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Background: The human heart primarily metabolizes fatty acids, and this decreases as alternative fuel use rises in heart failure with reduced ejection fraction (HFrEF). Patients with severe obesity and diabetes are thought to have increased myocardial fatty acid metabolism, but whether this is found in those who also have heart failure with preserved ejection fraction (HFpEF) is unknown. Methods: Plasma and endomyocardial biopsies were obtained from HFpEF (n=38), HFrEF (n=30), and nonfailing donor controls (n=20). Quantitative targeted metabolomics measured organic acids, amino acids, and acylcarnitines in myocardium (72 metabolites) and plasma (69 metabolites). The results were integrated with reported RNA sequencing data. Metabolomics were analyzed using agnostic clustering tools, Kruskal-Wallis test with Dunn test, and machine learning. Results: Agnostic clustering of myocardial but not plasma metabolites separated disease groups. Despite more obesity and diabetes in HFpEF versus HFrEF (body mass index, 39.8 kg/m 2 versus 26.1 kg/m 2 ; diabetes, 70% versus 30%; both P Conclusions: Despite marked obesity and diabetes, HFpEF myocardium exhibited lower fatty acid metabolites compared with HFrEF. Ketones and metabolites of the tricarboxylic acid cycle and BCAA were also lower in HFpEF, suggesting insufficient use of alternative fuels. These differences were not detectable in plasma and challenge conventional views of myocardial fuel use in HFpEF with marked diabetes and obesity and suggest substantial fuel inflexibility in this syndrome.

BACKGROUND: Right ventricular (RV) contractile dysfunction commonly occurs and worsens outcomes in patients with heart failure with reduced ejection fraction and pulmonary hypertension (HFrEF-PH). However, such dysfunction often goes undetected by standard clinical RV indices, raising concerns that they may not reflect aspects of underlying myocyte dysfunction. We thus sought to characterize RV myocyte contractile depression in HFrEF-PH, identify those components reflected by clinical RV indices, and uncover underlying biophysical mechanisms. METHODS: Resting, calcium-, and load-dependent mechanics were prospectively studied in permeabilized RV cardiomyocytes isolated from explanted hearts from 23 patients with HFrEF-PH undergoing cardiac transplantation and 9 organ donor controls. RESULTS: Unsupervised machine learning using myocyte mechanical data with the highest variance yielded 2 HFrEF-PH subgroups that in turn mapped to patients with decompensated or compensated clinical RV function. This correspondence was driven by reduced calcium-activated isometric tension in decompensated clinical RV function, whereas surprisingly, many other major myocyte contractile measures including peak power and myocyte active stiffness were similarly depressed in both groups. Similar results were obtained when subgroups were first defined by clinical indices, and then myocyte mechanical properties in each group compared. To test the role of thick filament defects, myofibrillar structure was assessed by x-ray diffraction of muscle fibers. This revealed more myosin heads associated with the thick filament backbone in decompensated clinical RV function, but not compensated clinical RV function, as compared with controls. This corresponded to reduced myosin ATP turnover in decompensated clinical RV function myocytes, indicating less myosin in a crossbridge-ready disordered-relaxed (DRX) state. Altering DRX proportion (%DRX) affected peak calcium-activated tension in the patient groups differently, depending on their basal %DRX, highlighting potential roles for precision-guided therapeutics. Last, increasing myocyte preload (sarcomere length) increased %DRX 1.5-fold in controls but only 1.2-fold in both HFrEF-PH groups, revealing a novel mechanism for reduced myocyte active stiffness and by extension Frank-Starling reserve in human heart failure. CONCLUSIONS: Although there are many RV myocyte contractile deficits in HFrEF-PH, commonly used clinical indices only detect reduced isometric calcium-stimulated force, which is related to deficits in basal and recruitable %DRX myosin. Our results support use of therapies to increase %DRX and enhance length-dependent recruitment of DRX myosin heads in such patients.

Retrotransposon families in the rodent family Cricetidae have been understudied in contrast to Muridae, both taxa classified within the superfamily Muroidea. Therefore, we pursued advancing our knowledge of the unique mys-1 LTR-retroelement identified in Peromyscus leucopus by utilizing intra-ORF PCR, quantitative dot bots, DNA and protein library screens, the generation of molecular phylogenies, and analyses of orthologous LTR-retroelement loci. This led to the discovery of three additional related families of LTR-retroelements. These include a 2900 bp full-length element of mys-related sequences (mysRS), an 8,000 bp element containing the mys ORF1 sequence (mORF1) with ERV-related sequences downstream in the reverse orientation, as well as an 1800 bp element primarily consisting of mys ORF2 (mORF2) related sequences flanked by LTRs. Our data revealed a very limited number of full-length mys elements among genera of the Neotominae subfamily of cricetid rodents. Additionally, although we estimated roughly 5,000–10,000 genomic copies of the mysRS element among Neotominae, most exist as partial copies. The mORF1 elements are also limited to the genomes of the Neotominae subfamily of cricetid rodents, whereas mORF2 appears limited to the Peromyscus genus. Molecular phylogenies demonstrating concerted evolution, along with an assessment of orthologous loci in Peromyscus for the presence or absence of elements, are consistent with recent activity of these novel LTR-retroelement families. Together with known activity of various families of non-LTR retroelements in Peromyscus species, we propose that retrotransposons have been continually contributing to the dynamics of Peromyscus genomes and are plausibly associated with the evolution of the over 50 identified species.

MTORC1 integrates signaling from the immune microenvironment to regulate T-cell activation, differentiation, and function. TSC2 in the tuberous sclerosis complex potently regulates mTORC1 activation. CD8+ T-cells lacking TSC2 have constitutively enhanced mTORC1 activity and generate potent effector T cells; however sustained mTORC1 activation prevents generation of long-lived memory CD8+ T-cells. Here we show manipulating TSC2 at Ser1365 potently regulates activated but not basal mTORC1 signaling in T cells. Unlike non-stimulated TSC2 knockout cells, CD8+ T-cells expressing mutant TSC2-S1365A (SA) have normal basal mTORC1 activity. PKC and T-cell Receptor (TCR) stimulation induces TSC2 S1365 phosphorylation and preventing this with the SA mutation markedly increases mTORC1 activation and T-cell effector function. Consequently, CD8+ SA T-cells display greater effector responses while retaining their capacity to become long-lived memory T-cells. CD8+ SA T-cells also display enhanced effector function under hypoxic and acidic conditions. In murine and human solid-tumor models, CD8+ SA T-cells used as adoptive cell therapy have greater anti-tumor immunity than WT CD8+ T-cells. These findings reveal an upstream mechanism to regulate mTORC1 activity in T-cells. The TSC2-SA mutation enhances both T-cell effector function and long-term persistence/memory formation, supporting a novel approach to engineer better CAR-T cells to treat cancer.

Phosphodiesterase 5 inhibition (PDE5i) activates cGMP-dependent protein kinase (PKG) and ameliorates heart failure; however, its impact on cardiac mitochondrial regulation has not been fully determined. Here, we investigated the role of the mitochondrial regulator peroxisome proliferator-activated receptor γ co-activator-1α (PGC1α) in the PDE5i-conferred cardioprotection, utilizing PGC1α null mice. In PGC1α(+/+) hearts exposed to 7 weeks of pressure overload by transverse aortic constriction, chronic treatment with the PDE5 inhibitor sildenafil improved cardiac function and remodeling, with improved mitochondrial respiration and upregulation of PGC1α mRNA in the myocardium. By contrast, PDE5i-elicited benefits were abrogated in PGC1α(−/−) hearts. In cultured cardiomyocytes, PKG overexpression induced PGC1α, while inhibition of the transcription factor CREB abrogated the PGC1α induction. Together, these results suggest that the PKG–PGC1α axis plays a pivotal role in the therapeutic efficacy of PDE5i in heart failure.

Rationale: cAMP activation of PKA (protein kinase A) stimulates excitation-contraction (EC) coupling, increasing cardiac contractility. This is clinically achieved by β-ARs (β-adrenergic receptor) stimulation or PDE3i (inhibition of phosphodiesterase type-3), although both approaches are limited by arrhythmia and chronic myocardial toxicity. PDE1i (Phosphodiesterase type-1 inhibition) also augments cAMP and enhances contractility in intact dogs and rabbits. Unlike β-ARs or PDE3i, PDE1i-stimulated inotropy is unaltered by β-AR blockade and induces little whole-cell Ca 2+ (intracellular Ca 2+ concentration; [Ca 2+ ] i ) increase. Positive inotropy from PDE1i was recently reported in human heart failure. However, mechanisms for this effect remain unknown. Objective: Define the mechanism(s) whereby PDE1i increases myocyte contractility. Methods and Results: We studied primary guinea pig myocytes that express the PDE1C isoform found in larger mammals and humans. In quiescent cells, the potent, selective PDE1i (ITI-214) did not alter cell shortening or [Ca 2+ ] i , whereas β-ARs or PDE3i increased both. When combined with low-dose adenylate cyclase stimulation, PDE1i enhanced shortening in a PKA-dependent manner but unlike PDE3i, induced little [Ca 2+ ] i rise nor augmented β-ARs. β-ARs or PDE3i reduced myofilament Ca 2+ sensitivity and increased sarcoplasmic reticulum Ca 2+ content and phosphorylation of PKA-targeted serines on TnI (troponin I), MYBP-C (myosin binding protein C), and PLN (phospholamban). PDE1i did not significantly alter any of these. However, PDE1i increased Ca v 1.2 channel conductance similarly as PDE3i (both PKA dependent), without altering Na + -Ca 2+ exchanger current density. Cell shortening and [Ca 2+ ] i augmented by PDE1i were more sensitive to Ca v 1.2 blockade and to premature or irregular cell contractions and [Ca 2+ ] i transients compared to PDE3i. Conclusions: PDE1i enhances contractility by a PKA-dependent increase in Ca v 1.2 conductance with less total [Ca 2+ ] i increase, and no significant changes in sarcoplasmic reticulum [Ca 2+ ], myofilament Ca 2+ -sensitivity, or phosphorylation of critical EC-coupling proteins as observed with β-ARs and PDE3i. PDE1i could provide a novel positive inotropic therapy for heart failure without the toxicities of β-ARs and PDE3i.

Cyclic nucleotides cAMP and cGMP are important second messengers for the regulation of adaptive thermogenesis. Their levels are controlled not only by their synthesis, but also their degradation. Since pharmacological inhibitors of cGMP-specific phosphodiesterase 9 (PDE9) can increase cGMP-dependent protein kinase signaling and uncoupling protein 1 expression in adipocytes, we sought to elucidate the role of PDE9 on energy balance and glucose homeostasis in vivo. Mice with targeted disruption of the PDE9 gene, Pde9a, were fed nutrient-matched high-fat (HFD) or low-fat diets. Pde9a−/− mice were resistant to HFD-induced obesity, exhibiting a global increase in energy expenditure, while brown adipose tissue (AT) had increased respiratory capacity and elevated expression of Ucp1 and other thermogenic genes. Reduced adiposity of HFD-fed Pde9a−/− mice was associated with improvements in glucose handling and hepatic steatosis. Cold exposure or treatment with β-adrenergic receptor agonists markedly decreased Pde9a expression in brown AT and cultured brown adipocytes, while Pde9a−/− mice exhibited a greater increase in AT browning, together suggesting that the PDE9-cGMP pathway augments classical cold-induced β-adrenergic/cAMP AT browning and energy expenditure. These findings suggest PDE9 is a previously unrecognized regulator of energy metabolism and that its inhibition may be a valuable avenue to explore for combating metabolic disease.

Right ventricular function has prognostic significance in patients with pulmonary hypertension. We evaluated whether cardiac magnetic resonance-derived strain and strain rate parameters could reliably reflect right ventricular systolic and diastolic function in precapillary pulmonary hypertension. End-systolic elastance and the time constant of right ventricular relaxation tau, both derived from invasive high-fidelity micromanometer catheter measurements, were used as gold standards for assessing systolic and diastolic right ventricular function, respectively. Nineteen consecutive precapillary pulmonary hypertension patients underwent cardiac magnetic resonance and right heart catheterization prospectively. Cardiac magnetic resonance data were compared with those of 19 control subjects. In pulmonary hypertension patients, associations between strain- and strain rate-related parameters and invasive hemodynamic parameters were evaluated. Longitudinal peak systolic strain, strain rate, and early diastolic strain rate were lower in PAH patients than in controls; peak atrial-diastolic strain rate was higher in pulmonary hypertension patients. Similarly, circumferential peak systolic strain rate was lower and peak atrial-diastolic strain rate was higher in pulmonary hypertension. In pulmonary hypertension, no correlations existed between cardiac magnetic resonance-derived and hemodynamically derived measures of systolic right ventricular function. Regarding diastolic parameters, tau was significantly correlated with peak longitudinal atrial-diastolic strain rate ( r = −0.61), deceleration time ( r = 0.75), longitudinal systolic to diastolic time ratio ( r = 0.59), early diastolic strain rate ( r = −0.5), circumferential peak atrial-diastolic strain rate ( r = −0.52), and deceleration time ( r = 0.62). Strain analysis of the right ventricular diastolic phase is a reliable non-invasive method for detecting right ventricular diastolic dysfunction in PAH.

Duchenne muscular dystrophy (DMD) is caused by the loss of the dystrophin protein, resulting in progressive muscle wasting, loss of ambulation, and early mortality in the second and third decades of life. While the skeletal muscle phenotype is most prominently associated with DMD, heart failure is the leading cause of death in DMD patients, and therapies remain limited. Advancements in stem cell-derived models and assays for heart disease have exciting translational potential for DMD, such as patient-specific modeling and drug screening. Contracting 2-D monolayers and organoids are standards of cardiac engineering, but measuring contraction is challenging due in part due to multi-axial alignment of immature sarcomeres. Complicated solutions to measure contraction in stem cell models use fluorescent beads to infer contraction, transgenic systems that express fluorescent proteins, 3-D scaffolding, and/or custom hardware and software. Here, we utilize a common microscope system used for measuring mature cardiomyocyte (IonOptix) and a commercially-available module (CytoMotion) that measures changes in pixel intensity to index contraction. This platform allows simultaneous measurement of contraction motion and calcium transients just like with adult mammalian cardiomyocytes. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) from a Duchenne muscular dystrophy (DMD) patient and a healthy relative, we demonstrate DMD hiPSC-CM exhibit impaired contraction and calcium handling. We have since further increased the output of our assay using a custom 24-well stimulation plate, and current studies are using this workflow to validate experimental therapies that show promise from mouse models of DMD.

Phosphodiesterases (PDEs) regulate cyclic nucleotide-mediated cell signaling and offer a therapeutic means to leverage cardiac function. FDA-approved PDE3 inhibitors increase myocyte contractility by enhancing L-type calcium channel activity and sarcoplasmic reticulum (SR) calcium (Ca 2+ ) load, but cause fatal arrhythmias in patients with heart failure. The PDE1 inhibitor ITI-214 is a novel inotrope that increases cardiac contractility in animal models and human patients with heart failure. Mechanistically, PDE1 inhibition leads to activation of the L-type Ca 2+ channel without altering the SR Ca 2+ load or myofilament-Ca 2+ sensitivity. The net result is enhanced myocyte contractility with comparatively less Ca 2+ increase and arrhythmias. PDE inhibition increases cAMP levels to activate protein kinase A (PKA), a pathway that regulates Ca 2+ handling and cycling. These results led us to hypothesize that PDEs 1 and 3 differ in localized domains where each controls cAMP-mediated signaling. Live-cell imaging experiments were performed in acutely isolated guinea pig myocytes expressing Förster resonance energy transfer (FRET) sensors to monitor changes in cAMP levels. These sensors were targeted to specific sarcolemmal domains or more generally to the cytosol. Our results showed that PDE1 inhibition is the predominant regulator of cAMP at the non T-tubular sarcolemmal membrane compared to other cAMP-hydrolyzing PDEs (PDE3 and 4). In contrast to PDE1, PDEs 3 and 4 were more indiscriminate and modulated cAMP in the cytosolic as well as in membrane domains. Upon beta-adrenergic stimulation, however, PDE4 but not PDEs 1 or 3 became the predominant cAMP modulator at the T-tubular membrane domain. These results provide evidence that PDE1 is a major regulator of sarcolemmal membrane cAMP, suggesting that PDE1 inhibitory effects upon the L-type Ca 2+ channel is localized to this domain. In future studies, we will examine if PDE1 inhibition selectively activates PKA in this region, and seek to identify the interacting proteins that support PDE1 modulation of sarcolemmal cAMP/PKA signaling. Resolving this cell signaling difference would provide mechanistic insight into a novel inotrope that has already completed a Phase II clinical evaluation in patients.

Transient receptor potential canonical type 6 (TRPC6) is a non-voltage gated cation channel that principally conducts calcium to regulate signaling in cardiac, vascular, neuronal and other cells. Abnormally increased TRPC6 expression/conductance and genetic gain of function mutations contribute to fibrosis, hypertrophy, proteinuria, and edema, notably linked to its stimulation of nuclear factor of activated T-cells (NFAT) signaling. Hyperglycemia (HG) also activates TRPC6/NFAT as a cause of diabetic renal disease. While prior work linked HG-TRPC6 activation to oxidant stress, the role of another major HG modification - O-GlcNAcylation, is unknown. Here we show TRPC6 is constitutively O-GlcNAcylated, TRPC6 and O-GlcNAc transferase proteins interact, this modification potently suppresses basal channel conductance and NFAT activity, and it is unaltered by HG. Proteomics identifies O-GlcNAcylation at Ser14, Thr70, and Thr221 in the N-terminus ankyrin-4 (AR4) and neighboring linker (LH1) domains of TRPC6. Of these, T221 is most impactful as a T221A mutation increases basal NFAT activity 11-fold, TRPC6 conductance 75-80% vs wild-type, and when expressed in cardiomyocytes amplifies NFAT-pro-hypertrophic gene expression. T221 is highly conserved and mutating homologs in TRPC3 and TRPC7 also markedly elevates basal NFAT activity. Molecular models predict electrostatic interactions between T221 O-GlcNAc and Ser199, Glu200, and Glu246, and we find similarly elevated NFAT activity from alanine substitutions at these coordinating sites as well. Thus, O-GlcNAcylation at T221 and its interaction with coordinating residues in AR4-LH1 is required for basal TRPC6 channel conductance and regulation of NFAT.

The InSight mission landed on the surface of Mars on 26 November 2018. The InSight system performance met all design requirements, although several performance metrics fell near the boundaries of t...

PURPOSE: Right ventricular (RV) capacity to adapt to increased afterload is the main determinant of outcome in pulmonary hypertension (PH), a common morbidity seen in systemic sclerosis (SSc). We hypothesized that supine bicycle echocardiography (SBE), coupled with RV longitudinal systolic strain (RVLSS), improves detection of limitations in RV reserve in SSc. METHODS: 56 SSc patients were prospectively studied during SBE with RV functional parameters compared at rest and peak stress. We further dichotomized patients based on resting RV systolic pressure (RVSP) to determine the effects of load on contractile response. RESULTS: Our pooled cohort analysis revealed reduced global RVLSS at rest (−16.2 ± 3.9%) with normal basal contractility (−25.6 ± 7.7%) and relative hypokinesis of the midventricular (−14.1 ± 6.0%) and apical (−8.9 ± 5.1%) segments. With exercise, global RVLSS increased significantly (p=0.0005), however despite normal basal contractility at rest, there was no further augmentation with exercise. Mid and apical RVLSS increased with exercise suggestive of RV contractile reserve. In patients with resting RVSP < 35 mmHg, global and segmental RVLSS increased with exercise. In patients with resting RVSP ≥35 mmHg, global and segmental RVLSS did not increase with exercise and there was evidence of exertional RV dilation. CONCLUSION: Exercise provocation in conjunction with RVLSS identified differential regional contractile response to exercise in SSc patients. We further demonstrate the effect of increased loading conditions on RV contractile response exercise. These findings suggest subclinical impairments in RV reserve in SSc that may be missed by resting noninvasive 2DE-based assessments alone.

Rationale: The mTORC1 (mechanistic target of rapamycin complex-1) controls metabolism and protein homeostasis and is activated following ischemia reperfusion (IR) injury and by ischemic preconditioning (IPC). However, studies vary as to whether this activation is beneficial or detrimental, and its influence on metabolism after IR is little reported. A limitation of prior investigations is their use of broad gain/loss of mTORC1 function, mostly applied before ischemic stress. This can be circumvented by regulating one serine (S1365) on TSC2 (tuberous sclerosis complex) to achieve bidirectional mTORC1 modulation but only with TCS2-regulated costimulation. Objective: We tested the hypothesis that reduced TSC2 S1365 phosphorylation protects the myocardium against IR and is required for IPC by amplifying mTORC1 activity to favor glycolytic metabolism. Methods and Results: Mice with either S1365A (TSC2 SA ; phospho-null) or S1365E (TSC2 SE ; phosphomimetic) knockin mutations were studied ex vivo and in vivo. In response to IR, hearts from TSC2 SA mice had amplified mTORC1 activation and improved heart function compared with wild-type and TSC2 SE hearts. The magnitude of protection matched IPC. IPC requited less S1365 phosphorylation, as TSC2 SE hearts gained no benefit and failed to activate mTORC1 with IPC. IR metabolism was altered in TSC2 SA , with increased mitochondrial oxygen consumption rate and glycolytic capacity (stressed/maximal extracellular acidification) after myocyte hypoxia-reperfusion. In whole heart, lactate increased and long-chain acylcarnitine levels declined during ischemia. The relative IR protection in TSC2 SA was lost by lowering glucose in the perfusate by 36%. Adding fatty acid (palmitate) compensated for reduced glucose in wild type and TSC2 SE but not TSC2 SA which had the worst post-IR function under these conditions. Conclusions: TSC2-S1365 phosphorylation status regulates myocardial substrate utilization, and its decline activates mTORC1 biasing metabolism away from fatty acid oxidation to glycolysis to confer protection against IR. This pathway is also engaged and reduced TSC2 S1365 phosphorylation required for effective IPC. Graphic Abstract: A graphic abstract is available for this article.

Cardiomyocytes undergo significant structural and functional changes after birth, and these fundamental processes are essential for the heart to pump blood to the growing body. However, due to the challenges of isolating single postnatal/adult myocytes, how individual newborn cardiomyocytes acquire multiple aspects of the mature phenotype remains poorly understood. Here we implement large-particle sorting and analyze single myocytes from neonatal to adult hearts. Early myocytes exhibit wide-ranging transcriptomic and size heterogeneity that is maintained until adulthood with a continuous transcriptomic shift. Gene regulatory network analysis followed by mosaic gene deletion reveals that peroxisome proliferator-activated receptor coactivator-1 signaling, which is active in vivo but inactive in pluripotent stem cell-derived cardiomyocytes, mediates the shift. This signaling simultaneously regulates key aspects of cardiomyocyte maturation through previously unrecognized proteins, including YAP1 and SF3B2. Our study provides a single-cell roadmap of heterogeneous transitions coupled to cellular features and identifies a multifaceted regulator controlling cardiomyocyte maturation., Cardiomyocyte maturation and the acquisition of phenotypes is poorly understood at the single cell level. Here, the authors analyse the transcriptome of single cells from neonatal to adult heart and reveal that peroxisome proliferator-activated receptor coactivator-1 mediates the phenotypic shift.

Purpose Pacing to increase resting heart rate (HR) is commonly employed in order to improve hemodynamics and cardiac output (CO), particularly in post-operative setting when right ventricle (RV) dysfunction is present. We tested if right atrial (RA) pacing improves RV hemodynamics acutely, and if the degree of baseline RV dysfunction modifies this relationship. Methods We prospectively enrolled adult subjects with known or suspected pulmonary arterial hypertension (PAH) who underwent elective right heart catheterization between January 2013 and April 2016. RV pressure-volume (PV) analysis was performed with conductance catheters. RV volumes were calibrated by cardiac MRI same day. After measuring baseline PV data, a bipolar pacing wire was positioned in the RA and rate set to 80 to 90 beats per minute (bpm). Rate was increased in steps of 20 bpm. PV loops were recorded at end-expiration after 1 minute in each group: 80-99, 100-119, and 120-139 bpm. Parametric data were analyzed by Repeated Measures ANOVA, and non-parametric data were analyzed by Friedman Test. Baseline hemodynamic predictors of CO were analyzed by Repeated Measures simple linear regression. Results Twenty-three subjects were included in this analysis. Baseline mean RA pressure was 7 ± 3 mmHg with pulmonary vascular resistance of 5.2 ± 4.1 wood units. As HR increased with RA pacing, stroke volume (SV) declined in each pacing group (68±22, 61±19, 54±21 mL, respectively; p Conclusion As heart rate increases with RA pacing, RV contractility and CO increase modestly at the expense of cardiac efficiency.