Pomegranate Juice Supplementation Alters Utero-Placental Vascular Function and Fetal Growth in the eNOS-/- Mouse Model of Fetal Growth Restriction

The eNOS^−/− mouse provides a well-characterized model of fetal growth restriction (FGR) with altered uterine and umbilical artery function and reduced utero- and feto-placental blood flow. Pomegranate juice (PJ), which is rich in antioxidants and bioactive polyphenols, has been posited as a beneficial dietary supplement to promote cardiovascular health. We hypothesized that maternal supplementation with PJ will improve uterine and umbilical artery function and thereby enhance fetal growth in the eNOS^−/− mouse model of FGR. Wild type (WT, C57Bl/6J) and eNOS^−/− mice were supplemented from E12.5-18.5 with either PJ in their drinking water or water alone. At E18.5 uterine (UtA) and umbilical (UmbA) arteries were isolated for study of vascular function, fetuses and placentas were weighed and fetal biometric measurements taken. PJ supplementation significantly increased UtA basal tone (both genotypes) and enhanced phenylephrine-induced contraction in eNOS^−/− but not WT mice. Conversely PJ significantly reduced UtA relaxation in response to both acetylcholine (Ach) and sodium nitroprusside (SNP), endothelium dependent and independent vasodilators respectively from WT but not eNOS^−/− mice. UmbA sensitivity to U46619-mediated contraction was increased by PJ supplementation in WT mice; PJ enhanced contraction and relaxation of UmbA to Ach and SNP respectively in both genotypes. Contrary to our hypothesis, the changes in artery function induced by PJ were not associated with an increase in fetal weight. However, PJ supplementation reduced litter size and fetal abdominal and head circumference in both genotypes. Collectively the data do not support maternal PJ supplementation as a safe or effective treatment for FGR.

Exposure to omentum adipose tissue conditioned medium from obese pregnant women promotes myometrial artery dysfunction

Aim

Underlying mechanisms of poor pregnancy outcome in obese (OB) mothers (body mass index [BMI] ≥ 30 kg/m²) are unknown. Our studies demonstrate that OB pregnant women have altered myometrial artery (MA) function related to the thromboxane and nitric oxide pathways. In obesity, increased central fat mass is associated with an altered endocrine milieu. We tested the hypothesis that in OB pregnant women the omentum, a central fat store, releases factors that promote dysfunction in normal MAs.

Methods

Myometrial and omental adipose tissue biopsies were obtained from women with uncomplicated term pregnancies. Omental adipose tissue explants from six normal weight (NW; BMI 18.5–24.9 kg/m²) and six OB (BMI ≥ 30 kg/m²) women were cultured and the conditioned medium collected and pooled to produce NW medium and OB medium. Adipokine concentrations were measured using enzyme‐linked immunosorbent assays. Wire myography was used to assess the effect of conditioned medium (NW or OB; N = 7) or leptin (100 nM; N = 5) exposure on MA responses to U46619 (thromboxane‐mimetic) and bradykinin (endothelial‐dependent vasodilator).

Results

OB medium had higher leptin and lower adiponectin levels than NW medium. U46619 and bradykinin concentration response curves shifted upwards in MAs exposed to OB medium but were unaffected by leptin.

Conclusions

Omental adipose tissue from OB pregnant women produced altered concentrations of adipokines. Acute OB medium exposure induced MA dysfunction, an effect not mirrored by exposure to leptin. These data suggest that an aberrant endocrine environment created by increased central adiposity in OB pregnant women induces vascular endothelial dysregulation, which may predispose them to a poor pregnancy outcome.

The atrial natriuretic peptide (ANP) knockout mouse does not exhibit the phenotypic features of pre-eclampsia or demonstrate fetal growth restriction

The ANP knockout mouse is reported to exhibit pregnancy-associated hypertension, proteinuria and impaired placental trophoblast invasion and spiral artery remodeling, key features of pre-eclampsia (PE). We hypothesized that these mice may provide a relevant model of human PE with associated fetal growth restriction (FGR). Here, we investigated pregnancies of ANP wild type (ANP^+/+), heterozygous (ANP^+/-) and knockout (ANP^−/-) mice. Maternal blood pressure did not differ between genotypes (E12.5, E17.5), and fetal weight (E18.5) was unaffected. Placental weight was greater in ANP^−/− versus ANP^+/+ mice. Therefore, in our hands, the ANP model does not express phenotypic features of PE with FGR.

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Mouse models of pre-eclampsia and fetal growth restriction are needed to test potential therapies.

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ANP knockout mice have previously been identified as a potential model of pre-eclampsia.

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We find that these mice do not exhibit pregnancy-associated hypertension, or fetal growth restriction.

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ANP knockout mice do not provide a robust model of pre-eclampsia or fetal growth restriction.

Maternal obesity impairs specific regulatory pathways in human myometrial arteries

Obese women (body mass index ≥30 kg/m(2)) are at greater risk than normal weight women of pregnancy complications associated with maternal and infant morbidity, particularly the development of cardiovascular disease and metabolic disorders in later life; why this occurs is unknown. Nonpregnant, obese individuals exhibit systemic vascular endothelial dysfunction. We tested the hypothesis that obese pregnant women have altered myometrial arterial function compared to pregnant women of normal (18-24 kg/m(2)) and overweight (25-29 kg/m(2)) body mass index. Responses to vasoconstrictors, U46619 (thromboxane mimetic) and arginine vasopressin, and vasodilators, bradykinin and the nitric oxide donor sodium nitroprusside, were assessed by wire myography in myometrial arteries from normal weight (n = 18), overweight (n = 18), and obese (n = 20) women with uncomplicated pregnancies. Thromboxane-prostanoid receptor expression was assessed using immunostaining in myometrial arteries of normal weight and obese women. Vasoconstriction and vasodilatation were impaired in myometrial arteries from obese women with otherwise uncomplicated pregnancies. Disparate agonist responses suggest that vascular function in obese women is not globally dysregulated but may be specific to thromboxane and nitric oxide pathways. Because obesity rates are escalating, it is important to identify the mechanisms underlying impaired vascular function and establish why some obese women compensate for vascular dysfunction and some do not. Future studies are needed to determine whether central adiposity results in an altered endocrine milieu that may promote vascular dysfunction by altering the function of perivascular adipose tissue.

Chorionic plate arterial function is altered in maternal obesity

Objectives

To characterise Chorionic Plate Artery (CPA) function in maternal obesity, and investigate whether leptin exposure reproduces the obese CPA phenotype in normal-BMI women.

Study design

CPA responses to the thromboxane-A₂ mimetic U46619 (pre/post leptin incubation), to the nitric oxide donor sodium nitroprusside (SNP) and the occurrence of tone oscillations (pre/post leptin incubation) were assessed in 46 term placentas from women of normal (18.5–24.9) or obese (>30) Body Mass Index (BMI).

Outcome measures

Area Under the dose response Curve (AUC), maximum response (V_max), sensitivity (EC₅₀) to U46619 (pre/post leptin) and SNP; average vessel tone, oscillation amplitude and frequency (pre/post leptin).

Results

U46619 vasoconstriction was similar between BMI categories (p > 0.05), however vasodilatation to SNP was reduced in obesity (AUC p = 0.02, V_maxp = 0.04) compared to normal-BMI women. Leptin incubation altered responses to U46619 in both normal-BMI (EC₅₀ at 100 ng/ml leptin; p < 0.05) and obese women (AUC at 50 ng/ml; p < 0.05) but vasomotion was unaffected (p > 0.05).

Conclusions

Maternal obesity is associated with altered placental vascular function which may adversely affect placental oxygen and nutrient transport, placing the fetus at risk. Leptin incubation altered CPA vascular function but did not reproduce the obese phenotype.