New regulators of lipid metabolism in immature cardiomyocytes

项目摘要 在正常婴儿中，血脂水平在出生前一直保持在相对较低的水平。此后，随着 母乳喂养或配方奶喂养开始。当婴儿足月出生时，他或她的心肌细胞已经 通过β产生代谢长链脂肪酸生成三磷酸腺苷的生化机制- 氧化和氧化磷酸化，它们不再对脂质毒性敏感。然而，它 似乎高水平的脂质会对未成熟的细胞产生毒性。不幸的是，目前还没有关于 未成熟心肌细胞的脂毒性。这种差距之所以重要，有两个原因：1)怀孕的女性 肥胖、糖尿病或先兆子痫患者的甘油三酯高于正常，游离脂肪高于正常 酸。因此，婴儿的脐带血中这些脂质的水平也会升高。2)过早 婴儿经常被给予一种含有高水平脂肪酸和其他复杂脂质的商业脂肪制剂。 在这两种情况下，未成熟的心脏细胞都暴露在病理性的高脂水平下。此应用程序是 旨在确定发育中的绵羊心肌细胞对妊娠期血脂水平的易感性 条件恶劣的女性。这个应用程序的目的是理解两个未被研究的 心脏发育的特点：1)心肌细胞的代谢如何受到其脂质的不利影响 出生前后的环境以及2)心肌细胞的代谢成熟过程是如何的 受三种在脂类代谢背景下仍未被研究的强大影响的调节。因此，我们的 全球假说是：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 水平高于出生后的心肌细胞和2)心肌细胞的成熟是通过正常减少 转录因子Meis1的表达与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 胎儿心肌细胞脂肪酸棕榈酸(PA)和单不饱和脂肪酸油酸(OA) 取自出生后100d、135d和14d的绵羊。此外，这些细胞的吸收和存储能力 荧光长链脂肪酸类似物BODIPY C-12也将在暴露前后进行测定 到高水平的PA和OA。目标2将确定Meis1在调节代谢转变中的作用 在成熟的心肌细胞中，糖酵解到氧化磷酸化，目标3将决定 甲状腺激素促进心肌细胞成熟和抗脂毒性，Aim 4将 确定胎盘功能不全在多大程度上阻碍心肌细胞的成熟并促进其成熟 对脂毒性的脆弱性。这些发现将为对人类婴儿的新研究提供基础，以帮助提供 对于需要营养治疗和出生时血浆有毒的婴儿来说，最有帮助的混合燃料 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.