The role of plasma membrane type sialidase gene Neu3 on the pathogenesis of type 2 diabetes mellitusin Japanese.

神经节苷脂是存在于细胞表面膜中的含唾液酸的鞘糖脂家族。一些证据表明，它们在调节广泛的生物学过程，包括细胞生长，细胞分化和跨膜信号转导中发挥重要的功能作用。质膜相关唾液酸酶（Neu 3）是神经节苷脂水解的关键酶，在调节细胞表面功能中起重要作用，我们利用人Neu 3 cDNA研究了在转基因小鼠中过表达Neu 3的影响。我们证明过表达人NEU 3的小鼠发展出与高胰岛素血症、胰岛增生和β细胞质量增加相关的糖尿病表型。与野生型相比，胰岛素刺激的胰岛素受体（IR）和胰岛素受体底物I的磷酸化显着减少，磷脂酰肌醇3-激酶和糖原合成酶的活动在转基因肌肉低。IR磷酸化作用 ...更多信息 在出现贫血之前，在年轻小鼠中S已经减弱。将NEU 3瞬时转染到3 T3-L1脂肪细胞和L 6肌细胞中引起IR信号的显著降低。响应于胰岛素，发现NEU 3经历酪氨酸磷酸化并随后与Grb 2蛋白结合，从而被激活并引起胰岛素信号传导的负调节。事实上，GM 1和GM 2（转基因组织中可能的唾液酸酶产物）的积累导致体外IR磷酸化的抑制，并且阻断与Grb 2的结合导致L 6细胞中受损的胰岛素信号转导的逆转。这些数据表明，NEU 3确实参与了胰岛素信号的控制，可能是通过调节神经节苷脂和Grb 2的相互作用，小鼠可以作为一个有价值的模型，为人类胰岛素抵抗diabetes.We还调查了可能的贡献，单核苷酸多态性（SNPs）在NEU 3的发展2型糖尿病。我们调查了298名日本2型糖尿病患者和两个对照日本人群中NEU 3基因的SNPs：一个由148名符合非糖尿病严格标准的老年受试者组成，包括年龄超过60岁和没有糖尿病证据（HbA 1c <5.6%），另一个由308名正常葡萄糖耐量（NGT）受试者组成。我们确定了8个SNPs和5个SNPs没有在其编码区的氨基酸取代。2型糖尿病患者中一个SNPs的等位基因频率显著高于老年正常人和NGT受试者，而其他SNPs的等位基因频率在这三组中基本相同。此外，在NGT受试者中，SNP与口服葡萄糖耐量试验的胰岛素敏感性指数显著降低相关。这些结果强烈表明，在日本，NEU 32基因中的SNP通过减少胰岛素信号传导与2型糖尿病的发展相关。少

Gangliosides are a family of sialic acid-containing glycosphingolipids present in the cell surface membranes. Several lines of evidence suggest their important functional roles in regulating a wide range of biological processes including cell growth, cell differentiation, and transmembrane signaling. Plasma membrane-associated sialidase (Neu3) is a key enzyme for ganglioside hydrolysis, thereby playing crucial roles in regulation of cell surface functions.We have investigated effects of overexpression in transgenic mice by using the human NEU3 cDNA. We demonstrated that mice overexpressing the human NEU3 develop diabetic phenotype associated with hyperinsulinemia, islet hyperplasia, and increased beta-cell mass. As compared with the wild type, insulin-stimulated phosphorylation of the insulin receptor (IR) and insulin receptor substrate I was significantly reduced, and activities of phosphatidylinositol 3-kinase and glycogen synthase were low in transgenic muscle. IR phosphorylation wa … More s already attenuated in the younger mice before manifestation of cemia. Transient transfection of NEU3 into 3T3-L1 adipocytes and L6 myocytes caused a significant decrease in IR signaling. In response to insulin, NEU3 was found to undergo tyrosine phosphorylation and subsequent association with the Grb2 protein, thus being activated and causing negative regulation of insulin signaling. In fact, accumulation of GM1 and GM2, the possible sialidase products in transgenic tissues, caused inhibition of IR phosphorylation in vitro, and blocking of association with Grb2 resulted in reversion of impaired insulin signaling in L6 cells. The data indicate that NEU3 indeed participates in the control of insulin signaling, probably via modulation of gangliosides and interaction with Grb2, and that the mice can serve as a valuable model for human insulin-resistant diabetes.We also investigate the possible contribution of single nucleotide polymorphisms (SNPs) in NEU3 to the development of type 2 diabetes. We surveyed SNPs in the NEU3 gene in 298 Japanese subjects with type 2 diabetes mellitus and two control Japanese populations : one consisting of 148 elderly subjects who met stringent criteria for being non-diabetic including age above 60 years and no evidence of diabetes (HbA1c<5.6%), and another 308 subjects with normal glucose tolerance (NGT). We identified eight SNPs with and five SNPs without amino acid substitutions in their coding regions. The allele frequency of one of SNPs was significantly higher in type 2 diabetic patients than in both elderly normal and NGT subjects, whereas the allele frequency of other SNPs was essentially identical in these three groups. Furthermore, in the NGT subjects, the SNP was associated with a significantly lower insulin sensitivity index on oral glucose tolerance test. These results strongly suggest that, in Japanese, the SNP in the NEU32 gene is associated with the development of type 2 diabetes, via reduced insulin signaling. Less