Betaine: a key modulator of one-carbon metabolism and homocysteine status
Betaine: a key modulator of one-carbon metabolism and homocysteine status
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DOI：
10.1515/cclm.2005.187
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发表时间：
2005-01-01
影响因子：
6.8
通讯作者：
Hustad, S
中科院分区：
文献类型：
--
作者：
Ueland, PM;Holm, PI;Hustad, S
甜菜碱在甜菜碱-同型半胱氨酸甲基转移酶的催化下，在同型半胱氨酸转化为蛋氨酸的反应中充当甲基供体。多年来，它一直被用于降低同型半胱氨酸尿症患者的血浆总同型半胱氨酸 (tHcy) 浓度，最近被证明可以降低健康受试者的禁食，特别是蛋氨酸负荷后 (PML) tHcy。甜菜碱在血浆中的浓度约为 30 μmol/L；个体之间的差异为 10 倍（从 9 至 90 μmol/L），但个体内变异性很小。主要决定因素是血浆中的胆碱、二甲基甘氨酸和叶酸、叶酸摄入量和性别。最近的研究表明，与维生素 B 和叶酸相比，血浆甜菜碱是 PML tHcy 更强的决定因素。补充 B 族维生素后，甜菜碱-PML tHcy 关系会减弱，并且在叶酸水平较低的受试者中最为明显。甜菜碱与空腹 tHcy 的关联较弱（与 PML tHcy 相比），而且这种关联在叶酸水平较低的受试者中最为明显。怀孕期间，血浆甜菜碱含量会下降，直至妊娠第 20 周，此后保持稳定。从妊娠第 20 周起，空腹 tHcy 与血浆甜菜碱呈强烈负相关，并且甜菜碱成为比叶酸更强的空腹 tHcy 预测因子。 总之，甜菜碱状态是个体生化组成的一个组成部分，对一碳代谢有影响。应在与同型半胱氨酸和叶酸代谢改变相关的病理学中研究甜菜碱状态，包括心血管疾病、癌症和神经管缺陷。
Betaine serves as a methyl donor in a reaction converting homocysteine to methionine, catalysed by the enzyme betaine-homocysteine methyltransferase. It has been used for years to lower the concentration of plasma total homocysteine (tHcy) in patients with homocystinuria, and has recently been shown to reduce fasting and in particular post-methionine load (PML) tHcy in healthy subjects.Betaine exists in plasma at concentrations of about 30 mu mol/L; it varies 10-fold (from 9 to 90 mu mol/L) between individuals, but the intra-individual variability is small. Major determinants are choline, dimethylglycine and folate in plasma, folic acid intake and gender.Recent studies have demonstrated that plasma betaine is a stronger determinant of PML tHcy than are vitamin B, and folate. The betaine-PML tHcy relationship is attenuated after supplementation with B-vitamins, and is most pronounced in subjects with low folate. Betaine shows a weaker association with fasting tHcy (than with PML tHcy), and also this association is most pronounced in subjects with low folate. In pregnancy, plasma betaine declines until gestational week 20, and thereafter remains constant. From gestational week 20 onwards, fasting tHcy shows a strong inverse association with plasma betaine, and betaine becomes a stronger predictor than folate of fasting tHcy.To conclude, betaine status is a component of an individual's biochemical make-up with ramifications to one-carbon metabolism. Betaine status should be investigated in pathologies related to altered metabolism of homocysteine and folate, including cardiovascular disease, cancer and neural tube defects.