Circulating factors in single ventricle congenital heart disease directly impair cardiomyocyte mitochondrial bioenergetics, and PDE5 inhibitor therapy partially reverses these abnormalities by restoring phospholipid levels, reducing reactive oxygen species, and improving energy production.
Key Findings
Results
Circulating factors from single ventricle patients impaired mitochondrial bioenergetics in primary cardiomyocytes treated with patient sera.
An established in vitro model was used whereby primary cardiomyocytes were treated with patient sera ± PDE5 inhibitor
Mitochondrial bioenergetics were evaluated using the Seahorse Bioanalyzer and a stable isotope-based enzyme activity assay
Impairments included decreased cardiolipin and other phospholipid species, impaired carnitine palmitoyltransferase activity, increased reactive oxygen species generation, and altered metabolite milieu
Relative mitochondrial copy number was quantified using reverse transcriptase-quantitative polymerase chain reaction
Results
Single ventricle patient sera caused decreased cardiolipin and other phospholipid species in cardiomyocytes.
Mass spectrometry-based lipidomics and metabolomics were used to assess phospholipid and metabolite changes
Cardiolipin reduction is consistent with prior findings that the failing SV myocardium is characterized by impaired mitochondrial bioenergetics
Cardiolipin is a mitochondria-specific phospholipid critical for mitochondrial membrane integrity and bioenergetic function
Additional phospholipid species beyond cardiolipin were also decreased
Results
Carnitine palmitoyltransferase (CPT) activity was impaired in cardiomyocytes exposed to single ventricle patient circulating factors.
CPT activity was assessed using a stable isotope-based enzyme activity assay
CPT is a key enzyme in fatty acid oxidation and mitochondrial energy metabolism
Impaired CPT activity suggests disruption of fatty acid transport into mitochondria as a mechanism of bioenergetic dysfunction
This finding implicates circulating factors as drivers of metabolic remodeling in single ventricle congenital heart disease
Results
Reactive oxygen species generation was increased in cardiomyocytes treated with single ventricle patient sera.
Increased ROS generation was identified as one of the fundamental changes in cardiomyocyte bioenergetics driven by circulating factors
Increased ROS is consistent with mitochondrial dysfunction and impaired electron transport chain function
ROS increase was partially reversed by PDE5 inhibitor treatment
Results
PDE5 inhibitor treatment partially rescued cardiomyocyte bioenergetic abnormalities induced by single ventricle circulating factors.
PDE5i treatment restored phosphatidylglycerol levels, which are precursors to cardiolipin synthesis
PDE5i improved energy production and normalized several metabolic intermediates
The rescue was described as partial, not complete
Results
PDE5 inhibitor therapy restored phosphatidylglycerol levels in cardiomyocytes exposed to single ventricle patient sera.
Phosphatidylglycerol is a direct precursor to cardiolipin in the mitochondrial phospholipid biosynthesis pathway
Restoration of phosphatidylglycerol suggests PDE5i may support cardiolipin synthesis capacity
This finding was identified through mass spectrometry-based lipidomics
The failing SV myocardium was previously characterized by the authors as having increased PDE5 activity and impaired mitochondrial bioenergetics
Background
The failing single ventricle myocardium is characterized by increased PDE5 activity and impaired mitochondrial bioenergetics.
This was established in prior work by the same research group and is cited as the foundation for the current study
PDE5 inhibitor therapies are increasingly used in single ventricle congenital heart disease but their direct myocardial effects remained poorly understood prior to this study
The current study extends these findings by demonstrating that systemic circulating factors contribute to pathological metabolic remodeling
Results
Circulating factors from single ventricle patients produced an altered metabolite milieu in cardiomyocytes.
Metabolomic changes were assessed using mass spectrometry-based metabolomics
PDE5i treatment normalized several metabolic intermediates that were altered by SV patient sera
The altered metabolite milieu suggests circulating factors may drive systemic metabolic dysfunction in single ventricle congenital heart disease
What This Means
This research suggests that substances circulating in the blood of patients with single ventricle (SV) heart disease — a serious congenital condition where only one pumping chamber develops — can directly harm the energy-producing machinery inside heart muscle cells. Using a laboratory model where heart cells were bathed in blood serum from SV patients, researchers found that these circulating factors disrupted mitochondria (the power plants of cells) in multiple ways: they depleted key structural lipids called cardiolipins, impaired a critical enzyme needed to burn fat for fuel, and increased damaging molecules called reactive oxygen species. Together, these changes compromised the ability of heart cells to produce energy efficiently.
The study also tested whether a class of drugs called PDE5 inhibitors — which are increasingly prescribed to SV patients — could protect against these harmful effects. PDE5 inhibitors partially reversed many of the metabolic problems: they restored levels of a lipid that feeds into cardiolipin production, reduced oxidative stress, improved the fat-burning enzyme's activity, and normalized several metabolic byproducts. The rescue was incomplete, meaning these drugs help but do not fully correct the underlying dysfunction.
This research suggests that the blood itself in SV heart disease carries disease-promoting signals that can impair heart cell metabolism independent of structural heart problems, and that metabolic modulation — including but potentially not limited to PDE5 inhibitor therapy — may be a valuable therapeutic strategy for these patients. These findings could inform future clinical trials testing metabolic therapies in the SV population, where long-term outcomes remain poor despite improving surgical care.
Garcia A, Pietra A, Turner M, Da Silva J, Baybayon-Grandgeorge A, Sparagna G, et al.. (2026). Circulating Factors in Single Ventricle Heart Disease Impair Cardiomyocyte Bioenergetics, With Partial Rescue by PDE5 Inhibition.. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.125.042725