ROLE OF CAMKII IN HEPATIC GLUCONEOGENESIS

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 糖异生(GNG)在禁食时被强烈刺激，在糖尿病时被异常激活。目前已有多种转录因子和共激活因子参与调控这一过程，但其内在机制尚未完全阐明。我们最近发现，在瘦素缺乏(ob/ob)小鼠的肝脏中，一种钙反应激酶钙/钙调素依赖的蛋白激酶II(CaMKII)被激活，这是一种严重的胰岛素抵抗和糖尿病的模型。用特定的CaMKII抑制剂治疗ob/ob小鼠可降低肝脏CaMKII活性，降低空腹血糖，并减少糖异生基因G6Pase和PEPCK的表达。接下来，我们研究了表达CaMKIIg的WT和Camk2g-/-小鼠的原代肝细胞中的GNG。我们证明了CaMKII在空腹糖异生的调节中起着重要作用。我们发现，CaMKIIg缺陷的肝细胞在胰升糖素模拟物和cAMP激活剂Forsklin诱导的G6Pase和PEPCK的表达显著降低，以及转录诱导GNG基因的核FoxO1水平降低。此外，转导含有结构性活性CaMKII的腺病毒的原代肝细胞与对照组相比，G6Pase和PEPCK mRNA的表达水平增加。为了支持CaMKIIg在体内禁食GNG中的作用，我们发现与WT小鼠相比，禁食Camk2g-/-小鼠的血糖水平更低；丙酮酸到葡萄糖的转化率更低；肝脏GNG基因的诱导迟钝；肝细胞核中FoxO1的水平更低。这些数据表明，内质网应激诱导的CaMKIIg在肥胖和禁食期间肝脏中的激活有助于增加肝脏葡萄糖的产生和高血糖。这一概念提出了以肝脏CaMKIIg为治疗靶点对胰岛素抵抗受试者的血糖稳态具有特殊益处的可能性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Gluconeogenesis (GNG) is strongly stimulated during fasting and is aberrantly activated in diabetes mellitus. Several transcription factors and coactivators have been shown to regulate this process, however, the underlying mechanisms have not been fully elucidated. We recently found that a calcium-responsive kinase calcium/calmodulin-dependent protein kinase II (CaMKII) is activated in the liver of leptin-deficient (ob/ob) mice, a model of severe insulin resistance and diabetes. Treatment of ob/ob mice with a specific CaMKII inhibitor decreased hepatic CaMKII activity, lowered fasting blood glucose, and decreased the expression of the gluconeogenic genes, G6Pase and PEPCK. We next explored GNG in primary hepatocytes, which express CaMKIIg, from WT vs. Camk2g-/- mice. We demonstrated that CaMKII plays an essential role in the regulation of fasting gluconeogenesis. We found that the CaMKIIg-deficient hepatocytes have a marked decrease in the expression of G6Pase and PEPCK induced by forskolin, a glucagon mimetic and cAMP activator, and lower levels of nuclear FoxO1, which transcriptionally induces GNG genes. Moreover, primary hepatocytes transduced with adenovirus containing constitutively active CaMKII have increased expression levels of G6Pase and PEPCK mRNA compared with controls. In support of a role for CaMKIIg in fasting GNG in vivo, we found that fasted Camk2g-/- mice had lower blood glucose levels; lower conversion of pyruvate to glucose; blunted induction of hepatic GNG genes; and lower levels of FoxO1 in hepatic nuclei compared with WT mice. These data suggest that ER stress-induced activation of CaMKIIg in liver during obesity and fasting contributes to increased hepatic glucose production and hyperglycemia. This concept raises the possibility that therapeutic targeting of hepatic CaMKIIg may have particular benefit in glucose homeostasis in insulin-resistant subjects.