Comparative Fecal Metabolomes of Silkworms Being Fed Mulberry Leaf and Artificial Diet

SIMPLE SUMMARY: Silkworm (Bombyx mori) is an oligophagous insect and their diets have preference for mulberry leaves. However, mulberry leaves are seasonal resources, not available in the winter, which severely limits the silkworm rearing and cocoon production. The aim of this study was to investigate the mechanism that caused the stunted growth and the low efficiency of silk protein synthesis of silkworms fed with artificial diet by analyzing the fecal metabolome. Compared to silkworm reared with mulberry leaves, the contents of the amino acids, carbohydrates and lipids in the feces of silkworm fed with artificial diet obviously decrease, while some organic acids, such as urea and citric acid significantly increase. These findings provide new insights for the improvement of silkworm artificial feed through metabolomics research. ABSTRACT: Metabonomics accurately monitors the precise metabolic responses to various dietary patterns. Metabolic profiling allows simultaneous measurement of various fecal metabolites whose concentrations may be affected by food intake. In this study, we analyzed the fecal metabolomes of silkworm (Bombyx mori) larvae reared on fresh mulberry leaves and artificial diets. 57 differentially expressed metabolites were identified by gas chromatography–mass spectrometry. Of these, 39 were up-regulated and 18 were downregulated in the mulberry leaf meal group. Most of the amino acids, carbohydrates and lipids associated with physical development and silk protein biosynthesis were enriched in silkworms reared on mulberry leaves. In contrast, the urea, citric acid, D-pinitol, D-(+)-cellobiose and N-acetyl glucosamine levels were relatively higher in the silkworm feeding on the artificial diets. The findings of this study help clarify the association between diet and metabolic profiling.