Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women
Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women
复制标题
DOI：
10.1093/jn/136.1.189
复制
发表时间：
2006-01-01
影响因子：
4.2
通讯作者：
Ulrich, CM
中科院分区：
文献类型：
--
作者：
Troen, AM;Mitchell, B;Ulrich, CM
叶酸(FA)补充剂和食物强化被用来预防神经管缺陷和降低血浆同型半胱氨酸。通过接触食物强化和维生素补充剂的使用，美国和其他地方的大量人口有前所未有的高FA摄入量。我们在105名健康的绝经后妇女中评估了叶酸和FA的饮食和补充摄入量与免疫功能指标--自然杀伤细胞(NK)细胞毒性的关系。在低叶酸饮食(233mUg/d)的妇女中，那些使用含FA补充剂的妇女具有明显更强的NK细胞毒性(P=0.01)。然而，与低叶酸饮食和不补充叶酸饮食的人相比，每天补充叶酸400 mg/d的人NK细胞毒性降低(P=0.02)。受此观察的启发，我们评估了血浆中未代谢的FA的存在作为过量FA的生化标记物。禁食参与者78%的血浆样本中检测到未代谢的叶酸。我们发现，血浆中未代谢的FA的存在与NK细胞杀伤活性呈负相关。在可检测到叶酸的女性中，NK细胞毒性类似于低23%(P=0.04)。这种相反的关系在60岁的女性中更明显，并且随着非代谢脂肪酸浓度的增加而更加明显(P-趋势=0.002)。由于许多国家的FA摄入量增加，我们的研究结果强调了长期高FA摄入量对免疫功能和健康的影响的进一步研究的必要性。
Folic acid (FA) supplements and food fortification are used to prevent neural tube defects and to lower plasma homocysteine. Through exposure to food fortification and vitamin supplement use, large populations in the United States and elsewhere have an unprecedented high FA intake. We evaluated dietary and supplemental intakes of folate and FA in relation to an index of immune function, natural killer cell (NK) cytotoxicity, among 105 healthy, postmenopausal women. Among women with a diet low in folate (< 233 mu g/d), those who used FA-containing supplements had significantly greater NK cytotoxicity (P = 0.01). However, those who consumed a folate-rich diet and in addition used FA supplements > 400 mu g/d had reduced NK cytotoxicity compared with those consuming a low-folate diet and no supplements (P = 0.02). Prompted by this observation, we assessed the presence of unmetabolized FA in plasma as a biochemical marker of excess FA. Unmetabolized folic acid was detected in 78% of plasma samples from fasting participants. We found an inverse relation between the presence of unmetabolized FA in plasma and NK cytotoxicity. NK cytotoxicity was similar to 23% lower among women with detectable folic acid (P = 0.04). This inverse relation was stronger among women >= 60 y old and more pronounced with increasing unmetabolized FA concentrations (P-trend = 0.002). Because of the increased intake of FA in many countries, our findings highlight the need for further studies on the effect of long-term high FA intake on immune function and health.