Nicotinamide for the treatment of heart failure with preserved ejection fraction

Identification of ageing-associated gene signatures in heart failure with preserved ejection fraction by integrated bioinformatics analysis and machine learning

The incidence of heart failure with preserved ejection fraction (HFpEF) increases with the ageing of populations. This study aimed to explore ageing-associated gene signatures in HFpEF to develop new diagnostic biomarkers and provide new insights into the underlying mechanisms of HFpEF. Mice were subjected to a high-fat diet combined with L-NG-nitroarginine methyl ester (l-NAME) to induce HFpEF, and next-generation sequencing was performed with HFpEF hearts. Additionally, separate datasets were acquired from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were used to identify ageing-related DEGs. Support vector machine, random forest, and least absolute shrinkage and selection operator algorithms were employed to identify potential diagnostic genes from ageing-related DEGs. The diagnostic value was assessed using a nomogram and receiver operating characteristic curve. The gene and related protein expression were verified by reverse transcription PCR and western blotting. The immune cell infiltration in hearts was analysed using the single-sample gene-set enrichment analysis algorithm. The results showed that the merged HFpEF datasets comprised 103 genes, of which 15 ageing-related DEGs were further screened in. The ageing-related DEGs were primarily associated with immune and metabolism regulation. AGTR1a, NR3C1, and PRKAB1 were selected for nomogram construction and machine learning-based diagnostic value, displaying strong diagnostic potential. Additionally, ageing scores were established based on nine key DEGs, revealing noteworthy differences in immune cell infiltration across HFpEF subtypes. In summary, those results highlight the significance of immune dysfunction in HFpEF. Furthermore, ageing-related DEGs might serve as promising prognostic and predictive biomarkers for HFpEF.

The Heart Has Intrinsic Ketogenic Capacity that Mediates NAD+ Therapy in HFpEF

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) has overtaken heart failure with reduced ejection fraction as the leading type of heart failure globally and is marked by high morbidity and mortality rates, yet with only a single approved pharmacotherapy: SGLT2i (sodium-glucose co-transporter 2 inhibitor). A prevailing theory for the mechanism underlying SGLT2i is nutrient deprivation signaling, of which ketogenesis is a hallmark. However, it is unclear whether the canonical ketogenic enzyme, HMGCS2 (3-hydroxy-3-methylglutaryl-coenzyme A synthase 2), plays any cardiac role in HFpEF pathogenesis or therapeutic response.

METHODS

We used human myocardium, human HFpEF and heart failure with reduced ejection fraction transcardiac blood sampling, an established murine model of HFpEF, ex vivo Langendorff perfusion, stable isotope tracing in isolated cardiomyocytes, targeted metabolomics, proteomics, lipidomics, and a novel cardiomyocyte-specific conditional HMGCS2-deficient model that we generated.

RESULTS

We demonstrate, for the first time, the intrinsic capacity of the human heart to produce ketones via HMGCS2. We found that increased acetylation of HMGCS2 led to a decrease in the enzyme's specific activity. However, this was overcome by an increase in the steady-state levels of protein. Oxidized form of nicotinamide adenine dinucleotide repletion restored HMGCS2 function via deacetylation, increased fatty acid oxidation, and rescued cardiac function in HFpEF. Critically, using a conditional, cardiomyocyte-specific HMGCS2 knockdown murine model, we revealed that the oxidized form of nicotinamide adenine dinucleotide is unable to rescue HFpEF in the absence of cardiomyocyte HMGCS2.

CONCLUSIONS

The canonical ketogenic enzyme, HMGCS2, mediates the therapeutic effects of the oxidized form of nicotinamide adenine dinucleotide repletion in HFpEF by restoring normal lipid metabolism and mitochondrial function.

The Role of NAD+ Metabolism in Cardiovascular Diseases: Mechanisms and Prospects

Nicotinamide adenine dinucleotide (NAD+) is a promising anti-aging molecule that plays a role in cellular energy metabolism and maintains redox homeostasis. Additionally, NAD+ is involved in regulating deacetylases, DNA repair enzymes, inflammation, and epigenetics, making it indispensable in maintaining the basic functions of cells. Research on NAD+ has become a hotspot, particularly regarding its potential in cardiovascular disease (CVD). Many studies have demonstrated that NAD+ plays a crucial role in the occurrence and development of CVD. This review summarizes the biosynthesis and consumption of NAD+, along with its precursors and their effects on raising NAD+ levels. We also discuss new mechanisms of NAD+ regulation in cardiovascular risk factors and its effects of NAD+ on atherosclerosis, aortic aneurysm, heart failure, hypertension, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and dilated cardiomyopathy, elucidating different mechanisms and potential treatments. NAD+-centered therapy holds promising advantages and prospects in the field of CVD.

Longevity mechanisms in cardiac aging: exploring calcium dysregulation and senescence

Cardiac aging is a multistep process that results in a loss of various structural and functional heart abilities, increasing the risk of heart disease. Since its remarkable discovery in the early 1800s, when limestone is heated, calcium's importance has been defined in numerous ways. It can help stiffen shells and bones, function as a reducing agent in chemical reactions, and play a central role in cellular signalling. The movement of calcium ions in and out of cells and between those is referred to as calcium signalling. It influences the binding of the ligand, enzyme activity, electrochemical gradients, and other cellular processes. Calcium signalling is critical for both contraction and relaxation under the sliding filament model of heart muscle. However, with age, the heart undergoes changes that lead to increases in cardiac dysfunction, such as myocardial fibrosis, decreased cardiomyocyte function, and noxious disturbances in calcium homeostasis. Additionally, when cardiac tissues age, cellular senescence, a state of irreversible cell cycle arrest, accumulates and begins to exacerbate tissue inflammation and fibrosis. This review explores the most recent discoveries regarding the role of senescent cell accumulation and calcium signalling perturbances in cardiac aging. Additionally, new treatment strategies are used to reduce aged-related heart dysfunction by targeting senescent cells and modulating calcium homeostasis.

Obesity accelerates cardiovascular ageing

A global obesity pandemic, coupled with an increasingly ageing population, is exacerbating the burden of cardiovascular disease. Indeed, clinical and experimental evidence underscores a potential connection between obesity and ageing in the pathogenesis of various cardiovascular disorders. This is further supported by the notion that weight reduction not only effectively reduces major cardiovascular events in elderly individuals but is also considered the gold standard for lifespan extension, in obese and non-obese model organisms. This review evaluates the intricate interplay between obesity and ageing from molecular mechanisms to whole organ function within the cardiovascular system. By comparatively analysing their characteristic features, shared molecular and cell biological signatures between obesity and ageing are unveiled, with the intent to shed light on how obesity accelerates cardiovascular ageing. This review also elaborates on how emerging metabolic interventions targeting obesity might protect from cardiovascular diseases largely through antagonizing key molecular mechanisms of the ageing process itself. In sum, this review aims to provide valuable insight into how understanding these interconnected processes could guide the development of novel and effective cardiovascular therapeutics for a growing aged population with a concerning obesity problem.

Metabolic rewiring and inter-organ crosstalk in diabetic HFpEF

Heart failure with preserved ejection fraction (HFpEF) represents a significant and growing clinical challenge. Initially, for an extended period, HFpEF was simply considered as a subset of heart failure, manifesting as haemodynamic disorders such as hypertension, myocardial hypertrophy, and diastolic dysfunction. However, the rising prevalence of obesity and diabetes has reshaped the HFpEF phenotype, with nearly 45% of cases coexisting with diabetes. Currently, it is recognized as a multi-system disorder that involves the heart, liver, kidneys, skeletal muscle, adipose tissue, along with immune and inflammatory signaling pathways. In this review, we summarize the landscape of metabolic rewiring and the crosstalk between the heart and other organs/systems (e.g., adipose, gut, liver and hematopoiesis system) in diabetic HFpEF for the first instance. A diverse array of metabolites and cytokines play pivotal roles in this intricate crosstalk process, with metabolic rewiring, chronic inflammatory responses, immune dysregulation, endothelial dysfunction, and myocardial fibrosis identified as the central mechanisms at the heart of this complex interplay. The liver-heart axis links nonalcoholic steatohepatitis and HFpEF through shared lipid accumulation, inflammation, and fibrosis pathways, while the gut-heart axis involves dysbiosis-driven metabolites (e.g., trimethylamine N-oxide, indole-3-propionic acid and short-chain fatty acids) impacting cardiac function and inflammation. Adipose-heart crosstalk highlights epicardial adipose tissue as a source of local inflammation and mechanical stress, whereas the hematopoietic system contributes via immune cell activation and cytokine release. We contend that, based on the viewpoints expounded in this review, breaking this inter-organ/system vicious cycle is the linchpin of treating diabetic HFpEF.

Lean ZSF1 rats in basic research on heart failure with preserved ejection fraction

AIMS

ZSF1 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 RESULTS

We 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).

CONCLUSIONS

In 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'.

Pathophysiological insights into HFpEF from studies of human cardiac tissue

Heart failure with preserved ejection fraction (HFpEF) is a major, worldwide health-care problem. Few therapies for HFpEF exist because the pathophysiology of this condition is poorly defined and, increasingly, postulated to be diverse. Although perturbations in other organs contribute to the clinical profile in HFpEF, altered cardiac structure, function or both are the primary causes of this heart failure syndrome. Therefore, studying myocardial tissue is fundamental to improve pathophysiological insights and therapeutic discovery in HFpEF. Most studies of myocardial changes in HFpEF have relied on cardiac tissue from animal models without (or with limited) confirmatory studies in human cardiac tissue. Animal models of HFpEF have evolved based on theoretical HFpEF aetiologies, but these models might not reflect the complex pathophysiology of human HFpEF. The focus of this Review is the pathophysiological insights gained from studies of human HFpEF myocardium. We outline the rationale for these studies, the challenges and opportunities in obtaining myocardial tissue from patients with HFpEF and relevant comparator groups, the analytical approaches, the pathophysiological insights gained to date and the remaining knowledge gaps. Our objective is to provide a roadmap for future studies of cardiac tissue from diverse cohorts of patients with HFpEF, coupling discovery biology with measures to account for pathophysiological diversity.

Contributions of Inflammation to Cardiometabolic Heart Failure with Preserved Ejection Fraction

The most common form of heart failure is heart failure with preserved ejection fraction (HFpEF). While heterogeneous in origin, the most common form of HFpEF is the cardiometabolic manifestation. Obesity and aging promote systemic inflammation that appears integral to cardiometabolic HFpEF pathophysiology. Accumulation of immune cells within the heart, fueled by an altered metabolome, contribute to cardiac inflammation and fibrosis. In spite of this, broad anti-inflammatory therapy has not shown significant benefit in patient outcomes. Thus, understanding of the nuances to metabolic and age-related inflammation during HFpEF is paramount for more targeted interventions. Here, we review clinical evidence of inflammation in the context of HFpEF and summarize our mechanistic understanding of immunometabolic inflammation, highlighting pathways of therapeutic potential along the way.

Leveraging metabolism for better outcomes in heart failure

Whilst metabolic inflexibility and substrate constraint have been observed in heart failure for many years, their exact causal role remains controversial. In parallel, many of our fundamental assumptions about cardiac fuel use are now being challenged like never before. For example, the emergence of sodium-glucose cotransporter 2 inhibitor therapy as one of the four 'pillars' of heart failure therapy is causing a revisit of metabolism as a key mechanism and therapeutic target in heart failure. Improvements in the field of cardiac metabolomics will lead to a far more granular understanding of the mechanisms underpinning normal and abnormal human cardiac fuel use, an appreciation of drug action, and novel therapeutic strategies. Technological advances and expanding biorepositories offer exciting opportunities to elucidate the novel aspects of these metabolic mechanisms. Methodologic advances include comprehensive and accurate substrate quantitation such as metabolomics and stable-isotope fluxomics, improved access to arterio-venous blood samples across the heart to determine fuel consumption and energy conversion, high quality cardiac tissue biopsies, biochemical analytics, and informatics. Pairing these technologies with recent discoveries in epigenetic regulation, mitochondrial dynamics, and organ-microbiome metabolic crosstalk will garner critical mechanistic insights in heart failure. In this state-of-the-art review, we focus on new metabolic insights, with an eye on emerging metabolic strategies for heart failure. Our synthesis of the field will be valuable for a diverse audience with an interest in cardiac metabolism.

Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease

Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction, and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Male mice fed a high fat/sugar diet (HFSD vs. control) exhibited diastolic dysfunction (echo E/e' Doppler ratio). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. E/e' for the HFSD hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from the non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs. control). With stretch, the Ca2+ transient decay time course was prolonged. With increased pacing, cardiomyocyte stiffness was elevated, yet diastolic Ca2+ elevation was attenuated. Our findings show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from cardiomyocyte stiffness. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca2+ interaction contributes to intrinsic cardiomyocyte stiffness in cardiometabolic disease. KEY POINTS: Understanding cardiomyocyte stiffness components is an important priority for identifying new therapeutics for diastolic dysfunction, a key feature of cardiometabolic disease. In this study cardiac function was measured in vivo (echocardiography) for mice fed a high-fat/sugar diet (HFSD, ≥25 weeks). Performance of intact isolated cardiomyocytes derived from the same hearts was measured during pacing under non-loaded, loaded and stretched conditions in vitro. Calibrated cardiomyocyte stretches demonstrated that stiffness (stress/strain) was elevated in HFSD cardiomyocytes in vitro and correlated with diastolic dysfunction (E/e') in vivo. HFSD cardiomyocyte Ca2+ transient decay was prolonged in response to stretch. Stiffness was accentuated with pacing increase while the elevation in diastolic Ca2+ was attenuated. Data show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. These findings suggest that stretch-dependent augmentation of the myofilament-Ca2+ response during diastole partially underlies elevated cardiomyocyte stiffness and diastolic dysfunction of hearts of animals with cardiometabolic disease.

Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease

Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction, and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Male mice fed a high fat/sugar diet (HFSD vs control) exhibited diastolic dysfunction (echo E/e' doppler ratio). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. E/e' for the origin hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs control). With stretch, the Ca2+ transient decay time course was prolonged. With increased pacing, cardiomyocyte stiffness was elevated, yet diastolic Ca2+ elevation was attenuated. Our findings show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from cardiomyocyte stiffness. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca2+ interaction contributes to intrinsic cardiomyocyte stiffness in cardiometabolic disease.

Self-Assembly Hypoxic and ROS Dual Response Nano Prodrug as a New Therapeutic Approach for Glaucoma Treatments

Glaucoma is an irreversible blinding eye disease characterized by retinal ganglion cell (RGC) death.Previous studies have demonstrated that protecting mitochondria and activating the CaMKII/CREB signaling pathway can effectively protect RGC and axon. However, currently treatments are often unsatisfactory, and the pathogenesis of glaucoma requires further elucidation. In this study, a ROS-responsive dual drug conjugate (OLN monomer) is first designed that simultaneously bonds nicotinamide and oleic acid. The conjugate self-assembled into nanoparticles (uhOLN-NPs) through the aggregation of multiple micelles and possesses ROS scavenging capability. Then, a polymer with a hypoxic response function is designed, which encapsulates uhOLN-NPs to form nanoparticles with hypoxic and ROS responses (HOLN-NPs). Under hypoxia in RGCs, the azo bond of HOLN-NPs breaks and releases uhOLN-NPs. Meanwhile, under high ROS conditions, the thioketone bond broke, leading to the dissociation of nano-prodrug. The released nicotinamide and oleic acid co-scavenge ROS and activate the CaMKII/CREB pathway, protecting mitochondria in RGCs. HOLN-NPs exhibit a significantly superior protective effect on R28 cells in glutamate models of glaucoma. The accumulation of HOLN-NPs in retinal RGCs lead to significant inhibition of RGC apoptosis and axonal damage in vivo. Notably, HOLN-NPs provide a new therapeutic approach for patients with neurodegenerative disease.

Effects of Supplementation with NAD + Precursors on Metabolic Syndrome Parameters: A Systematic Review and Meta-Analysis

Intracellular levels of NAD +  regulate metabolism, among other ways, through enzymes that use NAD +  as a substrate, capable of inducing catabolic processes, such as lipid oxidation, glucose uptake, and mitochondrial activity. In several model organisms, administering precursor compounds for NAD + synthesis increases its levels, improves lipid and glucose homeostasis, and reduces weight gain. However, evidence of the effects of these precursors on human patients needs to be better evaluated. Therefore, we carried out a systematic review and meta-analysis of randomized clinical trials that assessed the effects of NAD +  precursors on Metabolic Syndrome parameters in humans. We based our methods on PRISMA 2020. Our search retrieved 429 articles, and 19 randomized controlled trials were included in the meta-analysis. We assessed the risk of bias with the Rob 2 algorithm and summarized the quality of evidence with the GRADE algorithm. Supplementation with NAD +  precursors reduced plasma levels of total cholesterol and triglycerides in volunteers, but the intervention did not significantly affect the other outcomes analyzed. Three of the included articles presented a high risk of bias. The quality of evidence varied between very low and low due to the risk of bias, imprecision, and indirectness. The number of participants in outcomes other than lipidemia is still generally tiny; therefore, more clinical trials evaluating these parameters will increase the quality of the evidence. On the other hand, quality randomized studies are essential to assess better the effects of NAD +  precursors on lipidemia.

Blunted Cardiac Mitophagy in Response to Metabolic Stress Contributes to HFpEF

BACKGROUND

Metabolic remodeling and mitochondrial dysfunction are hallmarks of heart failure with reduced ejection fraction. However, their role in the pathogenesis of HF with preserved ejection fraction (HFpEF) is poorly understood.

METHODS

In a mouse model of HFpEF, induced by high-fat diet and Nω-nitrol-arginine methyl ester, cardiac energetics was measured by 31P nuclear magnetic resonance (NMR) spectroscopy and substrate oxidation profile was assessed by 13C-isotopmer analysis. Mitochondrial functions were assessed in the heart tissue and human induced pluripotent stem cell-derived cardiomyocytes.

RESULTS

HFpEF hearts presented a lower phosphocreatine content and a reduced phosphocreatine/ATP ratio, similar to that in heart failure with reduced ejection fraction. Decreased respiratory function and increased reactive oxygen species production were observed in mitochondria isolated from HFpEF hearts suggesting mitochondrial dysfunction. Cardiac substrate oxidation profile showed a high dependency on fatty acid oxidation in HFpEF hearts, which is the opposite of heart failure with reduced ejection fraction but similar to that in high-fat diet hearts. However, phosphocreatine/ATP ratio and mitochondrial function were sustained in the high-fat diet hearts. We found that mitophagy was activated in the high-fat diet heart but not in HFpEF hearts despite similar extent of obesity suggesting that mitochondrial quality control response was impaired in HFpEF hearts. Using a human induced pluripotent stem cell-derived cardiomyocyte mitophagy reporter, we found that fatty acid loading stimulated mitophagy, which was obliterated by inhibiting fatty acid oxidation. Enhancing fatty acid oxidation by deleting ACC2 (acetyl-CoA carboxylase 2) in the heart stimulated mitophagy and improved HFpEF phenotypes.

CONCLUSIONS

Maladaptation to metabolic stress in HFpEF hearts impairs mitochondrial quality control and contributed to the pathogenesis, which can be improved by stimulating fatty acid oxidation.

NAD metabolism and heart failure: Mechanisms and therapeutic potentials

Nicotinamide adenine dinucleotide provides the critical redox pair, NAD+ and NADH, for cellular energy metabolism. In addition, NAD+ is the precursor for de novo NADP+ synthesis as well as the co-substrates for CD38, poly(ADP-ribose) polymerase and sirtuins, thus, playing a central role in the regulation of oxidative stress and cell signaling. Declines of the NAD+ level and altered NAD+/NADH redox states have been observed in cardiometabolic diseases of various etiologies. NAD based therapies have emerged as a promising strategy to treat cardiovascular disease. Strategies that reduce NAD+ consumption or promote NAD+ production have repleted intracellular NAD+ or normalized NAD+/NADH redox in preclinical studies. These interventions have shown cardioprotective effects in multiple models suggesting a great promise of the NAD+ elevating therapy. Mechanisms for the benefit of boosting NAD+ level, however, remain incompletely understood. Moreover, despite the robust pre-clinical studies there are still challenges to translate the therapy to clinic. Here, we review the most up to date literature on mechanisms underlying the NAD+ elevating interventions and discuss the progress of human studies. We also aim to provide a better understanding of how NAD metabolism is changed in failing hearts with a particular emphasis on types of strategies employed and methods to target these pathways. Finally, we conclude with a comprehensive assessment of the challenges in developing NAD-based therapies for heart diseases, and to provide a perspective on the future of the targeting strategies.

Cardiac remodeling: novel pathophysiological mechanisms and therapeutic strategies

Morphological and structural remodeling of the heart, including cardiac hypertrophy and fibrosis, has been considered as a therapeutic target for heart failure for approximately three decades. Groundbreaking heart failure medications demonstrating reverse remodeling effects have contributed significantly to medical advancements. However, nearly 50% of heart failure patients still exhibit drug resistance, posing a challenge to the healthcare system. Recently, characteristics of heart failure resistant to ARBs and β-blockers have been defined, highlighting preserved systolic function despite impaired diastolic function, leading to the classification of heart failure with preserved ejection fraction (HFpEF). The pathogenesis and aetiology of HFpEF may be related to metabolic abnormalities, as evidenced by its mimicry through endothelial dysfunction and excessive intake of high-fat diets. Our recent findings indicate a significant involvement of mitochondrial hyper-fission in the progression of heart failure. This mitochondrial pathological remodeling is associated with redox imbalance, especially hydrogen sulphide accumulation due to abnormal electron leak in myocardium. In this review, we also introduce a novel therapeutic strategy for heart failure from the current perspective of mitochondrial redox-metabolic remodeling.

Cellular and extracellular proteomic profiling of paradoxical low-flow low-gradient aortic stenosis myocardium

Aims

Patients with severe aortic stenosis (AS), low transvalvular flow (LF) and low gradient (LG) with normal ejection fraction (EF)-are referred to as paradoxical LF-LG AS (PLF-LG). PLF-LG patients develop more advanced heart failure symptoms and have a worse prognosis than patients with normal EF and high-gradient AS (NEF-HG). Despite its clinical relevance, the mechanisms underlying PLF-LG are still poorly understood.

Methods

Left ventricular (LV) myocardial biopsies of PLF-LG (n = 5) and NEF-HG patients (n = 6), obtained during transcatheter aortic valve implantation, were analyzed by LC-MS/MS after sequential extraction of cellular and extracellular matrix (ECM) proteins using a three-step extraction method. Proteomic data are available via ProteomeXchange with identifier PXD055391.

Results

73 cellular proteins were differentially abundant between the 2 groups. Among these, a network of proteins related to muscle contraction and arrhythmogenic cardiomyopathy (e.g., cTnI, FKBP1A and CACNA2D1) was found in PLF-LG. Extracellularly, upregulated proteins in PLF-LG were related to ATP synthesis and oxidative phosphorylation (e.g., ATP5PF, COX5B and UQCRB). Interestingly, we observed a 1.3-fold increase in cyclophilin A (CyPA), proinflammatory cytokine, in the extracellular extracts of PLF-LG AS patients (p < 0.05). Consistently, immunohistochemical analysis confirmed its extracellular localization in PLF-LG AS LV sections along with an increase in its receptor, CD147, compared to the NEF-HG AS patients. Levels of core ECM proteins, namely collagens and proteoglycans, were comparable between groups.

Conclusion

Our study pinpointed novel candidates and processes with potential relevance in the pathophysiology of PLF-LG. The role of CyPA in particular warrants further investigation.

Insights into the post-translational modifications in heart failure

Heart failure (HF), as the terminal manifestation of multiple cardiovascular diseases, causes a huge socioeconomic burden worldwide. Despite the advances in drugs and medical-assisted devices, the prognosis of HF remains poor. HF is well-accepted as a myriad of subcellular dys-synchrony related to detrimental structural and functional remodelling of cardiac components, including cardiomyocytes, fibroblasts, endothelial cells and macrophages. Through the covalent chemical process, post-translational modifications (PTMs) can coordinate protein functions, such as re-localizing cellular proteins, marking proteins for degradation, inducing interactions with other proteins and tuning enzyme activities, to participate in the progress of HF. Phosphorylation, acetylation, and ubiquitination predominate in the currently reported PTMs. In addition, advanced HF is commonly accompanied by metabolic remodelling including enhanced glycolysis. Thus, glycosylation induced by disturbed energy supply is also important. In this review, firstly, we addressed the main types of HF. Then, considering that PTMs are associated with subcellular locations, we summarized the leading regulation mechanisms in organelles of distinctive cell types of different types of HF, respectively. Subsequently, we outlined the aforementioned four PTMs of key proteins and signaling sites in HF. Finally, we discussed the perspectives of PTMs for potential therapeutic targets in HF.

Effects of Nicotinamide Adenine Dinucleotide on Older Patients with Heart Failure

Background

Heart failure (HF) is the main cause of death in middle-aged and older people and is characterized by high morbidity, high mortality, a high rehospitalization rate, and many high-risk groups. Nicotinamide adenine dinucleotide (NAD+) is widely present in the mitochondria of cardiomyocytes and maintains the redox balance in the body, which can effectively treat HF. We sought to evaluate whether NAD+ therapy has some clinical efficacy in patients with HF.

Methods

Based on using conventional drugs to treat HF, patients (n = 60) were randomized 1:1 to saline and 50 mg NAD+ with 50 mL of normal saline for 7 days. The baseline characteristics of patients before and after treatment and cardiac function (N-terminal pro B-type natriuretic peptide (NT-proBNP) level and left ventricular ejection fraction (LVEF) value) were analyzed. Serological analysis (sirtuin-1 (SIRT1), sirtuin-3 (SIRT3), sirtuin-6 (SIRT6), reactive oxygen species (ROS), and endothelin) was also performed.

Results

Among the 60 patients with HF who were treated with NAD+ for 7 days, the improvement rate in NT-proBNP levels and LVEF values was better than in the saline group, although not statistically significant. These patients were more likely to benefit from NAD+ because of higher levels of anti-oxidative stress (SIRT1, SIRT3, SIRT6, and ROS) and anti-endothelial injury (endothelin) than those in the saline control group.

Conclusions

According to the results of this study, it is believed that 7 days of NAD+ injections has a positive effect on improving cardiac function, oxidative stress, and endothelial injury in patients with HF compared with the saline control.

Clinical Trial Registration

Chinese Clinical Trial Registry (http://www.chictr.org.cn/) ChiCTR2300074326; retrospectively registered on 3 August 2023.

Mitophagy modulation for the treatment of cardiovascular diseases

BACKGROUND

Defects of mitophagy, the selective form of autophagy for mitochondria, are commonly observed in several cardiovascular diseases and represent the main cause of mitochondrial dysfunction. For this reason, mitophagy has emerged as a novel and potential therapeutic target.

METHODS

In this review, we discuss current evidence about the biological significance of mitophagy in relevant preclinical models of cardiac and vascular diseases, such as heart failure, ischemia/reperfusion injury, metabolic cardiomyopathy and atherosclerosis.

RESULTS

Multiple studies have shown that cardiac and vascular mitophagy is an adaptive mechanism in response to stress, contributing to cardiovascular homeostasis. Mitophagy defects lead to cell death, ultimately impairing cardiac and vascular function, whereas restoration of mitophagy by specific compounds delays disease progression.

CONCLUSIONS

Despite previous efforts, the molecular mechanisms underlying mitophagy activation in response to stress are not fully characterized. A comprehensive understanding of different forms of mitophagy active in the cardiovascular system is extremely important for the development of new drugs targeting this process. Human studies evaluating mitophagy abnormalities in patients at high cardiovascular risk also represent a future challenge.

Rejuvenation of the Aging Heart: Molecular Determinants and Applications

In Canada and worldwide, the elderly population (ie, individuals > 65 years of age) is increasing disproportionately relative to the total population. This is expected to have a substantial impact on the health care system, as increased aged is associated with a greater incidence of chronic noncommunicable diseases. Within the elderly population, cardiovascular disease is a leading cause of death, therefore developing therapies that can prevent or slow disease progression in this group is highly desirable. Historically, aging research has focused on the development of anti-aging therapies that are implemented early in life and slow the age-dependent decline in cell and organ function. However, accumulating evidence supports that late-in-life therapies can also benefit the aged cardiovascular system by limiting age-dependent functional decline. Moreover, recent studies have demonstrated that rejuvenation (ie, reverting cellular function to that of a younger phenotype) of the already aged cardiovascular system is possible, opening new avenues to develop therapies for older individuals. In this review, we first provide an overview of the functional changes that occur in the cardiomyocyte with aging and how this contributes to the age-dependent decline in heart function. We then discuss the various anti-aging and rejuvenation strategies that have been pursued to improve the function of the aged cardiomyocyte, with a focus on therapies implemented late in life. These strategies include 1) established systemic approaches (caloric restriction, exercise), 2) pharmacologic approaches (mTOR, AMPK, SIRT1, and autophagy-targeting molecules), and 3) emerging rejuvenation approaches (partial reprogramming, parabiosis/modulation of circulating factors, targeting endogenous stem cell populations, and senotherapeutics). Collectively, these studies demonstrate the exciting potential and limitations of current rejuvenation strategies and highlight future areas of investigation that will contribute to the development of rejuvenation therapies for the aged heart.

The role of oxidative stress in aortic dissection: a potential therapeutic target

The incidence of aortic dissection (AD) is steadily increasing, driven by the rising prevalence of chronic conditions such as hypertension and the global aging of the population. Oxidative stress emerges as a pivotal pathophysiological mechanism contributing to the progression of AD. Oxidative stress triggers apoptosis in vascular smooth muscle cells, reshapes the extracellular matrix (ECM), and governs ECM degradation and remodeling, subsequently impacting aortic compliance. Furthermore, oxidative stress not only facilitates the infiltration of macrophages and mononuclear lymphocytes but also disrupts the integral structure and functionality of endothelial cells, thereby inducing endothelial cell dysfunction and furthering the degeneration of the middle layer of the aortic wall. Investigating antioxidants holds promise as a therapeutic avenue for addressing AD.

Mechanisms of myocardial reverse remodelling and its clinical significance: A scientific statement of the ESC Working Group on Myocardial Function

Cardiovascular disease (CVD) is the leading cause of morbimortality in Europe and worldwide. CVD imposes a heterogeneous spectrum of cardiac remodelling, depending on the insult nature, that is, pressure or volume overload, ischaemia, arrhythmias, infection, pathogenic gene variant, or cardiotoxicity. Moreover, the progression of CVD-induced remodelling is influenced by sex, age, genetic background and comorbidities, impacting patients' outcomes and prognosis. Cardiac reverse remodelling (RR) is defined as any normative improvement in cardiac geometry and function, driven by therapeutic interventions and rarely occurring spontaneously. While RR is the outcome desired for most CVD treatments, they often only slow/halt its progression or modify risk factors, calling for novel and more timely RR approaches. Interventions triggering RR depend on the myocardial insult and include drugs (renin-angiotensin-aldosterone system inhibitors, beta-blockers, diuretics and sodium-glucose cotransporter 2 inhibitors), devices (cardiac resynchronization therapy, ventricular assist devices), surgeries (valve replacement, coronary artery bypass graft), or physiological responses (deconditioning, postpartum). Subsequently, cardiac RR is inferred from the degree of normalization of left ventricular mass, ejection fraction and end-diastolic/end-systolic volumes, whose extent often correlates with patients' prognosis. However, strategies aimed at achieving sustained cardiac improvement, predictive models assessing the extent of RR, or even clinical endpoints that allow for distinguishing complete from incomplete RR or adverse remodelling objectively, remain limited and controversial. This scientific statement aims to define RR, clarify its underlying (patho)physiologic mechanisms and address (non)pharmacological options and promising strategies to promote RR, focusing on the left heart. We highlight the predictors of the extent of RR and review the prognostic significance/impact of incomplete RR/adverse remodelling. Lastly, we present an overview of RR animal models and potential future strategies under pre-clinical evaluation.

Combining the Strengths of the Explainable Boosting Machine and Metabolomics Approaches for Biomarker Discovery in Acute Myocardial Infarction

Acute Myocardial Infarction (AMI), a common disease that can have serious consequences, occurs when myocardial blood flow stops due to occlusion of the coronary artery. Early and accurate prediction of AMI is critical for rapid prognosis and improved patient outcomes. Metabolomics, the study of small molecules within biological systems, is an effective tool used to discover biomarkers associated with many diseases. This study intended to construct a predictive model for AMI utilizing metabolomics data and an explainable machine learning approach called Explainable Boosting Machines (EBM). The EBM model was trained on a dataset of 102 prognostic metabolites gathered from 99 individuals, including 34 healthy controls and 65 AMI patients. After a comprehensive data preprocessing, 21 metabolites were determined as the candidate predictors to predict AMI. The EBM model displayed satisfactory performance in predicting AMI, with various classification performance metrics. The model's predictions were based on the combined effects of individual metabolites and their interactions. In this context, the results obtained in two different EBM modeling, including both only individual metabolite features and their interaction effects, were discussed. The most important predictors included creatinine, nicotinamide, and isocitrate. These metabolites are involved in different biological activities, such as energy metabolism, DNA repair, and cellular signaling. The results demonstrate the potential of the combination of metabolomics and the EBM model in constructing reliable and interpretable prediction outputs for AMI. The discussed metabolite biomarkers may assist in early diagnosis, risk assessment, and personalized treatment methods for AMI patients. This study successfully developed a pipeline incorporating extensive data preprocessing and the EBM model to identify potential metabolite biomarkers for predicting AMI. The EBM model, with its ability to incorporate interaction terms, demonstrated satisfactory classification performance and revealed significant metabolite interactions that could be valuable in assessing AMI risk. However, the results obtained from this study should be validated with studies to be carried out in larger and well-defined samples.

Integration mapping of cardiac fibroblast single-cell transcriptomes elucidates cellular principles of fibrosis in diverse pathologies

Single-cell technology has allowed researchers to probe tissue complexity and dynamics at unprecedented depth in health and disease. However, the generation of high-dimensionality single-cell atlases and virtual three-dimensional tissues requires integrated reference maps that harmonize disparate experimental designs, analytical pipelines, and taxonomies. Here, we present a comprehensive single-cell transcriptome integration map of cardiac fibrosis, which underpins pathophysiology in most cardiovascular diseases. Our findings reveal similarity between cardiac fibroblast (CF) identities and dynamics in ischemic versus pressure overload models of cardiomyopathy. We also describe timelines for commitment of activated CFs to proliferation and myofibrogenesis, profibrotic and antifibrotic polarization of myofibroblasts and matrifibrocytes, and CF conservation across mouse and human healthy and diseased hearts. These insights have the potential to inform knowledge-based therapies.

The Efficacy of Risk Factor Modification Compared to NAD+ Repletion in Diastolic Heart Failure

Heart failure (HF) with left ventricular diastolic dysfunction is a growing global concern. This study evaluated myocardial oxidized nicotinamide adenine dinucleotide (NAD+) levels in human systolic and diastolic HF and in a murine model of HF with preserved ejection fraction, exploring NAD+ repletion as therapy. We quantified myocardial NAD+ and nicotinamide phosphoribosyltransferase levels, assessing restoration with nicotinamide riboside (NR). Findings show significant NAD+ and nicotinamide phosphoribosyltransferase depletion in human diastolic HF myocardium, but NR successfully restored NAD+ levels. In murine HF with preserved ejection fraction, NR as preventive and therapeutic intervention improved metabolic and antioxidant profiles. This study underscores NAD+ repletion's potential in diastolic HF management.

Postmortem metabolomics as a high-throughput cause-of-death screening tool for human death investigations

Autopsy rates are declining globally, impacting cause-of-death (CoD) diagnoses and quality control. Postmortem metabolomics was evaluated for CoD screening using 4,282 human cases, encompassing CoD groups: acidosis, drug intoxication, hanging, ischemic heart disease (IHD), and pneumonia. Cases were split 3:1 into training and test sets. High-resolution mass spectrometry data from femoral blood were analyzed via orthogonal-partial least squares discriminant analysis (OPLS-DA) to discriminate CoD groups. OPLS-DA achieved an R2 = 0.52 and Q2 = 0.30, with true-positive prediction rates of 68% and 65% for training and test sets, respectively, across all groups. Specificity-optimized thresholds predicted 56% of test cases with a unique CoD, average 45% sensitivity, and average 96% specificity. Prediction accuracies varied: 98.7% for acidosis, 80.5% for drug intoxication, 81.6% for hanging, 73.1% for IHD, and 93.6% for pneumonia. This study demonstrates the potential of large-scale postmortem metabolomics for CoD screening, offering high specificity and enhancing throughput and decision-making in human death investigations.

Mitochondrial Dysfunction: A Roadmap for Understanding and Tackling Cardiovascular Aging

Cardiovascular aging is a progressive remodeling process constituting a variety of cellular and molecular alterations that are closely linked to mitochondrial dysfunction. Therefore, gaining a deeper understanding of the changes in mitochondrial function during cardiovascular aging is crucial for preventing cardiovascular diseases. Cardiac aging is accompanied by fibrosis, cardiomyocyte hypertrophy, metabolic changes, and infiltration of immune cells, collectively contributing to the overall remodeling of the heart. Similarly, during vascular aging, there is a profound remodeling of blood vessel structure. These remodeling present damage to endothelial cells, increased vascular stiffness, impaired formation of new blood vessels (angiogenesis), the development of arteriosclerosis, and chronic vascular inflammation. This review underscores the role of mitochondrial dysfunction in cardiac aging, exploring its impact on fibrosis and myocardial alterations, metabolic remodeling, immune response remodeling, as well as in vascular aging in the heart. Additionally, we emphasize the significance of mitochondria-targeted therapies in preventing cardiovascular diseases in the elderly.

Aging in Heart Failure: Embracing Biology Over Chronology: JACC Family Series

Age is among the most potent risk factors for developing heart failure and is strongly associated with adverse outcomes. As the global population continues to age and the prevalence of heart failure rises, understanding the role of aging in the development and progression of this chronic disease is essential. Although chronologic age is on a fixed course, biological aging is more variable and potentially modifiable in patients with heart failure. This review describes the current knowledge on mechanisms of biological aging that contribute to the pathogenesis of heart failure. The discussion focuses on 3 hallmarks of aging-impaired proteostasis, mitochondrial dysfunction, and deregulated nutrient sensing-that are currently being targeted in therapeutic development for older adults with heart failure. In assessing existing and emerging therapeutic strategies, the review also enumerates the importance of incorporating geriatric conditions into the management of older adults with heart failure and in ongoing clinical trials.

Titin: roles in cardiac function and diseases

The giant protein titin is an essential component of muscle sarcomeres. A single titin molecule spans half a sarcomere and mediates diverse functions along its length by virtue of its unique domains. The A-band of titin functions as a molecular blueprint that defines the length of the thick filaments, the I-band constitutes a molecular spring that determines cell-based passive stiffness, and various domains, including the Z-disk, I-band, and M-line, serve as scaffolds for stretch-sensing signaling pathways that mediate mechanotransduction. This review aims to discuss recent insights into titin's functional roles and their relationship to cardiac function. The role of titin in heart diseases, such as dilated cardiomyopathy and heart failure with preserved ejection fraction, as well as its potential as a therapeutic target, is also discussed.

The therapeutic perspective of NAD+ precursors in age-related diseases

Nicotinamide adenine dinucleotide (NAD+) is the fundamental molecule that performs numerous biological reactions and is crucial for maintaining cellular homeostasis. Studies have found that NAD+ decreases with age in certain tissues, and age-related NAD+ depletion affects physiological functions and contributes to various aging-related diseases. Supplementation of NAD+ precursor significantly elevates NAD+ levels in murine tissues, effectively mitigates metabolic syndrome, enhances cardiovascular health, protects against neurodegeneration, and boosts muscular strength. Despite the versatile therapeutic functions of NAD+ in animal studies, the efficacy of NAD+ precursors in clinical studies have been limited compared with that in the pre-clinical study. Clinical studies have demonstrated that NAD+ precursor treatment efficiently increases NAD+ levels in various tissues, though their clinical proficiency is insufficient to ameliorate the diseases. However, the latest studies regarding NAD+ precursors and their metabolism highlight the significant role of gut microbiota. The studies found that orally administered NAD+ intermediates interact with the gut microbiome. These findings provide compelling evidence for future trials to further explore the involvement of gut microbiota in NAD+ metabolism. Also, the reduced form of NAD+ precursor shows their potential to raise NAD+, though preclinical studies have yet to discover their efficacy. This review sheds light on NAD+ therapeutic efficiency in preclinical and clinical studies and the effect of the gut microbiota on NAD+ metabolism.

Metabolic control of mitophagy

Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.

Palmitoleic Acid Ameliorates Metabolic Disorders and Inflammation by Modulating Gut Microbiota and Serum Metabolites

SCOPE

Palmitoleic acid (POA) is an omega-7 monounsaturated fatty acid that has been suggested to improve metabolic disorders. However, it remains unclear whether gut microbiota plays a role in the amelioration of metabolic disorders by POA. This study aims to investigate the regulation of POA on metabolism, as well as systemic inflammation in HFD-fed mice from the perspective of serum metabolome and gut microbiome.

METHODS AND RESULTS

Thirty-six C57BL/6 male mice are randomly assigned to either a normal chow diet containing 1.9% w/w lard or an HFD containing 20.68% w/w lard or 20.68% w/w sea buckthorn pulp oil for 16 weeks. The study finds that POA significantly attenuated hyperlipidemia, insulin resistance, and inflammation in HFD-fed mice. POA supplementation significantly alters the composition of serum metabolites, particularly lipid metabolites in the glycerophospholipid metabolism pathway. POA obviously increases the abundance of Bifidobacterium and decreases the abundance of Allobaculum. Importantly, the study finds that glycerophosphocholine mediates the effect of Bifidobacterium on LDL-C, sphingomyelin mediates the effect of Bifidobacterium on IL-6, and maslinic acid mediates the effect of Allobaculum on IL-6.

CONCLUSION

The results suggest that exogenous POA can improve metabolic disorders and inflammation in HFD-fed mice, potentially by modulating the serum metabolome and gut microbiome.

The cardiomyocyte origins of diastolic dysfunction: cellular components of myocardial "stiffness"

The impaired ability of the heart to relax and stretch to accommodate venous return is generally understood to represent a state of "diastolic dysfunction" and often described using the all-purpose noun "stiffness." Despite the now common qualitative usage of this term in fields of cardiac patho/physiology, the specific quantitative concept of stiffness as a molecular and biophysical entity with real practical interpretation in healthy and diseased hearts is sometimes obscure. The focus of this review is to characterize the concept of cardiomyocyte stiffness and to develop interpretation of "stiffness" attributes at the cellular and molecular levels. Here, we consider "stiffness"-related terminology interpretation and make links between cardiomyocyte stiffness and aspects of functional and structural cardiac performance. We discuss cross bridge-derived stiffness sources, considering the contributions of diastolic myofilament activation and impaired relaxation. This includes commentary relating to the role of cardiomyocyte Ca2+ flux and Ca2+ levels in diastole, the troponin-tropomyosin complex role as a Ca2+ effector in diastole, the myosin ADP dissociation rate as a modulator of cross bridge attachment and regulation of cross-bridge attachment by myosin binding protein C. We also discuss non-cross bridge-derived stiffness sources, including the titin sarcomeric spring protein, microtubule and intermediate filaments, and cytoskeletal extracellular matrix interactions. As the prevalence of conditions involving diastolic heart failure has escalated, a more sophisticated understanding of the molecular, cellular, and tissue determinants of cardiomyocyte stiffness offers potential to develop imaging and molecular intervention tools.

NAD in pathological cardiac remodeling: Metabolic regulation and beyond

Nicotinamide adenine dinucleotide (NAD) coenzymes are carriers of high energy electrons in metabolism and also play critical roles in numerous signaling pathways. NAD metabolism is decreased in various cardiovascular diseases. Importantly, stimulation of NAD biosynthesis protects against heart disease under different pathological conditions. In this review, we describe pathways for both generation and catabolism of NAD coenzymes and the respective changes of these pathways in the heart under cardiac diseases, including pressure overload, myocardial infarction, cardiometabolic disease, cancer treatment cardiotoxicity, and heart failure. We next provide an update on the strategies and treatments to increase NAD levels, such as supplementation of NAD precursors, in the heart that prevent or reverse cardiomyopathy. We also introduce the approaches to manipulate NAD consumption enzymes to ameliorate cardiac disease. Finally, we discuss the mechanisms associated with improvements in cardiac function by NAD coenzymes, differentiating between mitochondria-dependent effects and those independent of mitochondrial metabolism.

MiR-203 improves cardiac dysfunction by targeting PARP1-NAD+ axis in aging murine

Heart aging is a prevalent cause of cardiovascular diseases among the elderly. NAD+ depletion is a hallmark feature of aging heart, however, the molecular mechanisms that affect NAD+ depletion remain unclear. In this study, we identified microRNA-203 (miR-203) as a senescence-associated microRNA that regulates NAD+ homeostasis. We found that the blood miR-203 level negatively correlated with human age and its expression significantly decreased in the hearts of aged mice and senescent cardiomyocytes. Transgenic mice with overexpressed miR-203 (TgN (miR-203)) showed resistance to aging-induced cardiac diastolic dysfunction, cardiac remodeling, and myocardial senescence. At the cellular level, overexpression of miR-203 significantly prevented D-gal-induced cardiomyocyte senescence and mitochondrial damage, while miR-203 knockdown aggravated these effects. Mechanistically, miR-203 inhibited PARP1 expression by targeting its 3'UTR, which helped to reduce NAD+ depletion and improve mitochondrial function and cell senescence. Overall, our study first identified miR-203 as a genetic tool for anti-heart aging by restoring NAD+ function in cardiomyocytes.

Targeting HDAC6 to treat heart failure with preserved ejection fraction in mice

Heart failure with preserved ejection fraction (HFpEF) poses therapeutic challenges due to the limited treatment options. Building upon our previous research that demonstrates the efficacy of histone deacetylase 6 (HDAC6) inhibition in a genetic cardiomyopathy model, we investigate HDAC6's role in HFpEF due to their shared mechanisms of inflammation and metabolism. Here, we show that inhibiting HDAC6 with TYA-018 effectively reverses established heart failure and its associated symptoms in male HFpEF mouse models. Additionally, in male mice lacking Hdac6 gene, HFpEF progression is delayed and they are resistant to TYA-018's effects. The efficacy of TYA-018 is comparable to a sodium-glucose cotransporter 2 (SGLT2) inhibitor, and the combination shows enhanced effects. Mechanistically, TYA-018 restores gene expression related to hypertrophy, fibrosis, and mitochondrial energy production in HFpEF heart tissues. Furthermore, TYA-018 also inhibits activation of human cardiac fibroblasts and enhances mitochondrial respiratory capacity in cardiomyocytes. In this work, our findings show that HDAC6 impacts on heart pathophysiology and is a promising target for HFpEF treatment.

Influence of microbiota-associated metabolic reprogramming on clinical outcome in patients with melanoma from the randomized adjuvant dendritic cell-based MIND-DC trial

Tumor immunosurveillance plays a major role in melanoma, prompting the development of immunotherapy strategies. The gut microbiota composition, influencing peripheral and tumoral immune tonus, earned its credentials among predictors of survival in melanoma. The MIND-DC phase III trial (NCT02993315) randomized (2:1 ratio) 148 patients with stage IIIB/C melanoma to adjuvant treatment with autologous natural dendritic cell (nDC) or placebo (PL). Overall, 144 patients collected serum and stool samples before and after 2 bimonthly injections to perform metabolomics (MB) and metagenomics (MG) as prespecified exploratory analysis. Clinical outcomes are reported separately. Here we show that different microbes were associated with prognosis, with the health-related Faecalibacterium prausnitzii standing out as the main beneficial taxon for no recurrence at 2 years (p = 0.008 at baseline, nDC arm). Therapy coincided with major MB perturbations (acylcarnitines, carboxylic and fatty acids). Despite randomization, nDC arm exhibited MG and MB bias at baseline: relative under-representation of F. prausnitzii, and perturbations of primary biliary acids (BA). F. prausnitzii anticorrelated with BA, medium- and long-chain acylcarnitines. Combined, these MG and MB biomarkers markedly determined prognosis. Altogether, the host-microbial interaction may play a role in localized melanoma. We value systematic MG and MB profiling in randomized trials to avoid baseline differences attributed to host-microbe interactions.

Caloric restriction for the immunometabolic control of human health

Nutrition affects all physiological processes occurring in our body, including those related to the function of the immune system; indeed, metabolism has been closely associated with the differentiation and activity of both innate and adaptive immune cells. While excessive energy intake and adiposity have been demonstrated to cause systemic inflammation, several clinical and experimental evidence show that calorie restriction (CR), not leading to malnutrition, is able to delay aging and exert potent anti-inflammatory effects in different pathological conditions. This review provides an overview of the ability of different CR-related nutritional strategies to control autoimmune, cardiovascular, and infectious diseases, as tested by preclinical studies and human clinical trials, with a specific focus on the immunological aspects of these interventions. In particular, we recapitulate the state of the art on the cellular and molecular mechanisms pertaining to immune cell metabolic rewiring, regulatory T cell expansion, and gut microbiota composition, which possibly underline the beneficial effects of CR. Although studies are still needed to fully evaluate the feasibility and efficacy of the nutritional intervention in clinical practice, the experimental observations discussed here suggest a relevant role of CR in lowering the inflammatory state in a plethora of different pathologies, thus representing a promising therapeutic strategy for the control of human health.

Indole-3-Propionic Acid Protects Against Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a common but poorly understood form of heart failure, characterized by impaired diastolic function. It is highly heterogeneous with multiple comorbidities, including obesity and diabetes, making human studies difficult.

METHODS

Metabolomic analyses in a mouse model of HFpEF showed that levels of indole-3-propionic acid (IPA), a metabolite produced by gut bacteria from tryptophan, were reduced in the plasma and heart tissue of HFpEF mice as compared with controls. We then examined the role of IPA in mouse models of HFpEF as well as 2 human HFpEF cohorts.

RESULTS

The protective role and therapeutic effects of IPA were confirmed in mouse models of HFpEF using IPA dietary supplementation. IPA attenuated diastolic dysfunction, metabolic remodeling, oxidative stress, inflammation, gut microbiota dysbiosis, and intestinal epithelial barrier damage. In the heart, IPA suppressed the expression of NNMT (nicotinamide N-methyl transferase), restored nicotinamide, NAD+/NADH, and SIRT3 (sirtuin 3) levels. IPA mediates the protective effects on diastolic dysfunction, at least in part, by promoting the expression of SIRT3. SIRT3 regulation was mediated by IPA binding to the aryl hydrocarbon receptor, as Sirt3 knockdown diminished the effects of IPA on diastolic dysfunction in vivo. The role of the nicotinamide adenine dinucleotide circuit in HFpEF was further confirmed by nicotinamide supplementation, Nnmt knockdown, and Nnmt overexpression in vivo. IPA levels were significantly reduced in patients with HFpEF in 2 independent human cohorts, consistent with a protective function in humans, as well as mice.

CONCLUSIONS

Our findings reveal that IPA protects against diastolic dysfunction in HFpEF by enhancing the nicotinamide adenine dinucleotide salvage pathway, suggesting the possibility of therapeutic management by either altering the gut microbiome composition or supplementing the diet with IPA.

Myocardial Metabolic Reprogramming in HFpEF

Heart failure (HF) caused by structural or functional cardiac abnormalities is a significant cause of morbidity and mortality worldwide. While HF with reduced ejection fraction (HErEF) is well understood, more than half of patients have HF with preserved ejection fraction (HFpEF). Currently, the treatment for HFpEF primarily focuses on symptom alleviation, lacking specific drugs. The stressed heart undergoes metabolic switches in substrate preference, which is a compensatory process involved in cardiac pathological remodeling. Although metabolic reprogramming in HF has gained attention in recent years, its role in HFpEF still requires further elucidation. In this review, we present a summary of cardiac mitochondrial dysfunction and cardiac metabolic reprogramming in HFpEF. Additionally, we emphasize potential therapeutic approaches that target metabolic reprogramming for the treatment of HFpEF.

Senescent hearts from male Ts65Dn mice exhibit preserved function but altered size and nicotinamide adenine dinucleotide pathway signaling

Down syndrome (DS) is associated with congenital heart defects at birth, but cardiac function has not been assessed at older ages. We used the Ts65Dn mouse, a model of DS, to quantify heart structure and function with echocardiography in 18-mo male Ts65Dn and wild-type (WT) mice. Heart weight, nicotinamide adenine dinucleotide (NAD) signaling, and mitochondrial (citrate synthase) activity were investigated, as these pathways may be implicated in the cardiac pathology of DS. The left ventricle was smaller in Ts65Dn versus WT, as well as the anterior wall thickness of the left ventricle during both diastole (LVAW_d; mm) and systole (LVAW_s; mm) as assessed by echocardiography. Other functional metrics were similar between groups including left ventricular area end systole (mm2), left ventricular area end diastole (mm2), left ventricular diameter end systole (mm), left ventricular diameter end diastole (mm), isovolumetric relaxation time (ms), mitral valve atrial peak velocity (mm/s), mitral valve early peak velocity (mm/s), ratio of atrial and early peak velocities (E/A), heart rate (beats/min), ejection fraction (%), and fractional shortening (%). Nicotinamide phosphoribosyltransferase (NAMPT) protein expression, NAD concentration, and tissue weight were lower in the left ventricle of Ts65Dn versus WT mice. Sirtuin 3 (SIRT3) protein expression and citrate synthase activity were not different between groups. Although cardiac function was generally preserved in male Ts65Dn, the altered heart size and bioenergetic disturbances may contribute to differences in aging for DS.

Caloric Restriction Rejuvenates Skeletal Muscle Growth in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a major clinical problem, with limited treatments. HFpEF is characterized by a distinct, but poorly understood, skeletal muscle pathology, which could offer an alternative therapeutic target. In a rat model, we identified impaired myonuclear accretion as a mechanism for low myofiber growth in HFpEF following resistance exercise. Acute caloric restriction rescued skeletal muscle pathology in HFpEF, whereas cardiac therapies had no effect. Mechanisms regulating myonuclear accretion were dysregulated in patients with HFpEF. Overall, these findings may have widespread implications in HFpEF, indicating combined dietary with exercise interventions as a beneficial approach to overcome skeletal muscle pathology.

Loss of cardiac mitochondrial complex I persulfidation impairs NAD+ homeostasis in aging

Protein persulfidation is a significant post-translational modification that involves addition of a sulfur atom to the cysteine thiol group and is facilitated by sulfide species. Persulfidation targets reactive cysteine residues within proteins, influencing their structure and/or function across various biological systems. This modification is evolutionarily conserved and plays a crucial role in preventing irreversible cysteine overoxidation, a process that becomes prominent with aging. While, persulfidation decreases with age, its levels in the aged heart and the functional implications of such a reduction in cardiac metabolism remain unknown. Here we interrogated the cardiac persulfydome in wild-type adult mice and age-matched mice lacking the two sulfide generating enzymes, namely cystathionine gamma lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3MST). Our findings revealed that cardiac persulfidated proteins in wild type hearts are less abundant compared to those in other organs, with a primary involvement in mitochondrial metabolic processes. We further focused on one specific target, NDUFB7, which undergoes persulfidation by both CSE and 3MST derived sulfide species. In particular, persulfidation of cysteines C80 and C90 in NDUFB7 protects the protein from overoxidation and maintains the complex I activity in cardiomyocytes. As the heart ages, the levels of CSE and 3MST in cardiomyocytes decline, leading to reduced NDUFB7 persulfidation and increased cardiac NADH/NAD+ ratio. Collectively, our data provide compelling evidence for a direct link between cardiac persulfidation and mitochondrial complex I activity, which is compromised in aging.