EFFECT OF AGING ON GASTROINTESTINAL HORMONES

这项研究建议的总体假设是胃肠道 (GI)荷尔蒙与以下变化既有因果关系 随着年龄的增长发生在胃肠道。这些与年龄相关的改变包括 1)胃肠道粘膜的增殖活性增强，以及2)a 胃肠道分泌功能下降。的长期目标是 这个项目是为了定义至少一些涉及 年龄相关性生长和分泌紊乱的病理生理学 我的胃肠道。为了确定胃肠道组织衰老的进程， 三个年龄组(4个月龄、12个月龄和24个月龄)的Fischer 344只大鼠 被利用。将建立与胃肠道激素之间的因果关系 通过给予胃肠激素作为外源性给药或作为一种 增加内源性释放，无论有没有服用 高选择性胃肠激素受体拮抗剂。一个明确的目标是 验证胃肠道粘膜细胞凋亡受胃肠道调节的假说 激素，而胃肠激素对细胞凋亡的调控作用的丧失是 导致黏膜细胞过度增殖。中的细胞凋亡 胃、十二指肠、回肠和结肠将由引起粘膜 萎缩，这将通过禁食或通过喂食 基本饮食。营养胃肠激素(如胃泌素、 CCK、神经降压素、蛙皮素)抑制 将确定细胞凋亡，并将其与胃肠道粘膜的变化相关联 细胞增殖。细胞凋亡将通过原位组织学监测 细胞核DNA片段化免疫染色。细胞增殖将会是 由BrdU核标记监测。基因表达模式 与胃肠道中的细胞凋亡相关的基因将通过 测定胃肠激素及其受体的mRNA和蛋白质水平的变化 受体，以及与凋亡相关的基因(如转化生长因子-β1、p53和bcl-1)。 2)。第二个具体目标将检验这样一种假设，即抗衰老 热量限制(CR)的作用是通过调节GI来实现的 荷尔蒙新陈代谢，进而决定了 细胞保护机制，即抗氧化剂清除酶 (过氧化氢酶和超氧化物歧化酶[SOD])和热休克蛋白(HSP)。 CR将通过喂饲CR限制大鼠60%(wt/wt) 随意喂养的大鼠摄取的食物量。CR引起的胃肠道反应改变 激素代谢将在GI激素基因水平上进行研究 表达(组织mRNA和多肽水平)和释放，并在 胃肠道激素靶点(胃肠激素受体基因)的反应性 表达)。胃肠激素代谢变化与胃肠功能的关系 胃酸分泌、胰腺外分泌和内分泌的变化 胃肠激素分泌及过氧化氢酶、超氧化物歧化酶和热休克蛋白70的表达 目标，将被确立。对涉及的机制的理解 对大鼠胃肠道生长和分泌的失调可能有所帮助 制定治疗与年龄有关的疾病的策略 人类也有类似的精神错乱。

The overall hypothesis of this research proposal is that gastrointestinal (GI) hormones are related in both cause and effect to the changes that occur in the GI tract with aging. These age-related alterations include 1) an increased proliferative activity of the GI mucosa, and 2) a decreased secretory function in the GI tract. The long-term objective of this project is to define at least some of the mechanisms involved in the pathophysiology of the age-related derangements in growth and secretion of the GI tract. To establish the progression of GI organismal aging, Fischer 344 rats of three age groups (4-mo, 12-mo, and 24-mo old) will be used. Associations of causality with GI hormones will be established by giving GI hormones either as an exogenous administration or as an increased endogenous release, with or without the administration of highly selective GI hormone receptor antagonists. One specific aim will test the hypothesis that apoptosis in GI mucosa is regulated by GI hormones, and that loss of regulation of apoptosis by GI hormones is responsible for an exaggerated mucosal cell proliferation. Apoptosis in the stomach, duodenum, ileum and colon will be induced by causing mucosal atrophy, which will be accomplished either by fasting or by feeding an elemental diet. The ability of trophic GI hormones (eg, gastrin, cholecystokinin [CCK], neurotensin [NT], bombesin [BBS]) to inhibit apoptosis will be determined, and correlated with changes in GI mucosal cell proliferation. Apoptosis will be monitored histologically by in situ immunostaining of nuclear DNA fragmentation. Cell proliferation will be monitored by BrdU nuclear labelling. Patterns of gene expression associated with apoptosis in the GI tract will be established by measuring changes in mRNA and protein levels of GI hormones and their receptors, and of apoptosis-associated genes (eg, TGF-Beta1, p53 and bcl- 2). A second specific aim will test the hypothesis that the anti-aging actions of caloric restriction (CR) operate through the regulation of GI hormone metabolism which, in turn, determines the expression of cytoprotective mechanisms, namely antioxidant scavenging enzymes (catalase and superoxide dismutase [SOD]) and heat-shock proteins (hsp). CR will be accomplished by feeding CR-restricted rats 60% (wt/wt) the amount of food ingested by ad lib fed rats. CR-induced changes in GI hormone metabolism will be investigated at the levels GI hormone gene expression (tissue mRNA and peptide levels) and release, and at the responsiveness of the GI hormone targets (GI hormone receptor gene expression). The relationships between changes in GI hormone metabolism with changes in gastric acid secretion, pancreatic exocrine and endocrine secretions, and expression of catalase, SOD and hsp70 in GI hormone targets, will be established. Understanding of the mechanisms involved in dysregulation of growth and secretion of the GI tract in rats may help to devise strategies for the treatment of age-related diseases with similar derangements in humans.