Accumulation of cellular damage with advancing age leads to atherothrombosis and associated cardiovascular disease. Ageing is also characterized by shortening of the DNA component of telomeres, the ...specialized genetic segments located at the end of eukaryotic chromosomes that protect them from end-to-end fusions. By inducing genomic instability, replicative senescence and apoptosis, shortening of the telomeric DNA is thought to contribute to organismal ageing. In this Review, we discuss experimental and human studies that have linked telomeres and associated proteins to several factors which influence cardiovascular risk (eg, estrogens, oxidative stress, hypertension, diabetes, and psychological stress), as well as to neovascularization and the pathogenesis of atherosclerosis and heart disease. Two chief questions that remain unanswered are whether telomere shortening is cause or consequence of cardiovascular disease, and whether therapies targeting the telomere may find application in treating these disorders (eg, cell "telomerization" to engineer blood vessels of clinical value for bypass surgery, and to facilitate cell-based myocardial regeneration strategies). Given that most research to date has focused on the role of telomerase, it is also of up most importance to investigate whether alterations in additional telomere-associated proteins may contribute to the pathogenesis of cardiovascular disease.
Obesity is causally linked with the development of cardiovascular disorders. Accumulating evidence indicates that cardiovascular disease is the collateral damage of obesity-driven adipose tissue ...dysfunction that promotes a chronic inflammatory state within the organism. Adipose tissues secrete bioactive substances, referred to as adipokines, which largely function as modulators of inflammation. The microenvironment of adipose tissue will affect the adipokine secretome, having actions on remote tissues. Obesity typically leads to the upregulation of proinflammatory adipokines and the downregulation of anti-inflammatory adipokines, thereby contributing to the pathogenesis of cardiovascular diseases. In this review, we focus on the microenvironment of adipose tissue and how it influences cardiovascular disorders, including atherosclerosis and ischemic heart diseases, through the systemic actions of adipokines.
Recent studies have shown that hematopoietic stem cells can undergo clonal expansion secondary to somatic mutations in leukemia-related genes, thus leading to an age-dependent accumulation of mutant ...leukocytes in the blood. This somatic mutation-related clonal hematopoiesis is common in healthy older individuals, but it has been associated with an increased incidence of future cardiovascular disease. The epigenetic regulator TET2 is frequently mutated in blood cells of individuals exhibiting clonal hematopoiesis.
This study investigated whether Tet2 mutations within hematopoietic cells can contribute to heart failure in 2 models of cardiac injury.
Heart failure was induced in mice by pressure overload, achieved by transverse aortic constriction or chronic ischemia induced by the permanent ligation of the left anterior descending artery. Competitive bone marrow transplantation strategies with Tet2-deficient cells were used to mimic TET2 mutation-driven clonal hematopoiesis. Alternatively, Tet2 was specifically ablated in myeloid cells using Cre recombinase expressed from the LysM promoter.
In both experimental heart failure models, hematopoietic or myeloid Tet2 deficiency worsened cardiac remodeling and function, in parallel with increased interleukin-1beta (IL-1β) expression. Treatment with a selective NLRP3 inflammasome inhibitor protected against the development of heart failure and eliminated the differences in cardiac parameters between Tet2-deficient and wild-type mice.
Tet2 deficiency in hematopoietic cells is associated with greater cardiac dysfunction in murine models of heart failure as a result of elevated IL-1β signaling. These data suggest that individuals with TET2-mediated clonal hematopoiesis may be at greater risk of developing heart failure and respond better to IL-1β–NLRP3 inflammasome inhibition.
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Wnt signaling has diverse actions in cardiovascular development and disease processes. Secreted frizzled-related protein 5 (Sfrp5) has been shown to function as an extracellular inhibitor of ...non-canonical Wnt signaling that is expressed at relatively high levels in white adipose tissue. The aim of this study was to investigate the role of Sfrp5 in the heart under ischemic stress. Sfrp5 KO and WT mice were subjected to ischemia/reperfusion (I/R). Although Sfrp5-KO mice exhibited no detectable phenotype when compared with WT control at baseline, they displayed larger infarct sizes, enhanced cardiac myocyte apoptosis, and diminished cardiac function following I/R. The ischemic lesions of Sfrp5-KO mice had greater infiltration of Wnt5a-positive macrophages and greater inflammatory cytokine and chemokine gene expression when compared with WT mice. In bone marrow-derived macrophages, Wnt5a promoted JNK activation and increased inflammatory gene expression, whereas treatment with Sfrp5 blocked these effects. These results indicate that Sfrp5 functions to antagonize inflammatory responses after I/R in the heart, possibly through a mechanism involving non-canonical Wnt5a/JNK signaling.
Adipose tissue dysfunction plays a pivotal role in the development of insulin resistance in obese individuals. Cell culture studies and gain-of-function mouse models suggest that canonical Wnt ...proteins modulate adipose tissue expansion. However, no genetic evidence supports a role for endogenous Wnt proteins in adipose tissue dysfunction, and the role of noncanonical Wnt signaling remains largely unexplored. Here we provide evidence from human, mouse, and cell culture studies showing that Wnt5a-mediated, noncanonical Wnt signaling contributes to obesity-associated metabolic dysfunction by increasing adipose tissue inflammation. Wnt5a expression is significantly upregulated in human visceral fat compared with subcutaneous fat in obese individuals. In obese mice, Wnt5a ablation ameliorates insulin resistance, in parallel with reductions in adipose tissue inflammation. Conversely, Wnt5a overexpression in myeloid cells augments adipose tissue inflammation and leads to greater impairments in glucose homeostasis. Wnt5a ablation or overexpression did not affect fat mass or adipocyte size. Mechanistically, Wnt5a promotes the expression of proinflammatory cytokines by macrophages in a Jun NH2-terminal kinase-dependent manner, leading to defective insulin signaling in adipocytes. Exogenous interleukin-6 administration restores insulin resistance in obese Wnt5a-deficient mice, suggesting a central role for this cytokine in Wnt5a-mediated metabolic dysfunction. Taken together, these results demonstrate that noncanonical Wnt signaling contributes to obesity-induced insulin resistance independent of adipose tissue expansion.
Clonal hematopoiesis driven by somatic mutations in hematopoietic cells, frequently called clonal hematopoiesis of indeterminate potential (CHIP), has been associated with adverse cardiovascular ...outcomes in population-based studies and in patients with ischemic heart failure (HF) and reduced left ventricular ejection fraction (LVEF). Yet, the impact of CHIP on HF progression, including nonischemic etiology, is unknown.
The purpose of this study was to assess the clinical impact of clonal hematopoiesis on HF progression irrespective of its etiology.
The study cohort comprised 62 patients with HF and LVEF <45% (age 74 ± 7 years, 74% men, 52% nonischemic, and LVEF 30 ± 8%). Deep sequencing was used to detect CHIP mutations with a variant allelic fraction >2% in 54 genes. Patients were followed for at least 3.5 years for various adverse events including death, HF-related death, and HF hospitalization.
CHIP mutations were detected in 24 (38.7%) patients, without significant differences in all-cause mortality (p = 0.151). After adjusting for risk factors, patients with mutations in either DNA methyltransferase 3 alpha (DNMT3A) or Tet methylcytosine dioxygenase 2 (TET2) exhibited accelerated HF progression in terms of death (hazard ratio HR: 2.79; 95% confidence interval CI: 1.31 to 5.92; p = 0.008), death or HF hospitalization (HR: 3.84; 95% CI: 1.84 to 8.04; p < 0.001) and HF-related death or HF hospitalization (HR: 4.41; 95% CI: 2.15 to 9.03; p < 0.001). In single gene-specific analyses, somatic mutations in DNMT3A or TET2 retained prognostic significance with regard to HF-related death or HF hospitalization (HR: 4.50; 95% CI: 2.07 to 9.74; p < 0.001, for DNMT3A mutations; HR: 3.18; 95% CI: 1.52 to 6.66; p = 0.002, for TET2 mutations). This association remained significant irrespective of ischemic/nonischemic etiology.
Somatic mutations that drive clonal hematopoiesis are common among HF patients with reduced LVEF and are associated with accelerated HF progression regardless of etiology.
Abstract Obesity is a risk factor for various cardiovascular diseases including hypertension, atherosclerosis, and myocardial infarction. Recent studies aimed at understanding the microenvironment of ...adipose tissue and its impact on systemic metabolism have shed light on the pathogenesis of obesity-linked cardiovascular diseases. Adipose tissue functions as an endocrine organ by secreting multiple immune-modulatory proteins known as adipokines. Obesity leads to increased expression of pro-inflammatory adipokines and diminished expression of anti-inflammatory adipokines, resulting in the development of a chronic, low-grade inflammatory state. This adipokine imbalance is thought to be a key event in promoting both systemic metabolic dysfunction and cardiovascular disease. This review will focus on the adipose tissue microenvironment and the role of adipokines in modulating systemic inflammatory responses that contribute to cardiovascular disease.
Human aging is associated with an increased frequency of somatic mutations in hematopoietic cells. Several of these recurrent mutations, including those in the gene encoding the epigenetic modifier ...enzyme TET2, promote expansion of the mutant blood cells. This clonal hematopoiesis correlates with an increased risk of atherosclerotic cardiovascular disease. We studied the effects of the expansion of Tet2-mutant cells in atherosclerosis-prone, low-density lipoprotein receptor–deficient (Ldlr
–/–) mice. We found that partial bone marrow reconstitution with TET2-deficient cells was sufficient for their clonal expansion and led to a marked increase in atherosclerotic plaque size. TET2-deficient macrophages exhibited an increase in NLRP3 inflammasome–mediated interleukin-1β secretion. An NLRP3 inhibitor showed greater atheroprotective activity in chimeric mice reconstituted with TET2-deficient cells than in nonchimeric mice. These results support the hypothesis that somatic TET2 mutations in blood cells play a causal role in atherosclerosis.
Cancer genomes have long been known to carry a high number of somatic mutations distributed across many genes. However, recent sequencing studies have unveiled that non-cancerous cells also carry a ...considerable number of somatic mutations, which are acquired continuously through the lifespan. Accordingly, the pathophysiological relevance of somatic mutagenesis beyond cancer has become a topic of intensive research. Human genetic studies and experiments in mice have shown that some somatic mutations in the hematopoietic system provide a competitive advantage to the mutant cell and allow its clonal expansion. This phenomenon, termed clonal hematopoiesis, is typically driven by mutations in known oncogenes and tumor suppressor genes, and it is associated with a higher risk of hematological malignancies. Unexpectedly, accumulating genetic and experimental evidence strongly suggest that clonal hematopoiesis, at least when driven by certain mutations, also contributes causally to the development of cardiovascular disease and, therefore, represents a new cardiovascular risk factor. While clonal hematopoiesis is relatively common in healthy individuals, especially among the elderly, it is particularly frequent in cancer patients and survivors. Hence, it has emerged as a candidate contributor to the increased risk of cardiovascular complications in cancer patients. This review summarizes our current understanding of the connection between clonal hematopoiesis and cardiovascular disease, with a special focus on the available evidence linking clonal hematopoiesis to cardiovascular disorders that are frequent in cancer patients and survivors.
•Somatic mutations that drive clonal hematopoiesis represent a new cardiovascular risk factor.•Clonal hematopoiesis is particularly common in elderly individuals and cancer patients.•Some clonal hematopoiesis-related mutations contribute directly to cardiovascular disease.•Cytotoxic therapies facilitate clonal hematopoiesis driven by mutations in DNA damage response genes.
Interleukin‐6 (IL‐6) is a pleiotropic cytokine with complex roles in inflammation and metabolic disease. While typically regarded as a pro‐inflammatory cytokine, multiple studies in the last 20 years ...have generated conflicting data on the role of IL‐6 in inflammation and metabolism. In a recent study in Nature Immunology, Brüning and collaborators demonstrate that IL‐6 signaling in myeloid cells attenuates obesity‐induced inflammation and insulin resistance by promoting macrophage alternative activation (Mauer et al, ). This study unveils a new and surprising anti‐inflammatory action of IL‐6 and further highlights the complex actions of this cytokine.
Most recent work from the Brüning laboratory determines an unexpected, anti‐inflammatory role of IL‐6 in obesity‐associated insulin resistance by virtue of alternative macrophage polarization.
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