A 10-week feeding trial was conducted to investigate the effect of dietary curcumin (CC) on growth antioxidant responses, fatty acid composition, and expression of lipid metabolism-related genes of large yellow croaker fed a high-fat diet (HFD). Four diets (lipid level at 18 %) were formulated with different levels of curcumin (0, 0·02, 0·04 and 0·06 %). The best growth performance was found in the 0·04 % curcumin group, with the body and hepatic lipid levels lower than the control group (0 % CC). The content of TAG, total cholesterol and LDL-cholesterol was the least in the 0·06 % curcumin group. The lowest malondialdehyde and the highest superoxide dismutase, catalase and total antioxidant capacity were observed in the 0·04 % curcumin group. The 0·04 % curcumin group had higher expression of Δ6fad, elovl5 and elovl4 and showed higher hepatic n-6 and n-3 PUFA. Expression of ppara, cpt1, and aco was significantly increased, while expression of srebp1 and fas was dramatically decreased in curcumin groups compared with the control group. Overall, 0·04 % curcumin supplementation could mitigate the negative effects caused by HFD and promote growth via reducing hepatic lipid deposition, improving antioxidant activity and increasing PUFA of large yellow croaker. To conclude, abnormal hepatic lipid deposition was probably due to increased fatty acid oxidation and reduced de novo synthesis of fatty acids.

An 8-week feeding trial was conducted to evaluate the effects of dietary n-3 LC-PUFA levels on growth performance, tissue fatty acid profiles and relative expression of genes involved in the lipid metabolism of mud crab (Scylla paramamosain). Ten isonitrogenous diets were formulated to contain five n-3 LC-PUFA levels at 7 and 12 % dietary lipid levels. The highest weight gain and specific growth rate were observed in crabs fed the diets with 19·8 and 13·2 mg/g n-3 LC-PUFA at 7 and 12 % lipid, respectively. Moisture and lipid contents in hepatopancreas and muscle were significantly influenced by dietary n-3 LC-PUFA at the two lipid levels. The DHA, EPA, n-3 LC-PUFA contents and n-3:n-6 PUFA ratio in hepatopancreas and muscle significantly increased as dietary n-3 LC-PUFA levels increased at both lipid levels. The expression levels of -6 fatty acyl desaturase and acyl-CoA oxidase in hepatopancreas increased significantly, and expression levels of fatty acid synthase, carnitine palmitoyltransferase I and hormone-sensitive TAG lipase were down-regulated, with increased dietary n-3 LC-PUFA regardless of lipid level. Based on weight gain, n-3 LC-PUFA requirements of S. paramamosain were estimated to be 20·1 and 12·7 mg/g of diet at 7 and 12 % dietary lipid, respectively. Overall, dietary lipid level influenced lipid metabolism, and purified, high-lipid diets rich in palmitic acid reduced the n-3 LC-PUFA requirement of juvenile mud crab.

The present study was conducted to determine the effects of dietary terrestrial oils (TO) supplemented with l-carnitine on growth performance, biochemical and antioxidant response, lipid metabolism and inflammation in large yellow croaker (Larimichthys crocea). Three iso-nitrogenous and iso-lipidic experimental diets were formulated with FO (fish oil, the control group), 75 % TO (75 % FO was substituted by the oil mixture with equal amounts of soyabean oil, linseed oil and pork lard) and 75 % TOC (75 % TO supplemented with 800 mg/kg l-carnitine). Compared with the control group, feed efficiency ratio and specific growth rate were significantly increased in fish fed diets with 75 % TO and 75 % TOC. Hepatic lipid content, serum TAG level, LDL-cholesterol level and the mRNA expression of pro-inflammatory genes (tnfα and ifnγ) were significantly increased in fish fed the diet with 75 % TO compared with the control group. However, the supplementation of 800 mg/kg l-carnitine in the 75 % TO diet repressed hepatic lipid content, serum LDL-cholesterol level and the mRNA expression of tnfα and ifnγ in fish compared with fish fed the diet with 75 % TO. Total antioxidant capacity, the activity of superoxide dismutase, the mRNA expression of cpt-I and the activity of CPT-I were significantly increased in fish fed the diet with 75 % TOC compared with 75 % TO. In conclusion, these results suggested that the supplementation of 800 mg/kg l-carnitine in the diet with TO mixture could increase growth, antioxidant capacity and fatty acid oxidation and decrease the expression of inflammatory genes in large yellow croaker.

The regulation of lipogenesis and lipolysis mechanisms related to consumption of lipid has not been studied in swimming crab. The aims of the present study were to evaluate the effects of dietary lipid levels on growth, enzymes activities and expression of genes of lipid metabolism in hepatopancreas of juvenile swimming crab. Three isonitrogenous diets were formulated to contain crude lipid levels at 5·8, 9·9 and 15·1 %. Crabs fed the diet containing 15·1 % lipid had significantly lower growth performance and feed utilisation than those fed the 5·8 and 9·9 % lipid diets. Crabs fed 5·8 % lipid had lower malondialdehyde concentrations in the haemolymph and hepatopancreas than those fed the other diets. Highest glutathione peroxidase in haemolymph and superoxide dismutase in hepatopancreas were observed in crabs fed 5·8 % lipid. The lowest fatty acid synthase and glucose 6-phosphate dehydrogenase activities in hepatopancreas were observed in crabs fed 15·1 % lipid, whereas crabs fed 5·8 % lipid had lower carnitine palmitoyltransferase-1 activity than those fed the other diets. Crabs fed 15·1 % lipid showed lower hepatopancreas expression of genes involved in long-chain-PUFA biosynthesis, lipoprotein clearance, fatty acid uptake, fatty acid oxidation, lipid anabolism and lipid catabolism than those fed the other diets, whereas expression of some genes of lipoprotein assembly and fatty acid oxidation was up-regulated compared with crabs fed 5·8 % lipid. Overall, high dietary lipid level can inhibit growth, reduce antioxidant enzyme activities and influence lipid metabolic pathways to regulate lipid deposition in crab.

Polyunsaturated fatty acids (FA) regulate genes involved in lipid metabolism. The effects of polyunsaturated FA on the transcription factor adipocyte determination and differentiation-dependent factor (ADD) 1 and fatty acid synthase (FAS) mRNA in differentiating porcine adipocytes were measured using a stromal vascular cell culture system. Porcine stromal vascular cells were isolated from subcutaneous adi-pose tissues and plated in Dulbecco's modified Eagle's medium (DMEM)–nutrient mixture F-12 Ham (F-12) plus fetal bovine serum (100 ml/l) for 24 h. Then cells were differentiated in DMEM–F12 plus insulin, hydrocortisone and transferrin without or with polyunsaturated FA at 6·25, 25·00 or 100·00 μm. The ADD1 mRNA was decreased by 100·00 μm-arachidonic acid, 6·25 to 100·00 μm-docosahexaenoic acid or cis-9,trans-11-conjugated linoleic acid. The polyunsaturated FA reduced the transcription rate of FAS, but not of ADD1. All three polyunsaturated FA accelerated degradation of ADD1 and FAS mRNA to reduce the abundance of ADD1 and FAS mRNA. Results also showed that polyunsaturated FA inhibit the ADD1 expression, not only of mRNA concentration, but also of mature ADD1 protein concentration, suggesting an overall reduction of ADD1 function by polyunsaturated FA. Our present experiments demonstrate that polyunsaturated FA regulate the gene expression of ADD1 and enzymes involved in lipid metabolism in porcine adipocytes.