Urinary levels of nitric oxide metabolites in normal pregnancy and preeclampsia

Reduced Abundance of Nitrate-Reducing Bacteria in the Oral Microbiota of Women with Future Preeclampsia

The oral microbiota can contribute to the regulation of blood pressure by increasing the availability of nitric oxide through the reduction of nitrate to nitrite, which can be converted into nitric oxide in the stomach and then enter the circulation. It is unclear if the composition of the oral microbiota is different between women who do and do not develop preeclampsia. This study aimed to compare the composition of the buccal microbiota just prior to the development of symptoms at 36 weeks gestation in 12 women who developed late-onset preeclampsia and 24 matched women who remained normotensive throughout pregnancy by 16S rRNA gene amplicon sequencing. The abundance of the nitrate-reducing Veillonella spp V. parvula and V. dispar and a subunit of nitrate reductase narH was compared using real-time PCR. The abundance of bacteria was correlated with maternal blood pressure and dietary intake of nitrate-containing vegetables. The results showed that the abundance of nitrate-reducing bacteria including Veillonella, specifically V. parvula, and Prevotella was reduced in women who developed preeclampsia. Veillonella but not Prevotella abundance was negatively correlated with maternal blood pressure. The dietary intake of nitrate-containing vegetables did not differ between the groups and was not correlated with the abundance of Veillonella. There was no difference in the abundance of the nitrate reductase subunit narH between the groups. These results suggest that the abundance of nitrate-reducing bacteria is reduced in the oral microbiota of women who later develop preeclampsia, indicating a potential pathway for prevention.

Antepartum and postpartum changes in adipokines, endothelial dysfunction, inflammatory markers and other biochemical parameters in preeclamptic women: A prospective observational cohort study

This study aimed at evaluating the role played by insulin resistance, lipid metabolism disorder, oxidative stress, resistin, vaspin, Interleukin-18 and asymmetric dimethyl arginine as a marker for endothelial dysfunction in the pathogenesis of preeclampsia. This prospective observational cohort study involved 60 women who were classified into: 20 non-pregnant women (group 1 or control group), 20 normally pregnant women (group 2) and 20 preeclamptic women (group 3) at their third trimester. The pregnant women were assessed at their third trimester and further re-evaluated four weeks after delivery. The assessment included demography, assessment of proteinuria and urinary protein to creatinine ratio, blood pressure measurement and assessment of fasting blood glucose, fasting insulin level, lipid panel and the circulating levels of malondialdehyde, resistin, vaspin, interleukin-18 and asymmetric dimethyl arginine. Preeclamptic women showed more atherogenic lipid profile, significantly higher Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and significantly elevated levels of malondialdehyde, resistin, vaspin and interleukin-18 than the other study groups. Serum asymmetric dimethyl arginine concentration showed non-significant difference among the three study groups. The levels of resistin and vaspin showed significant decrease four weeks postpartum in preeclamptic group. We concluded that, preeclampsia was associated with insulin resistance, dyslipidemia, oxidative stress, inflammation and significant changes in adipokines; resistin and vaspin. Furthermore, the significant increase in the serum levels of resistin and vaspin at the third trimester and their significant decline four weeks postpartum in preeclamptic group focus the attention on the role played by these adipokines in the pathogenesis of preeclampsia.

Sildenafil Citrate Does Not Reprogram Risk of Hypertension and Chronic Kidney Disease in Offspring of Preeclamptic Pregnancies in the Dahl SS/Jr Rat

Background

Preeclampsia is a disorder of pregnancy with accompanying high disease and economic burdens in the United States. Evidence supporting longstanding effects of preeclampsia on the offspring of affected pregnancies is high, but the effects of current antihypertensive therapies for preeclampsia on cardio-renal outcomes are largely unknown. The purpose of this study was to test the hypothesis that sildenafil citrate, a phosphodiesterase-5 inhibitor, reprograms the risk of hypertension and kidney disease in offspring of preeclamptic pregnancies by altering responses to secondary stressors.

Methods

Dahl SS/Jr rats on a 0.3% NaCl diet were mated. At gestational day 10, pregnant dams were randomized to vehicle diet or diet with sildenafil (50 mg/kg per day), which was continued until birth. Pups were weaned at 4 weeks of age and allowed to age on a 0.3% NaCl diet until 3 months of age. At this point, pups were randomized into three groups: baseline or no intervention, 2% NaCl diet challenge for 4 weeks, or a subpressor infusion of angiotensin II (200 ng/kg per minute) for 2 weeks.

Results

There were no differences among maternal treatment groups at baseline. Upon introduction of 2% NaCl diet, male offspring of sildenafil-treated dams exhibited an attenuated rise in BP; however, this protection was not observed during angiotensin II infusion.

Conclusions

Our findings indicate that intrapartum sildenafil does not reprogram the risk of hypertension and kidney disease in offspring of preeclamptic pregnancies.

Preeclampsia beyond pregnancy: long-term consequences for mother and child

Preeclampsia is defined as new-onset hypertension after the 20th wk of gestation along with evidence of maternal organ failure. Rates of preeclampsia have steadily increased over the past 30 yr, affecting ∼4% of pregnancies in the United States and causing a high economic burden (22, 69). The pathogenesis is multifactorial, with acknowledged contributions by placental, vascular, renal, and immunological dysfunction. Treatment is limited, commonly using symptomatic management and/or early delivery of the fetus (6). Along with significant peripartum morbidity and mortality, current research continues to demonstrate that the consequences of preeclampsia extend far beyond preterm delivery. It has lasting effects for both mother and child, resulting in increased susceptibility to hypertension and chronic kidney disease (45, 54, 115, 116), yielding lifelong risk to both individuals. This review discusses recent guideline updates and recommendations along with current research on these long-term consequences of preeclampsia.

Increased circulating trimethylamine N-oxide plays a contributory role in the development of endothelial dysfunction and hypertension in the RUPP rat model of preeclampsia

OBJECTIVE

We examined whether trimethylamine-N-oxide (TMAO) plays a role in endothelial dysfunction and hypertension in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia (PE).  Methods: Normal pregnant rats and RUPP rats were treated without or with 3,3-Dimethyl-1-butanol (DMB, a TMAO inhibitor) from gestational day 14.  Results: On day 19 of gestation, RUPP rats had higher plasma TMAO, impaired vasodilation and hypertension, decreased interleukin (IL)-10, increased superoxide production and proinflammatory cytokines in the aorta. All of which were reversed by DMD.  Conclusion: Increased circulating TMAO downregulates IL-10 and promotes vascular inflammation and oxidative stress, contributing to endothelial dysfunction and hypertension in PE.

Mechanisms and Clinical Significance of Endothelial Dysfunction in High-Risk Pregnancies

The maternal cardiovascular system undergoes critical anatomic and functional adaptations to achieve a successful pregnancy outcome which, if disrupted, can result in complications that significantly affect maternal and fetal health. Complications that involve the maternal cardiovascular system are among the most common disorders of pregnancy, including gestational hypertension, preeclampsia, gestational diabetes, and impaired fetal growth. As a central feature, maternal endothelial dysfunction is hypothesized to play a predominant role in mediating the pathogenesis of these high-risk pregnancies, and as such, might proceed and precipitate the clinical presentation of these pregnancy disorders. Improving or normalizing maternal endothelial function in high-risk pregnancies might be an effective therapeutic strategy to ameliorate maternal and fetal clinical outcomes.

Preeclampsia 2012

Preeclampsia is a common complication of pregnancy associated with high maternal morbidity and mortality and intrauterine fetal growth restriction. There is extensive evidence that the reduction of uteroplacental blood flow in this syndrome results from the toxic combination of hypoxia, imbalance of angiogenic and antiangiogenic factors, inflammation, and deranged immunity. Women treated for preeclampsia also have an increased risk for cardiovascular and renal disease. At present it is unclear if the increased cardiovascular and renal disease risks are due to residual and or progressive effects of endothelial damage from the preeclampsia or from shared risk factors between preeclampsia and cardiac disease. Moreover, it appears that endothelin-1 signaling may play a central role in the hypertension associated with preeclampsia. In this paper, we discuss emerging data on the pathogenesis of preeclampsia and review therapeutic options.

Effect of intravenous hydralazine infusion on maternal plasma nitric oxide levels in gestations complicated with severe preeclampsia: a pilot study

AIM

To investigate the effect of intravenous hydralazine infusion on maternal nitric oxide (NO) levels.

METHODS

This pilot study comprised 40 (n = 40) gestations complicated with severe preeclampsia to whom maternal plasma NO levels were determined by chemiluminescence before and after hydralazine administration. Blood pressure values were concomitantly assessed.

RESULTS

After 20 min of intravenous hydralazine infusion blood pressure values decrease significantly in term and preterm gestations. This was accompanied by an overall significant decrease in mean plasma NO values (38.7 ± 12.9 to 35.4 ± 13.9 μmol/L, p < 0.05). Despite this, NO values decreased in 67.5% of cases (a 17.6% from baseline) and increased in 32.5% (a 14.8% from baseline) (p < 0.05 for both). Blood pressure decrease (%) was lower (systolic and diastolic) among those displaying a NO decrement than in the increment group. Interestingly, gestational age was higher in the group displaying decreased NO; however, this did not reach statistical significance (37.5 ± 2.7 vs. 35.9 ± 2.8 weeks, p = 0.08).

CONCLUSION

The results of this study fail to demonstrate a similar NO secretion after hydralazine infusion in women with severe preeclampsia.

The role of the L-arginine-nitric oxide pathway in preeclampsia

Preeclampsia (PE) is a major cause of maternal and perinatal mortality, especially in developing countries. Its etiology involves multiple factors, but no specific cause has been identified. Evidence suggests that clinical manifestations are caused by endothelial dysfunction. Nitric oxide (NO), which is synthesized from L-arginine in endothelial cells by the endothelial nitric oxide synthase (eNOS), provides a tonic dilator tone and regulates the adhesion of white blood cells and platelet aggregation. Alterations in the L-arginine-NO pathway have been associated with the development of PE. Various studies, reporting decreased, elevated or unchanged levels of nitrite (NO(2)) and nitrate (NO(3)), two end products of NO metabolism, have been published. Our group contributed to those contradictory reports describing cases of PE with both elevated and decreased levels of NO(2) and NO(3). Apparently, diminished levels of NO could be related to deficiencies in the ingestion of dietary calcium associated to low levels of plasma ionic calcium, which is crucial to the eNOS' activity. Also, low levels of NO could be associated with the presence of eNOS polymorphisms or the presence of increased levels of ADMA, the endogenous inhibitor of NO. High levels of NO associated to low levels of cGMP suggest a decreased bioactivity of NO, which is probably related to an increased degradation of NO caused by a high production of superoxide in states of infection and inflammation. The present article analyses and reviews the reported paradoxical roles of the L-arginine-NO pathway in PE and gives a possible explanation for these results.

Effect of posture on creatinine clearance in late pregnancy and after pregnancy

AIM

To assess creatinine clearance that indicates glomerular filtration rate (GFR) and to demonstrate the effect of posture on creatinine clearance in late pregnancy compared to the non-pregnant state.

METHODS

Twenty-six healthy pregnant women aged 19-30 years were studied for two sessions, first in their third trimester of pregnancy and then in a non-pregnant state at 6-12 weeks after delivery. In both sessions, creatinine clearance was assessed at three periods: the 24-h baseline, and at the end of 2-h sitting and 2-h lying (in left lateral decubitus position) periods. Urine and blood samples were collected for creatinine clearance measurement.

RESULTS

The results showed that the 24-h creatinine clearance in late pregnancy was 28.3% higher than that in the non-pregnant state (122.6 +/- 26.2 vs 95.3 +/- 15.1 mL/min per 1.73 m2, P < 0.001). In late pregnancy, after 2-h sitting, creatinine clearance decreased significantly (10%) compared to the 24-h baseline (122.6 +/- 26.2 vs 110.4 +/- 28.6 mL/min per 1.73 m2, P < 0.001). Creatinine clearance rose back to the high baseline level after the pregnant woman laid in left lateral decubitus for 2 h. The decrease in creatinine clearance during prolonged sitting was not seen in the non-pregnant state. At any posture, the creatinine clearance was always higher in the pregnant state than in the non-pregnant.

CONCLUSIONS

This study showed that creatinine clearance in late pregnancy was much higher than in the non-pregnant state, and was affected by sitting for up to 2 h. It might be wise for women to lay down in the left lateral decubitus position for a while after many hours of sitting when pregnancy is approaching its term.

Effects of Oral L-Arginine on the Foetal Condition and Neonatal Outcome in Preeclampsia: A Preliminary Report

Estimation of the influence of oral supplementation with low dose of L-arginine on biophysical profile, foeto-placental circulation and neonatal outcome in preeclampsia. Randomized, placebo-controlled, double-blind, clinical trial. Oral therapy with 3 g of L-arginine daily or placebo as a supplement to standard therapy. Eighty-three preeclamptic women, randomly assigned to the L-arginine (n=42) or placebo (n=41) groups; [n=30 (L-arginine) and n=31 (placebo) ended the study, respectively]. Foetal gain chances due to ultrasound biometry, biophysical profile, Doppler velocimetry of pulsatility indices of umbilical and middle cerebral arteries, cerebro-placental ratio, as well as differences in duration of pregnancy and clinical data of newborn. L-arginine treatment transitory accelerated foetal gain and improved biophysical profile. Starting from 3rd week of therapy, the umbilical artery pulsatility indices values were significantly lower in L-arginine than in placebo group. Moreover, treatment with L-arginine caused significant increase of middle cerebral artery pulsatility indices and cerebro-placental ratio values. Latency was longer in L-arginine group. Neonates delivered in the L-arginine group revealed higher Apgar score. Supplementary treatment with oral L-arginine seems to be promising in improving foetal well-being and neonatal outcome as well as in prolonging pregnancy complicated with preeclampsia. However, these benefits require confirmation in more-powered, larger studies.

Plasma- and urine concentrations of nitrite/nitrate and cyclic Guanosinemonophosphate in intrauterine growth restricted and preeclamptic pregnancies

BACKGROUND

The Nitric Oxide (NO) system plays an important role in the establishment and maintenance of the feto-placental circulation. Research on the pathogenesis of preeclampsia in several studies has established the involvement of the NO-system in preeclampsia and fetal intrauterine growth restriction (IUGR). In the presented study we analyzed the urine and plasma concentrations of nitrite/nitrate, the stable endproducts of NO and its second messenger, cyclic Guanosinemonophosphate (cGMP) in normal, preeclamptic and IUGR pregnancies.

PATIENTS AND METHODS

In total 76 patients were investigated in a prospective study for repeated determination of plasma and urinary levels of nitrate/nitrite and cGMP: 49 patients with a normal course of pregnancy, 14 patients with fetal IUGR and 13 patients with preeclampsia were included into the study. Plasma and urine Nitrite/Nitrate-concentrations were determined using a Colorimetric Assay (Cayman Inc., USA), concentrations of the second messenger cGMP in plasma and urinary samples were determined with a J(125)-Radio-Immuno-Assay (ibl Inc., Germany). The Stat View Program (Abacus Concepts, Inc., Berkeley, CA, 1992-1998) was used for statistical analysis, a P value <0.05 was considered significant.

RESULTS

Analyzing the data with the Kruskall-Wallis test a significance was reached for Plasma Nitrite/Nitrate (P=0.0236), plasma cGMP (P=0.004) and urinary nitrite/nitrate (P=0.032). No significance was seen for urinary cGMP (P=0.656). Comparing normal and preeclamptic and normal and IUGR pregnancies the following significant differences were seen (Mann-Whitney U test): In preeclamptic pregnancies urine nitrite/nitrate concentration was significantly lower compared to normal pregnancies (P=0.009) No significant difference between normal and preeclamptic pregnancies for plasma nitrite/nitrate (P=0.819) and plasma-cGMP (P=0.072) could be observed. In IUGR pregnancies plasma nitrite/nitrate and the plasma-cGMP concentrations were both significantly lower compared to normal pregnancies (P=0.0077 and 0.0066) in IUGR-pregnancies. No significance was reached when analyzing urine-Nitrite/Nitrate (P=0.7).

CONCLUSION

Whereas in preeclampsia a reduced urinary nitrite/nitrate was analyzed, IUGR pregnancies showed reduced plasma nitrite/nitrate and cGMP. A reduced release of NO into the maternal circulation might lead to the presented findings and be involved in the pathogenesis of preeclampsia and fetal IUGR.

Expression of phosphodiesterase 5 in maternal and fetal sheep

OBJECTIVE

Ovine pregnancy is associated with elevated levels of nitric oxide. Nitric oxide stimulates cyclic guanosine monophosphate (cGMP), which results in vascular smooth muscle relaxation/vasodilation. Phosphodiesterase type 5 regulates cGMP in the urogenital track. The present study was designed to determine message expression of phosphodiesterase type 5 in the myometrium, uterine vessels, and placentome of the sheep and phosphodiesterase type 5 protein expression in the maternal and fetal placentome.

STUDY DESIGN

Tissue was collected from 5 nonpregnant and 5 pregnant anesthetized animals (gestational day = 134 +/- 4) and frozen at -80 degrees C. Optimized reverse transcription-polymerase chain reaction was performed on all tissues, and immunohistochemistry was performed on the placentome only.

RESULTS

Phosphodiesterase type 5 messenger ribonucleic acid levels were significantly higher in the myometrium and placentome, compared with the maternal blood vessels. Phosphodiesterase type 5 protein was immuno-localized to the vascular smooth muscle of the maternal vessels, stroma, and placental capsule only.

CONCLUSION

Although phosphodiesterase type 5 messenger ribonucleic acid was present in the fetal placenta, phosphodiesterase type 5 protein was expressed only in maternally derived placental tissue. This suggests that regulation of cGMP levels and vascular tone in the umbilical circulation differs from the uterine circulation.

L-arginine attenuates hypertension in pregnant rats with reduced uterine perfusion pressure

A chronic reduction in uterine perfusion pressure in the pregnant rat is associated with significant elevations in mean arterial pressure, proteinuria, and reductions in kidney function as is chronic nitric oxide blockade, suggesting that nitric oxide deficiency may contribute to the clinical manifestations of preeclampsia. The purpose of this study was to determine whether supplementation with L-arginine, the precursor for nitric oxide, attenuates the hypertension produced in response to a chronic reduction in uterine perfusion pressure in the pregnant rat. Reduced uterine perfusion was initiated at day 14 of gestation with arterial pressure determined at day 19 of gestation in conscious, chronically instrumented rats. Arterial pressure was significantly elevated in pregnant rats with chronic reductions in uterine perfusion as compared with pregnant control rats (132+/-2 versus 109+/-2 mm Hg, P<0.01, respectively). Treatment with L-arginine (2%) in the drinking water was initiated at day 10 of gestation. l-arginine supplementation resulted in a significant decrease in arterial pressure in both pregnant rats with reduced uterine perfusion pressure (113+/-2 mm Hg treated, P<0.01 versus untreated pregnant with reduced uterine perfusion pressure) and pregnant control (97+/-3 mm Hg treated, P<0.01 versus untreated pregnant) rats. However, supplementation with L-arginine decreased blood pressure by 19 mm Hg in pregnant with reduced uterine perfusion pressure (untreated versus treated) as compared with 12 mm Hg in pregnant (untreated versus treated) rats. Thus, these results suggest that l-arginine supplementation may be beneficial in attenuating the hypertension in preeclampsia.

Decreasing resistance in the maternal uterine and peripheral arterial system is apparently unrelated to plasma and urinary levels of nitrite/nitrate and cyclic-guanosinmonophosohate during the course of normal pregnancies

AIMS

The aim of the presented study was to clarify the relationship between the pulsatility index of the uterine arteries and the maternal cubital artery and peripheral concentrations of the metabolites of nitric oxide (NO) and its second messenger cyclic guanosinmonophophate (cGMP) during the normal course of pregnancy and postpartum.

METHODS

49 uncomplicated pregnancies were investigated every 4-6 weeks until delivery, 29 of them were additionally investigated postpartum. Paralleling each Doppler sonographic investigation maternal blood and urine samples were taken. The measurements of nitrite/nitrate and cGMP were performed with a colorimetric and radio immuno assay. We demonstrate a significant decrease of the PI of the uterine arteries and of the cubital artery with inverse correlation to advancing gestational age.

RESULTS

The concentrations of nitrite/nitrate and cGMP remain stable during gestation and do not correlate to the PI of the uterine and cubital artery. Postpartum a re-increase in the uterine and peripheral resistance can be shown. The concentrations of urinary cGMP and nitrite/nitrate as well as plasma cGMP remain unchanged, whereas plasma nitrite/nitrate decreases postpartum.

CONCLUSIONS

The status of NO biosyntheses in normal pregnancy remains controversial. We hypothesize further systemically acting mediators which contribute to the decreasing vascular resistance.

Plasma anti-oxidant status and lipid profile in non-gravida women with a history of pre-eclampsia

OBJECTIVE

To investigate the total plasma anti-oxidant status, the plasma lipid profile and the uterine artery Doppler velocity waveform in formerly pre-eclamptic women.

METHODS

Thirty-two formerly pre-eclamptic, non-gravida women constituted the study group, while 28 age-matched non-gravida women who had never had pre-eclampsia served as control subjects. On days 17-19 of their menstrual cycle, fasting plasma samples were collected for total anti-oxidant status (TAS) and lipid profile evaluation, and uterine artery Doppler velocity waveform studies were performed. Results were analyzed with Mann-Whitney U-test and Pearson correlation analysis.

RESULTS

There was no significant difference between the groups in means of the uterine artery Doppler velocity waveforms and the plasma lipid levels, but body mass index values were significant (P < 0.005). The TAS value was subnormal in 72% of the formerly pre-eclamptic group and in 35% of the control group. The mean plasma TAS value was 1.20 +/- 0.05 mmol/L and was significantly lower in the study group when compared with the control group (P < 0.05).

CONCLUSION

The current study reveals significantly decreased TAS in women with a history of pre-eclampsia, which may have an important role in pathophysiology.

The immunology of preeclampsia

The immune maladaptation hypothesis of preeclampsia is concordant with cytokine-mediated oxidative stress, chronology of endothelial activation, lipid changes, adverse effect of changing partners, and the protective effect of sperm exposure. Genetic factors may involve underlying hereditary thrombophilic disorders and hyperhomocysteinemia, essential hypertension and/or obesity, or control of the Th1/Th2 balance and thus affect the maternal response against fetal antigens. Placental ischemia and increased syncytiotrophoblast deportation are probably end-stage disease phenomena.

Maternal serum nitric oxide levels associated with biochemical and clinical parameters in hypertension in pregnancy

OBJECTIVES

To measure maternal serum concentrations of total nitrites, as an index of nitric oxide synthesis, in normal and hypertensive pregnant women, and to examine the correlation between these concentrations and several variables of clinical interest.

STUDY DESIGN

A total of 60 women in four different groups were studied: 10 normotensive pregnant women, 17 pregnant women with preeclampsia, 18 pregnant women with gestational hypertension and 15 pregnant women with chronic hypertension. Serum nitrite levels were determined using the Griess reaction after reduction with nitrate reductase.

RESULTS

Serum nitrite levels were higher in preeclamptic women (34.11+/-14 micromol/l, P=0.04), lower in chronic hypertensive women (19.56+/-6.46 micromol/l, P=0.04) and similar in women with gestational hypertension (26.97+/-9.44 micromol/l) in comparison to the control group (25.37+/-7.24 micromol/l). Serum nitrite levels in preeclamptic women had significant positive correlations with hematocrit, fasting insulinemia, and apolipoprotein B and negative correlations with platelet count, serum phosphorus and glucose:insulin ratio. In pregnant women with chronic hypertension a negative correlation was found between serum nitrite levels and active partial thromboplastin time. In pregnant women with gestational hypertension, serum nitrite levels had negative correlations with birthweight and 24-h urine calcium, and positive correlations with mean corspuscular hemoglobin, 24-h urine sodium and maternal age.

CONCLUSIONS

We suggest that in women with preeclampsia, a higher maternal nitric oxide level may act as a compensatory mechanism against hemoconcentration and platelet aggregation and that nitric oxide production may be related to some metabolic events. In women with gestational hypertension, higher serum nitrite levels may be related to clinical and biochemical findings common in preeclampsia. In chronic hypertension, a lower maternal nitric oxide level is related to the status of coagulation.