Peptide therapy for age-associated gut dysmotility

项目总结/摘要 衰老与液体和固体的胃排空率以及胃排空频率的降低有关。 蠕动的收缩。在人类中，肠道运动障碍会加重感染，导致营养吸收不良， 并表现出使人衰弱的症状，如胃轻瘫、假性肠梗阻、腹泻， 便秘、先天性巨结肠和大便失禁。大约20%的老年人患有慢性 严重影响健康和生活质量的便秘。在美国，胃肠道疾病的费用为135.9美元 每年十亿。肠道运动是由平滑肌细胞、间质细胞、 Cajal（ICCs）、中枢神经系统神经元和肠神经系统中的运动神经元（ENS，“the 肠的大脑”）。ENS运动神经元释放兴奋性神经递质，如乙酰胆碱（ACh） P物质（SP）。5-羟色胺或5-羟色胺（5-HT）4受体（5-HT 4 R）和多巴胺（DA）2 受体（D2 R）在肠神经节内的神经突中广泛表达。DA抑制ACh的释放 内源性胆碱能运动神经元通过激活连接前的D2 Rs。5-HT通过以下途径增强肠道运动 通过激活5-HT 4 R引起ACh释放。CgA被蛋白水解加工成几种生物活性物质， 活性肽包括catestatin（CST：hCgA 352 -372）。最近，我们发现肠道运动 在CST-KO小鼠中受损，在补充CST后恢复。此外，CST-KO 小鼠表现出以下表型：（i）胃增大（胃轻瘫），（ii）胃排空延迟，（iii） CST可作为ACh受体（AChR）的短期拮抗剂， 抑制儿茶酚胺分泌和长期激动剂，刺激ACh分泌。因此，CST 可能通过增加肌间神经丛ACh的分泌， 由于我们发现老年WT小鼠血浆CST降低，老年WT小鼠肠道CST降低， 对于老年小鼠，我们推断CST将在减弱肠动力障碍中发挥作用。我们制定了四个 可能介导CST调节肠道运动的独立协同假说：（i）激活 AChR，（ii）促进肠嗜铬细胞产生5-HT，（iii）抑制ENS产生DA， 和（iv）通过增加耐受性维持肌内ICC（ICC-IM）群体。证实或反驳 根据上述假设，我们提出了两个具体目标的实验：目标I：测试假设， CST通过促进AChR信号传导改善衰老小鼠的肠道运动和胃排空， 增加5-HT的产生，抑制DA的释放，并防止ICC群体的损失。目标二： 翻译CST启发的疗法，以对抗年龄相关的肠道动力障碍。影响：The 本提案的首要重点是生成关于科技委及其模拟物影响的重要信息 缓解与年龄相关的肠道动力障碍。我们的研究将是第一个直接联系CST和它的模拟物 肠动力，并可能建立CST途径作为治疗肠道运动的目标。如果结果 是积极的，那么新的治疗途径可能会出现，使风险值得。

PROJECT SUMMARY/ABSTRACT Aging is associated with reductions in the rates of gastric emptying for liquids, and solids, as well as the frequency of peristaltic contractions. In humans, dysmotility of the gut potentiates infections, causes nutrient malabsorption, and manifests with debilitating symptoms, such as gastroparesis, intestinal pseudo-obstruction, diarrhea, constipation, Hirschprung’s disease, and fecal incontinence. About 20% of older adults experience chronic constipation that profoundly affect health and quality of life. In the USA, gastrointestinal diseases cost $135.9 billion annually. Gut motility is regulated by coordinated activities from smooth muscle cells, interstitial cells of Cajal (ICCs), central nervous system neurons and motor neurons in the enteric nervous system (ENS, “the brain of the gut”). ENS motor neurons release excitatory neurotransmitters, such as acetylcholine (ACh) and substance P (SP). Serotonin or 5-hydroxytryptamine (5-HT) 4 receptor (5-HT4R) and dopamine (DA) 2 receptor (D2R) are widely expressed in neurites within enteric ganglia. DA inhibits release of ACh from intrinsic cholinergic motor neurons by activating pre-junctional D2Rs. 5-HT enhances gut motility by evoking ACh release via activation of 5-HT4R. CgA is proteolytically processed to several biologically active peptides including catestatin (CST: hCgA352-372). Recently, we found that gut motility is compromised in CST-KO mice, which was restored after supplementation with CST. Furthermore, CST-KO mice show the following phenotypes: (i) enlarged stomach (gastroparesis), (ii) delayed gastric emptying, (iii) decreased 5-HT, and (iv) increased DA. CST acts as a short-term antagonist to ACh receptor (AChR), inhibiting catecholamine secretion and a long- term agonist, stimulating ACh secretion. Therefore, CST might modulate gut dysmotility by increasing secretion of ACh at the myenteric plexus and decreasing secretion of DA. Since we found decreased plasma CST in older WT mice and decreased CST in the gut of older mice, we reason that CST would play a role in attenuating gut dysmotility. We have formulated four independent synergistic hypotheses that may mediate CST’s regulation of gut motility: (i) activation of AChR, (ii) promotion of 5-HT production by enterochromaffin cells, (iii) inhibition of DA production by ENS, and (iv) maintenance of intramuscular ICC (ICC-IM) population by increasing tolerance. To validated or refute the above hypotheses, we have proposed experiments in two specific aims: Aim I: Test the hypothesis that CST improves gut motility and gastric emptying in aging mice by promoting AChR signaling, increasing 5-HT production, inhibiting DA release, and preventing loss of ICC population. Aim II: Translate CST-inspired therapeutics to combat age-associated gut dysmotility. IMPACT: The overarching focus of this proposal is to generate important information on the impact of CST and its mimetics on alleviation of age-associated gut dysmotility. Our study will be the first to directly link CST and its mimetics to gut motility, and potentially establish CST pathway as a therapeutic target for gut motility. If the outcome is positive, then new therapeutic avenues could come to light, making the risk worthwhile.