Hyperhomocysteinemia is not sufficient to cause preeclampsia in an animal model: the importance of folate intake

Association of methylenetetrahydrofolate reductase C677T polymorphism with the pre-eclampsia risk in Hakka pregnant women in Southern China

The aim of this study is to clarify the possible association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and pre-eclampsia in Hakka pregnant women in southern China. Pre-eclampsia and normal pregnant women were consecutively collected and MTHFR C677T genotypes were determined by the DNA sequencing method. One hundred and thirteen pre-eclampsia patients were CC homozygote (113 of 191, 59.2%), 68 of 191 (35.6%) were CT heterozygote, and 10 of 191 (5.2%) were TT homozygote, with the frequency of the T allele equal to 0.77. This is in comparison with the normal control group where 106 of 202 (52.5%) were CC homozygote, 83 of 202 (41.1%) were CT heterozygote, and 13 of 202 (6.4%) were TT homozygote, with the frequency of the T allele equal to 0.27. No statistically significant differences were observed in genotype or allele frequencies between the pre-eclampsia and normal control for the C677T polymorphism of MTHFR gene (p > .05). The findings of this study suggest that polymorphisms of MTHFR C677T genes were not associated with pre-eclampsia in Hakka pregnant women from southern China, but additional studies are necessary to explore the mechanisms involving it.

Increased homocysteine levels exist in women with preeclampsia from early pregnancy

OBJECTIVE

The present prospective study examines the levels of maternal plasma folate, vitamin B12 and homocysteine in normotensive control (NC) women and women with preeclampsia (PE) from early pregnancy till delivery.

METHODS

The present study includes 126 NC and 62 PE women. Maternal blood was collected at 3 time points during pregnancy (T1 = 16th-20th weeks, T2 = 26th-30th weeks and T3 = at delivery). Levels of folate, vitamin B12 and homocysteine were estimated by the chemiluminescent microparticle immunoassay technology.

RESULTS

Maternal plasma folate levels were similar between NC and PE women at all the time points across gestation. Maternal plasma vitamin B12 levels were significantly higher in PE (p < 0.05) as compared with NC at T2. Maternal plasma homocysteine levels were higher in PE as compared with NC at all the time points, i.e. T1, T2 (p < 0.05 for both) and T3 (p < 0.01).

CONCLUSION

Our results indicate that higher homocysteine levels exist in women with PE from early pregnancy and continue till delivery.

Full-length human placental sFlt-1-e15a isoform induces distinct maternal phenotypes of preeclampsia in mice

OBJECTIVE

Most anti-angiogenic preeclampsia models in rodents utilized the overexpression of a truncated soluble fms-like tyrosine kinase-1 (sFlt-1) not expressed in any species. Other limitations of mouse preeclampsia models included stressful blood pressure measurements and the lack of postpartum monitoring. We aimed to 1) develop a mouse model of preeclampsia by administering the most abundant human placental sFlt-1 isoform (hsFlt-1-e15a) in preeclampsia; 2) determine blood pressures in non-stressed conditions; and 3) develop a survival surgery that enables the collection of fetuses and placentas and postpartum (PP) monitoring.

METHODS

Pregnancy status of CD-1 mice was evaluated with high-frequency ultrasound on gestational days (GD) 6 and 7. Telemetry catheters were implanted in the carotid artery on GD7, and their positions were verified by ultrasound on GD13. Mice were injected through tail-vein with adenoviruses expressing hsFlt-1-e15a (n = 11) or green fluorescent protein (GFP; n = 9) on GD8/GD11. Placentas and pups were delivered by cesarean section on GD18 allowing PP monitoring. Urine samples were collected with cystocentesis on GD6/GD7, GD13, GD18, and PPD8, and albumin/creatinine ratios were determined. GFP and hsFlt-1-e15a expression profiles were determined by qRT-PCR. Aortic ring assays were performed to assess the effect of hsFlt-1-e15a on endothelia.

RESULTS

Ultrasound predicted pregnancy on GD7 in 97% of cases. Cesarean section survival rate was 100%. Mean arterial blood pressure was higher in hsFlt-1-e15a-treated than in GFP-treated mice (∆MAP = 13.2 mmHg, p = 0.00107; GD18). Focal glomerular changes were found in hsFlt-1-e15a -treated mice, which had higher urine albumin/creatinine ratios than controls (109.3 ± 51.7 μg/mg vs. 19.3 ± 5.6 μg/mg, p = 4.4 x 10(-2); GD18). Aortic ring assays showed a 46% lesser microvessel outgrowth in hsFlt-1-e15a-treated than in GFP-treated mice (p = 1.2 x 10(-2)). Placental and fetal weights did not differ between the groups. One mouse with liver disease developed early-onset preeclampsia-like symptoms with intrauterine growth restriction (IUGR).

CONCLUSIONS

A mouse model of late-onset preeclampsia was developed with the overexpression of hsFlt-1-e15a, verifying the in vivo pathologic effects of this primate-specific, predominant placental sFlt-1 isoform. HsFlt-1-e15a induced early-onset preeclampsia-like symptoms associated with IUGR in a mouse with a liver disease. Our findings support that hsFlt-1-e15a is central to the terminal pathway of preeclampsia, and it can induce the full spectrum of symptoms in this obstetrical syndrome.

Preventive effects of folic acid supplementation on adverse maternal and fetal outcomes

Although there is accumulating evidence regarding the additional protective effect of folic acid against adverse pregnancy outcomes other than neural tube defects, these effects have not been elucidated in detail. We evaluated whether folic acid supplementation is associated with favorable maternal and fetal outcomes. This was a secondary analysis of 215 pregnant women who were enrolled in our prior study. With additional data from telephone interviews regarding prenatal folic acid supplementation, existing demographic, maternal and fetal data were statistically analyzed. The concentration of folic acid in maternal blood was significantly higher following folic acid supplementation (24.6 ng/mL vs.11.8 ng/mL). In contrast, homocysteine level in maternal blood decreased with folic acid supplementation (5.5 µmol/mL vs. 6.8 µmol/mL). The rates of both preeclampsia (odds ratio [OR], 0.27; 95% confidence interval [CI], 0.09–0.76) and small for gestational age (SGA; 9.2% vs. 20.0%; OR, 0.42; 95% CI, 0.18–0.99) were lower in the folic acid supplementation group than those in the control group. Other pregnancy outcomes had no association with folic acid supplementation. The findings indicate that folic acid supplementation may help to prevent preeclampsia and SGA. Further studies are warranted to elucidate the favorable effects of folic acid supplementation on pregnancy outcomes.

Novel role of the renin-angiotensin system in preeclampsia superimposed on chronic hypertension and the effects of exercise in a mouse model

Gestational hypertensive disorders, such as preeclampsia, affect 6% to 8% of all pregnancies in North America, and they are the leading cause of maternal mortality in industrialized countries, accounting for 16% of deaths. Women with hypertension have an increased risk (15% to 25%) of developing preeclampsia. Our aim was to investigate the mechanisms implicated in preeclampsia superimposed on chronic hypertension and in the protective effects of exercise in a mouse model. Female mice overexpressing human angiotensinogen and human renin were used as a model of preeclampsia superimposed on chronic hypertension. In the trained group, mothers were placed in cages with access to a wheel before mating, and they remained within these throughout gestation. Blood pressure was measured by telemetry. We found that angiotensin II type I receptor was increased, whereas the Mas receptor was decreased in the placenta and the aorta of pregnant sedentary transgenic mice. This would produce a decrease in angiotensin-(1-7) effects in favor of angiotensin II. Supporting the functional contribution of this modulation, we found that the prevention of most pathological features in trained transgenic mice was associated with a normalization of placental angiotensin II type 1 and Mas receptors and an increase in aortic Mas receptor. We also found reduced circulating and placental soluble Fms-like tyrosine kinase-1 in trained transgenic mice compared with sedentary mice. This study demonstrates that modulation of the renin-angiotensin system is a key mechanism in the development of preeclampsia superimposed on chronic hypertension, which can be altered by exercise training to prevent disease features in an animal model.

Molecular genetics of preeclampsia and HELLP syndrome - a review

Preeclampsia is characterised by new onset hypertension and proteinuria and is a major obstetrical problem for both mother and foetus. Haemolysis elevated liver enzymes and low platelets (HELLP) syndrome is an obstetrical emergency and most cases occur in the presence of preeclampsia. Preeclampsia and HELLP are complicated syndromes with a wide variety in severity of clinical symptoms and gestational age at onset. The pathophysiology depends not only on periconceptional conditions and the foetal and placental genotype, but also on the capability of the maternal system to deal with pregnancy. Genetically, preeclampsia is a complex disorder and despite numerous efforts no clear mode of inheritance has been established. A minor fraction of HELLP cases is caused by foetal homozygous LCHAD deficiency, but for most cases the genetic background has not been elucidated yet. At least 178 genes have been described in relation to preeclampsia or HELLP syndrome. Confined placental mosaicism (CPM) is documented to cause early onset preeclampsia in some cases; the overall contribution of CPM to the occurrence of preeclampsia has not been adequately investigated yet. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Association between oxidized LDL and folate during pregnancy

High levels of oxidized low-density lipoprotein (ox-LDL) during pregnancy are a risk factor for preeclampsia. Ox-LDL levels might be affected by folate and total homocysteine (tHcy) levels because of their effects on oxygen free radicals. The relationships between ox-LDL and folate and tHcy during pregnancy, however, remain unclear. The present study investigated whether serum folate levels and plasma tHcy levels were associated with plasma ox-LDL levels in pregnant women. A sample of 137 healthy subjects with singleton pregnancies (age 30.3 ± 4.5 years) was recruited from a prenatal clinic in metropolitan Tokyo between June and October 2008. Their levels of plasma ox-LDL, plasma tHcy, and serum folate were measured, and lifestyle variables were obtained using a questionnaire. Dietary intake was assessed by means of a validated self-administered diet history questionnaire. A negative correlation between plasma ox-LDL levels and serum folate levels was found (r(s) = -.218, p =.011). However, there was no association between plasma ox-LDL levels and plasma tHcy levels (r(s) = .055, p = .525). The mean of the logarithmic ox-LDL levels was significantly lower among the participants taking folic acid-containing supplements regularly than among those who were not, after adjusting for confounding factors (p = .024). Serum folate levels and folic acid supplementation might be associated with plasma ox-LDL levels, independent of tHcy levels. The association observed between ox-LDL and folate can be used as evidence for dietary instruction by prenatal care providers.

Exercise training can attenuate preeclampsia-like features in an animal model

OBJECTIVE

Exercise training benefits have been widely investigated and used as alternative treatment for different pathological conditions. Since preeclampsia is a severe pregnancy-associated disease for which no treatment is available, our aim was to investigate the protective role of exercise training on pregnancy outcome using a mouse model of the disease.

METHODS

We used transgenic female mice overexpressing human angiotensinogen, which develop preeclampsia when mated with human renin-overexpressing males. Females were placed in exercise cages 4 weeks prior to mating, and remained in these throughout gestation. Blood pressure was measured by telemetry, and proteinuria was quantified by ELISA. Placentas were assessed by histology and immunohistochemistry, whereas vascular endothelial growth factor was measured by real-time PCR and immunoblot. Endothelial function was assessed in isolated mesenteric arteries.

RESULTS

Conversely to sedentary transgenic females (131.20 ± 4.08 mmHg), trained dam's mean arterial pressure was no longer different from normal mice at the end of gestation (117.5 ± 10.6 vs. 112.3 ± 5.5 mmHg). Proteinuria observed in transgenic dams (3.364 ± 1.62 μg/mg) was absent in trained mice (0.894 ± 0.43 μg/mg). Placental disease and cardiac hypertrophy were also normalized, whereas vascular reactivity was significantly ameliorated. Furthermore, placental vascular endothelial growth factor was normalized in trained transgenic mice.

CONCLUSIONS

To our knowledge, we are the first to clearly demonstrate that exercise training both before and during gestation can reduce preeclampsia features in a mouse model. Consequently, women at risk for this disease could benefit from exercise training to protect themselves and their future fetuses.

Pre-eclampsia: connecting angiogenic and metabolic pathways

Pre-eclampsia is a hypertensive disease of pregnancy with a worldwide incidence of 5-8%. This review focuses on recent developments in pre-eclampsia research related to angiogenesis and metabolism. We first address the 'angiogenic imbalance' theory, which hypothesizes that pre-eclampsia results from an imbalance of factors that promote or antagonize angiogenesis, such as soluble fms-like tyrosine kinase (sFlt1), 2-methoxyestradiol (2-ME) and catechol-O-methyltransferase (COMT). Next, we analyze the association between pre-eclampsia and dysfunctional metabolism of both homocysteine and placental glycogen. We hope that illuminating some of the various connections existing between angiogenesis and metabolism in pre-eclampsia will facilitate the update or reconsideration of old models of pathogenesis.