REGULATORY MECHANISMS IN KETOGENESIS AND GLUCONEOGENESIS

该提案概述了我们对三个重要项目的实验方法 涉及肝脏新陈代谢的调节问题。其中的第一个 问题涉及对监管关系的描述 线粒体介导的生酮和生糖途径 单羧酸盐转运体。我们已经提议交换 线粒体乙酰乙酸酯通过单羧酸对胞浆丙酮酸的作用 转运体是前驱体供应的主要调节器 糖异生途径。提出了几个实验来测试和验证 在各种肝脏来源的代谢系统中阐述这一假说。 将在开发特定的抑制剂方面做出相当大的努力 单羧酸转运体的最终目标是分离和 描述这一重要线粒体的分子特性 底物输送系统。第二，我们建议进行研究，以确定 α-肾上腺素能激动剂调节作用的某些方面 作为肝脏中的肾上腺素。有人建议进行实验a)来确定 释放到肝脏胞浆中的钙离子的来源 基于阿尔法刺激和b)来表征 对各种线粒体突起的α-肾上腺素能刺激。最后， 肝脏甘氨酸裂解系统的调节特性将是 在灌流的大鼠肝脏和分离的肝脏线粒体中进行了研究。 各种替代底物的可能调节效果(例如， 脂肪酸、氨基酸和酮体)和核苷酸种类(例如， 将对腺嘌呤和吡啶核苷酸进行评估。可能的抑制作用 几种化合物对线粒体甘氨酸转运的影响将是 已评估。甘氨酸裂解系统的变化将在 取自处于几种营养/激素状态的动物的肝脏(例如， 喂食、禁食糖尿病等)。最终，我们希望定义 甘氨酸合成酶多酶活力与酶活力的关系 肝脏中的复杂性和各种临床定义的高血糖状态。

This proposal outlines our experimental approach to three important regulatory problems involved in liver metabolism. The first of these problems concerns the characterization of a regulatory relationship between the ketogenic and gluconeogenic pathways mediated by the mitochondrial monocarboxylate translocator. We have proposed that the exchange of mitochondrial acetoacetate for cytosolic pyruvate via the monocarboxylate translocator is a primary regulator of the supply of precursors for the gluconeogenic pathway. Several experiments are proposed to test and to elaborate upon this hypothesis in various liver-derived metabolic systems. Considerable effort will be given to the development of specific inhibitors of the monocarboxylate translocator with an ultimate goal of isolating and characterizing the molecular properties of this important mitochondrial substrate transport system. Second, we have proposed studies to define certain aspects of the regulatory effects of Alpha-adrenergic agonists such as epinephrine in the liver. Experiments have been suggested a) to define the source of the calcium ions which are released into the liver cytosol upon Alpha-stimulation and b) to characterize the effects of Alpha-adrenergic stimulation on various mitochondrial processes. Finally, the regulatory properties of the hepatic glycine cleavage system will be investigated in perfused rat livers and in isolated liver mitochondria. The possible regulatory effects of various alternative substrates (e.g., fatty acids, amino acids and ketone bodies) and nucleotide species (e.g., adenine and pyridine nucleotides) will be assessed. Possible inhibitory effects of several compounds on mitochondrial glycine transport will be evaluated. Changes in the glycine cleavage system will be monitored in livers derived from animals in several nutritional/hormonal state (e.g., fed, fasted diabetic, etc.). Ultimately we would like to define the relationship between the activity of the glycine synthase multienzyme complex in the liver and various clinically defined hyperglycinemic states.