MECHANISMS FOR DIFFERENTIAL EFFECTS OF DIETARY FATTY ACIDS ON METABOLISM

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 在世界范围内，确实存在肥胖和“2型糖尿病”的流行病（与通常在成年前发展并且具有不同原因的“1型糖尿病”不同）。 虽然肥胖有许多并发症，但2型糖尿病是一种重要的并发症，并不是所有肥胖的人都会发生，但确实会在一些不肥胖的人中发生。 因此，重要的是要了解饮食是否会促进2型糖尿病的发展。 2型糖尿病被认为部分是因为激素胰岛素不能充分发挥作用，使血糖（葡萄糖）进入肌肉细胞。 胰岛素的活性缺陷反过来被认为是因为脂肪在肌肉细胞中没有最佳地燃烧，导致“有毒脂肪”在肌肉细胞中的积累，这阻止胰岛素向肌肉细胞发出信号以允许更多的葡萄糖进入其中。“有毒脂肪”的一些实例是“DAG、神经酰胺、β-羟基丁酸酯和酰基-肉毒碱”。 我们在年轻、非肥胖、人类受试者中的初步数据表明，增加膳食饱和脂肪（棕榈酸，PA）可以降低脂肪燃烧的速率，特别是在女性中，还可以通过降低运动的能量成本来降低维持体重的每日能量成本（特别是在男性中）。 我们还有来自杜克大学的合作研究者Deborah Muoio的初步数据，她研究了啮齿动物和人类的分离肌肉细胞。 她已经表明，单不饱和脂肪（油酸，OA）会导致细胞中控制脂肪氧化的基因（“PPAR基因”）的活性增加。 她还表明，饱和脂肪导致PGC-1基因的产生（“转录”）减少，PGC-1基因激活其他基因，刺激脂肪和能量燃烧。 这些基因还抑制细胞中从饱和脂肪制造单不饱和脂肪的酶（称为SCD 1）的活性，所述酶在细胞的某些隔室中可能不同于储存膳食脂肪的隔室。 具有较低SCD 1活性的动物被保护免于肥胖，并且能够以更高的速率燃烧脂肪和能量。 Muoio博士的初步数据显示，OA导致SCD 1的活性降低。 我们将在28名18-40岁的健康、非肥胖成年人中进行喂养试验，这些人将以随机顺序被喂养实验饮食（中等高脂肪）：高OA/低PA饮食（称为HIOA）和高PA饮食（称为HIPA）（各持续3周）。 受试者和研究者将对饮食顺序的身份保持盲态，直至判定数据完整且充分。 将对每例受试者进行筛选，以确定合格性：健康且未接受药物治疗（包括避孕药）;非肥胖;久坐且身体状况不佳;血糖和血脂正常。 然后，每例受试者将喂食低脂对照饮食一周，之后将在早餐前和早餐后状态下抽血并通过大腿穿刺活检获得肌肉组织。然后，受试者将被喂食两种实验饮食中的一种，持续三周。 将重复血液和肌肉测试，然后受试者将被喂食低脂饮食一周，然后是第二次实验饮食三周。将重复最后（第三）系列血液和肌肉测试。 此外，在每个实验饮食结束时，受试者将经历脂肪和卡路里燃烧的测量（过夜）和胰岛素作用和分泌的测试（静脉内葡萄糖耐量测试）。 将评估以下目标： 1. 研究与对照低脂饮食相比，实验饮食如何调节肌肉中的PPAR和PGC基因。 2. 将全身脂肪燃烧和基因活性的变化与肌肉中各种有毒脂质的水平相关联。 3. 评估增加OA的摄入是否会降低SCD 1的活性。 4. 评价性别在影响PA和OA反应中的作用。 该项目将提供有关饮食脂肪如何改变肌肉功能的重要新信息，以及它是否在肥胖症，2型糖尿病以及遗传性和年龄相关代谢疾病的发展中发挥核心作用。

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. Worldwide, there is truly an epidemic of obesity and "type 2 diabetes" (distinguished from "type 1 diabetes" which usually develops before adulthood and has a different cause). Although there are many complications of obesity, type 2 diabetes is an important one and does not develop in all obese people but does develop in some people who are not obese. It is thus important to understand whether diet may promote the development of type 2 diabetes. Type 2 diabetes is thought to develop, in part, because the hormone, insulin, does not function adequately in allowing blood sugar (glucose) to enter the muscle cells. Defective activity of insulin is in turn thought to develop because fat is not optimally burned in the muscle cell leading to the accumulation of "toxic fats" in the muscle cell which prevent insulin from signaling the muscle cell to allow more glucose to enter it. Some examples of "toxic fats" are "DAG, ceramide, -hydroxybutyrate, and acyl-carnitines". Our preliminary data in young, non-obese, human subjects suggest that increasing dietary saturated fat (palmitic acid, PA) lowers the rate of fat burning, especially in females and also lowers the daily energy cost for maintaining body weight by lowering the energy cost of performing exercise (especially in males). We also have preliminary data from our co-investigator at Duke University, Deborah Muoio, who studies isolated muscle cells from rodents and humans. She has shown that monounsaturated fat (oleic acid, OA) causes increased activity of genes which govern fat oxidation in the cell ("PPAR genes"). She also has shown that saturated fat causes less production ("transcription) of the gene, PGC-1, which activates other genes that stimulate both fat and energy burning. These genes also inhibit the activity of an enzyme which manufactures monounsaturated fat from saturated fat in the cell (called SCD1), within certain compartments of the cell which may be distinct from the compartments where dietary fat is stored. Animals which have lower activity of SCD1 are protected from obesity and are able to burn fat and energy at an increased rate. Dr. Muoio's preliminary data show that OA caused less activity of SCD1. We will conduct a feeding trial in 28 healthy, non-obese, adults, 18-40 yr of age, who will be fed experimental diets (moderately high in fat), in random order: both a high OA/low PA diet called HI OA and a high PA diet, called HI PA (each for 3 wk). The subjects and the investigators will be masked to the identity of the order of the diets until the data are judged to be complete and adequate. Each subject will be screened to determine eligibility: healthy and not on medication (including birth control pills); non-obese; sedentary and not exceptionally physically fit; normal serum glucose and lipids in blood. Then, each subject will be fed a low-fat, control diet for one week after which blood will be drawn and muscle tissue will be obtained by needle biopsy of the thigh in the pre-breakfast and post-breakfast state. Then the subject will be fed one of the two experimental diets for three weeks. The blood and muscle tests will be repeated and then the subject will be fed the low-fat diet for one week followed by the second experimental diet for three weeks. The final (third) series of blood and muscle tests will be repeated. In addition, at the end of each of the experimental diets, the subjects will undergo measurements of fat and calorie burning (overnight) and a test of insulin action and secretion (intravenous glucose tolerance test). The following Aims will be assessed: 1. To investigate how PPAR and PGC genes are regulated in muscle in response to the experimental diets in comparison to the control, low fat, diet. 2. To correlate changes in whole-body fat burning and gene activity with levels of various toxic lipids in muscle. 3. To assess whether increasing the intake of OA lowers the activity of SCD1. 4. To evaluate the role of gender in affecting responses to PA and OA. This project will provide important new information regarding how diet fat alters the functions of muscle and whether it plays a central role in the development of obesity, type 2 diabetes, and both inherited and age-related metabolic diseases.