Dietary Cholesterol and Defects in Cholesterol Synthesis

描述(申请人提供)：我们建议对Smith-Lemli-Opitz综合征(SLOS)的胆固醇代谢和胆固醇缺乏的影响进行研究。SLOS是一种由编码7-脱氢胆固醇(7DHC)还原酶基因突变引起的胆固醇合成障碍，7-脱氢胆固醇(7DHC)还原酶是胆固醇合成途径中的最终酶。受影响的个体表现出多种畸形和智力发育迟缓。SLOS的特征被认为主要与胆固醇缺乏和7DHC积聚有关。然而，临床表型尚不清楚，生化发病机制也不完全清楚，目前还没有针对这种毁灭性疾病的有效治疗方法。因此，我们的第一个目标是使用自然历史研究设计更好地确定SLOS的表型。我们假设，胆固醇稳态受损会导致可测量的行为和神经认知缺陷，脑髓鞘和胆固醇周转受损，以及视网膜功能障碍。为了验证这一假设，我们将在临床观察、测试和成像的同时，使用最先进的方法来评估胆固醇稳态。这项自然历史分研究将有助于创建一个全面的SLOS自然历史登记系统，并有助于开发临床试验的终点。我们的第二个目标是测试辛伐他汀作为补充治疗策略在补充胆固醇的患者中的有效性。我们假设SLOS患者将通过改善脑胆固醇合成和增加全身胆固醇池大小而对辛伐他汀治疗产生积极反应。为了验证这一假设，我们将用辛伐他汀治疗补充胆固醇的SLOS患者2年。与仅接受胆固醇补充的患者相比，治疗效果将主要根据认知和行为(临床)的变化以及替代生化和其他指标(即类固醇和氧类固醇、ERG和脑核磁共振)来判断。这项干预研究将检验SLOS临床治疗试验的可行性和有希望的干预措施的有效性，并为未来的多中心临床试验提供基础。在这个项目中，我们计划继续将体外研究从长凳转移到床边。我们的第三个目标是阐明SLOS的发病机制，探讨DCHR7缺乏对细胞功能的影响，并在体外评估具有治疗潜力的化合物的细胞效益。我们推测，DCHR7缺乏导致代谢偏离胆固醇合成，改变质膜小窝的结构、组成和信号功能，损害ER特异性蛋白折叠活性，并导致细胞氧化应激和细胞凋亡。我们进一步假设他汀类药物、胆汁酸、抗氧化剂和分子伴侣选择性地恢复SLOS细胞的代谢和功能。后一项研究将使用SLOS和对照皮肤成纤维细胞、SLOS小鼠脑源性细胞和SLOS人脑组织进行体外研究。总之，拟议的体内和体外研究应该有助于阐明SLOS的发病机制，并为迄今为止研究人员未能找到的治疗方法提供见解。

DESCRIPTION (provided by applicant): We propose a study of cholesterol metabolism and the effects of cholesterol deficiency in Smith-Lemli-Opitz Syndrome (SLOS). SLOS is a disorder of cholesterol synthesis caused by mutations in the DHCR7 gene encoding 7-dehydrocholesterol (7DHC) reductase, the final enzyme in the cholesterol synthetic pathway. Affected individuals exhibit multiple malformations and mental retardation. The features of SLOS are thought to be primarily related to cholesterol deficiency and accumulation of 7DHC. However, the clinical phenotype is not well characterized, the biochemical pathogenesis is incompletely understood, and there is no proven therapy for this devastating condition. Thus our first objective is to better define the phenotype of SLOS using a natural history study design. We hypothesize that impaired cholesterol homeostasis leads to measurable behavioral and neurocognitive deficits, impaired brain myelination and cholesterol turnover, and retinal dysfunction. To test this hypothesis we will assess cholesterol homeostasis using state-of-the-art methods in parallel with clinical observation, testing, and imaging. This natural history sub-study will contribute to creating a comprehensive SLOS natural history registry and to the development of end-points for clinical trials. Our second objective is to test the efficacy of simvastatin as a complementary therapeutic strategy in patients supplemented with cholesterol. We hypothesize that SLOS patients will respond favorably to simvastatin treatment by improving brain cholesterol synthesis and increasing whole body cholesterol pool size. To test this hypothesis, we will treat SLOS patients supplemented with cholesterol for 2 years with simvastatin. Treatment efficacy will be judged primarily on changes in cognition and behavior (clinical) but also on surrogate biochemical and other measures (i.e. sterols and oxysterols, ERG, and brain MRI), in comparison with patients receiving only cholesterol supplementation. This intervention study will test the feasibility of clinical treatment trials in SLOS and the likelihood of efficacy of a promising intervention, as well as provide a foundation for future multicenter clinical trials. In this project, we plan to proceed with translation of in vitro studies from bench to bedside. Our third objective is to elucidate SLOS pathogenesis, probe the consequences of DCHR7 deficiency on cell functions and evaluate the cellular benefit of compounds with therapeutic potential in vitro. We hypothesize that DCHR7 deficiency causes metabolic diversion away from cholesterol synthesis, alters the structure, composition and signaling function of plasma membrane caveolae, impairs ER-specific protein folding activity, and causes cellular oxidative stress and apoptosis. We further hypothesize that statins, bile acids, antioxidants and molecular chaperones selectively restore SLOS cell metabolism and function. These latter studies will be conducted in vitro using SLOS and control skin fibroblasts, SLOS mouse brain-derived cells, and SLOS human brain tissues. Together, the in vivo and in vitro studies proposed should shed light on the pathogenesis of SLOS, and offer insights into treatment that to date have eluded investigators.