Effects Of Dietary Lipid Levels And Types Of Fatty Acids On Lipid Deposition In Large Yellow Croaker(Larmichthys Crocea)

This study was conducted to investigate the effects of dietay lipid levels and types of fatty acids on growth, plasma biochemiacal indexes and expression of lipid deposition related genes in large yellow croaker (Larmichthys crocea). On basis of these studies, it was aimed to investigate mechamisms involved in the regulation of ditary lipid levels and fatty acid on lipid deposition of large yellow croaker. The results and conclusions are summarized as follows: 1. Effects of dietary lipid levels on growth, plasma biochemical indexes and lipid deposition of large yellow croaker (Larmichthys crocea)Large yellow croaker (150.0±4.9 g) were fed one of three diets with a low (6%), moderate (12%, the control diet) or high (18%) crude lipid content for 10 weeks. Growth performance, plasma biochemical indexes, tissues lipid contents and gene expression related to lipid deposition, including lipoprotein assembly and clearance, fatty acid uptake, triacylglycerol synthesis and catabolism, were assessed. Growth performance was not significantly affected by dietary lipid levels (P>0.05). However, the hepato-somatic index, viscera-somatic index, contents of plasma triacylglycerol. non-esterified fatty acids and LDL-cholesterol were significantly increased in fish fed the high-lipid diet (P<0.05). For fish fed the low-lipid diet in liver, to some extent, uptake of lipoprotein and fatty acid as well as triacylglycerol synthesis increased, triacylglycerol catabolism and secretion decreased, but hepatic lipid content decreased due to the lower ingested dietary lipids. Although fatty acid uptake was possibility increased, lipid content in muscle of fish fed the low-lipid diet was reduced potentially by decreased lipoprotein clearance and triacylglycerol synthesis, together with sufficience of lipid source. In liver of fish fed the high-lipid diet, increased lipoprotein clearance and fatty acid uptake and decreased triacylglycerol catabolism were potentially involved in the increased hepatic lipid deposition, and it could also reduce lipid deposition by liver through increased lipoprotein secretion and decreased triacylglycerol synthesis. In muscle of fish fed the high-lipid diet, decreased uptake of lipoprotein and fatty acid as well as triacylglycerol synthesis potentially related to inhibition of excessive lipid deposition. In abdominal adipose tissue of fish fed high-lipid diet, uptake of lipoprotein and fatty acid as well as triacylglycerol synthesis were possibly increased in order to increase lipid depositin. However, lipolytic rate of adipose tissue in fish fed high-lipid diet was potentially increased, and the lipid content of adipose tissue decreased to some extent compared to fish fed the control diet. Therefore, regulation of lipid deposition was complex by dietary lipid levels among different tissues, probably in a tissue-specific manner.2. Effects of dietary saturated and monounsaturated fatty acids on growth, plasma biochemical indexes and lipid deposition of large yellow croaker (Larmichthys crocea)Large yellow croaker (151.0 ± 3.5 g) were fed one of three diets containing high level of long chain-polyunsaturated fatty acid (FO). palmitic acid (PA) and oleic acid (OO) for 10 weeks. Growth performance, plasma biochemical indexes, gene expression involved in lipid deposition, including lipoprotein assembly and clearance, fatty acid uptake, triacylglycerol synthesis and catabolism. were investigated. The results showed that weight gain rate was not significantly different in fish fed diets with PA and FO (P>0.05). while it was significantly reduced in fish fed OO diet compared with FO group (P<0.05). Hepato-somatic index and viscera-somatic index were significantly lower in the PA group compared with the OO group (P<0.05), however, there were no significant difference between the PA and the FO groups (P>0.05). Plasma concentrations of triacylglycerol, total cholesterol, HDL-cholesterol, LDL-cholesterol were not significantly affected by dietary treatments (P>0.05). Plasma non-esterified fatty acids level was the highest in the OO group, which was approximately 2-fold higher compared to the PA group. The decreased lipid content of liver and muscle in the PA group was possibly related to increased capacity of lipoprotein secretion and (3-oxidation in liver, as well as decreased TAG synthesis and increased β-oxidation in muscle. On the contrary, the OO diet-fed fish increased lipid accumulation in liver and muscle. The increased uptake of lipoprotein and fatty acid and unchanged β-oxidation were potentially important factors which resulted in increased hepatic lipid content in the OO group. In addition, higher lipid content in muscle of fish fed the OO diet could be due to increased uptake of lipoprotein and fatty acid and higher TAG synthesis. Althouth the lipid content in adipose tissue was not significantly affected by dietary treatments, expressions of ATGL were at a higher level in the adipose tissue of fish fed the 00 diet, and the increased lipolytic rate of adipose tissue could be an important factor of lipid accumulated in liver of large yellow croaker.3. Effects of dietary linoleic acid and linolenic acid on growth, plasma biochemical indexes and lipid deposition of large yellow croaker (Larmichthys crocea)Large yellow croaker (151.5 ± 3.9 g) were fed one of three diets containing high level of long chain-polyunsaturated fatty acid (FO), linoleic acid (SO) and linolenic acid (PO) for 10 weeks. Growth performance, plasma biochemical indexes, gene expression involved in lipid deposition, including lipoprotein assembly and clearance, fatty acid uptake, triacylglycerol synthesis and catabolism, were investigated. The results showed that weight gain rate, survival rate and hepato-somatic index was not significantly affected by dietary treatments (P>0.05), while viscera-somatic index was significantly higher in the SO group compared with the FO group (P<0.05). Plasma concentrations of triacylglycerol. HDL-cholesterol and non-esterified fatty acids showed no significant difference among dietary treatments (P>0.05). Plasma total cholesterol level in the PO group and LDL-cholesterol levels in the SO and PO groups were significantly higher compared to the FO group (P<0.05). There was no significant difference about the lipid content of the whole body, muscle and adipose tissue among the three groups (P>0.05). while the hepatic lipid contents in the SO and PO groups were significantly increased compared to the FO group (P<0.05). The increased hepatic uptake of lipoprotein and fatty acid could be major reasons which led to hepatic lipid deposition in the SO group. Although liver could reduce lipid deposition through decreased triacylglycerol synthesis, increased triacylglycerol catabolism and secretion, these different metabolism pathways was still not enough to inhibit lipid deposition of liver in the SO group. The hepatic lipid content increased in the SO group which was possibly due to increased lipoprotein clearance and fatty acid uptake. In spite of hepatic triacylglycerol secretion was potentially increased, it could not transport much enough hepatic lipid. Furthermore, expressions of ATGL were significantly higher in the adipose tissue. The increased lipolytic rate of adipose tissue in the SO and PO groups could be an important factor of lipid accumulated in liver of large vellow croaker.4. Analysis of expression profiling of large yellow croaker (Larmichthys crocea) liver genes under different dietary fatty acidsA transcriptome library was constructed using Illumina HiSeqTM 2000/MiseqTM high-through sequencing based on the mix of large yellow croaker brain, stomach, intestine, kidney, heart, muscle, abdominal adipose tissue and liver from different dietary treatments (FO. SO and PO).126963 Unigene were obtained, which ranged from 201 bp to 29701 bp. with an average length of 795 bp.28586 Unigene were annotated with an alignment between Unigene and NR database, with an successive annotation rate of 22.51%. On basis of the transcriptome library, digital gene expression profiling of large yellow croaker liver from the three dietary fatty acids treatments. The results showed that expression of some genes significantly affected by dietary different types of fatty acids. Compared to the FO group, differential genes were mainly found to be focused on metabolism process and catalytic activity in the SO group, while differential genes showed to be concentrated in oxidation-reduction process, carboxylic acid metabolic process, oxoacid metabolic process, organic acid metabolic process and oxidoreductase activity in the PO group. The signaling pathways of P13K-Akt and TNFa were participated in the regulation of lipid deposition by dietary fatty acids.