Placental miRNAs Targeting Cellular Stress Response Pathways Are Highly Expressed in Non-Hispanic Black People

The expression of chromosome 19 miRNA cluster members during insulin sensitivity changes in pregnancy

HYPOTHESIS

Declines in insulin sensitivity during pregnancy important for fetal growth are associated with impairments in skeletal muscle post-receptor insulin signaling. The primary initiator of these changes is unknown but believed to originate in the placenta. We hypothesize that placental miRNAs are associated with maternal sensitivity changes and impact insulin-sensitive mechanisms in target tissues in vitro.

METHODS

Using qPCR, miRNA expression was measured in plasma in early (12-16 wk) and late (34-36 wk) gestation (N = 39) and placental tissue at term (37-41 weeks) (N = 142) collected from independent cohorts. Insulin-sensitive glucose uptake was measured in human skeletal muscle myoblasts exposed to miRNA mimics in vitro. Multi-linear and binomial regression models were generated to test for associations between miRNAs, insulin sensitivity and fetal growth outcomes, adjusting for relevant clinical variables. P < 0.05 was considered significant.

RESULTS

Placental expression of chromosome 19 miRNA cluster (C19MC) members was higher in patients with obesity and positively correlated with maternal HOMA-IR (Homeostatic Model Assessment for Insulin Resistance; miR-516b-5p, miR-517a-3p, miR-1283). Placental expression of miR-517a-3p was higher in offspring with high adiposity and birthweight. Plasma miR-517a-3p in early and late pregnancy was related to decreases in insulin sensitivity during pregnancy. Mimics for miR-517a-3p and miR-524-3p both impaired insulin-sensitive glucose uptake in human skeletal myocytes in vitro.

DISCUSSION

Our findings based on data from two independent pregnancy cohorts and in vitro studies support a role for members of the C19 cluster of miRNAs - particularly miR-517a-3p - in physiological changes in insulin sensitivity over pregnancy, which may impact fetal growth.

Epigenetic Responses to Nonchemical Stressors: Potential Molecular Links to Perinatal Health Outcomes

PURPOSE OF REVIEW

We summarize the recent literature investigating exposure to four nonchemical stressors (financial stress, racism, psychosocial stress, and trauma) and DNA methylation, miRNA expression, and mRNA expression. We also highlight the relationships between these epigenetic changes and six critical perinatal outcomes (preterm birth, low birth weight, preeclampsia, gestational diabetes, childhood allergic disease, and childhood neurocognition).

RECENT FINDINGS

Multiple studies have found financial stress, psychosocial stress, and trauma to be associated with DNA methylation and/or miRNA and mRNA expression. Fewer studies have investigated the effects of racism. The majority of studies assessed epigenetic or genomic changes in maternal blood, cord blood, or placenta. Several studies included multi-OMIC assessments in which DNA methylation and/or miRNA expression were associated with gene expression. There is strong evidence for the role of epigenetics in driving the health outcomes considered. A total of 22 biomarkers, including numerous HPA axis genes, were identified to be epigenetically altered by both stressors and outcomes. Epigenetic changes related to inflammation, the immune and endocrine systems, and cell growth and survival were highlighted across numerous studies. Maternal exposure to nonchemical stressors is associated with epigenetic and/or genomic changes in a tissue-specific manner among inflammatory, immune, endocrine, and cell growth-related pathways, which may act as mediating pathways to perinatal health outcomes. Future research can test the mediating role of the specific biomarkers identified as linked with both stressors and outcomes. Understanding underlying epigenetic mechanisms altered by nonchemical stressors can provide a better understanding of how chemical and nonchemical exposures interact.