FRUCTOSE IN DENOVO LIPOGENESIS IN HUMANS

果糖是一种天然存在于水果和蔬菜中的糖，越来越多地被用作加工食品和饮料中的甜味剂。它对肥胖或糖尿病患者有潜在的好处；然而，有证据表明，它也可能导致血浆甘油三酯、总胆固醇和低密度脂蛋白水平升高。这些参数的增加与冠状动脉疾病的风险增加有关，特别是在已经处于这种疾病高危状态的人群中。这项研究的目的是确定饮食中果糖对正常体重、肥胖和II型糖尿病人群甘油三酯和胆固醇从头合成的影响。作为一种稳定的同位素，氚的掺入速率将被用来确定新形成的胆固醇和甘油三酯中的氚标记的掺入速率。数据将在两个饮食周期内收集。每组将招收12名学生。受试者将摄入等卡路里的流质饮食(55%碳水化合物，15%蛋白质，30%脂肪)，为期5天。在一个测量期内，30%的卡路里将由果糖供应，在另一个测量期内，30%的卡路里将由麦芽糊精供应。受试者将饮用0.7g D2O/kg全身水。在接下来的36小时内，每隔6小时将在用餐前抽取一次血样。这项研究将在几周后重复进行，届时将消耗剩余形式的糖。用薄层层析法分离血浆胆固醇和甘油三酯，用同位素比值质谱仪测定掺入的氘的量。血浆甘油三酯和胆固醇中的氚掺入速率将被用来计算从头开始脂肪生成的速率。

Fructose is a form of sugar occurring naturally in fruits and vegetables, and increasingly, as a sweetener in processed foods and beverages. It has potential benefits to obese or diabetic individuals; however, evidence exists that it may also lead to high levels of plasma triglyceride, total cholesterol, and LDL cholesterol. Increases in these parameters are associated with increased risk of coronary artery disease, especially in populations already at high risk for this disease. The purpose of this investigation is to determine the effect of dietary fructose on de novo synthesis of triglyceride and cholesterol in normal weight, obese, and Type ll diabetic populations. The rate of incorporation of deuterium, a stable isotope, will be used determine the rate of incorporation of a deuterium label into newly formed cholesterol and triglyceride. Data will be collected in 2 dietary periods. Twelve subjects will be enrolled in each group. Subjects will consume an isocaloric liquid diet (55% carbohydrate, 15% protein, 30% fat) for 5 days. During one measurement period, 30% of calories will be supplied by fructose, in the other, 30% of calories will be supplied by maltodextrine. Subjects will drink 0.7 g D2O/kg total body water. Over the next 36 hours, blood samples will be drawn every 6 hours prior to a meal. The study will be repeated several weeks later, at which time the remaining form of sugar will be consumed. Plasma cholesterol and triglyceride will be isolated by thin layer chromatography and the amount of deuterium incorporated will be determined by isotope ratio mass spectrometry. The rate of deuterium incorporation into plasma triglyceride and cholesterol will be used to calculate the rate of de novo lipogenesis.