Medizinische Universität Graz - Research portal
Selected Publication:
Sun, Y.
The Impact of Gestational Diabetes Mellitus on Regulating Cholesterol Homeostasis in Human Fetoplacental Endothelium
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Graz Medical University; 2018. pp.111.
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- Authors Med Uni Graz:
- Sun Yidan
- Advisor:
- Panzenboeck Ute
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- Abstract:
- Background: Gestational diabetes mellitus (GDM) is associated with altered glucose, lipid and cholesterol metabolism in maternal circulation, which can significantly modify the key features of placental function. Researches in our group have demonstrated that cholesterol can be efficiently delivered into the fetal circulation across fetoplacental endothelial cells via ATP-binding cassette transporters (ABC) A1 and ABCG1. However, the effect of GDM on modulating cholesterol metabolism in placental vasculature is not well understood. The objective of this project is to investigate changes in cholesterol metabolism in human fetoplacental arterial endothelial cells (HPEC) under GDM condition. Using HPEC cells isolated from fetal arterial vessels of term placentas obtained from GDM or healthy pregnancies, we investigated cholesterol metabolism including cholesterol biosynthesis, esterification and cholesterol efflux and verified the expression levels of several genes and proteins involved in cholesterol metabolism. Methods: H2DCFDA fluorescent dye was used to measure levels of cellular reactive oxygen species (ROS). Oxysterols in HPEC and cord blood were detected by gas chromatography–mass spectrometry (GC-MS) method. Genes and proteins expression were determined by real-time PCR and immunoblotting, respectively. [3H]-Cholesterol was used to label HPEC and radioactivity of cholesterol efflux was detected by ¿-counting. The assay for cholesterol biosynthesis and esterification was detected by using [14C]-acetate as cholesterol precursor. Results: GDM increased the production of ROS in HPEC and resulted in the increase levels of oxysterols generated from ROS pathways in HPEC. ROS-generated oxysterols were simultaneously elevated in cord blood of GDM neonates. Levels of ABCA1 and ABCG1 mRNA and protein expression were upregulated after Liver-X receptor (LXR) activation by the treatment with TO901319, 7-ketocholesterol, or 7ß-hydroxycholesterol in control HPEC. LXR activation promoted cholesterol release from HPEC to apoA-I and HDL3. GDM upregulated the levels of ABCA1 and ABCG1 mRNA and protein expression and increased their mediated cholesterol release to apoA-I and HDL3, respectively. Inhibition of LXR activity in GDM HPEC by the LXR antagonist GGPP decreased LXR induced ABCA1 and ABCG1 expression and reduced cholesterol release to apoA-I and HDL3 mediated by ABCA1 and ABCG1, respectively. Comparable total cellular cholesterol content was determined between control and GDM HPEC, while GDM enhanced cholesterol biosynthesis by upregulating the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and sterol O-acyltransferase 1 (SOAT1) mRNA and protein levels. Preliminary analysis of DNA methylation levels in GDM and control HPEC indicates that the cholesterol metabolism related adjustments found in HPEC from GDM pregnancies might be mediated via epigenetic mechanisms. Conclusion: Our results suggest that GDM modulates cellular cholesterol homeostasis in HPEC via LXR activation mechanism and the modulated cholesterol homeostasis helps to maintain the placenta-blood barrier functionality of fetoplacental endothelial cells.