Sexual dimorphism in miR-210 expression and mitochondrial dysfunction in the placenta with maternal obesity

BACKGROUND: Maternal obesity is a major problem in obstetrics, and the placenta is involved in obesity-related complications via its roles at the maternal-fetal interface. We have recently shown a causative role for micro(mi) RNA-210, a so called 'hypoxamir' regulated by HIF-1 alpha, in mitochondrial dysfunction in placentas from women with preeclampsia. We also reported mitochondrial dysfunction in placentas with maternal obesity. Here we hypothesized that expression of miR-210 is dysregulated in the placentas with obesity. METHODS: Placentas from uncomplicated pregnancies were collected at term from healthy weight or control (CTRL, pre-pregnancy body mass index (BMI) <25), overweight (OW, BMI = 25-24.9) and obese (OB, BMI > 30) women following C-section with no labor. Expression of miRNA-210 and its target genes was measured by reverse transcription-PCR and Western Blot, respectively. Mitochondrial respiration was assessed by Seahorse Analyzer in syncytiotrophoblast (ST) 72 h after cytotrophoblast isolation. RESULTS: Expression of miR-210 was significantly increased in placentas of OB and OW women with female but not male fetuses compared with CTRL placentas of females. However, expression of HIF-1 alpha in these placentas remained unchanged. Levels of tumor-necrosis factor-alpha (TNF alpha) were increased in OW and OB placentas of females but not males, and in silico analysis suggested that activation of miR-210 expression in these placentas might be activated by NF kappa B1 (p50) signaling. Indeed, chromatin Immunoprecipitation assay showed that NFkB1 binds to placental miR-210 promoter in a fetal sex-dependent manner. Female but not male STs treated with TNF alpha showed overexpression of miR-210, reduction of mitochondrial target genes and decreased mitochondrial respiration. Pre-treatment of these STs with small interfering RNA to NFkB1 or antagomiR-210 prevented the TNF alpha-mediated inhibition of mitochondrial respiration. CONCLUSIONS: Our data suggest that the inflammatory intrauterine environment associated with maternal obesity induces an NF kappa B1-mediated increase in miR-210 in a fetal sex-dependent manner, leading to inhibition of mitochondrial respiration and placental dysfunction in the placentas of female fetuses.