Interstage Single Ventricle Heart Disease Infants Show Dysregulation in Multiple Metabolic Pathways: Targeted Metabolomics Analysis

Abstract

Background: Infants with SVHD experience morbidity related to pulmonary vascular inadequacy. Metabolomic analysis involves a systems biology approach to identifying novel biomarkers and pathways in complex diseases. The metabolome of infants with SVHD is not well understood and no prior study has evaluated the relationship between serum metabolite patterns and pulmonary vascular readiness for staged SVHD palliation.

Objectives: The purpose of this study was to evaluate the circulating metabolome of interstage infants with single ventricle heart disease (SVHD) and determine whether metabolite levels were associated with pulmonary vascular inadequacy.

Methods: This was a prospective cohort study of 52 infants with SVHD undergoing Stage 2 palliation and 48 healthy infants. Targeted metabolomic phenotyping (175 metabolites) was performed by tandem mass spectrometry on SVHD pre-Stage 2, post-Stage 2, and control serum samples. Clinical variables were extracted from the medical record.

Results: Random forest analysis readily distinguished between cases and controls and preoperative and postoperative samples. Seventy-four of 175 metabolites differed between SVHD and controls. Twenty-seven of 39 metabolic pathways were altered including pentose phosphate and arginine metabolism. Seventy-one metabolites differed in SVHD patients between timepoints. Thirty-three of 39 pathways were altered postoperatively including arginine and tryptophan metabolism. We found trends toward increased preoperative methionine metabolites in patients with higher pulmonary vascular resistance and higher postoperative tryptophan metabolites in patients with greater postoperative hypoxemia.

Conclusions: The circulating metabolome of interstage SVHD infants differs significantly from controls and is further disrupted after Stage 2. Several metabolites showed trends toward association with adverse outcomes. Metabolic dysregulation may be an important factor in early SVHD pathobiology.

Keywords: Glenn operation; arginine; congenital heart disease; methionine; pulmonary hypertension; tryptophan.

Graphical abstract

Figure 1

Metabolomic Changes Between Infants With Single Ventricle Heart Disease and Controls (A) Volcano plot demonstrating individual metabolites compared between cases and controls. Metabolites with false discovery rate (FDR) <0.05 are labeled in orange, while those with FDR ≥0.05 are black. Positive fold change indicates higher levels in cases than controls. (B) Pathway analysis delineates metabolic pathways that are altered in cases compared to controls. Larger values on Y axis indicated a greater degree of statistical significance in each pathway’s metabolite levels. Larger values on the X axis indicate that the measured metabolites are more impactful to that particular pathway. (C) Individual metabolites identified as the most important features distinguishing cases from controls on random forest analysis. (D) Multidimensional scaling plot depicts the results of random forest analysis. With high accuracy, the circulating metabolome distinguishes cases from controls after correction for batch effect.

Figure 2

Metabolomic Changes Between Infants With SVHD Pre-Stage 2 and Post-Stage 2 (A) Volcano plot demonstrating individual metabolites compared between pre-stage 2 and post-stage 2. Metabolites with FDR <0.05 are labeled in orange, while those with FDR ≥0.05 are black. Positive fold change indicates higher levels in postoperative samples than preoperative. (B) Pathway analysis delineates metabolic pathways that are altered in postoperative samples compared to preoperative. Larger values on Y axis indicated a greater degree of statistical significance in each pathway’s metabolite levels. Larger values on the X axis indicate that the measured metabolites are more impactful to that particular pathway. (C) Individual metabolites identified as the most important features distinguishing preoperative from postoperative samples on random forest analysis. (D) Multidimensional scaling plot depicts the results of random forest analysis. With high accuracy, the circulating metabolome distinguishes pre-stage 2 from post-Stage 2 samples after correction for batch effect.

Figure 3

Association Between Metabolites and Outcomes (A) Volcano plot depicting the association between metabolites measured in the preoperation systemic vein and indexed pulmonary vascular resistance. Positive fold change suggests higher metabolite levels in subjects with higher PVRi. (B) Volcano plot depicting the association between metabolites measured in the systemic vein at 2 hours postoperation and percent of the first 48 postoperative hours spent with oxygen saturation below 70%. Positive fold change suggests higher metabolite levels in subjects with greater hypoxemia burden.

Central Illustration

Metabolomic Changes in Infants Undergoing Stage 2 Single Ventricle Palliation (Left) Volcano plot demonstrating individual metabolites compared between cases and controls. (Right) Volcano plot demonstrating individual metabolites compared between pre-Stage 2 and post-Stage 2. Metabolites with FDR <0.05 are labeled in orange. Select altered metabolites of interest and metabolic pathways are noted.