Regulatiive Mechanism Of Choline On Lipid Metabolism In Blunt Snout Bream Megalobrama Amblycephala

In recent years, the intensive and high-density aquaculture develop rapidly, meanwhile,diet with low protein and high energy is used widely. High fat often induce lipid metabolism and physiological disorders of fish, even lead to fatty liver disease, which also insult growth performance, feed efficiency and resistence to disease, as well as increase death rate, consequently, make a big economic loss in fish farming. In order to sustain the healthy aquaculture,it is critically impotant to investigate the way to mitigate the lipid metabolism derangements. Previous studies have shown choline may be a lipotropic factor.This study was conducted to evaluate the effects of choline on lipid metabolism,antioxidant capacity, inmmunity and so on. In adition, the regulative mechanism of this species has also been researched.1 Effects of choline on growth performance, body composition and intestinal enzyme activities of blunt snout bream Megalobrama amblycephalThis study aimed to investigate the effects of choline on growth performance, body composition and intestinal enzyme activities of blunt snout bream Megalobrama amblycephala (average initial weight: 42.20±0.34 g). Fish were fed four diets with two lipid levels (5% and 15%) and two choline levels (1200 mg/kg and 2200 mg/kg) in an indoor circulatory system for eight weeks. Feed conversion ratio (FCR), viscerosomatic index (VSI), hepatosomatic index (HSI), whole-body and muscle lipid contents, intestinal lipase activities and tissue lipoprotein lipase (LPL) activities all increased significantly(P<0.05) as increasing dietary lipid, whereas the opposite was true for whole-body and muscle moisture contents as well as intestinal amylase activities. VSI, IPF ratio and whole-body lipid contents all decreased significantly (P<0.05) with increasing dietary choline. In addition, there is an interaction between dietary lipid and choline on weight gain,which significantly (P<0.05) higher in fish fed 15% lipid and 2200 mg/kg choline than that in any other groups. The result of this study indicated that extra choline supplementation can improve growth performance, intestinal enzymes activities and reduce the excessive lipid deposition of Megalobrama amblycephala fed high-fat diet.2 Effects of choline on physiological status, liver histology and immunity of blunt snout bream Megalobrama amblycephalThis study aimed to delineate the potentially beneficial effects of choline on the health status of blunt snout bream Megalobrama amblycephala fed high-lipid diet, with special reference to biochemistry and physiology, innate immunity and liver histopathology. The experimental design was the same as study one. After the feeding trial, liver lipid and triglyceride contents,plasma triglyceride levels as well as aspartate aminotransferase (AST)and alanine aminotransferase (ALT) activities all increased significantly (P<0.05) as dietary lipid levels increased,whereas,blood leucocyte counts,plasma lysozyme activity and total protein and globulin contents decreased significantly (P<0.05). A large munber of fat droplets were found in fish fed 15% lipid and 1200 mg/kg choline, additionally, obvious ultrastructure abnomalities were observed in the hepatocytes with apparent alterations involving mitochondrion, endoplasmic reticulum, nucleus and cell membrane. The results indicated the hepatic structure damage and reduced immunity induced by high-fat.However, liver lipid content, plasma aminotransferase activities decreased significantly(P<0.05) with increasing choline in fish fed 15% lipid, whereas the opposite was true for blood leucocyte counts, plasma lysozyme activity and globulin contents. However, the liver histology of fish fed 15% lipid and 2200 mg/kg was quite normal. The results of this study indicated that choline could play several important role in fish, involving in maintain structure and function of liver, strengthen immunity and keep the healthy of fish.3 Regulation of choline for lipid deposition and transport of blunt snout bream Megalobrama amblycephalThis study aimed to elucidate the choline metabolic pathways and its effects on hepatic lipid deposition and transport in blunt snout bream Megalobrama amblycephala (average initial weight: 9.80±0.35g). Fish were fed six experimental diets containing three lipid levels (5%, 8% and 11%) and two choline supplementation levels (1200 mg/kg and 1800 mg/kg) for 8 weeks. After the feeding trial, viscerosomatic index (VSI), hepatosomatic index (HSI),plasma aspartate aminotransferase(AST),plasma triglycerides and cholesterol content, as well as liver lipid content all increased significantly (P<0.05) as dietary lipid levels increased from 5 to 11% in terms of dietary lipid levels, whereas, hepatic S-adenosylmethionine (SAM) content showed the opposite trend. Feed conversion ratio,cholesterol content and liver lipid content decraesed significantly (P<0.05) with increasing dietary choline, however, hepatic SAM and GSH level, expression abundance of MTTP and apoB-100 elevated significantly as increasing choline. Additionally, Hepatic lipid accumulation was further observed by oil red O staining. Weight gain increased significantly (P<0.05) with increasing dietary choline when dietary lipid reached 11%. The results suggested that choline could increase SAM production, up-regulated the expression levels of MTTP and ApoB-100, which induced VLDL synthesis and assembly, thus enhanced the hepatic lipid transfer and reduced lipid deposition.4 Cloning and characterization of microsomal triglyceride transfer protein gene and its potential connection with peroxisome proliferator-activated receptor (PPAR) in blunt snout bream(Megalobrama amblycephala)In this study, MTTP of blunt snout bream Megalobrama amblycephala was firstly cloned and sequenced using a RACE asays. MTTP expression abundance in different tissues has also been assessed. In addition, effects of choline on MTTP and PPARα、βexpression in liver, muscle and intestine, as well as the association of MTTP and PPARs in lipid metabolism have been researched. The experimental design was the same as study three. The full-length cDNA covered 3457 bp with an open reading frame of 2661 bp,which encoding 886 amino acids, including a putative signal peptide of 24 amino acids long. The MTTP had a calculated molecular weight of 97482.5 Da and PI of 7.95. A graded tissue-specific expression pattern of M7TP was observed and high expression abundance in liver and intestine indicated its major function in lipid transport in this fish species. MTTP expression abundance in muscle and kidney was a little lower, and in spleen, eyes and gills was the lowest. Elevated dietary lipid levels significantly (P<0.05) increased the liver and muscle MTTP mRNA abundance. Expressions of PPARa, β in the liver and muscle showed similar to the trend of MTTP expression. The results suggested the potentially coordinate connection of MTTP and PPARs in lipid metabolism. Furthermore, choline could enhance fatty acid oxidation, which indicated a molecular mechanism of choline on diminishing fat accumulation in blunt snout bream.5 Effects of choline on insulin signaling in blunt snout bream Megalobrama amblycephalaThis study aimed to investigate the effects of choline on insulin signaling pathway and its relation with lipid metabolism in high-fat fed-blunt snout bream Megalobrama amblycephala (average initial weight: 56.80±0.50 g). Fish were fed diets with two lipid levels (5% and 11%) and two choline levels (1200 -mg/kg and 1800 mg/kg) for eight weeks. After the feeding trial, fish plasma insulin levels, expression abundances of hepatic and muscle insulin receptor (IR), insulin receptor substrate 1 (IRS1) and that of IRS2 in liver, as well as phosphatidylinositol 3-kinase (PI3K) and protein kinase B (PKB)activities were reduced significantly (P<0:05) as dietary lipid levels increased. However,increased choline significantly reduced plasma glucose and insulin levels, provoked action of insulin signaling factors, additionally enhanced acetyl-COA carboxylase (ACC), fatty acids synthase (FAS) and Carnitine palmitoyltransferase I (CPT I) expression levels. In conclusion, extra choline might be effective to mitigate high fat-induced insulin signaling hinderance,improve metabolic and physiological status in fish.6 Effects of choline on mitochondria function, oxidative stress and induced apoptosis in blunt snout bream Megalobrama amblycephalaThis study aimed to investigate the possible effects of dietary choline on hepatocytes mitochondria function, oxidative stress and induced apoptosis in blunt snout bream Megalobrama amblycephala fed a high-fat diet. The experimental design was the same as study five. After the feeding trial, activities of mitochondria Na+-K+-ATPase and succinate dehydrogenase (SDH), as well as respiratory chain complex I and III were all decreased significantly (P<0.05) as increasing dietary lipid,which suggest the damage of mitochondria function. However, mitochondria enzyme activities, espiratory chain complexes were increased significantly as increasing choline in diet, while, hepatic reactive oxygen species (ROS) and malondialdehyde (MDA) concentrations showed the opposite trend. Additionally, the increased choline declined the amount of TUNEL-stained apoptosis cells in the high-fat diet. Overall,extra choline might improve mitochondrial bioenergetics and functions, strengthen the ability to protect against oxidative stress.7 Regulation of choline for the DNA methylation of CPT I promoter of blunt snout bream Megalobrama amblycephalaThis study aimed to investigate the regulation of choline for the methylation of CPT I promoter of blunt snout bream Megalobrama amblycephala fed a high-fat diet, as well as the association with CPTI gene expression. The experimental design was the same as study five. MTTP, ApoB-100 and CPT I DNA promoter were cloned and sequenced from blunt snout bream. No CpG island was found in MTTP, ApoB-100 DNA promoter, but one CpG island was observed in CPT I DNA promoter,the length of this CpG island was 150bp,from -725 to -576 in 5-upstream region, and the CpG island included 14 CpG sites.Through CPT I DNA methylation analysis, significant differences in average level of CpG methlation and the CpG sites were observed in different experimental groups. The methlation level of CPT I promoter significantly (P<0.01) elevated as increasing dietary lipid, but significantly (P<0.01) reduced as increasing dietary choline. Additionally, an interaction between lipid and choline was also observed, the CpG methlation level was highest in fish fed with 5% lipid and 1800 mg/kg choline, but lowest in that with 11% lipid and 1200 mg/kg choline. CpG methylation sites also have remarkable differences in fish fed with different lipid and choline levels. DNA methylation happened at the CpG 3, 4, 9 and 10 sites in fish fed with 5% lipid and 1200 mg/kg choline, but the CpG 6, 8, 13 and 14 sites were methylated in fish fed with 1800 mg/kg choline at the same lipid level. In group of 11% lipid and 1800 mg/kg choline, DNA methylation happened only at the CpG 5 site,but at CpG 2, 3 and 11 sites in fish with 11% lipid and 1800 mg/kg choline. Additionally,mRNA expression abundance showed the similar trend with that of methylation level. In aword, DNA methylation of CPT I promoter may have associated relations with CPT I gene expression. Furthermore, the differences in DNA methlation level and CpG sites may be the molecular mechanism of its regulation, thus affect lipid metabolism in blunt snout bream.