Expression of Neuropeptide Y of GIFT Tilapia (Oreochromis sp.) in Yeast Pichia Pastoris and Its Stimulatory Effects on Food Intake and Growth

Neuropeptide YθNPYχ, a peptide with 36 amino acid residues which was first isolated from porcine brain (Tatemoto et al., 1982), is most highly expressed in the hypothalamic arcuate nucleus (ARC) (Lin et al., 2004). NPY is a member of the NPY family which consists of NPY, peptide YY (PYY), pancreatic polypeptide (PP) and peptide Y (PY)(Cerda-Reverter and Larhammar, 2000a). There are three NPY-related peptides were expressed in fish. They are NPY, peptide YY and peptide Y(Cerda-Reverter et al., 2000b; Sundstrom et al., 2008). Currently, NPY peptides or cDNA sequences have been obtained from many fish species including catfish, goldfish, sea bass, Atlantic cod, flounder, rainbow trout, zebrafish(Volkoff, 2006). As other low molecular weight secreted peptide, NPY is synthesized as larger peptide precursor which consists of a hydrophobic signal peptide, the mature peptide, the amidation-proteolytic site, and the carboxy-terminal extended peptide (Cerda-Reverter and Larhammar, 2000a). A partial cDNA coding for the mature peptide of NPY of tilapia (red tilapia, Oreochromis sp.) has been cloned and reported. The size of the sequence is of 192bp, which encodes a 28 a.a. signal peptide and the 36 a.a. mature peptide, while the sequence encoding carboxy-terminal extension aside the C-terminal of mature peptide has not been reported yet (Carpio et al., 2006). NPY is well known to be involved in many physiological functions, such as cardiovascular regulation, affective disorder, memory retention, neuroendocrine control and feeding in mammals(Pedrazzini, 2004). In fact, NPY has been considered as the most potent orexigenic peptide in mammals (Halford et al., 2004; Kalra et al., 1999; Valassi et al., 2008; Woods et al., 1998). Many studies have proved that NPY is also an important energy metabolism regulator of vertebrates. When fed with a high-carbohydrate diet; diabetic rats exhibit increased gene expression of the NPY in the hypothalamic ARC, and high-fat diet suppressed NPY expression(Chavez et al., 1998). Intraventricular administration of NPY has been shown to enhance carbohydrate and fat utilization in rats which leads to a significant