Gut microbiota-generated metabolites in animal health and disease

Microbiota and probiotics in canine and feline welfare

Dogs and cats have been cohabiting with us for thousands of years. They are the major human companions. Today, dogs and cats live in urban areas. Cats and most dogs are on high carbohydrate diets and face similar life-style challenges as the human beings. The health and well-being of companion animals, just as their owners, depends on the gut microbes. Providing a proper care and nutritionally balanced diet to companion animals is recognised as a part of our responsibility to maintain the health and well being of our pet. However, as microbiota differences may facilitate exposure to pathogens and harmful environmental influences, it is prudent to search for novel tools to protect dogs and cats and at the same time the human owners from pathogens. Specific probiotic strains and/or their defined combinations may be useful in the canine and feline nutrition, therapy, and care. Probiotic supplementations have been successful in the prevention and treatment of acute gastroenteritis, treatment of IBD, and prevention of allergy in companion animals. New challenges for probiotic applications include maintenance of obesity and overweight, urogenital tract infections, Helicobacter gastritis and parasitic infections. The probiotics of human origin appear to be among the new promising tools for the maintenance of pets' health. However, the host-derived microorganisms might be the most appropriate probiotic source. Therefore, more controlled trials are needed to characterise new and safe probiotic preparations with an impact on general health and well being as well as health maintenance in dogs and cats.

Treat the brain and treat the periphery: toward a holistic approach to major depressive disorder

The limited medication for major depressive disorder (MDD) against an ever-rising disease burden presents an urgent need for therapeutic innovations. During recent years, studies looking at the systems regulation of mental health and disease have shown a remarkably powerful control of MDD by systemic signals. Meanwhile, the identification of a host of targets outside the brain opens the way to treat MDD by targeting systemic signals. We examine these emerging findings and consider the implications for current thinking regarding MDD pathogenesis and treatment. We highlight the opportunities and challenges of a periphery-targeting strategy and propose its incorporation into a holistic approach.

[Characterization, influence and manipulation of the gastrointestinal microbiota in health and disease]

The gastrointestinal tract harbors trillions of microorganisms that are indispensable for health. The gastrointestinal microbiota can be studied using culture and molecular methods. The applications of massive sequencing are constantly increasing, due to their high yield, increasingly accessible costs, and the availability of free software for data analysis. The present article provides a detailed review of a large number of studies on the gastrointestinal microbiota and its influence on human health; particular emphasis is placed on the evidence suggesting a relationship between the gastrointestinal microbial ecosystem and diverse physiological and immune/inflammatory processes. Discussion of the articles analyzed combines a medical approach and current concepts of microbial molecular ecology. The present revision aims to be useful to those interested in the gastrointestinal microbiota and its possible alteration to maintain, re-establish and enhance health in the human host.

Bacterial uracil modulates Drosophila DUOX-dependent gut immunity via Hedgehog-induced signaling endosomes

Genetic studies in Drosophila have demonstrated that generation of microbicidal reactive oxygen species (ROS) through the NADPH dual oxidase (DUOX) is a first line of defense in the gut epithelia. Bacterial uracil acts as DUOX-activating ligand through poorly understood mechanisms. Here, we show that the Hedgehog (Hh) signaling pathway modulates uracil-induced DUOX activation. Uracil-induced Hh signaling is required for intestinal expression of the calcium-dependent cell adhesion molecule Cadherin 99C (Cad99C) and subsequent Cad99C-dependent formation of endosomes. These endosomes play essential roles in uracil-induced ROS production by acting as signaling platforms for PLCβ/PKC/Ca2+-dependent DUOX activation. Animals with impaired Hh signaling exhibit abolished Cad99C-dependent endosome formation and reduced DUOX activity, resulting in high mortality during enteric infection. Importantly, endosome formation, DUOX activation, and normal host survival are restored by genetic reintroduction of Cad99C into enterocytes, demonstrating the important role for Hh signaling in host resistance to enteric infection.

Functional genomic and metagenomic approaches to understanding gut microbiota-animal mutualism

Accumulating data sets of gut microbiome by next-generation sequencing allow us to gain a comprehensive view of the functional diversity of the gut-associated metagenome. However, many microbiome functions are unknown and/or have only been predicted, and may not necessarily reflect the in vivo function within a gut niche. Functional genomic and metagenomic approaches have been successfully applied to broaden the understanding of invertebrate and vertebrate gut microbiome involved in diverse functions, including colonization ability, nutritional processing, antibiotic resistance, microbial physiology and metabolism, and the modulation of the host physiology. In this review, we discuss the recent knowledge obtained from the study of functional genomics and metagenomics of the animal intestine and its potential values for understanding gut microbiota-animal mutualism.

Probiotics and pregnancy

Complications of pregnancy are associated with adverse outcomes for mother and baby in the short and long term. The gut microbiome has been identified as a key factor for maintaining health outside of pregnancy and could contribute to pregnancy complications. In addition, the vaginal and the recently revealed placental microbiome are altered in pregnancy and may play a role in pregnancy complications. Probiotic supplementation could help to regulate the unbalanced microflora composition observed in obesity and diabetes. Here, the impact of probiotic supplementation during pregnancy and infancy is reviewed. There are indications for a protective role in preeclampsia, gestational diabetes mellitus, vaginal infections, maternal and infant weight gain and allergic diseases. Large, well-designed randomised controlled clinical trials along with metagenomic analysis are needed to establish the role of probiotics in adverse pregnancy and infancy outcomes.

The chemistry of negotiation: rhythmic, glycan-driven acidification in a symbiotic conversation

Glycans have emerged as critical determinants of immune maturation, microbial nutrition, and host health in diverse symbioses. In this study, we asked how cyclic delivery of a single host-derived glycan contributes to the dynamic stability of the mutualism between the squid Euprymna scolopes and its specific, bioluminescent symbiont, Vibrio fischeri. V. fischeri colonizes the crypts of a host organ that is used for behavioral light production. E. scolopes synthesizes the polymeric glycan chitin in macrophage-like immune cells called hemocytes. We show here that, just before dusk, hemocytes migrate from the vasculature into the symbiotic crypts, where they lyse and release particulate chitin, a behavior that is established only in the mature symbiosis. Diel transcriptional rhythms in both partners further indicate that the chitin is provided and metabolized only at night. A V. fischeri mutant defective in chitin catabolism was able to maintain a normal symbiont population level, but only until the symbiotic organ reached maturity (∼ 4 wk after colonization); this result provided a direct link between chitin utilization and symbiont persistence. Finally, catabolism of chitin by the symbionts was also specifically required for a periodic acidification of the adult crypts each night. This acidification, which increases the level of oxygen available to the symbionts, enhances their capacity to produce bioluminescence at night. We propose that other animal hosts may similarly regulate the activities of epithelium-associated microbial communities through the strategic provision of specific nutrients, whose catabolism modulates conditions like pH or anoxia in their symbionts' habitat.

Host-microbe interactions shaping the gastrointestinal environment

Tremendous advances have been made in mapping the complexity of the human gut microbiota in both health and disease states. These analyses have revealed that, rather than a constellation of individual species, a healthy microbiota comprises an interdependent network of microbes. The microbial and host interactions that shape both this network and the gastrointestinal environment are areas of intense investigation. Here we review emerging concepts of how microbial metabolic processes control commensal composition, invading pathogens, immune activation, and intestinal barrier function. We posit that all of these factors are critical for the maintenance of homeostasis and avoidance of overt inflammatory disease. A greater understanding of the underlying mechanisms will shed light on the pathogenesis of many diseases and guide new therapeutic interventions.