| Due to the importance of dietary lipid utilization in fish rearing, increasing attention has been paid to different aspects of fish lipid nutrition. However, different explanations have been proposed but the exact mechanisms behind these observations have not been completely clarified. So this study was conducted to investigate that the lipid level and source effect the growth and lipid metabolism related gene expression of freshwater omnivorous darkbarbel catfish, Pelteobagrus vachelli.1 Cloning and tissues expression of the lipid metabolism related gene in darkbarbel catfish, Pelteobagrus vachelliTo investigated the lipid nutritional regulation of lipid molecular metabolism of fish, hepatic lipase (HL), fatty acid binding protein (FABP), fatty acid synthase (FAS) and carnitine acetyltransferase (CAT) gene of darkbarbel catfish P. vachelli were isolated from the liver. (1):The partial cDNA of HL (1065bp) was cloned, and was capable of encoding 343 amino acids residues, and showed significant identity to the HL gene of Danio rerio (73%). The partial deduced amino acids residues carried conserved features of this family, and found the"lid"sites. HL gene mRNA expression was detected in liver, but not in gill, muscle, intestine, spleen, heart and brain. (2)The length of cloned liver and heart FABP (L-and H-FABP) cDNA sequences were 335 and 425bp, and encoded 111 and 114 amino acids residues, respectively. Homologous alignment analysis showed L-and H-FABP gene had 82% and 85% identity to that of Cyprinus carpio and Rutilus rutilus, respectively. FABP gene mRNA was mainly distributed in liver, visceral adipose tissue, muscle and heart for liver FABP, and in liver, visceral adipose tissue and heart for heart FABP. (3):The partial cDNA of FAS gene consisted of 674bp, finding 216 amino acids residues. Sequence comparison showed that the partial FAS amino acids residues had the highest identity with D. rerio (90%). FAS transcripts were detected in all sampled tissues, and significantly distributed in liver, visceral adipose tissue, muscle, intestine, heart. (4):cDNA encoding CAT mRNA was obtained from the liver, partial cDNA with 494bp encoded 156 amino acids residues. Comparison the sequence of CAT amino acids residues showed the highest identity with D. rerio (81%).2 Effect of lipid sources on the growth and expression of related metabolism gene of lipid of darkbarbel catfish, Pelteobagrus vachelliThe effects of dietary lipid sources on fatty acid absorption and expression regulation of genes related to lipid metabolism in darkbarkbel catfish, Pelteobagrus vachelli, were evaluated. Fingerlings of P. vachelli (1.0±0.2 g) were fed five experimental diets with fish oil (FO), soybean oil (SO), pig oil (PO),75% fish oil and 25% soybean oil (Mix group 1), 25% fish oil and 75% soybean oil (Mix group 2) as lipid sources respectively for 80 days. Fish weight gains of SO, M1 and M2 groups were similar to those of FO group, but total replacement of fish oil by PO significantly reduced fish weight gain (P<0.05). Though there were increasing trends in hepatosomatic index (HSI) and intraperitoneal fat ratio (IPF) of fish feeding SO, M1, M2 and PO deits, no significant differences were found (P<0.05). Fish of PO group had higher SFA fraction and lower PUFA fraction in feces relative to those feeding FO diets. Fish of SO, M1 and M2 groups had significantly higher PUFA fraction and lower SFA fraction (p<0.05) in feces, and the PUFA fraction in feces increased with the replacement content of fish oil by soybean oil. Furthermore, replacement of fish oil with SO, PO and 75% SO could significantly increased the fatty acid binding protein (FABP) and fatty acid synthase (FAS) gene expressions in liver and adipose tissue (P<0.05), and significantly reduced the carnitine acyltransferase gene expression in liver (P<0.05). No significant changes were found in lipoprotein lipase (LPL) gene expression in liver and adipose tissue, and hepatic lipase (HL) gene expression in liver (P<0.05). All these findings could suggest that soybean oil could increase lipid biosynthesis and slow down the lipid catabolism of P. vachelli. Therefore, partly replacement of fish oil by soybean oil did not reduce the weight gain of darkbarkbel catfish.3 Effect of lipid level on the growth and expression of related lipid metabolism gene of lipid of darkbarbel catfish, Pelteobagrus vachelliAn experiment was conducted to determine the effect of dietary lipid levels on growth performance and expression regulation of genes of darkbarbel catfish, P. vachelli juveniles cultured in plastic boxes. Three isonitrogenous diets (42% dietary protein) with increasing dietary lipid concentration (5%,11%,20% of dry material, DM) were fed to satiation to triplicate groups of 30 fish (mean weight:1.0±0.1 g) for 70 days. Fish weight gains of 5% lipid and 11% lipid groups were similar, but weight gains of 20%lipid group significantly reduced (P<0.05). Furthermore, intraperitoneal fat ratio (IPF) significantly increased with lipid level (P<0.05), but no significant differences were found for hepatosomatic index (HSI) between different lipid level diets (P<0.05). Furthermore, in liver, the mRNA expression of LPL, HL and L-FABP significantly increased, FAS and CAT significantly reduced with the augment of diet lipid level (P<0.05). In visceral adipose tissue, gene expression characterization of lipid metabolism was multiplex. Both LPL and L-FABP mRNA expression were the highest in 5% lipid group. The 20% lipid group significantly increased the expression of CAT mRNA, but there was no significant difference between 5% lipid and 11% lipid groups. CAT mRNA was the highest in 20% lipid group. However, the FAS transcripts was decreased with increasing of dietary lipid level (P<0.05), but there was no significant difference between 11% and 20% lipid groups. These results suggested that increasing dietary lipid level could induce the metabolism of lipid in liver and visceral adipose tissue, and reduce the lipid biosynthesis.4 Effect of murine leptin injections on expression of the related metabolism gene of lipid of darkbarbel catfish, Pelteobagrus vachelliAn experiment was conducted to determine the effect of leptin on regulation of genes related to lipid metabolism in darkbarkbel catfish, Pelteobagrus vachelli, were evaluated. The darkbarbel catfish, P. vachelli, (30±0.5g) were injected daily with higher murine leptin (20μg/100μl), lower murine leptin (5μg/100μl), phosphate-buffered saline (PBS), or simply handled without injection for 15 days. At the end of the experiment, fish were assayed for expression regulation of genes related to lipid metabolism in liver. Injecting leptin could remarkably increase the mRNA expression of CAT and L-FABP, but no significant difference was found between high and low concentration. Though there were increasing trends with leptin injection for HL and LPL mRNA expression, but no significant differences were found in all groups (P<0.05). However, the FAS mRNA expression in leptin treated groups was significantly decreased. These results suggest that fish respond to murine leptin injections by increasing fat transport, and depressing the lipid biosynthesis. |
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