Dietary supplementation of ethyl caffeate in hybrid grouper (Epinephelus fuscoguttatus ?� x Epinephelus lanceolatus ??: study on growth-related gene expression and gut microbiota

Abstract

The hybrid grouper (Epinephelus fuscoguttatus female x Epinephelus lanceolatus male) is among the most profitable aquaculture species worldwide. However, its growth is often hindered by pathogenic infections and poor environmental conditions. Healthy gut microbiota is essential for appropriate gastrointestinal function, which regulates host growth and health. Ethyl caffeate (EC) enhances growth performance in hybrid groupers. However, the mechanism underlying EC-induced improvements in growth performance-for example, changes in growth-related gene expression and gut microbiota composition-remains unclear. In this study, we investigated how dietary supplementation of EC influences growth-related gene expression and gut microbiota composition in hybrid groupers. The expression of growth hormone, growth hormone receptor 1, and insulin-like growth factor 1 genes in several organs of hybrid groupers was evaluated. Dietary supplementation of EC (0.25 g/kg) markedly upregulated the aforementioned genes. Furthermore, the 16S ribosomal RNA V3-V4 region and the DNA internal transcribed spacer region were sequenced. Microbiota analysis revealed that hybrid groupers fed basal feed without EC primarily contained 72.82% Proteobacteria and 17.96% Firmicutes, which constituted approximately 90% of the total gut microbiota. Conversely, hybrid groupers fed basal diet + 0.25 g/kg EC contained 67.23% Firmicutes and 25.09% Proteobacteria. The 0.25 g/kg EC diet upregulated the cell cycle and various physiological pathways (lipid, linoleic acid, starch, sucrose, amino acid, and energy metabolism; protein digestion; and mechanistic target of rapamycin signaling). Our findings suggest that dietary supplementation of 0.25 g/kg EC enhances the growth of hybrid groupers by modulating gut microbiota composition and associated metabolic pathways.