ALDH1a1 Inhibition As A Therapeutic Target In Visceral Adiposity and Type 2 Diabetes

肥胖是2型糖尿病（T2D）和糖尿病并发症的一个已知驱动因素。白色脂肪组织（WAT）储存能量，而棕色脂肪组织（BAT）通过解偶联蛋白1 （UCP1）和更大的产热程序的作用，以热量的形式释放能量。现在已知BAT在成人中存在并可改变，包括在WAT中诱导BAT样特征（“褐变”）的前景。维甲酸脱氢酶1 （ALDH1a1）功能的丧失可有效诱导UCP1，导致WAT褐变，并防止饮食诱导的肥胖和糖尿病，这是我们和随后的其他人在多个体内模型中所证明的。与许多bat激活靶点不同，ALDH1a1抑制降低了皮下和内脏脂肪组织（VAT），尽管其在内脏脂肪中的高表达确实对这种特殊的致病库产生了明显的影响。与肥胖无关，ALDH1a1缺乏也会降低肝脏糖异生和脂肪变性，这是常见的T2D异常。ALDH1a1将底物视黄醛（Rald）转化为视黄酸（RA）。在体外，抑制ALDH1a1或直接刺激ald均可调节关键产热和糖异生介质的表达。数据支持ALDLH1a1水平与人类肥胖之间的关系。因此，正如我们跨学科的多PI团队所做的那样，将ALDH1a1作为降低肥胖和改善T2D的新治疗靶点存在很强的理论基础，从而为该应用提供了强有力的初步数据。Aim 1旨在优化、进一步开发和测试已经确定的先导小分子ALDH1a1抑制剂和Rald模拟物。最初的重点将是在我们的主要化学文库筛选中发现的四个ALDH1a1支架候选先导物（65万个化合物/验证ALDH1a1活性测定/纳摩尔IC50），使用迭代化学分析和结构修饰结合体外和体内测试。由于ALDH1a1抑制的代谢益处涉及Rald水平的增加，本文探索的一种新的正交治疗策略涉及合成Rald模拟物；铅类似物已经被设计、制造并诱导UCP1的表达。氢/氘交换（HDX）和ALDH1a1共晶学也将被用来对ALDH1a1调节剂的结构-活性关系产生更多的见解。Aim 2与Aim 1化合物进展紧密结合，将通过改变产热、能量平衡、糖异生和脂肪变性来测试ALDH1a1先导调节剂对糖尿病的体外和体内功能作用。综上所述，ALDH1a1调节与这种寻求“新靶点和治疗前先导的早期药理验证”的NIDDK PAR非常匹配：一种新的途径，具有令人信服的、经过验证的先前数据，对关键的、未解决的致病性糖尿病机制建立了临床相关的、独特的作用；一个跨学科的协作团队，为拟议的工作提供必要的背景和工具；迄今为止取得了广泛进展，包括支持ALDH1a1抑制的先导化合物作为治疗T2D的潜在治疗靶点。

Obesity is a known driver of type 2 diabetes (T2D) and diabetic complications. While white adipose tissue (WAT) stores energy, brown adipose tissue (BAT), through the action of uncoupling protein 1 (UCP1) and a larger thermogenic program, releases energy as heat. BAT is now known to be present and modifiable in adult humans, including the prospect of inducing BAT-like characteristics in WAT (‘browning'). Loss of retinaldehyde dehydrogenase 1 (ALDH1a1) function potently induces UCP1, causing browning of WAT and protecting against diet-induced obesity and diabetes, as first we, and subsequently others, have shown in multiple in vivo models. Unlike many BAT-activating targets, ALDH1a1 inhibition decreases both subcutaneous and visceral adipose tissue (VAT), although its higher expression in visceral fat does foster pronounced effects in this particularly pathogenic depot. Independent of adiposity, ALDH1a1 deficiency also decreases hepatic gluconeogenesis and steatosis, common T2D abnormalities. ALDH1a1 converts the substrate retinaldehyde (Rald) to retinoic acid (RA). In vitro, either ALDH1a1 inhibition or direct Rald stimulation modulates expression of key thermogenic and gluconeogenic mediators. Data supports a relationship between ALDLH1a1 levels and adiposity in humans. Thus, a strong rationale exists for pursuing ALDH1a1 as a novel therapeutic target for decreasing adiposity and improving T2D, as our interdisciplinary, multiple PI team has undertaken, resulting in the strong preliminary data underlying this application. Aim 1 seeks to optimize, further develop, and test already identified lead small molecule ALDH1a1 inhibitors and Rald mimetics. Initial focus will be on four ALDH1a1 scaffold lead candidates found in our primary chemical library screen (650,000 compounds/validated ALDH1a1 activity assay/nanomolar IC50) using iterative chemical analysis and structural modifications coupled to in vitro and in vivo testing. Since the metabolic benefits of ALDH1a1 inhibition involve increased Rald levels, a novel, orthogonal therapeutic strategy explored here involves synthetic Rald mimetics; lead analogs are already designed, made and induce UCP1 expression. Hydrogen/deuterium exchange (HDX) and ALDH1a1 co-crystallography will also be leveraged to generate additional insights into ALDH1a1 modulator structure-activity relationships. Aim 2, tightly integrated with Aim 1 compound progression, will test the functional in vitro and in vivo effects of lead ALDH1a1 modulators on diabetes through changes in thermogenesis, energy balance, gluconeogenesis and steatosis. Taken together, ALDH1a1 modulation is well matched to this NIDDK PAR seeking “early-stage pharmacological validation of novel targets and pre- therapeutic leads”: a new pathway with compelling, validated prior data establishing clinically-relevant, unique effects on critical, unaddressed pathogenic diabetic mechanisms; an interdisciplinary, collaborative team with the requisite background and tools for the proposed work; extensive progress to date, including lead compounds that support ALDH1a1 inhibition as a potential therapeutic target for treating T2D.