Placental mRNA and miRNA dynamics associated with lipid metabolism pathways in pregnancies affected by obesity

Abstract

Introduction: Maternal obesity (pregravid body mass index >30 kg/m²), which has reached epidemic levels in the US, increases the incidence of cardiovascular disease and all cause premature death in the offspring. The placenta modulates fetal access to lipids and other nutrients and is considered a key player in fetal growth and maturation. However, the complex interplay between dysregulated metabolism in mothers with obesity and placental pathways mediating impacts on fetal development that predispose offspring to morbidities later in life, is poorly understood.

Methods: We used unbiased Whole Genome Correlation Network Analysis (WGCNA) in 39 full-term unlabored placentas from mothers affected by obesity to explore relationships between coding and non-coding placental transcripts with maternal and fetal metabolic variables.

Results: We identified positive correlations between members of the Rho network, a key inflammation regulator, with maternal leptin and cord blood free fatty acids (cbFFA). Furthermore, we identified negative correlations between epigenetic regulators and the lipid metabolism drivers SMUG1 and CDS1, with cbFFA. A set of placental miRNAs showed positive correlations with cbFFA. Using mirTarRnaSeq, an R/Bioconductor package, we predicted interactions between placental coding genes and miRNA, which correlated negatively and positively with cbFFA, respectively. Several FFA-associated miRNAs (miR-23b cluster, -168, -138, -6825, -6845) have been previously associated with obesity in animal models and human cohorts.

Discussion: Further studies are required to investigate the role that the Rho network plays in placental inflammation and the link between miRNAs and the predisposition towards cardiovascular diseases in the offspring of obese mothers.

Keywords: free fatty acids; maternal obesity; microRNA; placenta; transcriptome.

Figure 1

Coding gene modules-metabolic traits correlations in placentas from pregnancies affected by obesity. Using Whole Genome Correlations Network Analysis (WGCNA), we established correlations between placental coding-genes with similar patterns of expression (Modules) with metabolic traits of the Maternal-Fetal dyad. Each correlation contains a coefficient of correlation and a (p-value). Red correlations are positive, Blue correlations are negative. Highlighted RED: significant positive correlations; Highlighted Blue: significant (p <0.05) negative correlations. cbFFA, cord blood Fatty-Acids; cblep cord blood leptin; neoadp, neonatal adiposity; bwt, birth weight; mffa, Maternal Free Fatty-Acids; mlep, Maternal Leptin; preBMI, Maternal Pre-pregnancy BMI.

Figure 2

String analysis of the RHO GTPases network components (GTPases + effectors) identified in MEred, MEbrown and MEpurple modules. Note the central functional position occupied by CDC42. Colored nodes: query proteins and first shell of interactors. line: Curated database. line: Experimentally determined. lines: Predicted interactions.

Figure 3

String Analysis of selected components of the Epigenome expressed in the MEgreen. Colored nodes: query proteins and first shell of interactors. line: curated database. line: Experimentally determined. lines: predicted interactions.

Figure 4

Panels (a–d) Linear regression between components of the methylation machinery and miRNAs. Using mirTarRnaSeq we predicted linear regression between miRNAs in the MEgreen+METurquoise modules (positively correlated with cbFFA) and components of the Epigenetic machinery contained in the MEgreen module (negatively correlated with cbFFA). All the miRNA-gene interactions reported have a p-value <0.05. Panel (A), upper left DNMT3A; Panel (B), upper right MBD4; Panel (C), lower left MTA3; Panel (D), lower right KDM6. Yellow: miR-6845 and -6825 previously identified in the screening for obesity in pediatric populations; Orange: miR-4632 and Dark Orange: miR-135b have been identified in experimental models of obesity [37]; Red: miR-196b, this miRNA is considered a master regulator of adipogenesis Azure: miR-23b. This gene is known to regulate KDM6 and it is overexpressed in obesity [40]; Dark Azure: miR-24, was overexpressed in livers of mice with high fat diet; Red: miR-196b, this miRNA is considered a master regulator of adipogenesis; Black: miR-32 was shown to be overexpressed in patients with hepatic steatosis.

Figure 5

Panels (a, b) Linear regression between Lipid metabolism genes and miRNAs. Using mirTarRnaSeq we predicted linear regression between miRNAs in the MEgreen+METurquoise modules (positively correlated with cbFFA) with genes involved in Lipid metabolism contained in the MEgreen module (negatively correlated with cbFFA). All the miRNA-gene interactions reported have a p-value <0.05. Panel (A), upper CDS1; Panel (B), lower SMUG1. Azure: miR23b. This gene is known to be overexpressed in obesity; Red: miR-196b, this miRNA is considered a master regulator of adipogenesis; Pink: miRNA-138 this miRNA is closing involved in targeting adipogenesis Lipoprotein Lipase, a key lipogenic enzyme in ahMSCs. The datasets for this study can be found in the Harvard Dataverse: https://doi.org/10.7910/DVN/LOIDQS.