title: Dietary lipid levels impact lipoprotein lipase, hormone-sensitive lipase, and fatty acid synthetase gene expression in three tissues of adult GIFT strain of Nile tilapia, Oreochromis niloticus.
abstract: The objective of this study was to assess the effects of dietary lipids on growth performance, body composition, serum parameters, and expression of genes involved in lipid metabolism in adult genetically improved farmed tilapia (GIFT strain) of Nile tilapia, Oreochromis niloticus. We randomly assigned adult male Nile tilapia (average initial body weight = 220.00 ± 9.54 g) into six groups consisting of four replicates (20 fish per replicate). Fish in each group were hand-fed a semi-purified diets containing different lipid levels [3.3 (the control group), 28.4, 51.4, 75.4, 101.9, and 124.1 g kg(-1)] for 8 weeks. The results indicated that there was no obvious effect in feeding rate among all groups (P > 0.05). The highest weight gain, specific growth rate, and protein efficiency ratio in 75.4 g kg(-1) diet group were increased by 23.31, 16.17, and 22.02 % than that of fish in the control group (P < 0.05). Protein retention ratio was highest in 51.4 g kg(-1) diet group. The results revealed that the optimum dietary lipid level for maximum growth performance is 76.6-87.9 g kg(-1). Increasing dietary lipid levels contributed to increased tissue and whole body lipid levels. Saturated and monounsaturated fatty acids (MUFAs) decreased, and polyunsaturated fatty acids increased with increasing dietary lipid levels. With the exception of MUFAs, the fatty acid profiles of liver and muscle were similar. Dietary lipid levels were negatively correlated with low-density lipoprotein- cholesterol content and positively with triacylglycerol and glucose contents. In the lipid-fed groups, there was a significant down-regulation of fatty acid synthase (FAS) mRNA in liver, muscle, and visceral adipose tissues. There was a rapid up-regulation of lipoprotein lipase (LPL) mRNA in muscle and liver with increasing dietary lipid levels. In visceral adipose tissue, LPL mRNA was significantly down-regulated in the lipid-fed groups. Dietary lipids increased hormone-sensitive lipase (HSL) mRNA expression levels in the three tissues. These results strongly suggested that moderate dietary lipid levels were beneficial for adult tilapia growth performance and feed efficiency. However, excessive dietary lipid levels contributed to lipid deposition. Additionally, excessive dietary lipids may induce a competition between lipolysis and lipogenesis. FAS did not have tissue-specific regulation; however, the regulation of dietary lipids on LPL expression is tissue specific. FAS was a negative feedback regulator on fat deposition, and HSL was an indicator of fat content in tilapia.
authors.affiliation: Key Laboratory of Freshwater Biodiversity Conservation and Utilization, Ministry of Agriculture, Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, No. 8, Wudayuan 1st Road, Donghu Hi-Tech Development Zone, Wuhan, 430223, Hubei, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Tian
authors.forename: Fan
authors.initials: F
authors.lastname: Wu
authors.forename: Chang-Geng
authors.initials: CG
authors.lastname: Yang
authors.forename: Ming
authors.initials: M
authors.lastname: Jiang
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Hua
authors.initials: H
authors.lastname: Wen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001823:Body Composition / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002849:Chromatography, Gas / Q000662:veterinary; D023681:Cichlids / Q000097:blood / Q000254:growth & development* / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004041:Dietary Fats / Q000494:pharmacology*; D064429:Fatty Acid Synthases / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis; D005247:Feeding Behavior / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008297:Male; D016133:Polymerase Chain Reaction / Q000662:veterinary; D002787:Sterol Esterase / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D004041:Dietary Fats; D005227:Fatty Acids; D064429:Fatty Acid Synthases; D002787:Sterol Esterase; D008071:Lipoprotein Lipase