The role of Stearate in the regulation of vascular calcification in chronic kidne

描述（由申请方提供）：心血管疾病（如血管钙化）是CKD受试者死亡的主要原因。然而，目前尚无有效的治疗血管钙化的方法。硬脂酸是哺乳动物细胞中主要的饱和脂肪酸，其来源有两条途径：膳食脂肪吸收和新生脂肪生成。我们的长期目标是确定预防血管钙化的新的药理学策略。我们以前的研究表明，硬脂酸盐来源于从头脂肪生成促进主动脉钙化。硬脂酰辅酶A去饱和酶（SCD）-1和SCD 2都是参与硬脂酸代谢的中心酶。正如我们的初步结果所示，通过添加外源性硬脂酸盐或通过抑制SCD 1和SCD 2增加硬脂酸盐在体外和体内增加血管钙化。最近，我们发现，血清硬脂酸水平显着增加， 患有慢性肾病（CKD）的受试者，由于SCD活性较低。硬脂酸盐的促钙化和促成骨作用与ER中二硬脂酰磷脂酸（18：0-PA）的水平和ATF 4的表达高度相关，ATF 4是骨生成调节中的中心转录因子。这些作用也与CHOP的表达有关，CHOP是一种促进细胞凋亡的转录因子。因此，我们假设，来源于内质网中SCD合成的硬脂酸酯的18：0-PA通过激活体内未折叠蛋白反应的PERK-eIF 2 <$-ATF 4-CHOP途径诱导血管成骨和钙化。我们将设计实验，以解决这一假设，在体内和体外的方法。本提案的两个具体目的是：1）确定体外硬脂酸盐介导血管钙化的分子机制，2）确定体内ATF 4-CHOP通路的激活是否介导了由于SCD 1和SCD 2的VSMC缺乏而导致的硬脂酸盐增加诱导的血管钙化。

DESCRIPTION (provided by applicant): Cardiovascular disease such as vascular calcification is a leading cause of death in subjects with CKD. However, there is no effective therapy for vascular calcification available. Stearate, a major saturated fatty acid in mammalian cells, is derived through two pathways: dietary fat absorption and de novo lipogenesis. Our long-term goal is to identify new pharmacological strategies for the prevention of vascular calcification. Our previous study has revealed that stearate derived from de novo lipogenesis promotes aortic calcification. Both stearoyl-CoA desaturase (SCD)-1 and SCD2 are central enzymes involved in the metabolism of stearic acid. As shown in our preliminary results, increasing stearate by adding exogenous stearate or by inhibiting SCD1 and SCD2 augmented vascular calcification in vitro and in vivo. Recently, we found that levels of serum stearate were significantly increased in subjects with chronic kidney disease (CKD), due to lower SCD activity. The pro-calcific and pro-osteogenic effects of stearate were highly correlated with levels of distearoyl-phosphatidic acid (18:0-PA) in the ER and the expression of ATF4, which is a central transcription factor in the regulation of osteogenesis. These effects were also associated with the expression of CHOP, a transcription factor that promotes apoptosis. We therefore hypothesize that 18:0-PA derived from stearate synthesized by SCD in the endoplasmic reticulum induces vascular osteogenesis and calcification by activating the PERK-eIF2¿-ATF4-CHOP pathway of the unfolded protein response in vivo. We will design experiments to address this hypothesis using in vivo and in vitro approaches. The two specific aims of this proposal are 1) To determine the molecular mechanism underlying stearate-mediated vascular calcification in vitro, and 2) To determine whether the activation of the ATF4-CHOP pathway mediates vascular calcification induced by increased stearate due to VSMC deficiency of SCD1 and SCD2 in vivo.