Molecular Characterization of 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase (HMGR) in Grass Carp Ctenopharyngodon idellus and Its Regulation by Oxidized Fish Oil

Özet

3-Hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR) is a rate-limiting enzyme for cholesterol biosynthesis. The aim of this study was to identify HMGR molecular characterization in grass carp (Ctenopharyngodon idellus), and to evaluate regulation of its expression by oxidized fish oil. Specific primers were designed for 3’RACE and 5’RACE to gain HMGR cDNA sequence of grass carp and to clone full-length HMGR cDNA. This cDNA covered 3591 bp, with 2526 bp for the open reading frame (ORF), 77 bp for 5’-untranslated region (UTR) and 988 bp for 3’UTR. ORF encoded a protein consisting of 841 amino acids. The result revealed that HMGR mRNA is predominantly expressed in liver. Multiple alignments and phylogenetic analysis indicated that grass carp HMGR has a high degree of conservation with other fish species. A 10-week feeding trial was conducted to investigate effects of offering diets containing fresh and oxidized fish oil on HMGR expression in liver and intestine of grass carp. The results showed that HMGR expression in fish fed the diet containing oxidized fish oil was significantly higher than fish fed the fresh fish oil after 10, 20, 30 and 70 days of feeding. Serum diamineoxidase (DAO) activity of fish was also increased by oxidized fish oil.