The Role of Cathepsin D in the Pathophysiology of Heart Failure and its Potentially Beneficial Properties:a translational approach

Aims: Cathepsin D is a ubiquitous lysosomal protease that is primarily secreted due to oxidative stress. The role of circulating cathepsin D in heart failure (HF) is unknown. The aim of this study is to determine the association between circulating cathepsin D levels and clinical outcomes in patients with HF and to investigate the biological settings that induce the release of cathepsin D in HF. Methods and results: Cathepsin D levels were studied in 2174 patients with HF from the BIOSTAT-CHF index study. Results were validated in 1700 HF patients from the BIOSTAT-CHF validation cohort. The primary combined outcome was all-cause mortality and/or HF hospitalizations. Human pluripotent stem cell-derived cardiomyocytes were subjected to hypoxic, pro-inflammatory signalling and stretch conditions. Additionally, cathepsin D expression was inhibited by targeted short hairpin RNAs (shRNA). Higher levels of cathepsin D were independently associated with diabetes mellitus, renal failure and higher levels of interleukin-6 and N-terminal pro-B-type natriuretic peptide (P < 0.001 for all). Cathepsin D levels were independently associated with the primary combined outcome [hazard ratio (HR) per standard deviation (SD): 1.12; 95% confidence interval (CI) 1.02–1.23], which was validated in an independent cohort (HR per SD: 1.23, 95% CI 1.09–1.40). In vitro experiments demonstrated that human stem cell-derived cardiomyocytes released cathepsin D and troponin T in response to mechanical stretch. ShRNA-mediated silencing of cathepsin D resulted in increased necrosis, abrogated autophagy, increased stress-induced metabolism, and increased release of troponin T from human stem cell-derived cardiomyocytes under stress. Conclusions: Circulating cathepsin D levels are associated with HF severity and poorer outcome, and reduced levels of cathepsin D may have detrimental effects with therapeutic potential in HF

Selenium and outcome in heart failure

Aims: Severe deficiency of the essential trace element selenium can cause myocardial dysfunction although the mechanism at cellular level is uncertain. Whether, in clinical practice, moderate selenium deficiency is associated with worse symptoms and outcome in patients with heart failure is unknown. Methods and results: BIOSTAT‐CHF is a multinational, prospective, observational cohort study that enrolled patients with worsening heart failure. Serum concentrations of selenium were measured by inductively coupled plasma mass spectrometry. Primary endpoint was a composite of all‐cause mortality and hospitalization for heart failure; secondary endpoint was all‐cause mortality. To investigate potential mechanisms by which selenium deficiency might affect prognosis, human cardiomyocytes were cultured in absence of selenium, and mitochondrial function and oxidative stress were assessed. Serum selenium concentration (deficiency) was &lt;70 μg/L in 485 (20.4%) patients, who were older, more often women, had worse New York Heart Association class, more severe signs and symptoms of heart failure and poorer exercise capacity (6‐min walking test) and quality of life (Kansas City Cardiomyopathy Questionnaire). Selenium deficiency was associated with higher rates of the primary endpoint [hazard ratio (HR) 1.23; 95% confidence interval (CI) 1.06–1.42] and all‐cause mortality (HR 1.52; 95% CI 1.26–1.86). In cultured human cardiomyocytes, selenium deprivation impaired mitochondrial function and oxidative phosphorylation, and increased intracellular reactive oxygen species levels. Conclusions: Selenium deficiency in heart failure patients is independently associated with impaired exercise tolerance and a 50% higher mortality rate, and impaired mitochondrial function in vitro, in human cardiomyocytes. Clinical trials are needed to investigate the effect of selenium supplements in patients with heart failure, especially if they have low plasma concentrations of selenium

Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole

Dynamic loading of human engineered heart tissue enhances contractile function and drives a desmosome-linked disease phenotype

The role that mechanical forces play in shaping the structure and function of the heart is critical to understanding heart formation and the etiology of disease but is challenging to study in patients. Engineered heart tissues (EHTs) incorporating human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes have the potential to provide insight into these adaptive and maladaptive changes. However, most EHT systems cannot model both preload (stretch during chamber filling) and afterload (pressure the heart must work against to eject blood). Here, we have developed a new dynamic EHT (dyn-EHT) model that enables us to tune preload and have unconstrained contractile shortening of >10%. To do this, three-dimensional (3D) EHTs were integrated with an elastic polydimethylsiloxane strip providing mechanical preload and afterload in addition to enabling contractile force measurements based on strip bending. Our results demonstrated that dynamic loading improves the function of wild-type EHTs on the basis of the magnitude of the applied force, leading to improved alignment, conduction velocity, and contractility. For disease modeling, we used hiPSC-derived cardiomyocytes from a patient with arrhythmogenic cardiomyopathy due to mutations in the desmoplakin gene. We demonstrated that manifestation of this desmosome-linked disease state required dyn-EHT conditioning and that it could not be induced using 2D or standard 3D EHT approaches. Thus, a dynamic loading strategy is necessary to provoke the disease phenotype of diastolic lengthening, reduction of desmosome counts, and reduced contractility, which are related to primary end points of clinical disease, such as chamber thinning and reduced cardiac output.Cardiolog

Heritability estimates for 361 blood metabolites across 40 genome-wide association studies

Metabolomics examines the small molecules involved in cellular metabolism. Approximately 50% of total phenotypic differences in metabolite levels is due to genetic variance, but heritability estimates differ across metabolite classes. We perform a review of all genome-wide association and (exome-) sequencing studies published between November 2008 and October 2018, and identify >800 class-specific metabolite loci associated with metabolite levels. In a twin-family cohort (N = 5117), these metabolite loci are leveraged to simultaneously estimate total heritability (h2 total), and the proportion of heritability captured by known metabolite loci (h2 Metabolite-hits) for 309 lipids and

The genetic epidemiology of joint shape and the development of osteoarthritis

Congruent, low-friction relative movement between the articulating elements of a synovial joint is an essential pre-requisite for sustained, efficient, function. Where disorders of joint formation or maintenance exist, mechanical overloading and osteoarthritis (OA) follow. The heritable component of OA accounts for ~ 50% of susceptible risk. Although almost 100 genetic risk loci for OA have now been identified, and the epidemiological relationship between joint development, joint shape and osteoarthritis is well established, we still have only a limited understanding of the contribution that genetic variation makes to joint shape and how this modulates OA risk. In this article, a brief overview of synovial joint development and its genetic regulation is followed by a review of current knowledge on the genetic epidemiology of established joint shape disorders and common shape variation. A summary of current genetic epidemiology of OA is also given, together with current evidence on the genetic overlap between shape variation and OA. Finally, the established genetic risk loci for both joint shape and osteoarthritis are discussed

Accelerating functional gene discovery in osteoarthritis

Osteoarthritis causes debilitating pain and disability, resulting in a considerable socioeconomic burden, yet no drugs are available that prevent disease onset or progression. Here, we develop, validate and use rapid-throughput imaging techniques to identify abnormal joint phenotypes in randomly selected mutant mice generated by the International Knockout Mouse Consortium. We identify 14 genes with functional involvement in osteoarthritis pathogenesis, including the homeobox gene Pitx1, and functionally characterize 6 candidate human osteoarthritis genes in mouse models. We demonstrate sensitivity of the methods by identifying age-related degenerative joint damage in wild-type mice. Finally, we phenotype previously generated mutant mice with an osteoarthritis-associated polymorphism in the Dio2 gene by CRISPR/Cas9 genome editing and demonstrate a protective role in disease onset with public health implications. We hope this expanding resource of mutant mice will accelerate functional gene discovery in osteoarthritis and offer drug discovery opportunities for this common, incapacitating chronic disease