Department of Family Medicine, Case Western Reserve University School of Medicine at MetroHealth Medical Center, Cleveland, OH, USA.
Am J Clin Nutr. 2010 Feb;91(2):357-65. doi: 10.3945/ajcn.2009.28457. Epub 2009 Nov 25.
Hyperhomocysteinemia during pregnancy, which is a consequence of perturbations in methionine and/or folate metabolism, has been implicated in adverse outcomes such as neural tube defects, preeclampsia, spontaneous abortion, and premature delivery. The adaptive changes in methionine metabolism during pregnancy in humans have not been determined.
Our objective was to examine the kinetics of methionine and its rate of transsulfuration and transmethylation in healthy women with advancing gestation.
The whole-body rate of appearance (Ra) of methionine and phenylalanine was measured in healthy pregnant women during the first (n = 10), second (n = 5), and third (n = 10) trimesters of pregnancy. These data were compared with those for nonpregnant women (n = 8). Tracers [1-(13)C]methionine, [C(2)H(3)]methionine, and [(2)H(5)]phenylalanine were administered as prime-constant rate infusions. The effect of enteral high-protein, mixed-nutrient load on tracer-determined variables was also examined.
In pregnant women, the Ra of phenylalanine was significantly (P < 0.05) lower in the first trimester than in the second and third trimesters and was significantly lower than that in nonpregnant women. A linear positive correlation was evident between gestational age and phenylalanine Ra. The fractional rate and total rate of transsulfuration of methionine was significantly (P < 0.05) higher during the first trimester, whereas the rate of transmethylation was higher during the third trimester. Plasma concentrations of total cysteine and homocysteine were lower during pregnancy.
Uncomplicated pregnancy in humans is associated with a higher rate of transsulfuration early in gestation and a higher rate of transmethylation of methionine in late gestation. These data may have implications for understanding the role of methionine and homocysteine in complications of pregnancy and for the nutritional care of pregnant women.
怀孕期间的高同型半胱氨酸血症是由于蛋氨酸和/或叶酸代谢紊乱引起的，与神经管缺陷、子痫前期、自然流产和早产等不良后果有关。人类怀孕期间蛋氨酸代谢的适应性变化尚未确定。
我们的目的是研究健康孕妇妊娠进展时蛋氨酸及其转硫和转甲基的动力学。
在妊娠第一（n = 10）、第二（n = 5）和第三（n = 10）期，我们测量了健康孕妇的全身蛋氨酸和苯丙氨酸出现率（Ra）。将这些数据与非孕妇（n = 8）的数据进行比较。作为恒速输注给予示踪剂[1-(13)C]蛋氨酸、[C(2)H(3)]蛋氨酸和[(2)H(5)]苯丙氨酸。还检查了肠内高蛋白、混合营养素负荷对示踪剂测定变量的影响。
在孕妇中，第一孕期的苯丙氨酸 Ra 明显（P < 0.05）低于第二和第三孕期，明显低于非孕妇。妊娠年龄与苯丙氨酸 Ra 呈线性正相关。蛋氨酸转硫的分数率和总率在第一孕期明显升高（P < 0.05），而转甲基率在第三孕期升高。血浆总半胱氨酸和同型半胱氨酸浓度在怀孕期间较低。
人类妊娠无并发症与妊娠早期转硫率较高和妊娠晚期蛋氨酸转甲基率较高有关。这些数据可能对理解蛋氨酸和同型半胱氨酸在妊娠并发症中的作用以及孕妇的营养护理具有重要意义。
