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The tissue distribution pattern of lipid is highly diverse among different fish species. Tiger puffer has a special lipid storage pattern, storing lipid predominantly in liver. In order to better understand the lipid physiology in fish storing lipid in liver, the present study preliminarily investigated the tissue distribution of transcription for 29 lipid metabolism-related genes in tiger puffer, which are involved in lipogenesis, fatty acid oxidation, biosynthesis and hydrolysis of glycerides, lipid transport, and relevant transcription regulation. Samples of eight tissues, brain, eye, heart, spleen, liver, intestine, skin, and muscle, from fifteen juvenile tiger puffer were used in the qRT-PCR analysis. The intestine and brain had high transcription of lipogenic genes, whereas the liver and muscle had low expression levels. The intestine also had the highest transcription level of most apolipoproteins and lipid metabolism-related transcription factors. The transcription of fatty acid β-oxidation-related genes was low in the muscle. The peroxisomal fatty acid oxidation may dominate over mitochondrial β-oxidation in the liver and intestine of tiger puffer, and the MAG pathway probably predominates over the G3P pathway in re-acylation of absorbed lipids in the intestine. The intracellular glyceridases were highly transcribed in the brain, eye, and heart. In conclusion, in tiger puffer, the intestine could be a center of lipid metabolism whereas the liver is more likely a pure storage organ for lipid. The lipid metabolism in the muscle could also be inactive, possibly due to the very low level of intramuscular lipid.

Methionine (Met) is one of the most important amino acids in fish feed. The effects of dietary Met on lipid deposition in fish varied a lot among different studies. The present study was aimed at investigating the effects of dietary Met supplementation on the lipid accumulation in tiger puffer, which have a unique lipid storage pattern. Crystalline L-Met was supplemented to a low-fishmeal control diet to obtain two experimental diets with a low (1.1% of dry weight, L-MET) or high Met level (1.6% of dry weight, H-MET). A 67-day feeding trial was conducted with juvenile tiger puffer (average initial weight, 13.83 g). Each diet was fed to triplicate tanks (30 fish in each tank). The results showed that the total lipid contents in whole-body and liver significantly increased with increasing dietary Met levels. The hepatosomatic index, weight gain, and total bile acid content in serum showed similar patterns in response to dietary Met treatments, while the lipid content in muscle was not affected. The hepatic contents of 18-carbon fatty acids were elevated by dietary Met supplementation. The Hepatic mRNA expression of lipogenetic gene such as FAS, GPAT, PPARγ, ACLY, and SCD1 was down-regulated, while the gene expression of lipolytic genes ACOX1 and HSL, as well as that of ApoB100, were up-regulated by increasing dietary Met levels. The hepatic lipidomics of experimental fish was also analyzed. In conclusion, increasing dietary Met levels (0.61%, 1.10%, and 1.60%) increased the hepatic lipid accumulation in tiger puffer. The mechanisms involved warrant further studies., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Astaxanthin (AST), functioning as an efficient antioxidant and pigment, is one of the most expensive additives in shrimp feeds. How to improve the uptake efficiency of dietary astaxanthin into farmed shrimp is of significance. The present study investigated the effects of lysophosphatidylcholine (LPC), an emulsifier, on dietary astaxanthin efficiency, growth performance, body color, body composition, as well as lipid metabolism of juvenile Pacific white shrimp (average initial body weight: 2.4 g). Three diets were prepared: control group, the AST group (supplemented with 0.02% AST), and the AST + LPC group (supplemented with 0.02% AST and 0.1% LPC). Each diet was fed to triplicate tanks, and each tank was stocked with 30 shrimp. The shrimp were fed four times daily for eight weeks. The AST supplementation improved the growth of white shrimp, while LPC further promoted the final weight of shrimp, but the whole-shrimp proximate composition and fatty acid composition were only slightly affected by AST and LPC. The LPC supplementation significantly increased the astaxanthin deposition in the muscle. The LPC supplementation significantly increased the shell yellowness of both raw and cooked shrimp compared to the AST group. Moreover, the dietary LPC increased the high-density lipoprotein-cholesterol content but decreased the low-density lipoprotein-cholesterol content in the serum, indicating the possible regulation of lipid and cholesterol transport. The addition of astaxanthin significantly up-regulated the expression of npc2 in the hepatopancreas compared to the control group, while the addition of LPC down-regulated the expression of mttp compared to the AST group. In conclusion, the LPC supplementation could facilitate the deposition of dietary astaxanthin into farmed shrimp and further enlarge the beneficial effects of dietary astaxanthin. LPC may also independently regulate shrimp body color and cholesterol transportation. This was the first investigation of the promoting effects of LPC on dietary astaxanthin efficiency. [ABSTRACT FROM AUTHOR]

Simple Summary: Enteromorpha prolifera is a type of green marine macroalgae that can cause green tides due to eutrophication. However, aquafeeds demand for E. prolifera meal has gradually exceeded annual E. prolifera production. Therefore, novel extraction methods should be applied to increase the bioactive compounds of E. prolifera at the level of large-scale industrialization to support the efficient utilization of E. prolifera in aquafeeds. According to biological activities of E. prolifera, the growth, feed intake, lipid metabolism, antioxidant, immune parameters and stress resistance were investigated in Pacific white shrimp. It confirmed that bio-products of E. prolifera based on different processing procedures could be used to reduce the amount of E. prolifera in feed without compromising its biological function. It will helpful to improve the application of E. prolifera in aquaculture. A feeding trial was conducted to evaluate the biological activities of Enteromorpha prolifera bio-products in the diets of Pacific white shrimp (Litopenaeus vannamei). Bio-products of E. prolifera included E. prolifera meal, E. prolifera hydrolysate and E. prolifera polysaccharide, which was supplied using different processing procedures. The control diet was supplemented without any E. prolifera bio-products or dietary attractants. Experimental diets were formulated to contain 0.2% and 0.4% of E. prolifera hydrolysate (EPH0.2% and EPH0.4%), 0.03% of E. prolifera polysaccharide (EPP0.03%), 3% of E. prolifera meal (EPM3%), 0.1% of dimethyl-β-propiothetn (DMPT0.1%) and 1% of squid paste (SP1%). Shrimp (~8 g) were randomly distributed in 21 tanks and fed for 44 days. Feed intake showed that 3% of E. prolifera meal and 0.4% of E. prolifera hydrolysate in diets exhibited similar attractant effects as 0.1% of DMPT. Gross qualitative observation showed that the abundance of lipid droplets decreased in hepatopancreas of the EPH0.4% and EPM3% groups, which were supported by hepatopancreas triacylglycerol (TG), where significantly lower concentrations were observed in the EPH0.4% and EPM3% groups compared with the control group. Similarly, TG and low-density lipoprotein cholesterol in serum significantly decreased in the EPH0.4%, EPP0.03% and EPM3% groups compared to the control group. Supplemental E. prolifera bio-products resulted in significantly higher serum glutathione level of EPP0.03% or superoxide dismutase activities of EPH0.4% and EPM3%, but significantly lower serum malondialdehyde level of EPM3%. In addition, tnf-α expression in hepatopancreas was significantly down-regulated in shrimp fed the EPH0.2%, EPH0.4% and EPM3% diets. Based on survival analysis, E. prolifera bio-products improved the resistance of shrimp to hypoxic stresses. Thus, this study confirmed that bio-products of E. prolifera supplied using different processing procedures could be used to reduce the amount of E. prolifera in feed of shrimp without compromising their biological functions. [ABSTRACT FROM AUTHOR]

Booming fish farming results in relative shortage of fish oil (FO), making it urgent to explore alternative lipid sources. This study comprehensively investigated the efficacy of FO replacement with poultry oil (PO) in diets of tiger puffer (average initial body weight, 12.28 g). An 8-week feeding trial was conducted with experimental diets, in which graded levels (0, 25, 50, 75, and 100%, named FO-C, 25PO, 50PO, 75PO, and 100PO, respectively) of FO were replaced with PO. The feeding trial was conducted in a flow-through seawater system. Each diet was fed to triplicate tanks. The results showed that FO replacement with PO did not significantly affect the growth performance of tiger puffer. FO replacement with PO at 50-100% even slightly increased the growth. PO feeding also had marginal effects on fish body composition, except that it increased the liver moisture content. Dietary PO tended to decrease the serum cholesterol and malondialdehyde content but increase the bile acid content. Increasing levels of dietary PO linearly upregulated the hepatic mRNA expression of the cholesterol biosynthesis enzyme, 3-hydroxy-3-methylglutaryl-CoA reductase, whereas high levels of dietary PO significantly upregulated the expression of the critical regulatory enzyme of bile acid biosynthesis, cholesterol 7-alpha-hydroxylase. In conclusion, poultry oil is a good substitution for fish oil in the diets of tiger puffer. Poultry oil could replace 100% added fish oil in the diet of tiger puffer, without adverse effects on growth and body composition. [ABSTRACT FROM AUTHOR]

Two 70-day feeding trials were conducted to reevaluate the necessity of cholesterol supplementation in diets of two important marine fish species, turbot and tiger puffer. Graded levels (0, 0.5, 1.0, 2.0, and 4.0% of dry matter) of cholesterol were added into the basal diet (with 30% fishmeal but no fish oil) to make five experimental diets, which were designated as control, CHO-0.5, CHO-1.0, CHO-2.0, and CHO-4.0, respectively. The dietary cholesterol concentration was measured to be 0.11%, 0.65%, 1.10%, 2.32%, and 4.59%, respectively. Each group had triplicate tanks, and each tank was stocked with 30 fish. The results showed that compared to the control, dietary cholesterol supplementation had no significant effect on the growth of both turbot and tiger puffer. Nevertheless, excess dietary cholesterol (CHO-2.0 and CHO-4.0) led to significant lower weight gain of tiger puffer compared to CHO-1.0. The feed intake decreased with increasing levels of dietary cholesterol. In general, the cholesterol supplementation decreased the crude lipid content in the liver, whereas 0.5% dietary cholesterol supplementation tended to increase the crude lipid content in the muscle of both species. Dietary cholesterol supplementation significantly regulated the lipid-related biochemical parameters in serum, liver, and muscle, and compared to turbot, tiger puffer lipid compositions had a higher buffering capacity in response to changes in dietary cholesterol level. Dietary cholesterol supplementation increased the 20:4n-6 content in the liver. Dietary cholesterol supplementation significantly downregulated the gene expression of HMG-COAr, upregulated the CYP7A1 expression, and downregulated the expression of lipid absorption and biosynthesis genes, but had no significant effect on gene expression of CPT1 and lipid transport-related genes (ApoA1, ApoA4, ApoB100, and ApoEα) in the liver. In conclusion, under the present experimental condition, dietary cholesterol supplementation had no significant effect on the growth of turbot and tiger puffer. In both species, dietary cholesterol supplementation significantly regulated the lipid accumulation and metabolism. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was conducted in a flow-through seawater system to investigate the effects of lysophosphatidylcholine (LPC) on growth performance and lipid metabolism of turbot. Four experimental diets were prepared, differing only in the LPC supplementation, namely, 0 (LPC-0, control), 0.1 (LPC-0.1), 0.25 (LPC-0.25), and 0.5% (LPC-0.5) of dry matter. Each diet was randomly fed to triplicate tanks. LPC-0.1 and LPC-0.25 led to significantly higher weight gain than the control diet, and the highest weight gain was observed in LPC-0.1. Compared to the control group, the LPC-supplemented groups had higher survival and lower hepatosomatic index and viscerosomatic index. LPC-0.25 led to significantly lower contents of crude lipid and ash in whole fish. Dietary LPC supplementation led to a basic decrease in the lipid metabolism-related biochemical parameters in serum but had only very minor influence on the fatty acid composition in the liver and subcutaneous tissue around the fin (STF). High LPC levels upregulated the mRNA expression of BSAL and ApoEα in both the liver and STF. In conclusion, dietary LPC supplementation (0.1-0.25%) enhanced the growth, lowered the lipid accumulation in juvenile turbot, and significantly regulated the lipid metabolism. However, it seldom influenced the fatty acid composition. [ABSTRACT FROM AUTHOR]

Taurine (TAU) plays important roles in the metabolism of bile acids, cholesterol and lipids. However, little relevant information has been available in fish where TAU has been identified as a conditionally essential nutrient. The present study aimed to investigate the effects of dietary TAU on the metabolism of bile acids, cholesterol and lipids in tiger puffer, which is both an important aquaculture species and a good research model, having a unique lipid storage pattern. An 8-week feeding trial was conducted in a flow-through seawater system. Three experimental diets differed only in TAU level, that is, 1·7, 8·2 and 14·0 mg/kg. TAU supplementation increased the total bile acid content in liver but decreased the content in serum. TAU supplementation also increased the contents of total cholesterol and HDL-cholesterol in both liver and serum. The hepatic bile acid profile mainly includes taurocholic acid (94·48 %), taurochenodeoxycholic acid (4·17 %) and taurodeoxycholic acid (1·35 %), and the contents of all these conjugated bile acids were increased by dietary TAU. The hepatic lipidomics analysis showed that TAU tended to decrease the abundance of individual phospholipids and increase those of some individual TAG and ceramides. The hepatic mRNA expression study showed that TAU stimulated the biosynthesis of both bile acids and cholesterol, possibly via regulation of farnesoid X receptor and HDL metabolism. TAU also stimulated the hepatic expression of lipogenic genes. In conclusion, dietary TAU stimulated the hepatic biosynthesis of both bile acids and cholesterol and tended to regulate lipid metabolism in multiple ways. [ABSTRACT FROM AUTHOR]

Long non-coding RNAs (lncRNA) have emerged as important regulators of lipid metabolism and have been shown to play multifaceted roles in controlling transcriptional gene regulation, but very little relevant information has been available in fish, especially in non-model fish species. With a feeding trial on a typical marine teleost tongue sole C. semilaevis followed by transcriptomic analysis, the present study investigated the possible involvement of lncRNA in hepatic mRNA expression in response to different levels of dietary DHA and EPA, which are two most important fatty acids for marine fish. An 80-day feeding trial was conducted in a flow-through seawater system, and in this trial three experimental diets differing basically in DHA/EPA ratio, i.e., 0.61 (D/E-0.61), 1.46 (D/E-1.46), and 2.75 (D/E-2.75), were randomly assigned to 9 tanks of experimental fish. A total of 124.04 G high quality genome-wide clean data about coding and non-coding transcripts was obtained in the analysis of hepatic transcriptome. Compared to diet D/E-0.61, D/E-1.46 up-regulated expression of 178 lncRNAs and 2629 mRNAs, and down-regulated that of 47 lncRNAs and 3059 mRNAs, while D/E-2.75 resulted in much less change in gene expression. The co-expression and co-localization analysis of differentially expressed (DE) lncRNA and mRNA among dietary groups were then conducted. The co-expressed DE lncRNA and mRNA were primarily enriched in GO terms such as Metabolic process, Intracellular organelle, Catalytic activity, and Oxidoreductase activity, as well as in KEGG pathways such as Ribosome and Oxidative phosphorylation. Overlap of co-expression and co-localization analysis, i.e., lncRNA–mRNA matches "XR_523541.1–solute carrier family 16, member 5 (slc16a5)" and "LNC_000285–bromodomain adjacent to zinc finger domain 2A (baz2a)," were observed in all inter-group comparisons, indicating that they might crucially mediate the effects of dietary DHA and EPA on hepatic gene expression in tongue sole. In conclusion, this was the first time in marine teleost to investigate the possible lncRNA–mRNA interactions in response to dietary fatty acids. The results provided novel knowledge of lncRNAs in non-model marine teleost, and will serve as important resources for future studies that further investigate the roles of lncRNAs in lipid metabolism of marine teleost. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to comprehensively investigate the effects of dietary phosphorus level and stocking density on tiger puffer. A 3 × 3 factorial design was used. The three dietary phosphorus levels were 0.68% (LP), 0.98% (MP), and 1.31% (HP) of dry matter, of which the available phosphorus level was 0.44%, 0.76%, and 1.06%, respectively. The three stocking density grades were 1.53 (LD), 2.30 (MD), and 3.06 (HD) kg m−3. The feeding trial was conducted in an indoor flow-through seawater system. Three replicate tanks were used for each group. The results showed that HP resulted in the highest growth rate. Higher dietary phosphorus levels reduced the whole-body lipid content, serum cholesterol contents, and hepatic mRNA expression of lipid metabolism-related genes such as ACACβ, DGAT1, and PPARα2. High stocking density levels reduced the growth rate and feed intake, but rarely affected other physiological parameters. Significant interactions were observed between effects of dietary phosphorus level and stocking density on phosphorus and calcium metabolism, but not between effects of both variables on the growth performance. Synergetic enhancement of phosphorus excretion by high phosphorus level and high stocking density was observed. These results shed new lights into the phosphorus physiology of marine fish and the interactions between phosphorus nutrition and rearing condition. • Tiger puffer had a high requirement for dietary phosphorus. • High dietary phosphorus levels reduced the lipid deposition. • High stocking density levels reduced the growth rate and feed intake. • Significant interaction was observed regarding phosphorus and calcium metabolism. • Significant interaction was not observed regarding growth performance. [ABSTRACT FROM AUTHOR]

Bile acid (BA) plays an important role in lipid metabolism. Tiger puffer has a unique lipid storage pattern; storing lipid predominantly in the liver. The present study aimed to investigate the effects of dietary BA supplementation on hepatic lipid accumulation and metabolism in tiger puffer fed normal or high-lipid diets. An 8-week feeding trial was conducted in an indoor flow-through seawater system. Two diets with suitable (8.5%, diet C) or high lipid level (12.5%, diet HL) were prepared. BA, a porcine bile extract mainly comprised of hyodeoxycholic acid was supplemented into the two diets at the level of 0.02% to formulate diet CBA and diet HLBA, respectively. A fifth diet was prepared by supplementing an excess level of porcine bile extract (0.10%) into diet C (diet CHBA). Each diet was randomly fed to triplicate tanks. Dietary BA supplementation did not significantly affect fish growth performances. Dietary BA tended to decrease the whole-body lipid content, liver lipid content, hepatosomatic index, and viscerasomatic index in both fish fed with normal diets and fish fed with high-lipid diets. Similar results were observed for the contents of triacylglycerol, total cholesterol, and low-density lipoprotein-cholesterol in serum. The quantitative bile acid metabolomics analysis showed that taurocholic acid and taurochenodeoxycholic acid were dominantly abundant in the gallbladder. Dietary BA supplementation increased the concentration of taurohyodeoxycholic acid, glycohyodeoxycholic acid, and glycocholic acid, but affected some other BAs in various patterns. Dietary BA regulated hepatic transcription of lipid metabolism-related genes differentially in fish fed normal diets and fish fed high-lipid diets, decreasing the transcription of lipogenic genes in fish fed normal diets but increasing the transcription of genes related to lipid digestion and lipid/cholesterol transport in fish fed high-lipid diets. In conclusion, dietary BA supplementation tended to reduce the lipid accumulation in juvenile tiger puffer. However, at the transcription level the regulation of lipid metabolism by dietary BA seemed very different between fish fed normal diets and fish fed high-lipid diets. This study contributes to the general knowledge of bile physiology under different nutritional conditions in teleost and is beneficial to lipid management in tiger puffer farming. • Dietary bile acid tended to decrease hepatic lipid accumulation and serum triacylglycerol and cholesterol levels. • Dietary bile acid increased the contents of taurochenodeoxycholic acid and taurohyodeoxycholic acid in the gallbladder. • Dietary bile acid regulates gene transcription differentially in fish fed normal diets and fish fed high-lipid diets. • Dietary bile acid decreased the transcription of lipogenic genes only in fish fed normal diets. [ABSTRACT FROM AUTHOR]