Age-related Cardiac Dysfunction Research Articles

Effects of sacubitril-valsartan on aging-related cardiac dysfunction

Heart failure (HF) remains a huge medical burden worldwide, with aging representing a major risk factor. Here, we report the effects of sacubitril/valsartan, an approved drug for HF with reduced EF, in an experimental model of aging-related HF with preserved ejection fraction (HFpEF).Eighteen-month-old female Fisher 344 rats were treated for 12 weeks with sacubitril/valsartan (60 mg/kg/day) or with valsartan (30 mg/kg/day). Three-month-old rats were used as control.No differential action of sacubitril/valsartan versus valsartan alone, either positive or negative, was observed. The positive effects of both sacubitril/valsartan and valsartan on cardiac hypertrophy was evidenced by a significant reduction of wall thickness and myocyte cross-sectional area. Contrarily, myocardial fibrosis in aging heart was not reduced by any treatment. Doppler echocardiography and left ventricular catheterization evidenced diastolic dysfunction in untreated and treated old rats. In aging rats, both classical and non-classical renin-angiotensin-aldosterone system (RAAS) were modulated. In particular, with respect to untreated animals, both sacubitril/valsartan and valsartan showed a partial restoration of cardioprotective non-classical RAAS.In conclusion, this study evidenced the favorable effects, by both treatments, on age-related cardiac hypertrophy. The attenuation of cardiomyocyte size and hypertrophic response may be linked to a shift towards cardioprotective RAAS signaling. However, diastolic dysfunction and cardiac fibrosis persisted despite of treatment and were accompanied by myocardial inflammation, endothelial activation, and oxidative stress.

Combined Endurance and Resistance Exercise Mitigates Age-Associated Cardiac Dysfunction.

Aging is associated with a decline in cardiac function. Exercise has been shown to effectively reduce the risks of cardiovascular diseases. Here whether a combination of endurance and resistance exercises can improve cardiac function in aged mice during late life is investigated. Through transcriptome analysis, several signaling pathways activated in the hearts of 22-month-old mice after combined exercise, including cardiac muscle contraction, mitophagy, and longevity regulation are identified. Combined exercise training mitigated age-associated pathological cardiac hypertrophy, reduced oxidative stress, cardiac senescence, and enhanced cardiac function. Upstream stimulatory factor 2 (Usf2) is upregulated in the aged mouse hearts with combined exercise compared to sedentary mice. In the human cardiomyocytes senescent model, overexpression of Usf2 led to anti-senescence effects, while knockdown of Usf2 exacerbated cellular senescence. The results suggest that a combination of endurance and resistance exercises, such as swimming and resistance running, can mitigate age-related pathological cardiac remodeling and cardiac dysfunction in late life. These cardioprotective effects are likely due to the activation of Usf2 and its anti-senescence effect. Therefore, Usf2 can potentially be a novel therapeutic target for mitigating age-related cardiac dysfunction.

Isthmin-1 Improves Aging-Related Cardiac Dysfunction in Mice through Enhancing Glycolysis and SIRT1 Deacetylase Activity.

Aging-related cardiac dysfunction poses a major risk factor of mortality for elderly populations, however, efficient treatment for aging-related cardiac dysfunction is far from being known. Isthmin-1 (ISM1) is a novel adipokine that promotes glucose uptake and acts indispensable roles in restraining inflammatory and fibrosis. The present study aims to investigate the potential role and molecular mechanism of ISM1 in aging-related cardiac dysfunction. Aged and matched young mice were overexpressed or silenced with ISM1 to investigate the role of ISM1 in aging-related cardiac dysfunction. Moreover, H9C2 cells were stimulated with D-galactose (D-gal) to examine the role of ISM1 in vitro. Herein, we found that cardiac-specific overexpression of ISM1 significantly mitigated insulin resistance by promoting glucose uptake in aging mice. ISM1 overexpression alleviated while ISM1 silencing deteriorated cellular senescence, cardiac inflammation, and dysfunction in natural and accelerated cardiac aging. Mechanistically, ISM1 promoted glycolysis and activated Sirtuin-1 (SIRT1) through increasing glucose uptake. ISM1 increased glucose uptake via translocating GLUT4 to the surface, thereby enhancing glycolytic flux and hexosamine biosynthetic pathway (HBP) flux, ultimately leading to increased SIRT1 activity through O-GlcNAc modification. ISM1 may serve as a novel potential therapeutic target for preventing aging-related cardiac disease in elderly populations. ISM1 prevents aging-related cardiac dysfunction by promoting glycolysis and enhancing SIRT1 deacetylase activity, making it a promising therapeutic target for aging-related cardiac disease.

Age-Induced Accumulation of Succinate Promotes Cardiac Fibrogenesis.

Age-related cardiac fibrosis is a risk factor for heart failure and a marker for heart aging. However, the mechanisms underlying age-related cardiac fibrosis remain unclear. Ischemia and hypoxia are inevitable events in the aging process, which are direct causes of mitochondrial dysfunction and metabolic alterations. In this study, we identified metabolic changes and determined the mechanisms by which succinate (a tricarboxylic acid cycle intermediate) accumulation promotes fibroblast activation and apoptosis resistance in the aging heart. We also assessed its significance in relation to cardiac fibrosis and diastolic dysfunction. We first investigated how aging promotes persistent cardiac fibrosis. Following this, the metabolic alterations of the aging heart were identified by untargeted metabolomics, and the succinate level was verified via quantitative analysis. Furthermore, the correlations between succinate and fibrosis or diastolic dysfunction in older mice/people were assessed. We also described the role of succinate and its receptor SUCNR1/GPR91 in establishing a fibrosis network during diastolic dysfunction with age using SUCNR1-/- mouse model and an AAV9-based approach. We further identified the specific mechanisms involved in PKM2 dimerization, which regulate fibroblast activation and apoptosis resistance. We demonstrated that aging promotes fibrogenesis and diastolic dysfunction, which are linked to fibroblast activation and apoptosis resistance in the heart. Succinate levels were correlated with diastolic dysfunction and cardiac fibrosis in older mice and people. Functionally, succinate promoted fibroblast activation and apoptosis resistance, which aggravate cardiac fibrosis formation in both young and old mice. This was attributed to the ability of succinate to stimulate PKM2 dimerization via succinate receptor SUCNR1. Furthermore, dimeric PKM2 translocated to the nucleus and mitochondria, where it promoted fibroblast activation and apoptosis resistance, respectively. Accumulated PKM2 in the nucleus interacted with HIF-1α, increasing the DNA binding of HIF-1α and the expression of fibrogenic genes, resulting in fibroblast activation. In the mitochondria, accumulated PKM2 phosphorylated VDAC1 at T93 and increased VDAC1 degradation by promoting SYVN1-based E3 ligase binding to VDAC1, which is associated with increased apoptosis resistance and fibrosis persistence. We found that targeting succinate accumulation by metformin can inhibit fibroblast activation and apoptosis resistance in mice, which is a potential strategy to control age-related cardiac fibrosis and diastolic dysfunction. Our findings indicate that targeting metabolic dysregulation has significant implications for the treatment of age-related cardiac fibrosis and diastolic dysfunction. We further demonstrate a novel mechanism by which succinate induces fibroblast activation and apoptosis resistance by promoting PKM2 dimerization. Hence, inhibiting succinate generation or blocking its downstream effects is potentially a promising new strategy for slowing the heart aging.

Abstract 13603: Inhibition of Exercise-Regulated Long Noncoding RNA SALTe1 Reverses Vascular Aging and Age-Related Cardiac Dysfunction

Rationale: Age is a major risk factor for cardiovascular disease. Recent work suggests vascular aging is an important determinant of longevity and end-organ function, although its role in age-related cardiac dysfunction and how exercise mitigates these phenotypes remain unclear. Objective: To identify exercise-regulated, cardiac long noncoding RNAs (lncRNAs) that modulate vascular aging. Methods and Results: Twenty-month-old mice underwent voluntary wheel running for eight weeks. RNAseq identified a novel set of lncRNAs altered in exercised aged hearts, termed S enescence A ssociated L ncRNA T ranscripts in E xercise (SALTes). SALTe1 was conserved and primarily expressed in endothelial cells (ECs). SALTe1 increased in aged hearts but decreased with exercise. Myocardial perfusion and CD31 positive cells were reduced in 20-month-old vs 10-week-old mice while EC senescence (CD31 and p16 or γH2AX double-positive cells) and cardiac diastolic dysfunction increased (p<0.05 for all). In 20-month-old mice, SALTe1 inhibition using antisense GapmeR or EC-specific knockdown in CAS9-mice reversed multiple hallmarks of vascular aging. Recovery from hindlimb ischemia improved (post-surgery day 28 perfusion ratio, Control: 0.58±0.03 vs GapmeR: 0.73±0.03, p=0.04, n=12/group) and aortic stiffness was reduced to levels seen in young animals. Myocardial perfusion (time-to-peak, Control: 2.585±0.08 vs GapmeR: 2.048±0.11 seconds, p=0.03, n=12/group) improved. Cardiac EC number increased, and EC senescence decreased (p<0.05 for all). Inhibition of SALTe1 reduced E/E’ (-20.16±1.60 vs -15.4±1.10, p=0.04, n=12/group) and increased global longitudinal strain (-15.88±0.84 vs 20.66±1.02, p=0.02, n=12/group). Mechanistic studies in vitro and in vivo revealed that SALTe1 works through regulation of Poly (ADP-Ribose) Polymerase Family Member 9 (PARP9) and RNA-binding protein with multiple splicing (RBPMS). Conclusions: SALTe1 regulates EC senescence through PARP9 and RBPMS. SALTe1 inhibition reverses multiple hallmarks of vascular aging and improves age-related cardiac dysfunction. These findings suggest a primary role for EC senescence in age-related cardiac dysfunction and identify SALTe1 as a potential new therapeutic target.

Neutrophil peptidylarginine deiminase 4 is essential for detrimental age-related cardiac remodelling and dysfunction in mice.

Mice fully deficient in peptidylarginine deiminase 4 (PAD4) enzyme have preserved cardiac function and reduced collagen deposition during ageing. The cellular source of PAD4 is hypothesized to be neutrophils, likely due to PAD4's involvement in neutrophil extracellular trap release. We investigated haematopoietic PAD4 impact on myocardial remodelling and systemic inflammation in cardiac ageing by generating mice with Padi4 deletion in circulating neutrophils under the MRP8 promoter (Ne-PAD4-/-), and ageing them for 2 years together with littermate controls (PAD4fl/fl). Ne-PAD4-/- mice showed protection against age-induced fibrosis, seen by reduced cardiac collagen deposition. Echocardiography analysis of structural and functional parameters also demonstrated preservation of both systolic and diastolic function with MRP8-driven PAD4 deletion. Furthermore, cardiac gene expression and plasma cytokine levels were evaluated. Cardiac genes and plasma cytokines involved in neutrophil recruitment were downregulated in aged Ne-PAD4-/- animals compared to PAD4fl/fl controls, including decreased levels of C-X-C ligand 1 (CXCL1). Our data confirm PAD4 involvement from circulating neutrophils in detrimental cardiac remodelling, leading to cardiac dysfunction with old age. Deletion of PAD4 in MRP8-expressing cells impacts the CXCL1-CXCR2 axis, known to be involved in heart failure development. This supports the future use of PAD4 inhibitors in cardiovascular disease. This article is part of the Theo Murphy meeting issue 'The virtues and vices of protein citrullination'.

SIRT2 counteracts primate cardiac aging via deacetylation of STAT3 that silences CDKN2B.

Aging is a major risk factor contributing to pathophysiological changes in the heart, yet its intrinsic mechanisms have been largely unexplored in primates. In this study, we investigated the hypertrophic and senescence phenotypes in the hearts of aged cynomolgus monkeys as well as the transcriptomic and proteomic landscapes of young and aged primate hearts. SIRT2 was identified as a key protein decreased in aged monkey hearts, and engineered SIRT2 deficiency in human pluripotent stem cell-derived cardiomyocytes recapitulated key senescence features of primate heart aging. Further investigations revealed that loss of SIRT2 in human cardiomyocytes led to the hyperacetylation of STAT3, which transcriptionally activated CDKN2B and, in turn, triggered cardiomyocyte degeneration. Intra-myocardial injection of lentiviruses expressing SIRT2 ameliorated age-related cardiac dysfunction in mice. Taken together, our study provides valuable resources for decoding primate cardiac aging and identifies the SIRT2-STAT3-CDKN2B regulatory axis as a potential therapeutic target against human cardiac aging and aging-related cardiovascular diseases.

Saponins of Panax japonicus ameliorates cardiac aging phenotype in aging rats by enhancing basal autophagy through AMPK/mTOR/ULK1 pathway

Heart disease is a significant health concern for elderly individuals, with heart aging being the primary cause. Recent studies have shown that autophagy can play a protective role in preventing cardiac aging. Our previous research confirmed that Chikusetsu saponin IVa, a fundamental component of Saponins of Panax japonics (SPJ), can enhance basic autophagy levels in cardiomyocyte of isoproterenol induced cardiac fibrosis mice. However, it remains unclear whether SPJ possesses a protective effect on cardiac dysfunction during the natural aging process. Rats were randomly divided into four groups: adult control group (6 months old), aging group (24 months old), aging group treated with 10 mg/kg SPJ, and aging group treated with 30 mg/kg SPJ. The heart function, blood pressure, and heart mass index (HMI) were measured. Hematoxylin and eosin staining (H&E) and Wheat Germ Agglutinin (WGA) staining were used to observe the changes in morphology, while Masson staining was used to examine collagen deposition in the rat hearts and CD45 immunohistochemistry was conducted to examine the macrophage infiltration in heart tissues. TUNEL kit was used to detect apoptosis level of cardiomyocyte, and western blot was used to evaluate autophagy-related proteins as well as AMPK/mTOR/ULK1 pathway-related markers. SPJ treatment improved the cardiac function, reduced HMI, attenuated myocardial fiber disorder, inhibited inflammatory cell infiltration, and decreased collagen deposition and cardiomyocyte apoptosis in aging rats. Additionally, SPJ treatment decreased the expression of aging-related proteins and restored the expression of autophagy-related markers. SPJ activated autophagy through the activation of AMPK, which in turn increased the phosphorylation of ULK1(Ser555), while inhibited the phosphorylation of mTOR and ULK1(Ser757). Our study demonstrates that SPJ improves the cardiac function of aging rats by enhancing basal autophagy through the AMPK/mTOR/ULK1 pathway. These results offer a theoretical foundation and empirical evidence to support the clinical advancement of SPJ in enhancing age-related cardiac dysfunction.

Abstract P3116: Age-Related Cardiac Changes In S-Nitrosoglutathione Reductase Knockout Mice

Age associated cardiac aging differs between males and females, yet these age-related sex-dimorphic pathways remain poorly explored. We have previously shown that inhibition of S-nitrosoglutathione reductase (GSNOR) was cardioprotective during ischemic injury in male but not female mice. We therefore, hypothesized that GSNOR activity might play a role in sex-related differences in cardiac aging, and GSNOR deletion (KO) might exacerbate age-related cardiac dysfunction in females but not males. WT and KO mice underwent longitudinal 2D-echocardiography at 4, 7, 10 and 14 months of age, and echocardiographic data were analyzed with mixed-effects analysis. We saw a significant decrease in GSNOR activity in old (18 months) WT mice relative to young (4 months) in both sexes but more pronounced in males (p<0.0001) vs. females (p=0.02). Left ventricular (LV) internal diameter at end-diastole significantly increased with age in WT males (2.65 ± 0.02 to 3.60 ± 0.13) and females (2.61 ± 0.02 to 3.32 ± 0.04) with a significant effect of sex across age (p<0.0001). LV Mass (indexed to group body weight at 18 months) increased with age in both males (82 ± 2 to 127 ± 3) and females (85 ± 3 to 113 ± 3) with a significant age and sex interaction (p<0.0001). Similar trends were observed for other echocardiographic parameters. Contrary to our hypothesis, the age- and sex-related differences observed in WT were absent in KO mice. LV internal diameter at end-diastole and LV Mass did not significantly change in male or female KO mice from 4 to 14 months of age neither did the majority of echocardiographic parameters tested. No differences were observed between male and female KO mice. Taken together, our data show that GSNOR deletion attenuates aging-induced cardiac dysfunction and abrogates age-related sex differences in the mouse heart.

A masked, placebo-controlled, randomized clinical trial evaluating safety and the effect on cardiac function of low-dose rapamycin in 17 healthy client-owned dogs.

Geroscience studies of low-dose rapamycin in laboratory species have identified numerous benefits, including reversing age-related cardiac dysfunction. Cardiovascular benefits have been observed in dogs with 10 weeks of treatment, raising questions about possible benefits and adverse effects of long-term use of low-dose rapamycin. The objectives of this study were to assess the impact of 6 months of low-dose rapamycin on echocardiographic indices of cardiac function in healthy dogs and to document the occurrence of adverse events. Seventeen client-owned dogs aged 6-10 years, weighing 18-36 kg, and without significant systemic disease were included in a prospective, randomized, placebo-controlled, masked clinical trial. Low-dose rapamycin (0.025 mg/kg) or placebo was administered three times per week for 6 months. Baseline, 6-month, and 12-month evaluation included physical examination, cardiology examination, and clinicopathology. Three-month evaluation included physical examination and clinicopathology. Owners completed online questionnaires every 2 weeks. There were no statistically significant differences in echocardiographic parameters between rapamycin and placebo groups at 6 or 12 months. No clinically significant adverse events occurred. In 26.8% of the bi-weekly surveys owners whose dogs received rapamycin reported perceived positive changes in behavior or health, compared to 8.1% in the placebo group (p = 0.04). While no clinically significant change in cardiac function was observed in dogs treated with low-dose rapamycin, the drug was well-tolerated with no significant adverse events.

Kielin/chordin-like protein deficiency causes cardiac aging in male mice.

Previous studies have demonstrated that bone morphogenetic proteins (BMPs) play important roles in cardiovascular diseases, including atherosclerosis, artery calcification, myocardial remodeling, pulmonary arterial hypertension, and diabetic cardiomyopathy. Kielin/chordin-like protein (KCP) is a secreted protein that regulates the expression and function of BMPs. However, the role of KCP in cardiac aging remains unknown. In this study, we aimed to investigate the role of KCP in cardiac aging and its possible mechanisms. Echocardiogram showed that heart function was impaired in aged mice (24 months). In addition, analysis of heart structure showed that KCP knockout (KO) aggravated cardiac remodeling in aged mice. Moreover, KCP KO increased p-smad2/3 and TGF-β expression, while decreased BMP-2 expression in aged mice. Furthermore, KCP KO increased the expression of cardiac senescence-related proteins in aged mice. KCP KO aggravated the imbalance of oxidants and antioxidants and increased the expression of proinflammatory cytokines and cardiomyocyte apoptosis in aged mice. Our study demonstrated that KCP KO aggravated cardiac aging in mice by increasing the levels of oxidative stress, inflammation, and cardiomyocyte apoptosis. KEY MESSAGE: KCP KO aggravated aging-related cardiac dysfunction and remodeling in male mice. KCP KO aggravated cardiac aging by increasing the levels of oxidative stress, inflammation, and cardiomyocyte apoptosis.

Cardiac-Specific Expression of Cre Recombinase Leads to Age-Related Cardiac Dysfunction Associated with Tumor-like Growth of Atrial Cardiomyocyte and Ventricular Fibrosis and Ferroptosis.

Transgenic expression of Cre recombinase driven by a specific promoter is normally used to conditionally knockout a gene in a tissue- or cell-type-specific manner. In αMHC-Cre transgenic mouse model, expression of Cre recombinase is controlled by the myocardial-specific α-myosin heavy chain (αMHC) promoter, which is commonly used to edit myocardial-specific genes. Toxic effects of Cre expression have been reported, including intro-chromosome rearrangements, micronuclei formation and other forms of DNA damage, and cardiomyopathy was observed in cardiac-specific Cre transgenic mice. However, mechanisms associated with Cardiotoxicity of Cre remain poorly understood. In our study, our data unveiled that αMHC-Cre mice developed arrhythmias and died after six months progressively, and none of them survived more than one year. Histopathological examination showed that αMHC-Cre mice had aberrant proliferation of tumor-like tissue in the atrial chamber extended from and vacuolation of ventricular myocytes. Furthermore, the αMHC-Cre mice developed severe cardiac interstitial and perivascular fibrosis, accompanied by significant increase of expression levels of MMP-2 and MMP-9 in the cardiac atrium and ventricular. Moreover, cardiac-specific expression of Cre led to disintegration of the intercalated disc, along with altered proteins expression of the disc and calcium-handling abnormality. Comprehensively, we identified that the ferroptosis signaling pathway is involved in heart failure caused by cardiac-specific expression of Cre, on which oxidative stress results in cytoplasmic vacuole accumulation of lipid peroxidation on the myocardial cell membrane. Taken together, these results revealed that cardiac-specific expression of Cre recombinase can lead to atrial mesenchymal tumor-like growth in the mice, which causes cardiac dysfunction, including cardiac fibrosis, reduction of the intercalated disc and cardiomyocytes ferroptosis at the age older than six months in mice. Our study suggests that αMHC-Cre mouse models are effective in young mice, but not in old mice. Researchers need to be particularly careful when using αMHC-Cre mouse model to interpret those phenotypic impacts of gene responses. As the Cre-associated cardiac pathology matched mostly to that of the patients, the model could also be employed for investigating age-related cardiac dysfunction.

Regular Exercise in Drosophila Prevents Age-Related Cardiac Dysfunction Caused by High Fat and Heart-Specific Knockdown of skd.

Skuld (skd) is a subunit of the Mediator complex subunit complex. In the heart, skd controls systemic obesity, is involved in systemic energy metabolism, and is closely linked to cardiac function and aging. However, it is unclear whether the effect of cardiac skd on cardiac energy metabolism affects cardiac function. We found that cardiac-specific knockdown of skd showed impaired cardiac function, metabolic impairment, and premature aging. Drosophila was subjected to an exercise and high-fat diet (HFD) intervention to explore the effects of exercise on cardiac skd expression and cardiac function in HFD Drosophila. We found that Hand-Gal4>skd RNAi (KC) Drosophila had impaired cardiac function, metabolic impairment, and premature aging. Regular exercise significantly improved cardiac function and metabolism and delayed aging in HFD KC Drosophila. Thus, our study found that the effect of skd on cardiac energy metabolism in the heart affected cardiac function. Exercise may counteract age-related cardiac dysfunction and metabolic disturbances caused by HFD and heart-specific knockdown of skd. Skd may be a potential therapeutic target for heart disease.

The mTOR signaling pathway in cardiac aging.

The mammalian target of rapamycin (mTOR) is one of the most important signaling pathways that regulate nutrient sensing, cell growth, metabolism, and aging. The mTOR pathway, particularly mTOR complex 1 (mTORC1), has been shown to control aging, lifespan, and healthspan through the regulation of protein synthesis, autophagy, mitochondrial function, and metabolic health. The mTOR pathway also plays critical roles in the heart, from cardiac development, growth and maturation, and maintenance of cardiac homeostasis. Hyperactivation of mTORC1 signaling is well documented in aging and many age-related pathologies, including age-related cardiac dysfunction and heart failure. Suppression of mTORC1 by calorie restriction or rapamycin not only extends lifespan but also restores youthful phenotypes in the heart. In this article, we review model organisms of cardiac aging and highlight recent advances in the impact of the mTORC1 pathway on organismal and cardiac aging, particularly in Drosophila and mice. We focus on the downstream signaling pathways S6 kinase and 4EBP1, which regulates protein synthesis, as well as ULK1 and its related pathway that regulates autophagy. The interaction with mTOR complex 2 (mTORC2) and its potential role in cardiac aging are also discussed.

Nuclear remodeling drives age-related cardiac dysfunction.

Nuclear remodeling drives age-related cardiac dysfunction.

Abstract 11782: Senolytic Therapy Improves Diastolic Cardiac Function in Aged Mice

Introduction: Cellular senescence, an irreversible arrest of the cell cycle, is a recognized hallmark of aging that contributes to age-related multi-organ dysfunction and diseases. Evidence suggests that cardiomyocyte senescence plays a critical role in the development of age-related cardiac dysfunction. We tested the hypothesis that targeting senescent cells via intermittent administration of the senolytic drugs dasatinib and quercetin (D&Q) will improve cardiac dysfunction in old mice. Methods: 21-month-old C57Bl/6 mice were treated with D&Q or vehicle via oral gavage on a bi-monthly basis for three months. Systolic and diastolic cardiac function were assessed using echocardiography. Expression of inflammatory and matrix metalloproteinase genes was assessed using quantitative polymerase chain reactions. Cardiac tissue morphology was assessed by histological analysis. Results: D&Q treatment improved ejection fraction (EF) in old mice (60.3% vs. 64.5%, con vs. D&Q, p = 0.0207, n=18). Global longitudinal strain was improved by D&Q treatment (-13.99% vs. -17.03%, con vs. D&Q, p=.0005, n=18). Measures of diastolic function were improved after D&Q treatment (n=18 for all): E/E’ (27.60 vs. 20.08, con vs. D&Q, p<.0001), isovolumetric relaxation time (IVRT, 22.74ms vs. 14.99ms, con vs. D&Q, p<.0001), and reverse longitudinal strain rate (rLSR, 4.64 1/s vs. 13.41 1/s, con vs. D&Q, p<.0001). Expression of inflammatory and matrix metalloproteinase genes ( cd3e, foxp3, tnf- α, mcp-1, mmp9 ) was lower in hearts from D&Q treated compared to control mice (p≤0.05). Extracellular matrix collagen expression was lower in cardiac tissue from D&Q treated compared to control (p<0.01). Conclusions: For the first time we report a significant improvement in diastolic function in aged mice when treated long term with the senolytic therapy dasatinib and quercetin. Measurements of systolic function also improved, but not to the same degree as observed for diastolic function. Overall, senolytic therapy with D&Q represents an attractive option to explore for the treatment of diastolic heart failure in humans.

Knockout of Trpa1 accelerates age-related cardiac fibrosis and dysfunction.

Age-related cardiac fibrosis contributes to the development of heart failure with preserved ejection fraction which lacks ideal treatment. Transient receptor potential ankyrin 1 (TRPA1) is an oxidative stress sensor and could attenuate age-related pathologies in invertebrates. The present study aimed to test whether TRPA1 plays a role in age-related cardiac remodeling and dysfunction. The cardiac function and pathology of 12-week-old (young) and 52-week-old (older) Trpa1-/- mice and wild-type (WT) littermates were evaluated by echocardiography and histologic analyses. The expression levels of 84 fibrosis-related genes in the heart were measured by quantitative polymerase chain reaction array. Young Trpa1-/- and WT mice had similar left ventricular wall thickness, volume, and systolic and diastolic function. Older Trpa1-/- mice had significantly increased left ventricular internal diameter and volume and impaired systolic (lower left ventricular ejection fraction) and diastolic (higher E/A ratio and isovolumetric relaxation time) functions compared with older WT mice (P<0.05 or P<0.01). Importantly, older Trpa1-/- mice had enhanced cardiac fibrosis than older WT mice (P<0.05) while the two strains had similar degree of cardiac hypertrophy. Among the 84 fibrosis-related genes, Acta2, Inhbe, Ifng, and Ccl11 were significantly upregulated, while Timp3, Stat6, and Ilk were significantly downregulated in the heart of older Trpa1-/- mice compared with older WT mice. Taken together, we found that knocking out Trpa1 accelerated age-related myocardial fibrosis, ventricular dilation, and cardiac dysfunction. These findings suggest that TRPA1 may become a therapeutic target for preventing and/or treating cardiac fibrosis and heart failure with preserved ejection fraction in the elderly.

Fibronectin type III domain-containing 5 improves aging-related cardiac dysfunction in mice.

Aging is an important risk factor for cardiovascular diseases, and aging‐related cardiac dysfunction serves as a major determinant of morbidity and mortality in elderly populations. Our previous study has identified fibronectin type III domain‐containing 5 (FNDC5) and its cleaved form, irisin, as the cardioprotectant against doxorubicin‐induced cardiomyopathy. Herein, aging or matched young mice were overexpressed with FNDC5 by adeno‐associated virus serotype 9 (AAV9) vectors, or subcutaneously infused with irisin to uncover the role of FNDC5 in aging‐related cardiac dysfunction. To verify the involvement of nucleotide‐binding oligomerization domain‐like receptor with a pyrin domain 3 (NLRP3) and AMP‐activated protein kinase α (AMPKα), Nlrp3 or Ampkα2 global knockout mice were used. Besides, young mice were injected with AAV9‐FNDC5 and maintained for 12 months to determine the preventive effect of FNDC5. Moreover, neonatal rat cardiomyocytes were stimulated with tumor necrosis factor‐α (TNF‐α) to examine the role of FNDC5 in vitro. We found that FNDC5 was downregulated in aging hearts. Cardiac‐specific overexpression of FNDC5 or irisin infusion significantly suppressed NLRP3 inflammasome and cardiac inflammation, thereby attenuating aging‐related cardiac remodeling and dysfunction. In addition, irisin treatment also inhibited cellular senescence in TNF‐α‐stimulated cardiomyocytes in vitro. Mechanistically, FNDC5 activated AMPKα through blocking the lysosomal degradation of glucagon‐like peptide‐1 receptor. More importantly, FNDC5 gene transfer in early life could delay the onset of cardiac dysfunction during aging process. We prove that FNDC5 improves aging‐related cardiac dysfunction by activating AMPKα, and it might be a promising therapeutic target to support cardiovascular health in elderly populations.

Metabolic targets in cardiac aging and rejuvenation

Cardiac aging is accompanied by progressive loss of cellular function, leading to impaired heart function and heart failure. There is an urgent need for efficient strategies to combat this age-related cardiac dysfunction. A growing number of events suggest that age-related cardiac diseases are tightly related to metabolic imbalance. This review summarizes recent findings concerning metabolic changes during cardiac aging and highlights the therapeutic approaches that target metabolic pathways in cardiac aging.

Abstract 14038: Deficiency of Arachidonate 5-Lipoxygenase Intensifies Sepsis-Induced Cardiac Dysfunction in Aging

Introduction: Age-related cardiac dysfunction is a prime component of sepsis-induced multi-organ failure in the clinical setting. Arachidonate 5-lipoxygenase (5LOX) pathway and 5LOX-derived lipid mediators are critical in early inflammation and immune response signaling. In addition, 5LOX derived mediators activate macrophages and other cells to counter infection via surface receptors. However, the role of 5LOX in sepsis-induced cardiac dysfunction superimposed on aging is still under-investigated. Hypothesis: Given that the inflammatory role of 5LOX, we tested the hypothesis that deletion of 5LOX in aging would be deleterious to cardiac function in sepsis. Methods: To induce sepsis, lipopolysaccharide (LPS; E. coli O55:B5) was injected into aging male C57BL/6J (WT) and 5LOX -/- mice (18-20 months). To study heart function, molecular, and cellular mechanisms, mice were challenged with a single subcutaneous dose of LPS (20mg/kg) for 4 hours. Survival was monitored for 7 days post-LPS challenge to testify therapeutic application of outcome. Results: Lack of 5LOX increased mortality (~70%) in aging mice with severe depression in cardiac function post-LPS compared with age-matched WT controls. LPS challenge in 5LOX -/- aging mice decreased resolution mediators (RvD1) and inflammation mediators (LTB 4 ) in the spleen with robust recruitment of leukocytes in a spleno-cardiac manner indicative of non-resolving inflammation. The spleen monocytes (CD11b + ), macrophages (F4/80 + ), and neutrophils (Ly6G + ) were significantly decreased in 5LOX -/- mice post-LPS with the consistent increase in the heart. The absence of 5LOX blunted physiological inflammatory response in aging by attenuating TLR4 and CD169 in both the heart and spleen as a sign of immunosuppression. Conclusion: Our results suggest that 5LOX -/- aging mice fail to initiate physiological inflammation-resolution signaling in response to LPS-induced septic shock, leading to cardiac dysfunction and immunosuppression. Our study highlights the role of 5LOX and 5LOX-derived mediators as targets for the inflammation-resolution response and therapeutics potential in aging-related sepsis.