Regulation of insulin signaling and sensitivity by the xenobiotic metabolizing enzyme NQO1

代谢综合征包括一组心血管危险因素，包括肥胖、高血压、血糖 不耐受和血脂异常，其基本病理与胰岛素抵抗有关。我们已经证明了 异源生物代谢酶NQO1对胰岛素敏感性和对饮食诱导的疾病的保护至关重要。 使用NQO1转基因小鼠提高NQO1表达可保护负生化和 高脂肪饮食的生理效应和增强胰岛素敏感性。NQO1的药理抑制作用 使用基于选择性机制的抑制剂导致小鼠胰岛素敏感性严重受损。NQO1 基因敲除动物是胰岛素不敏感的，导致糖尿病样表型，NQO1基因缺失是 与人类代谢综合征表型有关。我们的数据显示，NQO1是激活 AKT通过启用其胰岛素诱导的与允许AKT丝氨酸的蛋白复合体TORC 2的相互作用来实现 磷酸化和充分利用葡萄糖。胰岛素治疗导致NQO1迅速而显著增加 胰岛素受体的酪氨酸磷酸化和突变分析表明，磷酸化导致主要 NQO1功能的变化。构象依赖抗体和电泳法也表明 NQO1构象的变化是由于改变了吡啶核苷酸氧化还原比或添加了胰岛素。 基于NQO1的细胞功能，我们将测试三种生物学上可信的机制，以支持观察到的 NQO1在胰岛素信号转导和代谢综合征表型保护中的作用。1)NQO1调制 蛋白质支架的胰岛素依赖信号转导。我们将检验这样一个假设，即NQO1的观察到的影响 在胰岛素敏感性上，NQO1的构象变化是由吡啶的变化引起的 核苷酸水平或通过胰岛素受体对NQO1的磷酸化，促进AKT的最佳关联 2)NQO1产生NAD+以获得最佳的SIRT活性。脱乙酰化 Via SIRT在胰岛素信号转导中起关键作用，而NQO1可以迅速产生高水平的NAD+，以实现最佳SIRT 活性；3)关键代谢调节剂的稳定。关键的新陈代谢调节剂Pgc1α受到保护 NQO1降解蛋白酶体。前列腺素C_1α和AMPK均影响线粒体氧化磷酸化和 生物发生和预防代谢综合征。因此，我们将定义NQO1是否影响新陈代谢 Pgc1、α、AMPK水平调节证候。 我们的工作假设是NQO1在胰岛素敏感性和对代谢的保护中起着关键作用 证候表型，但有待回答的关键问题是其背后的机制(S) NQO1的有益效果。

Metabolic syndrome comprises a group of cardiovascular risk factors including obesity, high blood pressure, glucose intolerance and dyslipidemia whose underlying pathology is related to insulin resistance. We have shown that the xenobiotic-metabolizing enzyme NQO1 is critical to insulin sensitivity and protection from diet-induced morbidities. Increasing NQO1 expression using NQO1 transgenic mice protects against the negative biochemical and physiological effects of a high fat diet and confers increased insulin sensitivity. Pharmacological inhibition of NQO1 using selective mechanism-based inhibitors led to a severe impairment in insulin sensitivity in mice. NQO1 knockout animals are insulin-insensitive resulting in a diabetes-like phenotype and a null NQO1 polymorphism is associated with metabolic syndrome phenotypes in humans. Our data shows that NQO1 is required for activation of AKT by enabling its insulin-inducible interaction with the protein complex TORC 2 allowing AKT serine phosphorylation and full glucose utilization. Insulin administration led to a rapid and marked increase in NQO1 tyrosine phosphorylation by the insulin receptor and mutational analysis suggests that phosphorylation leads to major changes in NQO1 functionality. Conformation-dependent antibodies and electrophoresis also indicated marked changes in NQO1 conformation as a result of either altered pyridine nucleotide redox ratios or addition of insulin. Based on the cellular functions of NQO1, we will test 3 biologically plausible mechanisms underlying the observed role of NQO1 in insulin signaling and protection against metabolic syndrome phenotypes. 1) NQO1 modulates insulin-dependent signaling by protein scaffolding. We will test the hypothesis that the observed effects of NQO1 on insulin sensitivity are modulated by a change in NQO1 conformation induced either by alterations in pyridine nucleotide levels or by phosphorylation of NQO1 by the insulin receptor, facilitating optimal association of AKT and Rictor and downstream insulin signaling; 2) NQO1 generates NAD+ for optimal SIRT activity. Deacetylation via SIRTs is critical in insulin signaling and NQO1 can rapidly generate high levels of NAD+ for optimal sirtuin activity; 3) Stabilization of critical metabolic regulators. The key metabolic regulator PGC1α is protected against proteasomal degradation by NQO1. Both PGC1α and AMPK influence mitochondrial oxidative phosphorylation and biogenesis and protect against metabolic syndrome. We will therefore define whether NQO1 influences metabolic syndrome by modulation of PGC1α and AMPK levels. Our working hypothesis is that NQO1 plays a critical role in insulin sensitivity and protection against metabolic syndrome phenotypes but the critical question that remains to be answered is the mechanism(s) underlying the beneficial effects of NQO1.