Molecular characterization of lipoprotein lipase from blunt snout bream Megalobrama amblycephala and the regulation of its activity and expression by dietary lipid levels

摘要

A full-length cDNA coding lipoprotein lipase (LPL) was cloned from the visceral adipose tissue of blunt snout bream Megalobrama amblycephala by RT-PCR and rapid amplification of cDNA ends (RACE) approaches. The cDNA obtained covered 2372 bp with an open reading frame of 1524 bp encoding 507 amino acids, including a putative signal peptide of 22 amino acids long. Sequence alignment and phylogenetic analysis revealed a high degree of conservation (63-97%) among most fish and higher vertebrates, retaining the consensus sequence, the polypeptide "lid", the catalytic triad and eight cysteine residues at the N-terminal region. Then, a 10-week feeding trial was conducted to investigate the effects of dietary lipid levels (4%, 8% and 12%) on the activity and mRNA expression of LPL in M. amblycephala. LPL activities in the visceral adipose tissue and white skeletal muscle both increased significantly (P < 0.05) with increasing dietary lipid levels, whereas no significant difference (P > 0.05) was also observed in that of the liver. LPL expressions in the visceral adipose tissue, liver and white skeletal muscles all increased significantly (P < 0.05) as dietary lipid levels increased. In addition, a graded tissue-specific expression pattern of LPL (visceral adipose tissue > liver > white skeletal muscle) was also observed. The results indicated that LPL gene of M. amblycephala showed a typical structure of the lipase family, and shared a high similarity with that of the other vertebrates. In addition, an up-regulation of both LPL expressions and activities was observed in various tissues by high dietary lipid levels