Abstract
Bile acids (BAs) usually display growth-promoting and lipid-lowering properties when supplemented to the diet. The effects of a high-lipid diet (HD) and BAs supplementation on growth performance and lipid deposition of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) was evaluated in this study. Compared to the control diet (CD), the HD did not significantly affect the fish growth performance, but it promoted lipid deposition, as revealed by a significantly higher crude lipid content of the whole body, muscle, and liver. Among the HD supplemented with taurocholic acid (BD) groups, and compared to the HD, fish fed dietary supplementation of BAs at 900 mg kg−1 exhibited the best growth performance and lowest hepatic lipid deposition. In most BD groups, the content of total cholesterol, low-density lipoprotein cholesterol, and triglycerides in serum, as well as the content of total cholesterol in the liver, were decreased, whereas the content of high-density lipoprotein cholesterol in serum was increased. In addition, the most strongly influenced pathways between the control, HD, and B3D groups were fatty acid biosynthesis, insulin signaling pathway, and AMPK signaling pathway. The improvement of lipid metabolism induced by the supplementation of BAs may be attributed to decreased expression of lipogenesis genes and proteins (enzymes), and increased lipolysis. In conclusion, dietary supplementation of BAs at 900 mg kg−1 promoted growth performance and reduced lipid accumulation, whereas BAs supplementation improved the hepatic lipid metabolism by enhancing hepatic lipolysis, inhibiting lipogenesis, and regulating associated transcriptional factors in hybrid grouper.
Highlights
The hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) is a popular marine fish in Asia that has great potential in the aquaculture industry due to its rapid growth and popularity with consumers [1]
When the exogenous dietary Bile acids (BAs) level was at 900 mg kg−1, fish exhibited the best growth performance, with a higher growth rate compared to other levels
In agreement with the downregulated/upregulated mRNA expression levels of ppara in large yellow croaker fed high-fat/BAs treatment diets, respectively [11], our study showed that hybrid grouper fed an High-lipid diets (HD) exhibited reduced expression of lipolysis genes and activities of lipolysis enzymes (LPS and triglyceride lipase (ATGL)), while these pathways were enhanced in most BAs diets (BD) groups
Summary
The hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) is a popular marine fish in Asia that has great potential in the aquaculture industry due to its rapid growth and popularity with consumers [1]. High-lipid diets (HD) for hybrid grouper are favored by the aquaculture. Bile Acids in Hybrid Grouper industry because they reduce the use of costly protein as an energy source [3]. Bile acids (BAs) are synthesized from cholesterol, produced in the hepatocytes, stored in the gallbladder, and secreted into the intestine to facilitate the digestion of lipids and the absorption of triglycerides (TG), cholesterol, and lipid-soluble vitamins [7, 8]. Previous studies showed that the addition of BAs improved the growth performance, including the weight gain (WG) and special growth rate (SGR), of largemouth bass (Micropterus salmoides) fed an HD [9] or a high-starch diet [10], of yellow croaker (Larimichthys crocea) fed an HD [11], of grass carp (Ctenopharyngodon idella) fed an HD [12], of tilapia (Oreochromis niloticus) fed a plant protein-based diet [13], of turbot (Scophthalmus maximus) fed a high plant protein diet [14], previous studies have not focused on the effects of dietary BAs on growth performance of hybrid grouper
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