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

叶酸是单碳代谢（OCM）的关键调节剂，OCM是一种生化途径，为许多反应提供甲基，包括数百种必需的甲基转移酶。叶酸（FA）是一种合成的非活性形式的叶酸，比食物中的天然形式（5-甲基四氢叶酸（5mTHF））更稳定，在包括美国在内的87个国家的法律中得到强制规定。人们代谢FA到5mTHF的能力各不相同，导致未代谢FA (UMFA)，在95%的美国人的血清中存在。虽然充足的叶酸摄入对人体健康至关重要，但血清中UMFA的广泛存在引发了有关潜在意想不到的不良影响的问题。专家小组系统地审查了高摄入脂肪酸的安全性，得出结论，有强有力的证据表明脂肪酸的益处，例如神经管缺陷的预防，但非ntd结果的不确定性。许多人认为，迫切需要确定与高FA摄入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有意义的变化。本提案的目标是利用孟加拉国最近完成的FA补充随机、双盲、安慰剂对照试验（RCT） （FACT, n=610）的大量数据和存储样本。与美国不同的是，孟加拉国的人口是FA-naïve，因为食物中不添加FA。我们建议纳入新的研究，将使用新的高分辨率代谢组学（HRM）。非靶向代谢组学是对小分子代谢物的定量测量，它捕获了几乎所有代谢疾病发展中涉及的所有代谢活跃器官系统活动的无偏快照。FACT研究设计包括补充FA（400或800µg/d x 12或24周），以及停止FA后的“洗脱”期。本研究设计允许我们识别和验证新的代谢物和由FA补充（目标1）和UMFA（目标2）改变的途径，并确定这些影响随时间的稳定性或可逆性。我们将与西奈山高分辨率代谢组学设施的负责人Walker博士合作，将FACT严格的随机对照试验方法（确定因果关系的黄金标准设计）与人力资源管理相结合，后者可询问80%以上的代谢途径。我们将测试FA补充和/或UMFA影响未预料到的下游代谢物和途径的假设，并确定那些可能与健康结果相关的假设。在目标3中，我们将与遗传学家Pierce博士合作，评估基因变异如何影响FA补充和UMFA对代谢组学结果的影响。在Aim 4中，我们将与Kioumourtzoglou博士一起使用新的模式识别和分层方法来识别受FA补充和/或UMFA影响的特定代谢模式。这项研究的结果可能会为有关FA强化计划以及非处方补充剂和流行饮料产品中使用的叶酸的形式和剂量的政策决策提供信息。

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.