Elucidating the Role of Very-long-chain Polyunsaturated Fatty Acids in Retinal Health and Disease

极长链多不饱和脂肪酸（VLC-PUFA）是一种非膳食脂质， 在视网膜和人体的其他一些组织中。这些不寻常的C26-C38 n-3和n-6脂质是 由长链多不饱和脂肪酸（LC-PUFA）膳食前体通过以下作用合成： DLVL 4脂肪酸延伸酶。认为LC-PUFA和VLC-PUFA有助于增强膜流动性 对于维持感光体外节的高度弯曲的膜盘是必要的 并促进光感受器突触传递。ESTVL 4中的常染色体显性突变导致一种形式 Stargardt黄斑营养不良（STGD 3）与干性年龄相关性黄斑变性有许多共同特征， (AMD)我们和其他人已经表明，视杆细胞和视锥细胞Elovl 4的条件性敲除导致了细胞内的 视网膜VLC-PUFA和最终的视网膜功能和结构异常的小鼠模型。 尽管HPVL 4变异与AMD风险无关，但饮食的保护作用高， 针对STGD 3和AMD的n-3 VLC-PUFA的脂质前体中的作用导致我们检查饮食对 健康和疾病中视网膜VLC-PUFA水平和n-3/n-6比率。我们已经报道了饮食消费 VLC-PUFA前体强烈影响正常人视网膜中n-3/n-6比值和VLC-PUFA含量， VLC-PUFA谱在AMD供体中明显异常，甚至在黄斑之外。这些发现 表明VLC-PUFA代谢异常与黄斑变性密切相关， 通过补充增加VLC-PUFA水平的策略可以帮助减缓退化过程。 令人惊讶的是，明显的治疗干预绕过VLC-PUFA的局部视网膜合成， 在活生物体中从未尝试过外源施用预先形成的VLC-PUFA，因为，直到 最近，即使在小鼠中，也从未有足够的这些脂质供应来进行这些实验。 虽然VLC-PUFAs的合成被认为是非常困难的，但我们发起了与脂质体的合作。 犹他州大学的化学专家开发了改进的方案， 扩大规模以生产足量的纯n-3和n-6 VLC-PUFA（未标记、氟化或氘代） 用于动物研究甚至最终的人体试验。我们已经生成了令人兴奋的初始数据，表明 口服给药的合成VLC-PUFA（32：6 n-3）在急性炎症后选择性靶向视网膜和RPE， 并在小鼠和野生型小鼠和VLC-PUFA小鼠模型中慢性灌胃喂养显示功能障碍 在他们的视网膜电图和视觉性能的功能改善。凭借我们独特的渠道， 的n-3和n-6 VLC-PUFA阵列，我们渴望继续测试我们的基本假设，即VLC- PUFAs是维持健康和疾病中视网膜感光功能的关键化合物 states.我们将通过更充分地探索外源性抗氧化剂保护作用的机制来实现这一点。 新型动物模型、细胞培养物和模型膜中视网膜和RPE中的VLC-PUFA。

Very long-chain polyunsaturated fatty acids (VLC-PUFAs) are non-dietary lipids that are uniquely found in the retina and just a few other tissues in the human body. These unusual C26-C38 n-3 and n-6 lipids are synthesized from long-chain polyunsaturated fatty acid (LC-PUFA) dietary precursors through the action of the ELOVL4 fatty acid elongase. Enhanced membrane fluidity contributed by LC-PUFAs and VLC-PUFAs is thought to be essential for the maintenance of the highly curved membrane disks of the photoreceptor outer segments and to facilitate photoreceptor synaptic transmission. Autosomal dominant mutations in ELOVL4 lead to a form of Stargardt macular dystrophy (STGD3) that shares many features with dry age-related macular degeneration (AMD), and we and others have shown that conditional knockouts of rod and cone Elovl4 lead to depletion of retinal VLC-PUFAs and eventual retinal functional and structural abnormalities in mouse models. Although ELOVL4 variants have not been associated with AMD risk, the protective effects of diets high in lipid precursors of n-3 VLC-PUFAs against STGD3 and AMD led to us to examine the influence of diet on retinal VLC-PUFA levels and n-3/n-6 ratios in health and disease. We have reported that dietary consumption of VLC-PUFA precursors strongly influences n-3/n-6 ratios and VLC-PUFA content in normal human retinas and that VLC-PUFA profiles are distinctly abnormal in AMD donors even outside of the macula. These findings suggest that abnormalities of VLC-PUFA metabolism are intimately associated with macular degeneration and that strategies to increase VLC-PUFA levels by supplementation could help slow the degeneration process. Surprisingly, the obvious therapeutic intervention of bypassing local retinal synthesis of VLC-PUFAs by administering preformed VLC-PUFAs exogenously had never been tried in living organisms because, until recently, there have never been adequate supplies of these lipids to perform these experiments, even in mice. Although synthesis of VLC-PUFAs has been reputed to be very difficult, we initiated a collaboration with lipid chemistry specialists at the University of Utah who developed improved schemes that allow for straightforward scale-up to produce sufficient quantities of pure n-3 and n-6 VLC-PUFAs (unlabeled, fluorinated, or deuterated) for animal studies and even eventual human trials. We have generated exciting initial data that show that an orally administered synthetic VLC-PUFA (32:6 n-3) is selectively targeted to the retina and the RPE after acute and chronic gavage feeding in mice and that wild-type mice and a mouse model of VLC-PUFA dysfunction show functional improvements in their ERGs and visual performance. With our unique access to sufficient quantities of an array of n-3 and n-6 VLC-PUFAs, we are eager to continue to test our fundamental hypothesis that VLC- PUFAs are key compounds for the maintenance of photoreceptor function in the retina in both health and disease states. We will do this by more fully exploring the mechanisms underlying the protective effects of exogenous VLC-PUFAs in the retina and RPE in novel animal models, in cell culture, and in model membranes.