The vitamin E-binding protein afamin increases in maternal serum during pregnancy

Abstract

BackgroundAfamin is a liver-derived plasma glycoprotein with vitamin E-binding properties and a putative function in fertility. This study evaluated serum afamin concentrations during and postpartum to uncomplicated pregnancies and investigated a potential association between afamin concentrations and pregnancy outcome.MethodsAfamin serum concentrations were measured in women with uncomplicated pregnancies in a retrospective cohort (n = 466) at different gestational ages and a prospective observational study (n = 76) in the first, second and third trimester. Furthermore, afamin was determined in the first trimester in a cross-sectional pilot study including women with preeclampsia (PE), pregnancy-induced hypertension (PIH) and women without pregnancy complications (n = 13 each). Finally, expression of afamin was investigated in human placental tissue by RT-PCR and immunohistochemistry.ResultsAfamin concentrations increased linearly almost two-fold during pregnancy in both retrospective and prospective studies in women without pregnancy complications with median afamin serum concentrations of 61.9 mg/l, 79.6 mg/l, and 98.6 mg/l in the first, second, and third trimester, respectively. After delivery, median afamin concentrations decreased to baseline values of 54.6 mg/l. In the pilot study with pregnancy complications, women with PE displayed significantly higher median afamin concentrations than did women with uncomplicated pregnancy (70.0 mg/l vs. 55.4 mg/l, P = 0.007). Expression analyses revealed no placental afamin expression at either mRNA or protein level in uncomplicated pregnancy.ConclusionA linear increase in the maternally expressed glycoprotein afamin during pregnancy may serve as basic reference for subsequent investigations of afamin in pregnancy-related disorders.

Afamin — A pleiotropic glycoprotein involved in various disease states

“…In a pilot study conducted in patients diagnosed with pregnancy complications, blood drawn at the first trimester screening from women with preeclampsia revealed significantly higher median afamin concentrations than did blood from women with uncomplicated pregnancy [37]. These findings suggest a potential role of afamin as a predictive marker for pregnancy-related disorders.…”

“…During uncomplicated pregnancy afamin increases linearly almost two-fold and drops to pre-pregnant values immediately after delivery [37]. It is therefore tempting to speculate that afamin rises during pregnancy due to changing hormonal status and subsequent hormonal regulation of the afamin gene expression in human liver.…”

Complexity of vitamin E metabolism

“…However, in body fluids with low lipoprotein concentrations, such as follicular fluids, an alternative carrier protein for vitamin E, namely afamin, has been described [87][88][89] . Afamin is a liver-derived plasma glycoprotein and a member of the albumin protein family [90][91][92] ; therefore it is also called α-albumin [93] . Afamin is partly (13%) bound to plasma lipoproteins [88] , but circulates mostly in free form.…”

“…Originally, vitamin E was discovered as a resorption-gestations factor in female rats [2,94] . Afamin was therefore suggested as playing a role in female fertility [92] , and indeed it has been shown to bind vitamin E and to increase in maternal serum during pregnancy [92] . Yet the precise role of afamin in pregnancy or for infertility is still not known [95] .…”

“…Yet the precise role of afamin in pregnancy or for infertility is still not known [95] . On the one hand, afamin increases during pregnancy and decreases after childbirth to baseline levels, but on the other hand, a pilot study of Hubalek et al [92] showed that women suffering from pregnancy complications had significantly higher median afamin concentrations than women with uncomplicated pregnancy. In addition to being found in follicular fluids, afamin has also been detected in other extravascular fluids, such as cerebrospinal fluids, although the concentration is tenfold lower than in follicular fluids [88] .…”