Dietary Cholesterol and Defects in Cholesterol Synthesis

描述（由申请人提供）：我们提议研究胆固醇代谢和胆固醇缺乏对Smith-Lemli-Opitz综合征（SLOS）的影响。sls是一种由编码7-脱氢胆固醇（7DHC）还原酶的DHCR7基因突变引起的胆固醇合成障碍，7DHC还原酶是胆固醇合成途径中的最后一种酶。受影响的个体表现出多种畸形和智力迟钝。sls的特征被认为主要与胆固醇缺乏和7DHC积累有关。然而，临床表型尚未很好地表征，生化发病机制尚不完全清楚，并且尚无针对这种破坏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来更好地定义sls的表型。我们假设，受损的胆固醇稳态导致可测量的行为和神经认知缺陷，受损的脑髓鞘和胆固醇转换，以及视网膜功能障碍。为了验证这一假设，我们将使用最先进的方法与临床观察、测试和成像并行评估胆固醇稳态。这项自然历史子研究将有助于创建一个全面的sls自然历史注册表，并为临床试验的终点发展做出贡献。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患者中的疗效。我们假设通过改善脑胆固醇合成和增加全身胆固醇池大小，sls患者对辛伐他汀治疗反应良好。为了验证这一假设，我们将用辛伐他汀治疗伴有胆固醇的sls患者2年。与仅接受胆固醇补充的患者相比，治疗效果将主要通过认知和行为（临床）的变化来判断，但也通过替代生化和其他措施（即固醇和氧甾醇、ERG和脑MRI）来判断。本干预研究将检验sls临床治疗试验的可行性和有希望的干预效果的可能性，并为未来的多中心临床试验提供基础。在这个项目中，我们计划将体外研究从实验室转移到床边。我们的第三个目标是阐明sls的发病机制，探讨DCHR7缺乏对细胞功能的影响，并评估体外治疗潜力化合物的细胞益处。我们假设DCHR7缺乏导致代谢偏离胆固醇合成，改变质膜小泡的结构、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。后一项研究将在体外使用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。总之，提出的体内和体外研究应该能阐明SLOS的发病机制，并提供迄今为止研究人员尚未了解的治疗方法。公共卫生相关性：这个研究项目代表了一种尝试，即尽可能多地了解一种叫做Smith-Lemli- Opitz综合征（SLOS）的疾病，以便开发治疗方法。sls是一种胆固醇生成缺陷；受影响的患者有智力迟钝和先天缺陷。与大多数胆固醇过高的胆固醇疾病不同，SLOS的特点是胆固醇缺乏。对这种罕见疾病的研究应该能让我们对胆固醇代谢有更全面的了解，这将有助于对抗更常见的胆固醇相关问题。

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. PUBLIC HEALTH RELEVANCE: This research project represents an attempt to learn as much as we can about a condition called Smith-Lemli- Opitz syndrome (SLOS) in order to develop treatment. SLOS is a defect in cholesterol production; affected patients have mental retardation and birth defects. Unlike most cholesterol diseases which have excess cholesterol, SLOS is characterized by cholesterol deficiency. Studying this rare disease should yield insights into cholesterol metabolism in general, which should prove useful in fighting more common cholesterol related problems.