Medium Chain Triglycerides and Ketogenesis

背景：中脂肪酸链以中链甘油三酯（MCT）的形式自然存在，可以在椰子油和棕榈油中找到。MCT有不同的形式，可以在柜台购买作为膳食补充剂（MCT油）。与其他脂肪酸不同，MCT提供即时能量，因为它们能够非常迅速地穿过双线粒体膜，这导致酮体（KB）的产生。有趣的是，许多研究表明MCT补充剂可以增加循环KB并提高运动表现。然而，MCT的生物学作用以及MCT促进酮体生成（Ketogenesis）的机制研究相对较少。因此，本建议的主要目的是阐明MCT补充增加肝脏生酮的机制，随后这将增强肝脏线粒体功能。假设：我们假设MCT补充剂通过增加线粒体3-羟甲基戊二酰辅酶a合成酶（HMGCS2）的命运来增加循环KB，从而改善肝脏线粒体功能。方法：我们将利用一些细胞培养和动物方法来揭示MCT补充剂如何增加肝脏中KB的产生率。这包括用不同形式和浓度的MCT培养和处理肝细胞系（HepG2），并评估生酮酶和肝线粒体功能。此外，我们将给小鼠喂食富含MCT的饮食12周，通过肝脏提取物的mRNA/蛋白表达谱来确定MCT治疗是否会增加循环KB，增强生酮途径（如HMGCS2）和肝脏线粒体功能。此外，能量消耗和能量底物偏好将通过间接量热测量确定小鼠接受富含mct的饮食。目的：本研究计划将包括两个具体目标；(1)确定MCT治疗后肝脏中生酮酶（HMGCS2）是否增强；(2)评估MCT治疗是否增加肝脏线粒体功能。在目的1中，我们将用不同形式和浓度的MCT处理培养的HepG2，并评估生酮代谢途径的mRNA/蛋白表达谱。此外，我们将测量mct丰富饮食小鼠的循环KB，并通过间接量热法评估其全身氧气消耗率和呼吸交换率。在目标2中，我们将评估涉及线粒体功能的一些关键因素。影响：我们的研究结果将深入了解MCT补充剂提高酮体产生率和肝线粒体功能的机制。此外，该研究项目的结果还提供了重要的见解，即对于将MCT作为非处方营养膳食补充剂销售以增加KB的制造商来说，应该允许哪些“声明”。

Background: Medium fatty acids chain occur naturally as medium chain triglycerides (MCT) and can be found in coconut and palm oils. MCT have different forms and can be purchased over the counter as a dietary supplement (MCT oil). Unlike other fatty acid, MCT provide immediate energy because they are able to cross the double mitochondrial membrane very rapidly, and this results in the production of ketone bodies (KB). Of interest, many studies have shown that MCT supplements rise circulating KB and enhance athletic performance. However, the biological actions of MCT, and the mechanisms by which MCT may enhance ketone body production (Ketogenesis) have been relatively understudied. Hence, the major aims of this proposal are to elucidate the mechanisms by which MCT supplement increases ketogenesis in liver, and subsequently this will enhance liver mitochondrial function. Hypothesis: We hypothesize that MCT supplement increases circulation KB by augmenting the fate committing ketogenic enzyme mitochondrial 3-hydroxymethylglutaryl-CoA synthase (HMGCS2), as a result this will improve hepatic mitochondrial function. Methodology: We will utilize a number of cell culture and animal approaches to reveal how MCT supplement augment KB production rates in the liver. This includes culturing and treating liver cell line (HepG2) with different forms and concentrations of MCT, and assessing the ketogenesis enzymes and hepatic mitochondrial function. Furthermore, we will subject mice to MCT-rich diet for 12 weeks to determine whether MCT treatment increases circulating KB, enhances ketogenic pathway (e.g. HMGCS2) and hepatic mitochondrial function via mRNA/protein expression profiling of liver extracts. Moreover, energy expenditure and energy substrate preference will be determined in mice subjected to MCT-rich diet via indirect calorimetry measurements. Aims: This research proposal will encompass 2 specific aims; (1) To determine whether the ketogenic enzyme (HMGCS2) is augmented in the liver following treatment with MCT, and (2) to assess whether MCT treatment increases hepatic mitochondrial function. In aim 1, we will treat cultured HepG2 with different forms and concentrations of MCT, and assess mRNA/protein expression profile of ketogenic metabolic pathway. Furthermore, we will measure circulating KB in mice subjected to MCT-rich diet and assess their whole body O2 consumption rates and respiratory exchange ratio via indirect calorimetry. In aim 2, we will assess a number of key factors involved in mitochondrial function. Impact: Our findings will yield insight into the mechanism by which MCT supplement enhances ketone body production rates and hepatic mitochondrial function. Moreover, the results of this research program also provide significant insights into what "claims" should be allowed for manufacturers who market MCT as an over-the-counter nutraceutical dietary supplement to augment KB.