Metabolomic and nutrigenetic effects of folic acid supplementation and unmetabolized folic acid

叶酸是一碳代谢(OCM)的关键调节剂，OCM是一种生化途径，为包括数百种必要的甲基转移酶在内的许多反应提供甲基。在食品中添加叶酸(FA)是一种合成的非活性叶酸，比食品中的天然叶酸(5-甲基四氢叶酸(5mTHF))更稳定，包括美国在内的87个国家的法律规定了这一点。人们将FA代谢成5mTHF的能力各不相同，导致了非代谢FA(UMFA)，这种物质存在于95%的美国人的血清中。虽然充足的叶酸摄入量对人类健康至关重要，但血清中普遍存在的UMFA引发了关于潜在的意想不到的不良影响的问题。系统审查高FA摄入量的安全性的专家小组得出结论，有强有力的证据表明FA的益处，例如对于神经管缺陷的预防，但对非NTD的结果不确定。许多人认为，迫切需要确定与高FA摄入量相关的代谢物和代谢途径的变化。代谢组提供了一种强大的方法来做到这一点，因为它整合了广泛的关键调控过程中的有意义的变化。这项建议的目标是利用最近在孟加拉国完成的FA补充随机、双盲、安慰剂对照试验(RCT)(FACT，n=610)的丰富数据和银行样本。与美国不同，孟加拉国是一个痴迷于FA的国家，因为食品中没有添加FA。我们建议纳入将使用新的高分辨率代谢组学(HRM)的新研究。非靶向代谢组学是对小分子代谢物的定量测量，它捕捉到与几乎所有代谢紊乱的发生有关的所有代谢活跃的器官系统的活动的无偏见快照。FACT研究设计包括补充FA(400或800微克/天×12或24周)，以及在FA停止后的一段“洗脱期”。这项研究设计使我们能够识别和验证FA补充(Aim 1)和UMFA(Aim 2)改变的新代谢物和途径，并确定这些影响随时间的稳定性或可逆性。与沃克博士合作，沃克博士是芒特大学高分辨率代谢组学设施的负责人。在西奈半岛，我们将结合FACT的严格随机对照试验方法-确定因果关系的黄金标准设计-与询问80%以上代谢途径的人力资源管理相结合。我们将测试补充FA和/或UMFA影响意外下游代谢产物和途径的假说，并确定可能与健康结果有关的假说。在目标3中，我们将与遗传学家皮尔斯博士合作，评估基因变异如何影响FA补充和UMFA对代谢结果的影响。在目标4中，我们将与Kioumortzoglou博士一起，使用新的模式识别和分层方法来确定受FA补充和/或UMFA影响的特定代谢模式。这项研究的发现可能会为有关FA强化计划和非处方补充剂中出售的叶酸的形式和剂量以及在受欢迎的饮料产品中使用的叶酸的政策决策提供参考。

Folate is a key regulator of one-carbon metabolism (OCM), a biochemical pathway that provides methyl groups for numerous reactions including hundreds of essential methyltransferase enzymes. Food fortification with folic acid (FA), a synthetic inactive form of folate more stable than the natural form in food (5-methyltetrahydrofolate (5mTHF)), is mandated by law in 87 countries, including the US. People vary in their ability to metabolize FA to 5mTHF, resulting in unmetabolized FA (UMFA), which is present in serum of >95% of the US population. While adequate folate intake is essential for human health, the widespread presence of UMFA in serum has raised questions regarding potential unanticipated adverse effects. Expert panels systematically reviewing the safety of high FA intake concluded there is strong evidence on the benefits of FA, e.g. for neural tube defect prevention, but uncertainty for non-NTD outcomes. Many feel that there is a critical need to identify alterations in metabolites and metabolic pathways associated with high FA intake. The metabolome offers a robust approach to do so as it integrates meaningful changes in a broad spectrum of key regulatory processes. The goal of this proposal is to leverage a wealth of data and banked samples from a recently completed randomized, double-blind, placebo-controlled trial (RCT) of FA supplementation (FACT, n=610) in Bangladesh. Unlike the US, Bangladesh is a FA-naïve population, as foods are not fortified with FA. We propose to incorporate new studies that will use novel high-resolution metabolomics (HRM). Untargeted metabolomics is the quantitative measurement of small-molecule metabolites that captures an unbiased snap-shot of the activity of all metabolically active organ systems involved in the development of almost all metabolic disorders. The FACT study design includes supplementation with FA (400 or 800 µg/d x 12 or 24 weeks), and a “wash-out” period following FA cessation. This study design permits us to identify and validate novel metabolites and pathways altered by FA supplementation (Aim 1) and UMFA (Aim 2) and to determine the stability or reversibility of those effects over time. In collaboration with Dr. Walker, leader of the high-resolution metabolomics facility at Mt. Sinai, we will combine FACT’s rigorous RCT approach – the gold standard design to determine causality – with HRM that interrogates greater than 80% of metabolic pathways. We will test the hypotheses that FA supplementation and/or UMFA influence unanticipated downstream metabolites and pathways, and identify those that may be linked to health outcomes. In Aim 3, in collaboration with geneticist, Dr. Pierce, we will evaluate how gene variants influence the effects of FA supplementation and UMFA on metabolomic outcomes. In Aim 4, with Dr. Kioumourtzoglou, we will use novel pattern recognition and hierarchical approaches to identify specific metabolic patterns that are impacted by FA supplementation and/or UMFA. The findings of this study may inform policy decisions regarding FA fortification programs and the forms and doses of folate sold in over-the-counter supplements and used in popular beverage products.