Myocardial leptin transcription in feline hypertrophic cardiomyopathy

Genetic Basis of Hypertrophic Cardiomyopathy in Cats

Hypertrophic cardiomyopathy (HCM) is a common cardiovascular condition in cats, affecting yth males and females of all ages. Some breeds, such as Ragdolls and Maine Coons, can develop HCM at a young age. The disease has a wide range of progression and severity, characterized by various pathological changes in the heart, including arteritis, fibrous tissue deposition, and myocardial cell hypertrophy. Left ventricular hypertrophy, which can restrict blood flow, is a common feature of HCM. The disease may persist into old age and eventually lead to heart failure and increased diastolic pressure. The basis of HCM in cats is thought to be genetic, although the exact mechanisms are not fully understood. Mutations in sarcomeric proteins, in particular myosin-binding protein C (MYBPC3), have been identified in cats with HCM. Two specific mutations, MYBPC3 [R818W] and MYBPC3 [A31P], have been classified as 'pathogenic'. Other variants in genes such as MYBPC3, TNNT2, ALMS1, and MYH7 are also associated with HCM. However, there are cases where cats without known genetic mutations still develop HCM, suggesting the presence of unknown genetic factors contributing to the disease. This work aims to summarise the new knowledge of HCM in cats and the alterations in cardiac tissue as a result of genetic variants.

Cardio-oncology: Shared Genetic, Metabolic, and Pharmacologic Mechanism

PURPOSE OF REVIEW

The article aims to investigate the complex relationship between cancer and cardiovascular disease (CVD), with a focus on the effects of cancer treatment on cardiac health.

RECENT FINDINGS

Advances in cancer treatment have improved long-term survival rates, but CVD has emerged as a leading cause of morbidity and mortality in cancer patients. The interplay between cancer itself, treatment methods, homeostatic changes, and lifestyle modifications contributes to this comorbidity. Recent research in the field of cardio-oncology has revealed common genetic mutations, risk factors, and metabolic features associated with the co-occurrence of cancer and CVD. This article provides a comprehensive review of the latest research in cardio-oncology, including common genetic mutations, risk factors, and metabolic features, and explores the interactions between cancer treatment and CVD drugs, proposing novel approaches for the management of cancer and CVD.

Feline myocardial transcriptome in health and in hypertrophic cardiomyopathy-A translational animal model for human disease

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, characterized by primary left ventricular hypertrophy. Feline HCM closely resembles human HCM and is suggested as translational animal model for the human disease. A genetic cause is established in humans and suspected for cats, but little is known about the gene expression and pathways involved in the pathogenesis of HCM. To investigate the myocardial transcriptome changes in HCM, RNA sequencing was conducted on left ventricle (LV) and left atrium (LA) samples of healthy cats and cats with HCM (each n = 5; 20 samples). Ingenuity Pathway Analysis was used to determine functional pathways, regulators, and networks. Distinct gene expression profiles were identified in the LV and LA of the feline healthy and HCM myocardium. Analysis of differentially expressed mRNAs (>2 fold; FDR < 0.01) found chamber-specific (LV vs. LA) expression in both healthy and HCM groups, with higher transcriptional activity in the LA. Genes that contribute to the distinct structure and function of each chamber in health and HCM were identified in the regional comparison. The gene expression profiles of HCM compared to healthy hearts revealed disease related genes, including THBS4 and KLHL33 (LV), FAM177B and THRSP (LA), the latter 3 have not been reported for the myocardium so far, as the top differently expressed genes in the HCM heart. Differently expressed genes and functional pathways found in the HCM heart are associated with cardiac remodeling and fibrosis, inflammation, microvascular changes, calcium signaling and cardiac metabolism, with some regional differences. RhoGDI-RhoGTPase signaling, integrin and ILK signaling pathways, the LXR/RXR pathway in the LA, and the PPARα/RXRα, HIF1α and CXCR4 pathways in the LV might be of particular importance in the HCM disease process. This study identified region-specific myocardial gene transcription patterns as well as novel genes and pathways associated with HCM.

The Acute Effects of Leptin on the Contractility of Isolated Rat Atrial and Ventricular Cardiomyocytes

Leptin is a pleiotropic peptide playing an important role in the regulation of cardiac functions. It is not clear whether leptin directly modulates the mechanical function of atrial cardiomyocytes. We compared the acute effects of leptin on the characteristics of mechanically non-loaded sarcomere shortening and cytosolic Ca2+ concentration ([Ca2+]i) transients in single rat atrial and ventricular cardiomyocytes. We also studied the functional properties of myosin obtained from cardiomyocytes using an in vitro motility assay and assessed the sarcomeric protein phosphorylation. Single cardiomyocytes were exposed to 5, 20, and 60 nM leptin for 60 min. In ventricular cardiomyocytes, 60 nM leptin depressed sarcomere shortening amplitude and decreased the rates of shortening and relaxation. These effects were accompanied by a decrease in the phosphorylation of cMyBP-C, an increase in Tpm phosphorylation, and a slowdown of the sliding velocity of thin filaments over myosin in the in vitro motility assay. In contrast, in atrial cardiomyocytes, the phosphorylation of cMyBP-C and TnI increased, and the characteristics of sarcomere shortening did not change. Leptin had no effect on the characteristics of [Ca2+]i transients in ventricular cardiomyocytes, while 5 nM leptin prolonged [Ca2+]i transients in atrial cardiomyocytes. Thus, leptin-induced changes in contractility of ventricular cardiomyocytes may be attributed to the direct effects of leptin on cross-bridge kinetics and sarcomeric protein properties rather than changes in [Ca2+]i. We also suggest that the observed differences between atrial and ventricular cardiomyocytes may be associated with the peculiarities of the expression of leptin receptors, as well as signaling pathways in the atrial and ventricular myocardium.

Lipid Droplet-Associated Proteins in Cardiomyopathy

BACKGROUND

The heart requires a high rate of fatty-acid oxidation (FAO) to meet its energy needs. Neutral lipids are the main source of energy for the heart and are stored in lipid droplets (LDs), which are cytosolic organelles that primarily serve to store neutral lipids and regulate cellular lipid metabolism. LD-associated proteins (LDAPs) are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism. Therefore, abnormal cardiac lipid accumulation or FAO can alter the redox state of the heart, resulting in cardiomyopathy, a group of diseases that negatively affect the myocardial function, thereby leading to heart failure and even cardiac death.

SUMMARY

LDs, along with LDAPs, are pivotal for modulating heart lipid homeostasis. The proper cardiac development and the maintenance of its normal function depend largely on lipid homeostasis regulated by LDs and LDAPs. Overexpression or deletion of specific LDAPs can trigger myocardial dysfunction and may contribute to the development of cardiomyopathy. Extensive connections and interactions may also exist between LDAPs. Key Message: In this review, the various mechanisms involved in LDAP-mediated regulation of lipid metabolism, the association between cardiac development and lipid metabolism, as well as the role of LDAPs in cardiomyopathy progression are discussed.

Novel biomarkers in cats with congestive heart failure due to primary cardiomyopathy

The pathogenesis of feline cardiomyopathy and congestive heart failure (CHF) requires further understanding. In this study, we assessed serum proteome change in feline CHF, aiming to identify novel biomarker for both research and clinical use. The study comprised 15 cats in CHF, 5 cats in preclinical cardiomyopathy and 15 cats as healthy controls. Serum proteome profiles were obtained by tandem mass tag labelling followed by mass spectrometry. Protein concentrations in CHF cats were compared with healthy controls. Western blot was performed for proteomic validation. Correlations were assessed between the altered proteins in CHF and clinical variables in cats with cardiomyopathy to evaluate protein-cardiac association. Bioinformatic analysis was employed to identify pathophysiological pathways involved in feline CHF. Sixteen serum proteins were significantly different between CHF and healthy control cats (P < .05). These included serine protease inhibitors, apolipoproteins and other proteins associated with inflammation and coagulation. Clinical parameters from cats with cardiomyopathy significantly correlated with the altered proteins (P < .05). Bioinformatic analysis identified 13 most relevant functional profiles in feline CHF, which mostly associated with extracellular matrix organization and metabolism. Data are available via ProteomeXchange with identifier PXD017761. SIGNIFICANCE: Cardiomyopathies affect both cats and humans, and they can cause serious consequence such as congestive heart failure (CHF). To date, the pathophysiological mechanism of CHF is not fully understood. In this study, for the first time, we used a proteomic approach combined with bioinformatic analysis to evaluate serum protein change in cats with CHF. Results indicate systemic inflammation, coagulation protein changes, innate immunity and extracellular matrix remodeling are involved in feline CHF, which are largely comparable with findings in previous human studies. Our study provides new insights into CHF and cardiomyopathy in cats, and the identified novel biomarkers and pathophysiological pathways provide valuable information for future studies.