Interaction of Choline and Fat in the Prenatal Programming of Nonalcoholic Steatohepatitis

总结 非酒精性脂肪性肝炎（NASH），以肝脏甘油三酯蓄积和炎症为特征， 这是一个日益严重的公共卫生问题，影响了大约7%的美国人口。据推测， 肥胖首先对胎儿肝脏造成代谢打击，使其开始脂肪积累并增加易感性 然而，出生后的致肥环境施加了导致NASH的进一步打击。在这一提议中， 我们将使用胆碱，一种半必需营养素，来预防NASH的产前编程。胆碱 在脂质代谢中起重要作用，促进肝脏脂质输出，并作为甲基供体， 通过表观遗传机制改变脂质代谢基因的表达。我们实验室之前的研究表明 在肥胖小鼠母鼠中母体胆碱补充剂（MCS）可防止过量甘油三酯蓄积， 在胎儿肝脏中，部分是通过增加脂肪生成基因Srebf 1的DNA甲基化， 葡萄糖稳态。MCS还增加了长链多不饱和脂肪酸的丰度， 含有缩醛磷脂（一组充当牺牲抗氧化剂的磷脂）的LC-PUFA， 后代。由于NASH肝脏的特征在于氧化应激和LC-PUFA缺乏，因此MCS可能 降低NASH的这些风险因素。有趣的是，MCS的有益效果在后代中更为突出， 其母鼠在妊娠期间也接受高脂（HF）喂养，表明胆碱和 高频喂养。本研究的目的是确定CS与膳食脂肪的交互作用， NASH的产前编程。总体假设是产前和产后CS 改善由母体HF、致肥胖饮食引发的NASH发展; CS将与LC-PUFA协同作用 补充以进一步防止NASH的产前编程。在目标1中，我们将确定 终身胆碱补充（CS）对预防HF喂养引起的NASH产前编程的影响。 HF诱导的肥胖母鼠所生的后代小鼠将接受HF，高果糖西式饮食（WD）， 断奶引发NASH胆碱将在不同的生命阶段补充，以辨别其作用的时间， 在产前阶段（首次命中）、产后阶段（随后命中）或两者（首次和随后命中）进行干预。我们 将使用稳定同位素示踪来辨别胆碱优先分配到其代谢命运， 磷脂酰胆碱或甜菜碱，从而影响肝脏脂质组学特征和后期的表观遗传调节 生活中在目标2中，我们将确定CS和LC-PUFA共补充对NASH预防的作用。 小鼠母鼠和后代都将接受鱼油补充的HF或WD饮食以及CS。我们将 比较鱼油和CS对NASH特征和脂质组学特征的联合作用。本研究将提供 单独使用胆碱或与LC-PUFA组合使用胆碱作为具有成本效益和 用于通过产前和产后HF、致肥胖饮食暴露编程的NASH的无害预防剂。

Summary Nonalcoholic steatohepatitis (NASH), characterized by hepatic triglyceride accumulation and inflammation, is a growing public health problem that affects about 7% of the U.S. population. It is hypothesized that maternal obesity exerts the first metabolic hit to the fetal liver, priming it for fat accumulation and increased susceptibility to NASH, whereas a postnatal obesogenic environment imposes further hits that result in NASH. In this proposal, we will use choline, a semi-essential nutrient, to prevent the prenatal programming of NASH. Choline plays an important role in lipid metabolism, facilitating hepatic lipid export and serving as a methyl donor which modifies expression of lipid metabolic genes via an epigenetic mechanism. Prior research of our lab suggests that maternal choline supplementation (MCS) in obese mouse dams prevented excess triglyceride accumulation in the fetal liver partly by increasing the DNA methylation of the lipogenic gene Srebf1 and improved blood glucose homeostasis in early adulthood. MCS also increased the abundance of long-chain polyunsaturated fatty acids (LC-PUFAs) containing plasmalogens, a group of phospholipids that serve as sacrificial antioxidants, in the offspring. Since the NASH liver is characterized by oxidative stress and LC-PUFA deficiency, MCS may mitigate these risk factors of NASH. Interestingly, the beneficial effects of MCS was more prominent in offspring whose dams also received high-fat (HF) feeding during gestation, suggesting an interaction between choline and HF feeding. The objective of this study is to determine the interactive effect of CS with dietary fat on preventing the prenatal programming of NASH. The overarching hypothesis is that prenatal and postnatal CS would ameliorate NASH development initiated by a maternal HF, obesogenic diet; CS would synergize with LC-PUFA supplementation to further prevent the prenatal programming of NASH. In Aim 1, we will determine the effect of lifelong choline supplementation (CS) on preventing the prenatal programming of NASH by HF feeding. Offspring mice born to HF-induced obese dams will receive a HF, high-fructose Western style diet (WD) post- weaning to trigger NASH. Choline will be supplemented at different life stages to discern its effect by timing of intervention during the prenatal period (first hit), postnatal period (later hits), or both (first and later hits). We will use stable isotope tracing to discern the preferential partitioning of choline into its metabolic fates as phosphatidylcholine or betaine, thereby influencing the hepatic lipidomic profile and epigenetic regulation later in life. In Aim 2, we will determine the effect of CS and LC-PUFA co-supplementation on NASH prevention. Both mouse dams and offspring will receive a fish oil supplemented HF or WD diet as well as CS. We will compare the joint effect of fish oil and CS on NASH characteristics and lipidomic profile. This study will provide proof-of-concept evidence for the use of choline alone or in combination with LC-PUFA as a cost-effective and innocuous prophylactic agent for NASH programmed by prenatal and postnatal HF, obesogenic diet exposures.