Regulation of Intestinal Fructose Transport in Neonatal Rats

出生时，胎盘营养停止，肠内营养开始。 小肠突然获得了一个新的功能：从牛奶中吸收营养。 此后不久，断奶哺乳动物的小肠面临着一个新的挑战：合成不同类型或不同数量的转运蛋白，以匹配饮食中不同类型营养物质浓度的预期变化。 肠道细胞如何制造，以及“知道”何时制造这些转运蛋白？ 与其他细胞不同，肠细胞直接暴露于肠腔中存在的环境信号。 已知激素可调节肠道酶的出现，但其在调节肠道营养转运蛋白中的作用尚不清楚。 饮食或管腔信号相对于激素信号在调节营养转运蛋白中的重要性是什么？ 本项目的长期目标是确定发育过程中调节肠道营养物质转运的机制。肠道果糖转运蛋白GLUT5通常在断奶后才产生。 然而，过早引入其底物，膳食果糖，诱导这种转运蛋白的早期出现。 因此，GLUT 5将被用作模型，以评估饮食和激素信号在调节出生后肠道营养物质转运增加中的作用。 该项目将试图确定控制肠道发育的营养响应调节机制，并重新编程正常的吸收发育模式，以使肠道在发育的早期阶段处理营养物质。 这将是重要的，在进一步了解机制，控制肠道生长和成熟的早产儿。 果糖是美国人饮食中越来越重要的成分，对肠道果糖吸收本身的研究远远落后于对葡萄糖和氨基酸转运的研究，具有重要的营养意义。

At birth, placental nutrition ceases and enteral nutrition begins. The small intestine abruptly acquires a new function: to absorb nutrients from milk. Shortly thereafter, the small intestine in weaning mammals faces a new challenge: to synthesize different types or different numbers of transporters to match expected changes in concentrations of different types of nutrients from the diet. How do intestinal cells make, and 'know' when to make, these transporters? Unlike other cells, intestinal cells are directly exposed to environmental signals present in the intestinal lumen. Hormones are known to regulate the appearance of intestinal enzymes, but their role in regulating intestinal nutrient transporters is not known. What is the importance of dietary or luminal signals relative to hormonal signals in modulating nutrient transporters? The long term objective of this project is to determine the mechanisms regulating intestinal nutrient transport during development. The intestinal fructose transporter GLUT5 is normally not made until after completion of weaning. However, precocious introduction of its substrate, dietary fructose, induces the early appearance of this transporter. GLUT5 will therefore be used as a model to evaluate the role of dietary and hormonal signals in modulating postnatal increases in intestinal nutrient transport. This project will attempt to identify nutrient-responsive regulatory mechanisms controlling gut development, and to reprogram normal developmental patterns of absorption in order to allow the intestine to process nutrients at an earlier stage of development. It will be important in furthering an understanding of mechanisms that control intestinal growth and maturation in premature infants. Fructose is an increasingly important component in American diets, and studies on intestinal fructose absorption per se, which have lagged way behind those on glucose and amino acid transport, have major nutritional significance.