Desaturation Of Essential Fatty Acids Using Stable Isotope GC/MS

使用稳定同位素 GC/MS 进行必需脂肪酸的去饱和

基本信息

批准号：
7732110
负责人：
Joseph Hibbeln
金额：
$ 22.89万
依托单位：
NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/7732110
关键词：
Adipose tissue Adult Animal Feed Animals Arachidonic Acids Area Back Biochemical Birth Blood Blood Circulation Brain Condition Deposition Development Diet Dietary Factors Docosahexaenoic Acids Dose Drug or chemical Tissue Distribution Essential Fatty Acids Extrahepatic Fatty Acids Female Goals Growth Heart High Density Lipoproteins Human Infant Invasive Kidney Label Life Linoleic Acids Lipoproteins Liver Low-Density Lipoproteins Lung Mammals Metabolic Metabolism Methodology Milk Molecular Mus Myocardium Nervous system structure Oils Oleic Acid Oleic Acids Omega-3 Fatty Acids Oral Organ Pattern Phospholipids Plants Plasma Positron-Emission Tomography Rate Rattus Relative (related person)Research Research Project Grants Rodent Role Smoke Smoker Source Spleen Stream Suggestion Techniques Testis Thalamic structure Time Tissues Tracer Triglycerides Very low density lipoprotein alpha-Linolenic Acid base day fatty acid metabolism feeding gray matter healthy volunteer heart imaging in vivo latent nuclear antigen low density lipoprotein inhibitor male non-smoker novel nutrition problem drinker pup radiotracer research study stable isotope uptake white matter

项目摘要

Prior to the recent application of stable isotope based GC/MS methodology, little was known about in vivo essential fatty acid metabolism in animals or humans. Essential fatty acid metabolism was studies in human adults, both male and female, and those who smoked as well as non-smokers. This was a stable isotope study of in vivo metabolism of deuterated-LA and deuterated-LNA conversion after a single oral dose of these precursors. Our results indicated that female smokers had a two-fold increase in the percent of plasma dose and a higher fractional conversion rate for 22:5n-3 conversion to 22:6n-3 compared with non-smokers. Male smokers had elevated total plasma n-3 fatty acids, a more rapid turn over of D5-18:3n-3, a disappaerance rate of D5-20:5n-3 that was both delayed and slower, and a greater percentage of D5-20:5n-3 was directed into 22:5n-3 relative to non-smokers. Generally, smoking increased the bioavailablity of n-3 fatty acids from plasma, accelerated fractional conversion rates, and increased the percent formation for some long chain n-3 fatty acids. In rats, it was observed that addition of preformed DHA to the diet leads to a decreased accumulation of label from 18-C precursors into DHA and DPAn6 in several organs even though there was a significant increase in tissue DHA. Female rats accumulated more DHA and DPAn6 but less AA than males when fed a controlled diet containing 3 wt% alpha-linolenic acid. An n-3 fatty acid deficient diet led to a marked decline in labeling of liver 22:4n6 and 22:5n6 from the 18:2n6 precursor. A closely related research project concerns the origins of nervous system and other organ DHA. Possible sources are from dietary preformed DHA, from metabolism of the precursor, LNA, or from body stores of DHA. A novel technique has been developed that allows for the quantitative assessment of the amount of DHA accreted from LNA metabolism under various dietary conditions. For this study, it is necessary to control the diet from near birth up to a period where significant brain development has occurred. This has been accomplished thru the use of newly developed artifiicial rearing techniques using an artificial rat milk that was nearly devoid of n-3 fatty acids. The n-3 fatty acids are then added as deuterated-LNA and containing varying levels of DHA. In one major experiment, rat pups were fed diets with 0 or 2% DHA between days 8-29 of life. During this period, it could be calculated that 40% of the newly formed brain DHA in the animals fed D5-LNA as their only source of n-3 fatty acids were derived from preformed DHA and not from LNA metabolism. This was surprising as there was no DHA in the diet; thus, all preformed DHA deposited in the brain must have been derived from other organs via the blood stream. When DHA was added to the diet, there was a pronounced decrease in the rate of LNA metabolism to DHA, possibly due to a form of end-product inhibition, and 88% of brain DHA was derived from the preformed dietary DHA. The biochemical mechanisms underlying these metabolic effects of dietary DHA are being investigated. A decline in labeled DHA was also observed in liver, heart, muscle, kidney and testes but no such changes were observed in adipose tissues. There was also a higher level of brain DHA in the rats given preformed DHA indicating that metabolism could not provide an adequate source of brain DHA. Another finding of consequence for infants fed formulas without DHA was that several organs including the heart, lungs, kidney and spleen had a net loss of DHA content during a period of intense body growth when no preformed DHA was present in the diet. An attempt was made to determine what the underlying mechanisms for DHA transport into brain and other organs. Lipoproteins were purified and labeled with radiotracers and modified with a tracer levels of phospholipids acylated with DHA, AA or oleic acid (OA). The modified lipoproteins were intravenously injected in mice. The plasma and tissue distribution of the radiotracers were investigated as a function of time and the lipoproteins composition. We found that higher proportion of DHA in LDL results in an enhanced uptake of these lipoproteins by brain and heart. A similar enrichment of LDL in AA or OA did not result in any changes compared to control unaltered LDL. Tissue uptake of HDL did not depend on its fatty acid composition. We next compared the distribution in plasma pools and tissue uptake of 14C-DHA and 3H-(OA) intravenously injected in mice. We found that DHA is rapidly taken up by liver, selectively acylated into triglycerides and released back into the circulation in VLDL. Most of the DHA from VLDL and LDL appeared to be rapidly taken up by extrahepatic organs. This pattern seems to be unique for DHA, because no significant amount of non-essential oleic acid, traced in a similar way, was found in TG and VLDL fractions. In summary, these results point to the important role of VLDL and LDL in transport of DHA to extrahepatic tissues, and to the involvement of liver in the initial selectivity for DHA transport. A novel application of PET imaging for the study of C11-DHA incorporation into brain has been initiated. Brain and heart images from 19 healthy volunteers and 17 alcoholics have now been obtained. Extensive characterization of the fatty acid input function in plasma has been made in real time for the 11-C-DHA. Our findings thusfar are that the J(in) and K* values for male and female healthy volunteers are similar except for the K* values in the thalamus and the gray matter/white matter ratio. There is a suggestion from initial studies that alcoholics may have a lower incorporation of DHA in many areas of cortex than control subjects, but more subjects will be needed.

在最近应用基于稳定同位素的 GC/MS 方法之前，人们对动物或人类体内必需脂肪酸代谢知之甚少。对成年人（男性和女性、吸烟者和不吸烟者）进行了必需脂肪酸代谢的研究。这是一项对单次口服剂量这些前体后氘化 LA 和氘化 LNA 转化的体内代谢的稳定同位素研究。我们的结果表明，与非吸烟者相比，女性吸烟者的血浆剂量百分比增加了两倍，并且 22:5n-3 转化为 22:6n-3 的分数转化率更高。男性吸烟者的血浆 n-3 脂肪酸总量升高，D5-18:3n-3 的周转更快，D5-20:5n-3 的消失率延迟且更慢，D5 的百分比更高相对于非吸烟者，-20:5n-3 被定向为 22:5n-3。一般来说，吸烟会增加血浆中 n-3 脂肪酸的生物利用度，加速部分转化率，并增加某些长链 n-3 脂肪酸的形成百分比。在大鼠中，观察到在饮食中添加预先形成的 DHA 会导致多个器官中从 18-C 前体到 DHA 和 DPAn6 的标记积累减少，尽管组织 DHA 显着增加。当喂食含有 3 wt% α-亚麻酸的受控饮食时，雌性大鼠比雄性大鼠积累更多的 DHA 和 DPAn6，但积累的 AA 更少。缺乏 n-3 脂肪酸的饮食导致肝脏 22:4n6 和 22:5n6 的标记较 18:2n6 前体显着下降。一个密切相关的研究项目涉及神经系统和其他器官 DHA 的起源。可能的来源包括饮食中预先形成的 DHA、前体 LNA 的代谢或体内储存的 DHA。一种新技术已被开发出来，可以定量评估各种饮食条件下 LNA 代谢产生的 DHA 量。对于这项研究，有必要从出生前一直到大脑发生显着发育的时期控制饮食。这是通过使用新开发的人工饲养技术实现的，该技术使用几乎不含 n-3 脂肪酸的人造大鼠奶。然后将 n-3 脂肪酸作为氘化 LNA 添加，并含有不同水平的 DHA。在一项主要实验中，幼鼠在出生后第 8-29 天期间被喂食含有 0 % 或 2% DHA 的饮食。在此期间，可以计算出，在以 D5-LNA 作为 n-3 脂肪酸唯一来源的动物中，新形成的脑 DHA 的 40% 来自预先形成的 DHA，而不是来自 LNA 代谢。这是令人惊讶的，因为饮食中不含 DHA；因此，所有沉积在大脑中的预先形成的 DHA 必定是通过血流从其他器官中获得的。当 DHA 添加到饮食中时，LNA 代谢为 DHA 的速率显着降低，这可能是由于某种形式的终产物抑制，并且 88% 的大脑 DHA 来自预先形成的饮食 DHA。膳食 DHA 的这些代谢作用背后的生化机制正在研究中。在肝脏、心脏、肌肉、肾脏和睾丸中也观察到标记 DHA 的下降，但在脂肪组织中没有观察到这种变化。给予预先形成的 DHA 的大鼠脑部 DHA 水平也较高，这表明新陈代谢无法提供足够的脑部 DHA 来源。喂养不含 DHA 配方奶粉的婴儿的另一个后果是，在身体快速生长期间，当饮食中不存在预先形成的 DHA 时，包括心脏、肺、肾和脾在内的多个器官的 DHA 含量出现净损失。我们试图确定 DHA 转运到大脑和其他器官的潜在机制。脂蛋白经过纯化并用放射性示踪剂标记，并用示踪剂水平的 DHA、AA 或油酸 (OA) 酰化磷脂进行修饰。将修饰的脂蛋白静脉注射到小鼠体内。研究了放射性示踪剂的血浆和组织分布作为时间和脂蛋白组成的函数。我们发现 LDL 中 DHA 的比例越高，大脑和心脏对这些脂蛋白的吸收就会增加。与对照未改变的 LDL 相比，AA 或 OA 中 LDL 的类似富集并未导致任何变化。 HDL 的组织摄取不依赖于其脂肪酸组成。接下来，我们比较了小鼠静脉注射的 14C-DHA 和 3H-(OA) 的血浆池分布和组织摄取。我们发现 DHA 迅速被肝脏吸收，选择性酰化为甘油三酯，并以 VLDL 形式释放回循环中。来自 VLDL 和 LDL 的大部分 DHA 似乎被肝外器官迅速吸收。这种模式对于 DHA 来说似乎是独特的，因为以类似的方式追踪，在 TG 和 VLDL 组分中没有发现大量的非必需油酸。总之，这些结果表明 VLDL 和 LDL 在 DHA 转运至肝外组织中的重要作用，以及肝脏参与 DHA 转运的初始选择性。 PET 成像用于研究 C11-DHA 掺入大脑的新应用已经启动。现已获得 19 名健康志愿者和 17 名酗酒者的大脑和心脏图像。已对 11-C-DHA 的血浆脂肪酸输入功能进行了实时广泛表征。迄今为止我们的发现是，除了丘脑中的 K* 值和灰质/白质比率之外，男性和女性健康志愿者的 J(in) 和 K* 值相似。初步研究表明，酗酒者大脑皮层许多区域的 DHA 含量可能低于对照组，但需要更多的受试者。