New regulators of lipid metabolism in immature cardiomyocytes

项目摘要 在正常婴儿中，血浆脂质水平在出生前保持相对较低。此后，它们急剧上升， 开始母乳或配方奶喂养。当婴儿足月出生时，他或她的心肌细胞已经 产生了生化机制，代谢长链脂肪酸，通过β- 氧化和氧化磷酸化，并且它们不再对脂质毒性敏感。但 似乎高水平的脂质对未成熟的细胞是有毒的。不幸的是，没有研究表明 未成熟心肌细胞的脂毒性。这一差距很重要，原因有两个：1）怀孕妇女 肥胖、糖尿病或先兆子痫患者的甘油三酯高于正常，游离脂肪酸高于正常 acids.因此，婴儿的脐带血也具有这些脂质的升高水平。2)过早 婴儿经常被给予具有高水平脂肪酸和其它复合脂质的市售脂质制剂。 在这两种情况下，未成熟的心脏细胞暴露于病理性高脂质水平。本申请是 旨在确定发育中的绵羊心肌细胞对妊娠中观察到的脂质水平的脆弱性， 条件不好的女人这个应用程序的目的是了解两个understudied 心脏发育的特点：1）心肌细胞代谢如何受到其脂质的影响 出生前后的环境和2）心肌细胞的代谢成熟过程是如何 由三种强大的影响调节，这些影响在脂质代谢的背景下尚未研究。所以我们 总体假设是：1）未成熟的心肌细胞更容易受到胎儿脂质异常升高的影响 2）心肌细胞的成熟是由正常的减少， 转录因子Meis 1的表达和胎儿血液中甲状腺激素水平的升高 并受到胎盘功能不全的抑制。目标1将确定饱和长链的毒性水平 脂肪酸，棕榈酸（PA）和单不饱和脂肪酸，油酸（OA 从100日龄、135日龄和14日龄新生绵羊中采集。此外，这些细胞吸收和储存 荧光长链脂肪酸类似物BODIPY C-12也将在暴露前后进行测定 PA和OA的高水平。目的2将确定Meis 1在调节代谢转换中的作用， 糖酵解到氧化磷酸化在成熟的心肌细胞，目标3将确定程度， 甲状腺激素促进心肌细胞成熟和抵抗脂毒性，Aim 4将 确定胎盘功能不全阻碍心肌细胞成熟的程度， 脂毒性的脆弱性。这些发现将为对人类婴儿的新研究提供基础， 对于需要营养治疗和出生时血浆水平有毒的婴儿来说， 长链脂肪酸

Project Summary In normal babies, plasma lipid levels remain relatively low until birth. Thereafter, they rise dramatically with the onset of breast or formula feeding. By the time a baby is born full term, his or her cardiomyocytes have generated the biochemical machinery to metabolize long chain fatty acids for generating ATP through β- oxidation and oxidative phosphorylation and they are no longer susceptible for lipid toxicity. However, it appears that high levels of lipid can be toxic to immature cells. Unfortunately, there are no studies of lipotoxicity in immature cardiomyocytes. This gap is important for two reasons: 1) pregnant women who are obese, diabetic or have preeclampsia have higher than normal triglycerides and higher than normal free fatty acids. As a consequence, the cord blood of babies also has elevated levels of these lipids. 2) premature babies are often given a commercial lipid preparation with high levels of fatty acids and other complex lipids. In both cases, immature heart cells are exposed to pathologically high lipid levels. This application is designed to determine the vulnerability of developing ovine cardiomyocytes to lipid levels seen in pregnant women with compromising conditions. The purpose of this application is to understand two understudied features of heart development: 1) How cardiomyocyte metabolism can be detrimentally affected by its lipid environment before and after birth and 2) how the metabolic maturation process in cardiomyocytes is regulated by three powerful influences that remain unstudied in the context of lipid metabolism. Thus, our global hypothesis is that 1) immature cardiomyocytes are more vulnerable to abnormal elevations in fetal lipid levels than postnatal myocytes and 2) the maturation of cardiomyocytes is augmented by normal reductions in the expression of the transcription factor, Meis1, and elevations of thyroid hormone levels in the fetal blood and is suppressed by placental insufficiency. Aim 1 will determine the toxic levels of the saturated long chain fatty acid, palmitic acid (PA) and the mono-unsaturated fatty acid, oleic acid (OA) for fetal cardiomyocytes taken from sheep at 100d, 135d, and 14d neonates. In addition, the ability of these cells to take up and store fluorescent long chain fatty acid analogue, BODIPY C-12, will also be determined before and after exposure to high levels of PA and OA. Aim 2 will determine the role of Meis1 in regulating the metabolic transition from glycolysis to oxidative phosphorylation in maturing cardiomyocytes, Aim 3 will determine the degree to which thyroid hormone promotes maturation of cardiomyocytes and resistance to lipotoxicity and Aim 4 will determine the degree to which placental insufficiency stunts maturity of cardiomyocytes and promotes their vulnerability for lipotoxicity. Findings will provide the basis for new studies on human infants to help provide the most helpful fuel mixes for babies who need nutrition therapy and who are born with toxic levels of plasma long chain fatty acids.