Regulation of tissue LC-PUFA contents, Δ6 fatty acyl desaturase (FADS2) gene expression and the methylation of the putative FADS2 gene promoter by different dietary fatty acid profiles in Japanese seabass (Lateolabrax japonicus).
The present study was conducted to evaluate the influences of different dietary fatty acid profiles on the tissue content and biosynthesis of LC-PUFA in a euryhaline species Japanese seabass reared in seawater. Six diets were prepared, each with a characteristic fatty acid: Diet PA: Palmitic acid (C16:0); Diet SA: Stearic acid (C18:0); Diet OA: Oleic acid (C18:1n-9); Diet LNA: α-linolenic acid (C18:3n-3); Diet N-3 LC-PUFA: n-3 LC-PUFA (DHA+EPA); Diet FO: the fish oil control. A 10-week feeding trial was conducted using juvenile fish (29.53 ± 0.86 g). The results showed that Japanese seabass had limited capacity to synthesize LC-PUFA and fish fed PA, SA, OA and LNA showed significantly lower tissue n-3 LC-PUFA contents compared to fish fed N-3 LC-PUFA and FO. The putative gene promoter and full-length cDNA of FADS2 was cloned and characterized. The protein sequence was confirmed to be homologous to FADS2s of marine teleosts and possessed all the characteristic features of microsomal fatty acid desaturases. The FADS2 transcript levels in liver of fish fed N-3 LC-PUFA and FO were significantly lower than those in fish fed other diets except LNA while Diet PA significantly up-regulated the FADS2 gene expression compared to Diet LNA, N-3 LC-PUFA and FO. Inversely, fish fed N-3 LC-PUFA and FO showed significantly higher promoter methylation rates of FADS2 gene compared to fish fed the LC-PUFA deficient diets. These results suggested that Japanese seabass had low LC-PUFA synthesis capacity and LC-PUFA deficient diets caused significantly reduced tissue n-3 LC-PUFA contents. The liver gene expression of FADS2 was up-regulated in groups enriched in C16:0, C18:0 and C18:1n-9 respectively but not in the group enriched in C18:3n-3 compared to groups with high n-3 LC-PUFA contents. The FADS2 gene expression regulated by dietary fatty acids was significantly negatively correlated with the methylation rate of putative FADS2 gene promoter.
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China ; Key Laboratory of Chinese Ministry of Agriculture for Sustainable Utilization of Marine Fisheries Resources, Yellow Sea Fisheries Research Institute, Qingdao, China.
Houguo
H
Xu
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.
Xiaojing
X
Dong
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.
Qinghui
Q
Ai
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.
Kangsen
K
Mai
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.
Wei
W
Xu
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.
Yanjiao
Y
Zhang
Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture) & Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China ; Key Laboratory of Mariculture and Stock Enhancement in North China's Sea (Ministry of Agriculture), Dalian Ocean University, Dalian, China.
Rantao
R
Zuo
D000818:Animals; D001492:Bass / Q000378:metabolism*; D019175:DNA Methylation / Q000187:drug effects* / Q000502:physiology; D004041:Dietary Fats / Q000494:pharmacology*; D044943:Fatty Acid Desaturases / Q000096:biosynthesis*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D029941:Fish Proteins / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology
D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D029941:Fish Proteins; D044943:Fatty Acid Desaturases