Padmanabhan R, Shafiullah M, Benedict S, Nagelkerke N
Department of Anatomy, Faculty of Medicine and Health Sciences, UAE University, PO Box 17666, Al Ain, United Arab Emirates.
Eur J Nutr. 2006 Sep;45(6):311-9. doi: 10.1007/s00394-006-0600-4. Epub 2006 May 13.
Neural tube defects (NTD) are mainly of multifactorial origin. Maternal treatment with valproic acid (VPA) during pregnancy induces NTD in susceptible fetuses. Elevated levels of homocysteine are observed in pregnancies with NTD. The mechanism by which homocysteine might cause NTD is unknown.
The aim of this study was to determine if homocystine would augment VPA-induced exencephaly in an experimental model.
Groups of mice were injected (IP) on gestational day 8 (GD) with a single dose of 75 mg/kg of L: -Homocystine (HC) or a proportionate volume of saline, followed by a single dose of 600 mg/kg of VPA or an equal volume of saline. In a second experiment, mice were treated with a daily dose of 75 mg/kg of HC or an equal volume of saline (IP) from GD 5 and continued through GD 10. These animals had a single exposure to 600 mg/kg of VPA or saline (IP) on GD 8. All animals were killed by cervical dislocation on GD 18. Plasma homocysteine, folate and vitamin B12 were determined on GD 8 and GD 10 from single and multiple dose groups of mice, respectively, from additional experiments.
The VPA and HC+VPA induced significantly higher rates of embryonic resorption and intrauterine growth retardation (IUGR) than HC or saline alone. HC + VPA groups had significantly more numerous fetuses with severe IUGR than HC alone or VPA alone groups. Both single and multiple doses of HC augmented VPA-induced reduction in fetal body weight. Successive doses of HC did not augment the rate of IUGR more significantly than a single dose of HC. Incidence of exencephaly was significantly enhanced in the HC + VPA groups compared to that in the HC or VPA alone groups. HC alone was not teratogenic. Plasma homocysteine levels increased several fold both in HC and HC + VPA groups and the increase was not particularly more marked in multiple dose groups than in the single dose groups. VPA did not elevate homocysteine concentration. Both FA and vitamin B12 concentrations were reduced by VPA, HC and HC + VPA, but HC and VPA when combined did not produce an additive effect on vitamin levels.
These data indicate that HC and VPA interact in neurulation stage embryos, affect fundamental processes of closure of the neural tube and lead to enhanced incidence of NTD.
神经管缺陷（NTD）主要源于多因素。孕期母体使用丙戊酸（VPA）会导致易感胎儿出现NTD。在患有NTD的妊娠中观察到同型半胱氨酸水平升高。同型半胱氨酸可能导致NTD的机制尚不清楚。
本研究的目的是确定在实验模型中同型胱氨酸是否会增加VPA诱导的无脑畸形。
在妊娠第8天（GD）给小鼠腹腔注射（IP）单剂量75mg/kg的L-同型胱氨酸（HC）或等体积的生理盐水，随后腹腔注射单剂量600mg/kg的VPA或等体积的生理盐水。在第二个实验中，从GD 5开始每天给小鼠腹腔注射75mg/kg的HC或等体积的生理盐水，持续至GD 10。这些动物在GD 8时单次暴露于600mg/kg的VPA或生理盐水（IP）。所有动物在GD 18时通过颈椎脱臼处死。分别在另外的实验中，从单次和多次给药组的小鼠中，在GD 8和GD 10测定血浆同型半胱氨酸、叶酸和维生素B12。
与单独使用HC或生理盐水相比，VPA和HC + VPA诱导的胚胎吸收和宫内生长迟缓（IUGR）发生率显著更高。HC + VPA组中患有严重IUGR 的胎儿数量明显多于单独使用HC或单独使用VPA的组。单剂量和多剂量的HC均增加了VPA诱导的胎儿体重减轻。连续给予HC并没有比单剂量HC更显著地增加IUGR的发生率。与单独使用HC或VPA的组相比，HC + VPA组中无脑畸形的发生率显著增加。单独使用HC没有致畸作用。HC组和HC + VPA组的血浆同型半胱氨酸水平均增加了几倍，且多剂量组的增加并不比单剂量组更明显。VPA没有提高同型半胱氨酸浓度。VPA、HC和HC + VPA均降低了叶酸和维生素B12的浓度，但HC和VPA联合使用时对维生素水平没有产生相加作用。
这些数据表明，HC和VPA在神经胚形成阶段的胚胎中相互作用，影响神经管闭合的基本过程，并导致NTD发生率增加。
