenient may be a part of a global solution to these nutritional challenges. Individuals, however, are unique regarding their genetic background, gut microbiota and health status. In addition, nutrition may already play a role in the development (and prevention) of disease very early in life. Thus, additional health benefits could be achieved by tailoring nutritional strategies to particular population subgroups or even individuals on the basis of current and future knowledge about the relationship between nutrients, genes, the microbiome and health. New technologies and food innovation may help in finding novel foods fit for purpose

Processed Animal Proteins from Insect and Poultry By-Products in a Fish Meal-Free Diet for Rainbow Trout: Impact on Intestinal Microbiota and Inflammatory Markers

Sustainability of aquaculture is tied to the origin of feed ingredients. In search of sustainable fish meal‐free formulations for rainbow trout, we evaluated the effect of Hermetia illucens meal (H) and poultry by‐product meal (P), singly (10, 30, and 60% of either H or P) or in combination (10% H + 50% P, H10P50), as partial replacement of vegetable protein (VM) on gut microbiota (GM), inflammatory, and immune biomarkers. Fish fed the mixture H10P50 had the best growth performance. H, P, and especially the combination H10P50 partially restored α‐diversity that was negatively affected by VM. Diets did not differ in the Firmicutes:Proteobacteria ratio, although the relative abundance of Gammaproteobacteria was reduced in H and was higher in P and in the fishmeal control. H had higher relative abundance of chitin‐degrading Actinomyces and Bacillus, Dorea, and Enterococcus. Actinomyces was also higher in H feed, suggesting feed‐chain microbiome transmission. P increased the relative abundance of protein degraders Paeniclostridium and Bacteroidales. IL‐1β, IL‐10, TGF‐β, COX‐2, and TCR‐β gene expression in the midgut and head kidney and plasma lipopolysaccharide (LPS) revealed that the diets did not compromise the gut barrier function or induce inflammation. H, P, and H10P50 therefore appear valid protein sources in fishmeal‐free aquafeeds

Low-Molecular-Weight Seaweed-Derived Polysaccharides Lead to Increased Faecal Bulk but Do Not Alter Human Gut Health Markers

Seaweeds are potentially sustainable crops and are receiving significant interest because of their rich bioactive compound content; including fatty acids, polyphenols, carotenoids, and complex polysaccharides. However, there is little information on the in vivo effects on gut health of the polysaccharides and their low-molecular-weight derivatives. Herein, we describe the first investigation into the prebiotic potential of low-molecular-weight polysaccharides (LMWPs) derived from alginate and agar in order to validate their in vivo efficacy. We conducted a randomized; placebo-controlled trial testing the impact of alginate and agar LWMPs on faecal weight and other markers of gut health and on composition of gut microbiota. We show that these LMWPs led to significantly increased faecal bulk (20–30%). Analysis of gut microbiome composition by sequencing indicated no significant changes attributable to treatment at the phylum and family level, although FISH analysis showed an increase in Faecalibacterium prausnitzii in subjects consuming agar LMWP. Sequence analysis of gut bacteria corroborated with the FISH data, indicating that alginate and agar LWMPs do not alter human gut microbiome health markers. Crucially, our findings suggest an urgent need for robust and rigorous human in vivo testing—in particular, using refined seaweed extracts

Mathematically modelling the dynamics of cholesterol metabolism and ageing

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the UK. This conditionbecomes increasingly prevalent during ageing; 34.1% and 29.8% of males and females respectively, over 75years of age have an underlying cardiovascular problem. The dysregulation of cholesterol metabolism isinextricably correlated with cardiovascular health and for this reason low density lipoprotein cholesterol(LDL-C) and high density lipoprotein cholesterol (HDL-C) are routinely used as biomarkers of CVD risk. Theaim of this work was to use mathematical modelling to explore how cholesterol metabolism is affectedby the ageing process. To do this we updated a previously published whole-body mathematical model ofcholesterol metabolism to include an additional 96 mechanisms that are fundamental to this biologicalsystem. Additional mechanisms were added to cholesterol absorption, cholesterol synthesis, reversecholesterol transport (RCT), bile acid synthesis, and their enterohepatic circulation. The sensitivity of themodel was explored by the use of both local and global parameter scans. In addition, acute cholesterolfeeding was used to explore the effectiveness of the regulatory mechanisms which are responsible formaintaining whole-body cholesterol balance. It was found that our model behaves as a hypo-responderto cholesterol feeding, while both the hepatic and intestinal pools of cholesterol increased significantly.The model was also used to explore the effects of ageing in tandem with three different cholesterolester transfer protein (CETP) genotypes. Ageing in the presence of an atheroprotective CETP genotype,conferring low CETP activity, resulted in a 0.6% increase in LDL-C. In comparison, ageing with a genotypereflective of high CETP activity, resulted in a 1.6% increase in LDL-C. Thus, the model has illustrated theimportance of CETP genotypes such as I405V, and their potential role in healthy ageing

Diet : Microbe interactions - ecosystem support

Recent metagenomic studies are confirming what pioneers in gut microbiology have long said, that diet:microbe interactions in the gut impact on human health and disease. The gut microbiota appear to regulate various physiological functions including host energy metabolism, immune homeostasis, and brain development and function. The gut microbiota produces a range of biologically active metabolites, not least, short chain fatty acids, small phenolic compounds derived from polyphenol metabolism, and, immunologically and neurologically active amino acid derivatives such as gamma-aminobutyric acid, serotonin and dopamine. Microbiota activities also control systemic tryptophan metabolism and peripheral concentrations of potentially harmful metabolites derived from choline and carnitine metabolism, notably the cardiotoxicant trimethylamine-N-oxide. The gut microbiota also determines the profile of bile acids returning to the liver through the enterohepatic circulation, important cell signalling molecules involved in various physiological functions, including host energy metabolism and immune function. Diet in large part regulates these important microbiota physiological services and dietary constituents, particularly the relative proportions of fermentable fiber and plant polyphenols on the one hand, and refined sugars, fat and animal protein, on the other, appear to critically determine the flux of either beneficial or potentially harmful metabolites from the gut. This presentation will discuss how diet regulates both the composition and metabolic output of the gut microbiota constituting, in effect, ecosystem support, not just for the gut microbiota, but for the greater human:microbe ecosystem as a whol

Measuring the metabolic output of the human gut microbiota: implications for chronic disease risk

Recent metagenomic studies have highlighted significant associations between dysregulation of the intestinal microbiome and chronic disease risk in humans. Indeed, many diet and life-style associated diseases, obesity, type 2 diabetes, autoimmune diseases and certain cancers, all appear to possess characteristic profiles of gut bacteria and dysbiosys at the genetic level, with differences both in microbial diversity and relative abundance of important groups of gut bacteria compared to healthy individuals. However, clear links between aberrant microbiota composition and disease mechanisms in the host remain elusive. This presentation will focus on metabolic links between host and microbiome, metabolic links which appear to be altered in disease states and which in turn appear to be modifiable through dietary intervention. Interactions between specific dietary components, e.g. fermentable fibers/prebiotics, polyphenols and aromatic amino acids, appear to strongly influence both the composition and metabolic output of the gut microbiota and modify metabolites of known importance in physiological pathways regulating host metabolism and immune function. Similarly, high resolution MS based metabolomics is presenting a detailed picture of host:microbiome co-metabolism of many complex dietary components, providing novel biomarkers of intake and new putative therapeutic targets. Using data from model systems and human dietary interventions, the ability of host:microbiota co-metabolism to impact significantly on the risk of metabolic disease will be discussed using examples combining microbiome 16S rRNA sequence based profiling and biofluid targeted and untargeted MS based metabolomics

Intestinal microbiota, diet and health

Recent omics level studies are confirming what pioneers in gut microbiology have been saying for some time, that diet:microbe interactions impact on human health and disease risk (Midtvedt, 1974; Rowland, 1988). The post genomics technologies of metagenomics and metabolomics are decoding the detailed cross-talk between the structure and function of the intestinal microbiome and host physiology, with diet:microbe interactions now shown to impact on the risk of cardio-metabolic disease, cancers, immune diseases and psychiatric disorders (Nicholson et al, 2012). The gut microbiota is becoming recognised as an important metabolic and immunological organ in its own right, intricately linked to the functioning of other organs most notably the liver, adipose tissue and the brain. Evidence mainly from animal studies describe important roles for gut microbiota metabolites and/or microbiota immunological regulation of metabolic and inflammatory pathways critical for maintenance of host defences. Indeed, such studies hint at common underlying pathological processes linking diet:microbe interactions in the gut with a spectrum of chronic diseases along the gut:liver:fat:brain axis. Indeed, different aspects of this gut:liver:fat:brain axis are currently receiving much attention for their role in obesity, the diseases of obesity (cardiovascular-disease, type 2 diabetes, non-alcoholic fatty liver disease, Alzheimer’s disease) and psychiatric conditions such as autism, Schizophrenia and importantly, depression. Many of these diseases are characterised by loss of metabolic homeostasis and unresolved systemic inflammation. While the gut microbiota have been shown to produce toxic compounds for example trimethylamine-N-oxide and N-nitroso compounds derived from amino acid/protein fermentation n the gut, many microbial metabolites impact beneficially on host health, especially those which derive from the breakdown and fermentation of plant macromolecules, fibers and polyphenols. Short chain fatty acids and small phenolic compounds derived from colonic carbohydrate fermentation and plant polyphenol catabolism respectively, have been shown to play a critical role in establishment and maintenance of host defences, especially immune function (both within the gut and systemically) and gut barrier integrity. Moreover, plant fibers and polyphenols can influence the quantity of bile acids entering the distal ileum and colon, and also the profile of bile salt hydrolyzing bacteria therein, and thus may influence microbial involvement in the enterohepatic circulation of bile acids. Bile acids, apart from their role in regulating fat uptake are now being recognised for their important cell signalling role, acting as ligands for nuclear receptors like FXR, VDR, PXR, CAR and g-coupled receptors like TGR5, which in turn regulate inflammation, glucose and lipid metabolism, nutrient absorption, intestinal permeability and thermogenesis. Gut bacteria also produce biologically active compounds like B vitamins (niacin and folate for example), vitamin K, and conjugated linoleic acids, all powerful bioactive agents targeting regulation of various inflammatory and metabolic pathways in man. Moreover, both the physiological concentrations of these compounds and their biological activity change throughout life, driven both by diet and successional development of the gut microbiota, identifying diet:microbe interactions as an important extra-genomic epigenetic mediator capable of impacting on physiological processes linked to chronic disease risk and the ageing process itself. Recent studies indicate that processes within the gut play a critical role in the persistent low grade systemic inflammation common to many chronic human diseases associated with modern diet and life-style. Increased intestinal permeability leads to translocation of inflammatory molecules such as lipopolysaccharide, which then act as continuous triggers for unresolved systemic inflammation. This intestinal permeability and emergence of aberrant microbiota profiles is strongly influenced by diet, with high fat - low fiber diets (the modern or Western style diet) contributing to gut wall permeability. Conversely, ancestral or traditional dietary patterns high in fermentable fiber, prebiotics, fruit and vegetables (and indeed certain probiotic or fermentative microorganisms) support microbiome structure and function and improve gut barrier integrity (Figure 1). A number of gut bacteria, including species of bifidobacteria and lactobacilli commonly used as probiotics, SCFA and the bile acid regulated nuclear receptor, FXR, have all been shown to control gut permeability via induction of tight junction proteins between epithelial cells. Similarly gut inflammation and oxidative damage play their part in gut “leakiness”, and are themselves impacted by both diet and the gut microbiome. Indeed, this diet induced intestinal damage and gut permeability, which is also characteristic of certain chronic disease states like obesity strongly mirrors the gut leakiness and chronic low grade systemic inflammation observed in the elderly, and at least in models of ageing, harbingers unresolved inflammation, metabolic derangement, diabetes and eventually death (Rena et al. 2012). Of course the ancients knew this all along - “death sits in the bowel” Hippocrates c. 400 BC. However, we are now providing the mechanistic understanding of how the gut microbiota may constitute a lynch-pin upon which the destructive degenerative processes of aberrant metabolic and inflammatory pathway activation are held at bay until overwhelmed by advancing age or aberrant diet. When this occurs, or what chronic disease expresses itself, is of course determined by host genetic predisposition, but it appears that diet:microbiota interactions in the gut contribute significantly to the environmental pressure driving these metabolic and inflammatory disease processes. Diet is one disease risk factor we can modify, and understanding on the one hand, what dietary components contribute to disease risk, and on the other hand, those which reduce disease risk is critical if we are to reduce the burden of chronic non-communicable diseases. Adherence to the Mediterranean style diet has been proven to protect against these chronic non-communicable diseases and improve mental well-being (Bonaccio et al. 2013) and indeed, recent studies are showing that components of the Mediterranean diet may mediate, at least part of their protective effects, through the gut microbiome (Figure 1, Tuohy and Del Rio, 2014). This lecture will provide an insight into recent studies illustrating how diet:microbe interactions in the gut not only contribute to chronic disease risk, but also hold great potential of reducing the socioeconomic impact of these diseases through rational modulation of dietary patterns throughout life