【摘要】 为明确食欲素(orexin)在西伯利亚鲟(Acipenser baerii)食欲调节中的作用，通过RACE技术克隆获得西伯利亚鲟orexin-like基因cDNA全长序列，并分析了其分子特征、组织表达模式及对摄食的调控功能。结果表明:该基因cDNA全长1 216 bp，包含1个471 bp的开放阅读框(ORF)，可编码156个氨基酸的前体蛋白，其中含39个氨基酸组成的信号肽及31个氨基酸的orexin-A成熟肽结构域(简称为orexinlike)，未包含类似于orexin-B的成熟肽结构域;系统进化分析表明，西伯利亚鲟orexin-like在鲟形目中高度保守，与哺乳动物orexin亲缘关系更接近于硬骨鱼类，且其orexin-like成熟肽区域无硬骨鱼类中普遍存在的氨基酸插入序列;组织分布结果显示，orexin-like基因在检测的14种组织中均有表达，前脑表达量最高，肝和直肠次之;西伯利亚鲟下丘脑和前脑orexin-like mRNA表达量在摄食后1 h显著降低，且在禁食1 d和7 d后显著升高;当腹腔分别注射100、200、400 ng/g体质量的orexin-like成熟肽后，西伯利亚鲟幼鱼3、6 h累计摄食量显著提升，同时伴随下丘脑中关键食欲调节基因pomc、cart、npy和agrp表达显著降低，前脑中pomc、agrp和npy表达显著上调，瓣肠中cck表达显著下降。研究表明，西伯利亚鲟orexin-like具有明确的促食欲作用，本研究可为阐明西伯利亚鲟摄食调控分子机制提供科学依据。更多还原

【Abstract】 The role of orexin in regulating the appetite of Siberian sturgeon (Acipenser baeri),was investigated by cloning the full-length cDNA sequence of an orexin-like gene with the RACE technology and then analyzing its molecular characteristics,tissue expression patterns,and regulatory functions of appetite. The cDNA of this gene was1 216 bp long,containing a 471 bp open reading frame (ORF) that encoded a precursor protein of 156 amino acids. This precursor protein included a 39 amino acid signal peptide and a 31 amino acid orexin. A mature peptide domain (denoted as orexin-like),without a domain similar to the orexin-B peptide. Phylogenetic analysis revealed that the orexin-like gene was highly conserved within the Acipenseriformes and showed a closer phylogenetic relationship to mammalian orexins than to those of teleosts. In particular,the orexin-like mature peptide region lacked the amino acid insertion commonly found generally in teleosts. Tissue distribution analysis revealed that the orexinlike gene was expressed in all 14 types of tissues examined,with its highest expression in forebrain,followed by liver and rectum. The mRNA expression levels of the orexin-like gene in the hypothalamus and forebrain decreased significantly 1 h after feeding,while it increased markedly after one day and seven days of fasting. Intraperitoneal injection of the orexin-like mature peptides at doses of 100,200,and 400 ng/g body weight significantly promoted cumulative food intake of juvenile Siberian sturgeon 3 h and 6 h after injection. This was accompanied with a significant decrease in expression of key appetite-regulating genes (pomc,cart,npy,and agrp) in hypothalamus; significantly upregulated expression of pomc,agrp,and npy in forebrain; and significantly downregulated expression of cck in valvula intestine. The study demonstrates that the orexin-like gene in Siberian sturgeon has a clear orexigenic effect. It provides a theoretical basis for elucidating the molecular mechanisms underlying appetite regulation of Siberian sturgeon.更多还原