Effects of TiO2 nanoparticles on nutrition metabolism in silkworm fat body.

J. H. Tian,W. D. Shen,Y. Y. Li,M. Ni,F. C. Li,B. Li,J. S. Hu,B. B. Wang,K. Z. Xu

doi:10.1242/bio.015610

Abstract

ABSTRACTSilkworm (Bombyx mori) is an important economic insect with a fat body that plays a crucial role in the storage and transfer of nutrients. It is also known that TiO2 nanoparticles (NPs) can improve feed efficiency and promote silk protein synthesis in the silkworm. In this study, we profiled gene expression in the silkworm fat body after TiO2 NP treatment, validated the major RNA-seq findings, and determined the contents of trehalose and triglyceride, the activity of lipase, and the amount of total proteins. RNA-seq analysis revealed that TiO2 NP treatment caused significant expression changes in 341 genes (P≤0.01), 138 of which were upregulated while the other 203 were downregulated. The expression levels of two target genes in the insulin signaling pathway and two protein metabolism-related target genes, three lipid metabolism-associated target genes, two carbohydrate metabolism related target genes and expression levels of seven heat shock protein genes were increased, and that of threonine dehydratase gene and fatty acid transport protein gene were decreased. The RNA-seq results of 16 genes were validated by quantitative real-time PCR. The lipase activity, content of trehalose, and amount of total proteins were elevated by 3.86-fold, 1.34-fold, and 1.21-fold, respectively, and the content of triglyceride was decreased by 0.94-fold after TiO2 NP treatment. These results indicated that TiO2 NPs activated the insulin signaling pathway, promoted the metabolism of protein, fat, and carbohydrate, and improved nutrition metabolism. Our study provides new support for the understanding of the beneficial effect of TiO2 NPs on silkworm nutrient metabolism.

Highlights

The silkworm, which belongs to Lepidoptera: Bombycidae, has complete metamorphosis including four stages: egg, larva, pupa and adult
Effect of TiO2 NPs on the gene expression in silkworm fat body Fifth instar silkworms were fed with TiO2 NPs, and RNA-seq was used to determine TiO2 NPs’ effect on gene expression in the silkworm fat body
RNA-seq revealed that TiO2 NPs treatment led to differential expression of 11,268 genes in the silkworm fat body. 341 genes showed significant differences, among which 138 were upregulated and 203 were downregulated (Fig. 1)

Summary

Introduction

The silkworm, which belongs to Lepidoptera: Bombycidae, has complete metamorphosis including four stages: egg, larva, pupa and adult. The larvae use absorbed nutrients to provide energy for the growth, development and metamorphosis, during which they synthesize and secrete a large amount of silk proteins (Tanaka et al, 2009; Truman and Riddiford, 1999). The fat body is the silkworm’s intermediate metabolic organ, playing important physiological roles in nutrient storage and transport (Arrese and Soulages, 2010), metabolic detoxification TiO2 NPs can mediate the synthesis of ecdysterone to affect silkworm growth and development (Li et al, 2014), and enhance silkworm’s anti-viral ability (Su et al, 2014)

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Results

Conclusion