Oxidative stress-related gene interactions with preterm delivery in Korean women

Spontaneous preterm birth: advances toward the discovery of genetic predisposition

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.

New Insights Regarding Genetic Aspects of Childhood Obesity: A Minireview

Introduction: Childhood obesity is occurring at alarming rates in both developed and developing countries. "Obesogenic" environmental factors must be associated with variants of different risk alleles to determine polygenic or common obesity, and their impact depends on different developmental stages.The interaction between obesogenic environment and genetic susceptibility results in the so-called polygenic forms of obesity. In contrast, monogenic and syndromic obesity are not influenced by environmental events. Therefore, this review aimed to underline the roles of some of the most studied genes in the development of monogenic and polygenic obesity in children. Results: Among the most common obesity related genes, we chose the fat mass and obesity-associated (FTO) gene, leptin gene and its receptor, tumor necrosis factor alpha (TNF-α), the melanocortin 4 receptor gene (MC4R), Ectoenzyme nucleotide pyrophosphate phosphodiesterase 1 (ENPP1), and others, such as peroxisome proliferator-activated receptor gamma (PPARG), angiotensin-converting enzyme (ACE), glutathione S-transferase (GST), and interleukin-6 (IL-6) genes. The roles of these genes are complex and interdependent, being linked to different cornerstones in obesity development, such as appetite behavior, control of food intake and energy balance, insulin signaling, lipid and glucose metabolism, metabolic disorders, adipocyte differentiation, and so on. Conclusions: Genetic predisposition is mandatory, but not enough to trigger obesity.Dietary interventions and proper lifestyle changes can prevent obesity development in genetically predisposed children. Further studies are needed to identify the precise role of both genetic and obesogenic factors in the development of childhood obesity in order to design effective preventive methods.

Spontaneous preterm birth and single nucleotide gene polymorphisms: a recent update

Background

Preterm birth (PTB), birth at <37 weeks of gestation, is a significant global public health problem. World-wide, about 15 million babies are born preterm each year resulting in more than a million deaths of children. Preterm neonates are more prone to problems and need intensive care hospitalization. Health issues may persist through early adulthood and even be carried on to the next generation. Majority (70 %) of PTBs are spontaneous with about a half without any apparent cause and the other half associated with a number of risk factors. Genetic factors are one of the significant risks for PTB. The focus of this review is on single nucleotide gene polymorphisms (SNPs) that are reported to be associated with PTB.

Results

A comprehensive evaluation of studies on SNPs known to confer potential risk of PTB was done by performing a targeted PubMed search for the years 2007–2015 and systematically reviewing all relevant studies. Evaluation of 92 studies identified 119 candidate genes with SNPs that had potential association with PTB. The genes were associated with functions of a wide spectrum of tissue and cell types such as endocrine, tissue remodeling, vascular, metabolic, and immune and inflammatory systems.

Conclusions

A number of potential functional candidate gene variants have been reported that predispose women for PTB. Understanding the complex genomic landscape of PTB needs high-throughput genome sequencing methods such as whole-exome sequencing and whole-genome sequencing approaches that will significantly enhance the understanding of PTB. Identification of high risk women, avoidance of possible risk factors, and provision of personalized health care are important to manage PTB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3089-0) contains supplementary material, which is available to authorized users.

Maternal Stress and Depressive Symptoms and Infant Development at Six Months: the Mothers and Children's Environmental Health (MOCEH) Prospective Study

Our objective is to evaluate the relationships between prenatal maternal stress and depressive symptoms, respectively, and infant neurodevelopment at 6 months, adjusted for heavy metals and oxidative stress. This research is a part of a multi-center birth cohort study in South Korea. Information on stress and depressive symptoms was collected during the first trimester using Psychosocial Well-Being Index Short Form (PWI-SF) and Center for Epidemiological Studies Depression Scale (CES-D). The Korean Bayley Scales of Infant Development-II assessment (BSID-II), which includes the standardized mental development index (MDI) and psychomotor developmental index (PDI), and Korean Ages & Stages Questionnaires (K-ASQ) were applied to infants at six months of age. A higher index score indicates better development. Among 641 babies, 320 were female (50%). Maternal PWI ≥ 29 (vs. PWI ≤ 18) during early pregnancy was associated with a decrease in MDI scores of 5.37 points (P = 0.02) after adjusting for socioeconomic factors. Maternal CES-D ≥ 26 (vs. CES-D ≤ 10) during early pregnancy was associated with a decrease in MDI scores of 8.18 points (P = 0.01). The associations remained significant even after adjustment for lead, cadmium, and MDA levels (P < 0.05). However, no association was found between maternal PWI/CES-D and PDI score. No interaction was observed between stress and lead exposure. We found an inverse association between prenatal maternal stress and depressive symptoms, and MDI scores in 6-month-old infants after adjustment for prenatal lead exposure, which is known to affect cognitive function negatively.

Genetic polymorphisms in Cytochrome P 4501B1 and susceptibility to idiopathic preterm labor in North Indian population

OBJECTIVE

The etiology of preterm labor (PTL) is still unknown, but it may be related to a possible genetic predisposition together with involvement of environmental factors. We investigated the relation between PTL and polymorphisms in Cytochrome P4501B1 (CYP1B1) gene, which is involved in the metabolism of a wide range of environmental toxins and hormones.

DESIGN AND METHODS

Three hundred (n=300) cases of PTL and equal number of subjects of full term labor (FTL), after excluding all the known risk factors for PTL were included in the study. A two step allele specific PCR was performed for polymorphic analysis of CYP1B1 gene.

RESULTS

The homozygous variant genotype of CYP1B1*2 (OR=2.97, 95%CI=1.08-8.08, p=0.033) and heterozygous variant of CYP1B1*3 (OR=2.57, 95%CI=1.88-3.63, p=0.001), and CYP1B1*7 (OR=2.59, 95%CI=1.85-3.62, p=0.001) were found to be significantly higher in PTL cases as compared to FTL.

CONCLUSIONS

The present study demonstrates the possible association of homozygous variant of CYP1B1*2 and heterozygous variant of CYP1B1*3 and CYP1B1*7 genes with the increased risk of PTL.

Birth weight of Korean infants is affected by the interaction of maternal iron intake and GSTM1 polymorphism

Excessive iron consumption during pregnancy can lead to increased oxidative stress in the maternal body, which may result in adverse pregnancy outcomes. Glutathione S-transferases (GSTs) originate from a superfamily of detoxifying enzymes that play a role in reducing xenobiotic compounds and oxidative stress. The aim of this study was to determine the relationship among GST gene expression, maternal iron intake during pregnancy, and neonatal birth weight. The study participants were 1087 Korean gravidas and their newborns recruited for the Mothers and Children's Environmental Health study between 2006 and 2010. A 24-h dietary recall interview was conducted to estimate iron intake; additional intake through nutritional supplements was thoroughly investigated. Deletion polymorphisms of GSTM1 and GSTT1 were genotyped using PCR. Dietary iron consumption during pregnancy was positively associated with birth weight in pregnant women who were GSTM1-present after adjustment for the following covariates: maternal age, prepregnancy BMI, mother's education level, log-transformed urinary cotinine level, infant gender, gestational age at term, log-transformed energy intake, parity, and the use of folic acid supplements (P < 0.05). There were interactions between the GSTM1 genotype and iron intakes from animal foods (P < 0.05), diet (P < 0.05), and diet with supplements (P < 0.05). No relationship was found between maternal iron intake and birth weight for the GSTT1 polymorphism. This study demonstrates that increased iron consumption during pregnancy may improve infant birth weight for mothers who are GSTM1-present, but it might not be beneficial for mothers with the GSTM1-null genotype.

Associations between genetic polymorphisms of beta-2 adrenergic receptor and preterm delivery in Korean women

PROBLEM

We investigated genetic polymorphisms to understand the etiology of preterm delivery, which involves inflammatory cytokines and uterine contraction. Maternal polymorphisms of ADRB2, iNOS, and eNOS were examined, and associations between these and the risk of preterm delivery were sought.

METHOD OF STUDY

This study was performed on 166 Korean women who underwent preterm delivery and 289 normal controls. Logistic regression analyses were carried out to identify single genes and haplotypes that affect the risk of preterm delivery.

RESULTS

The G/G haplotype of ADRB2-rs1042713 and -rs1042714 was found to be associated with the risk of preterm delivery (OR = 1.90, 95% CI = 1.08-3.33, P-value = 0.0252). The genotype frequency of G allele in ADRB2-rs1042714 was associated with increased the risk of preterm delivery. However, after the adjustment of multiple comparison corrections, the association with preterm delivery was not remained significantly.

CONCLUSION

These findings possibly aid our understanding of the pathogenesis of preterm delivery and suggest that a haplotype with variants in maternal genes involved in adrenergic activation may lead to the dysregulation of uterine contractility and increase the risk of preterm delivery.

A model for prediction of spontaneous preterm birth in asymptomatic women

BACKGROUND

Preterm birth is a complex health problem with social, environmental, behavioral, and genetic determinants of an individual's risk and remains a major challenge in obstetrics. Recent research has caused improvements in predicting preterm birth; however, there is still controversy about the prediction of preterm birth in asymptomatic women. The purpose of this study was to determine if Bayesian filtering can be used in a clinical setting to predict spontaneous preterm birth in asymptomatic women.

METHODS

A model of predicting spontaneous preterm birth using PopBayes based on a Bayesian filtering algorithm was developed using a previously collected dataset, then applied to a prospectively collected cohort of asymptomatic women who delivered singleton live newborns at or after 24 weeks of gestation. Cases complicated with major congenital malformations were excluded.

RESULTS

The proportion of patients with spontaneous preterm birth was 18.4% (96 of 522) at <37 weeks gestation, 5.4% (28 of 522) at <34 weeks gestation, and 2.7% (14 of 522) at <32 weeks gestation. The match rates with the combination of demographic, clinical, and genetic factors using a Bayesian filtering method (PopBayes) were higher than the match rates using demographic and clinical factors only, including maternal age, maternal body mass index (BMI), prior preterm birth, education, occupation, income, and active and passive smoking. The match rates in preterm delivery before 32 weeks of gestation were higher than the match rates in preterm delivery before 37 and 34 weeks of gestation (94.3% vs. 84.7% and 82.0%, respectively). The negative predictive values for demographic, clinical, and genetic factors in predicting preterm delivery using PopBayes were consistently >90%.

CONCLUSIONS

We suggest that Bayesian filtering (PopBayes) is a customizable and useful tool in establishing a model for the prediction of preterm birth.

Paraoxonase 1 gene and glutathione S-transferase μ 1 gene interaction with preterm delivery in Korean women

OBJECTIVE

This study was undertaken to identify the paraoxonase 1 gene and glutathione S-transferase μ 1 gene interaction for the risk of preterm delivery and to determine the serum paraoxonase activity according to paraoxonase 1 genotypes.

STUDY DESIGN

This case-control study was performed on 162 gravida women with preterm delivery and 306 controls. Serum paraoxonase activity was measured by a ultraviolet spectrophotometer. Logistic regression, 2-way analysis of variance, and multifactor dimensionality reduction analysis were used.

RESULTS

Gravida women with the QQ and QR genotype of paraoxonase 1 with high body mass index had 6.19- and 4.41-fold increased risks of preterm delivery. The glutathione S-transferase μ 1 null genotype and the interaction between the paraoxonase 1 genotype and glutathione S-transferase μ 1 null type conferred a risk for preterm delivery. Serum paraoxonase activity was significantly different according to paraoxonase 1 genotypes (P < .0001).

CONCLUSION

The glutathione S-transferase μ 1 null genotype confers a risk for preterm delivery in Korean gravida women independent of and interactive with the paraoxonase 1 genotype.

Identification of fetal and maternal single nucleotide polymorphisms in candidate genes that predispose to spontaneous preterm labor with intact membranes

OBJECTIVE

The purpose of this study was to determine whether maternal/fetal single nucleotide polymorphisms (SNPs) in candidate genes are associated with spontaneous preterm labor/delivery.

STUDY DESIGN

A genetic association study was conducted in 223 mothers and 179 fetuses (preterm labor with intact membranes who delivered <37 weeks of gestation [preterm birth (PTB)]), and 599 mothers and 628 fetuses (normal pregnancy); 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; the false discovery rate was used to correct for multiple testing.

RESULTS

The strongest single locus associations with PTB were interleukin-6 receptor 1 (fetus; P=.000148) and tissue inhibitor of metalloproteinase 2 (mother; P=.000197), which remained significant after correction for multiple comparisons. Global haplotype analysis indicated an association between a fetal DNA variant in insulin-like growth factor F2 and maternal alpha 3 type IV collagen isoform 1 (global, P=.004 and .007, respectively).

CONCLUSION

An SNP involved in controlling fetal inflammation (interleukin-6 receptor 1) and DNA variants in maternal genes encoding for proteins involved in extracellular matrix metabolism approximately doubled the risk of PTB.

Human milk enhances antioxidant defenses against hydroxyl radical aggression in preterm infants

BACKGROUND

Preterm infants endowed with an immature antioxidant defense system are prone to oxidative stress. Hydroxyl radicals are very aggressive reactive oxygen species that lack specific antioxidants. These radicals cannot be measured directly, but oxidation byproducts of DNA or phenylalanine in urine are reliable markers of their activity. Human milk has a higher antioxidant capacity than formula.

OBJECTIVE

We hypothesized that oxidative stress associated with prematurity could be diminished by feeding human milk.

DESIGN

We recruited a cohort of stable preterm infants who lacked perinatal conditions associated with oxidative stress; were not receiving prooxidant or antioxidant drugs, vitamins, or minerals before recruitment; and were fed exclusively human milk (HM group) or preterm formula (PTF group). Collected urine was analyzed for oxidative bases of DNA [8-hydroxy-2'-deoxyguanosine (8-oxodG)/2'-deoxyguanosine (2dG) ratio] and oxidative derivatives of phenylalanine [ortho-tyrosine (o-Tyr)/Phe ratio] by HPLC coupled to tandem mass spectrometry. Healthy term newborn infants served as control subjects.

RESULTS

Both preterm groups eliminated greater amounts of metabolites than did the control group. However, the PTF group eliminated significantly (P < 0.02) higher amounts of 8-oxodG (8-oxodG/2dG ratio: 10.46 +/- 3.26) than did the HM group (8-oxodG/2dG ratio: 9.05 +/- 2.19) and significantly (P < 0.01) higher amounts of o-Tyr (o-Tyr/Phe ratio: 14.90 +/- 3.75) than did the HM group (o-Tyr/Phe ratio: 12.53 +/- 3.49). When data were lumped together independently of the type of feeding received, a significant correlation was established between the 8-oxodG/2dG and o-Tyr/Phe ratios in urine, dependent on gestational age and birth weight.

CONCLUSION

Prematurity is associated with protracted oxidative stress, and human milk is partially protective.