N.M. Gude

Effects of gestational diabetes on human placental glucose uptake, transfer, and utilisation.

Aims/hypothesis. Gestational diabetes is associated with complications for the offspring before, during and after delivery. Poor maternal glucose control, however, is a weak predictor of these complications. Given its position at the interface of the maternal and fetal circulations, the placenta possibly plays a crucial part in protecting the fetus from adverse effects from the maternal diabetic milieu. We hypothesised that gestational diabetes may result in changes in placental function, particularly with respect to the uptake, transfer, and/or utilisation of glucose. We aimed to examine glucose transport and utilisation in intact human placental lobules from women with gestational diabetes and those from normal pregnancies. Method. Dual perfusion of an isolated placental lobule was done on placentae from diet treated gestational diabetic (n = 7) and normal pregnant patients (n = 9) using maternal glucose concentrations of 4, 8, 16 and 24 mmol/l in random order over a 4-h experiment. Results were expressed in μmol · min–1· g–1. Results. d-glucose uptake from the maternal circulation (control 0.492 vs gestational diabetes mellitus 0.248, at 8 mmol/l maternal glucose), d-glucose utilisation by the placenta (0.255 vs 0.129), d-glucose transfer to the fetal circulation (direct 0.979 vs 0.402; net transfer 0.269 vs 0.118) and l-lactate maternal release into both the fetal (0.052 vs 0.042) and maternal (0.255 vs 0.129) circulation were significantly reduced during in vitro perfusion of placentae from patients with gestational diabetic pregnancies. Transfer of 3H-l-glucose also significantly reduced in the diabetic group (8.1 % vs 2.6 %). Conclusion/interpretation. These results suggest that placental transport and metabolism of d-glucose is altered during gestational diabetes. [Diabetologia (2000) 43: 576–582]

Placental glucose transport and utilisation is altered at term in insulin-treated, gestational-diabetic patients

Abstract.Aims/hypothesis: We have previously shown that placentae from patients with gestational diabetes mellitus who did not receive insulin had lower glucose transport and utilisation than non-diabetic control subjects. To assess the placental glucose handling characteristics of women with gestational diabetes mellitus receiving insulin, we examined glucose transport and utilisation in placentae from three groups of women after term delivery: those with gestational diabetes mellitus and receiving insulin (n = 9, insulin group); those with gestational diabetes mellitus and not receiving insulin (n = 10, no insulin group); and those with normal, non-diabetic pregnancies (n = 9, control group). Methods: Dual perfusion of an isolated placental lobule was done using maternal glucose concentrations of 4, 8, 16 and 24 mmol/l. Glucose and l-lactate concentrations in the maternal and fetal effluents were measured. Direct glucose transfer from the maternal to the fetal effluent was measured using 14C-d-glucose. Mean rates in μmol ming–1 (wet tissue) at maternal glucose concentration of 8 mmol/l are shown. Results: Glucose uptake from the maternal perfusate (insulin group 0.57, no insulin group 0.30) and net glucose transfer to the fetal effluent (insulin group 0.41, no insulin group 0.20) both increased in the placentae of women receiving insulin compared with the diabetic group not receiving insulin. Both groups of patients had lower placental glucose utilisation than the control group (insulin group 0.16, no insulin group 0.10, control group 0.25). Conclusion/interpretation: These results suggest that materno-fetal glucose transport increases in the placentae of women with gestational diabetes mellitus who receive insulin compared with those women who do not receive insulin. [Diabetologia (2001) 44: 1133–1139]

NITRIC OXIDE METABOLITES IN NORMAL HUMAN PREGNANCY AND PREECLAMPSIA

Objective: Alterations in the vascular endothelial release of nitric oxide (NO) may contribute to the vasodilatory adaptation to normal pregnancy and to the vasoconstriction associated with preeclampsia. The aim of this study was to investigate these hypotheses by measuring plasma levels of the stable metabolites of NO, nitrite and nitrate, during normal human pregnancy and those complicated by preeclampsia.Methods: Plasma samples were obtained from women in the following groups: nonpregnant; normal first-, second-, and third-trimester pregnant; and preeclamptic. Nitrite concentrations in the samples were determined using a colorimetric assay. Nitrate concentrations were determined using anion-exchange chromatography with UV detection.Results: The plasma nitrite and nitrate concentrations of normal pregnant women (9.45 ± 0.58 u.M. n = 59. and 85 ± 8 µM, n = 29, respectively) were not significantly different from those of nonpregnant women (10.04 ± 1.47 µM, n = 10, and 95 ± 15 µM, n = 9, respectively), and...

Differential Bidirectional Transfer of Indinavir in the Isolated Perfused Human Placenta

ABSTRACT The protease inhibitor (PI) indinavir may be used in the management of human immunodeficiency virus (HIV) infection during pregnancy. Poor maternal-to-fetal transfer of indinavir has been reported previously, but the mechanisms of transfer remain unknown. The bidirectional transfer of indinavir was assessed in dually perfused, isolated human placentae. Term placentae (n = 5) were obtained from non-HIV-infected pregnant women. To investigate transport mechanisms, the steady-state transfer of indinavir was compared to those of antipyrine (a marker of passive diffusion) and [3H]vinblastine (a marker of P-glycoprotein [P-gp] transport) in the maternal-to-fetal and fetal-to-maternal directions in each placenta. Indinavir and antipyrine perfusate concentrations were determined by using reverse-phase, high-performance liquid chromatography; [3H]vinblastine concentrations were measured by liquid scintillation. The antipyrine transfer clearance in each direction did not differ (P = 0.76), a finding consistent with passive diffusion. However, the maternal-to-fetal transfer clearance of vinblastine, normalized to that of antipyrine (clearance index) (0.31 ± 0.05), was significantly lower than the fetal-to-maternal clearance index of vinblastine (0.67 ± 0.17; P = 0.017), suggesting the involvement of placental P-gp. Similarly, the maternal-to-fetal clearance index of indinavir (0.39 ± 0.09) was significantly lower than its fetal-to-maternal clearance index (0.97 ± 0.12; P < 0.001). These results represent the first evidence for differential transfer of a xenobiotic in the intact human placenta. The use of transport modulators to increase the maternal-to-fetal transfer of PIs as a possible strategy to reduce mother-to-child transmission of HIV warrants investigation.

Placental Nitric Oxide Synthase Activity and Abnormal Umbilical Artery Flow Velocity Waveforms

Objective To assess the nitric oxide synthase activity in placentas from women with either normal or abnormal Doppler ultrasound umbilical artery flow velocity waveforms who delivered by elective cesarean. Methods This prospective observational study involved 16 women admitted either for elective cesarean for standard obstetric indications (with normal umbilical artery Doppler waveform studies, n = 8) or with evidence of fetal or maternal complications of pregnancy (with abnormal umbilical artery Doppler studies, n = 8). Placental tissue was collected and frozen in liquid nitrogen immediately upon delivery. Following storage at −80C, nitric oxide synthase activity was analyzed by measuring the conversion of [3H]L-arginine to [3H]L-citrulline. Results Placentas from women with abnormal umbilical artery flow velocity waveforms showed significantly lower mean nitric oxide synthase activity than did placentas from women with normal umbilical artery flow velocity waveforms (Vmax = 11.3 pmol/minute/mg protein versus 22.6 pmol/minute/mg protein). Conclusion There is a statistically significant reduction in nitric oxide synthase activity in placentas from pregnancies with abnormal umbilical artery flow velocity waveforms.

Decidua Parietalis-Derived Mesenchymal Stromal Cells Reside in a Vascular Niche Within the Choriodecidua

Mesenchymal stromal cells (MSCs) from gestational tissues represent promising cell populations with stem cell-like properties for use in regenerative medicine. Previously, we reported that MSCs in the chorionic villi of the human placenta reside in a vascular niche. However, the niche(s) in which MSCs reside in the fetal membranes, another rich source of MSCs, remains to be determined. The cell surface markers STRO-1 and 3G5 were previously employed to identify niches in a variety of tissues and here we use these markers to report the location of the MSC niche in the human decidua parietalis. The cultured decidua parietalis MSCs (DPMSCs) isolated from the choriodecidua component of the fetal membranes possessed stem cell-like properties such as adherence to plastic, colony forming ability, and multipotent differentiation potential. Fluorescence in situ hybridization analysis showed cultured DPMSCs were of maternal origin. Immunocytochemistry demonstrated that cultured DPMSCs stained positively with stem cell surface markers 3G5, CD105, CD106, STRO-1, CD146, CD49a, and α-SMA but were negative for hematopoietic markers (CD117, CD34) and vascular markers (CD34, von Willebrand factor [vWF]). Immunohistochemistry with antibodies to stem cell surface markers and the endothelial markers on term fetal membranes revealed a vascular niche for DPMSCs, which was confirmed by immunofluorescence analysis. Both STRO-1 and vWF fluorescence signals showed substantial overlap, while CD146 and vWF signals showed partial overlap. These observations were consistent with a vascular niche.

Antioxidant Gene Expression in Preeclamptic Placentae: A Preliminary Investigation

Oxidative stress has been implicated in the pathogenesis of preeclampsia. This study measured the relative mRNA expression of antioxidant proteins glutathione peroxidase 1 and 4, glutathione reductase, thioredoxin 1 and 2, thioredoxin reductase 1, thioredoxin peroxidase 3 and superoxide dismutase 1 and 2 in preeclamptic and non-preeclamptic placentae. Quantitative real-time PCR was conducted on placental mRNA isolated from preeclamptic and control patients. Cycle threshold numbers and fold differences were calculated as a measure of linear product amplification and used for comparison. The mRNA expression of glutathione reductase was significantly reduced (fold difference 0.41, p<0.05) in preeclamptic placenta when compared to controls while the expression of thioredoxin peroxidase 3 was significantly increased (fold difference 3.25, p<0.001) in the preeclamptic placentae. No significant difference in expression was observed for glutathione peroxidase 1 and 4, thioredoxin 1 and 2, thioredoxin reductase 1 and superoxide dismutase 1 and 2. These results suggest that it is the abnormal oxidative insult associated with preeclampsia not mRNA expression of antioxidant proteins that may be responsible for reduced antioxidant enzyme activity in preeclamptic placentae.

Changes in the biological activity of autocoids during passage through the human perfused fetoplacental lobule

Changes in the biological activities of a number of autacoids after a single passage through the human perfused fetoplacental lobule have been assessed by bioassay, whilst recording fetal vascular resistance. Bradykinin did not affect vascular resistance, but its biological activity on the superfused bioassay tissues fell by approximately 98%, whereas des-Asp1-angiotensin I activity increased at least 80-fold and the vascular resistance rose. All these effects were inhibited by captopril. Angiotensin II increased vascular resistance but its activity on the bioassay tissues was not changed. 5-Hydroxytryptamine activity was reduced by 67-90% and resistance to flow was not affected. The activities of prostaglandins D2, E2, and F2 alpha were slightly reduced. Prostaglandins D2 and F2 alpha caused vasoconstriction, their maximum effects being greater than those of either of the angiotensins. The TxA2-mimetic U46619 was approximately 90 times more potent than PGF2 alpha, as a vasoconstrictor, but the maximal effects were comparable. Thus, autacoid activity can be reduced, augmented or not affected during passage through the human perfused fetal placental vasculature.

Effects of eicosanoid and endothelial cell derived relaxing factor inhibition on fetal vascular tone and responsiveness in the human perfused placenta

Summary Local output of endothelial cell-derived relaxing factor (EDRF) appeared tomake a greater contribution to the low resistance of the fetal circulation of the human placenta perfused in vitro than did prostaglandins, such as prostacyclin. Whereas blockade of the effects of EDRF, using three drugs inhibiting EDRF by differing mechanisms, caused increased fetal vascular resistance, reduction of prostaglandin output using three drugs inhibiting various stages of prostaglandin biosynthesis did not. Concomitant EDRF release also appeared to be important for modulation of vasoconstrictor responses to 5-hydroxytryptamine, endothelin-1, bradykinin, and angiotensin II and was more important than prostaglandin release for mediating the vasodilator effects of adenosine triphosphate. Reduced EDRF release, consequent to endothelial cell damage, could make an important contribution to the increased fetal placental vascular resistance associated with pre-eclampsia and fetal growth retardation.

Analysis of the responses of the fetal vessels of human perfused placental lobules to acute infusions of arachidonic acid

The vasodilatory response to arachidonic acid by the fetal vessels of human perfused placental lobules, in which tone had been increased by infusion of the thromboxane A2 mimetic U46619, was significantly reduced in the presence of the prostacyclin (PGI2) synthetase inhibitor tranylcypromine compared with saline infusion controls. HPLC analysis of the fetal effluent from human perfused placental lobules, in which radiolabelled arachidonic acid had been infused, identified two peaks of activity. The first peak displayed an elution profile similar to that of a 6-keto-PGF1 alpha standard; the presence of 6-keto-PGF1 alpha in this peak was confirmed by RIA. The second peak had an elution profile similar to that of an arachidonic acid standard. These results suggest that the vasodilatory response to the fetal vessels of human perfused placental lobules to acute infusions of arachidonic acid is mediated, at least in part, by the synthesis of PGI2. These data are consistent with the hypothesis that PGI2 may be involved in the maintenance of low vascular resistance of the fetal placenta in utero.