Cardiac contractility requires precise regulation. A recently discovered form of regulation of cardiac contractility involves a β-cardiac myosin off-state, the Interacting-Heads Motif (CarIHM). Despite its central role in cardiac physiology and disease, CarIHM structural dynamics remain poorly understood. Here, we integrate near-atomic resolution cryo-EM with all-atom molecular dynamics to characterize CarIHM in solution and in the context of the filament. We describe its conformational ensembles maintained by dynamic interfaces, and the stabilizing effect of the dilated cardiomyopathy mutation E525K, which limits S2 coiled-coil flexibility and impairs myosin activation. Intrinsically disordered regions of CarIHM and MyBP-C further modulate these dynamics. Our findings provide evidence for how CarIHM ensembles balance off/on states and anchor myosin heads in distinct thick filament environments. This integrated structural and dynamic approach enhances the understanding of thick filament regulation and facilitates predictions of the effects of genetic variants in inherited cardiomyopathies.

Isolated cardiac sarcoidosis (iCS), defined by granulomatous inflammation limited to the myocardium, represents the most diagnostically challenging and prognostically adverse form of sarcoidosis. As it is fundamentally a diagnosis of exclusion, iCS diagnosis relies on the absence of extracardiac sarcoid and the integration of multimodality imaging, endomyocardial biopsy, and molecular testing, each with inherent limitations. Cardiac magnetic resonance and positron emission tomography provide complementary assessment of inflammation, fibrosis, and ventricular function, enhancing diagnostic confidence. Electroanatomic mapping-guided biopsy may improve histologic yield, whereas genetic testing helps exclude phenocopies such as arrhythmogenic, hypertrophic, or dilated cardiomyopathies. Circulating biomarkers remain nonspecific but may complement imaging-based algorithms. Future research should focus on harmonized imaging protocols, non-FDG radiotracers, and molecular tissue profiling to refine activity assessment and guide therapy. Multimodal, probability-based frameworks represent the most promising approach for earlier, more accurate diagnosis and risk stratification in iCS.

The sodium-dependent multivitamin transporter, encoded by SLC5A6, mediates cellular uptake of biotin and pantothenic acid, essential cofactors for energy metabolism. We identified two families with SLC5A6 mutations presenting with early-onset dilated cardiomyopathy (DCM). To investigate the link between vitamin deficiency and cardiomyopathy, we generated a cardiac-specific SLC5A6 knockout (Slc5a6cKO) mouse model and evaluated the impact of vitamin supplementation. Slc5a6cKO mice developed progressive cardiac dysfunction, culminating in cardiac pathology and premature death at 26 weeks; earlier stages exhibited cardiomyocyte hypertrophy, fibrosis, impaired Coenzyme A synthesis, and metabolic imbalance, indicating progression toward cardiomyopathy. Cardiac magnetic resonance imaging and ECG confirmed progressive functional decline. Proteomic analysis revealed early mitochondrial metabolic disruption and extracellular matrix protein upregulation at 8 weeks, preceding overt cardiac dysfunction. Strikingly, vitamin supplementation from preconception onwards prevented the cardiac phenotype, preserving cardiac structure, function, morphology and survival. This paralleled the clinical outcome in one patient who received early vitamin treatment, compared to another who required a heart transplant without vitamin treatment. This study establishes a direct link between SLC5A6-mediated vitamin transport, mitochondrial function, and cardiac health. It highlights how vitamin deficiency contributes to cardiomyopathy pathogenesis and supports early vitamin supplementation as a potential therapeutic strategy for metabolic cardiomyopathies.

Duchenne muscular dystrophy (DMD) is a life-limiting disease characterized by progressive muscle wasting of skeletal and cardiac myocytes. Nowadays, heart failure is the principal cause of death. Current treatment is still unsatisfactory. Empagliflozin has shown excellent results in adults with heart failure, and is licensed for adolescents > 10 years of age with type 2 diabetes mellitus. In an effort to repurpose empagliflozin for DMD-associated cardiomyopathy, we aim to describe its pharmacokinetic behaviour in this population, assess ease-of-swallow, monitor safety, explore efficacy and screen efficacy markers.

Dilated cardiomyopathy (DCM) is a genetically heterogeneous disorder, characterized by ventricular dilatation and impaired systolic function, leading to heart failure and sudden cardiac death. Despite advances in genomic technologies, the genetic cause of DCM remains unidentified in more than half of the cases. Here, we performed an integrative analysis of genomic and transcriptomic data from patient-derived cardiac tissue to identify causative variants in genetically undiagnosed DCM. This approach enabled us to identify a homozygous splice-site variant (c.243+6T>A) in the sarcoglycan gene SGCB, which results in exon 2 skipping. This variant was significantly enriched in patients with DCM compared with the general population, with consistent genotype-phenotype correlations observed across multiple families. Protein-level analysis of cardiac tissue from homozygous individuals revealed loss of β-sarcoglycan, the protein product of SGCB, and destabilization of the sarcoglycan complex. Although SGCB has been previously associated with limb-girdle muscular dystrophy, these homozygous individuals showed no biochemical or clinical signs of skeletal muscle involvement, indicating an absence of myopathy. Compared with variant-negative patients with DCM, homozygous individuals also had a higher risk of early-onset adverse cardiac events. Together, these findings identify c.243+6T>A in SGCB as a cause of isolated DCM associated with unfavorable clinical outcomes.

Phospholamban (PLN) p.Arg14del (R14[Δ/+], also known as R14del) is a pathogenic variant that causes inherited cardiomyopathy. RNA therapy improves cardiac function and survival in murine PLN R14[Δ/+]. However, the molecular disease mechanisms and potential therapeutic effects of RNA therapy in the human setting remain poorly defined. Proteomic and phosphoproteomic profiling was performed on cardiac tissue from R14[Δ/+] patients (N = 6) and compared to other causes of dilated cardiomyopathy (DCM; N = 10). Findings were validated in CRISPR-Cas9-engineered R14[Δ/+] induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and isogenic controls. To assess reversibility, PLN-targeted RNA therapy using antisense oligonucleotides was applied to iPSC-CMs. Proteomics revealed enrichment of fibrotic pathways, while phosphoproteomics highlighted altered actomyosin structural organization uniquely distinguishing R14[Δ/+] from other DCM. This phosphoproteomic profile was recapitulated in R14[Δ/+] iPSC-CMs. RNA therapy concentration-dependently reduced PLN expression and modified the disease-specific phosphorylation profile. Twenty-eight phosphorylation sites were consistently altered across patient tissue and iPSC-CMs; twenty-two were reversed by RNA therapy and were enriched for cadherin- and actin-binding functions, implicating cytoskeletal remodeling. PLN/LC3 protein aggregates, a hallmark of PLN cardiomyopathy, were reduced after RNA therapy. Functionally, R14[Δ/+] cardiomyocytes exhibited accelerated calcium handling and contractile kinetics, which increased further upon RNA therapy. Human PLN R14[Δ/+] cardiomyopathy is characterized by a distinct phosphoproteomic signature involving cytoskeletal and contractile machinery. PLN-targeted RNA therapy reduced PLN expression, partially normalized these alterations, diminished protein aggregation, and enhanced calcium handling and contractile performance. These findings clarify the molecular mechanisms underlying R14[Δ/+] pathogenesis and support RNA therapy as a promising therapeutic strategy for PLN cardiomyopathy.

Background: Iron overload cardiomyopathy (IOC) is a major determinant of outcomes in hemochromatosis, and conventional echocardiography may miss early myocardial toxicity. Comparative data on primary (PH) versus secondary hemochromatosis (SH) using myocardial work (MW) indices are limited. Methods: We performed a retrospective cross-sectional study of 34 adults (16 PH and 18 SH patients) at a tertiary center. They all underwent echocardiography with speckle-tracking to obtain LV global longitudinal strain (GLS) and non-invasive MW indices from pressure-strain loops: global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE). Echocardiographic phenotypes were classified as a Normal, Dilated, Restrictive, or right ventricular/pulmonary hypertension (RVPH) phenotype. Results: SH patients showed higher iron burden and neurohormonal activation than PH patients (maximum ferritin 2954 vs. 444 ng/mL; BNP 93 vs. 13.5 pg/mL; both p < 0.001) and accounted for all deaths (33% vs. 0%) despite similar 3D LVEFs and GLSs. PH patients predominantly exhibited Normal phenotypes (81%), whereas SH patients more often showed advanced phenotypes, mainly RVPH and Dilated. GWI correlated inversely with ferritin (ρ ≈ -0.40), particularly ferritin at echocardiography in SH patients, while PH patients showed no significant correlations. GWW was higher in Dilated/RVPH compared to Normal phenotypes, and in SH patients, higher maximum ferritin was associated with impaired right ventricular free-wall strain. Conclusions: PH and SH patients exhibit distinct IOC phenotypes, with SH patients showing more advanced remodeling and worse outcomes. In this exploratory analysis, MW indices showed modest associations with iron burden markers, suggesting they may provide complementary information beyond LVEF and GLS. These preliminary findings require validation in larger, prospective studies.

Cardiovascular diseases (CVDs) are the leading cause of death globally, taking an estimated 17.9 million lives each year. Most heart cardiomyopathies result in an increased need for protein production that translates into an increased endoplasmic reticulum stress and therefore in the activation of the unfolded protein response pathway (UPR). The sustained activation of this pathway produces cell death and worsens the course of the disease. The role of lncRNAs in UPR signalling and their impact in several cardiomyopathies is beginning to be addressed.