Dietary Regulation of Pancreatic Digestive Enzymes

描述(申请人提供)：每顿饭后不久，胰腺分泌消化各种饮食成分所需的大部分酶。为了使可利用的消化酶的数量与消化需要相匹配，消化酶的合成和腺体的大小都受到调节。这在一定程度上是通过刺激消化酶分泌的激素和神经递质，特别是CCK，但也通过饮食成分，特别是氨基酸。这项拟议工作的目的是表征这种调控，揭示分子机制，并将刺激机制与整合反应联系起来。这项建议的具体目的包括：(1)确定食物、氨基酸和CCK诱导胰腺消化酶合成的作用和机制。我们将首先确定喂食后小鼠胰腺蛋白质合成增强的时间进程和程度。将评估翻译起始因子，特别是elF2和eIF4E以及p70核糖体S6激酶的激活状态。我们将确定氨基酸，特别是亮氨酸作为启动蛋白质合成和激活翻译机制的信号的作用。我们还将确定CCK、氨基酸和胰岛素在调节蛋白质合成方面的相对重要性和协同作用。(2)探讨CCK和氨基酸在促进胰腺生长中的作用。我们将确定在没有CCK的情况下饮食蛋白质对MAP激酶和其他生长调节途径的影响，我们将确定在没有CCK的情况下饮食诱导的生长是否依赖于钙调神经磷酸酶，类似于正常饮食中CCK的作用。(3)探讨钙调神经磷酸酶诱导胰腺蛋白质合成和生长的机制。激活的钙调神经磷酸酶是否足以诱导生长和蛋白质合成将被确定。我们还将确定钙调素诱导的基因调控是否参与生长反应。这些研究将在正常小鼠身上进行，这些小鼠喂食不同的饮食或灌胃给予胰蛋白酶抑制剂或氨基酸。他们还将利用CCK缺失的突变小鼠品系，并涉及构建以胰腺为靶点的具有结构性活性的钙调神经磷酸酶转基因小鼠品系。研究将在体内和在分离的胰腺腺泡中进行。免疫抑制剂如环磷酰胺A和FK506将被用来抑制钙调神经磷酸酶和雷帕霉素来抑制mTOR。这项工作，除了了解正常的功能，可能有助于设计饮食，最大限度地刺激胰腺生长，以抵消胰腺功能不全。

DESCRIPTION (provided by applicant): The pancreas shortly after each meal secretes the majority of the enzymes required for digestion of a diverse array of dietary components. To match the amount of available digestive enzymes to digestive need, both the synthesis of digestive enzymes and the size of the gland are regulated. This is in part via the hormones and neurotransmitters that stimulate digestive enzyme secretion, particularly cholecystokinin (CCK), but also by dietary components, particularly amino acids. It is the purpose of the proposed work to characterize this regulation, uncover the molecular mechanisms, and relate the stimulatory mechanisms to the integrative response. Specific Aims of this proposal include: (1) determining the role and mechanism by which food, amino acids and CCK induce the synthesis of pancreatic digestive enzymes. We will first establish the time course and extent of enhanced pancreatic protein synthesis in mice after feeding. The state of activation of translation initiation factors, particularly elF2 and eIF4E, and p70 ribosomal S6 kinase will be evaluated. We will determine the effects of amino acids particularly leucine as a signal to initiate protein synthesis and activate the translation machinery. We will also determine the relative importance and synergy of CCK, amino acids and insulin in regulating protein synthesis. (2) We will determine the role by which CCK and amino acids enhance pancreatic growth. We will determine the effects of dietary protein in the absence of CCK on MAP kinase and other growth mediating pathways, and we will determine if diet-induced growth in the absence of CCK is dependent on calcineurin, similar to the effect of CCK with a normal diet. (3) We will determine the mechanism of calcineurin in induction of pancreatic protein synthesis and growth. Whether activated calcineurin is sufficient to induce growth and protein synthesis will be determined. We will also determine whether calcincunn-induced gene regulation is involved in the growth response. These studies will be carried out in normal mice fed different diets or gavage-fed trypsin inhibitor or amino acids. They will also make use of a mutant mouse line with CCK-deleted and involve the construction of a transgenic mouse line with constitutively active calcineurin targeted to the pancreas. Studies will be carried out both in vivo and in isolated pancreatic acini. Immunosuppressants such as cyclosponn A and FK506 will be used to inhibit calcineurin and rapamycin to inhibit mTOR. This work, in addition to understanding normal function may assist in designing diets to maximally stimulate pancreatic growth to counteract pancreatic insufficiency.