Offspring sex determines the impact of the maternal ACE I/D polymorphism on maternal glycaemic control during the last weeks of pregnancy

Parental genetic effects on the offspring's phenotype without transmission of the gene itself-pathophysiology and clinical evidence

Parental genes can influence the phenotype of their offspring through genomic-epigenomic interactions even without the direct inheritance of specific parental genotypes. Maternal genetic variations can affect the ovarian and intrauterine environments and potentially alter lactation behaviors, impacting offspring nutrition and health outcomes independently of the fetal genome. Similarly, paternal genetic changes can affect the endocrine system and vascular functions in the testes, influencing sperm quality and seminal fluid composition. These changes can initiate early epigenetic modifications in sperm, including alterations in microRNAs, tRNA-derived small RNAs (tsRNAs), and DNA methylation patterns. These epigenetic modifications might induce further changes in target organs of the offspring, leading to modified gene expression and phenotypic outcomes without transmitting the original parental genetic alterations. This review presents clinical evidence supporting this hypothesis and discusses the potential underlying molecular mechanisms. Parental gene-offspring epigenome-offspring phenotype interactions have been observed in neurocognitive disorders and cardio-renal diseases.

Fibroblast growth factor 23 is associated with the development of gestational diabetes mellitus

BACKGROUND

Besides its established impact on bone and mineral metabolism, it was suggested that fibroblast growth factor 23 (FGF23) might play an important role in the pathogenesis of type 2 diabetes. The impact of FGF23 on gestational diabetes mellitus (GDM), however, is not well understood. iFGF23 ELISAs measure the intact FGF23 molecule, whereas cFGF23 assays measure intact FGF23 as well as degradation products of FGF23.

OBJECTIVES

The aim of this study is to compare the association of maternal and foetal cFGF23 and iFGF23 with GDM in a German birth cohort.

METHODS

cFGF23 and iFGF23 were analysed in 826 random mother/child pairs from the Berlin Birth Cohort.

RESULTS

Mothers who developed GDM had higher concentrations of iFGF-23 compared to mothers who did not suffer from GDM (19.73 vs. 13.23 pg/mL, p < 0.0001), but not higher concentrations of cFGF-23. Multivariant regression analyses showed that gestational diabetes is associated with iFGF23 independently of confounding factors such as age, BMI, ethnic background, family history of diabetes, smoking during pregnancy, and recurrent pregnancy loss. This, however, was only seen when using an iFGF23 ELISA measuring just the full length FGF23 and not in addition FGF23 fragments. No differences in both iFGF23 and cFGF23 concentrations between the GDM and non-GDM groups were detected in cord blood samples of the offspring.

CONCLUSIONS

This study of a representative German birth cohort showed that maternal but not foetal iFGF23 is independently associated with GDM.

Fetal sex and maternal insulin resistance during mid-pregnancy: a retrospective cohort study

Background

Recent studies have suggested that fetal sex influences maternal glucose and insulin metabolism during pregnancy. We examined whether fetal sex is associated with maternal insulin resistance and the β-cell function during mid-pregnancy.

Methods

This retrospective study included singleton pregnant women who underwent a 75-g oral glucose tolerance test (OGTT) at 24–34 weeks of gestation due to positive diabetic screening. In addition to plasma glucose (PG), we measured plasma insulin during the OGTT to obtain surrogate indices associated with insulin resistance (IR), including homeostasis assessment model (HOMA) -IR and insulin sensitivity index (IsOGTT), and β-cell function, including insulinogenic index (II), HOMA-β, and area under the curve of insulin response. We compared these indices between women carrying male fetuses to those carrying female fetuses.

Results

The study population included 617 women (mean age, 32.4 ± 4.9 years) with a mean pre-pregnancy body mass index (BMI) of 22.6±4.5. They underwent the 75g-OGTT at 29.0 ± 2.5 weeks. Two hundred fifty-eight (42%) women were diagnosed with gestational diabetes (GDM). There was no significant difference in maternal age, pre-pregnancy BMI, gestational age at OGTT, PG at OGTT, or the prevalence of GDM between women with a male fetus (n=338) (male group) and those with a female fetus (n=279) (female group). Regarding the indices of IR, IR was significantly higher and insulin sensitivity was lower in the female group than in the male group (HOMA-IR: 7.0 [5-9.6] vs. 6.2 [4.6-8.8], p< 0.05; IsOGTT: 5.86 [4.29-7.83] vs. 6.29 [4.59-8.84], p< 0.01) (median [quartile range]). These differences remained significant after adjustment for maternal age, pre-pregnancy BMI, gestational age and fasting PG at OGTT, and the diagnosis of GDM. In contrast, the β-cell function did not differ between the two groups.

Conclusion

Maternal IR during mid-pregnancy was significantly higher in women carrying a female fetus than in those with a male fetus. The sex of the fetus may affect maternal insulin sensitivity during mid-pregnancy.

Epigenetic signatures of gestational diabetes mellitus on cord blood methylation

Background

Intrauterine exposure to gestational diabetes mellitus (GDM) confers a lifelong increased risk for metabolic and other complex disorders to the offspring. GDM-induced epigenetic modifications modulating gene regulation and persisting into later life are generally assumed to mediate these elevated disease susceptibilities. To identify candidate genes for fetal programming, we compared genome-wide methylation patterns of fetal cord bloods (FCBs) from GDM and control pregnancies.

Methods and results

Using Illumina’s 450K methylation arrays and following correction for multiple testing, 65 CpG sites (52 associated with genes) displayed significant methylation differences between GDM and control samples. Four candidate genes, ATP5A1, MFAP4, PRKCH, and SLC17A4, from our methylation screen and one, HIF3A, from the literature were validated by bisulfite pyrosequencing. The effects remained significant after adjustment for the confounding factors maternal BMI, gestational week, and fetal sex in a multivariate regression model. In general, GDM effects on FCB methylation were more pronounced in women with insulin-dependent GDM who had a more severe metabolic phenotype than women with dietetically treated GDM.

Conclusions

Our study supports an association between maternal GDM and the epigenetic status of the exposed offspring. Consistent with a multifactorial disease model, the observed FCB methylation changes are of small effect size but affect multiple genes/loci. The identified genes are primary candidates for transmitting GDM effects to the next generation. They also may provide useful biomarkers for the diagnosis, prognosis, and treatment of adverse prenatal exposures.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0329-3) contains supplementary material, which is available to authorized users.

Associations Between Fetal Imprinted Genes and Maternal Blood Pressure in Pregnancy

In addition to maternal genes and environmental exposures, variation in fetal imprinted genes could also affect maternal blood pressure during pregnancy. Our objective was to test the associations between polymorphic variants in 16 imprinted genes and maternal mean arterial blood pressures in 1160 DNA trios from 2 established birth cohorts (the Cambridge Baby Growth and Wellbeing Studies) and seek replication in 1367 Hyperglycemia and Adverse Pregnancy Outcome Study participants. Significant univariate associations, all independent of fetal sex, were observed in the Cambridge cohorts, including FAM99A rs1489945 transmitted from the mother (P=2×10^-4), DLK1 rs10139403 (mother; P=9×10^-4), DLK1 rs12147008 (mother; P=1×10^-3), H19 rs217222 (father; P=1×10^-3), SNRPN rs1453556 (father; P=1×10^-3), IGF2 rs6356 (father; P=1×10^-3), and NNAT rs6066671 (father; P=1×10^-3). In meta-analysis including additional independent Hyperglycemia and Adverse Pregnancy Outcome Study data, the association with maternally transmitted fetal DLK1 rs10139403 reached genome-wide significance (P=6.3×10^-10). With the exception of fetal rs1489945 and rs217222, all of other associations were unidirectional and most were statistically significant. To further explore the significance of these relationships, we developed an allele score based on the univariate findings. The score was strongly associated with maternal blood pressure at 31 weeks (P=4.1×10^-8; adjusted r²=5.6%) and 37 weeks of pregnancy (P=1.1×10^-4; r²=3.6%), and during the last 2 weeks before parturition (P=1.1×10^-10; r²=8.7%). It was also associated with gestational hypertension (odds ratio, 1.54 [range, 1.14-2.09] per allele; P=0.005; 45 cases and 549 controls). These data support the concept that fetal imprinted genes are related to the development of gestational hypertension.

Fetal sex and maternal risk of gestational diabetes mellitus: the impact of having a boy

OBJECTIVE

Retrospective analyses of perinatal databases have raised the intriguing possibility of an increased risk of gestational diabetes mellitus (GDM) in women carrying a male fetus, but it has been unclear if this was a spurious association. We thus sought to evaluate the relationship between fetal sex and maternal glucose metabolism in a well-characterized cohort of women reflecting the full spectrum of gestational glucose tolerance from normal to mildly abnormal to GDM.

RESEARCH DESIGN AND METHODS

A total of 1,074 pregnant women underwent metabolic characterization, including oral glucose tolerance test (OGTT), at mean 29.5 weeks' gestation. The prevalence of GDM, its pathophysiologic determinants (β-cell function and insulin sensitivity/resistance), and its clinical risk factors were compared between women carrying a female fetus (n = 534) and those carrying a male fetus (n = 540).

RESULTS

Women carrying a male fetus had lower mean adjusted β-cell function (insulinogenic index divided by HOMA of insulin resistance: 9.4 vs. 10.5, P = 0.007) and higher mean adjusted blood glucose at 30 min (P = 0.025), 1 h (P = 0.004), and 2 h (P = 0.02) during the OGTT, as compared with those carrying a female fetus. Furthermore, women carrying a male fetus had higher odds of developing GDM (odds ratio 1.39 [95% CI 1.01-1.90]). Indeed, male fetus further increased the relative risk of GDM conferred by the classic risk factors of maternal age >35 years and nonwhite ethnicity by 47 and 51%, respectively.

CONCLUSIONS

Male fetus is associated with poorer β-cell function, higher postprandial glycemia, and an increased risk of GDM in the mother. Thus, fetal sex potentially may influence maternal glucose metabolism in pregnancy.

Female fetus is associated with greater maternal insulin resistance in pregnancy

AIM

To explore the hypothesis that female fetus is associated with greater maternal insulin resistance during pregnancy.

METHODS

In a singleton pregnancy cohort study (n = 299), we compared maternal insulin resistance according to fetal sex, based on plasma biomarkers from a 50-g 1-h oral glucose tolerance test at 24-28 weeks gestation. The primary outcome was plasma glucose-to-insulin ratio. Other outcomes included plasma proinsulin-to-insulin ratio, and insulin, proinsulin, leptin, adiponectin and insulin-like growth factor I and II concentrations.

RESULTS

After adjusting for maternal race, age, parity, education, pre-pregnancy BMI, smoking and alcohol use, history of gestational diabetes, and gestational age at blood sampling, plasma insulin concentrations were significantly higher (mean ± sd: 66.4 ± 50.5 vs. 51.0 ± 46.1 mU/l; adjusted P = 0.001), and glucose-to-insulin ratios significantly lower (2.60 ± 2.03 vs. 3.77 ± 4.98 mg/dl/mU/l; adjusted P = 0.002) in women bearing a female vs those bearing a male fetus, despite similar glucose levels (116.4 ± 27.2 vs. 117.0 ± 31.9 mg/dl; adjusted P = 0.92).There were no significant differences in proinsulin-to-insulin ratios, or leptin, adiponectin, insulin-like growth factor I and insulin-like growth factor II concentrations by fetal sex.

CONCLUSION

Female fetus may be associated with greater maternal insulin resistance during pregnancy.

A functional fetal HSD11B2[CA]n microsatellite polymorphism is associated with maternal serum cortisol concentrations in pregnant women

BACKGROUND/AIMS

Cortisol plays an important role during pregnancy. It controls maternal glucose metabolism and fetal development. Cortisol metabolism is partially controlled by the 11b-HSD2. This enzyme is expressed in the kidney and human placenta. The activity of the enzyme is partially controlled by functional polymorphisms: the HSD11B2[CA]n microsatellite polymorphism. The impact of this functional gene polymorphism on cortisol metabolism and potential effects on the newborn's is unknown so far.

METHODS

In the current prospective birth cohort study in southern Asia, we analyzed the association of the HSD11B2[CA]n microsatellite polymorphisms in 187 mothers and their newborn's on maternal and newborn's serum cortisol concentrations.

RESULTS

Using multivariable regression analyses considering known confounding (gestational age, newborn's gender, the labor uterine contraction states and the timing during the day of blood taking), we showed that the fetal HSD11B2[CA]n microsatellite polymorphisms in the first intron was related to maternal cortisol concentration (R2=0.26, B=96.27, p=0.007), whereas as the newborn's cortisol concentrations were independent of fetal and maternal HSD11B2[CA]n microsatellite polymorphism.

CONCLUSIONS

Our study showed for the first time that the fetal HSD11B2[CA]n microsatellite polymorphism of the HSD11B2 gene in healthy uncomplicated human pregnancy is associated with maternal cortisol concentration. This indicates that fetal genes controlling cortisol metabolism may affect maternal cortisol concentration and hence physiology in healthy pregnant women.

Angiotensin-converting enzyme gene insertion/deletion polymorphism with metabolic syndrome in Turkish patients

BACKGROUND

The ACE gene has received substantial attention in recent years as candidate for a variety of diseases. The most common polymorphism in ACE gene is the Insertion/Deletion (I/D, rs4646994) polymorphism located on intron 16.

AIM

We investigated the association between metabolic syndrome (MS) and the insertion (I) - deletion (D) polymorphisms in the angiotensin converting enzyme (ACE) gene in south-east of Turkey.

SUBJECTS AND METHODS

One hundred and sixty subjects, with 101 cases of MS and 59 age- and gender-matched healthy controls were included in the study.

RESULTS

The frequency of ACE I/D polymorphism was found to be 49.5% for DD, 36.6% for ID, and 13.9% for II in the MSstudy group and 44.1% for DD, 42.4% for ID and 13.5% for II in the control group. Allele frequencies were found to be 0.68% for D and 0.32% for I allele in the study group with MS and 0.65% for D, 0.35% for I allele in the control group. The I/D polymorphism of the ACE gene, DD, ID, and II genotypes occurred with similar frequencies in the study group with MS and the control group with no significant differences (p<0.05). On applying one-way analysis of variance to different ACE gene polymorphic groups in patients with MS were not significantly associated to ACE gene polymorphism and waist circumference, systolic blood pressure, diastolic blood pressure, fasting blood glucose, HDL, and LDL (p<0.05).

CONCLUSIONS

Further studies of patients in larger numbers and of different ethnic backgrounds may be necessary to elucidate the association between the ACE I/D gene polymorphism and MS.