Differential Expression Of Placental 11β-Hydroxysteroid Dehydrogenase As A Key Determinant Of Fetal Environment In Pregnancies With Gestational Diabetes Mellitus

Objective: Our current studies were designed to investigate placental type 1 and 2 of 11β-hydroxysteroid dehydrogenase (11β-HSD1 and 11β-HSD2) gene and protein expression among pregnant women either with gestational diabetes mellitus (GDM) or normal glucose tolerance (NGT). In addition, correlation between fetal growth and maternal and fetal cortisol levels with placental 11β-HSDs was analyzed.Methods: 1. Age matched pregnant women with gestational diabetes mellitus (GDM group, n=23) and normal glucose tolerance (NGT group, n=22) were recruited at the 2nd Affiliated Hospital, CQMU. The blood from maternal and umbilical venous was collected and placental tissues were dissected. 2. The biochemical index and fasting glucose of maternal blood were analyzed by automatic biochemical analyzer and glucose oxidase. Cortisol and insulin levels were examined by chemiluminescence and radioimmunoassay (RIA). The homeostasis model assessment of insulin resistance index (HOMA-IR) and insulin secretion index were performed as literatures. 3. Immunohistochemical assay were applied for measurement of 11β-HSD1 and 11β-HSD2 distribution in the placenta. Real time-PCR and Western blot were applied for measurement of 11β-HSD1 and 11β-HSD2 mRNA and protein expression between NGT group and the GDM group. 4. Placental villi explants from full-term NGT pregnancy were incubated with free fatty acids , dexamethasone, insulin and their combined mixture for 24h. Real time-PCR and Western blot were used to measure 11β-HSD1 and 11β-HSD2 mRNA and protein expression in incubated placental explants.Results: 1. Compared with NGT group, fasting insulin (14.8±1.5 vs 19.8±1.7 (μU / ml)), HOMA-IR (2.8±0.3 vs 4.1±0.4), insulin secretion index (57.2±5.8 vs 83.7±7.3), maternal cortisol levels (940.3±44.2 vs 1125.0±42.8 (nmol / L)), triglycerides (3.3±0.4 vs 4.3±0.4 (nmol / L)) and BMI (26.8±0.8 vs 29.0±0.6 ( kg/m2)) from GDM group were significantly higher, respectively, P <0.05), while fasting blood glucose, cord blood cortisol ,birth weight, high density lipoprotein and low density lipoprotein did not differ between the two groups. 2. Pearson's correlation analysis between maternal vein or umbilical cord cortisol levels and fetal body weight demonstrated a negative correlation between fetal body weight with umbilical cord cortisol levels (R=-0.378, P=0.01) but not maternal vein cortisol levels. 3. 11β-HSD1 protein in the placental villi was extensively distributed in the villous unit interstitial substance, syncytiotrophoblast of villious branches, and outer syncytiotrophoblast, while 11β-HSD2 was relatively concentrated on the outer layer of syncytial trophoblast. 4. Real time-PCR and Western blot results suggest that GDM placental 11β-HSD1 mRNA and protein levels were significantly lower than the NGT group (0.56±0.09 vs 1.36±0.36 for mRNA and 0.27±0.07 vs 1.00±0.01 for protein, respectively, P <0.05). 11β-HSD2 mRNA was significantly higher than NGT group (5.17±1.02 vs 1.21±0.34, P <0.05), while no significant difference was found for 11β-HSD2 protein (1.30±0.19 vs 1.00±0.14, P> 0.05). 5. Treatment of placenta explants from NGT with palmitic acid, dexamethasone, insulin or their combination resulted in a significant drop of 11β-HSD1 and increase in 11β-HSD2. 11β-HSD1 mRNA levels in untreated, palmitic acid, dexamethasone, insulin and combined mi xture explants were : (1.00±0.01, 0.49±0.04, 0.57±0.16, 0.44±0.07, and 0.55±0.13, respectively ,P <0.05); and 11β-HSD1 protein levels were (0.99±0.01, 0.36±0.03, 0.13±0.01, 0.68±0.09, and 0.50±0.04, respectively,P <0.05). 11β-HSD2 mRNA levels in above groups were ( 1.00±0.01, 1.14±0.12, 1.43±0.12, 1.47±0.13, and 1.91±0.17, respectively, P <0.05)and protein levels were (1.04±0.04, 2.35±0.18, 4.10±0.98, 3.20±0.39, and 3.91±0.32, respectively,P <0.05)Conclusions: 1. The fasting blood glucose in GDM patients can be maintained normal through diet control and exercise, even though there are still significant insulin resistance, hyperlipidemia and hypercorticism. 2. Although GDM mothers had significant hypercorticism, fetal cord blood cortisol levels and infant body weight did not significantly changed. Birth weight was not correlated with maternal cortisols, but was negatively correlated with cord blood cortisol levels. 3. Both 11β-HSD1 and 11β-HSD2 were present in the full-term pregnancy placenta. The downregulation of 11β-HSD1 and upregulation of 11β-HSD2 participate in the maintenance of cord blood cortisol levels. High levels of circulating insulin, free fatty acids, and cortisol in GDM state are directly associated with the upregulation of 11β-HSD1 and downregulation of 11β-HSD2 in the placenta. 4. Differential expression of 11β-HSDs in GDM placenta provides a protective mechanism for the fetus throughout the adverse environment of pregnancy by limiting excessive exposure of the fetus to glucocorticoids.