Fetal ovine skeletal and cardiac muscle transcriptomics are differentially altered by increased maternal cortisol during gestation

Abstract

We have previously found that in utero exposure to excess maternal cortisol (1 mg/kg/day) in late gestation increases the incidence of stillbirth during labor and produces fetal bradycardia at birth. In the interventricular septum, mitochondrial DNA (mt-DNA) was decreased, and transcriptomics and metabolomics were consistent with altered mitochondrial metabolism. The present study uses transcriptomics to model effects of increased maternal cortisol on fetal biceps femoris. Transcriptomic modeling revealed that pathways related to mitochondrial metabolism were downregulated, whereas pathways for regulation of reactive oxygen species and activation of the apoptotic cascade were upregulated. Mt-DNA and the protein levels of cytochrome C were significantly decreased in the biceps femoris. RT-PCR validation of the pathways confirmed a significant decrease in SLC2A4 mRNA levels and a significant increase in PDK4, TXNIP, ANGPTL4 mRNA levels, suggesting that insulin sensitivity of the biceps femoris muscle may be reduced in cortisol offspring. We also tested for changes in gene expression in diaphragm by rt-PCR. PDK4, TXNIP, and ANGPTL4 mRNA were also increased in the diaphragm, but SLC2A4, cytochrome C protein, and mt-DNA were unchanged. Comparison of the change in gene expression in biceps femoris to that in cardiac interventricular septum and left ventricle showed few common genes and little overlap in specific metabolic or signaling pathways, despite reduction in mt-DNA in both heart and biceps femoris. Our results suggest that glucocorticoid exposure alters expression of nuclear genes important to mitochondrial activity and oxidative stress in both cardiac and skeletal muscle tissues, but that these effects are tissue-specific.

Pharmacokinetic and Biochemical Profiling of Sodium Dichloroacetate in Pregnant Ewes and Fetuses

“…We previously found that sheep fetuses exposed to hypercortisolemia in late pregnancy suffered an increased rate of stillbirth and perinatal mortality (Keller-Wood et al, 2014); this effect of a chronic increase in cortisol is similar to the observation that the risk of late gestation stillbirth is increased in human pregnancies complicated by chronic maternal hypercortisolemia secondary to maternal stress (László et al, 2013;Silver and Ruiz, 2013) or by maternal Cushing's syndrome (Brue et al, 2018). Transcriptomic and metabolic analyses of heart and skeletal muscle from the fetuses and newborns from our ovine model of gestational hypercortisolemia suggested that inhibition of mitochondrial metabolism (Richards et al, 2014;Walejko et al, 2019;Joseph et al, 2020) may be a predisposing factor in the development of bradycardia and altered ECG patterns at the time of delivery (Antolic et al, 2018).…”

Glucocorticoid maturation of mitochondrial respiratory capacity in skeletal muscle before birth

“…In the current study, raising cortisol level to prepartum values by cortisol infusion before the normal surge increased mitochondrial content, specifically in the SDF. In a recent study, longer-term treatment of pregnant ewes with cortisol for the last 25 days of pregnancy reduced mitochondrial DNA content of the fetal BF and heart at term ( Joseph et al 2020 ). Similarly, maternal corticosterone treatment of rats at mid-pregnancy decreased placental mitochondrial density ( Bartho et al 2019 ).…”

Metabolic Consequences of Glucocorticoid Exposure before Birth

“…Transcriptome and metabolome analyses of the ovine placenta after 25 days of maternal cortisol infusion also indicate that there are changes in amino acid metabolism that involve glutamate and the degradation and biosynthesis of branched chain amino acids [ 64 ]. Similar changes in the metabolism of branched chain amino acids are also seen in ovine cardiac and skeletal muscle before and at birth after prolonged maternal hypercortisolemia [ 65 , 94 ].…”