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1.  C-Myc Induced Compensated Cardiac Hypertrophy Increases Free Fatty Acid Utilization for the Citric Acid Cycle 
The protooncogene C-Myc (Myc) regulates cardiac hypertrophy. Myc promotes compensated cardiac function, suggesting that the operative mechanisms differ from those leading to heart failure. Myc regulation of substrate metabolism is a reasonable target, as Myc alters metabolism in other tissues. We hypothesize that Myc-induced shifts in substrate utilization signal and promote compensated hypertrophy. We used cardiac specific Myc-inducible C57/BL6 male mice between 4–6 months old that develop hypertrophy with tamoxifen (tam) injections. Isolated working hearts and 13Carbon (13C)-NMR were used to measure function and fractional contributions (Fc) to the citric acid cycle by using perfusate containing 13C-labeled free fatty acids, acetoacetate, lactate, unlabeled glucose and insulin. Studies were performed at pre-hypertrophy (3-days tam, 3dMyc), established hypertrophy (7-days tam, 7dMyc) or vehicle control (Cont). Non-transgenic siblings (NTG) received 7-days tam or vehicle to assess drug effect. Hypertrophy was assessed by echocardiograms and heart weights. Western blots were performed on key metabolic enzymes. Hypertrophy occurred in 7dMyc only. Cardiac function did not differ between groups. Tam alone did not affect substrate contributions in NTG. Substrate utilization was not significantly altered in 3dMyc versus Cont. The free fatty acid FC was significantly greater in 7dMyc versus Cont with decreased unlabeled Fc, which is predominately exogenous glucose. Free fatty acid flux to the citric acid cycle increased while lactate flux was diminished in 7dMyc compared to Cont. Total protein levels of a panel of key metabolic enzymes were unchanged; however total protein O-GlcNAcylation was increased in 7dMyc. Substrate utilization changes for the citric acid cycle did not precede hypertrophy; therefore they are not the primary signal for cardiac growth in this model. Free fatty acid utilization and oxidation increase at established hypertrophy. Understanding the mechanisms whereby this change maintained compensated function could provide useful information for developing metabolic therapies to treat heart failure. The molecular signaling for this metabolic change may occur through O-GlcNAcylation.
PMCID: PMC3524362  PMID: 22828478
Cardiac hypertrophy; compensated hypertrophy; substrate metabolism; fatty acid oxidation
2.  Extracorporeal membrane oxygenation promotes long chain fatty acid oxidation in the immature swine heart in vivo 
Extracorporeal membrane oxygenation (ECMO) supports infants and children with severe cardiopulmonary compromise. Nutritional support for these children includes provision of medium- and long-chain fatty acids (FAs). However, ECMO induces a stress response, which could limit the capacity for FA oxidation. Metabolic impairment could induce new or exacerbate existing myocardial dysfunction. Using a clinically relevant piglet model, we tested the hypothesis that ECMO maintains the myocardial capacity for FA oxidation and preserves myocardial energy state. Provision of 13-Carbon labeled medium-chain FA (octanoate), long-chain free FAs (LCFAs), and lactate into systemic circulation showed that ECMO promoted relative increases in myocardial LCFA oxidation while inhibiting lactate oxidation. Loading of these labeled substrates at high dose into the left coronary artery demonstrated metabolic flexibility as the heart preferentially oxidized octanoate. ECMO preserved this octanoate metabolic response, but also promoted LCFA oxidation and inhibited lactate utilization. Rapid upregulation of pyruvate dehydrogenase kinase-4 (PDK4) protein appeared to participate in this metabolic shift during ECMO. ECMO also increased relative flux from lactate to alanine further supporting the role for pyruvate dehydrogenase inhibition by PDK4. High dose substrate loading during ECMO also elevated the myocardial energy state indexed by phosphocreatine to ATP ratio. ECMO promotes LCFA oxidation in immature hearts, while maintaining myocardial energy state. These data support the appropriateness of FA provision during ECMO support for the immature heart.
PMCID: PMC3739709  PMID: 23727393
Extracorporeal membrane oxygenation; immature heart; fatty acid oxidation; Nuclear magnetic resonance; substrate metabolism
3.  Myocardial Reloading After Extracorporeal Membrane Oxygenation Alters Substrate Metabolism While Promoting Protein Synthesis 
Extracorporeal membrane oxygenation (ECMO) unloads the heart, providing a bridge to recovery in children after myocardial stunning. ECMO also induces stress which can adversely affect the ability to reload or wean the heart from the circuit. Metabolic impairments induced by altered loading and/or stress conditions may impact weaning. However, cardiac substrate and amino acid requirements upon weaning are unknown. We assessed the hypothesis that ventricular reloading with ECMO modulates both substrate entry into the citric acid cycle (CAC) and myocardial protein synthesis.
Methods and Results
Sixteen immature piglets (7.8 to 15.6 kg) were separated into 2 groups based on ventricular loading status: 8‐hour ECMO (UNLOAD) and postwean from ECMO (RELOAD). We infused into the coronary artery [2‐13C]‐pyruvate as an oxidative substrate and [13C6]‐L‐leucine as an indicator for amino acid oxidation and protein synthesis. Upon RELOAD, each functional parameter, which were decreased substantially by ECMO, recovered to near‐baseline level with the exclusion of minimum dP/dt. Accordingly, myocardial oxygen consumption was also increased, indicating that overall mitochondrial metabolism was reestablished. At the metabolic level, when compared to UNLOAD, RELOAD altered the contribution of various substrates/pathways to tissue pyruvate formation, favoring exogenous pyruvate versus glycolysis, and acetyl‐CoA formation, shifting away from pyruvate decarboxylation to endogenous substrate, presumably fatty acids. Furthermore, there was also a significant increase of tissue concentrations for all CAC intermediates (≈80%), suggesting enhanced anaplerosis, and of fractional protein synthesis rates (>70%).
RELOAD alters both cytosolic and mitochondrial energy substrate metabolism, while favoring leucine incorporation into protein synthesis rather than oxidation in the CAC. Improved understanding of factors governing these metabolic perturbations may serve as a basis for interventions and thereby improve success rate from weaning from ECMO.
PMCID: PMC3828804  PMID: 23959443
amino acids; congenital heart disease; extracorporeal circulation; metabolism; pediatrics
4.  Thyroid Hormone Reverses Aging-Induced Myocardial Fatty Acid Oxidation Defects and Improves the Response to Acutely Increased Afterload 
PLoS ONE  2013;8(6):e65532.
Subclinical hypothyroidism occurs during aging in humans and mice and may contribute to the development of heart failure. Aging also impairs myocardial fatty acid oxidation, causing increased reliance on flux through pyruvate dehydrogenase (PDH) to maintain function. We hypothesize that the metabolic changes in aged hearts make them less tolerant to acutely increased work and that thyroid hormone supplementation reverses these defects.
Studies were performed on young (Young, 4–6 months) and aged (Old, 22–24 months) C57/BL6 mice at standard (50 mmHg) and high afterload (80 mmHg). Another aged group received thyroid hormone for 3 weeks (Old-TH, high afterload only). Function was measured in isolated working hearts along with substrate fractional contributions (Fc) to the citric acid cycle (CAC) using perfusate with 13C labeled lactate, pyruvate, glucose and unlabeled palmitate and insulin.
Old mice maintained cardiac function under standard workload conditions, despite a marked decrease in unlabeled (presumably palmitate) Fc and relatively similar individual carbohydrate contributions. However, old mice exhibited reduced palmitate oxidation with diastolic dysfunction exemplified by lower -dP/dT. Thyroid hormone abrogated the functional and substrate flux abnormalities in aged mice.
The aged heart shows diminished ability to increase cardiac work due to substrate limitations, primarily impaired fatty acid oxidation. The heart accommodates slightly by increasing efficiency through oxidation of carbohydrate substrates. Thyroid hormone supplementation in aged mice significantly improves cardiac function potentially through restoration of fatty acid oxidation.
PMCID: PMC3676337  PMID: 23762386
5.  Functional FcγRIIB Gene Variants Influence Intravenous Immunoglobulin (IVIG) Response in Kawasaki Disease (KD) Patients 
Capsule Summary
In Kawasaki Disease patients, the authors show associations between high-dose intravenous immunoglobulin (IVIG) response and a polymorphism in the FCγRIIB. This provides basis for defining the IVIG regulatory mechanisms and pharmacogenomic approach to IVIG therapy.
PMCID: PMC3444515  PMID: 21601260
Kawasaki disease; IVIG treatment response; FcγR
6.  A Prospective Open-Label Trial of Etanercept as Adjunctive Therapy for Kawasaki Disease 
The Journal of pediatrics  2010;157(6):960-966.e1.
To determine the safety and pharmacokinetics of etanercept (etanercept, Amgen inc. Thousands Oak, CA) a tumor necrosis factor-α (TNF-α) receptor blocker, in children with acute Kawasaki disease (KD). Standard therapy of acute KD includes IVIG and high dose aspirin, but a substantial number of patients are refractory and require additional treatment. TNF-α is elevated in children with KD suggesting a role for etanercept in treatment.
Study design
We performed a prospective open label trial of etanercept in patients with KD (6 months to 5 years, n = 17) meeting clinical criteria and with fever ≤ 10 days. All received IVIG and ASA. They received etanercept immediately after IVIG infusion and then weekly times two. For initial safety evaluation, the first five patients received 0.4 mg/kg/dose. Subsequent subjects received 0.8 mg/kg/dose.
Fifteen patients completed the study. Pharmacokinetics were similar to older children in published series. No serious adverse events related to etanercept occurred. No patient demonstrated prolonged or recrudescent fever requiring retreatment with IVIG. No patient showed an increase in coronary artery diameter, new coronary artery dilation /cardiac dysfunction.
Etanercept appears to be safe and well tolerated in children with KD. The data support performance of a placebo-controlled trial.
PMCID: PMC2970727  PMID: 20667551
Kawasaki’s disease; IVIG; TNF-α antagonist; Etanercept; Coronary artery aneurysm
7.  Triiodothyronine Supplementation in Infants and Children Undergoing Cardiopulmonary Bypass (TRICC) A Multicenter Placebo-Controlled Randomized Trial: Age Analysis 
Circulation  2010;122(11 Suppl):S224-S233.
Triiodothyronine levels decrease in infants and children after cardiopulmonary bypass. We tested the primary hypothesis that triiodothyronine (T3) repletion is safe in this population and produces improvements in postoperative clinical outcome.
Methods and Results
The TRICC study was a prospective, multicenter, double-blind, randomized, placebo-controlled trial in children younger than 2 years old undergoing heart surgery with cardiopulmonary bypass. Enrollment was stratified by surgical diagnosis. Time to extubation (TTE) was the primary outcome. Patients received intravenous T3 as Triostat (n=98) or placebo (n=95), and data were analyzed using Cox proportional hazards. Overall, TTE was similar between groups. There were no differences in adverse event rates, including arrhythmia. Prespecified analyses showed a significant interaction between age and treatment (P=0.0012). For patients younger than 5 months, the hazard ratio (chance of extubation) for Triostat was 1.72. (P=0.0216). Placebo median TTE was 98 hours with 95% confidence interval (CI) of 71 to 142 compared to Triostat TTE at 55 hours with CI of 44 to 92. TTE shortening corresponded to a reduction in inotropic agent use and improvement in cardiac function. For children 5 months of age, or older, Triostat produced a significant delay in median TTE: 16 hours (CI, 7–22) for placebo and 20 hours (CI, 16–45) for Triostat and (hazard ratio, 0.60; P=0.0220).
T3 supplementation is safe. Analyses using age stratification indicate that T3 supplementation provides clinical advantages in patients younger than 5 months and no benefit for those older than 5 months.
Clinical Trial Registration
URL: Unique identifier: NCT00027417.
PMCID: PMC3090076  PMID: 20837917
cardiopulmonary bypass; congenital heart surgery; thyroid hormone

Results 1-7 (7)