Institute of Brain Science, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
PLoS One. 2010 Dec 9;5(12):e15333. doi: 10.1371/journal.pone.0015333.
Obesity is a multifactorial disease that arises from complex interactions between genetic predisposition and environmental factors. Leptin is central to the regulation of energy metabolism and control of body weight in mammals.
METHODOLOGY/PRINCIPAL FINDINGS: To better recapitulate the complexity of human obesity syndrome, we applied N-ethyl-N-nitrosourea (ENU) mutagenesis in combination with a set of metabolic assays in screening mice for obesity. Mapping revealed linkage to the chromosome 6 within a region containing mouse Leptin gene. Sequencing on the candidate genes identified a novel T-to-A mutation in the third exon of Leptin gene, which translates to a V145E amino acid exchange in the leptin propeptide. Homozygous Leptin(145E/145E) mutant mice exhibited morbid obesity, accompanied by adipose hypertrophy, energy imbalance, and liver steatosis. This was further associated with severe insulin resistance, hyperinsulinemia, dyslipidemia, and hyperleptinemia, characteristics of human obesity syndrome. Hypothalamic leptin actions in inhibition of orexigenic peptides NPY and AgRP and induction of SOCS1 and SOCS3 were attenuated in Leptin(145E/145E) mice. Administration of exogenous wild-type leptin attenuated hyperphagia and body weight increase in Leptin(145E/145E) mice. However, mutant V145E leptin coimmunoprecipitated with leptin receptor, suggesting that the V145E mutation does not affect the binding of leptin to its receptor. Molecular modeling predicted that the mutated residue would form hydrogen bond with the adjacent residues, potentially affecting the structure and formation of an active complex with leptin receptor within that region.
CONCLUSIONS/SIGNIFICANCE: Thus, our evolutionary, structural, and in vivo metabolic information suggests the residue 145 as of special function significance. The mouse model harboring leptin V145E mutation will provide new information on the current understanding of leptin biology and novel mouse model for the study of human obesity syndrome.
肥胖是一种多因素疾病，它是由遗传易感性和环境因素之间复杂的相互作用引起的。瘦素在哺乳动物的能量代谢调节和体重控制中起着核心作用。
方法/主要发现：为了更好地概括人类肥胖综合征的复杂性，我们应用 N-乙基-N-亚硝基脲（ENU）诱变剂与一系列代谢测定相结合，在筛选肥胖小鼠的过程中发现了与瘦素基因所在的染色体 6 上的一个区域有关的连锁。对候选基因的测序发现了瘦素基因第三外显子中的一个新的 T 到 A 突变，导致瘦素前肽中的 V145E 氨基酸替换。瘦素（145E/145E）纯合突变小鼠表现出病态肥胖，伴随着脂肪肥大、能量失衡和肝脂肪变性。这进一步与严重的胰岛素抵抗、高胰岛素血症、血脂异常和高瘦素血症有关，这些都是人类肥胖综合征的特征。Leptin(145E/145E) 突变小鼠下丘脑抑制食欲肽 NPY 和 AgRP 的作用以及诱导 SOCS1 和 SOCS3 的作用减弱。给予外源性野生型瘦素可减轻 Leptin(145E/145E) 小鼠的过度摄食和体重增加。然而，突变的 V145E 瘦素与瘦素受体共免疫沉淀，表明 V145E 突变不影响瘦素与其受体的结合。分子建模预测，突变残基会与相邻残基形成氢键，可能会影响该区域与瘦素受体形成的活性复合物的结构。
结论/意义：因此，我们的进化、结构和体内代谢信息表明残基 145 具有特殊的功能意义。携带瘦素 V145E 突变的小鼠模型将为我们目前对瘦素生物学的理解提供新的信息，并为研究人类肥胖综合征提供新的小鼠模型。
