Endothelial dysfunction in preeclampsia. Increased homocysteine and decreased nitric oxide levels

Endothelial dysfunction underlies the pathogenesis of preeclampsia, but its mechanism has not yet been completely understood. Elevated oxygen free radicals may partially explain the endothelial cell damage. In this study, we have aimed to measure homocysteine (Hcy) and nitric oxide (NO) levels as endothelial dysfunction markers in preeclamptic women. Nineteen preeclamptic (33.9 +/- 1.4 weeks) and 15 gestational-age-matched normal pregnant women (35.5 +/- 0.7 weeks) were included in the study. Mean NO level was significantly lower (p < 0.001) and mean Hcy level was significantly higher (p < 0.001) in the preeclamptic group. Elevated Hcy and oxygen free radical levels could decrease NO levels due to the reaction with each other and reduced NO may increase blood pressure and ischemia in preeclamptic patients. We have concluded that increased Hcy and oxygen free radical levels, and decreased NO levels are closely associated with preeclampsia-related endothelial dysfunction.     

Calcium, nitric oxide, and preeclampsia

A relationship between calcium dietary intake and incidence of preeclampsia was proposed. In the Andean Ecuadorian population, the average calcium intake, evaluated by a 24 hours dietary recall range between 52.3% of the US RDA to 77%. The calcium intake in women with preeclampsia was significantly lower in relation with normal pregnant women. Three prospective, randomized, double-blind, placebo-controlled clinical trials to investigate the effect of calcium supplementation (2 g/day of elemental calcium) in the incidence of pregnancy-induced hypertension and preeclampsia were conduced between 1984 and 1995. All the subjects included were nulliparous, younger that 25 years old, first prenatal visit before 24 weeks' gestation, residency in Quito, and normotensives. These clinical trials showed a risk reduction in pregnancy induced hypertension and preeclampsia in the calcium group. Calcium supplementation was associated with an increase in the serum ionized calcium concentrations. Moreover, women with preeclampsia showed a significant decrease in the levels of the serum ionized calcium. Ionic calcium is crucial for the synthesis of vasoactive substances in the endothelium as prostacyclin and nitric oxide. Recent results suggest that an alteration in the action of NO may be related to a high inactivation by free radical superoxide, secondary to an inflammatory process.     

Evaluation of asymmetric dimethylarginine,nitric oxide levels and associated independent variables in obese and lean patients with polycystic ovarian syndrome

Objective.?To evaluate the asymmetric dimethylarginine (ADMA) and nitric oxide (NO) levels in obese and lean patients with polycystic ovarian syndrome (PCOS) and find out their relation with hormonal and metabolic parameters.

Methods.?Twenty-two obese, 18 lean patients with PCOS and 11 obese, 24 lean healthy control patients were enrolled prospectively. Plasma ADMA and NO levels and arginine/ADMA ratio were evaluated on 3rd day of menstrual cycle after at least 10?h overnight fasting.

Results.?Plasma ADMA, NO levels and arginine/ADMA ratio were similar in the groups. ADMA level did not correlate with the hormonal and metabolic parameters in patients with PCOS. However, NO correlated inversely with fasting insulin (r?=??0.353, p?=?0.041) and homeostasis model of insulin resistance (HOMA-IR) (r?=??0.379, p?=?0.027). Arginine/ADMA ratio also correlated inversely with fasting insulin (r?=??0.339, p?=?0.050). In multinomial regression analysis the risk of low NO was associated independently with high fasting insulin (OR?=?1.19, 95% CI 1.001–1.42, p?=?0.049) and high HOMA-IR in patients with PCOS (OR?=?2.26, 95% CI 1.03–4.98, p?=?0.042).

Conclusions.?Insulin resistance may be the underlying mechanism of endothelial dysfunction through NO pathway in PCOS.     

Association of endothelial nitric oxide synthase gene G894T polymorphism and serum nitric oxide levels in patients with preeclampsia and gestational hypertension

Objective: Pregnancy-induced hypertension is one of the most important cause of maternal-fetal morbidity and mortality. Pregnancy-related hypertensive disorders are usually associated with diminished nitric oxide (NO) levels. We aimed to evaluate the role of serum NO levels and eNOS gene G894T polymorphism on hypertensive disorders of pregnancy.

Methods: Eighty patients with gestational hypertension or preeclampsia, and 80 healthy pregnants were enrolled to analyze serum NO levels and G894T polymorphism of the eNOS gene. NO level was analyzed by high-performance liquid chromatography (HPLC) method. The G894T polymorphism of the eNOS gene was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

Results: There was no significant difference between groups in terms of G894T/eNOS genotype and allele frequencies (p?>?0.05). Serum NO levels were significantly lower in the patients group. In the control group, subjects with thymine-thymine (TT) genotype had significantly lower NO levels when compared to subjects with guanine-guanine (GG) or guanine-thymine (GT) genotype (p?Conclusions: We failed to demonstrate an association between eNOS gene G894T polymorphism and serum NO levels in patients with pregnancy-induced hypertensive disorders. We established a relation between pregnancy-induced hypertension and low NO levels.     

Endothelial nitric oxide synthase polymorphism in preeclampsia

OBJECTIVE: We wished to determine whether genetic variability in the gene encoding endothelial nitric oxide synthase (eNOS) modifies individual susceptibility to the development of preeclampsia. METHODS: The study involved 132 preeclamptic and 113 healthy control pregnant women who were genotyped for the Glu298Asp polymorphism in the eNOS gene. Chi(2) analysis was used to assess genotype and allele frequency differences between preeclamptic women and controls. RESULTS: A statistically similar allelic distribution of eNOS Glu298Asp polymorphism was observed in the two groups, with the frequency of the variant G allele being 74.6% in the preeclampsia group and 67.7% in the control group (P = .091; odds ratio 1.40, 95% confidence interval 0.95, 2.01). Accordingly, the genotype distribution of the NOS polymorphism in the preeclamptic and control groups was found to be similar (P = .233). CONCLUSION: These genotype data in subjects from eastern Finland were not suggestive of an important contribution of the Glu298Asp polymorphism in the NOS gene on preeclampsia across populations. However, the observed association between the G allele and disease risk, of borderline significance, may imply that other polymorphism(s) in the gene may modify disease risk.     

内源性一氧化氮合酶抑制物与子痫前期关系的研究

目的:探讨子痫前期患者血浆内源性一氧化氮合酶抑制物-非对称性二甲基精氨酸(asymmetric dimethylarginine,ADMA)及胎盘内皮性一氧化氮合酶(endothelial nitricoxide synthase,eNOS)的表达与子痫前期的关系。方法:2004年1月至2005年1月广州医学院第三附属医院住院分娩的子痫前期孕妇30例,正常晚期妊娠10例,早孕12例。用高效液相色谱法(HPLC)测定血浆ADMA,免疫组化法检测胎盘组织中eNOS。结果:子痫前期组ADMA水平明显高于正常晚期妊娠组,分别为17.97±7.25μg/ml和10.27±1.67μg/ml,两组差异有统计学意义(P<0.01)。而子痫前期组胎盘eNOS表达则明显低于正常晚期妊娠组,两组差异有统计学意义(P<0.05)。结论:子痫前期患者体内eNOS抑制物ADMA升高,胎盘eNOS活性下降,提示ADMA作为eNOS的抑制调节因子在子痫前期病理生理改变中可能起重要作用。     

Association of the missense Glu298Asp variant of the endothelial nitric oxide synthase gene with severe preeclampsia

OBJECTIVES: A large number of studies suggest that abnormalities in nitric oxide (NO) synthesis may contribute to the development of preeclampsia. We recently identified a variant within exon 7 of the endothelial NO synthase (eNOS) gene: G to T conversion at nucleotide position 894 resulting in replacement of glutamic acid with aspartic acid at codon 298 (Glu298Asp). We analyzed the association between the Glu298Asp eNOS gene variant and preeclampsia. STUDY DESIGN: The study included 152 preeclampsia patients (35 mild, 80 severe, and 37 superimposed) and 170 control subjects. Screening for the Glu298Asp eNOS gene variant was carried out by analysis of polymerase chain reaction-restriction fragment length polymorphism. RESULTS: The frequency of the Glu298Asp variant was significantly higher in the severe preeclampsia group (28.8%) than in the control (14.1%; p <. 01), superimposed preeclampsia (8.1%; p <.01), and mild preeclampsia (11.4%; p <.01) groups. CONCLUSIONS: We conclude that the presence of the Glu298Asp eNOS gene could be a marker of increased risk of developing severe preeclampsia.     

Asymmetric dimethylarginine,an endogenous inhibitor of nitric oxide synthase,in maternal and fetal circulation

Pronounced dilation of the maternal vasculature occurs during normal pregnancy. Likewise, low resistance characterizes the fetoplacental circulation. Nitric oxide released by endothelial cells is a potent vasodilator known to be a key modulator of both maternal and fetal vascular tone. However, the mechanisms underlying the maternal circulatory adaptations and the low resistance of the fetal circulation remain unknown. The aim of the present study was to compare levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in the maternal and fetal circulations.High performance liquid chromatography was used to measure asymmetric ADMA in the maternal and umbilical venous plasma.Plasma ADMA levels during the first trimester were 0.29 +/- 0.05, the third trimester before term 0.29 +/- 0.05, and at term 0.32 +/- 0.05 nmol/mL, which were significantly (P <.05) lower than the levels measured in nonpregnant women (0.41 +/- 0.06 nmol/mL). By contrast, ADMA levels in umbilical venous plasma averaged 1.02 +/- 0.18 nmol/mL, significantly (P <.005) higher than maternal levels. Unlike ADMA, levels of plasma L-arginine, the nitric oxide precursor, did not significantly differ among nonpregnant and pregnant women and the fetus.During pregnancy, maternal hemodynamics are modulated, at least in part, by a reduction in ADMA. Conversely, the low resistance to umbilical blood flow is maintained despite substantially higher fetal ADMA levels. Thus, the predominant mechanisms regulating the maternal and fetal circulation apparently differ.     

Cerebrospinal fluid nitric oxide level changes in preeclampsia

OBJECTIVE: The purpose of this study was to determine the level of nitric oxide (NO) metabolites, nitrite and nitrate in human cerebrospinal fluid (CSF) and serum and to assess whether there is any relationship among CSF, serum nitrate-nitrite levels and preeclampsia. STUDY DESIGN: Twenty-one preeclamptic and 27 healthy pregnant women as control group who underwent cesarean section (C/S) were included in the study. Before administering local anesthetic for spinal anesthesia, 2 ml CSF and 4 ml venous blood sample were taken. CSF and serum total nitrite, direct nitrite and nitrate levels were determined spectrophotometrically. RESULTS: CSF total nitrite, direct nitrite and nitrate levels were significantly different between the two groups (21.00+/-1.68, 8.28+/-0.89 and 12.71+/-1.08 micromol/l, respectively versus 15.53+/-1.49, 5.57+/-0.39 and 9.96+/-1.45 micromol/l, respectively, P<0.05). Significantly higher serum nitrate level was found (31.84+/-2.31 micromol/l) in the control group compared to the preeclamptic group serum nitrate level (25.06+/-2.02 micromol/l). Statistical comparisons were performed by the Mann-Whitney U-test. CONCLUSION: CSF-NO is significantly higher but serum NO is lower in preeclamptic group compared with control group may suggest independent regulation of NO in the two compartments. The determination of CSF-NO metabolites could be useful to clarify whether increased NO production is predominantly associated with poor perfusion of the brain in preeclampsia.     

Endogenous inhibitors of nitric oxide and preeclampsia: A review

Nitric oxide (NO) is a potent vasodilator. NO is synthesized by NO synthases (NOS) and NOS are inhibited by asymmetrical dimethylarginine (ADMA). ADMA is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) and excreted in the kidneys. Lower ADMA levels in pregnant women compared to non-pregnant controls suggest that ADMA has a role in vascular dilatation and blood pressure changes. Several studies show an increase in ADMA levels in pregnancies complicated with preeclampsia. Elevated ADMA levels in preeclampsia are seen before clinical symptoms have developed; these findings suggest that ADMA has a role in the pathogenesis of preeclampsia.     

Possible role of asymmetric dimethylarginine (ADMA) in prediction of perinatal outcome in preeclampsia and fetal growth retardation related to preeclampsia

Objective: The objective of this study is to investigate maternal serum and neonatal umbilical cord asymmetric dimethylarginine (ADMA) levels in prediction of perinatal prognosis in pregnancies with preeclampsia (PE) and fetal intrauterine growth retardation (IUGR) accompanying PE (PE?+?IUGR).

Methods: Maternal serum ADMA (msADMA) and neonatal umbilical cord ADMA (ucADMA) levels were studied from 34 patients with PE, 25 patients with PE?+?IUGR, and 30 healthy pregnant controls in this prospective case–control study. Umbilical artery Doppler indices of fetuses, birth weights, Apgar scores, umbilical artery pH measurements of neonates, and admissions to neonatal intensive care unit (NICU) were recorded.

Results: Median msADMA was significantly higher in PE and PE?+?IUGR groups (p?=?0.024 and p?=?0.011, respectively), and ucADMA was significantly higher in PE and PE?+?IUGR groups than the control group (p?=?0.029 and p?=?0.018, respectively). Median msADMA and ucADMA levels were significantly higher in the PE?+?IUGR group than the PE group (p?=?0.019 and 0.021, respectively). ucADMA levels did not correlate with fetal umbilical arterial blood flow neither in the PE nor in the PE?+?IUGR group (p?=?0.518 and p?=?0.892, respectively). None was related with neonatal umbilical artery pH or NICU admission rates.

Conclusions: msADMA and ucADMA correlated with severity of PE. msADMA and ucADMA failed to predict perinatal outcome in patients with PE and PE?+?IUGR.     

Angiotensinogen and endothelial nitric oxide synthase gene polymorphisms among Hispanic patients with preeclampsia

OBJECTIVE: We sought to establish an association between preeclampsia and the methionine to threonine polymorphism at amino acid residue 235 (Met235Thr) in angiotensinogen in a Hispanic population. We looked for a relationship between this allele and the allele in the endothelial nitric oxide synthase gene (NOS3) that produces the A form (NOS3*A) with respect to preeclampsia. STUDY DESIGN: Clinical data were collected from 87 patients with preeclampsia and 53 control subjects. Patients and controls were genotyped for the angiotensinogen polymorphism allele (AGT*T) and the NOS3*A polymorphism. We then compared patients with preeclampsia and control subjects and investigated disease severity within the preeclampsia group as a function of genotype. RESULTS: The AGT*T allelic frequencies among patients with preeclampsia and control subjects were 0.72 and 0.70, respectively (P =.84). The blood pressure of patients with an AGT*T allele who also carried a NOS3*A allele was higher at earlier gestational ages (r = -0.052; P =.02). Analysis suggested that the systolic blood pressure differences were due to gestational age effects and the presence of a NOS3*A allele (P <.10). CONCLUSION: The AGT*T allele was not associated with the development of preeclampsia. Independently of the presence of an AGT*T allele, the NOS3*A allele was associated with a higher blood pressure at an earlier gestational age.     

Endogenous inhibitors of nitric oxide and preeclampsia: a review.

Nitric oxide (NO) is a potent vasodilator. NO is synthesized by NO synthases (NOS) and NOS are inhibited by asymmetrical dimethylarginine (ADMA). ADMA is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) and excreted in the kidneys. Lower ADMA levels in pregnant women compared to non-pregnant controls suggest that ADMA has a role in vascular dilatation and blood pressure changes. Several studies show an increase in ADMA levels in pregnancies complicated with preeclampsia. Elevated ADMA levels in preeclampsia are seen before clinical symptoms have developed; these findings suggest that ADMA has a role in the pathogenesis of preeclampsia.     

Levels of asymmetric dimethylarginine throughout normal pregnancy and in pregnancies complicated with preeclampsia or had a small for gestational age baby

Objective: The aim of this study was to investigate maternal asymmetric dimethylarginine (ADMA) concentrations at the three trimesters of pregnancy in uncomplicated pregnancies and in women who developed preeclampsia or had small for gestational age infants (SGA) without preeclampsia. Methods: ADMA concentrations were retrospectively determined in the first, second and third trimester of pregnancy in 41 uncomplicated pregnancies, 10 pregnancies complicated with preeclampsia and 14 pregnancies that delivered a SGA baby. ADMA was measured with an ELISA kit. Results: Mean (±SD) concentrations of ADMA (µmol/L) in uncomplicated l pregnancies were: 0.51?±?0.14; 0.52?±?0.13; 0.58?±?0.16 in the three trimesters, respectively. ADMA concentrations in SGA pregnancies were significantly lower in each trimester compared to uncomplicated pregnancies: (0.40?±?0.10, p?=?0.005 1st trim; 0.42?±?0.10, p?=?0.007 2nd trim; 0.45?±?0.10, p?=?0.007 3rd trim). Although pregnancies that developed preeclampsia had higher ADMA concentration in all trimesters compared to uncomplicated pregnancies (0.58?±?0.10; 0.63?±?0.14; 0.68?±?0.11), the difference was statistically significant only in the 2nd trimester (p?=?0.02). Conclusions: Maternal serum ADMA concentration tends to increase during normal pregnancy. Pregnancies with SGA infants had significantly lower ADMA levels in all trimesters of pregnancy. ADMA concentrations in the 2nd trimester was significantly elevated in pregnancies that later developed preeclampsia.     

Plasma malondialdehyde, superoxide dismutase, sE-selectin, fibronectin, endothelin-1 and nitric oxide levels in women with preeclampsia

OBJECTIVE: The purpose of this study was to determine plasma malondialdehyde (MDA), superoxide dismutase (SOD), soluble E-selectin (sE-selectin), fibronectin, endothelin-1 (ET-1) and nitric oxide (NO) levels in women with preeclampsia and to find out the relations of diastolic blood pressure with these variables. STUDY DESIGN: We performed a case-control study consisting of randomly selected 34 healthy pregnant women and 35 patients diagnosed as preeclampsia. Lipoperoxidation was ascertained by the formation of MDA. SOD activity was determined by the method of Sun et al. Plasma concentration of NO was estimated using colorimetric assay. Plasma ET-1 and sE-selectin were measured by enzyme-linked immunosorbent assay (ELISA). A nephelometric method for fibronectin quantitation was used. RESULTS: The mean plasma level of MDA was significantly higher and SOD was significantly lower in preeclamptic pregnancies (P<0.001). Plasma concentrations of fibronectin, sE-selectin and ET-1 were significantly increased, whereas NO was significantly decreased in women with preeclampsia than normotensive women (P<0.001). CONCLUSION: Increased plasma levels of MDA, fibronectin, sE-selectin, ET-1, and decreased plasma levels of NO and SOD in preeclamptic patients suggest that poorly perfused fetoplacental unit is the origin of oxygen free radicals and lipid peroxides.     

Estimation of oxidative products of nitric oxide (nitrates, nitrites) in preeclampsia

Oxidative products of nitric oxide, serum nitrates and nitrites were estimated in 50 primigravidas with preeclampsia and in 50 gestation and age-matched normotensive primigravidas. Thirty three (66%) of these women had mild preeclampsia and 17 (34%) had severe preeclampsia. Serum nitrate and nitrite levels were significantly higher in preeclamptic women (nitrates - 15 +/- 1.17; nitrites - 11.82 +/- 1.16 micromol/L) than in the normotensive pregnant women (nitrates 11.82 +/- 1.16; nitrites - 5.08 +/- 0.47 micromol/L, p < 0.001). In preeclamptic women, serum nitrate and nitrite levels correlated with the severity of the disease (mild preeclampsia nitrate - 14.46 +/- 1.98; nitrite 6.21 +/- 0.84 micromol/L, severe preeclampsia nitrate - 16.65 +/- 3.64; Nitrite - 6.87 +/- 1.56 micromol/L). In preeclampsia there was significant positive correlation between nitrate and nitrite levels and diastolic blood pressure and proteinuria.