Ceramide and acute phase protein elevation during aging

描述(申请人提供)：我们的实验室长期以来一直对导致慢性低度炎症状态的机制感兴趣，这是衰老过程和许多与衰老相关的疾病的内在组成部分。在过去，我们报道了肝脏对白介素12(IL-12)的反应，白介素12(IL-12)是全身炎症的主要介质，随着年龄的增长，肝脏对白介素12(IL-12)的反应会增强，导致IGFBP1的过度产生，IGFBP1是肝脏分泌的一种蛋白质，与胰岛素样生长因子1(IGF1)结合，并中和其生物活性。肝脏IL-12高反应性是由进化保守的细胞应激反应通路的内在激活引起的，该通路涉及中性鞘磷脂酶及其产物神经酰胺。在此，我们假设IL-12的高反应性损害了肝脏中的胰岛素信号通路。首先，我们将研究衰老相关的IL-12高反应性如何影响胰岛素途径，并将研究PI3K、Akt-1和Foxo1(针对胰岛素)和神经酰胺、IRAK-1和JNK(针对IL-12)两级联中关键分子之间的相互作用。研究将在体外分离的肝细胞和体内的动物身上进行。将使用年轻、老年和老年限制卡路里的大鼠。我们将研究这两条途径对IGFBP1基因转录的调节作用。这些分子研究将得到体内胰岛素和IGFBP1依赖功能的测试的补充，其中包括IGF1生物活性、肌肉功能和葡萄糖调节的测试。在整个实验过程中，将通过腺病毒介导的基因转移的过度表达和沉默方法来检验因果关系。这些研究可能有助于阐明老年人肌肉萎缩、虚弱和葡萄糖调节失调的细胞和分子途径。它们还可能揭示一种整合炎症和代谢信号通路的新机制，以及衰老如何影响这些相互作用。)

DESCRIPTION (provided by applicant): Our lab has a long standing interest in the mechanisms leading to the state of chronic, low-grade inflammation, which is an intrinsic component of the aging process and many aging-associated diseases. In the past we reported that the hepatic response to Interleukin 12 (IL-12), a major mediator of systemic inflammation, is augmented during aging leading to excessive production of IGFBP1, a protein that is secreted by the liver, binds to the Insulin-like Growth Factor 1 (IGF1), and neutralizes its bioactivity. Hepatic IL-12 hyperresponsiveness is caused by the intrinsic activation of an evolutionary conserved cellular stress response pathway involving neutral sphingomyelinase and its product, ceramide. Here we hypothesize that this IL-12 hyperresponsiveness impairs the insulin signaling pathway in liver. First, we will investigate how aging-associated IL-12 hyperresponsiveness affects the insulin pathway and will study the interactions between key molecules in the two cascades PI3K, Akt-1, and Foxo1 (for insulin), and ceramide, IRAK-1 and JNK (for IL-12). Studies will be done in isolated hepatocytes in vitro and in animals in vivo. Young, aged and aged calorie restricted rats will be used. The regulation of IGFBP1 mRNA transcription by the two pathways will be investigated. These molecular studies will be complemented by assays of insulin- and IGFBP1-dependent functions in vivo, which include tests of IGF1 bioactivity, muscle functions and glucose regulation. Throughout the experiments cause and effect relations will be tested by overexpression and silencing approach using adenovirus-mediated gene transfer. These studies may help to elucidate the cellular and molecular pathways responsible for muscle waste, frailty, and glucose dysregulation in the elderly. They may also reveal a novel mechanism for integration of inflammatory and metabolic signaling pathways and how aging affects these interactions. )