ABSTRACT Diabetes and obesity increase cardiac lipid levels leading to cardiomyopathy and heart failure. We hypothesized that intermittent fasting would reduce cardiac lipid levels. Surprisingly, intermittent fasting increased myocardial triglyceride content, but rescued mortality and attenuated cardiomyopathy in mice overexpressing cardiomyocyte acyl-CoA synthetase 1 (MHC-ACSL1). Lipid overload caused cardiomyocyte accumulation of polyubiquitinated protein aggregates containing desmin, a scaffolding intermediate filament protein, which intermittent fasting prevented. Furthermore, intermittent fasting reversed elevated myocardial C16:0 ceramide content, and knockdown of ceramide synthase CerS5 and CerS6 reduced palmitate-induced protein aggregation, highlighting a role for C16:0 ceramides in this pathology. Conversely, impairing aggrephagy with cardiomyocyte-specific p62 ablation induced heart failure in mice fed a high-fat diet, with paradoxically reduced cardiac lipid content. Crucially, non-failing diabetic human hearts also exhibited protein aggregate pathology. Taken together, these results demonstrate that impaired proteostasis characterizes cardiomyopathy from cardiac lipid overload and identify a promising new therapeutic target for this condition.

BACKGROUND:Perivascular adipose tissue (PVAT) fine-tunes blood vessel contractility and vascular homeostasis. During obesity and atherosclerosis, PVAT becomes dysfunctional and loses its anticontractile potential. Previously, we reported that global knockout of adipose triglyceride lipase (ATGL), the major enzyme responsible for the breakdown of triglycerides, has the potential to modify PVAT functions. To address the causal relationship between PVAT lipolysis and blood vessel contractility, we analyzed ex vivo vasomotor function of mice with tissue-specific rescue/overexpression or knockout of ATGL in adipose tissue. METHODS:To generate mice lacking ATGL in all tissues except for adipose tissue (ATGL knockout with adipocyte-specific expression of ATGL [A+/AKO]), we crossed adipocyte ATGL-rescued (A+) mice with ATGL-deficient (ATGL knockout [AKO]) mice. Body weight, plasma levels of fatty acids, and blood glucose were compared between A+/AKO and AKO mice. Ex vivo vasoreactivity studies were performed in the absence and presence of PVAT to test for acute and chronic effects of PVAT on vascular function. RESULTS:Adipocyte-rescued AKO mice (A+/AKO) had significantly less amounts of PVAT than AKO controls while displaying moderate ATGL expression. A+/AKO aortas exhibited decreased anticontractile effects of PVAT compared with AKO aortas. This effect on contractile function was observed in an agonist-specific manner without affecting smooth muscle cell function or endothelium-dependent relaxation. Assessment of cardiac function using the Langendorff setup revealed that adipocyte ATGL selectively modulated vascular contractility without affecting systolic or diastolic performance. Studies using mice that express ATGL solely in cardiac muscle and adipocyte-specific ATGL knockout mice verified our findings in A+/AKO mice, revealing acute and chronic effects of adipocyte lipolysis on vasoreactivity. CONCLUSIONS:We provide the first evidence that changes in adipocyte lipolysis have the potential to regulate blood vessel contractility. Ablation of ATGL in adipocytes decreases vascular contractility and, thus, has the potential to prevent PVAT dysfunction in obesity and atherosclerosis.

Macroautophagy/autophagy is markedly inhibited in the hearts of elderly obese patients with heart failure and preserved ejection fraction (HFpEF). However, the therapeutic relevance and underlying signaling mechanisms of the decline of autophagy in HFpEF remain unclear. We observed that therapeutic nicotinamide adenine dinucleotide (NAD+) repletion via nicotinamide supplementation restores cardioprotective autophagy and mitophagy in preclinical models of obesity-related HFpEF. Targeted and untargeted cardiac acetylome profiling revealed no significant deacetylation of essential autophagy-related proteins, including ATG5, ATG7 and mammalian Atg8-family members (ATG8s), suggesting a SIRT (sirtuin)-independent mechanism of autophagy induction by nicotinamide. Instead, cardiac transcriptomic analysis revealed major shifts in insulin-IGF1 (insulin-like growth factor 1) signaling, a known autophagy inhibitory pathway. Nicotinamide supplementation reverses the HFpEF-associated increase in insulin-IGF1 signaling, whereas exogenous IGF1 counteracts nicotinamide-induced autophagy. Importantly, nicotinamide fails to exert cardioprotective effects in mice lacking the autophagy-related protein ATG5 in cardiomyocytes, implicating autophagy as essential for the therapeutic response. In patients with HFpEF, a metabolic shift diverting nicotinamide away from NAD+ biosynthesis toward catabolism strongly correlates with worsening heart failure and increased cardiovascular mortality, even after adjusting for traditional risk factors. In sum, we demonstrate that NAD+ replenishment improves cardiometabolic HFpEF by restoring cardiac autophagy through suppression of excessive IGF1 signaling.

Protein aggregates are emerging therapeutic targets in rare monogenic causes of cardiomyopathy and amyloid heart disease, but their role in more prevalent heart failure syndromes remains mechanistically unexamined. We observed mis-localization of desmin and sarcomeric proteins to aggregates in human myocardium with ischemic cardiomyopathy and in mouse hearts with post-myocardial infarction ventricular remodeling, mimicking findings of autosomal-dominant cardiomyopathy induced by R120G mutation in the cognate chaperone protein, CRYAB. In both syndromes, we demonstrate increased partitioning of CRYAB phosphorylated on serine-59 to NP40-insoluble aggregate-rich biochemical fraction. While CRYAB undergoes phase separation to form condensates, the phospho-mimetic mutation of serine-59 to aspartate (S59D) in CRYAB mimics R120G-CRYAB mutants with reduced condensate fluidity, formation of protein aggregates and increased cell death. Conversely, changing serine to alanine (phosphorylation-deficient mutation) at position 59 (S59A) restored condensate fluidity, and reduced both R120G-CRYAB aggregates and cell death. In mice, S59D CRYAB knock-in was sufficient to induce desmin mis-localization and myocardial protein aggregates, while S59A CRYAB knock-in rescued left ventricular systolic dysfunction post-myocardial infarction and preserved desmin localization with reduced myocardial protein aggregates. 25-Hydroxycholesterol attenuated CRYAB serine-59 phosphorylation and rescued post-myocardial infarction adverse remodeling. Thus, targeting CRYAB phosphorylation-induced condensatopathy is an attractive strategy to counter ischemic cardiomyopathy.

Significant progress in clinical care has extended human life expectancy to unprecedented levels. However, this trend has been parallelled by a rise in years lived with poor health, posing profound challenges not only to individual quality of life, but also to substantial medical and socioeconomic burdens at the population level. This underscores the urgent need for strategies that extend healthspan alongside lifespan. In this regard, nicotinamide adenine dinucleotide (NAD+) has emerged as a central metabolic cofactor and signaling molecule that regulates processes fundamental to health and longevity, including energy metabolism, mitochondrial function, inflammation, and DNA repair. Importantly, intracellular NAD+ levels decline with age across multiple tissues and organ systems, and restoring NAD+ content has been shown to reinstate cellular and physiological function in various model systems. Among the strategies to augment NAD+, supplementation with its precursors, namely nicotinic acid/niacin, nicotinamide, nicotinamide riboside, and nicotinamide mononucleotide, represents the most practical and extensively studied approach. Over the past two decades, preclinical research and an increasing number of clinical trials have investigated the therapeutic potential of these precursors in preventing or reversing age-associated decline and pathologies. In this review, we synthesize recent clinical advances, critically evaluate the promise and limitations of NAD+ precursor supplementation, and discuss future directions for leveraging NAD+ metabolism to improve healthspan in a rapidly aging global population.

Obesity is a modifiable major driver of heart failure with preserved ejection fraction (HFpEF), the most common and rapidly increasing form of heart failure. Current metabolic therapies, such as caloric restriction and incretin-based drugs, have shown promise in treating obesity-related HFpEF. However, these interventions neither specifically nor selectively improve adipose tissue metabolism, which is a key etiological factor in HFpEF that may offer a pathway to safer and more effective treatment strategies. Towards this end, we found that genetic inhibition of adipose triglyceride lipase (ATGL) specifically in adipocytes is sufficient to prevent the development of obesity-related HFpEF, and that pharmacological inhibition of ATGL using atglistatin effectively treats established disease. Atglistatin selectively inhibits ATGL in adipose tissue, but not in the heart, leading to superior reduction in adiposity and greater improvement in diastolic dysfunction compared to caloric restriction. These observations underscore the therapeutic potential of selectively targeting adipose tissue, independent of the effects of body weight loss. Mechanistically, atglistatin attenuates HFpEF-associated elevation of inflammatory cytokines, especially IL-1β levels in adipose tissue, more effectively than caloric restriction. In sum, these findings identify dysregulated adipose tissue metabolism as a causal factor and therapeutic target in maladaptive fat-heart crosstalk driving obesity-related HFpEF.

Ageing of the cardiovascular system is associated with frailty and various life-threatening diseases. As global populations grow older, age-related conditions increasingly determine healthspan and lifespan. The circulatory system not only supplies nutrients and oxygen to all tissues of the human body and removes by-products but also builds the largest interorgan communication network, thereby serving as a gatekeeper for healthy ageing. Therefore, elucidating organ-specific and cell-specific ageing mechanisms that compromise circulatory system functions could have the potential to prevent or ameliorate age-related cardiovascular diseases. In support of this concept, emerging evidence suggests that targeting the circulatory system might restore organ function. In this Roadmap, we delve into the organ-specific and cell-specific mechanisms that underlie ageing-related changes in the cardiovascular system. We raise unanswered questions regarding the optimal design of clinical trials, in which markers of biological ageing in humans could be assessed. We provide guidance for the development of gerotherapeutics, which will rely on the technological progress of the diagnostic toolbox to measure residual risk in elderly individuals. A major challenge in the quest to discover interventions that delay age-related conditions in humans is to identify molecular switches that can delay the onset of ageing changes. To overcome this roadblock, future clinical trials need to provide evidence that gerotherapeutics directly affect one or several hallmarks of ageing in such a manner as to delay, prevent, alleviate or treat age-associated dysfunction and diseases. In this Roadmap, Stellos and colleagues discuss the mechanisms of cardiovascular system ageing and how the ageing of blood, vessels and heart relates to the decline in organ function, and highlight potential therapeutic interventions, challenges in ageing research and future directions for preclinical and clinical studies.

The global increase in human life expectancy, coupled with an unprecedented rise in the prevalence of obesity, has led to a growing clinical and socioeconomic burden of heart failure with preserved ejection fraction (HFpEF). Mechanistically, the molecular and cellular hallmarks of aging are omnipresent in HFpEF and are further exacerbated by obesity and associated metabolic diseases. Conversely, weight loss strategies, particularly caloric restriction, have shown promise in improving health status in patients with HFpEF and are considered the gold standard for promoting longevity and healthspan (disease-free lifetime) in model organisms. In this review, we implicate fundamental mechanisms of aging in driving HFpEF and elucidate how caloric restriction mitigates the disease progression. Furthermore, we discuss the potential for pharmacologically mimicking the beneficial effects of caloric restriction in HFpEF using clinically approved and emerging caloric restriction mimetics. We surmise that these compounds could offer novel therapeutic avenues for HFpEF and alleviate the challenges associated with the implementation of caloric restriction and other lifestyle modifications to reduce the burden of HFpEF at a population level.

Aims: Sirtuin 4 (SIRT4) is a mitochondrially-localized stress-responsive NAD+-dependent deacetylase predominantly regulating energy metabolism and reactive oxygen species (ROS) homeostasis. Overexpression of SIRT4 aggravates angiotensin-induced cardiac hypertrophy, however underlying mechanisms remain incompletely elucidated. To current study was designed to explore mechanisms underlying adverse effects of increased SIRT4 levels in the heart following pressure overload. Methods and results: Mice with cardiomyocyte-specific overexpression of Sirt4 (cSirt4-Tg) or non-transgenic controls underwent transverse aortic constriction (TAC) or sham procedure. Cardiac structure, function and energy metabolism were assessed by echocardiography and working heart perfusions. Transcriptome analysis was performed using RNA sequencing. Nine weeks following TAC and thereafter, cSirt4-Tg mice displayed exacerbated cardiac dilation, dysfunction, and fibrosis compared to non-transgenic controls. This aggravation was accompanied by impaired rates of glycolysis and a blunted increase of mitochondrial respiratory capacity. More importantly, expression of numerous genes encoding collagens and profibrotic regulators was elevated. This profibrotic signaling was reversed by mitochondria-targeted antioxidant treatment using MitoQ, along with attenuation of cardiac dysfunction and reversal of structural remodeling. SIRT4 may drive oxidative stress and fibrotic signaling via increased NOX4 expression (>7-fold), and/or direct modulation of potential SIRT4 targets newly identified by Human Protein Microarray, including calcitonin gene-related peptide receptor component protein, cyclophilin A, and interleukin-2 receptor β. Conclusions: SIRT4 overexpression accelerates heart failure development in response to pressure overload, predominantly by ROS-mediated enhancement of profibrotic transcriptional signaling.

AIM:Sirtuin 5 (SIRT5), a mitochondrial NAD+-dependent deacylase, regulates fundamental cellular pathways, including energy substrate metabolism. The current study is designed to better elucidate the role of SIRT5 in the development of heart failure (HF). METHODS:Mice with cardiomyocyte-specific deletion (cSirt5-/-) or overexpression (cSirt5-Tg) of SIRT5 were generated and subjected to chronic pressure overload by transverse aortic constriction (TAC) or Sham surgery. Cardiac structure and function were assessed by echocardiography, isolated heart perfusions, and histology. MS-based metabolomics and bulk RNA sequencing were used to explore metabolic and molecular signatures. RESULTS:cSirt5-Tg mice had similar cardiac structure and function compared to control mice, whereas cSirt5-/- mice displayed exacerbated cardiac dilation and dysfunction following TAC, measured both in vivo by echocardiography and ex vivo in isolated heart perfusions. Metabolomics revealed accumulation of inosine and hypoxanthine, and depletion of adenosine, adenine, AMP, and ADP in cSirt5-/- hearts and following TAC, indicating dysregulation of purine metabolism. RNA-sequencing uncovered upregulation of purine-nucleoside phosphorylase and 5' nucleotidase, and downregulation of adenosine kinase (ADK) in cSirt5-/- hearts following TAC, indicating dysregulation at the interface of adenosine nucleotide salvage and purine degradation in the absence of SIRT5. Analyses of left ventricular tissue of patients with HF revealed reduced SIRT5 expression correlating with reduced ADK expression. CONCLUSION:Loss of SIRT5 in cardiomyocytes aggravates cardiac remodeling and dysfunction in response to chronic pressure overload, involving ATP precursor depletion due to transcriptional dysregulation of cardiac purine metabolism.

Heart failure (HF) is a major global and life-threatening disease. Despite advances in therapies, the prevalence of HF is increasing owing to an ageing population and the pervasive pandemic of obesity and metabolic disorders, which have transformed the pathophysiology of HF. Changes in cardiac energy metabolism and the related energy deficit crucially contribute to the severity and type of HF. Furthermore, perturbations in excitation–contraction coupling, mitochondrial function and oxidative stress are characteristic features of HF. In this Review, we focus on the close interaction between cardiac mechanics and mitochondrial energetics, and decipher how this mechano-energetic coupling is disturbed in various acquired and hereditary forms of HF. In HF with reduced ejection fraction, defects in excitation–contraction coupling are key drivers of mechano-energetic uncoupling, whereas in HF with preserved ejection fraction, increased preload and afterload imposed by obesity, hypertension and age-dependent vascular stiffness increase mechanical workload, which is insufficiently matched by mitochondrial tricarboxylic acid cycle activity and ATP supply. In both scenarios, oxidative stress results from depletion of the antioxidative capacity and contributes to maladaptive cardiac remodelling and dysfunction. Several established and emerging treatments for HF target this mechano-energetic uncoupling, and a greater understanding of the underlying mechanisms will open new therapeutic opportunities to alleviate the burden of HF. In this Review, the authors focus on the tight interaction between cardiac mechanics and mitochondrial energetics, discuss how this mechano-energetic coupling is disturbed in various acquired and inherited forms of heart failure, and summarize the established and emerging treatments for heart failure that target this mechano-energetic uncoupling.

Population aging and the associated increase in cardiovascular disease rates pose serious threats to global public health. Different forms of fasting have become an increasingly attractive strategy to directly address aging and potentially limit or delay the onset of cardiovascular diseases. A growing number of experimental studies and clinical trials indicate that the amount and timing of food intake as well as the daily time window during which food is consumed, are crucial determinants of cardiovascular health. Indeed, intermittent fasting counteracts the molecular hallmarks of cardiovascular aging and promotes different aspects of cardiometabolic health, including blood pressure and glycemic control, as well as body weight reduction. Here, we summarize current evidence from randomized clinical trials of intermittent fasting on body weight and composition as well as cardiovascular and metabolic risk factors. Moreover, we critically discuss the preventive and therapeutic potential of intermittent fasting, but also possible detrimental effects in the context of cardiovascular aging and related disease. We delve into the physiological mechanisms through which intermittent fasting might improve cardiovascular health, and raise important factors to consider in the design of clinical trials examining the efficacy of intermittent fasting to reduce major adverse cardiovascular events among aged individuals at high risk of cardiovascular disease. We conclude that despite growing evidence and interest among both the lay and scientific communities in the cardiovascular health-improving effects of intermittent fasting, further research efforts and appropriate caution are warranted before broadly implementing intermittent fasting regimens, especially in the elderly.

Acute nutrient deprivation (fasting) causes an immediate increase in spermidine biosynthesis in yeast, flies, mice and humans, as corroborated in four independent clinical studies. This fasting-induced surge in spermidine constitutes the critical first step of a phylogenetically conserved biochemical cascade that leads to spermidine-dependent hypusination of EIF5A (eukaryotic translation initiation factor 5A), which favors the translation of the pro-macroautophagic/autophagic TFEB (transcription factor EB), and hence an increase in autophagic flux. We observed that genetic or pharmacological inhibition of the spermidine increase by inhibition of ODC1 (ornithine decarboxylase 1) prevents the pro-autophagic and antiaging effects of fasting in yeast, nematodes, flies and mice. Moreover, knockout or knockdown of the enzymes required for EIF5A hypusination abolish fasting-mediated autophagy enhancement and longevity extension in these organisms. Of note, autophagy and longevity induced by rapamycin obey the same rule, meaning that they are tied to an increase in spermidine synthesis. These findings indicate that spermidine is not only a "caloric restriction mimetic" in the sense that its supplementation mimics the beneficial effects of nutrient deprivation on organismal health but that it is also an obligatory downstream effector of the antiaging effects of fasting and rapamycin.

AbstractAimsZSF1 obese rats harbouring two mutant leptin receptor alleles (Leprcp and Leprfa) develop metabolic syndrome and heart failure with preserved ejection fraction (HFpEF), making them a widely used animal model in cardiometabolic research. Studies using ZSF1 rats have contributed significantly to the elucidation of pathophysiological mechanisms underlying HFpEF and therapeutic strategies against this multi‐organ syndrome. In contrast, hybrid, lean ZSF1 rats (L‐ZSF1) do not develop HFpEF and generally serve as controls, disregarding the possibility that the presence of one mutant Lepr allele might affect left ventricular ejection fraction (LVEF), diastolic dysfunction and other relevant HFpEF parameters, such as N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) levels and cardiac inflammation, which could increase during disease manifestation.Methods and ResultsWe collected specimens and echocardiography data of male and female L‐ZSF1 rats (n = 165; ZSF1‐LeprfaLeprcp/Crl) at the age of 6–32 weeks from four independent research groups and performed genotyping as well as the genotype–phenotype analyses. The genotype distribution within L‐ZSF1 was in line with the Hardy–Weinberg equilibrium. Genotypes were not associated with CD68 counts (n = 52, P = 0.886), E/e′ ratio (n = 125, P > 0.250) and NT‐proBNP (n = 126, P = 0.874). LVEF significantly decreased from 25 weeks of age (P = 0.021) but was independent of the genotype (P = 0.768 at <25 weeks of age and P = 0.069 at ≥25 weeks of age, n = 128).ConclusionsIn conclusion, validation of the genotype distribution in L‐ZSF1 rats revealed no associations between the genotype and HFpEF‐relevant measures, namely, NT‐proBNP, CD68 count, LVEF or E/e′.