短期大剂量叶酸减轻心脏病发作心肌损伤

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Brief, High Doses Of Folate -- B Vitamin -- Blunt Damage From Heart Attack


ScienceDaily (Mar. 28, 2008) — Long known for its role in preventing anemia in expectant mothers and spinal birth defects in newborns, the B vitamin folate, found in leafy green vegetables, beans and nuts has now been shown to blunt the damaging effects of heart attack when given in short-term, high doses to test animals.
每日科学（2008年3月28日）----B族维生素叶酸，主要存在于叶状蔬菜、豆类和坚果中，长期以来都已知它能够预防孕妇贫血和新生儿神经管缺陷，最近的动物实验显示短期大剂量叶酸能减轻心脏病发作所致心肌损伤。

In a new study, an international team of heart experts at Johns Hopkins and elsewhere report that rats fed 10 milligrams daily of folate, also known as folic acid or vitamin B9, for a week prior to heart attack had smaller infarcts than rats who took no supplements. On average, researchers say, the amount of muscle tissue exposed to damage and scarred by the arterial blockage was shrunk to less than a tenth.
在一项新的研究中，由约翰霍普金斯大学和其它大学心脏病专家组成的国际性团队报道，让先前有过心脏病发作的老鼠连续一周每天服用10毫克叶酸盐（即叶酸或维生素B9），发作所导致的梗死比没有服用的老鼠小。研究者们说，平均起来损伤所导致的肌肉组织总量和动脉闭塞所致斑痕缩小到不足十分之一。

The team's findings, set for publication in the April 8 edition of the journal Circulation, come just weeks after other international studies in humans suggested that low-dose folic acid supplements may prevent dementia in the elderly and premature births.
这个研究预计发表在4月8版的《循环》杂志上，是继其它的几个国际临床研究显示低剂量的叶酸可以预防老年人和早产儿痴呆后的又一重大研究。

\"We want to emphasize that it is premature for people to begin taking high doses of folic acid,\" says senior study investigator David Kass, M.D., a professor at The Johns Hopkins University School of Medicine and its Heart Institute.
实验的主要研究者、约翰霍普金斯大学医学院及心脏研究所教授David Kass博士说：“需要强调一下，让人们开始服用大剂量叶酸为时尚早。”

\"But if human studies prove equally effective, then high-dose folate could be given to high-risk groups to guard against possible heart attack or to people while they are having one,\" says Kass.
Kass说：“如果在人类身上实验证实同样有效，那么可以让那些需要预防心脏病发作或已经发作过的高危人群服用大剂量叶酸。”

The more likely and most practical advantage to ingesting supplements, he says, lies in folic acid's potential to act as a short-term buffer for people who may be having a heart attack and who rush to their local emergency room complaining of chest pain.
他还说，对于那些因心脏病发作或者胸痛紧急就诊的急诊患者来说，摄取叶酸更有可能和最实用的好处是叶酸作为一个缓冲液起作用。

Clinical trials are expected in the near future, although Kass says a major challenge in testing is that a high dose of folic acid for humans comparable to that given the rats would require an average-size adult to swallow more than 200 one-milligram pills per day, \"an impractical and unrealistic regimen, even if the body excretes the excess.\"
临床实验有望在不久的将来开始，然而Kass说实验面临一个最大的问题是，如果取相当于老鼠一样大剂量的叶酸，则需要一个正常体重的成年人每天服用200片1毫克的叶酸片，“即使机体可以排泄多余的部分，这也是不实际和不现实的服药法。”

In addition, he cautions, \"we do not yet know if folate is safe to consume in this high a dose, or how much or how little of it is needed to be effective,\" citing 25 milligrams per day as the highest dose previously tested safe to consume in adults as.
此外，他警告说：“我们不知道一次服用这么大剂量的叶酸是否安全，多大剂量才是必需的有效剂量，”先前的研究认为一个成年人每日服用25毫克叶酸是最大安全剂量。

Kass says that such large amount of folate may also yield unpredictable side effects. Some studies have linked the nutrient supplement to increased rates of colon and prostate cancer.
Kass说如此大剂量的叶酸可能产生无法预料的不良反应。一些研究证实营养强化剂与老鼠结肠和前列腺肿瘤增加相关。

Each year, an estimated 565,000 first-time heart attacks occur in the United States, with an additional 300,000 recurrent heart attacks.
美国每年估计有565,000人首次心脏病发作，另外有300,000人再发。

Results from the new study, conducted in rats - dozens were fed supplements and dozens more did not receive any - showed that overall pumping function during heart attack remained strong in vitamin B9-fortified animals.
来源于老鼠的新研究（部分服用叶酸，部分不服用）显示使用了维生素B9的动物在心脏病发作期间心脏整体泵功能保持强有力的状态。

The amount of blood pumped by the treated hearts during a 30-minute window when blood flow to the heart was restricted to simulate a heart attack stayed near normal for rodents, at an average ejection fraction of 73 percent. Meanwhile, it fell in the untreated group to 27 percent.
通过限制老鼠心脏的血流量模拟心脏病发作，当在30分钟的时间窗内采取治疗措施时，心脏泵血功能接近正常，平均摄血分数73%。而不给予治疗则会下降到27%。

Similarly, the muscle wall at the front of the heart kept contracting during heartbeats, thickening by 37 percent in the supplement-fed group, but the muscle could barely compress, thickening by 5 percent, in the untreated group. (Sixty percent would be the normal amount of thickening in a healthy rat heart.)
类似的，在叶酸治疗组心脏跳动时，心肌保持收缩，前壁增厚37%，而未治疗组几乎没有收缩，心肌增厚5%。（健康老鼠心脏收缩时增厚60%）

Moreover, researchers found that an injection of folic acid into the bloodstream of rats that had never before taken supplements, within the first 10 minutes of a heart attack, was almost equally as effective as preventive therapy in reversing muscle damage, and in lowering infarct size by a factor of 10.
而且，研究者们发现对之前没有服用叶酸的老鼠在心脏病发作后10分钟内经血管途径给予叶酸，在逆转心肌损害方面和预防性应用的效果相当，降低梗死到10%。

\"Folic acid is already well known to be safe to consume in high doses in the short term, and it is very inexpensive, costing pennies per milligram, so its prospects look promising,\" says Kass.
Kass说：“已经证实短期内服用大剂量叶酸是安全的，而且价格便宜，每毫克仅需数便士，所以它很有前途。”

Researchers plan further tests to determine precisely why folate protects the heart, and to determine how effective it is in not-as-high doses. But they point out that it has long been known for its role in the normal workings of the cell's principal energy source, the mitochondria, whose function is essential to maintaining healthy blood vessels.
研究者们准备进一步研究为什么叶酸能保护心脏，并确定有效剂量而不是大剂量。但是他们指出长期以来认为叶酸的功能是通过能量的供应者线粒体中起作用，是维护健康的血管必需的。

It was this evidence that led to the latest study, which, says lead investigator An Moens, M.D., suggests that folate acts as an energy reserve in the heart, \"providing much needed energy for muscle contraction, in the form of ATP, at the same time the heart is being starved for oxygen-carrying blood by a blocked artery.\"
主要研究者An Moens博士说，这个最新的研究表明叶酸在心脏中是能源贮存体，“以ATP的形式提供肌肉收缩所需要的大部分能量，同理，当供氧血管阻塞时心脏会缺血坏死。”

According to Moens, a postdoctoral cardiology research fellow at Johns Hopkins, study results showed that high-energy phosphate levels went down 43 percent in the blood of treated rats, but levels dropped by one-third more (by 66 percent) in untreated rats.
按照约翰霍普金斯大学心脏病学博士后Moens的说法，研究结果显示高能磷酸盐水平治疗组下降43%，而未治疗组下降到三分之一（降低了66%）。

\"With more fuel, the heart kept pumping even though its blood flow was reduced,\" says Moens, now a cardiologist at the University of Antwerp in Belgium. \"The smaller heart attacks seemed related to this better energy balance in the heart produced by the folate.\"
现在身为比利时安特卫普大学心脏病专家的Moens说：“即使血流量减少，如果有更多的能源，心脏泵血功能仍能保持。较小的心脏损害似乎与叶酸所致的较好的能量平衡有关。”

In the study, heart function was monitored by more than two dozen key tests, such as echocardiogram and magnetic resonance imaging, as well as by blood analysis before, during and after the heart attack, when blood flow was allowed to resume in the coronary artery that had been blocked.
在研究中，通过20多个关键实验测试心功能，比如在心脏病发作前后以及梗塞血管再通时用超声心动图、磁共振进行血流分析。

Among the team's other findings that backed up the protective effects of folate on the heart were mild, slight dips in systolic blood pressure during heart attack in treated rats, while pressure fell in untreated animals by 25 percent. Similarly, blood flow was stable in the treated group, but dropped by 40 percent in untreated animals. Post-heart attack buildup of dangerous chemicals, known as reactive oxygen species, was halved in treated rats. And fatal arrhythmias, unstable heartbeats that can immediately follow a heart attack, also went down from 36.7 percent to 8.3 percent in the supplement-fed group.
该团队还发现叶酸对心脏的支持保护效应有：治疗组老鼠在心脏病发作时收缩压轻微下降，而未治疗组下降了25%。类似的，治疗组血流量平稳，未治疗组下降了40%。心脏病发作后的不良物质活性氧浓度，治疗组较未治疗减少一半。而心脏病发作后的致死性心律失常也下降，未治疗组和叶酸添加组分别为36.7%、8.3%。

\"In future, we might just pop in an I.V., and give people high-dose folate while they are waiting for their catheterization or CT scans to search for blockages,\" says Moens.
Moens说:“将来当患者在等待导管介入或CT扫描寻找罪犯血管时，此时我们也许会静脉给予大剂量的叶酸。”

Funding for the study of folate, one of eight B vitamins, was provided by the National Institutes of Health and the Peter Belfer Laboratory Foundation, with additional support from the American Heart Association, the Belgian American Educational Foundations, as well as the University of Antwerp, Belgium.
作为八个B族维生素之一的叶酸实验基金由国立卫生研究院、Peter Belfer实验室基金提供，并得到美国心脏协会、比利时美国教育基金和比利时安特卫普大学支持。