Nicotinamide for the treatment of heart failure with preserved ejection fraction

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.

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.

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 (stress/strain) properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Mice fed a High Fat/Sugar Diet (HFSD vs control) for at least 25 weeks exhibited glucose intolerance, obesity and diastolic dysfunction (echo E/e'). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. The E/e' doppler ratio 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 Ca 2+ transient decay time course was prolonged. With transition from 2-4Hz pacing, HFSD cardiomyocyte stiffness was further increased, yet diastolic Ca 2+ rise was 50% less than control. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from intrinsic cardiomyocyte mechanical abnormality. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca 2+ interaction contributes to 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, ≥25weeks) and performance of intact isolated cardiomyocytes derived from the same hearts was measured during pacing under non-loaded, loaded and stretched conditions in vitro . Using a calibrated cardiomyocyte stretch protocol, stiffness (stress/strain) was elevated in HFSD cardiomyocytes in vitro and correlated with diastolic dysfunction (E/e') in vivo . The HFSD cardiomyocyte Ca 2+ transient decay was prolonged in response to stretch, and stiffness was accentuated in response to pacing increase while the rise in diastolic Ca 2+ was attenuated. These findings suggest that stretch-dependent augmentation of the myofilament-Ca 2+ response during diastole partially underlies elevated cardiomyocyte stiffness and diastolic dysfunction of hearts of animals with cardiometabolic disease.

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.

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.

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.

New Perspectives for Antihypertensive Sartans as Components of Co-crystals and Co-amorphous Solids with Improved Properties and Multipurpose Activity

Sartans (angiotensin II receptor blockers, ARBs), drugs used in the treatment of hypertension, play a principal role in addressing the global health challenge of hypertension. In the past three years, their potential use has expanded to include the possibility of their application in the treatment of COVID-19 and neurodegenerative diseases (80 clinical studies worldwide). However, their therapeutic efficacy is limited by their poor solubility and bioavailability, prompting the need for innovative approaches to improve their pharmaceutical properties. This review discusses methods of co-crystallization and co-amorphization of sartans with nonpolymeric, low molecular, and stabilizing co-formers, as a promising strategy to synthesize new multipurpose drugs with enhanced pharmaceutical properties. The solid-state forms have demonstrated the potential to address the poor solubility limitations of conventional sartan formulations and offer new opportunities to develop dual-active drugs with broader therapeutic applications. The review includes an in-depth analysis of the co-crystal and co-amorphous forms of sartans, including their properties, possible applications, and the impact of synthetic methods on their pharmacokinetic properties. By shedding light on the solid forms of sartans, this article provides valuable insights into their potential as improved drug formulations. Moreover, this review may serve as a valuable resource for designing similar solid forms of sartans and other drugs, fostering further advances in pharmaceutical research and drug development.

NAD metabolism: Role in senescence regulation and aging

The geroscience hypothesis proposes that addressing the biology of aging could directly prevent the onset or mitigate the severity of multiple chronic diseases. Understanding the interplay between key aspects of the biological hallmarks of aging is essential in delivering the promises of the geroscience hypothesis. Notably, the nucleotide nicotinamide adenine dinucleotide (NAD) interfaces with several biological hallmarks of aging, including cellular senescence, and changes in NAD metabolism have been shown to be involved in the aging process. The relationship between NAD metabolism and cellular senescence appears to be complex. On the one hand, the accumulation of DNA damage and mitochondrial dysfunction induced by low NAD+ can promote the development of senescence. On the other hand, the low NAD+ state that occurs during aging may inhibit SASP development as this secretory phenotype and the development of cellular senescence are both highly metabolically demanding. However, to date, the impact of NAD+ metabolism on the progression of the cellular senescence phenotype has not been fully characterized. Therefore, to explore the implications of NAD metabolism and NAD replacement therapies, it is essential to consider their interactions with other hallmarks of aging, including cellular senescence. We propose that a comprehensive understanding of the interplay between NAD boosting strategies and senolytic agents is necessary to advance the field.

Impact of NAD+ metabolism on ovarian aging

Nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme in cellular redox reactions, is closely associated with age-related functional degeneration and metabolic diseases. NAD exerts direct and indirect influences on many crucial cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cellular senescence, and immune cell functionality. These cellular processes and functions are essential for maintaining tissue and metabolic homeostasis, as well as healthy aging. Causality has been elucidated between a decline in NAD levels and multiple age-related diseases, which has been confirmed by various strategies aimed at increasing NAD levels in the preclinical setting. Ovarian aging is recognized as a natural process characterized by a decline in follicle number and function, resulting in decreased estrogen production and menopause. In this regard, it is necessary to address the many factors involved in this complicated procedure, which could improve fertility in women of advanced maternal age. Concerning the decrease in NAD+ levels as ovarian aging progresses, promising and exciting results are presented for strategies using NAD+ precursors to promote NAD+ biosynthesis, which could substantially improve oocyte quality and alleviate ovarian aging. Hence, to acquire further insights into NAD+ metabolism and biology, this review aims to probe the factors affecting ovarian aging, the characteristics of NAD+ precursors, and the current research status of NAD+ supplementation in ovarian aging. Specifically, by gaining a comprehensive understanding of these aspects, we are optimistic about the prominent progress that will be made in both research and therapy related to ovarian aging.

Clinical Impact and Mechanisms of Nonatherosclerotic Vascular Aging: The New Kid to Be Blocked

Ischemic cardiovascular disease and stroke remain the leading cause of global morbidity and mortality. During aging, protective mechanisms in the body gradually deteriorate, resulting in functional, structural, and morphologic changes that affect the vascular system. Because atherosclerotic plaques are not always present along with these alterations, we refer to this kind of vascular aging as nonatherosclerotic vascular aging (NAVA). To maintain proper vascular function during NAVA, it is important to preserve intracellular signalling, prevent inflammation, and block the development of senescent cells. Pharmacologic interventions targeting these components are potential therapeutic approaches for NAVA, with a particular emphasis on inflammation and senescence. This review provides an overview of the pathophysiology of vascular aging and explores potential pharmacotherapies that can improve the function of aged vasculature, focusing on NAVA.

The Roles of Caloric Restriction Mimetics in Central Nervous System Demyelination and Remyelination

The dysfunction of myelinating glial cells, the oligodendrocytes, within the central nervous system (CNS) can result in the disruption of myelin, the lipid-rich multi-layered membrane structure that surrounds most vertebrate axons. This leads to axonal degeneration and motor/cognitive impairments. In response to demyelination in the CNS, the formation of new myelin sheaths occurs through the homeostatic process of remyelination, facilitated by the differentiation of newly formed oligodendrocytes. Apart from oligodendrocytes, the two other main glial cell types of the CNS, microglia and astrocytes, play a pivotal role in remyelination. Following a demyelination insult, microglia can phagocytose myelin debris, thus permitting remyelination, while the developing neuroinflammation in the demyelinated region triggers the activation of astrocytes. Modulating the profile of glial cells can enhance the likelihood of successful remyelination. In this context, recent studies have implicated autophagy as a pivotal pathway in glial cells, playing a significant role in both their maturation and the maintenance of myelin. In this Review, we examine the role of substances capable of modulating the autophagic machinery within the myelinating glial cells of the CNS. Such substances, called caloric restriction mimetics, have been shown to decelerate the aging process by mitigating age-related ailments, with their mechanisms of action intricately linked to the induction of autophagic processes.

Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns

Recent research has unveiled an expansive role of NAD+ in cellular energy generation, redox reactions, and as a substrate or cosubstrate in signaling pathways that regulate health span and aging. This review provides a critical appraisal of the clinical pharmacology and the preclinical and clinical evidence for therapeutic effects of NAD+ precursors for age-related conditions, with a particular focus on cardiometabolic disorders, and discusses gaps in current knowledge. NAD+ levels decrease throughout life; age-related decline in NAD+ bioavailability has been postulated to be a contributor to many age-related diseases. Raising NAD+ levels in model organisms by administration of NAD+ precursors improves glucose and lipid metabolism; attenuates diet-induced weight gain, diabetes, diabetic kidney disease, and hepatic steatosis; reduces endothelial dysfunction; protects heart from ischemic injury; improves left ventricular function in models of heart failure; attenuates cerebrovascular and neurodegenerative disorders; and increases health span. Early human studies show that NAD+ levels can be raised safely in blood and some tissues by oral NAD+ precursors and suggest benefit in preventing nonmelanotic skin cancer, modestly reducing blood pressure and improving lipid profile in older adults with obesity or overweight; preventing kidney injury in at-risk patients; and suppressing inflammation in Parkinson disease and SARS-CoV-2 infection. Clinical pharmacology, metabolism, and therapeutic mechanisms of NAD+ precursors remain incompletely understood. We suggest that these early findings provide the rationale for adequately powered randomized trials to evaluate the efficacy of NAD+ augmentation as a therapeutic strategy to prevent and treat metabolic disorders and age-related conditions.

Obesity Enables NLRP3 Activation and Induces Myocardial Fibrosis via Hyperacetylation of HADHa

Obesity increases the risk of myocardial fibrosis, a pathological change in most heart diseases, but the mechanism has not been fully elucidated. Here, we found that mice with high-fat diet-induced obesity had more severe myocardial fibrosis than control mice under normal and ischemia/reperfusion (I/R) conditions, which could be alleviated by neutralizing antibodies against interleukin (IL)-1β and IL-18, downstream products of the nucleotide-binding oligomerization-like receptor protein 3 (NLRP3) inflammasome, and the NLRP3 inhibitor MCC950. Mechanistically, mitochondrial hyperacetylation in obese mouse hearts recruited apoptosis-associated speck-like protein containing a CARD (ASC) to mitochondria and thus facilitated NLRP3 inflammasome assembly. Acetylation of K255 on hydroxyl-CoA dehydrogenase α subunit (HADHa) was identified to trigger the mitochondrial localization of ASC. Blockade of HADHa-K255 acetylation downregulated mitochondrial ASC, suppressed the NLRP3 inflammasome, and attenuated post-I/R myocardial fibrosis in obese mouse hearts. In obese human patients, the extent of myocardial fibrosis according to T1 MRI was positively correlated with the plasma levels of IL-1β and IL-18, supporting the connection of NLRP3 inflammation to obesity-induced myocardial fibrosis. In conclusion, our study demonstrates that the heart is susceptible to fibrosis under obesity through hyperacetylated HADHa-mediated activation of the NLRP3 inflammasome.

ARTICLE HIGHLIGHTS

NAD+: A key metabolic regulator with great therapeutic potential for myocardial infarction via Sirtuins family

Myocardial infarction (MI) is one of the complex phenotypes of coronary artery disease, which results from the interaction of multiple genetic and environmental factors. Nicotinamide Adenine Dinucleotide (NAD+) is an important cofactor regulating metabolic homeostasis and a rate-limiting substrate for sirtuin (SIRT) deacetylase. Numerous NAD+ studies have shown that it can be used as an anti-MI treatment. However, there have been few systematic reviews of the overall role of NAD+ in treating MI. MI, which has long been a global health problem, still lacks effective treatment till now, and the discovery of NAD+ provides a new perspective on its adjuvant treatment. This review summarizes the role of NAD+ signaling in SIRTs in alleviating MI.

Hallmarks of cardiovascular ageing

Normal circulatory function is a key determinant of disease-free life expectancy (healthspan). Indeed, pathologies affecting the cardiovascular system, which are growing in prevalence, are the leading cause of global morbidity, disability and mortality, whereas the maintenance of cardiovascular health is necessary to promote both organismal healthspan and lifespan. Therefore, cardiovascular ageing might precede or even underlie body-wide, age-related health deterioration. In this Review, we posit that eight molecular hallmarks are common denominators in cardiovascular ageing, namely disabled macroautophagy, loss of proteostasis, genomic instability (in particular, clonal haematopoiesis of indeterminate potential), epigenetic alterations, mitochondrial dysfunction, cell senescence, dysregulated neurohormonal signalling and inflammation. We also propose a hierarchical order that distinguishes primary (upstream) from antagonistic and integrative (downstream) hallmarks of cardiovascular ageing. Finally, we discuss how targeting each of the eight hallmarks might be therapeutically exploited to attenuate residual cardiovascular risk in older individuals.

Smurfness-based two-phase model of ageing helps deconvolve the ageing transcriptional signature

Ageing is characterised at the molecular level by six transcriptional 'hallmarks of ageing', that are commonly described as progressively affected as time passes. By contrast, the 'Smurf' assay separates high-and-constant-mortality risk individuals from healthy, zero-mortality risk individuals, based on increased intestinal permeability. Performing whole body total RNA sequencing, we found that Smurfness distinguishes transcriptional changes associated with chronological age from those associated with biological age. We show that transcriptional heterogeneity increases with chronological age in non-Smurf individuals preceding the other five hallmarks of ageing that are specifically associated with the Smurf state. Using this approach, we also devise targeted pro-longevity genetic interventions delaying entry in the Smurf state. We anticipate that increased attention to the evolutionary conserved Smurf phenotype will bring about significant advances in our understanding of the mechanisms of ageing.

Geranylgeranylacetone reduces cardiomyocyte stiffness and attenuates diastolic dysfunction in a rat model of cardiometabolic syndrome

Titin-dependent stiffening of cardiomyocytes is a significant contributor to left ventricular (LV) diastolic dysfunction in heart failure with preserved LV ejection fraction (HFpEF). Small heat shock proteins (HSPs), such as HSPB5 and HSPB1, protect titin and administration of HSPB5 in vitro lowers cardiomyocyte stiffness in pressure-overload hypertrophy. In humans, oral treatment with geranylgeranylacetone (GGA) increases myocardial HSP expression, but the functional implications are unknown. Our objective was to investigate whether oral GGA treatment lowers cardiomyocyte stiffness and attenuates LV diastolic dysfunction in a rat model of the cardiometabolic syndrome. Twenty-one-week-old male lean (n = 10) and obese (n = 20) ZSF1 rats were studied, and obese rats were randomized to receive GGA (200 mg/kg/day) or vehicle by oral gavage for 4 weeks. Echocardiography and cardiac catheterization were performed before sacrifice at 25 weeks of age. Titin-based stiffness (Fpassive ) was determined by force measurements in relaxing solution with 100 nM [Ca2+ ] in permeabilized cardiomyocytes at sarcomere lengths (SL) ranging from 1.8 to 2.4 μm. In obese ZSF1 rats, GGA reduced isovolumic relaxation time of the LV without affecting blood pressure, EF or LV weight. In cardiomyocytes, GGA increased myofilament-bound HSPB5 and HSPB1 expression. Vehicle-treated obese rats exhibited higher cardiomyocyte stiffness at all SLs compared to lean rats, while GGA reduced stiffness at SL 2.0 μm. In obese ZSF1 rats, oral GGA treatment improves cardiomyocyte stiffness by increasing myofilament-bound HSPB1 and HSPB5. GGA could represent a potential novel therapy for the early stage of diastolic dysfunction in the cardiometabolic syndrome.

Searching for Effective Treatments in HFpEF: Implications for Modeling the Disease in Rodents

BACKGROUND

While the prevalence of heart failure with preserved ejection fraction (HFpEF) has increased over the last two decades, there still remains a lack of effective treatment. A key therapeutic challenge is posed by the absence of animal models that accurately replicate the complexities of HFpEF. The present review summarizes the effects of a wide spectrum of therapeutic agents on HF.

METHODS

Two online databases were searched for studies; in total, 194 experimental protocols were analyzed following the PRISMA protocol.

RESULTS

A diverse range of models has been proposed for studying therapeutic interventions for HFpEF, with most being based on pressure overload and systemic hypertension. They have been used to evaluate more than 150 different substances including ARNIs, ARBs, HMGR inhibitors, SGLT-2 inhibitors and incretins. Existing preclinical studies have primarily focused on LV diastolic performance, and this has been significantly improved by a wide spectrum of candidate therapeutic agents. Few experiments have investigated the normalization of pulmonary congestion, exercise capacity, animal mortality, or certain molecular hallmarks of heart disease.

CONCLUSIONS

The development of comprehensive preclinical HFpEF models, with multi-organ system phenotyping and physiologic stress-based functional testing, is needed for more successful translation of preclinical research to clinical trials.

Boosting NAD preferentially blunts Th17 inflammation via arginine biosynthesis and redox control in healthy and psoriasis subjects

To evaluate whether nicotinamide adenine dinucleotide-positive (NAD+) boosting modulates adaptive immunity, primary CD4+ T cells from healthy control and psoriasis subjects were exposed to vehicle or nicotinamide riboside (NR) supplementation. NR blunts interferon γ (IFNγ) and interleukin (IL)-17 secretion with greater effects on T helper (Th) 17 polarization. RNA sequencing (RNA-seq) analysis implicates NR blunting of sequestosome 1 (sqstm1/p62)-coupled oxidative stress. NR administration increases sqstm1 and reduces reactive oxygen species (ROS) levels. Furthermore, NR activates nuclear factor erythroid 2-related factor 2 (Nrf2), and genetic knockdown of nrf2 and the Nrf2-dependent gene, sqstm1, diminishes NR amelioratory effects. Metabolomics analysis identifies that NAD+ boosting increases arginine and fumarate biosynthesis, and genetic knockdown of argininosuccinate lyase ameliorates NR effects on IL-17 production. Hence NR via amino acid metabolites orchestrates Nrf2 activation, augments CD4+ T cell antioxidant defenses, and attenuates Th17 responsiveness. Oral NR supplementation in healthy volunteers similarly increases serum arginine, sqstm1, and antioxidant enzyme gene expression and blunts Th17 immune responsiveness, supporting evaluation of NAD+ boosting in CD4+ T cell-linked inflammation.

Skeletal muscle atrophy, regeneration, and dysfunction in heart failure: Impact of exercise training

This review highlights some established and some more contemporary mechanisms responsible for heart failure (HF)-induced skeletal muscle wasting and weakness. We first describe the effects of HF on the relationship between protein synthesis and degradation rates, which determine muscle mass, the involvement of the satellite cells for continual muscle regeneration, and changes in myofiber calcium homeostasis linked to contractile dysfunction. We then highlight key mechanistic effects of both aerobic and resistance exercise training on skeletal muscle in HF and outline its application as a beneficial treatment. Overall, HF causes multiple impairments related to autophagy, anabolic-catabolic signaling, satellite cell proliferation, and calcium homeostasis, which together promote fiber atrophy, contractile dysfunction, and impaired regeneration. Although both wasting and weakness are partly rescued by aerobic and resistance exercise training in HF, the effects of satellite cell dynamics remain poorly explored.

Effects of Triiodothyronine Treatment in an Animal Model of Heart Failure with Preserved Ejection Fraction

Background: Low levels of triiodothyronine (T3) are common in patients with heart failure (HF). Our aim was to evaluate the effects of supplementation with low and replacement doses of T3 in an animal model of HF with preserved ejection fraction (HFpEF). Methods: We evaluated four groups: ZSF1 Lean (n = 8, Lean-Ctrl), ZSF1 Obese (rat model of metabolic-induced HFpEF, n = 13, HFpEF), ZSF1 Obese treated with a replacement dose of T3 (n = 8, HFpEF-T3high), and ZSF1 Obese treated with a low-dose of T3 (n = 8, HFpEF-T3low). T3 was administered in drinking water from weeks 13 to 24. The animals underwent anthropometric and metabolic assessments, echocardiography, and peak effort testing with maximum O2 consumption (VO2max) determination at 22 weeks, and a terminal hemodynamic evaluation at 24 weeks. Afterwhile myocardial samples were collected for single cardiomyocyte evaluation and molecular studies. Results: HFpEF animals showed lower serum and myocardial thyroid hormone levels than Lean-Ctrl. Treatment with T3 did not normalize serum T3 levels, but increased myocardial T3 levels to normal levels in the HFpEF-T3high group. Body weight was significantly decreased in both the T3-treated groups, comparing with HFpEF. An improvement in glucose metabolism was observed only in HFpEF-T3high. Both the treated groups had improved diastolic and systolic function in vivo, as well as improved Ca2+ transients and sarcomere shortening and relaxation in vitro. Comparing with HFpEF animals, HFpEF-T3high had increased heart rate and a higher rate of premature ventricular contractions. Animals treated with T3 had higher myocardial expression of calcium transporter ryanodine receptor 2 (RYR2) and α-myosin heavy chain (MHC), with a lower expression of β-MHC. VO2max was not influenced by treatment with T3. Myocardial fibrosis was reduced in both the treated groups. Three animals died in the HFpEF-T3high group. Conclusions: Treatment with T3 was shown to improve metabolic profile, myocardial calcium handling, and cardiac function. While the low dose was well-tolerated and safe, the replacement dose was associated with increased heart rate, and increased risk of arrhythmias and sudden death. Modulation of thyroid hormones may be a potential therapeutic target in HFpEF; however, it is important to take into account the narrow therapeutic window of T3 in this condition.

Identification of crucial genes related to heart failure based on GEO database

BACKGROUND

The molecular biological mechanisms underlying heart failure (HF) remain poorly understood. Therefore, it is imperative to use innovative approaches, such as high-throughput sequencing and artificial intelligence, to investigate the pathogenesis, diagnosis, and potential treatment of HF.

METHODS

First, we initially screened Two data sets (GSE3586 and GSE5406) from the GEO database containing HF and control samples from the GEO database to establish the Train group, and selected another dataset (GSE57345) to construct the Test group for verification. Next, we identified the genes with significantly different expression levels in patients with or without HF and performed functional and pathway enrichment analyses. HF-specific genes were identified, and an artificial neural network was constructed by Random Forest. The ROC curve was used to evaluate the accuracy and reliability of the constructed model in the Train and Test groups. Finally, immune cell infiltration was analyzed to determine the role of the inflammatory response and the immunological microenvironment in the pathogenesis of HF.

RESULTS

In the Train group, 153 significant differentially expressed genes (DEGs) associated with HF were found to be abnormal, including 81 down-regulated genes and 72 up-regulated genes. GO and KEGG enrichment analyses revealed that the down-regulated genes were primarily enriched in organic anion transport, neutrophil activation, and the PI3K-Akt signaling pathway. The upregulated genes were mainly enriched in neutrophil activation and the calcium signaling. DEGs were identified using Random Forest, and finally, 16 HF-specific genes were obtained. In the ROC validation and evaluation, the area under the curve (AUC) of the Train and Test groups were 0.996 and 0.863, respectively.

CONCLUSIONS

Our research revealed the potential functions and pathways implicated in the progression of HF, and designed an RNA diagnostic model for HF tissues using machine learning and artificial neural networks. Sensitivity, specificity, and stability were confirmed by ROC curves in the two different cohorts.

Serum Metabolites Are Associated With HFpEF in Biopsy-Proven Nonalcoholic Fatty Liver Disease

Background Nonalcoholic fatty liver disease (NAFLD) and heart failure with preserved ejection fraction (HFpEF) share common risk factors, including obesity and diabetes. They are also thought to be mechanistically linked. The aim of this study was to define serum metabolites associated with HFpEF in a cohort of patients with biopsy-proven NAFLD to identify common mechanisms. Methods and Results We performed a retrospective, single-center study of 89 adult patients with biopsy-proven NAFLD who had transthoracic echocardiography performed for any indication. Metabolomic analysis was performed on serum using ultrahigh performance liquid and gas chromatography/tandem mass spectrometry. HFpEF was defined as ejection fraction >50% plus at least 1 echocardiographic feature of HFpEF (diastolic dysfunction, abnormal left atrial size) and at least 1 heart failure sign or symptom. We performed generalized linear models to evaluate associations between individual metabolites, NAFLD, and HFpEF. Thirty-seven out of 89 (41.6%) patients met criteria for HFpEF. A total of 1151 metabolites were detected; 656 were analyzed after exclusion of unnamed metabolites and those with >30% missing values. Fifty-three metabolites were associated with the presence of HFpEF with unadjusted P value <0.05; none met statistical significance after adjustment for multiple comparisons. The majority (39/53, 73.6%) were lipid metabolites, and levels were generally increased. Two cysteine metabolites (cysteine s-sulfate and s-methylcysteine) were present at significantly lower levels in patients with HFpEF. Conclusions We identified serum metabolites associated with HFpEF in patients with biopsy-proven NAFLD, with increased levels of multiple lipid metabolites. Lipid metabolism could be an important pathway linking HFpEF to NAFLD.

NAD+ metabolism-based immunoregulation and therapeutic potential

Nicotinamide adenine dinucleotide (NAD⁺) is a critical metabolite that acts as a cofactor in energy metabolism, and serves as a cosubstrate for non-redox NAD⁺-dependent enzymes, including sirtuins, CD38 and poly(ADP-ribose) polymerases. NAD⁺ metabolism can regulate functionality attributes of innate and adaptive immune cells and contribute to inflammatory responses. Thus, the manipulation of NAD⁺ bioavailability can reshape the courses of immunological diseases. Here, we review the basics of NAD⁺ biochemistry and its roles in the immune response, and discuss current challenges and the future translational potential of NAD⁺ research in the development of therapeutics for inflammatory diseases, such as COVID-19.

Stretching the story of titin and muscle function

The discovery of the giant protein titin, also known as connectin, dates almost half a century back. In this review, I recapitulate major advances in the discovery of the titin filaments and the recognition of their properties and function until today. I briefly discuss how our understanding of the layout and interactions of titin in muscle sarcomeres has evolved and review key facts about the titin sequence at the gene (TTN) and protein levels. I also touch upon properties of titin important for the stability of the contractile units and the assembly and maintenance of sarcomeric proteins. The greater part of my discussion centers around the mechanical function of titin in skeletal muscle. I cover milestones of research on titin's role in stretch-dependent passive tension development, recollect the reasons behind the enormous elastic diversity of titin, and provide an update on the molecular mechanisms of titin elasticity, details of which are emerging even now. I reflect on current knowledge of how muscle fibers behave mechanically if titin stiffness is removed and how titin stiffness can be dynamically regulated, such as by posttranslational modifications or calcium binding. Finally, I highlight novel and exciting, but still controversially discussed, insight into the role titin plays in active tension development, such as length-dependent activation and contraction from longer muscle lengths.

Long-term dietary n3 fatty acid prevents aging-related cardiac diastolic and vascular dysfunction

AIMS

The prevalence of left ventricular (LV) diastolic and vascular dysfunction increases with age, eventually leading to heart failure with preserved ejection fraction (HFpEF). A preventive strategy is an unmet medical need. We and others reported previously on the beneficial effects of omega-3 fatty acid alpha linolenic acid (ALA) on cardiovascular disorders in animal models and translational studies. We now investigate whether long-term dietary ALA could prevent LV diastolic dysfunction and vascular aging in a murine model.

METHODS AND RESULTS

Wild-type C57BL/6 J mice were fed a chow or ALA diet for 12 months, starting at 6 months of age. Here, we show that aged (~18 months) mice recapitulate major hallmarks of HFpEF, including LV diastolic dysfunction with preserved ejection fraction, impaired vascular function, cardiac fibrosis, arterial stiffening and inflammation, as well as elevated B-type natriuretic peptide (BNP). Long-term ALA supplementation upregulated the mitochondrial tricarboxylic acid enzyme Idh2 and the antioxidant enzymes SOD1 and Gpx1. It also has been associated with reduced inflammation and ECM remodeling, accompanied by a significant downregulation of fibrosis biomarkers MMP-2 and TGF-β in both cardiac and vascular tissues obtained from aged mice. Our data exhibited the preventive effects of dietary ALA against LV diastolic dysfunction, impaired vasorelaxation, cardiac fibrosis, inflammation and arterial stiffening in aged mice.

CONCLUSIONS

We provide evidence and a simplified mechanistic insight on how long-term ALA supplementation is a successful strategy to prevent the development of age-related diastolic and vascular dysfunction.