Cloning of lipoprotein lipase (LPL) and the effects of dietary lipid levels on LPL expression in GIFT tilapia (Oreochromis niloticus)

Genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) is an important aquaculture species. Lipoprotein lipase (LPL) is considered as a key enzyme in lipid metabolism and deposition. The present study was conducted to investigate the nutritional regulation of LPL in GIFT. We cloned and characterized the LPL gene from GIFT. Finally, we determined the effects of dietary lipid levels and refeeding on hepatic LPL gene expression in GIFT. The LPL gene of GIFT (Oreochromis niloticus) (O.nLPL) was 2,298 bp in length and encoded 515 amino acids. Sequence analysis showed that O.nLPL shared 57.3-87.9 % identity with LPLs from other piscine species. To study LPL expression patterns, juveniles GIFT were fed diets containing 3.7, 7.7 or 16.6 % crude lipid for 90 days and the expression of hepatic O.nLPL was examined using real-time PCR. The abundance of hepatic LPL mRNA increased with increasing dietary lipid. The expression of O.nLPL mRNA in the 16.6 % dietary lipid group was significantly higher than that of the 3.7 % lipid group (P < 0.05). The expression of O.nLPL was increased in GIFT following a 48-h fast and decreased 12 h after refeeding. Hepatic LPL mRNA returned to fasting levels 48 h after refeeding. In summary, high dietary lipid induced expression of liver O.nLPL, and expression of liver LPL is regulated by fasting and refeeding.