Diet: Microbiota Interaction in the Gut-Focus on Amino Acid Metabolism

This study aims to measure the impact of protein and amino acid fermentation on the composition and metabolic output of gut microbiota. Although dissimilatory pathways have been described for most amino acids, microbial degradation routes within the gut microbiota are relatively unexplored. The objectives were (1) to characterize amino acid breakdown by the colonic microbiota, (2) to determine the fermentation products formed from individual amino acids/protein (3) to examine how amino acid metabolism is impacted by the presence of a fermentable fiber (prebiotic inulin) and finally (4) to evaluate with an in vivo model (trout fish) diet:microbe interactions and the development of gut microbiota during fish farming. Interactions between the healthy human intestinal microbiota of the distal colon and different combinations of nutrients were simulated using in vitro pH-controlled anaerobic batch cultures of human faeces. Combining high-throughput sequencing of 16S rRNA amplicons, with high-throughput 1H NMR, changes in faecal microbiota composition and metabolic output were measured. During exogenous substrate microbial fermentation (e.g. beef, Trp or fish feed) in the large bowel bioactive compounds (harmful or beneficial) are produced. Many factors affect the gut-microbial metabolism including pH, type and quantity of growth substrate (e.g. protein/carbohydrate) and make up of the gut microbiota. Considerable interindividual variation was observed in response to different digested substrates but over all, the beneficial impact of prebiotic fiber fermentation on production of bioactive compounds from amino acids/proteins was confirmed in this study. In trout, although our dietary intervention with essential oils had little impact on the gut microbiota, the study showed for the first time a dramatic shift in the composition and diversity of the gut microbiota in juvenile, compared to adult fish. Thse observations may have relevance in designing dietary strategies to reduce chronic diseases like colon cancer and heard disease and for fish farming respectively

Current evidence linking diet to gut microbiota and brain development and function

The gut:brain axis is emerging as an important information highway linking the foods we eat with neurophysiological development and functions. Some gut microorganisms have shown to alleviate anxiety and depression, improve cognitive performance and play a role in brain development in early life. However, most studies were conducted in laboratory animals and these findings await confirmation in carefully designed human interventions. Similarly, little attention has been given to how diet:microbe interactions within the gut can impact on neurotransmitter production or their subsequent biological effects within the nervous system. In this review, we discuss the possible influence of carbohydrates, polyphenols, lipids and proteins colonic fermentation on production, bioavailability and biological activity of metabolites linked to the gut-microbiota-brain axis. An increased understanding of how nervous system may be regulated by diet will greatly enhance our ability to design dietary strategies to improve healthy brain development and functions

Diet and the Gut Microbiota – How the Gut: Brain Axis Impacts on Autism

Autism spectrum disorders (ASDs) are a group of neurodevelopmental conditions characterized by qualitative impairments in social interaction and communication, and by the presence of restricted interests and of repetitive and stereotyped behaviors. Although environmental factors are recognized to play an important role in ASD, there is little conclusive evidence linking diet with disease onset and progression. However, recent works examining how diet shapes the gut:brain axis may offer new insights into environmental contributions to disease mechanisms and raise the possibility of at least improving certain ASD symptoms through diet. Gut microbiota is a key player in development and regulation of the gut:brain axis and might thus play a critical role in ASD pathophysiology. Indeed, gut microbiota is altered in ASD. The recent appreciation of the core contribution of the human microbiome to host metabolic processes and in processing of dietary compounds has raised interest in how microbial activities might impact on ASD. This chapter provides a detailed overview of the current knowledge on the effect of gut microbiota on the metabolism of molecules (amino acids, γ-aminobutyric acid, unsaturated fatty acids, short-chain fatty acids, cholesterol, butyrate, acetate, N-acetylaspartate, polyphenols, etc.) and enzymes (disaccharidases, hexose transporters, and monocarboxylic acid transporters, among others) associated with ADS onset and progression. The role of dietary patterns, probiotics, and successional development of gut microbiota in brain function is also reviewed. Evidence points to the essential role of gut microbiota composition and metabolism in brain development and disease risk throughout life. However, there is a clear lack of human data describing the contribution of gut microbiota and its modulation through diet to hormonal, immunological, or metabolic communication along the information highways linking gut and brain, especially in early childhood