Multiomics approach reveals metabolic changes in the heart at birth

Abstract

During late gestation, the fetal heart primarily relies on glucose and lactate to support rapid growth and development. Although numerous studies describe changes in heart metabolism to utilize fatty acids preferentially a few weeks after birth, little is known about metabolic changes of the heart within the first day following birth. Therefore, we used the ovine model of pregnancy to investigate metabolic differences between the near-term fetal and the newborn heart. Heart tissue was collected for metabolomic, lipidomic, and transcriptomic approaches from the left and right ventricles and intraventricular septum in 7 fetuses at gestational day 142 and 7 newborn lambs on the day of birth. Significant metabolites and lipids were identified using a Student’s t-test, whereas differentially expressed genes were identified using a moderated t-test with empirical Bayes method [false discovery rate (FDR)-corrected P < 0.10]. Single-sample gene set enrichment analysis (ssGSEA) was used to identify pathways enriched on a transcriptomic level (FDR-corrected P < 0.05), whereas overrepresentation enrichment analysis was used to identify pathways enriched on a metabolomic level ( P < 0.05). We observed greater abundance of metabolites involved in butanoate and propanoate metabolism, and glycolysis in the term fetal heart and differential expression in these pathways were confirmed with ssGSEA. Immediately following birth, newborn hearts displayed enrichment in purine, fatty acid, and glycerophospholipid metabolic pathways as well as oxidative phosphorylation with significant alterations in both lipids and metabolites to support transcriptomic findings. A better understanding of metabolic alterations that occur in the heart following birth may improve treatment of neonates at risk for heart failure.

Chronic maternal cortisol excess during late gestation leads to metabolic alterations in the newborn heart

“…Following birth, the heart gradually transitions from utilizing lactate and glucose as primary energy substrates in utero to fatty acids, which is sustained in the healthy heart into adult life (2,32,33). Previous work in our laboratory has found that transcripts for BCAA degradation are enriched in fetal hearts in healthy sheep compared with newborn hearts on the first day of life (51). Additionally, studies in adult human hearts has suggested that BCAA degradation is diminished in the failing heart (27,48).…”

“…Nuclear magnetic resonance metabolomics analysis. HR-MAS proton nuclear magnetic resonance ( 1 H-NMR) was used to determine metabolites present in RV and LV free walls and intraventricular septum as previously described (51). Metabolites identified with this technique were not found to be significantly altered between different areas of the heart and were therefore treated as biological replicates, effectively defining cardiac tissue as our experimental unit (29) (Supplemental Table S1; Supplemental Material for this article is available online at the Journal website).…”

“…For cardiac tissue, one pooled control (n ϭ 2) and one pooled cortisol (n ϭ 2) specimen were created by pooling 100 mg of cardiac tissue. The two tissue samples were homogenized and prepared for NMR metabolomics analysis as previously described (51). For serum, one pooled maternal (from 4 ewes) and one pooled fetal (from 4 fetuses) specimen were each used for 2D NMR data acquisition.…”

“…Lipidomic analysis of cardiac specimens. Tissue specimens were prepared for lipidomic analysis as previously described (51). Internal and injections standard mixtures are listed in Supplemental Table S3.…”

Diabetes Leads to Alterations in Normal Metabolic Transitions of Pregnancy as Revealed by Time-Course Metabolomics

“…For metabolites with significant interaction effects between trimester and diabetes, a Tukey–Kramer post-hoc test was conducted to determine significant alterations over each trimester ( p < 0.05). Pathway analysis was conducted using Metaboanalyst with significant metabolites from each linear mixed-effects model as previously described [ 75 , 77 ]. Pathways not related to human metabolism or containing D-amino acids were removed from the results.…”