Abstract
Understanding how intestinal microbiota alters energy homeostasis and lipid metabolism is a critical process in energy balance and health. However, the exact role of intestinal microbiota in the regulation of lipid metabolism in fish remains unclear. Here, we used two zebrafish models (germ-free and antibiotics-treated zebrafish) to identify the role of intestinal microbiota in lipid metabolism. Conventional and germ-free zebrafish larvae were fed with egg yolk. Transmission electron microscopy was used to detect the presence of lipid droplets in the intestinal epithelium. The results showed that, microbiota increased lipid accumulation in the intestinal epithelium. The mRNA sequencing technology was used to assess genes expression level. We found majority of the differentially expressed genes were related to lipid metabolism. Due to the limitation of germ-free zebrafish larvae, antibiotics-treated zebrafish were also used to identify the relationship between the gut microbiota and the host lipid metabolism. Oil-red staining showed antibiotics-treated zebrafish had less intestinal lipid accumulation than control group. The mRNA expression of genes related to lipid metabolism in liver and intestine was also quantified by using real-time PCR. The results indicated that apoa4, hsl, cox15, slc2a1a, and lss were more related to intestinal bacteria in fish, while the influence of intestinal microbiota on the activity of fabp6, acsl5, cd36, and gpat2 was different between the liver and intestine. This study identified several genes regulated by intestinal microbiota. Furthermore, the advantages and disadvantages of each model have been discussed. This study provides valuable information for exploring host-microbiota interactions in zebrafish in future.
Highlights
The intestine as the most important absorptive organ is densely colonized with microbial cells referred to as microbial community (Costello et al, 2009)
LB plate was used to detect the bacterial quantity of germ-free and conventional zebrafish
The results indicated that no any bacteria were detected in the germ-free zebrafish and the bacterial quantity was about 106 CFU/g for conventional zebrafish
Summary
The intestine as the most important absorptive organ is densely colonized with microbial cells referred to as microbial community (Costello et al, 2009). The microbial community is considered to be a metabolic “organ” in the host (Backhed et al, 2004) that ferments indigestible dietary polysaccharides (Zhang et al, 2014), increases lipid accumulation in adipocytes (Turnbaugh et al, 2006), and influences nutrient absorption and energy balance (Semova et al, 2012). The colonization of adult germ-free mice with bacteria harvested from the cecum of conventional animals resulted in a significant increase in body fat content (Backhed et al, 2004). All these findings indicated that intestinal microbiota participated in the host lipid metabolism
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