The role of arginine, homoarginine and nitric oxide in pregnancy

Association between eNOS gene polymorphisms and the risk of unexplained recurrent spontaneous abortion in Yunnan province, China

BACKGROUND

Recurrent spontaneous abortion affects approximately 1-2% of reproductive-age women, with roughly half of RSA cases classified as unexplained recurrent spontaneous abortion (URSA). Genetic polymorphisms in eNOS gene have been shown to have significant implications across various disease processes. Nevertheless, the potential impact of eNOS gene polymorphisms on the susceptibility to URSA in Yunnan population has yet to be explored or documented.

OBJECTIVE

This study aims to investigate the potential association between specific variations in the eNOS gene (VNTR 4b/a, -786T > C, and +894G > T) and the risk of URSA in Yunnan population.

METHODS

A total of 243 URSA patients and 241 healthy females are involved in this study. We conducted amplification of the eNOS gene fragment and performed sanger sequencing to detect the specific eNOS gene polymorphisms, including VNTR 4b/a, -786T > C, and +894G > T. Using a multivariate logistic regression model, we evaluate the potential association between eNOS gene polymorphisms (VNTR 4b/a, -786T > C, and +894G > T) and the risk of URSA. Furthermore, serum NO levels were measured in URSA patients.

RESULTS

The presence of VNTR 4a, -786C, and +894T alleles was found to be associated with an increased risk of URSA. Additionally, our study revealed a significant association between the G-C-4b haplotype of the investigated eNOS gene polymorphisms and a predisposition to URSA. Notably, these eNOS polymorphisms were shown to reduce serum NO levels in URSA patients.

CONCLUSION

This study provides evidence supporting the association between eNOS gene polymorphisms, VNTR 4b/a, -786T > C, and +894G > T, and the occurrence of URSA in Yunnan Province, China.

Maternal-derived galectin-1 shapes the placenta niche through Sda terminal glycosylation: Implication for preeclampsia

Placental abnormalities cause impaired fetal growth and poor pregnancy outcome (e.g. preeclampsia [PE]) with long-lasting consequences for the mother and offspring. The molecular dialogue between the maternal niche and the developing placenta is critical for the function of this organ. Galectin-1 (gal-1), a highly expressed glycan-binding protein at the maternal-fetal interface, orchestrates the maternal adaptation to pregnancy and placenta development. Down-regulation or deficiency of gal-1 during pregnancy is associated with the development of PE; however, the maternal- and placental-derived gal-1 contributions to the disease onset are largely unknown. We demonstrate that lack of gal-1 imposes a risk for PE development in a niche-specific manner, and this is accompanied by a placental dysfunction highly influenced by the absence of maternal-derived gal-1. Notably, differential placental glycosylation through the Sda-capped N-glycans dominates the invasive trophoblast capacity triggered by maternal-derived gal-1. Our findings show that gal-1 derived from the maternal niche is essential for healthy placenta development and indicate that impairment of the gal-1 signaling pathway within the maternal niche could be a molecular cause for maternal cardiovascular maladaptation during pregnancy.

Evaluation of oxidative stress markers in subtypes of preeclampsia: A systematic review and meta-analysis

Studies about oxidative stress biomarkers revealed different phenotypes between early and late preeclampsia (PE). Despite that, there is extensive evidence of oxidative stress in investigations that combinate forms different of preeclampsia. This study reviews the oxidative stress profile in the PE subtypes and evaluates which markers are altered in the blood and placental tissue. A search was conducted in databases such as MEDLINE, EMBASE, LILACS, and Web of Science without restricting the year and language of publication. The quality of the studies was evaluated by the Newcastle-Ottawa scale and Joanna Briggs Institute for analytical Cross-Sectional Studies. After 13,319 screened records, 65 were included in the systematic review. The markers of stress oxidative of damage and reactive species were those selected, such as malondialdehyde (MDA), lipid peroxide, advanced protein oxidation products, carbonyl protein, 8-hydroxy-2'-deoxyguanosine, total oxidant status, hydrogen peroxide, nitric oxide (NO). We described the antioxidant activity, including the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase, free glutathione, and total antioxidant capacity (TAC). We results demonstrated that oxidative stress is related to pathophysiology of PE, there were increased lipid peroxidation in the blood and placenta, and in blood a reduction of NO levels and of TAC, like lower enzymatic activity of GPx, CAT in PE, and SOD in mild PE. In addition, altered levels of MDA in the placenta and blood show that placental changes have repercussions on the clinical syndrome and are related to the severity of the disease.

Homoarginine in health and disease

PURPOSE OF REVIEW

Homoarginine (hArg) is an endogenous, nonproteinogenic amino acid. It is enzymatically synthesized from L-arginine and L-lysine. Low hArg concentrations appear to be a risk factor in the renal and cardiovascular systems. This review discusses advances in-vitro and in-vivo experimental and clinical research on hArg in health and disease.

RECENT FINDINGS

Recent studies indicate that low circulating and low urinary concentrations of hArg are associated with morbidity and worse outcome. Although the biological activities of hArg remain still unexplored, hArg supplementation is intensely investigated as a strategy to increase hArg concentration to reach normal levels in cases of low hArg concentrations. The greatest changes in circulating hArg concentrations are observed during pregnancy and after delivery. In healthy adults, a daily dose of 125 mg hArg seems to be optimum to normalize circulating levels. Short-term supplementation of inorganic nitrate enhances hArg biosynthesis in healthy young men. Apart from hArg supplementation, dietary L-arginine and L-citrulline appear to be a promising alternative.

SUMMARY

Considerable progress has been made in recent years, but hArg remains still enigmatic. Further research is required to explore the biological activities of hArg. Supplementation of hArg or its precursors L-citrulline/L-arginine seem to be promising strategies to prevent and overcome altered hArg synthesis.

First-trimester preterm preeclampsia prediction with metabolite biomarkers: differential prediction according to maternal body mass index

BACKGROUND

Prediction of preeclampsia risk is key to informing effective maternal care. Current screening for preeclampsia at 11 to 13 weeks of gestation using maternal demographic characteristics and medical history with measurements of mean arterial pressure, uterine artery pulsatility index, and serum placental growth factor can identify approximately 75% of women who develop preterm preeclampsia with delivery at <37 weeks of gestation. Further improvements to preeclampsia screening tests will likely require integrating additional biomarkers. Recent research suggests the existence of distinct maternal risk profiles. Therefore, biomarker evaluation should account for the possibility that a biomarker only predicts preeclampsia in a specific maternal phenotype.

OBJECTIVE

This study aimed to verify metabolite biomarkers as preterm preeclampsia predictors early in pregnancy in all women and across body mass index groups.

STUDY DESIGN

Observational case-control study drawn from a large prospective study on the early prediction of pregnancy complications in women attending their routine first hospital visit at King's College Hospital, London, United Kingdom, in 2010 to 2015. Pregnant women underwent a complete first-trimester assessment, including the collection of blood samples for biobanking. In 11- to 13-week plasma samples of 2501 singleton pregnancies, the levels of preselected metabolites implicated in the prediction of pregnancy complications were analyzed using a targeted liquid chromatography-mass spectrometry method, yielding high-quality quantification data on 50 metabolites. The ratios of amino acid levels involved in arginine biosynthesis and nitric oxide synthase pathways were added to the list of biomarkers. Placental growth factor and pregnancy-associated plasma protein A were also available for all study subjects, serving as comparator risk predictors. Data on 1635 control and 106 pregnancies complicated by preterm preeclampsia were considered for this analysis, normalized using multiples of medians. Prediction analyses were performed across the following patient strata: all subjects and the body mass index classes of <25, 25 to <30, and ≥30 kg/m². Adjusted median levels were compared between cases and controls and between each body mass index class group. Odds ratios and 95% confidence intervals were calculated at the mean ±1 standard deviation to gauge clinical prediction merits.

RESULTS

The levels of 13 metabolites were associated with preterm preeclampsia in the entire study population (P<.05) with particularly significant (P<.01) associations found for 6 of them, namely, 2-hydroxy-(2/3)-methylbutyric acid, 25-hydroxyvitamin D3, 2-hydroxybutyric acid, alanine, dodecanoylcarnitine, and 1-(1Z-octadecenyl)-2-oleoyl-sn-glycero-3-phosphocholine. Fold changes in 7 amino acid ratios, all involving glutamine or ornithine, were also significantly different between cases and controls (P<.01). The predictive performance of some metabolites and ratios differed according to body mass index classification; for example, ornithine (P<.001) and several ornithine-related ratios (P<.0001 to P<.01) were only strongly associated with preterm preeclampsia in the body mass index of <25 kg/m² group, whereas dodecanoylcarnitine and 3 glutamine ratios were particularly predictive in the body mass index of ≥30 kg/m² group (P<.01).

CONCLUSION

Single metabolites and ratios of amino acids related to arginine bioavailability and nitric oxide synthase pathways were associated with preterm preeclampsia risk at 11 to 13 weeks of gestation. Differential prediction was observed according to body mass index classes, supporting the existence of distinct maternal risk profiles. Future studies in preeclampsia prediction should account for the possibility of different maternal risk profiles to improve etiologic and prognostic understanding and, ultimately, clinical utility of screening tests.

Evaluation of the predictive values of elevated serum L-homoarginine and dimethylarginines in preeclampsia

L-homoarginine (hARG) is involved in nitric oxide biosynthesis, but its role and concentration in preeclampsia (PE) have not been fully revealed. The purpose of this study was to develop and validate a feasible clinical assay to quantify serum hARG, arginine (ARG), asymmetric (ADMA) and symmetric dimethylarginines (SDMA) levels by LC-MS/MS and investigate their differences at different stages of pregnancy with or without preeclampsia. Serum samples were collected from 84 pregnant women without complications (controls), 84 with mild preeclampsia (MPE), and 81 with severe preeclampsia (SPE) at various gestation stages (before the 20th week, during the 20th-28th week or after the 28th week of gestation). No significant difference in ARG levels was observed between PE and controls at any stage (P > 0.05). The serum hARG levels and hARG/ADMA ratios of MPE before the 20th week were higher than those of controls (P < 0.001). ADMA levels of MPE were higher than those of controls during the 20th-28th week (P < 0.01). SDMA levels of SPE were higher than those of MPE (P < 0.01) and controls (P < 0.05) after the 28th week. Elevated serum hARG before the 20th week was identified as an independent predictor for PE (OR = 1.478, 95% CI 1.120-1.950). ROC curve analysis showed serum hARG before the 20th week had a good potential to predict MPE (AUC = 0.875, 95% CI 0.759-0.948). In conclusion, our study indicated that elevated serum hARG and dimethylarginine levels detected by LC-MS/MS might serve as potential biomarkers for the early prediction of PE.

Metabolic Signatures of Pregnancy-Induced Cardiac Growth

The goal of this study was to develop an atlas of the metabolic, transcriptional, and proteomic changes that occur with pregnancy in the maternal heart. Timed pregnancy studies in FVB/NJ mice revealed significant increases in heart size by day 8 of pregnancy (mid-pregnancy; MP), which was sustained throughout the rest of the term compared with non-pregnant controls. Cardiac hypertrophy and myocyte cross-sectional area were highest 7 d after birth (post-birth; PB) and were associated with significant increases in end-diastolic and end-systolic left ventricular volumes and cardiac output. Metabolomics analyses revealed that, by day 16 of pregnancy (late pregnancy; LP), metabolites associated with nitric oxide production as well as acylcholines, sphingomyelins, and fatty acid species were elevated, which coincided with a lower activation state of phosphofructokinase and higher levels of pyruvate dehydrogenase kinase 4 (Pdk4). In the postpartum period, urea cycle metabolites, polyamines, and phospholipid levels were markedly elevated in the maternal heart. Cardiac transcriptomics in LP revealed significant increases in not only Pdk4, but also genes that regulate glutamate and ketone body oxidation, which were preceded in MP by higher expression of transcripts controlling cell proliferation and angiogenesis. Proteomics analysis of the maternal heart in LP and PB revealed significant reductions in several contractile filaments and mitochondrial complex subunits. Collectively, these findings describe the coordinated molecular changes that occur in the maternal heart during and after pregnancy.

Stereochemical Assignment and Absolute Abundance of Nonproteinogenic Amino Acid Homoarginine in Marine Sponges

Together with arginine, the nonproteinogenic amino acid homoarginine is a substrate for the production of vasodilator nitric oxide in the human body. In marine sponges, homoarginine has been postulated to serve as a precursor for the biosynthesis of pyrrole-imidazole alkaloid and bromotyrosine alkaloid classes of natural products. The absolute abundance of homoarginine, its abundance relative to arginine, and its stereochemical assignment in marine sponges are not known. Here, using stable isotope dilution mass spectrometry, we quantify the absolute abundances of homoarginine and arginine in marine sponges. We find that the abundance of homoarginine is highly variable and can far exceed the concentration of arginine, even in sponges where incorporation of homoarginine in natural products cannot be rationalized. The [homoarginine]/[arginine] ratio in marine sponges is greater than that in human analytes. By derivatization of sponge extracts with Marfey's reagent and comparison with authentic standards, we determine the l-isomer of homoarginine to be exclusively present in sponges. Our results shed light on the presence of the high abundance of homoarginine in marine sponge metabolomes and provide the foundation to investigate the biosynthetic routes and physiological roles of this nonproteinogenic amino acid in sponge physiology.

Plasma homoarginine concentrations in ewe's pregnancy and association with the number of fetuses

A striking increase in homoarginine concentrations, about more than 100-fold that observed in humans, was recently reported during pregnancy in a nutritionally induced model of intra-uterine growth restriction in ewes. To determine whether this phenomenon is at least partially related to the nutritional regimen, estrus synchronization, or analytical method, thirty-four one-year-old primiparous, non-synchronized, and well-fed Sarda breed ewes were exposed to fertile rams allowing those who came into estrus to naturally mate. Plasma arginine, homoarginine, asymmetric dimethylarginine, symmetric dimethylarginine, mono methylarginine, and citrulline concentrations were measured in each sample using LC-MS/MS. Homoarginine concentrations showed a 44-fold variation between the highest and the lowest values while the fluctuations of arginine and its analogues and metabolites were much smaller, between 1.1 and 1.6-fold. Repeated-measures correlation analysis showed a significant negative correlation between homoarginine/arginine and arginine/asymmetric dimethylarginine ratios (Rm = -0.40; P < 0.000001). Furthermore, median homoarginine concentrations significantly increased with the number of fetuses. The marked increase in homoarginine concentrations with advancing gestational age is genuine and independent of mating, feeding, diet, and hormone treatment. The higher homoarginine concentrations found in ewes bearing multiple fetuses suggest the presence of a physiological link between this arginine analog and energy metabolism in pregnancy that warrants further investigation.

Developing Novel Tests to Screen for Fetal Growth Restriction

Fetal growth restriction (FGR) is a major determinant of global morbidity and mortality. There is an unmet need for methods to stratify the pregnant population on the basis of FGR risk. Despite evolutionary divergence in mammalian reproduction, studies of genetically modified mice have identified biomarkers that have been validated in women, and a systematic screen for genes that control fetal growth in animals could help identify novel clinical biomarkers. Current approaches to biomarker identification using human samples include both targeted and discovery approaches (omics). Application of omic methods to the placenta and maternal blood has yielded promising results, but comes with logistical, experimental, and analytical challenges and all studies are limited by the lack of a gold standard for disease.

A Significant Change in Free Amino Acids of Soybean (Glycine max L. Merr) through Ethylene Application

In this study, the changes in free amino acids of soybean leaves after ethylene application were characterized based on quantitative and metabolomic analyses. All essential and nonessential amino acids in soybean leaves were enhanced by fivefold (250 to 1284 mg/100 g) and sixfold (544 to 3478 mg/100 g), respectively, via ethylene application. In particular, it was found that asparagine is the main component, comprising approximately 41% of the total amino acids with a twenty-five fold increase (78 to 1971 mg/100 g). Moreover, arginine and branched chain amino acids (Val, Leu, and Ile) increased by about 14 and 2-5 times, respectively. The increase in free amino acid in stem was also similar to the leaves. The metabolites in treated and untreated soybean leaves were systematically identified by gas chromatography-mass spectrometry (GC-MS), and partial variance discriminant analysis (PLS-DA) scores and heat map analysis were given to understand the changes of each metabolite. The application of ethylene may provide good nutrient potential for soybean leaves.

The plasma metabolome of women in early pregnancy differs from that of non-pregnant women

BACKGROUND

In comparison to the non-pregnant state, the first trimester of pregnancy is characterized by systemic adaptation of the mother. The extent to which these adaptive processes are reflected in the maternal blood metabolome is not well characterized.

OBJECTIVE

To determine the differences between the plasma metabolome of non-pregnant and pregnant women before 16 weeks gestation.

STUDY DESIGN

This study included plasma samples from 21 non-pregnant women and 50 women with a normal pregnancy (8-16 weeks of gestation). Combined measurements by ultrahigh performance liquid chromatography/tandem mass spectrometry and by gas chromatography/mass spectrometry generated molecular abundance measurements for each sample. Molecular species detected in at least 10 samples were included in the analysis. Differential abundance was inferred based on false discovery adjusted p-values (FDR) from Mann-Whitney-Wilcoxon U tests <0.1 and a minimum median abundance ratio (fold change) of 1.5. Alternatively, metabolic data were quantile normalized to remove sample-to-sample differences in the overall metabolite abundance (adjusted analysis).

RESULTS

Overall, 637 small molecules met the inclusion criteria and were tested for association with pregnancy; 44% (281/637) of small molecules had significantly different abundance, of which 81% (229/281) were less abundant in pregnant than in non-pregnant women. Eight percent (14/169) of the metabolites that remained significant in the adjusted analysis also changed as a function of gestational age. A pathway analysis revealed enrichment in steroid metabolites related to sex hormones, caffeine metabolites, lysolipids, dipeptides, and polypeptide bradykinin derivatives (all, FDR < 0.1).

CONCLUSIONS

This high-throughput mass spectrometry study identified: 1) differences between pregnant vs. non-pregnant women in the abundance of 44% of the profiled plasma metabolites, including known and novel molecules and pathways; and 2) specific metabolites that changed with gestational age.

Reductions of Circulating Nitric Oxide are Followed by Hypertension during Pregnancy and Increased Activity of Matrix Metalloproteinases-2 and -9 in Rats

Hypertensive pregnancy has been associated with reduced nitric oxide (NO), bioavailability, and increased activity of matrix metalloproteinases (MMPs). However, it is unclear if MMPs activation is regulated by NO during pregnancy. To this end, we examined activity of MMP-2 and MMP-9 in plasma, placenta, uterus and aorta, NO bioavailability, oxidative stress, systolic blood pressure (SBP), and fetal-placental development at the early, middle, and late pregnancy stages in normotensive and Nω-Nitro-L-arginine methyl-ester (L-NAME)-induced hypertensive pregnancy in rats. Reduced MMP-2 activity in uterus, placenta, and aorta and reduced MMP-9 activity in plasma and placenta with concomitant increased NO levels were found in normotensive pregnant rats. By contrast, increased MMP-2 activity in uterus, placenta, and aorta, and increased MMP-9 activity in plasma and placenta with concomitant reduced NO levels were observed in hypertensive pregnant rats. Also, elevated oxidative stress was displayed by hypertensive pregnant rats at the middle and late stages. These findings in the L-NAME-treated pregnant rats were also followed by increases in SBP and associated with fetal growth restrictions at the middle and late pregnancy stages. We concluded that NO bioavailability may regulate MMPs activation during normal and hypertensive pregnancy.

Impact of Arginine Nutrition and Metabolism during Pregnancy on Offspring Outcomes

By serving as a precursor for the synthesis of nitric oxide, polyamines, and other molecules with biological importance, arginine plays a key role in pregnancy and fetal development. Arginine supplementation is a potential therapy for treating many human diseases. An impaired arginine metabolic pathway during gestation might produce long-term morphological or functional changes in the offspring, namely, developmental programming to increase vulnerability to developing a variety of non-communicable diseases (NCDs) in later life. In contrast, reprogramming is a strategy that shifts therapeutic interventions from adulthood to early-life, in order to reverse the programming processes, which might counterbalance the rising epidemic of NCDs. This review presented the role of arginine synthesis and metabolism in pregnancy. We also provided evidence for the links between an impaired arginine metabolic pathway and the pathogenesis of compromised pregnancy and fetal programming. This was followed by reprogramming strategies targeting the arginine metabolic pathway, to prevent the developmental programming of NCDs. Despite emerging evidence from experimental studies showing that targeting the arginine metabolic pathway has promise as a reprogramming strategy in pregnancy to prevent NCDs in the offspring, these results need further clinical application.

Regulation of Nitric Oxide Production in the Developmental Programming of Hypertension and Kidney Disease

Development of the kidney can be altered in response to adverse environments leading to renal programming and increased vulnerability to the development of hypertension and kidney disease in adulthood. By contrast, reprogramming is a strategy shifting therapeutic intervention from adulthood to early life to reverse the programming processes. Nitric oxide (NO) is a key mediator of renal physiology and blood pressure regulation. NO deficiency is a common mechanism underlying renal programming, while early-life NO-targeting interventions may serve as reprogramming strategies to prevent the development of hypertension and kidney disease. This review will first summarize the regulation of NO in the kidney. We also address human and animal data supporting the link between NO system and developmental programming of hypertension and kidney disease. This will be followed by the links between NO deficiency and the common mechanisms of renal programming, including the oxidative stress, renin–angiotensin system, nutrient-sensing signals, and sex differences. Recent data from animal studies have suggested that interventions targeting the NO pathway could be reprogramming strategies to prevent the development of hypertension and kidney disease. Further clinical studies are required to bridge the gap between animal models and clinical trials in order to develop ideal NO-targeting reprogramming strategies and to be able to have a lifelong impact, with profound savings in the global burden of hypertension and kidney disease.

Gene polymorphism associated with endothelial nitric oxide synthase (4VNTR, G894T, C786T) and unexplained recurrent spontaneous abortion risk: A meta-analysis

To evaluate the association between endothelial nitric oxide synthase gene polymorphisms (4VNTR A/B, G894T, C786T) and risk of URSA.Related case-control studies were collected by computers. A meta-analysis was conducted using Stata 12.0 software to assess the strength of association.Altogether 37 articles were examining the relationship between endothelial nitric oxide synthase gene polymorphisms and URSA, among which sixteen (16) studies were related to 4VNTR, twelve (12) to G894T, and nine (9) to C786T, the study suggested that 4VNTR A/B polymorphism was closely connected with URSA risk under all gene models except for recessive model (AA vs. BB + AB). The integrated result which indicated the association between G894T gene mutation and URSA risk had been shown under homozygote (TT vs. GG; OR 1.585, 95%CI 1.175-2.138) and recessive models (TT vs. TG + GG; OR 1.530, 95%CI 1.142-2.052). Considering heterogeneity in the remaining gene models, subgroup analysis was performed on ethnicity, and the results showed that it was the dominant (TT + TG vs. GG; OR 1.585, 95%CI 1.175-2.138) and additive models (T vs. G; OR 1.727, 95%CI 1.372-2.175) of G894T in Asians and the heterozygote model (TG vs. GG; OR 1.015, 95%CI 0.846-1.217) in Caucasians that were associated with URSA (P < .05). Besides C786T gene was significantly connected with URSA under all models except for additive model (T vs. C).It is of great guiding significance for screening out and preventing URSA among high-risk women via testing on 4VNTR A/B, G894T, C786T eNOS under gene models mentioned above which are closely associated with URSA.

Oxidative stress in healthy pregnancy and preeclampsia is linked to chronic inflammation, iron status and vascular function

Background

During normal pregnancy, placental oxidative stress (OS) is present during all three trimesters and is necessary to obtain normal cell function. However, if OS reaches a certain level, pregnancy complications might arise. In preeclampsia (PE), a dangerous pregnancy specific hypertensive disorder, OS induced in the ischemic placenta causes a systemic inflammatory response and activates maternal endothelial cells. In this study, we aimed to quantify superoxide concentrations (as a measure of systemic OS) using electron paramagnetic resonance (EPR) and correlate them to markers of systemic inflammation, iron status and vascular function.

Methods

Fifty-nine women with a healthy pregnancy (HP), 10 non-pregnant controls (NP) and 28 PE patients (32±3.3weeks) were included. During HP, blood samples for superoxide, neutrophil to lymphocyte ratio (NLR), mean platelet volume (MPV) and iron status were taken at 10, 25 and 39 weeks. Vascular measurements for arterial stiffness (carotid-femoral pulse wave velocity (CF-PWV), augmentation index (AIx), augmentation Pressure (AP)) and microvascular endothelial function (reactive hyperemia index (RHI)) were performed at 35 weeks. In PE, all measurements were performed at diagnosis. CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine) was used as spin probe for EPR, since the formed CM radical corresponds to the amount of superoxide.

Results

Superoxide concentration remains stable during pregnancy (p = 0.92), but is significantly higher compared to the NP controls (p<0.0001). At 25 weeks, there is a significant positive correlation between superoxide and ferritin concentration. (p = 0.04) In PE, superoxide, systemic inflammation and iron status are much higher compared to HP (all p<0.001). During HP, superoxide concentrations correlate significantly with arterial stiffness (all p<0.04), while in PE superoxide is significantly correlated to microvascular endothelial function (p = 0.03).

Conclusions

During HP there is an increased but stable oxidative environment, which is correlated to ferritin concentration. If superoxide levels increase, there is an augmentation in arterial stiffness. In PE pregnancies, systemic inflammation and superoxide concentrations are higher and result in a deterioration of endothelial function. Together, these findings support the hypothesis that vascular function is directly linked to the amount of OS and that measurement of OS in combination with vascular function tests might be used in the prediction of PE.

Plasma Homoarginine Concentrations According to Use of Hormonal Contraception

Estrogen is a potent vasodilator through activation of endothelial nitric oxide synthase (eNOS). Arginine and its homologue homoarginine are substrates for NOS, while asymmetric dimethylarginine (ADMA) is a NOS inhibitor. Healthy, never-pregnant women aged 18 to 40 years (n = 158) were categorized according to use of hormonal contraception into non-users (n = 76), users of estrogen contraceptives (EC-users, n = 58) and users of progestins-only contraceptives (PC-users, n = 24). Plasma homoarginine, arginine, ADMA and SDMA concentrations were assayed using a LC-MS/MS method. Compared to non-users, EC users had higher plasma homoarginine (median (interquartile range) 1.63 (1.24, 2.04) vs. 2.39 (2.05, 2.85) µmol/L, p < 0.001), lower arginine (80.8 (72.4, 94.3) vs. 72.1 (62.9, 85.1) µmol/L, p = 0.008) and ADMA (0.52 (0.46, 0.59) vs. 0.48 (0.42, 0.54) µmol/L, p = 0.003) concentrations. The lowest median plasma homoarginine concentration (1.34 (0.92, 1.75) µmol) was seen in PC-users. No differences were seen in SDMA concentrations according to use of hormonal contraception. In healthy, never-pregnant women aged 18 to 40 years, use of estrogen containing contraception was associated with significantly higher plasma concentrations of homoarginine and lower plasma concentrations of arginine and ADMA as compared to non-users, while the lowest plasma homoarginine concentrations were seen in progestin-only users. Whether the observed changes in relation to use of hormonal contraception have an impact on cardiovascular status, should be evaluated in an intervention study.

Maternal cardiovascular and endothelial function from first trimester to postpartum

Objective

To explore noninvasively the complex interactions of the maternal hemodynamic system throughout pregnancy and the resulting after-effect six weeks postpartum.

Methods

Eighteen women were tested beginning at the 12^th week of gestation at six time-points throughout pregnancy and six weeks postpartum. Heart rate, heart rate variability, blood pressure, pulse transit time (PTT), respiration, and baroreceptor sensitivity were analyzed in resting conditions. Additionally, hemoglobin, asymmetric and symmetric dimethylarginine and Endothelin (ET-1) were obtained.

Results

Heart rate and sympathovagal balance favoring sympathetic drive increased, the vagal tone and the baroreflex sensitivity decreased during pregnancy. Relative sympathetic drive (sympathovagal balance) reached a maximum at 6 weeks postpartum whereas the other variables did not differ compared to first trimester levels. Postpartum diastolic blood pressure was higher compared to first and second trimester. Pulse transit time and endothelial markers showed no difference throughout gestation. However, opposing variables PTT and asymmetric dimethylarginine (ADMA) were both higher six weeks postpartum.

Conclusions

The sympathetic up regulation throughout pregnancy goes hand in hand with a decreased baroreflex sensitivity. In the postpartum period, the autonomic nervous system, biochemical endothelial reactions and PTT show significant and opposing changes compared to pregnancy findings, indicating the complex aftermath of the increase of blood volume, the changes in perfusion strategies and blood pressure regulation that occur in pregnancy.

Circulating asymmetric dimethylarginine and the risk of preeclampsia: a meta-analysis based on 1338 participants

Background

Patients with preeclampsia have higher circulating asymmetric dimethylarginine (ADMA). However, whether circulating ADMA is elevated before the diagnosis of preeclampsia has not been determined.

Methods

A meta-analysis of observational studies that reported circulating ADMA level before the onset of preeclampsia was performed. Pubmed and Embase were searched. Standardized mean differences (SMD) with 95% confidence intervals (CI) were used to estimate the differences in circulating ADMA. A random effect model or a fixed effect model was applied depending on the heterogeneity. The predictive efficacy of circulating ADMA for the incidence of preeclampsia was also explored.

Results

Eleven comparisons with 1338 pregnant women were included. The pooled results showed that the circulating ADMA was significantly higher in women who subsequently developed preeclampsia as compared with those did not (SMD: 0.71, p < 0.001) with a moderate heterogeneity (I² = 43%). Stratified analyses suggested elevation of circulating ADMA is more remarkable in studies with GA of ADMA sampling ≥ 20 weeks (SMD: 0.89, p < 0.01) as compared those with GA of ADMA sampling < 20 weeks (SMD: 0.56, p < 0.01; p for subgroup interaction = 0.03). Differences of maternal age, study design, and ADMA measurement methods did not significantly affect the results. Only two studies evaluated the potential predicting ability of circulating ADMA for subsequent preeclampsia, and retrieved moderate predictive efficacy.

Conclusions

Circulating ADMA is elevated before the development of preeclampsia. Studies are needed to evaluate the predictive efficacy of ADMA for the incidence of preeclampsia.

Dietary supplementation of l-arginine and chromium picolinate in sows during gestation affects the muscle fibre characteristics but not the performance of their progeny

BACKGROUND

The present study investigated the effects of dietary supplementation of l-arginine and chromium picolinate (CrP) in sows during gestation on muscle fibre characteristics, performance and carcass characteristics of their progeny. Sixty healthy sows were randomly divided into four groups as a 2 × 2 factorial experiment design: one group received the control diet, another received the control diet + 10 g kg^-1 l-arginine, the third group received the control diet + 400 ppb CrP, and the fourth group received the control diet + 10 g kg^-1 l-arginine and 400 ppb CrP.

RESULTS

The results showed that sows fed the diet supplemented with CrP produced progeny with higher muscle fibre numbers at birth, weaning and slaughter compared to sows fed the control diet. For mean fibre areas, the same result was found at weaning. For progeny of sows fed diets supplemented with l-arginine, only higher muscle fibre numbers at slaughter was observed. Almost no differences were observed regarding average daily gains, average daily feed intake, gain-to-feed ratios, carcass and meat traits.

CONCLUSION

The results of the present study indicate that dietary supplementation of l-arginine and particularly CrP in sows during gestation alters muscle fibre numbers in their offspring, although not their performance or carcass characteristics. © 2017 Society of Chemical Industry.

Inverse correlation between maternal plasma asymmetric dimethylarginine (ADMA) and birthweight percentile in women with impaired placental perfusion: circulating ADMA as an NO-independent indicator of fetal growth restriction?

L-Arginine (Arg) is the enzymatic precursor of nitric oxide (NO) which has multiple biological functions. Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are endogenous inhibitors of NO. We hypothesized that the ADMA and SDMA have additional biological functions in pregnancy, beyond NO synthesis, and may play a role in the regulation of birthweight (BW). To investigate this issue, we measured the plasma concentration of ADMA, SDMA, Arg and the NO metabolites nitrite and nitrate, at 23-25 weeks of gestation in women with normal placental function (Group 1) and in women with impaired placental perfusion; 19 of these women had normal outcome (Group 2), 14 had a fetus that was growth restricted (Group 3), and 10 women eventually developed preeclampsia (Group 4). BW percentile was found to inversely correlate with maternal plasma ADMA concentration in Group 3 (r = - 0.872, P < 0.001) and in Group 4 (r = - 0.800, P < 0.05). But, BW percentile did not correlate with the maternal plasma concentration of Arg, SDMA, nitrate or nitrite. Our results suggest that maternal plasma ADMA concentration is an important indicator of fetal growth restriction in women with impaired placental perfusion independent of NO.

Flow-mediated dilation and peripheral arterial tonometry are disturbed in preeclampsia and reflect different aspects of endothelial function

Endothelial function and arterial stiffness are known to be altered in preeclamptic pregnancies. Previous studies have shown conflicting results regarding the best technique for assessing vascular function in pregnancy. In this study, we made a comprehensive evaluation of in vivo vascular function [including flow-mediated dilatation (FMD), peripheral arterial tonometry (PAT), and arterial stiffness] in preeclamptic patients and compared them with normal pregnancies. In addition, we assessed the relation between vascular function and systemic inflammation. Fourteen patients with preeclampsia (PE) and 14 healthy pregnant controls were included. Endothelial function was determined by FMD and PAT and arterial stiffness by carotid-femoral pulse-wave velocity and augmentation index. Systemic inflammation was assessed using mean platelet volume (MPV) and neutrophil-lymphocyte ratio (NLR). The reactive hyperemia index, assessed using PAT, is decreased at the third trimester compared with the first trimester in a normal, uncomplicated pregnancy (P = 0.001). Arterial stiffness is significantly higher in PE versus normal pregnancy (P < 0.001). Endothelial function, obtained by FMD, is deteriorated in PE versus normal pregnancy (P = 0.015), whereas endothelial function assessment by PAT is improved in PE versus normal pregnancy (P = 0.001). Systemic inflammation (MPV and NLR) increases during normal pregnancy. FMD and PAT are disturbed in PE. Endothelial function, assessed by FMD and PAT, shows distinct results. This may indicate that measurements with FMD and PAT reflect different aspects of endothelial function and that PAT should not be used as a substitute for FMD as a measure of endothelial function in pregnancy.

Placental Vesicles Carry Active Endothelial Nitric Oxide Synthase and Their Activity is Reduced in Preeclampsia

Supplemental Digital Content is available in the text.

Preeclampsia, a multisystem hypertensive disorder of pregnancy, is associated with increased systemic vascular resistance. Placentae from patients with preeclampsia have reduced levels of endothelial nitric oxide synthase (eNOS) and, thus, less nitric oxide (NO). Syncytiotrophoblast extracellular vesicles (STBEV), comprising microvesicles (STBMV) and exosomes, carry signals from the syncytiotrophoblast to the mother. We hypothesized that STBEV-bound eNOS (STBEV-eNOS), capable of producing NO, are released into the maternal circulation. Dual-lobe ex vivo placental perfusion and differential centrifugation was used to isolate STBEV from preeclampsia (n=8) and normal pregnancies (NP; n=11). Plasma samples of gestational age–matched preeclampsia and NP (n=6) were used to isolate circulating STBMV. STBEV expressed placental alkaline phosphatase, confirming placental origin. STBEV coexpressed eNOS, but not inducible nitric oxide synthase, confirmed using Western blot, flow cytometry, and immunodepletion. STBEV-eNOS produced NO, which was significantly inhibited by N ^G-nitro-l-arginine methyl ester (eNOS inhibitor; P<0.05) but not by N-(3-(aminomethyl) bezyl) acetamidine) (inducible nitric oxide synthase inhibitor). STBEV-eNOS catalytic activity was confirmed by visualizing eNOS dimerization. STBEV-eNOS was more abundant in uterine vein compared with peripheral blood, indicating placental origin. STBEV isolated from preeclampsia-perfused placentae had lower levels of STBEV-eNOS (STBMV; P<0.05) and overall lower NO activity (STBMV, not significant; syncytiotrophoblast extracellular exosomes, P<0.05) compared with those from NP. Circulating plasma STBMV from preeclampsia women had lower STBEV-eNOS expression compared with that from NP women (P<0.01). This is the first observation of functional eNOS expressed on STBEV from NP and preeclampsia placentae, as well as in plasma. The lower STBEV-eNOS NO production seen in preeclampsia may contribute to the decreased NO bioavailability in this disease.

Interplay between Oxidative Stress and Nutrient Sensing Signaling in the Developmental Origins of Cardiovascular Disease

Cardiovascular disease (CVD) presents a global health burden, despite recent advances in management. CVD can originate from early life by so-called “developmental origins of health and disease” (DOHaD). Epidemiological and experimental evidence supports that early-life insults can induce programming of later CVD. Underlying the DOHaD concept, early intervention may offset programming process to prevent the development of CVD, namely reprogramming. Oxidative stress and nutrient sensing signals have been considered to be major mechanisms of cardiovascular programming, while the interplay between these two mechanisms have not been examined in detail. This review summarizes current evidence that supports the link between oxidative stress and nutrient sensing signaling to cardiovascular programming, with an emphasis on the l-arginine–asymmetric dimethylarginine (ADMA)–nitric oxide (NO) pathway. This review provides an overview of evidence from human studies supporting fetal programming of CVD, insight from animal models of cardiovascular programming and oxidative stress, impact of the l-arginine–ADMA–NO pathway in cardiovascular programming, the crosstalk between l-arginine metabolism and nutrient sensing signals, and application of reprogramming interventions to prevent the programming of CVD. A greater understanding of the mechanisms underlying cardiovascular programming is essential to developing early reprogramming interventions to combat the globally growing epidemic of CVD.

The role of L-arginine/L-homoarginine/nitric oxide pathway for aortic distensibility and intima-media thickness in stroke patients

Asymmetric dimethylarginine (ADMA) and L-homoarginine (hArg) are L-arginine (Arg) metabolites derived from different pathways. Protein arginine N-methyltransferase (PRMT) and subsequent proteolysis of proteins containing methylarginine residues release ADMA. Arginine:glycine amidinotransferase (AGAT) converts Arg to hArg and guanidinoacetate (GAA). While high concentrations of ADMA and low concentrations of hArg in the blood have been established as cardiovascular risk markers, the cardiovascular relevance of GAA is still unexplored. Arg and hArg are substrates and ADMA is an inhibitor of nitric oxide (NO) synthase (NOS). The cardiovascular effects of ADMA and hArg have been related to NO, a potent endogenous vasodilator. ADMA and hArg are considered to exert additional, not yet explored, presumably NO-unrelated effects and to act antagonistically in the renal and cardiovascular systems. Although the physiological role of Arg, ADMA, hArg and NO for endothelial function in small- and medium-sized arteries has been intensively studied in the past, the clinical relevance of aortic wall remodeling still remains unclear. Here, we evaluated potential relation between aortic distensibility (AD) or aortic intima-media thickness (aIMT) and circulating ADMA, hArg, GAA, and the NO metabolites nitrite and nitrate in the plasma of 78 patients (24 females, 54 males; aged 59 ± 14 years) with recent ischemic stroke or transient ischemic attack (TIA). All biochemical parameters were determined by stable-isotope dilution gas chromatography-mass spectrometry. AD and aIMT were measured by transesophageal echocardiography. Arg, hArg, ADMA and GAA median plasma concentrations (µM) were determined to be 61, 1.43, 0.50 and 2.16, respectively. hArg, ADMA and GAA correlated closely with Arg. Nitrite, nitrate and creatinine median plasma concentrations (µM) were 2.49, 48.7, and 84.1, respectively. Neither AD (2.61 vs. 1.85 10^-6 × cm² × dyn^-1, P = 0.064) nor aIMT (1.25 vs. 1.13 mm, P = 0.596) differed between females and males. The hArg/ADMA molar ratio (r = -0.351, P = 0.009), nitrate (r = 0.364, P = 0.007) and nitrite (r = 0.329, P = 0.015) correlated with aIMT but not with AD. Arg, hArg, ADMA and GAA correlated with aIMT but not with AD. The results demonstrate a strong relation between the Arg/NO pathway and aortic atherosclerosis but not with AD suggesting different mechanisms underlying the two aspects of aortic wall remodeling.

Comprehensive analysis of the L-arginine/L-homoarginine/nitric oxide pathway in preterm neonates: potential roles for homoarginine and asymmetric dimethylarginine in foetal growth

L-Arginine (Arg) and L-homoarginine (hArg) are precursors of nitric oxide (NO), a signalling molecule with multiple important roles in human organism. In the circulation of adults, high concentrations of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) and low concentrations of hArg emerged as cardiovascular risk factors. Yet, the importance of the Arg/hArg/NO pathway, especially of hArg and ADMA, in preterm neonates is little understood. We comprehensively investigated the Arg/hArg/NO pathway in 106 healthy preterm infants (51 boys, 55 girls) aged between 23 + 6 and 36 + 1 gestational weeks. Babies were divided into two groups: group I consisted of 31 babies with a gestational age of 23 + 6 - 29 + 6 weeks; group II comprised 75 children with a gestational age of 30 + 0 - 36 + 1 weeks. Plasma and urine concentrations of ADMA, SDMA, hArg, Arg, dimethylamine (DMA) which is the major urinary ADMA metabolite, as well as of nitrite and nitrate, the major NO metabolites, were determined by GC-MS and GC-MS/MS methods. ADMA and hArg plasma levels, but not the hArg/ADMA molar ratio, were significantly higher in group II than in group I: 895 ± 166 nM vs. 774 ± 164 nM (P = 0.001) for ADMA and 0.56 ± 0.04 µM vs. 0.48 ± 0.08 µM (P = 0.010) for hArg. There was no statistical difference between the groups with regard to urinary ADMA (12.2 ± 4.6 vs 12.8 ± 3.6 µmol/mmol creatinine; P = 0.61) and urinary SDMA. Urinary hArg, ADMA, SDMA correlated tightly with each other. Urinary excretion of DMA was slightly higher in group I compared to group II: 282 ± 44 vs. 247 ± 35 µmol/mmol creatinine (P = 0.004). The DMA/ADMA molar ratio in urine was tendentiously higher in neonates of group I compared to group II: 27 ± 13 vs. 20 ± 5 (P = 0.065). There were no differences between the groups with respect to Arg in plasma and to nitrite and nitrate in plasma and urine. In preterm neonates, ADMA and hArg biosynthesis increases with gestational age without remarkable changes in the hArg/ADMA ratio or NO biosynthesis. Our study suggests that ADMA and hArg are involved in foetal growth.

Molecular hydrogen ameliorates several characteristics of preeclampsia in the Reduced Uterine Perfusion Pressure (RUPP) rat model

Oxidative stress plays an important role in the pathogenesis of preeclampsia. Recently, molecular hydrogen (H₂) has been shown to have therapeutic potential in various oxidative stress-related diseases. The aim of this study is to investigate the effect of H₂ on preeclampsia. We used the reduced utero-placental perfusion pressure (RUPP) rat model, which has been widely used as a model of preeclampsia. H₂ water (HW) was administered orally ad libitum in RUPP rats from gestational day (GD) 12-19, starting 2 days before RUPP procedure. On GD19, mean arterial pressure (MAP) was measured, and samples were collected. Maternal administration of HW significantly decreased MAP, and increased fetal and placental weight in RUPP rats. The increased levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and diacron reactive oxygen metabolites as a biomarker of reactive oxygen species in maternal blood were decreased by HW administration. However, vascular endothelial growth factor level in maternal blood was increased by HW administration. Proteinuria, and histological findings in kidney were improved by HW administration. In addition, the effects of H₂ on placental villi were examined by using a trophoblast cell line (BeWo) and villous explants from the placental tissue of women with or without preeclampsia. H₂ significantly attenuated hydrogen peroxide-induced sFlt-1 expression, but could not reduce the expression induced by hypoxia in BeWo cells. H₂ significantly attenuated sFlt-1 expression in villous explants from women with preeclampsia, but not affected them from normotensive pregnancy. The prophylactic administration of H₂ attenuated placental ischemia-induced hypertension, angiogenic imbalance, and oxidative stress. These results support the theory that H₂ has a potential benefit in the prevention of preeclampsia.

Whole-body synthesis of L-homoarginine in pigs and rats supplemented with L-arginine

Recent studies suggest an important role for L-homoarginine in cardiovascular, hepatic and neurological functions, as well as the regulation of glucose metabolism. However, little is known about whole-body L-homoarginine synthesis or its response to dietary L-arginine intake in animals. Four series of experiments were conducted to determine L-homoarginine synthesis and catabolism in pigs and rats. In Experiment 1, male and female pigs were fed a corn- and soybean meal-based diet supplemented with 0.0-2.42 % L-arginine-HCl. In Experiment 2, male and female rats were fed a casein-based diet, while receiving drinking water containing supplemental L-arginine-HCl to provide 0.0-3.6 g L-arginine/kg body-weight/day. In both experiments, urine collected from the animals for 24 h was analyzed for L-homoarginine and related metabolites. In Experiment 3, pigs and rats received a single oral dose of 1 or 10 mg L-homoarginine/kg body-weight, respectively, and their urine was collected for 24 h for analyses of L-homoarginine and related substances. In Experiment 4, slices of pig and rat tissues (including liver, brain, kidney, heart, and skeletal-muscle) were incubated for 1 h in Krebs-bicarbonate buffer containing 5 or 50 µM L-homoarginine. Our results indicated that: (a) animal tissues did not degrade L-homoarginine in the presence of physiological concentrations of other amino-acids; (b) 95-96 % of orally administered L-homoarginine was recovered in urine; (c) L-homoarginine was quantitatively a minor product of L-arginineg catabolism in the body; and (d) dietary L-arginine supplementation dose-dependently increased whole-body L-homoarginine synthesis. These novel findings provide a new framework for future studies of L-homoarginine metabolism and physiology in animals and humans.

Mechanism of vascular dysfunction due to circulating factors in women with pre-eclampsia

Circulating factors in the plasma of pre-eclamptic women contribute to vascular dysfunction by increasing oxidative stress, which is associated with a reduction in nitric oxide bioavailability and an increase in prostaglandin H synthase-dependent vasoconstrictors.