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Fetal and Pediatric Pathology
ISSN: 1551-3815 (Print) 1551-3823 (Online) Journal homepage: https://www.tandfonline.com/loi/ipdp20
Dynamic Thiol/Disulfide Homeostasis in Predicting
Adverse Neonatal Outcomes in Fetal Growth
Restriction
Sibel Ozler, Efser Oztas, Basak Gumus Guler, Ozcan Erel, Ali Turhan Caglar,
Merve Ergin & Nuri Danisman
To cite this article: Sibel Ozler, Efser Oztas, Basak Gumus Guler, Ozcan Erel, Ali Turhan Caglar, Merve Ergin & Nuri Danisman (2020) Dynamic Thiol/Disulfide Homeostasis in Predicting Adverse Neonatal Outcomes in Fetal Growth Restriction, Fetal and Pediatric Pathology, 39:2, 132-144, DOI: 10.1080/15513815.2019.1644686
To link to this article: https://doi.org/10.1080/15513815.2019.1644686
Published online: 30 Jul 2019.
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Dynamic Thiol/Disulfide Homeostasis in Predicting Adverse
Neonatal Outcomes in Fetal Growth Restriction
Sibel Ozlera, Efser Oztasb, Basak Gumus Gulerc, Ozcan Ereld , Ali Turhan Caglare, Merve Erginf, and Nuri Danismang
a
Department of Perinatology in Selcuk University Faculty of Medicine, Konya, Turkey;bDepartment of Perinatology in Eskis¸ehir City Hospital, Eskisehir, Turkey;cDepartment of Health Sciences in Istinye
University, Istanbul, Turkey;dDepartment of Clinical Biochemistry, Faculty of Medicine, Yildirim Beyazit
University, Ankara, Turkey;eDepartment of Pathology in Zekai Tahir Burak Women’s Health Education and Research Hospital, Ankara, Turkey;fDepartment of Clinical Biochemistry, Gaziantep 25 Aralik State
Hospital, Gaziantep, Turkey,gDepartment of Perinatology in Acıbadem Acıbadem University Medical School, Istanbul, Turkey
ABSTRACT
Aim: The main aim of this study was to investigate thiol/disulfide homeostasis associated with fetal growth restriction (FGR) and to evaluate whether alterations are predictive for adverse neonatal out-comes. Methods: 273 pregnant women (77 with FGR and 196 with normal fetal growth) were enrolled in this prospective case–control study. Results: Native thiol and total thiol were decreased in FGR compared to the control group (p < .001; p < .001). Decreased levels of maternal serum native and total thiol were significantly associated with adverse neonatal outcomes in FGR (OR: 0.983, 95% CI 0.976–0.991, p < .001; OR: 0.983, 95% CI 0.976–0.991, p < .001). Decreased maternal serum total thiol levels were the only significantly associated risk factor with adverse neonatal outcomes in FGR (OR: 0.981, 95% CI 0.963–1.000, p ¼ .046). Conclusion: The decrease in the antioxidants of thiol/disulfide mechanism may be related to the development of both FGR and adverse neonatal outcome in FGR.
ARTICLE HISTORY
Received 28 April 2019 Revised 24 June 2019 Accepted 1 July 2019
KEYWORDS
Fetal growth restriction; dynamic thiol disulfide homeostasis; adverse neonatal outcomes
Introduction
Fetal growth restriction (FGR) refers to those fetuses whose estimated weights are less than the weight of 10th centile for the population of the same gestational age. Many fac-tors of maternal, fetal, and placental origin are implicated in the etiopathogenesis [1]. FGR is related to increased risk of intrauterine fetal demise, neonatal morbidity, and mortality [2]. The risks of low APGAR score (<3) at the 5th minute, intubation in the
delivery room, low pH of umbilical artery blood (7), seizure in the first 24 hours, sep-sis, and mortality rate in the first 28 days were higher in the neonates with birth weight lower 25th percentile for their ages, when compared to the ones with weight between 25th and 75th percentiles [3].
For these fetuses, prolongation of the intrauterine period increases the mean duration of exposure to oxidative stress and may end in complications such as deterioration of CONTACTSibel Ozler sibel2ozler@gmail.com Faculty of Medicine, Selc¸uk University, Konya 42050, Turkey. Color versions of one or more of the figures in the article can be found online atwww.tandfonline.com/ipdp. ß 2019 Taylor & Francis Group, LLC
2020, VOL. 39, NO. 2, 132–144
placental and fetal blood flow, chronic hypoxia resulting in oligohydramnios, and fetal distress [4]. The most sensitive markers of oxidative stress during intrauterine life for the fetuses with FGR are the impairments in the blood flow of fetus (umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV)) [5] and deterioration of biophysical variables [6]. These parameters are also predictive for fetal distress, the need for emergent cesarean delivery, and need for neonatal intensive care unit admission [7]. The neonatal outcome of fetuses with birth weight below the 10th centile of their gesta-tional ages is worse compared to those with normal birth weights, even if they have no deterioration in their Doppler parameters [8]. In the light of these findings, it would be beneficial to predict the early effects of intrauterine fetal hypoxia in fetuses with FGR but with normal Doppler values and biophysical profile score more than 6, to prevent the adverse neonatal outcome.
Dynamic thiol disulfide homeostasis, which can easily and inexpensively be evaluated by a spectrophotometric method described by Erel et al. is a marker of oxidative stress [9]. The whole of the oxidative and anti-oxidative parameters can be evaluated, and its reliability has been demonstrated with many studies [10,11].
In the present study, we aimed to determine maternal serum dynamic thiol disulfide homeostasis levels in patients with FGR and to compare these levels with the levels in healthy controls. We examined if it could help to discriminate the healthy fetuses from the ones with FGR when the Doppler measurements, biophysical profile scores, and amniotic fluid levels were within normal ranges. We also evaluated this to determine if the oxidative status was effective in predicting adverse neonatal outcome.
Material and methods
Design and study population
A prospective case-control study was performed between August 2013 and January 2016 in the Perinatology Department of Zekai Tahir Burak Women’s Health Education and Training Hospital. A total of 273 participants were included in the study. Pregnant women were diagnosed with FGR prenatally (fetuses with EFW and birth weights less than the 10th centile of their gestational ages were accepted as growth restricted) [1]. The standard EFW was calculated using the Hadlock formula, which incorporates the fetal bi-parietal diameter, head circumference, abdominal circumference, and femur length measured by grey-scale ultrasonography [12].The patients with EFW less than the 10th centile for the appropriate gestational ages were followed for the birth weights of their newborns. The confirmation of FGR was based on birth weight. The control group consisted of healthy pregnant women whose EFW and the birth weights of the newborns were in between 10th and 90th centiles for their gestational weeks.
The patients of the control group who had malpresented fetus, cephalopelvic dis-proportion or previous uterine surgery delivered with cesarean operation; and the rest were vaginally delivered at term. The study group was composed of patients with FGR in the late preterm weeks (late onset FGR), during the follow-up period their biophysical profile scores were more than 6, with no sign of placental insufficiency (like oligohydramnios) [4].
Patients were excluded if any of the following criteria were present: modified bio-physical profile score< 6, being in active labor stage, impaired fetal and/or placental Doppler parameters (impaired MCA or UA flow, absent or reversed end-diastolic blood flow, cerebro-placental ratio< 1) [13, 14] oligohydramnios, abnormal nonstress test (NST), delivery of infant with birth weight more than the 10th centile for the gestational age, preeclampsia, gestational hypertension, preterm premature rupture of membranes (PPROM), gestational diabetes, type 1 diabetes, autoimmune diseases (systemic lupus erythematosus, hypothyroidism, hyperthyroidism), gestational cholestasis, acute trauma leading oxidative stress, seizure, eclampsia, sepsis, chronic kidney or liver disease, pla-cental adhesive disorder (placenta previa totalis), fetuses diagnosed to have physical or cytogenetic abnormality, twin pregnancies.
All participants provided written informed consent. The study protocol was per-formed according to the principles of Declaration of Helsinki and was approved by the local Ethical Committee of our hospital (approval date: 20.11.2015).
All participants of the study were evaluated at the initial admission. Clinical examin-ation was performed and anthropometric measurements, as well as the previous obstet-ric and medical history, were recorded. Gestational age was calculated according to the last menstrual period and verified by ultrasonography. The blood samples were collected from the participants who are not in labor, and who had a modified biophysical profile more than 6 in the late preterm period (after 34th gestational week). Blood samples were obtained by venipuncture and processed within 30 minutes–1 hour after with-drawal, by centrifugation at 5000 revolutions/minute for 15 minutes. All serum samples were stored at80C until the day of analysis.
Measurement of maternal serum thiol/disulfide homeostasis levels
Thiol/disulfide homeostasis was determined with a unique spectrophotometric technique described previously by Erel and Neselioglu [9]. This assay uses sodium borohydride (NaBH4) to reduce the disulfide bonds to the thiol groups. The sum of existing thiol groups and reduced thiol groups provide the overall thiol. The NaBH4 residuals which do not seem to be used are completely removed by formaldehyde. Hence, the additional reduction of 5,50-dithio-bis-(2-nitrobenzoic acid) (DTNB) is prevented. The native thiol is measured using a modified Ellman’s reagent. Half of the difference between the total thiols and native thiols provides the dynamic disulfide amount [Disulfide¼ (overall thiol-native thiol)/2].The native thiols (–SH) and total thiols (–SH þ –SS) were deter-mined, disulfide (–SS) amounts, disulfide/native thiol percent ratios (–SS/–SH), disul-fide/total thiol percent ratios (–SS/–SHþ–SS) and native thiol/total thiol percent ratios (–SH/–SHþ–SS) were calculated. Measurements were obtained by using an automated clinical chemistry analyzer (Cobas 501; Roche Diagnostics, Mannheim, Germany) and also the results were conferred as mmol/l.
Adverse neonatal outcomes
Presence of one of the following criteria was accepted as an adverse neonatal outcome: (1) APGAR score< 7 in 5 minutes, (2) pH of blood sampled from umbilical artery < 7.0,
(3) need for intubation in the first 24 hours after delivery, (4) meconium aspiration, (5) presence of hypoglycemia, hyperbilirubinemia, hypothermia, intraventricular hemor-rhage, necrotizing enterocolitis, seizures, sepsis, respiratory distress syndrome, or neo-natal death in the first 28 days postpartum [1,7].
Statistical analysis
Data analysis was performed by using SPSS for Windows, version 22 (SPSS Inc., Chicago, IL, United States). The Kolmogorov Smirnov test was used to test whether or not continuous variables were normally distributed. Homogeneity of variances was eval-uated by the Levene test. Continuous variables were shown as mean ± standard deviation (SD). Mean variations between FGR and control groups were compared by Student’s t-test. The best cutoff points of the clinical measurements that discriminated FGR were evaluated by receiver operating characteristic (ROC) analysis calculating area under the curve (AUC) as giving the maximum total of sensitivity and specificity for the signifi-cant test. Sensitivity and specificity values were also calculated at the most effective cut-off point for every clinical and laboratory measurement. Multivariate logistic regression analysis was used to determine if relationships between FGR, adverse neonatal outcome and Thiol/disulfide homeostasis were present. Any variable whose univariable test had a p-value< 0.05 was accepted as a candidate for the multivariable model in conjunction with Thiol/disulfide homeostasis variables. A p-value < 0.05 was considered as significant.
Results
The baseline characteristics, maternal serum thiol/disulfide homeostasis levels of the groups
A total of 273 patients and controls were enrolled in the study (77 FGR and 196 healthy controls). The baseline maternal and fetal characteristics of FGR and controls are given in Table 1. There was no significant difference for the delivery week between the groups. The mean maternal age difference between the groups was significant (p ¼ .007). Pregestational body mass index (BMI) and weight gain during pregnancy were significantly higher in the FGR group when compared to the control group (p ¼ .014 and p ¼ .025). EFW was significantly lower in the FGR group (p < .001) (Table 1).
Table 1. Clinical and laboratory data of FGR and Controls.
FGR n ¼ 77 Control n ¼ 196 p value
Maternal Age (years) 30.43 ± 6.04 28.36 ± 5.53 .007
PBMI (kg/m2) 30.39 ± 4.51 29.00 ± 4.03 .014 Weight Gain (kg) 12.33 ± 5.13 10.76 ± 5.24 .025 Gravidy Primigravidy 28 (36.4%) 48 (24.5%) .036 Multigravidy 49 (63.6%) 148 (75.5%) Birth week 37.37 ± 3.04 37.82 ± 1.15 .075 EFW (gr) 2203.89 ± 861.76 3281.28 ± 448.73 <.001
Results were analyzed by independent sample t-test. (mean ± standard deviation). p-value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text, and Pearson chi-square test, percent (%), PBMI: Pre-gestational, Body Mass Index, EFW: Estimated Fetal Weight.
The maternal serum –SH and –SHþ–SS levels were significantly lower in the FGR group than the control groups (288.58 ± 62.57mmol/l vs. 332.93 ± 67.55 mmol/l, p < .001 and 316.92 ± 63.55mmol/l vs. 360.80 ± 66.94 mmol/l, p < .001).The maternal serum –SS/ SH and –SS/–SHþ–SS levels in the FGR group were significantly higher than the con-trol group (5.12 ± 1.79 vs. 4.44 ± 2.23, p ¼ .017 and 4.60 ± 1.44 vs. 4.00 ± 1.79, p ¼ .010). The maternal serum –SH/–SHþ–SS levels were lower in FGR group than the control group (90.79 ± 2.89 vs. 91.98 ± 3.59, p ¼ .010). There was no statistically significant dif-ference for –SS between FGR and control groups (14.17 ± 4.04 mmol/l vs. 13.87 ± 5.76mmol/l, p ¼ .682) (Table 2).
The maternal serum–SH and –SHþ–SS levels were significantly lower in the FGR group with adverse neonatal outcomes, when compared to the ones with non-adverse neonatal outcomes in the same FGR group (261.27 ± 56.45mmol/l vs. 310.17 ± 59.15 mmol/l, p < .001 and 290.31 ± 58.19mmol/l vs. 337.97 ± 60.17 mmol/l, p < .001). The maternal serum –SS/SH and -SS/-SHþ-SS levels were significantly higher in FGR group with adverse neonatal out-comes, when compared to the ones with non-adverse neonatal outcomes in FGR group (5.64 ± 1.80 vs. 4.71 ± 1.69, p ¼ .023 and 5.02 ± 1.42 vs. 4.26 ± 1.38, p ¼ .021). The maternal serum–SH/–SHþ–SS levels were lower in the FGR group with adverse neonatal outcomes than the FGR group with non-adverse neonatal outcomes (89.94 ± 2.85 vs. 91.46 ± 2.77, p ¼ .021). There was no statistically significant difference for -SS between in the FGR group with adverse neonatal outcomes and FGR group with non-adverse neonatal outcomes (14.77 ± 3.95mmol/l vs. 13.70 ± 4.10 mmol/l, p ¼ .252) (Table 3).
Serum thiol/disulfide homeostasis levels were reevaluated with ROC analysis in FGR; cutoff levels were determined, and AUC were calculated (Fig. 1). According to the ROC analysis performed for the predictive value of –SH, –SHþ–SS, –SS/SH, –SS/–SHþ–SS and –SH/–SHþ–SS levels for FGR, the AUC were 0.691 (95% CI 0.624–0.759; p < .001),
Table 2. Thiol/disulfide homeostasis of FGR and control group.
FGR Control p value –SH (mmol/l) 288.58 ± 62.57 332.93 ± 67.55 <.001 –SH 1 –SS(mmol/l) 316.92 ± 63.55 360.80 ± 66.94 <.001 –SS(mmol/l) 14.17 ± 4.04 13.87 ± 5.76 .682 –SS/–SH (%) 5.12 ± 1.79 4.44 ± 2.23 .017 –SS/–SH 1 –SS (%) 4.60 ± 1.44 4.00 ± 1.79 .010 –SH/–SH 1 –SS (%) 90.79 ± 2.89 91.98 ± 3.59 .010
Results were analyzed by independent samplet-test. (mean ± standard deviation). p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text. FGR: Fetal Growth Restriction, – SH: Native Thiol,–SSþ–SH: total thiol–SS: Dynamic disulfide amount.
Table 3. Comparison of Thiol/disulfide homeostasis of FGR groups with and without adverse neonatal outcomes.
FGR þ adverse neonatal outcomes FGR þ non adverse neonatal outcomes p value
–SH (mmol/l) 261.27 ± 56.45 310.17 ± 59.15 <.001 –SH 1 –SS(mmol/l) 290.31 ± 58.19 337.97 ± 60.17 .001 –SS(mmol/l) 14.77 ± 3.95 13.70 ± 4.10 .252 –SS/–SH (%) 5.64 ± 1.80 4.71 ± 1.69 .023 –SS/–SH 1 –SS (%) 5.02 ± 1.42 4.26 ± 1.38 .021 –SH/–SH 1 –SS (%) 89.94 ± 2.85 91.46 ± 2.77 .021
Results were analyzed by independent samplet-test. (mean ± standard deviation). p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text. FGR: Fetal Growth Restriction, – SH: Native Thiol,–SSþ–SH: total thiol–SS: Dynamic disulfide amount.
Figure 1. ROC curve of Thiol/disulfide homeostasis in FGR. (a) ROC curve of native thiol, total thiol and–SS/SH in FGR. (b) ROC curve of –SS/SH þ–SS and –SH/–SH þ –SS in FGR
0.689 (95% CI 0.621–0.757; p < .001), 0.380 (95% CI 0.310–0.449; p ¼ .002), 0.380 (95% CI 0.310–0.449; p ¼ .002) and 0.620 (95% CI 0.551–0.690; p ¼ .002). The best –SH, –SHþ–SS, –SS/SH and –SS/–SHþ–SS cutoff values associated with FGR were 296.10mmol/l (68% specificity and 67% sensitivity), 280.40 mmol/l (68% specificity and 67% sensitivity), 4.56 (68% specificity and 48% sensitivity), 4.18 (68% specificity and 48% sensitivity) and 91.64 (68% specificity and 48% sensitivity) (Table 4).
Serum thiol/disulfide homeostasis levels were reevaluated with ROC analysis with adverse neonatal outcomes in FGR; cutoff levels were determined, and AUC were calcu-lated (Fig. 2). According to the ROC analysis performed for the predictive value of –SH, –SHþ–SS, –SS/SH, –SS/–SHþ–SS and –SH/–SHþ–SS levels for FGR, the AUC were 0.717 (95% CI: 0.603–0.831; p ¼ .001), 0.711 (95% CI: 0.596–0.826; p ¼ .002), 0.344 (95% CI: 0.223–0.465; p ¼ .019), 0.344 (95% CI: 0.223–0.465; p ¼ .019) and 0.656 (95% CI: 0.535–0.777; p ¼ .019). The best –SH, –SHþ–SS, –SS/SH, –SS/–SHþ–SS and –SH/ –SHþ–SS cutoff values associated with adverse neonatal outcomes FGR were 285.90mmol/l (68% specificity and 67% sensitivity), 302.00 mmol/l (68% specificity and 61% sensitivity), 5.12 (68% specificity and 61% sensitivity), 4.65 (65% specificity and 61% sensitivity) and 90.70 (65% specificity and 61% sensitivity) (Table 5).
Logistic regression analysis of the possible risk factors for FGR and adverse neonatal outcomes in FGR
All statistically significant parameters according to the univariate analysis were further evaluated by multivariate logistic regression analysis (Table 6 and Table 7). Based on the laboratory parameters, only decreased maternal serum –SH and –SHþ–SS levels were significantly associated with adverse neonatal outcomes in FGR (OR: 0.983, 95% CI: 0.976–0.991, p < .001 and OR: 0.983, 95% CI: 0.976–0.991, p < .001) (Table 4). Decreased maternal serum –SH and –SHþ–SS levels and increased maternal age were significantly associated with FGR (OR: 0.988, 95% CI 0.983–0.993, p < .001, OR: 0.988, 95% CI: 0.983–0.993, p < .001 and OR:1.092, 95% CI 1.037–1.149, p ¼ .001, respect-ively) (Table 7).
Logistic regression analysis of the possible risk factors for adverse neonatal outcomes in FGR
All statistically significant parameters according to the univariate analysis were further evaluated by multivariate logistic regression analysis (Table 8). Based on the laboratory parameters, a decreased maternal serum–SHþ–SS level was the only significantly
Table 4. Best cutoff value, sensitivity, specificity, and AUC of thiol/disulfide homeostasis in FGR. Cut off Specificity % Sensitivity % AUC (95 %Cl) p value
–SH (mmol/l) 296.10 68 67 0.691 (0.624–0.759) <.001
–SH 1 –SS(mmol/l) 280.40 68 67 0.689 (0.621–0.757) <.001
–SS/–SH % 4.56 68 48 0.380 (0.310–0.449) .002
–SS/–SH 1 –SS% 4.18 68 48 0.380 (0.310–0.449) .002
–SH/–SH 1 –SS % 91.64 68 48 0.620 (0.551-0.690) .002
AUC; Area under curve, p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text. FGR: Fetal Growth Restriction– SH: Native Thiol, –SSþ–SH: total thiol.
Figure 2. ROC curve of Thiol/disulfide homeostasis in FGR with adverse neonatal outcomes. (a) ROC curve of native thiol, total thiol and–SS/SH in FGR with adverse neonatal outcomes. (b) ROC curve of –SS/SH þ–SS and –SH/–SH þ –SS in FGR with adverse neonatal outcomes
associated risk factor with adverse neonatal outcomes in FGR (OR: 0.981, 95% CI: 0.963–1.000, p ¼ .046) (Table 8).
Discussion
Native thiol (–SH), total thiol (–SHþ–SS) and –SH/–SHþ–SS, which are known to have antioxidative effects in the dynamic Thiol/disulfide homeostasis, were significantly lower in FGR than the control group in our study. We also observed increased oxidative stress
Table 5. Best cutoff value, sensitivity, specificity and AUC of thiol/disulfide homeostasis in FGR with adverse neonatal outcomes.
Cut off Specificity % Sensitivity % AUC (95 %Cl) p value
–SH (mmol/l) 285.90 68 67 0.717 (0.603–0.831) .001
–SH 1 –SS(mmol/l) 302.00 68 61 0.711 (0.596–0.826) .002
–SS/–SH % 5.12 68 61 0.344 (0.223–0.465) .019
–SS/–SH 1 –SS% 4.65 65 61 0.344 (0.223–0.465) .019
–SH/–SH 1 –SS % 90.70 65 61 0.656 (0.535–0.777) .019
AUC; Area under curve, p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text. FGR: Fetal Growth Restriction– SH: Native Thiol, –SSþ–SH: total thiol.
Table 6. Multiple regression analyses of thiol/disulfide homeostasis related to adverse neonatal outcome.
Adverse Neonatal Outcome
Univariate Multivariate
Odds Ratio (95%Cl) p value Odds Ratio (95%Cl) p value Maternal Age (years) 0.985 (0.926–1.048) .640
PBMI (kg/m2) 1.017 (0.937–1.104) .690 Weight Gain (kg) 1.048 (0.980–1.120) .168 –SH (mmol/l) 0.984 (0.978–0.990) <.001 0.983 (0.976–0.991) <.001 –SH 1 –SS(mmol/l) 0.984 (0.978–0.990) <.001 0.983 (0.976–0.991) <.001 –SS(mmol/l) 1.027 (0.965–1.094) .404 –SS/–SH % 1.236 (1.068–1.431) .004 –SS/–SH 1 –SS% 1.332 (1.104–1.608) .003 –SH/–SH 1 –SS % 0.866 (0.789–0.952) .003
p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text, ns; non-significance, EFW; Estimated Fetal Weight, – SH; Native Thiol, –SSþ–SH; total thiol –SS; Dynamic disulfide amount.
Table 7. Multiple regression analyses of thiol/disulfide homeostasis related to FGR. FGR
Univariate Multivariate
Odds Ratio (95%Cl) p value Odds Ratio (95%Cl) p value Maternal Age (years) 1.065 (1.016–1.116) .008 1.092 (1.037–1.149) .001 PBMI (kg/m2) 1.081 (1.015–1.151) .015 Weight Gain (kg) 1.059 (1.007–1.115) .027 –SH (mmol/l) 0.990 (0.986–0.994) <.001 0.988 (0.983–0.993) <.001 –SH 1 –SS(mmol/l) 0.990 (0.986–0.994) <.001 0.988 (0.983–0.993) <.001 –SS(mmol/l) 1.010 (0.962–1.061) .681 –SS/–SH % 1.155 (1.024–1.303) .019 –SS/–SH 1 –SS% 1.216 (1.045–1.415) .011 –SH/–SH 1 –SS % 0.907 (0.841–0.978) .011
p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text, ns; non-significance, EFW; Estimated Fetal Weight, – SH; Native Thiol, –SSþ–SH; total thiol –SS; Dynamic disul-fide amount.
markers, –SS/–SH and –SS/–SHþ–SS ratio, in the FGR group, when compared to the control group.
Fetuses with FGR are exposed to hypoxia in-utero life and demonstrate altered vaso-constrictor and vasodilator mechanisms in addition to vascular remodeling in the pla-centa [15]. Uteroplacental insufficiency, characterized by attenuated placental perfusion, is one of the important causes of FGR [16]. Oxidative stress is associated with FGR [17]. Oxidative stress results from redox imbalance caused by either overproduction of reactive oxygen species (ROS) or diminished anti-oxidative activities. Hypoxia occurs due to the inefficient perfusion in the intervillous spaces in placental insufficiency, and increases apoptosis in placental trophoblasts. Reactive oxygen radicals [18–20] increase due to the apoptosis of trophoblasts. This may contribute to the oxidative stress in both fetus and the mother. The increase of oxidative stress in both maternal and fetal com-partments has been shown in FGR. Studies in the mothers of growth-restricted fetuses have shown increased plasma protein carbonyls and reduced plasma total antioxidant capacity during pregnancy [21], indicating maternal oxidative stress. Biri et al. reported that malondialdehyde (MDA) and xanthine oxidase levels were higher in the maternal plasma, umbilical cord plasma, and placental tissues of patients of FGR compared to controls [22]. Gupta et al. showed that increased levels of oxidative stress markers superoxide dismutase, catalase, and serum MDA; and decreased levels of antioxidative markers resulted in a decreased birth weight of the newborn [23]. Apoptosis after pla-cental hypoxia was demonstrated to produce plapla-cental oxidative stress and caused an increase in cardiovascular disease risk in late-term FGR [24]. The free radical damage, which was caused by oxidative stress in the fetal and neonatal period in the fetuses of smoking mothers, was found to trigger metabolic diseases, other fetal morbidities, and fetal mortality [25]. In light of the mentioned studies, we may accept the importance of oxidative stress in the development of adverse results in the prenatal and neonatal period, in FGR patients. Oxidative stress and antioxidant defense mechanisms are involved in the mechanism maintaining the oxidative balance. It is accepted that dynamic thiol groups are modulated with thiol-disulfide exchange mechanisms at a cer-tain stage in such cases as protein synthesis, protein secretion, regulation of cell struc-ture, differentiation, caspase-mediated cell death and anti-oxidant defense. [26] Thiol is
Table 8. Multiple regression analyses of thiol/disulfide homeostasis related to adverse neonatal outcome in FGR.
Adverse Neonatal Outcome
Univariate Multivariate
Odds Ratio (95%Cl) p value Odds Ratio (95%Cl) p value Maternal Age (years) 0.918 (0.848–0.995) .038 0.925 (0.848–1.009) .079 PBMI (kg/m2) 0.934 (0.843–1.036) .199 Weight Gain (kg) 1.011 (0.926–1.104) .804 –SH (mmol/l) 0.990 (0.982–0.998) .013 1.005 (0.988–1.023) .577 –SH 1 –SS(mmol/l) 0.986 (0.977–0.995) .002 0.981 (0.963–1.000) .046 –SS(mmol/l) 1.069 (0.954–1.197) .251 –SS/–SH % 1.358 (1.033–1.785) .028 0.115 (0–2.345) .579 –SS/–SH 1 –SS% 1.470 (1.047–2.064) .026 1.992 (0.001–2.695) .538 –SH/–SH 1 –SS % 0.825 (0.696–0.977) .026 1.992 (0.001–2.695) .538 p value; statistical significance, <.05 statistically significant. Statistically, significant p values are marked as bold text, ns;
non-significance, EFW; Estimated Fetal Weight, – SH; Native Thiol, –SSþ–SH; total thiol –SS; Dynamic disulfide amount.
a very important member of the antioxidant system [27]. The anti-oxidative stress markers, native and total thiol, are decreased in FGR pregnant mothers when compared to pregnant controls without FGR; whereas oxidative stress markers like disulfide are not different when the groups are compared [28]. We previously observed decreased native and total thiol levels, and increased disulfide in the patients of preeclampsia com-pared to healthy pregnant controls [29]. We also demonstrated that adverse perinatal outcome in obese patients with gestational diabetes was related to decreased native and total thiol, and increased disulfide levels in the cord blood [10].
In the present study, we observed decreased levels of native and total thiol in mater-nal serum; increased oxidative stress ratios (–SS/–SH and –SS/–SH þ – SS) in FGR, and these dynamic Thiol/disulfide hemostasis markers were associated with adverse neonatal outcomes. These decreased levels of native thiol, total thiol, –SH/–SH þ –SS and increased levels of –SS/–SH and –SS/–SH þ – SS were associated with the presence of FGR. Decreased antioxidant and increased oxidant levels were found to be predictive for future neonatal complications in FGR.
We observed no difference in disulfide levels of patient and control groups contrary to our other studies [11]. According to our results, we suggest that the adverse neonatal outcomes may be decreased by the support of anti-oxidant agents at the early stages of FGR. We suggest the evaluation of dynamic Thiol/disulfide mechanism with the new, inexpensive, and rapid spectrophotometric method described by Erel et al. to predict adverse perinatal and neonatal outcome in FGR patients [6].
Acknowledgments
We would like to thank the patients and staff who participated in the study.
Disclosure Statement
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.
ORCID
Ozcan Erel http://orcid.org/0000-0002-2996-3236
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