Dietary Supplementation with Omega-6 LC-PUFA-Rich Microalgae Regulates Mucosal Immune Response and Promotes Microbial Diversity in the Zebrafish Gut.

Sagar Nayak,Ashraf Al Ashhab,Dina Zilberg,Inna Khozin-Goldberg

doi:10.3390/biology9060119

Sagar Nayak, Ashraf Al Ashhab + Show 2 more

Open Access

https://doi.org/10.3390/biology9060119

Copy DOI

Abstract

The effect of dietary omega-6 long-chain polyunsaturated fatty acid (LC-PUFA) on host microbiome and gut associated immune function in fish is unexplored. The effect of dietary supplementation with the omega-6 LC-PUFA-rich microalga Lobosphaera incisa wild type (WT) and its delta-5 desaturase mutant (MUT), rich in arachidonic-acid and dihomo-gamma-linolenic acid (DGLA), respectively, on intestinal gene expression and microbial diversity was analyzed in zebrafish. For 1 month, fish were fed diets supplemented with broken biomass at 7.5% and 15% (w/w) of the two L. incisa strains and a control nonsupplemented commercial diet. Dietary supplementation resulted in elevated expression of genes related to arachidonic acid metabolism-cyclooxygenase 2 (cox-2), lipoxygenase 1(lox-1), anti-inflammatory cytokine-interleukin 10 (il-10), immune defense-lysozyme (lys), intestinal alkaline phosphatase (iap), complement (c3b), and antioxidants-catalase (cat), glutathione peroxidase (gpx). Microbiome analysis of the gut showed higher diversity indices for microbial communities in fish that were fed the supplemented diets compared to controls. Different treatment groups shared 237 operational taxonomic units (OTUs) that corresponded to the core microbiome, and unique OTUs were evident in different dietary groups. Overall, the zebrafish gut microbiome was dominated by the phylum Fusobacteria and Proteobacteria (averaging 38.4% and 34.6%, respectively), followed by Bacteroidetes (12.9%), Tenericutes, Planctomycetes, and Actinobacteria (at 3.1–1.3%). Significant interaction between some of the immune-related genes and microbial community was demonstrated.

Highlights

Diet, gut microbiome, and gut-associated immune function are recognized as key contributors to metabolic processes, pathological conditions, and immune responses affecting the overall health of an organism [1,2,3]
In our previous study with zebrafish, we demonstrated that ARA- and dihomo-gamma-linolenic acid (DGLA)-rich diets exert a significant effect on the expression of various immune and inflammatory genes in kidneys, and contribute to better performance of the fish upon bacterial challenge [25]
To check the effect of dietary supplementation on fish gut microbial diversity, we calculated the observed number of operational taxonomic units (OTUs), the Shannon diversity index, and Faith’s phylogenetic diversity for the gut samples

Summary

Introduction

Gut microbiome, and gut-associated immune function are recognized as key contributors to metabolic processes, pathological conditions, and immune responses affecting the overall health of an organism [1,2,3]. Microbes and microbial products influence both systemic and mucosal immune responses through the interaction of microbe-associated molecular patterns with pattern-recognition receptors in the host. The microbial community in the fish gut contributes to the development, maturation, and modulation of its immune system [4]. Fish microbiota are known to play key roles in cytokine modulation, B and T leukocyte activation, and immunoglobulin levels [5]. Diseases can emerge when the gut microbiome is altered by various factors, such as environmental changes, use of antibiotics, and different diets that affect the symbioses and interactions between the gut microbiome and its host.

Objectives

Methods

Results

Conclusion