Analysis of correlations between the placental expression of glucose transporters GLUT-1, GLUT-4 and GLUT-9 and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus

Purpose: The aim of the study was to analyze the correlations between the expression of glucose transporters GLUT-1, GLUT-4, and GLUT-9 in human term placenta and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus (DM).

Materials and methods: Placental samples were obtained from healthy control (n?=?25) and diabetic pregnancies, including diet-controlled gestational diabetes mellitus (GDMG1) (n?=?16), insulin-controlled gestational diabetes mellitus (GDMG2) (n?=?6), and pregestational DM (PGDM) (n?=?6). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected glucose transporter proteins. For the purposes of correlation analysis, the following parameters were selected: type of diabetes, gestational age, maternal prepregnancy body mass index (BMI), gestational weight gain, third trimester glycated hemoglobin concentration, placental weight, fetal birth weight (FBW) as well as ultrasonographic indicators of fetal adiposity, including subscapular (SSFM), abdominal (AFM), and midthigh (MTFM) fat mass measurements.

Results: In the PGDM group, the analysis demonstrated positive correlations between the placental expression of GLUT-1, GLUT-4, and GLUT-9 and FBW, AFM, and SSFM measurements (p?p?p?p?Conclusions: The study results revealed that placental expression of GLUT-1, GLUT-4, and GLUT-9 may be involved in the intensification of the fetal growth in pregnancies complicated by GDM/PGDM.     

Effect of albumin on transplacental transfer and distribution of rosiglitazone and glyburide

Objective.?The aims of this investigation were (i) to determine the rate and extent of rosiglitazone transfer across term human placenta, and (ii) to determine the effect of human serum albumin (HSA) on rosiglitazone and glyburide transfer and distribution.

Methods.?These aims were achieved by utilizing the technique of dual perfusion of placental lobule (DPPL). Each hypoglycemic drug was coperfused with the marker compound antipyrine (AP). In each experiment, the [³H]-isotope of the hypoglycemic drug and the [¹⁴C]-isotope of AP were added to enhance the detection limits of each drug. Human serum albumin (HSA) was added to both the maternal and fetal circuits in the experiments in which it was investigated.

Results.?Transplacental transfer of rosiglitazone and glyburide from the maternal to fetal circuits in media devoid of HSA was similar. However, the addition of HSA to the maternal and fetal circuits had different effects on the transfer and distribution of the two drugs, though their binding to HSA (99.8%) was almost identical. HSA increased the maternal (M) to fetal (F) transfer of rosiglitazone, as revealed by an increase in its F/M concentration ratio from 0.17 ± 0.01 (in the absence of albumin) to 0.33 ± 0.07 (p < 0.001). Moreover, the addition of albumin decreased the amount of rosiglitazone retained by placental tissue from 539 ± 148 to 60 ± 8 ng/g (p < 0.001). Conversely, the addition of HSA to the perfusion media resulted in a decrease in glyburide transfer, as revealed by the change of its F/M concentration ratio from 0.09 ± 0.02 (in the absence of albumin) to 0.03 ± 0.01 (p < 0.01). However, similar to rosiglitazone, glyburide retention by the tissue decreased from 103 ± 26 to 19 ± 6 ng/g (p < 0.001).

Conclusions.?These data indicate that the binding of the two drugs to albumin, though similar, is only one of the factors that could affect their placental transfer and distribution.     

The role of placental breast cancer resistance protein in the efflux of glyburide across the human placenta

Gestational diabetes mellitus is a common medical complication in pregnancy. Recent findings demonstrate that glyburide is effluxed against a concentration gradient from the fetal to the maternal circulation. However, the transport systems involved in the active efflux of glyburide in the human placenta have not yet been identified. The ATP-binding cassette transporter, breast cancer resistance protein (BCRP), is highly expressed in placental syncytiotrophoblast suggesting it may play a role in protecting the fetus from drug toxicity. The objective of the present study was to determine whether BCRP participates in the transport of glyburide across the human placenta. The placental transfer of glyburide in the presence of specific BCRP inhibitor, nicardipine, was investigated using the ex vivo dual perfusion system of isolated human placental lobules. In a closed experiment, glyburide was added (200ng/mL) to the maternal and fetal circulations and the BCRP inhibitor (20muM) was added to the maternal circulation. Samples were taken during pre-control, experimental, and post-control periods for measurement of glyburide and markers of tissue viability. Results obtained from perfusions (n=4) in the presence of the BCRP inhibitor show a significant increase in the mean fetal-to-maternal concentration ratio of glyburide determined at 180min, 0.56+/-0.06, when compared to the mean ratio obtained in the absence of inhibitor, 0.32+/-0.06 (p=0.04). These data indicate that nicardipine partially blocked the transfer of glyburide across the whole placenta through its inhibition of BCRP. This is the first ex vivo evidence that BCRP actively transports glyburide.     

孕前糖尿病围孕期咨询和评估及降糖药应用

孕前糖尿病占所有妊娠合并糖尿病的5%~10%,妊娠前咨询内容包括了解血糖水平、评估慢性并发症及合并症以确定合适的妊娠时机。资料表明,相对比较安全的孕期口服降糖药是格列本脲和二甲双胍,目前仍推荐孕期使用胰岛素控制血糖。     

Transport of glyburide by placental ABC transporters: implications in fetal drug exposure

Much evidence has demonstrated that a number of ATP-binding cassette (ABC) efflux transporters including P-glycoprotein (PGP), the multidrug resistance-associated proteins (MRPs) and the breast cancer resistance protein (BCRP) are highly expressed in placental tissues and are believed to profoundly limit the passage of therapeutic or toxic xenobiotics to the fetus. Recent studies indicate that the oral hypoglycemic glyburide does not cross the human placenta to an appreciable extent. Our objective was to identify placental transporters potentially involved in limiting the transplacental transfer of glyburide to the fetus. Thus, [(3)H]-glyburide transport was examined in BCRP, PGP, MRP1, MRP2 and MRP3 over-expressing cell lines in the presence or absence of specific inhibitors. Our results demonstrated significant increases in the intracellular accumulation of [(3)H]-glyburide in BCRP and MRP3 over-expressing cells in the presence of the inhibitors novobiocin and indomethacin, respectively. PGP inhibition with verapamil or MRP inhibition with indomethacin did not affect [(3)H]-glyburide accumulation in the PGP or MRP2 over-expressing cell lines and only limited changes were seen in the MRP1 over-expressing cell line. On the other hand, glyburide was found to significantly inhibit MRP1-, MRP2- and MRP3-mediated efflux of 5-carboxyfluorescein diacetate and PGP-mediated transport of rhodamine 123. Our evidence is the first to clearly indicate that glyburide is preferentially transported by BCRP and MRP3.     

Role of equilibrative adenosine transporters and adenosine receptors as modulators of the human placental endothelium in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a diseases that alters human placenta macro and microvascular reactivity as a result of endothelial dysfunction. The human placenta is a highly vascularized organ which lacks innervation, so blood flux is governed by locally released vasoactive molecules, including the endogenous nucleoside adenosine and the free radical nitric oxide (NO). Altered adenosine metabolism and uptake by the endothelium leads to increased NO synthesis which then turns-off the expression of genes coding for a family of nucleoside membrane transporters belonging to equilibrative nucleoside transporters, particularly isoforms 1 (hENT1) and 2 (hENT2). This mechanism leads to increased extracellular adenosine and, as a consequence, activation of adenosine receptors to further sustain a tonic activation of NO synthesis. This is a phenomenon that seems operative in the placental macro and microvascular endothelium in GDM. We here summarize the findings available in the literature regarding these mechanisms in the human feto-placental circulation. This phenomenon is altered in the feto-placental vasculature, which could be crucial for understanding GDM deleterious effects in fetal growth and development.     

Role of human placental efflux transporter P-glycoprotein in the transfer of buprenorphine, levo-alpha-acetylmethadol, and paclitaxel

This study examines the role of placental P-glycoprotein (P-gp) in the transfer of buprenorphine (BUP) and L-alpha-acetylmethadol (LAAM) across the dually perfused human placental lobule. BUP (10 ng/mL) and LAAM (35 ng/mL) were perfused in the maternal-to-fetal direction. The following kinetic parameters were determined: fetal transfer rate (TR (f)), maternal clearance (Cl (m)), and clearance index (Cl (index)). The opiates were perfused in the presence of P-gp inhibitor GF120918 (experimental group) and in its absence (control group). The kinetic parameters for the control group were set at 100% and were as follows for LAAM in the experimental group: TR (f), 123 +/- 20%, Cl (m) 116 +/- 23%, and Cl (index) 123 +/- 22% ( P < 0.05). The corresponding parameters for BUP were not different from controls. The data indicate that LAAM, but not BUP, is extruded by the efflux transporter P-gp. Therefore, it is reasonable to assume that the activity of P-gp could be one of the factors affecting the extent of fetal exposure to LAAM during pregnancy.     

Barium, TEA and sodium sensitive potassium channels are present in the human placental syncytiotrophoblast apical membrane

The human placental syncytiotrophoblast (hSTB) is a polarized epithelial structure, without paracellular routes, forming the main barrier for materno-fetal exchange. There is ample evidence suggesting the presence of potassium (K(+)) channels in the placental apical membrane; which could contribute to membrane potential and volume regulation. We have therefore examined the K(+) currents of isolated apical membranes from human term placenta using electrophysiological methods: reconstitution of ion channels from apical membranes into giant liposomes (single channel recordings, patch clamp method) or their functional transplantation into Xenopus laevis oocytes (total currents recording, voltage clamp method). Single channel recording experiments show the presence of K(+) channels in the hSTB microvillous membrane sensitive to Tetraethylammonium (TEA) and Barium (Ba(+2)). Patch current activity was diminished 50% and 70% by 20 mmol/L TEA and 5 mmol/L Ba(+2) respectively. The more frequent conductance was approximately 73pS, however several levels of current were detected suggesting the presence of more than one type of K(+) channel. In addition, sodium (Na(+)) sensitivity was detected in the patch current thus, over 10 mmol/L Na(+) reduced the seal current to 38%. These results were corroborated by the total current experiments where the K(+) current elicited in injected oocytes with apical purified membrane was blocked by Ba(+2) and TEA. The total current was also affected by Na(+), becoming larger when a Na(+)-free solution was used. Our results show the existence of at least two types of Ba(+2)-sensitive K(+) channels including a TEA sensitive sub-population, and some of them Na(+) sensitive K(+) channels. These channels could be the conductive pathways proposed previously for this cation in placental hSTB. Our novel contribution has been to successfully obtain K(+) channel recordings in systems suitable for electrophysiological studies of isolated apical membranes.     

Maternal citrulline supplementation enhances placental function and fetal growth in a rat model of IUGR: involvement of insulin-like growth factor 2 and angiogenic factors

Objective: To determine the effects of maternal citrulline supplementation on fetal growth and placental efficiency in a rat model of intrauterine growth restriction (IUGR) induced by maternal protein restriction.

Methods: Pregnant Sprague–Dawley rats were randomly assigned to three groups: NP (receiving a control 20% protein diet), LP (a 4% protein diet), or LP-CIT (an LP diet along with L-citrulline, 2?g/kg/d in drinking water). On the 15th and 21st day of gestation (GD15 and GD21, respectively), dams underwent a C-section, by which fetuses and placentas were extracted. The expression of genes involved in placental growth and angiogenesis was studied by quantitative RT-PCR.

Results: Maternal citrulline supplementation increased fetal weight at GD21, and fetal weight/placental weight ratio, an index of placental efficiency, from mid gestation (p?Igf2-P0, a placenta-specific variant of insulin-like growth factor 2 (Igf2) gene, and Vegf and Flt-1, involved in angiogenic pathways, was enhanced in the LP-CIT group (versus NP, p?p?p?Igf2-P0, Vegf, and Flt-1, respectively).

Conclusions: In a model of IUGR induced by protein deprivation, citrulline enhances fetal growth, placental efficiency, and the expression of genes involved in angiogenesis. The relevance of such effect in human pregnancies complicated by IUGR warrants further study.     

The effect of magnesium sulfate on the placental corticotropin-releasing factor (CRF) and CRF binding protein mRNA expression in perfused human placental cotyledon

Objectives: Stress stimuli and inflammation influence the secretion of the placental corticotropin-releasing factor CRF (CRF) that has a significant role in controlling the timing of birth. The CRF-binding protein (CRF-BP) binds CRF with high affinity and inhibits its activity. Magnesium sulfate (MgSO₄) has been known to ameliorate maternal, fetal and gestational tissue-associated inflammatory response. We aimed to study the effect of MgSO₄ on the CRF and CRF-BP mRNA expression levels in perfused human cotyledon.

Methods: Placentas from elective caesarean section were obtained and selected cotyledons were cannulated and dually perfused ex-vivo within 30?min. MgSO₄ (7?mg/dl) was added to the maternal reservoir. Each perfusion experiment was conducted for 180?min. At the end of the experiment, RNA was extracted from the perfused cotyledon, and RT-PCR was performed to quantify the expression of CRF and CRF-BP. Human HPRT gene served as a reference gene.

Results: Perfusion with MgSO₄ (n?=?3) induced a significantly lower CRF and higher CRF-BP mRNA expression compared to placentas perfused only with medium (n?=?3).

Conclusion: In the human placenta, MgSO₄ possibly exerts its action through different modulation on the CRF and CRF-BP expression.     

Increased chemerin concentrations in fetuses of obese mothers and correlation with maternal insulin sensitivity

Objective: The aim of this study was to determine the effect of maternal obesity and gestational diabetes mellitus (GDM) on (i) the circulating concentrations of chemerin in cord and maternal plasma, and (ii) gene expression and release of chemerin from human placenta and adipose tissue. Design: Chemerin concentrations were measured in maternal and cord plasma from 62 normal glucose tolerant women (NGT) and 69 women with GDM at the time of term elective Caesarean section. Placenta and adipose tissue expression and release of chemerin was measured from 22 NGT and 22 GDM women. Results: There was no effect of maternal obesity or GDM on maternal chemerin concentrations. Chemerin concentrations were significantly higher in cord plasma from women with maternal obesity. Cord chemerin concentrations in NGT women negatively correlated with the concentrations of maternal insulin sensitivity. There was no effect of GDM on maternal and cord chemerin concentrations, and on the release of chemerin from placenta and adipose tissue. Conclusions: At the time of term Caesarean section, preexisting maternal obesity, and its associated insulin resistance, is associated with higher cord plasma chemerin concentrations.     

Maternal growth restriction and stress exposure in rats differentially alters expression of components of the placental glucocorticoid barrier and nutrient transporters

The placenta plays a major role in the development of fetal growth restriction, which affects 10% of pregnancies and contributes to chronic adult disease risk. We have reported that female rats born small develop cardiometabolic dysfunction only during pregnancy. The physiological tests performed during pregnancy induced a maternal stress response as indicated by increased maternal corticosterone concentrations. This stress effected placental growth compared to females who were unhandled during pregnancy. Maternal stress and growth restriction independently program F2 offspring metabolic dysfunction. This study investigated the effects of maternal stress and growth restriction on placental and fetal metabolic parameters that may contribute to F2 offspring metabolic disease. Maternal growth restriction reduced F2 fetal weight whilst maternal stress reduced placental weight. Stressed mothers had reduced insulin and increased glucose concentrations, changes that were reflected in the fetus. Fetal β-cell number was reduced by maternal growth restriction, but was increased by stress exposure. Maternal growth restriction reduced placental Slc2a1, Igf2, Slc38a2 and Nr3c1 gene expression. Maternal stress decreased the expression of Slc2a1, Igf2, Slc38a2, Nr3c1, Slc2a3, Slc2a4, Nr3c2, Hsd11b2, Crhr1 and Ogt. Maternal birth weight effects on fetal weight were likely due to changes in placental nutrient transporter and Igf2 expression. On the contrary, maternal stress induced a systemic effect by altering maternal metabolic parameters, placental gene expression and fetal glucose and insulin concentrations. This study highlights the importance of informing pregnant women on effective ways to cope with stress during pregnancy to prevent adverse long-term disease outcomes in their children.     

Gestational diabetes: comparision of the carpenter and the coustan thresholds with the new thresholds of Turkish women and implications of variations in diagnostic criteria

Objective: To find optimal 100-g 3-h oral glucose tolerance test (OGTT) threshold levels for diagnosis of gestational diabetes (GDM) in Turkish pregnant women. Methods: This study was conducted with 808 women screened for GDM between 24–28 weeks of gestation using the 1-h 50-g glucose challenge test (GCT) with a subsequent 3-h 100-g OGTT for confirmation if screen was positive. The glucose values obtained were analysed by both the Carpenter and Coustan (C&C criteria) and National Diabetes Data Group (NDDG) criteria for the diagnosis of GDM and IGT. Optimal OGTT cutoff values for Turkish population were calculated by ROC curve analysis. Results: The new diagnostic criteria, based on the result of the 100-g OGTT obtained from the healthy pregnant women, were 82.5, 171.5, 151.5, and 111.5?mg/dl at 0, 1, 2, and 3?h. The prevalence of GDM was 15.7% by the new criteria, 8.1% by C&C criteria, and 5.6% by the NDDG criteria. According to new criteria, 7.7% of infants of diabetic mothers had macrosomia. This ratio was 2.6% for non diabetic women. Conclusions: Ethnic differences, enviromental factors and nutritional habits may effect development of GDM. Application of some pre-determined nomograms to all races and ethnic groups can lead errors.     

生活方式调整及药物治疗多囊卵巢综合征的临床研究

目的探讨生活方式调整、二甲双胍及罗格列酮治疗多囊卵巢综合征（PCOS）的临床疗效。方法将106例PCOS患者随机分为单纯生活方式调整（锻炼及饮食控制）、生活方式调整＋二甲双胍与生活方式调整＋罗格列酮治疗3组,分别为43、36、27例,共有60例（分别为22、21、17例）患者完成治疗,观察3组患者治疗前、后排卵情况,比较体重指数（BMI）、腰围、腰围与臀围比值（WHR）、血清睾酮、空腹真胰岛素水平、血脂、稳态模型法测定的胰岛素抵抗指数（HOMA-IR）、空腹血糖与胰岛素比值（GIR）、定量胰岛素敏感检测指数（QUICKI）的变化。结果治疗前3组患者年龄、BMI、腰围、WHR、睾酮水平、空腹真胰岛素水平、总胆固醇（TC）、甘油三酯（TG）、高密度脂蛋白．胆固醇（HDL-C）、低密度脂蛋白-胆固醇（LDL-C）比较,差异均无统计学意义（P〉0．05）。单纯生活方式调整组的43例患者中22例完成治疗,23％（5／22）恢复排卵;生活方式调整＋二甲双胍组的36例患者中21例完成治疗,43％（9／21）恢复排卵;生活方式调整＋罗格列酮组的27例患者中17例完成治疗,59％（10／17）恢复排卵。3组患者的恢复排卵率比较,差异无统计学意义（P〉0．05）;但生活方式调整＋罗格列酮组较单纯生活方式调整组恢复排卵率高,且差异有统计学意义（P〈0．05）。治疗后3组患者的BMI、腰围、WHR、睾酮、TC、TG、LDL-C、HDL-C比较,差异均无统计学意义（P〉0．05）。结论生活方式调整、二甲双胍、罗格列酮对PCOS患者均有恢复排卵作用。