THE ROLE OF DIETARY CARBOHYDRATE ON MATERNAL FAT MOBILIZATION AND OXIDATION D

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 由于肥胖风险的增加，许多哺乳妇女担心在不影响她们产奶量的情况下减轻怀孕期间增加的体重。我们以前已经证明，与葡萄糖相比，口服半乳糖的升糖指数较低，它可以提供一种营养底物，转化为葡萄糖，从而为乳糖的合成提供底物，但不会通过增加血糖和胰岛素来抑制脂肪动员。 这项研究的目的是确定高(葡萄糖)和低(半乳糖)胰岛素刺激的口服碳水化合物餐对产后和对照组妇女脂肪动员和氧化的影响。我们假设，一种不刺激胰岛素分泌的等卡路里碳水化合物饮料，与刺激显著胰岛素分泌的饮料相比，将促进脂肪动员和氧化，并且不会影响健康哺乳妇女的乳汁产量。如果我们证明口服碳水化合物的性质影响脂肪酸动员和脂肪氧化，而不影响乳糖合成和牛奶产量，我们就有科学证据设计一项更广泛的临床试验，让那些希望在保持成功母乳喂养的同时减肥的母乳喂养母亲参加。 一、假说 假设：在三天的时间里，不刺激胰岛素分泌的等卡路里碳水化合物饮料(低血糖指数)与刺激显著胰岛素分泌的碳水化合物饮料(高血糖指数)相比，将： 促进脂肪动员和氧化。 二、对健康哺乳期妇女的产奶量没有影响。 这一假设将在两个不同的方案中进行检验。在方案(1)中，饮料要么是葡萄糖，要么是半乳糖，提供受试者每日基础代谢需求的55%。方案(2)将与方案(1)相同，只是饮料将额外添加15%的蛋白质、必需脂肪酸、矿物质和维生素。因此，这种饮料的碳水化合物含量将与方案(1)中使用的完全相同，但将提供基础代谢率的70%。 具体目标 这项研究的目的是确定低(半乳糖)和高(葡萄糖)血糖指数饮食碳水化合物含量在减少卡路里的饮食中是否会促进脂肪的动员和氧化，而不会对牛奶产量或牛奶成分产生不利影响。 了解哺乳期对母体新陈代谢的代谢影响和乳糖合成的调节，将为调节人类乳汁生产提供新的见解，提供新的战略，以提高成功哺乳妇女的数量，并使妇女在保持足够的乳汁产量的同时减轻不必要的体重。 许多哺乳期女性担心的是减轻怀孕期间的体重。有大量的饮食方法可以实现减肥。许多西方饮食中常见的高碳水化合物食物会产生高血糖反应(高血糖指数)。这些饮食会导致血糖迅速升高，导致胰岛素释放，从而抑制脂肪动员。因此，高血糖指数饮食可能会以一种可能导致身体脂肪增加的方式改变燃料分配。另一方面，产生低血糖反应的饮食(低血糖指数饮食)可能会加强体重控制，因为它们能促进饱腹感，并最大限度地减少餐后胰岛素分泌。 虽然恢复孕前体重应该是目标，但极端的饮食行为可能会损害牛奶产量。据推测，乳糖量的主要决定因素是乳糖产量。我们最近已经证明，口服半乳糖具有低血糖指数，提供了一种转化为葡萄糖的营养底物，并且仅极小地提高了血糖和胰岛素浓度。因此，半乳糖是乳糖合成的潜在底物，也可能促进脂肪动员。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Due to the increasing obesity risks, many lactating women are concerned about losing weight gained during pregnancy without adversely affecting their milk production. We have demonstrated previously that oral galactose which has low glycemic index compared to glucose, may provide a nutrient substrate that is converted to glucose, thus providing a substrate for lactose synthesis but not inhibit fat mobilization by increasing plasma glucose and insulin. The objective of this study is to determine the impact of a high (glucose) versus low (galactose) insulin stimulating oral carbohydrate meal on mobilization and oxidation of fat in post-partum and control women. We hypothesize that an isocaloric carbohydrate drink which does not stimulate insulin secretion, when compared to one which stimulates significant insulin secretion will promote fat mobilization and oxidation and will not affect on milk production in healthy lactating women. Should we demonstrate that the nature of the oral carbohydrate affects fatty acid mobilization and fat oxidation with no impact on lactose synthesis and milk production, we would have the scientific evidence to design a wider clinical trial of breast-feeding mothers who are desirous of losing weight while sustaining successful breast feeding. I. HYPOTHESIS Hypothesis: Over a three day period, an isocaloric carbohydrate drink which does not stimulate insulin secretion (low glycemic index), when compared to one which stimulates significant insulin secretion (high glycemic index) will: i. Promote fat mobilization and oxidation. ii. Have no effect on milk production in healthy lactating women. This hypothesis will be tested in two different protocols. In protocol (1) the drink will be either just glucose or just galactose providing 55% of the subject's daily basal metabolic needs. Protocol (2) will be the same as protocol (1) with the exception that the drink will be supplemented with extra 15% protein, essential fatty acids, minerals and vitamins. Thus, this drink will have exactly the same carbohydrate content as that used in protocol (1) but will provide 70% of the basal metabolic rate. SPECIFIC AIMS The objective of this study is to determine whether low(galactose) versus high (glucose) glycemic index dietary carbohydrate content in a diet with reduced calories will facilitate fat mobilization and oxidation without adversely affecting milk production, or milk composition. Understanding the metabolic consequences of lactation on maternal metabolism and the regulation of lactose synthesis will give new insights into the regulation of human milk production, providing new strategies to improve the number of successfully breastfeeding women and to allow women to lose unwanted weight while maintaining adequate milk production. Many lactating women are concerned about losing weight gained during pregnancy. A large number of dietary approaches to achieve weight loss are available. Many high-carbohydrate foods common to Western diets produce a high glycemic response (high-glycemic index). These diets induce a rapid increase in blood glucose, resulting in insulin release which leads to inhibition of fat mobilization. Thus high-glycemic index diets may result in altering fuel partitioning in a way that may lead to body fat gain. On the other hand, diets that produce a low glycemic response (low-glycemic index diets) may enhance weight control because they promote satiety and minimize postprandial insulin secretion. Although regaining pre-pregnancy weight should be the goal, extreme dietary behaviors could impair milk production. It is postulated that the primary determinant of milk volume is lactose production. We have recently demonstrated that oral galactose, which has a low-glycemic index, provides a nutrient substrate that is converted to glucose and only minimally increases plasma glucose and insulin concentrations. Thus galactose is a potential substrate for lactose synthesis that might also promote fat mobilization.