Ghrelin Agonists Multiple Beneficial Effects on Parkinson's Non-Motor Symptoms

 说明： 帕金森病是一种复杂的运动和非运动症状，伴有进行性多巴胺能(DA)和多系统的非DA神经变性。对非运动性症状的治疗很少，这些症状包括胃排空延迟，更明显的是便秘，体重减轻和水摄入量减少。其潜在的机制在很大程度上是未知的，涉及中枢和外周的改变。在帕金森病患者和帕金森病动物模型的脑中发现了炎症，这可能促进DA神经元的退化，与运动症状的严重程度相关，并可能有助于非运动症状的发展。大鼠前脑内侧束微量注射神经毒素6-羟基多巴胺(6-OHDA)所致帕金森病动物模型，DA能神经元部分丧失。除了运动障碍，大鼠还有便秘，和帕金森病患者一样，减少了水的摄入量和体重。我们之前也报道了在遗传模型(Thy1-asyn小鼠)中，便秘样疾病和较少的体重增加。Ghrelin是一种胃肠激素，它通过外周和中枢机制对肠道产生促氧和促动力作用。体重减轻的PD患者基础循环中的Ghrelin水平较低，并且没有表现出餐后晚期升高，这表明Ghrelin的释放和/或合成受到抑制。我们的初步数据显示，全身性给予Ghrelin激动剂anamorelin增加了Thy1-aSyn小鼠的体重和食物摄入量。然而，全身性Ghrelin不能刺激结肠运动，而Ghrelin激动剂能通过血脑屏障(BBB)。我们发现，HM01是一种跨越血脑屏障的Ghrelin激动剂，可以增加6-OHDA大鼠的排便。更重要的是，Ghrelin对DA神经元具有抗炎和神经保护作用。Ghrelin激动剂具有口服活性和长效作用，因此比Ghrelin有优势。该假说认为，Ghrelin激动剂通过肠道促动力、促食欲素、生脂肪和合成代谢等涉及不同机制的作用，对帕金森病症状有多种有益的影响。我们将在两个显示不同帕金森病病理特征的动物模型中验证Ghrelin激动剂的作用，因为没有一个动物模型概括了人类帕金森病的进行性和复杂性。将比较血脑屏障交叉(HM01)和非血脑屏障交叉(Anamorelin)激动剂的效果，并对目标进行评估。(1)观察Ghrelin激动剂对6-OHDA大鼠和Thy1-asyn小鼠便秘和结肠信号改变的影响。口服HM01或Anamorelin后，将监测粪便产量和水分含量，并使用非侵入性微型压力传感器测量结肠运动。远端回肠和结肠粘膜的通透性将在Ussing小室中进行评估。(2)评估Ghrelin激动剂是否能减少体重和脂肪质量的损失，并改善摄食和水分摄入。HM01和Anamorelin对Thy1-asyn和野生型小鼠的食物和水摄入量的影响，体重将使用最先进的自动新陈代谢筛查系统与能量摄入和消耗同时进行监测，并通过自动进食事件监测系统监测进食模式。Ghrelin激动剂对Thy1-aSyn小鼠和6-OHDA大鼠身体成分的影响将在啮齿动物磁共振设备上进行测量，以及对6-OHDA大鼠摄水量的影响。(3)观察Ghrelin激动剂对L多巴治疗的6-羟基多巴胺大鼠便秘、体重减轻、运动功能障碍及L多巴诱导的胃排空障碍等帕金森病症状的影响。用Ghrelin激动剂和L-多巴治疗后，检测结肠和脑内的相关信号。本研究将有助于进一步验证Ghrelin激动剂对动物模型黑质纹状体系统的神经炎症和神经保护作用。治疗非运动症状是帕金森病研究的重点之一。该项目将为Ghrelin激动剂缓解便秘、肥胖和体重减轻以及包括在压力下更脆弱的退伍军人在内的帕金森病患者的运动障碍提供临床前证据。

 DESCRIPTION: PD has a complex of motor and non-motor symptoms with progressive dopaminergic (DA) and non-DA neurodegeneration in multisystem. There is paucity in treatment for non-motor symptoms that include delayed gastric emptying and more prominently constipation, weight loss and reduced water intake. The underlying mechanisms are largely unknown and involve both central and peripheral alterations. Inflammation was found in the brains of PD patients, as well as animal models of PD, which may promote degeneration of DA neurons, is correlated to motor symptom severity and might contribute to the development of non-motor symptoms. An animal model for PD induced by a neurotoxin, 6-hydroxydopamine (6-OHDA) microinjected unilaterally in the medial forebrain bundle of rats, has partial loss of DA neurons. Beside motor disorders, the rats have constipation, and reduced water intake and body weight as in PD patients. We also previously reported constipation-like disorders and less weight gain in a genetic model (Thy1-asyn mice). Ghrelin is a gut hormone and it has orexigenic and prokinetic effect on the gut through peripheral and central mechanisms. PD patients with body weight loss have lower basal circulating levels of ghrelin, and do not show the late phase postprandial rise suggesting dampened ghrelin release and/or synthesis. Our preliminary data showed that systemic administration of a ghrelin agonist, anamorelin increased body weight and food intake in Thy1-aSyn mice. However, systemic ghrelin did not stimulate the colonic motility, while ghrelin agonist crossing the blood- brain barrier (BBB) did. We showed that a BBB-crossing ghrelin agonist, HM01 increased defecation in 6- OHDA rats. More importantly, ghrelin has anti-inflammatory and neuroprotective effect on DA neurons. Ghrelin agonists have advantages over ghrelin as they are orally active and long acting. The hypothesis is that ghrelin agonists have multiple beneficial effects on PD symptoms via gut prokinetic, orexigenic, dipsogenic and anabolic actions that involve distinct mechanisms. We will validate the ghrelin agonist effects in two animal models which display different PD pathological features, because no animal model recapitulates the progressive nature and complexity of human PD. The effects of BBB crossing (HM01) and non-BBB crossing (anamorelin) agonists will be compared and the targets will be assessed. (1) To assess ghrelin agonists' effect on constipation and altered colonic signals in 6-OHDA rats and Thy1-asyn mice. After oral administration of HM01 or anamorelin, fecal output and water content will be monitored, colonic motility will be measured using a non-invasive miniaturized pressure transducer. The permeability of the distal ileal and colonic mucosa will be assessed in Ussing's chambers. (2) To assess whether ghrelin agonists reduce loss of body weight and fat mass and improve feeding and water intake. HM01 and anamorelin effect in Thy1-asyn and wide type mice on food and water intake, body weight will be monitored simultaneously with energy intake and expenditure using a state-of-art automated metabolism screening system, and meal pattern by an automated feeding episode monitoring system. Ghrelin agonists' effect on body composition of Thy1-aSyn mice and 6-OHDA rats will be measured in rodent MRI equipment, as well as on water intake in 6-OHDA rats. (3) To assess ghrelin agonist effect on PD symptoms in 6-OHDA rats under L-dopa treatment, such as constipation, body weight loss, motor dysfunctions and L-dopa-induced delayed gastric emptying. The related signals in the colon and brain will be measured after ghrelin agonist and L-dopa treatment. This study will help to further validate ghrelin agonists' effect on neuroinflammation and neuroprotection in the nigrostriatal system in the animal models. Treating non- motor symptoms is one of the priorities in PD research. This project will provide preclinical evidence for novel beneficial effects of ghrelin agonists to alleviate constipation, adipsia and weight loss, as well as motor deficits in PD including Veterans who are more vulnerable under stress.