Convergence of gut microbiotas in the adaptive radiations of African cichlid fishes

Ecoevolutionary dynamics of the gut microbiota at the macroscale level, that is, in across-species comparisons, are largely driven by ecological variables and host genotype. The repeated explosive radiations of African cichlid fishes in distinct lakes, following a dietary diversification in a context of reduced genetic diversity, provide a natural setup to explore convergence, divergence and repeatability in patterns of microbiota dynamics as a function of the host diet, phylogeny and environment. Here we characterized by 16S rRNA amplicon sequencing the gut microbiota of 29 cichlid species from two distinct lakes/radiations (Tanganyika and Barombi Mbo) and across a broad dietary and phylogenetic range. Within each lake, a significant deviation between a carnivorous and herbivorous lifestyle was found. Herbivore species were characterized by an increased bacterial taxonomic and functional diversity and converged in key compositional and functional community aspects. Despite a significant lake effect on the microbiota structure, this process has occurred with remarkable parallels in the two lakes. A metabolic signature most likely explains this trend, as indicated by a significant enrichment in herbivores/omnivores of bacterial taxa and functions associated with fiber degradation and detoxification of plant chemical compounds. Overall, compositional and functional aspects of the gut microbiota individually and altogether validate and predict main cichlid dietary habits, suggesting a fundamental role of gut bacteria in cichlid niche expansion and adaptation

Efficacy of a new delivery system based on solid lipid microparticles for the oral administration of the non-conventional antioxidant IAC on a diabetes mouse model

Purpose: We previously showed the positive effects of the new antioxidant molecule bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate (IAC) in reducing basal hyperglycaemia and relieving glucose intolerance in a diabetes model. However, the chemical properties of IAC did not allow an efficient oral administration, thus representing the main failing of that study. Here, we tested the effect of a new oral delivery system based on solid lipid microparticles (SLMs) in a diabetes mouse model. Methods: The diabetes model was induced in C57B1/6J mice using streptozotocin and nicotinamide. Only the animals that overcame the glycaemic threshold of 180 mg/dL were enrolled in the study. Diabetic animals were then randomly assigned to 4 groups (n = 9) and treated once a day for 5 consecutive weeks with IAC (50, 100, and 150 mg/kg b.w.). The control group was composed of (n = 7) healthy mice that received only the vehicle. Glucose level was weekly monitored during the treatment period and up to 3 weeks after the suspension of the treatment. Glucose tolerance and insulin-resistance test were carried out. Results: Our results showed that SLMs maintained the IAC effect in reducing basal hyperglycaemia as well as improving the insulin sensitivity and glucose tolerance. Conclusion: The present study confirms that SLMs are promising drug carriers, which allow the oral administration of IAC ensuring its therapeutic efficacy. The concrete possibility to administer IAC per os represents a significant breakthrough in the putative consideration of this multi-radical scavenger in the diabetes therapeutic approach

Membrane Vesicles from the Gut Microbiota and Their Interactions with the Host

Gut microbiota plays an essential role in maintaining intestinal homeostasis and human health. Microbiota establishes a complex network of dynamic and reciprocal interactions with the intestinal epithelium and immune system. The mucin layer that covers the epithelium prevents luminal bacteria from accessing host cells. Thus, microbiota–host communication mainly relies on secreted factors and membrane vesicles (MVs), which can cross the inner mucus layer and reach the epithelium. This chapter focuses on the role of microbiota-secreted MVs as key players in signaling processes in the intestinal mucosa. This is an emerging research topic, with the first reports dating from 2012. Microbiota-derived MVs are involved in interspecies communication in the gut, between bacteria and between microbiota and host. Here we present current knowledge on the mechanisms used by microbiota MVs to assist and control the gut microbial community and to modulate host immune and defense responses. Constant stimulation of immune receptors by microbiota MVs results in tightly controlled inflammation that contributes to tolerogenic responses essential to maintaining intestinal homeostasis. Moreover, gut microbiota MVs are emerging as physical vehicles for distribution and delivery of bacterial effectors to distal tissues in human health and disease