AMPK inhibits cardiac hypertrophy by promoting autophagy via mTORC1

AMPK and O-GlcNAcylation: interplay in cardiac pathologies and heart failure

Heart failure (HF) represents a multifaceted clinical syndrome characterized by the heart's inability to pump blood efficiently to meet the body's metabolic demands. Despite advances in medical management, HF remains a major cause of morbidity and mortality worldwide. In recent years, considerable attention has been directed toward understanding the molecular mechanisms underlying HF pathogenesis, with a particular focus on the role of AMP-activated protein kinase (AMPK) and protein O-GlcNAcylation. This review comprehensively examines the current understanding of AMPK and O-GlcNAcylation signalling pathways in HF, emphasizing their interplay and dysregulation. We delve into the intricate molecular mechanisms by which AMPK and O-GlcNAcylation contribute to cardiac energetics, metabolism, and remodelling, highlighting recent preclinical and clinical studies that have explored novel therapeutic interventions targeting these pathways.

Fenofibrate reduces cardiac remodeling by mitochondrial dynamics preservation in a renovascular model of cardiac hypertrophy

Fenofibrate, a PPAR-α agonist clinically used to lower serum lipid levels, reduces cardiac remodeling and improves cardiac function. However, its mechanism of action is not completely elucidated. In this study we examined the effect of fenofibrate on mitochondria in a rat model of renovascular hypertension, focusing on mediators controlling mitochondrial dynamics and autophagy. Rats with two-kidney one-clip (2K1C) hypertension were treated with fenofibrate 150 mg/kg/day (2K1C-FFB) or vehicle (2K1C-VEH) for 8 weeks. Systolic blood pressure and cardiac functional were in-vivo assessed, while cardiomyocyte size and protein expression of mediators of cardiac hypertrophy and mitochondrial dynamics were ex-vivo examined by histological and Western blot analyses. Fenofibrate treatment counteracted the development of hypertension and the increase of left ventricular mass, relative wall thickness and cross-sectional area of cardiomyocytes. Furthermore, fenofibrate re-balanced the expression Mfn2, Drp1 and Parkin, regulators of fusion, fission, mitophagy respectively. Regarding autophagy, the LC3-II/LC3-I ratio was increased in 2K1C-VEH and 2K1C-FFB, whereas the autophagy was increased only in 2K1C-FFB. In cultured H9C2 cardiomyoblasts, fenofibrate reversed the Ang II-induced mRNA up-regulation of hypertrophy markers Nppa and Myh7, accumulation of reactive oxygen species and depolarization of the mitochondrial membrane exerting protection mediated by up-regulation of the Uncoupling protein 2. Our results indicate that fenofibrate acts directly on cardiomyocytes and counteracts the pressure overload-induced cardiac maladaptive remodeling. This study reveals a so far hidden mechanism involving mitochondrial dynamics in the beneficial effects of fenofibrate, support its repurposing for the treatment of cardiac hypertrophy and provide new potential targets for its pharmacological function.

The effect of autophagy on hemoporfin-mediated photodynamic therapy in human umbilical vein endothelial cells

SIGNIFICANCE

Hemoporfin-mediated photodynamic therapy (HMME-PDT) has been recognized as a safe and effective treatment for port wine stain (PWS). However, some patients show limited improvement even after multiple treatments. Herein, we aim to explore the effect of autophagy on HMME-PDT in human umbilical vein endothelial cells (HUVECs), so as to provide theoretical basis and treatment strategies to enhance clinical effectiveness.

METHODS

Establish the in vitro HMME-PDT system by HUVECs. Apoptosis and necrosis were identified by Annexin Ⅴ-FITC/PI flow cytometry, and autophagy flux was detected by monitoring RFP-GFP-LC3 under the fluorescence microscope. Hydroxychloroquine and rapamycin were employed in the mechanism study. Specifically, the certain genes and proteins were qualified by qPCR and Western Blot, respectively. The cytotoxicity was measured by CCK-8, VEGF-A secretion was determined by ELISA, and the tube formation of HUVECs was observed by angiogenesis assay.

RESULTS

In vitro experiments revealed that autophagy and apoptosis coexisted in HUVECs treated by HMME-PDT. Apoptosis was dominant in early stage, while autophagy gradually increased in the middle and late stage. AMPK, AKT and mTOR participated in the regulation of autophagy induced by HMME-PDT, in which AMPK was positive regulation, while AKT and mTOR were negative regulation. Hydroxychloroquine could not inhibit HMME-PDT-induced autophagy, but capable of blocking the fusion of autophagosomes with lysosome. Rapamycin might cooperate with HMME-PDT to enhance autophagy in HUVECs, leading to increased cytotoxicity, reduced VEGF-A secretion, and weakened angiogenesis ability.

CONCLUSIONS

Both autophagy and apoptosis contribute to HMME-PDT-induced HUVECs death. Pretreatment of HUVECs with rapamycin to induce autophagy might enhance the photodynamic killing effect of HMME-PDT on HUVECs. The combination of Rapamycin and HMME-PDT is expected to further improve the clinical efficacy.

Possible Role of Cellular Polyamine Metabolism in Neuronal Apoptosis

Recent studies have shown that cellular levels of polyamines (PAs) are significantly altered in neurodegenerative diseases. Evidence from in vivo animal and in vitro cell experiments suggests that the cellular levels of various PAs may play important roles in the central nervous system through the regulation of oxidative stress, mitochondrial metabolism, cellular immunity, and ion channel functions. Dysfunction of PA metabolism related enzymes also contributes to neuronal injury and cognitive impairment in many neurodegenerative diseases. Therefore, in the current work, evidence was collected to determine the possible associations between cellular levels of PAs, and related enzymes and the development of several neurodegenerative diseases, which could provide a new idea for the treatment of neurodegenerative diseases in the future.

Cardiac Metabolism, Reprogramming, and Diseases

Cardiovascular diseases (CVD) account for the largest bulk of deaths worldwide, posing a massive burden on societies and the global healthcare system. Besides, the incidence and prevalence of these diseases are on the rise, demanding imminent action to revert this trend. Cardiovascular pathogenesis harbors a variety of molecular and cellular mechanisms among which dysregulated metabolism is of significant importance and may even proceed other mechanisms. The healthy heart metabolism primarily relies on fatty acids for the ultimate production of energy through oxidative phosphorylation in mitochondria. Other metabolites such as glucose, amino acids, and ketone bodies come next. Under pathological conditions, there is a shift in metabolic pathways and the preference of metabolites, termed metabolic remodeling or reprogramming. In this review, we aim to summarize cardiovascular metabolism and remodeling in different subsets of CVD to come up with a new paradigm for understanding and treatment of these diseases.

The potential of herbal drugs to treat heart failure: The roles of Sirt1/AMPK

Heart failure (HF) is a highly morbid syndrome that seriously affects the physical and mental health of patients and generates an enormous socio-economic burden. In addition to cardiac myocyte oxidative stress and apoptosis, which are considered mechanisms for the development of HF, alterations in cardiac energy metabolism and pathological autophagy also contribute to cardiac abnormalities and ultimately HF. Silent information regulator 1 (Sirt1) and adenosine monophosphate-activated protein kinase (AMPK) are nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases and phosphorylated kinases, respectively. They play similar roles in regulating some pathological processes of the heart through regulating targets such as peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), protein 38 mitogen-activated protein kinase (p38 MAPK), peroxisome proliferator-activated receptors (PPARs), and mammalian target of rapamycin (mTOR). We summarized the synergistic effects of Sirt1 and AMPK in the heart, and listed the traditional Chinese medicine (TCM) that exhibit cardioprotective properties by modulating the Sirt1/AMPK pathway, to provide a basis for the development of Sirt1/AMPK activators or inhibitors for the treatment of HF and other cardiovascular diseases (CVDs).

Identification of 4 autophagy-related genes in heart failure by bioinformatics analysis and machine learning

Introduction

Autophagy refers to the process of breaking down and recycling damaged or unnecessary components within a cell to maintain cellular homeostasis. Heart failure (HF) is a severe medical condition that poses a serious threat to the patient's life. Autophagy is known to play a pivotal role in the pathogenesis of HF. However, our understanding of the specific mechanisms involved remains incomplete. Here, we identify autophagy-related genes (ARGs) associated with HF, which we believe will contribute to further comprehending the pathogenesis of HF.

Methods

By searching the GEO (Gene Expression Omnibus) database, we found the GSE57338 dataset, which was related to HF. ARGs were obtained from the HADb and HAMdb databases. Annotation of GO and enrichment analysis of KEGG pathway were carried out on the differentially expressed ARGs (AR-DEGs). We employed machine learning algorithms to conduct a thorough screening of significant genes and validated these genes by analyzing external dataset GSE76701 and conducting mouse models experimentation. At last, immune infiltration analysis was conducted, target drugs were screened and a TF regulatory network was constructed.

Results

Through processing the dataset with R language, we obtained a total of 442 DEGs. Additionally, we retrieved 803 ARGs from the database. The intersection of these two sets resulted in 15 AR-DEGs. Upon performing functional enrichment analysis, it was discovered that these genes exhibited significant enrichment in domains related to "regulation of cell growth", "icosatetraenoic acid binding", and "IL-17 signaling pathway". After screening and verification, we ultimately identified 4 key genes. Finally, an analysis of immune infiltration illustrated significant discrepancies in 16 distinct types of immune cells between the HF and control group and up to 194 potential drugs and 16 TFs were identified based on the key genes.

Discussion

In this study, TPCN1, MAP2K1, S100A9, and CD38 were considered as key autophagy-related genes in HF. With these relevant data, further exploration of the molecular mechanisms of autophagy in HF can be carried out.

AMPK Signalling Pathway: A Potential Strategy for the Treatment of Heart Failure with Chinese Medicine

Heart failure (HF) is a complex clinical syndrome that represents the advanced stage of cardiovascular disease, characterized by systolic and diastolic dysfunction of the heart. Despite continuous updates in HF treatment drugs, the morbidity and mortality rates remain high, necessitating ongoing exploration for new therapeutic targets. Adenosine monophosphate-activated protein kinase (AMPK) is the serine/threonine protein kinase which responds to adenosine monophosphate (AMP) levels.Activation of AMPK shifts cellular metabolic patterns from synthesis to catabolism, enhancing energy metabolism in pathological conditions such as inflammation, ischemia, obesity, and aging. Numerous studies have identified AMPK as a vital target for HF treatment, with herbal monomers/extracts and compounds affecting key signaling factors including rapamycin targeting protein (mTOR), silencing regulator protein 1 (SIRT1), nuclear transcription factor E2-related factor 2 (Nrf2), and nuclear transcription factor-κB (NF-κB) through regulation of the AMPK signaling pathway.This modulation can achieve the effects of improving metabolism, autophagy, reducing oxidative stress and inflammatory response in the treatment of heart failure, with the advantages of multi-targeting, comprehensive action and low toxicity.The modulation of the AMPK pathway by Traditional Chinese Medicine (TCM) has emerged as a crucial research direction for the prevention and treatment of HF, but a systematic summary and generalization in this field is lacking. This article provides an overview of the composition, regulation, and mechanism of the AMPK signaling pathway's influence on HF, as well as a summary of current research on the regulation of the AMPK pathway by TCM for HF prevention and treatment. The aim is to serve as a reference for the diagnosis and treatment of HF using TCM and the development of new drugs.

Effects of Vitamin D3 Supplementation and Aerobic Training on Autophagy Signaling Proteins in a Rat Model Type 2 Diabetes Induced by High-Fat Diet and Streptozotocin

The aim of this study was to investigate the combined effects of vitamin D3 supplementation and aerobic training on regulating the autophagy process in rats with type 2 diabetic induced by a high-fat diet and streptozotocin. A total of 40 Wistar rats were divided into five groups: normal control (NC), diabetic control (DC), diabetic + aerobic training (DAT), diabetic + vitamin D3 (DVD), and diabetic + aerobic training + vitamin D3 (DVDAT). The rats underwent eight weeks of aerobic training with an intensity of 60% maximum running speed for one hour, along with weekly subcutaneous injections of 10,000 units of vitamin D3. The protein levels of different autophagy markers were assessed in the left ventricular heart tissue. The results showed that the protein levels of AMPK, pAMPK, mTOR, and pmTOR were significantly lower in the DC group compared to the NC group. Conversely, the levels of ULK, Beclin-1, LC3II, Fyco, and Cathepsin D proteins were significantly higher in the DC group. However, the interventions of aerobic training and vitamin D3 supplementation, either individually or in combination, led to increased levels of AMPK, pAMPK, mTOR, and pmTOR, and decreased levels of ULK, Beclin-1, LC3II, Fyco, and Cathepsin D (p < 0.05). Additionally, the aerobic capacity in the DAT and DVDAT groups was significantly higher compared to the NC, DC, and DVD groups (p < 0.05). These findings suggest that type 2 diabetes is associated with excessive autophagy in the left ventricle. However, after eight weeks of vitamin D3 supplementation and aerobic training, a significant reduction in excessive autophagy was observed in rats with type 2 diabetes.

Assessment of Autophagy Markers Suggests Increased Activity Following LVAD Therapy

Left ventricular reverse remodeling in heart failure is associated with improved clinical outcomes. However, the molecular features that drive this process are poorly defined. Left ventricular assist devices (LVADs) are the therapy associated with the greatest reverse remodeling and lead to partial myocardial recovery in most patients. In this study, we examined whether autophagy may be implicated in post-LVAD reverse remodeling. We found expression of key autophagy factors increased post-LVAD, while autophagic substrates decreased. Autolysosome numbers increased post-LVAD, further indicating increased autophagy. These findings support the conclusion that mechanical unloading activates autophagy, which may underly the reverse remodeling observed.

SGLT2 inhibitors: role in protective reprogramming of cardiac nutrient transport and metabolism

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce heart failure events by direct action on the failing heart that is independent of changes in renal tubular function. In the failing heart, nutrient transport into cardiomyocytes is increased, but nutrient utilization is impaired, leading to deficient ATP production and the cytosolic accumulation of deleterious glucose and lipid by-products. These by-products trigger downregulation of cytoprotective nutrient-deprivation pathways, thereby promoting cellular stress and undermining cellular survival. SGLT2 inhibitors restore cellular homeostasis through three complementary mechanisms: they might bind directly to nutrient-deprivation and nutrient-surplus sensors to promote their cytoprotective actions; they can increase the synthesis of ATP by promoting mitochondrial health (mediated by increasing autophagic flux) and potentially by alleviating the cytosolic deficiency in ferrous iron; and they might directly inhibit glucose transporter type 1, thereby diminishing the cytosolic accumulation of toxic metabolic by-products and promoting the oxidation of long-chain fatty acids. The increase in autophagic flux mediated by SGLT2 inhibitors also promotes the clearance of harmful glucose and lipid by-products and the disposal of dysfunctional mitochondria, allowing for mitochondrial renewal through mitochondrial biogenesis. This Review describes the orchestrated interplay between nutrient transport and metabolism and nutrient-deprivation and nutrient-surplus signalling, to explain how SGLT2 inhibitors reverse the profound nutrient, metabolic and cellular abnormalities observed in heart failure, thereby restoring the myocardium to a healthy molecular and cellular phenotype.

ATROPHIC REMODELING OF THE HEART DURING VITAMIN D DEFICIENCY AND INSUFFICIENCY IN A RAT MODEL

Vitamin D deficiency (VDD) is associated with skeletal muscle wasting and impaired cardiac function in humans and animals. However, the molecular events that cause cardiac dysfunction in VDD are poorly understood, and therefore, therapeutic approaches are limited. In the present study, we investigated the effects of VDD on heart function with an emphasis on signaling pathways that regulate anabolism/catabolism in cardiac muscle. A Vitamin D deficient or insufficient rat model was employed. Heart electrical activity was measured by electrocardiography. Gene expression was monitored by qPCR, while protein expression was assessed by western blotting. Catalytic activities of the proteasome, lysosomal cathepsin activity, and apoptotic caspases were measured by fluorimetry. Vitamin D insufficiency and deficiency led to cardiac arrhythmia, a decrease in heart weight, and an increase in apoptosis and interstitial fibrosis.  Ex-vivo cultures of atria revealed an increase in total protein degradation and a decrease in de-novo protein synthesis. The catalytic activities of the major proteolytic systems: ubiquitin-proteasome system, autophagy-lysosome, and calpains were upregulated in the heart of VDD and insufficient rats. In contrast, the mTOR pathway that regulates protein synthesis was suppressed. These catabolic events were exacerbated by a decrease in the expression of myosin heavy chain and troponin genes, as well as decreased expression and activities of metabolic enzymes. These latter changes occurred despite the activation of the energy sensor, AMPK. Our results provide, compelling evidence for cardiac atrophy in Vitamin D deficient rats. Unlike the skeletal muscle, the heart responded to VDD by activating all three proteolytic systems.

Emerging Therapy for Diabetic Cardiomyopathy: From Molecular Mechanism to Clinical Practice

Diabetic cardiomyopathy is characterized by abnormal myocardial structure or performance in the absence of coronary artery disease or significant valvular heart disease in patients with diabetes mellitus. The spectrum of diabetic cardiomyopathy ranges from subtle myocardial changes to myocardial fibrosis and diastolic function and finally to symptomatic heart failure. Except for sodium–glucose transport protein 2 inhibitors and possibly bariatric and metabolic surgery, there is currently no specific treatment for this distinct disease entity in patients with diabetes. The molecular mechanism of diabetic cardiomyopathy includes impaired nutrient-sensing signaling, dysregulated autophagy, impaired mitochondrial energetics, altered fuel utilization, oxidative stress and lipid peroxidation, advanced glycation end-products, inflammation, impaired calcium homeostasis, abnormal endothelial function and nitric oxide production, aberrant epidermal growth factor receptor signaling, the activation of the renin–angiotensin–aldosterone system and sympathetic hyperactivity, and extracellular matrix accumulation and fibrosis. Here, we summarize several important emerging treatments for diabetic cardiomyopathy targeting specific molecular mechanisms, with evidence from preclinical studies and clinical trials.

PCSK9: A emerging participant in heart failure

Heart failure (HF) is a complex clinical syndrome caused by various cardiovascular diseases. Its main pathogenesis includes cardiomyocyte loss, myocardial energy metabolism disorder, and activation of cardiac inflammation. Due to the clinically unsatisfactory treatment of heart failure, different mechanisms need to be explored to provide new targets for the treatment of this disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene mainly related to familial hypercholesterolemia, was discovered in 2003. Aside from regulating lipid metabolism, PCSK9 may be involved in other biological processes such as apoptosis, autophagy, pyroptosis, inflammation, and tumor immunity and related to diabetes and neurodegenerative diseases. Recently, clinical data have shown that the circulating PCSK9 level is significantly increased in patients with heart failure, and it is related to the prognosis for heart failure. Furthermore, in animal models and patients with myocardial infarction, PCSK9 in the infarct margin area was also found to be significantly increased, which further suggested that PCSK9 might be closely related to heart failure. However, the specific mechanism of how PCSK9 participates in heart failure remains to be further explored. The purpose of this review is to summarize the potential mechanism of PCSK9's involvement in heart failure, thereby providing a new treatment strategy for heart failure.

mTORC2: a multifaceted regulator of autophagy

Autophagy is a multi-step catabolic process that delivers cellular components to lysosomes for degradation and recycling. The dysregulation of this precisely controlled process disrupts cellular homeostasis and leads to many pathophysiological conditions. The mechanistic target of rapamycin (mTOR) is a central nutrient sensor that integrates growth signals with anabolism to fulfil biosynthetic and bioenergetic requirements. mTOR nucleates two distinct evolutionarily conserved complexes (mTORC1 and mTORC2). However, only mTORC1 is acutely inhibited by rapamycin. Consequently, mTORC1 is a well characterized regulator of autophagy. While less is known about mTORC2, the availability of acute small molecule inhibitors and multiple genetic models has led to increased understanding about the role of mTORC2 in autophagy. Emerging evidence suggests that the regulation of mTORC2 in autophagy is mainly through its downstream effector proteins, and is variable under different conditions and cellular contexts. Here, we review recent advances that describe a role for mTORC2 in this catabolic process, and propose that mTORC2 could be a potential clinical target for the treatment of autophagy-related diseases. Video abstract.

Autophagy and pressure overload-induced cardiac hypertrophy

Autophagy plays an important role in the pathogenesis of cardiovascular diseases. Dysregulation of autophagy may have a huge effect on cardiac hypertrophy induced by overload pressure although reports on autophagy and cardiac hypertrophy have been contradictory. Some studies showed that autophagy activation attenuated cardiac hypertrophy. However, others suggested that inhibition of autophagy would be protective. Different research models or different pathways involved could be responsible for it. Cardiac hypertrophy may be alleviated through regulation of autophagy. This review aims to highlight the pathways and therapeutic targets identified in the prevention and treatment of cardiac hypertrophy by regulating autophagy.

The Proteostasis Network: A Global Therapeutic Target for Neuroprotection after Spinal Cord Injury

Proteostasis (protein homeostasis) is critical for cellular as well as organismal survival. It is strictly regulated by multiple conserved pathways including the ubiquitin-proteasome system, autophagy, the heat shock response, the integrated stress response, and the unfolded protein response. These overlapping proteostasis maintenance modules respond to various forms of cellular stress as well as organismal injury. While proteostasis restoration and ultimately organism survival is the main evolutionary driver of such a regulation, unresolved disruption of proteostasis may engage pro-apoptotic mediators of those pathways to eliminate defective cells. In this review, we discuss proteostasis contributions to the pathogenesis of traumatic spinal cord injury (SCI). Most published reports focused on the role of proteostasis networks in acute/sub-acute tissue damage post-SCI. Those reports reveal a complex picture with cell type- and/or proteostasis mediator-specific effects on loss of neurons and/or glia that often translate into the corresponding modulation of functional recovery. Effects of proteostasis networks on such phenomena as neuro-repair, post-injury plasticity, as well as systemic manifestations of SCI including dysregulation of the immune system, metabolism or cardiovascular function are currently understudied. However, as potential interventions that target the proteostasis networks are expected to impact many cell types across multiple organ systems that are compromised after SCI, such therapies could produce beneficial effects across the wide spectrum of highly variable human SCI.

Identification of a long noncoding RNA Gm17501 as a novel negative regulator of cardiac hypertrophy

Pathological cardiac hypertrophy is an independent risk factor for the development of heart failure. Long noncoding RNAs (lncRNAs), an emerging class of non-protein-coding transcripts, are involved in regulation of multiple cardiac diseases through diverse molecular mechanism, whereas the role of cytoplasmic lncRNAs in regulating cardiac hypertrophy remains unclear. In this study, we identified a novel and functional long noncoding RNA Gm17501, which was predominantly expressed in the cytoplasm of cardiomyocytes. The expression level of lncRNA Gm17501 was altered in cardiac hypertrophy induced by pressure overload and phenylephrine treatment. Moreover, lncRNA Gm17501 expression was decreased in the heart tissue of patients with heart failure. Silencing lncRNA Gm17501 aggravated cardiac hypertrophy under pathological stress. Inhibition of lncRNA Gm17501 did not alter the expression of nearby genes but decreased mRNA level of calcium handling proteins which were involved in cardiac contraction. Therefore, the cytoplasmic lncRNA Gm17501 might protect cardiomyocytes against hypertrophy, possibly by maintaining calcium signaling pathway.

Role of m6A Methylation in the Occurrence and Development of Heart Failure

N6-methyladenosine (m6A) RNA methylation is one of the most common epigenetic modifications in RNA nucleotides. It is known that m6A methylation is involved in regulation, including gene expression, homeostasis, mRNA stability and other biological processes, affecting metabolism and a variety of biochemical regulation processes, and affecting the occurrence and development of a variety of diseases. Cardiovascular disease has high morbidity, disability rate and mortality in the world, of which heart failure is the final stage. Deeper understanding of the potential molecular mechanism of heart failure and exploring more effective treatment strategies will bring good news to the sick population. At present, m6A methylation is the latest research direction, which reveals some potential links between epigenetics and pathogenesis of heart failure. And m6A methylation will bring new directions and ideas for the prevention, diagnosis and treatment of heart failure. The purpose of this paper is to review the physiological and pathological mechanisms of m6A methylation that may be involved in cardiac remodeling in heart failure, so as to explain the possible role of m6A methylation in the occurrence and development of heart failure. And we hope to help m6A methylation obtain more in-depth research in the occurrence and development of heart failure.

Calpains as Potential Therapeutic Targets for Myocardial Hypertrophy

Despite advances in its treatment, heart failure remains a major cause of morbidity and mortality, evidencing an urgent need for novel mechanism-based targets and strategies. Myocardial hypertrophy, caused by a wide variety of chronic stress stimuli, represents an independent risk factor for the development of heart failure, and its prevention constitutes a clinical objective. Recent studies performed in preclinical animal models support the contribution of the Ca²⁺-dependent cysteine proteases calpains in regulating the hypertrophic process and highlight the feasibility of their long-term inhibition as a pharmacological strategy. In this review, we discuss the existing evidence implicating calpains in the development of cardiac hypertrophy, as well as the latest advances in unraveling the underlying mechanisms. Finally, we provide an updated overview of calpain inhibitors that have been explored in preclinical models of cardiac hypertrophy and the progress made in developing new compounds that may serve for testing the efficacy of calpain inhibition in the treatment of pathological cardiac hypertrophy.

Small molecule QF84139 ameliorates cardiac hypertrophy via activating the AMPK signaling pathway

Cardiac hypertrophy is a common adaptive response to a variety of stimuli, but prolonged hypertrophy leads to heart failure. Hence, discovery of agents treating cardiac hypertrophy is urgently needed. In the present study, we investigated the effects of QF84139, a newly synthesized pyrazine derivative, on cardiac hypertrophy and the underlying mechanisms. In neonatal rat cardiomyocytes (NRCMs), pretreatment with QF84139 (1-10 μM) concentration-dependently inhibited phenylephrine-induced hypertrophic responses characterized by fetal genes reactivation, increased ANP protein level and enlarged cardiomyocytes. In adult male mice, administration of QF84139 (5-90 mg·kg^-1·d^-1, i.p., for 2 weeks) dose-dependently reversed transverse aortic constriction (TAC)-induced cardiac hypertrophy displayed by cardiomyocyte size, left ventricular mass, heart weights, and reactivation of fetal genes. We further revealed that QF84139 selectively activated the AMPK signaling pathway without affecting the phosphorylation of CaMKIIδ, ERK1/2, AKT, PKCε, and P38 kinases in phenylephrine-treated NRCMs and in the hearts of TAC-treated mice. In NRCMs, QF84139 did not show additive effects with metformin on the AMPK activation, whereas the anti-hypertrophic effect of QF84139 was abolished by an AMPK inhibitor Compound C or knockdown of AMPKα2. In AMPKα2-deficient mice, the anti-hypertrophic effect of QF84139 was also vanished. These results demonstrate that QF84139 attenuates the PE- and TAC-induced cardiac hypertrophy via activating the AMPK signaling. This structurally novel compound would be a promising lead compound for developing effective agents for the treatment of cardiac hypertrophy.

Natural AMPK Activators in Cardiovascular Disease Prevention

Cardiovascular diseases (CVD), as a life-threatening global disease, is receiving worldwide attention. Seeking novel therapeutic strategies and agents is of utmost importance to curb CVD. AMP-activated protein kinase (AMPK) activators derived from natural products are promising agents for cardiovascular drug development owning to regulatory effects on physiological processes and diverse cardiometabolic disorders. In the past decade, different therapeutic agents from natural products and herbal medicines have been explored as good templates of AMPK activators. Hereby, we overviewed the role of AMPK signaling in the cardiovascular system, as well as evidence implicating AMPK activators as potential therapeutic tools. In the present review, efforts have been made to compile and update relevant information from both preclinical and clinical studies, which investigated the role of natural products as AMPK activators in cardiovascular therapeutics.

Remote cyclic compression ameliorates myocardial infarction injury in rats via AMPK-dependent pathway

BACKGROUND

Remote ischemic conditioning (RIC) displays a cardioprotective role in acute myocardial infarction (AMI). Since interruption of blood vessel is not an essential trigger of remote cardioprotection, tissue compression may play a prominent part in the effect. The purpose of this study was to confirm the protective effect of tissue compression on AMI and the underlying mechanisms.

METHODS AND RESULTS

Rat model of AMI was induced by ligation of the left anterior descending coronary artery. Remote cyclic compression (RCC) on forelimb was applied to AMI rats for 3 days after the operation. RCC postconditioning displayed cardioprotective effects against AMI injury by limiting infarct size, alleviating cardiac dysfunction, and suppressing cardiomyocyte apoptosis. In addition, RCC postconditioning induced myocardial autophagy as evidenced by increased LC3-II and Beclin-1 and reduced mTOR levels. Furthermore, RCC treatment upregulated AMPK phosphorylation in the context of AMI hearts. AMPK inhibitor Compound C administration markedly abrogated RCC-mediated cardioprotective effect, as evidenced by decreased infarct size and cardiac function.

CONCLUSION

Our results indicated that RCC postconditioning could attenuate AMI injury through inhibiting apoptosis and promoting autophagy via AMPK signaling pathway. The research provided a novel perspective for studying the cardioprotection of RIC and possible therapeutic strategy for managing AMI injury.

SGLT2 Inhibition for Cardiovascular Diseases, Chronic Kidney Disease, and NAFLD

Sodium glucose cotransporter 2 (SGLT-2) inhibitors are the latest class of antidiabetic medications. They prevent glucose reabsorption in the proximal convoluted tubule to decrease blood sugar. Several animal studies revealed that SGLT-2 is profoundly involved in the inflammatory response, fibrogenesis, and regulation of numerous intracellular signaling pathways. Likewise, SGLT-2 inhibitors markedly attenuated inflammation and fibrogenesis and improved the function of damaged organ in animal studies, observational studies, and clinical trials. SGLT-2 inhibitors can decrease blood pressure and ameliorate hypertriglyceridemia and obesity. Likewise, they improve the outcome of cardiovascular diseases such as heart failure, arrhythmias, and ischemic heart disease. SGLT-2 inhibitors are associated with lower cardiovascular and all-cause mortality as well. Meanwhile, they protect against nonalcoholic fatty liver disease (NAFLD), chronic kidney disease, acute kidney injury, and improve micro- and macroalbuminuria. SGLT-2 inhibitors can reprogram numerous signaling pathways to improve NAFLD, cardiovascular diseases, and renal diseases. For instance, they enhance lipolysis, ketogenesis, mitochondrial biogenesis, and autophagy while they attenuate the renin-angiotensin-aldosterone system, lipogenesis, endoplasmic reticulum stress, oxidative stress, apoptosis, and fibrogenesis. This review explains the beneficial effects of SGLT-2 inhibitors on NAFLD and cardiovascular and renal diseases and dissects the underlying molecular mechanisms in detail. This narrative review explains the beneficial effects of SGLT-2 inhibitors on NAFLD and cardiovascular and renal diseases using the results of latest observational studies, clinical trials, and meta-analyses. Thereafter, it dissects the underlying molecular mechanisms involved in the clinical effects of SGLT-2 inhibitors on these diseases.

Target Sestrin2 to Rescue the Damaged Organ: Mechanistic Insight into Its Function

Sestrin2 is a stress-inducible metabolic regulator and a conserved antioxidant protein which has been implicated in the pathogenesis of several diseases. Sestrin2 can protect against atherosclerosis, heart failure, hypertension, myocardial infarction, stroke, spinal cord injury neurodegeneration, nonalcoholic fatty liver disease (NAFLD), liver fibrosis, acute kidney injury (AKI), chronic kidney disease (CKD), and pulmonary inflammation. Oxidative stress and cellular damage signals can alter the expression of Sestrin2 to compensate for organ damage. Different stress signals such as those mediated by P53, Nrf2/ARE, HIF-1α, NF-κB, JNK/c-Jun, and TGF-β/Smad signaling pathways can induce Sestrin2 expression. Subsequently, Sestrin2 activates Nrf2 and AMPK. Furthermore, Sestrin2 is a major negative regulator of mTORC1. Sestrin2 indirectly regulates the expression of several genes and reprograms intracellular signaling pathways to attenuate oxidative stress and modulate a large number of cellular events such as protein synthesis, cell energy homeostasis, mitochondrial biogenesis, autophagy, mitophagy, endoplasmic reticulum (ER) stress, apoptosis, fibrogenesis, and lipogenesis. Sestrin2 vigorously enhances M2 macrophage polarization, attenuates inflammation, and prevents cell death. These alterations in molecular and cellular levels improve the clinical presentation of several diseases. This review will shed light on the beneficial effects of Sestrin2 on several diseases with an emphasis on underlying pathophysiological effects.

Autophagy in skin barrier and immune-related skin diseases

Autophagy is a process which is highly conserved in eukaryotes to degrade or recycle cytoplasmic components through lysosomes to maintain cellular homeostasis. Recent studies have shown that autophagy also plays critical roles in cell apoptosis, inflammation, pathogen clearance, and so on under stressed conditions and thereby has been linked to a variety of human disorders. The skin is the largest organ of the body and serves as the first line of defense against environmental insult. Skin as a nutrient-poor environment requires recycling of limited resources via the autophagy machinery to maintain homeostasis. Therefore, dysregulation of autophagy has been linked to skin diseases. In this review, we describe the molecular machinery and regulation of autophagy, discuss its role in keratinocytes and skin barrier, skin immune cells, and immune-related skin diseases including autoimmune skin disorders, allergic skin diseases, infectious skin disorders, and antitumor immunity against skin tumor. Finally, we highlight the potential of autophagy as a therapeutic target for immune-related skin diseases, and delivery of autophagy-related molecules (such as inducers, inhibitors, or nucleic acid molecules) by virtue of physical materials (such as nanoparticles) or biological materials (such as peptides) to skin topically may obtain clinical benefits in immune-related skin diseases. Moreover, developing autophagy-related gene product-based biomarkers may be promising to diagnose immune-related skin diseases.

Gelsolin is an important mediator of Angiotensin II-induced activation of cardiac fibroblasts and fibrosis

Myocardial fibrosis is a characteristic of various cardiomyopathies, and myocardial fibroblasts play a central role in this process. Gelsolin (GSN) is an actin severing and capping protein that regulates actin assembly and may be involved in fibroblast activation. While the role of GSN in mechanical stress-mediated cardiac fibrosis has been explored, its role in myocardial fibrosis in the absence of mechanical stress is not defined. In this study, we investigated the role of GSN in myocardial fibrosis induced by Angiotensin II (Ang II), a profibrotic hormone that is elevated in cardiovascular disease. We utilized mice lacking GSN (Gsn^-/- ) and cultured primary adult cardiac fibroblasts (cFB). In vivo, Ang II infusion in mice resulted in significantly less severe myocardial fibrosis in Gsn^-/- compared with Gsn^+/+ mice, along with diminished activation of the TGFβ1-Smad2/3 pathway, and reduced expression of cardiac extracellular matrix proteins (collagen, fibronectin, periostin). Moreover, Gsn-deficient hearts exhibited suppressed activity of the AMPK pathway and its downstream effectors, mTOR and P70S6Kinase, which could contribute to the suppressed TGFβ1 activity. In vitro, the Ang II-induced activation of cFBs was reduced in Gsn-deficient fibroblasts evident from decreased expression of αSMA and periostin, diminished actin filament turnover; which also exhibited reduced activity of the AMPK-mTOR pathway, and P70S6K phosphorylation. AMPK inhibition compensated for the loss of GSN, restored the levels of G-actin in Gsn^-/- cFBs and promoted activation to myofibroblasts by increasing αSMA and periostin levels. This study reveals a novel role for GSN in mediating myocardial fibrosis by regulating the AMPK-mTOR-P70S6K pathway in cFB activation independent from mechanical stress-induced factors.

TFEB insufficiency promotes cardiac hypertrophy by blocking autophagic degradation of GATA4

Autophagosome-lysosome pathway (ALP) insufficiency has been suggested to play a critical role in the pathogenesis of cardiac hypertrophy. However, the mechanisms underlying ALP insufficiency remain largely unknown, and strategies to specifically manipulate ALP insufficiency for treating cardiac hypertrophy are lacking. Transcription factor EB (TFEB), as a master regulator of ALP, regulates the generation and function of autophagosomes and lysosomes. We found that TFEB was significantly decreased, whereas autophagosome markers were increased in phenylephrine (PE)-induced and transverse aortic constriction-induced cardiomyocyte hypertrophy and failing hearts from patients with dilated cardiomyopathy. Knocking down TFEB induced ALP insufficiency, as indicated by increased autophagosome markers, decreased light chain 3II flux, and cardiomyocyte hypertrophy manifested through increased levels of atrial natriuretic peptide and β-myosin heavy chain and enlarged cell size. The effects of TFEB knockdown were abolished by promoting autophagy. TFEB overexpression improved autophagic flux and attenuated PE-stimulated cardiomyocyte hypertrophy and transverse aortic constriction-induced hypertrophic remodeling, fibrosis, and cardiac dysfunction. Curcumin analog compound C1, a specific TFEB activator, similarly attenuated PE-induced ALP insufficiency and cardiomyocyte hypertrophy. TFEB knockdown increased the accumulation of GATA4, a transcription factor for several genes causing cardiac hypertrophy by blocking autophagic degradation of GATA4, whereas knocking down GATA4 attenuated TFEB downregulation-induced cardiomyocyte hypertrophy. Both TFEB overexpression and C1 promoted GATA4 autophagic degradation and alleviated PE-induced cardiomyocyte hypertrophy. In conclusion, TFEB downregulation plays a vital role in the development of pressure overload-induced cardiac hypertrophy by causing ALP insufficiency and blocking autophagic degradation. Activation of TFEB represents a potential therapeutic strategy for treating cardiac hypertrophy.

Proteome characterisation of extracellular vesicles isolated from heart

Cardiac intercellular communication is critical for heart function and often dysregulated in cardiovascular diseases. While cardiac extracellular vesicles (cEVs) are emerging mediators of signalling, their isolation remains a technical challenge hindering our understanding of cEV protein composition. Here, we utilised Langendorff-collagenase-based enzymatic perfusion and differential centrifugation to isolate cEVs from mouse heart (yield 3-6 μg/heart). cEVs are ∼200 nm, express classical EV markers (Cd63/81/9⁺ , Tsg101⁺ , Pdcd6ip/Alix⁺ ), and are depleted of blood (Alb/Fga/Hba) and cardiac damage markers (Mb, Tnnt2, Ldhb). Comparison with mechanically-derived EVs revealed greater detection of EV markers and decreased cardiac damage contaminants. Mass spectrometry-based proteomic profiling revealed 1721 proteins in cEVs, implicated in proteasomal and autophagic proteostasis, glycolysis, and fatty acid metabolism; essential functions often disrupted in cardiac pathologies. There was striking enrichment of 942 proteins in cEVs compared to mouse heart tissue - implicated in EV biogenesis, antioxidant activity, and lipid transport, suggesting active cargo selection and specialised function. Interestingly, cEVs contain marker proteins for cardiomyocytes, cardiac progenitors, B-cells, T-cells, macrophages, smooth muscle cells, endothelial cells, and cardiac fibroblasts, suggesting diverse cellular origin. We present a method of cEV isolation and provide insight into potential functions, enabling future studies into EV roles in cardiac physiology and disease.

Novel Targets of Metformin in Cardioprotection: Beyond the Effects Mediated by AMPK

Ischemic heart disease is the main cause of death globally. In the heart, the ischemia/reperfusion injury gives rise to a complex cascade of molecular signals, called cardiac remodeling, which generates harmful consequences for the contractile function of the myocardium and consequently heart failure. Metformin is the drug of choice in the treatment of type 2 diabetes mellitus. Clinical data suggest the direct effects of this drug on cardiac metabolism and studies in animal models showed that metformin activates the classical pathway of AMP-activated protein kinase (AMPK), generating cardioprotective effects during cardiac remodeling, hypertrophy and fibrosis. Furthermore, new studies have emerged about other targets of metformin with a potential role in cardioprotection. This state of the art review shows the available scientific evidence of the cardioprotective potential of metformin and its possible effects beyond AMPK. Targeting of autophagy, mitochondrial function and miRNAs are also explored as cardioprotective approaches along with a therapeutic potential. Further advances related to the biological effects of metformin and cardioprotective approaches may provide new therapies to protect the heart and prevent cardiac remodeling and heart failure.

AMP-activated protein kinase: A remarkable contributor to preserve a healthy heart against ROS injury

Heart failure is one of the leading causes of death and disability worldwide. Left ventricle remodeling, fibrosis, and ischemia/reperfusion injury all contribute to the deterioration of cardiac function and predispose to the onset of heart failure. Adenosine monophosphate-activated protein kinase (AMPK) is the universally recognized energy sensor which responds to low ATP levels and restores cellular metabolism. AMPK activation controls numerous cellular processes and, in the heart, it plays a pivotal role in preventing onset and progression of disease. Excessive reactive oxygen species (ROS) generation, known as oxidative stress, can activate AMPK, conferring an additional role of AMPK as a redox-sensor. In this review, we discuss recent insights into the crosstalk between ROS and AMPK. We describe the molecular mechanisms by which ROS activate AMPK and how AMPK signaling can further prevent heart failure progression. Ultimately, we review the potential therapeutic approaches to target AMPK for the treatment of cardiovascular disease and prevention of heart failure.

Inhibition of lncRNA Gm15834 Attenuates Autophagy-Mediated Myocardial Hypertrophy via the miR-30b-3p/ULK1 Axis in Mice

Emerging evidence reveals that autophagy plays crucial roles in cardiac hypertrophy. Long noncoding RNAs (lncRNAs) are novel transcripts that function as gene regulators. However, it is unclear whether lncRNAs regulate autophagy in cardiac hypertrophy. Here, we identified a novel transcript named lncRNA Gm15834, which was upregulated in the transverse aortic constriction (TAC) model in vivo and the angiotensin-II (Ang-II)-induced cardiac hypertrophy model in vitro and was regulated by nuclear factor kappa B (NF-κB). Importantly, forced expression of lncRNA Gm15834 enhanced autophagic activity of cardiomyocytes and promoted myocardial hypertrophy, whereas silencing of lncRNA Gm15834 attenuated autophagy-induced myocardial hypertrophy. Mechanistically, we found that lncRNA Gm15834 could function as an endogenous sponge RNA of microRNA (miR)-30b-3p, which was downregulated in cardiac hypertrophy. Inhibition of miR-30b-3p enhanced cardiomyocyte autophagic activity and aggravated myocardial hypertrophy, whereas overexpression of miR-30b-3p suppressed autophagy-induced myocardial hypertrophy by targeting the downstream autophagy factor of unc-51-like kinase 1 (ULK1). Moreover, inhibition of lncRNA Gm15834 by adeno-associated virus carrying short hairpin RNA (shRNA) suppressed cardiomyocyte autophagic activity, improved cardiac function, and mitigated cardiac hypertrophy. Taken together, our study identified a novel regulatory axis encompassing lncRNA Gm15834/miR-30b-3p/ULK1/autophagy in cardiac hypertrophy, which may provide a potential therapy target for cardiac hypertrophy.

Ghrelin inhibited pressure overload-induced cardiac hypertrophy by promoting autophagy via CaMKK/AMPK signaling pathway

Ghrelin, a novel gut hormone, has been shown to exert protective effects on cardiac dysfunction and remodeling. However, the underlying mechanisms of its protective effects remain unclear. Here, we investigated the effects of ghrelin on cardiac hypertrophy and explored the mechanisms involved. Ghrelin (30 μg.kg^-1. day^-1) was systemically administered to rats with cardiac hypertrophy induced by abdominal aortic constriction (AAC) by a mini-osmotic pump the next day after surgery continuously for 4 weeks. The AAC treated rats without ghrelin infusion showed decreased ghrelin content and expression of its receptors in the hearts. Exogenous ghrelin greatly attenuated cardiac hypertrophy as shown by heart weight to tibial length (HW/TL), hemodynamics, echocardiography, histological analyses, and expression of hypertrophic markers induced by AAC. This corresponded with decreased cardiac fibrosis and inflammation in the hearts of AAC rats treated with ghrelin. Moreover, ghrelin significantly increased the myocardial expression of autophagy markers, which was further confirmed in cultured cardiomyocytes. Concurrently, cardiomyocyte apoptosis in vivo and in vitro was ameliorated by ghrelin, which was reversed by inhibition of autophagy. The enhancement of autophagy and inhibition of apoptosis by ghrelin were eliminated on pretreatment with compound C, an AMP-activated protein kinase (AMPK) inhibitor. Furthermore, inhibition of Ca²⁺/Calmodulin-dependent protein kinase kinase (CaMKK), an upstream kinase of AMPK, made ghrelin fail to activate AMPK and simultaneously reversed ghrelin's promotion of autophagy. In conclusion, ghrelin could exert its cardioprotective effects on cardiac hypertrophy by promoting autophagy, possibly via CaMKK/AMPK signaling pathway.

Testosterone, cardiomyopathies, and heart failure: a narrative review

Testosterone exerts an important regulation of cardiovascular function through genomic and nongenomic pathways. It produces several changes in cardiomyocytes, the main actor of cardiomyopathies, which are characterized by pathological remodeling, eventually leading to heart failure. Testosterone is involved in contractility, in the energy metabolism of myocardial cells, apoptosis, and the remodeling process. In myocarditis, testosterone directly promotes the type of inflammation that leads to fibrosis, and influences viremia with virus localization. At the same time, testosterone exerts cardioprotective effects that have been observed in different studies. There is increasing evidence that low endogenous levels of testosterone have a negative impact in some cardiomyopathies and a protective impact in others. This review focuses on the interrelationships between testosterone and cardiomyopathies and heart failure.

The Relationship Between Reactive Oxygen Species and Endothelial Cell Metabolism

Cardiovascular disease (CVD) has been the leading cause of death for many decades, highlighting the importance of new research and treatments in the field. The role of hypoxia and subsequent free radical production [reactive oxygen species (ROS)] have become an area of particular interest in CVD. Interestingly, our laboratory and other laboratories have recently reported positive roles of subcellular ROS in modulating endothelial cell (EC) metabolism, proliferation, and angiogenesis. This bidirectional relationship between ROS and EC metabolism, as well as functional changes, continues to be an area of active research. Interestingly, ECs have been shown to rely on anaerobic processes for ATP generation, despite their direct access to oxygen. This paradox has proven to be beneficial as the major reliance on glycolysis produces ATP faster, preserves oxygen, and results in reduced ROS levels in contrast to oxidative phosphorylation. This review will address the relationship between ROS and carbohydrate, lipid, and nitrogen metabolism in ECs, and their effects on EC phenotype such as sprouting angiogenesis.

Phosphorylation Modifications Regulating Cardiac Protein Quality Control Mechanisms

Many forms of cardiac disease, including heart failure, present with inadequate protein quality control (PQC). Pathological conditions often involve impaired removal of terminally misfolded proteins. This results in the formation of large protein aggregates, which further reduce cellular viability and cardiac function. Cardiomyocytes have an intricately collaborative PQC system to minimize cellular proteotoxicity. Increased expression of chaperones or enhanced clearance of misfolded proteins either by the proteasome or lysosome has been demonstrated to attenuate disease pathogenesis, whereas reduced PQC exacerbates pathogenesis. Recent studies have revealed that phosphorylation of key proteins has a potent regulatory role, both promoting and hindering the PQC machinery. This review highlights the recent advances in phosphorylations regulating PQC, the impact in cardiac pathology, and the therapeutic opportunities presented by harnessing these modifications.

Role of Exercise on Alleviating Pressure Overload-Induced Left Ventricular Dysfunction and Remodeling via AMPK-Dependent Autophagy Activation

Cardiac hypertrophy is one of the significant risk factors that result in maladaptive cardiac remodeling and heart failure, and exercise is known to exert cardioprotection. In this research, the cardioprotective function and exercise mechanisms were explored.The rats underwent transverse aortic constriction (TAC) or a sham operation. The rats that received TAC were randomly assigned to five groups: (1) rats subjected to a sham operation as control group (SC), (2) rats that underwent TAC group (TC), (3) TAC and moderate-intensity exercise group (TE), (4) TE plus 3-MA group (TEM), and (5) TE plus Compound C group (TEC). The heart function was measured via echocardiography. Histological analysis and relative protein testing were conducted to analyze collagen deposition and apoptosis. Furthermore, western blot was employed to measure the protein expression of relevant signaling pathways. Impaired cardiac function, interstitial fibrosis, enhanced apoptosis, and ER stress were observed in the TAC-induced left ventricular hypertrophy. Exercise attenuated TAC-induced cardiac dysfunction, interstitial fibrosis, and ER stress-related apoptosis. In addition, exercise significantly improved autophagy and upregulated AMPK phosphorylation. Furthermore, AMPK inhibitor Compound C repressed the activation of AMPK, and autophagy inhibitor 3-methyladenine reversed exercise-induced autophagy. All of these abolished the protection of exercise against cardiac dysfunction and fibrosis induced by TAC.Our results indicated that 4 weeks of treadmill exercise could alleviate pressure overload-induced LV dysfunction and remodeling via an autophagy-dependent mechanism, which was induced by enhancing autophagy through the activation of AMPK.

Empagliflozin Ameliorates Obesity-Related Cardiac Dysfunction by Regulating Sestrin2-Mediated AMPK-mTOR Signaling and Redox Homeostasis in High-Fat Diet-Induced Obese Mice

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have favorable cardiovascular outcomes in patients with diabetes. However, whether SGLT2i can improve obesity-related cardiac dysfunction is unknown. Sestrin2 is a novel stress-inducible protein that regulates AMPK-mammalian target of rapamycin (mTOR) and suppresses oxidative damage. The aim of this study was to determine whether empagliflozin (EMPA) improves obesity-related cardiac dysfunction via regulating Sestrin2-mediated pathways in diet-induced obesity. C57BL/6J mice and Sestrin2 knockout mice were fed a high-fat diet (HFD) for 12 weeks and then treated with or without EMPA (10 mg/kg) for 8 weeks. Treating HFD-fed C57BL/6J mice with EMPA reduced body weight and whole-body fat and improved metabolic disorders. Furthermore, EMPA improved myocardial hypertrophy/fibrosis and cardiac function and reduced cardiac fat accumulation and mitochondrial injury. Additionally, EMPA significantly augmented Sestrin2 levels and increased AMPK and endothelial nitric oxide synthase phosphorylation, but inhibited Akt and mTOR phosphorylation. These beneficial effects were partially attenuated in HFD-fed Sestrin2 knockout mice. Intriguingly, EMPA treatment enhanced the Nrf2/HO-1-mediated oxidative stress response, suggesting antioxidant and anti-inflammatory activity. Thus, EMPA improved obesity-related cardiac dysfunction via regulating Sestrin2-mediated AMPK-mTOR signaling and maintaining redox homeostasis. These findings provide a novel mechanism for the cardiovascular protection of SGLT2i in obesity.

Lower Body Weight in Rats Under Hypobaric Hypoxia Exposure Would Lead to Reduced Right Ventricular Hypertrophy and Increased AMPK Activation

Background

Both chronic hypoxia (CH) and long-term chronic intermittent hypoxia (CIH) exposure lead to right ventricular hypertrophy (RVH). Weight loss is an effective intervention to improve cardiac function and energy metabolism in cardiac hypertrophy. Likewise, caloric restriction (CR) also plays an important role in this cardioprotection through AMPK activation. We aimed to determine the influence of body weight (BW) on RVH, AMPK and related variables by comparing rats exposed to both hypoxic conditions.

Methods

Sixty male adult rats were separated into two groups (n = 30 per group) according to their previous diet: a caloric restriction (CR) group and an ad libitum (AL) group. Rats in both groups were randomly assigned to 3 groups: a normoxic group (NX, n = 10), a CIH group (2 days hypoxia/2 days normoxia; n = 10) and a CH group (n = 10). The CR group was previously fed 10 g daily, and the other was fed ad libitum. Rats were exposed to simulated hypobaric hypoxia in a hypobaric chamber set to 428 Torr (the equivalent pressure to that at an altitude of 4,600 m above sea level) for 30 days. Measurements included body weight; hematocrit; serum insulin; glycemia; the degree of RVH (Fulton's index and histology); and AMPK, mTOR, and PP2C expression levels in the right ventricle determined by western blotting.

Results

A lower degree of RVH, higher AMPK activation, and no activation of mTOR were found in the CR groups exposed to hypobaric hypoxia compared to the AL groups (p < 0.05). Additionally, decreased glycemia and serum insulin levels were observed. Interestingly, PP2C expression showed an increase in the AL groups but not in the CR groups (p < 0.05).

Conclusion

Maintaining a low weight before and during exposure to high-altitude hypoxia, during either CH or CIH, could prevent a major degree of RVH. This cardioprotection would likely be due to the activation of AMPK. Thus, body weight is a factor that might contribute to RVH at high altitudes.

Role of Impaired Nutrient and Oxygen Deprivation Signaling and Deficient Autophagic Flux in Diabetic CKD Development: Implications for Understanding the Effects of Sodium-Glucose Cotransporter 2-Inhibitors

Growing evidence indicates that oxidative and endoplasmic reticular stress, which trigger changes in ion channels and inflammatory pathways that may undermine cellular homeostasis and survival, are critical determinants of injury in the diabetic kidney. Cells are normally able to mitigate these cellular stresses by maintaining high levels of autophagy, an intracellular lysosome-dependent degradative pathway that clears the cytoplasm of dysfunctional organelles. However, the capacity for autophagy in both podocytes and renal tubular cells is markedly impaired in type 2 diabetes, and this deficiency contributes importantly to the intensity of renal injury. The primary drivers of autophagy in states of nutrient and oxygen deprivation-sirtuin-1 (SIRT1), AMP-activated protein kinase (AMPK), and hypoxia-inducible factors (HIF-1α and HIF-2α)-can exert renoprotective effects by promoting autophagic flux and by exerting direct effects on sodium transport and inflammasome activation. Type 2 diabetes is characterized by marked suppression of SIRT1 and AMPK, leading to a diminution in autophagic flux in glomerular podocytes and renal tubules and markedly increasing their susceptibility to renal injury. Importantly, because insulin acts to depress autophagic flux, these derangements in nutrient deprivation signaling are not ameliorated by antihyperglycemic drugs that enhance insulin secretion or signaling. Metformin is an established AMPK agonist that can promote autophagy, but its effects on the course of CKD have been demonstrated only in the experimental setting. In contrast, the effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors may be related primarily to enhanced SIRT1 and HIF-2α signaling; this can explain the effects of SGLT2 inhibitors to promote ketonemia and erythrocytosis and potentially underlies their actions to increase autophagy and mute inflammation in the diabetic kidney. These distinctions may contribute importantly to the consistent benefit of SGLT2 inhibitors to slow the deterioration in glomerular function and reduce the risk of ESKD in large-scale randomized clinical trials of patients with type 2 diabetes.

MG-132 attenuates cardiac deterioration of viral myocarditis via AMPK pathway

BACKGROUND

Coxsackievirus B3 (CVB3) is the primary cause of infectious myocarditis. Aggressive immunological activation and apoptosis of myocytes contributes to progressive dysfunction of cardiac contraction and poor prognosis. MG-132, a proteasome inhibitor, regulates mitochondrial-mediated intrinsic myocardial apoptosis and downregulates NF-κB-mediated inflammation. Here, we determined whether AMPK pathway participates in MG-132-mediated myocardial protection in viral-induced myocarditis.

METHODS AND RESULTS

Acute viral myocarditis models were established by intraperitoneal inoculation of CVB3 in male BALB/c mice. Myocarditis and age-matched control mice were administered MG-132 and/or BML-275 dihydrochloride (BML) (AMPK antagonist) intraperitoneally daily from the day following CVB3 inoculation. MG-132 improved hemodynamics and inhibited the structural remodeling of the ventricle in mice with myocarditis, while BML largely blunted these effects. TUNEL staining and immunochemistry suggested that MG-132 exerts anti-apoptotic and anti-inflammatory effects against CVB3-induced myocardial injuries. BML attenuated the effects of MG-132 on anti-apoptosis and anti-inflammation.

CONCLUSION

MG-132 modulated apoptosis and inflammation, improved hemodynamics, and inhibited the structural remodeling of ventricles in a myocarditis mouse model via regulation of the AMPK signal pathway.

Spermidine and spermine delay brain aging by inducing autophagy in SAMP8 mice

The natural polyamine spermidine and spermine have been reported to ameliorate aging and aging-induced dementia. However, the mechanism is still confused. An aging model, the senescence accelerated mouse-8 (SAMP8), was used in this study. Novel object recognition and the open field test results showed that oral administration of spermidine, spermine and rapamycin increased discrimination index, modified number, inner squares distance and times. Spermidine and spermine increased the activity of SOD, and decreased the level of MDA in the aging brain. Spermidine and spermine phosphorylate AMPK and regulate autophagy proteins (LC3, Beclin 1 and p62). Spermidine and spermine balanced mitochondrial and maintain energy for neuron, with the regulation of MFN1, MFN2, DRP1, COX IV and ATP. In addition, western blot results (Bcl-2, Bax and Caspase-3, NLRP3, IL-18, IL-1β) showed that spermidine and spermine prevented apoptosis and inflammation, and elevate the expression of neurotrophic factors, including NGF, PSD95and PSD93 and BDNF in neurons of SAMP8 mice. These results indicated that the effect of spermidine and spermine on anti-aging is related with improving autophagy and mitochondrial function.

Beta 3 adrenoreceptors protect from hypertrophic remodelling through AMP-activated protein kinase and autophagy

Aims

The abundance of beta 3‐adrenergic receptors (β3‐ARs) is upregulated in diseased human myocardium. We previously showed that cardiac‐specific expression of β3‐AR inhibits the hypertrophic response to neurohormonal stimulation. Here, we further analysed signalling pathways involved in the anti‐hypertrophic effect of β3‐AR.

Methods and results

In vitro hypertrophic responses to phenylephrine (PE) were analysed in neonatal rat ventricular myocytes (NRVM) infected with a recombinant adenovirus expressing the human β3‐AR (AdVhβ3). We confirmed results in mice with cardiomyocyte‐specific moderate expression of human β3‐AR (β3‐TG) and wild‐type (WT) littermates submitted to thoracic transverse aortic constriction (TAC) for 9 weeks. We observed a colocalization of β3‐AR with the AMP‐activated protein kinase (AMPK) both in neonatal rat and in adult mouse cardiomyocytes. Treatment of NRVM with PE induced hypertrophy and a decrease in phosphorylation of Thr172‐AMPK (/2, P = 0.0487) and phosphorylation of Ser79‐acetyl‐CoA carboxylase (ACC) (/2.6, P = 0.0317), inducing an increase in phosphorylated Ser235/236 S6 protein (×2.5, P = 0.0367) known to be involved in protein synthesis. These effects were reproduced by TAC in WT mice but restored to basal levels in β3‐AR expressing cells/mice. siRNA targeting of AMPK partly abrogated the anti‐hypertrophic effect of β3‐AR in response to PE in NRVM. Concomitant with hypertrophy, autophagy was decreased by PE, as measured by microtubule‐associated protein 1 light chain 3 (LC3)‐II/LC3‐I ratio (/2.6, P = 0.0010) and p62 abundance (×3, P = 0.0016) in NRVM or by TAC in WT mice (LC3‐II/LC3‐I ratio: /5.4, P = 0.0159), but preserved in human β3‐AR expressing cells and mice, together with reduced hypertrophy.

Conclusions

Cardiac‐specific moderate expression of β3‐AR inhibits the hypertrophic response in part through AMPK activation followed by inhibition of protein synthesis and preservation of autophagy. Activation of the cardiac β3‐AR pathway may provide future therapeutic avenues for the modulation of hypertrophic remodelling.

Application of Autophagy in Cardiovascular Diseases

Autophagy is closely related to the pathogenesis and progression of cardiovascular diseases. Autophagy may be a therapeutic target for many cardiovascular diseases. In this chapter, we will summarize autophagy activators and inhibitors as potential drugs for cardiovascular diseases.

Androgen-Regulated Cardiac Metabolism in Aging Men

The prevalence of cardiovascular mortality is higher in men than in age-matched premenopausal women. Gender differences are linked to circulating sex-related steroid hormone levels and their cardio-specific actions, which are critical factors involved in the prevalence and features of age-associated cardiovascular disease. In women, estrogens have been described as cardioprotective agents, while in men, testosterone is the main sex steroid hormone. The effects of testosterone as a metabolic regulator and cardioprotective agent in aging men are poorly understood. With advancing age, testosterone levels gradually decrease in men, an effect associated with increasing fat mass, decrease in lean body mass, dyslipidemia, insulin resistance and adjustment in energy substrate metabolism. Aging is associated with a decline in metabolism, characterized by modifications in cardiac function, excitation-contraction coupling, and lower efficacy to generate energy. Testosterone deficiency -as found in elderly men- rapidly becomes an epidemic condition, associated with prominent cardiometabolic disorders. Therefore, it is highly probable that senior men showing low testosterone levels will display symptoms of androgen deficiency, presenting an unfavorable metabolic profile and increased cardiovascular risk. Moreover, recent reports establish that testosterone replacement improves cardiomyocyte bioenergetics, increases glucose metabolism and reduces insulin resistance in elderly men. Thus, testosterone-related metabolic signaling and gene expression may constitute relevant therapeutic target for preventing, or treating, age- and gender-related cardiometabolic diseases in men. Here, we will discuss the impact of current evidence showing how cardiac metabolism is regulated by androgen levels in aging men.

Protective effects of glucagon-like peptide-1 on cardiac remodeling by inhibiting oxidative stress through mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase pathway in diabetes mellitus

AIMS/INTRODUCTION

Although increased reactive oxygen species (ROS) generation is a major mechanism leading to cardiac remodeling in diabetes mellitus, research into the effects of anti-oxidation on diabetic cardiac remodeling remains scarce and controversial. Glucagon-like peptide-1 (GLP-1) shows potential anti-oxidative effects besides lowering blood glucose. The objective of this research was to investigate the effects of GLP-1 on cardiac remodeling and the molecular mechanism involved in diabetes mellitus.

MATERIALS AND METHODS

Streptozotocin-induced diabetic rats received exenatide treatment for 3 months. Cardiac function, cardiac weight index and myocardial interstitial fibrosis were measured. Cardiomyocytes were cultured in high-glucose medium with GLP-1 treatment. The ROS production, apoptosis and the levels of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase protein expression in cardiomyocytes were analyzed.

RESULTS

Experimental diabetes mellitus showed impaired cardiac diastolic function, increased brain natriuretic peptide expression and increased interstitial collagen deposition in the myocardium, which were ameliorated by exenatide treatment. Exenatide reduced myocardial ROS production and apoptosis in diabetes mellitus. Also, high glucose-induced ROS generation and apoptosis in cardiomyocytes were inhibited by GLP-1, as well as the levels of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase phosphorylation. Furthermore, GLP-1 treatment upregulated adenosine monophosphate-activated protein kinase activity in high-glucose-induced cardiomyocyte.

CONCLUSIONS

Glucagon-like peptide-1 protects the cardiomyocytes from oxidative stress and apoptosis in diabetes mellitus, which might contribute to the improvement of cardiac remodeling. The cardiac protection of GLP-1 might be dependent on inhibition of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase, through an adenosine monophosphate-activated protein kinase-mediated pathway.

Transcribed Ultraconserved Regions, Uc.323, Ameliorates Cardiac Hypertrophy by Regulating the Transcription of CPT1b (Carnitine Palmitoyl transferase 1b)

Transcribed ultraconserved regions (T-UCRs) are a novel class of long noncoding RNAs transcribed from UCRs, which exhibit 100% DNA sequence conservation among humans, mice, and rats. However, whether T-UCRs regulate cardiac hypertrophy remains unclear. We aimed to explore the effects of T-UCRs on cardiac hypertrophy. First, we performed long noncoding RNA microarray analysis on hearts of mice subjected to sham surgery or aortic banding and found that the T-UCR uc.323 was decreased significantly in mice with aortic banding-induced cardiac hypertrophy. In vitro loss- and gain-of-function experiments demonstrated that uc.323 protected cardiomyocytes against hypertrophy induced by phenylephrine. Additionally, we discovered that mammalian target of rapamycin 1 contributed to phenylephrine-induced uc.323 downregulation and uc.323-mediated cardiomyocyte hypertrophy. We further mapped the possible target genes of uc.323 through global microarray mRNA expression analysis after uc.323 knockdown and found that uc.323 regulated the expression of cardiac hypertrophy-related genes such as CPT1b (Carnitine Palmitoyl transferase 1b). Then, chromatin immunoprecipitation proved that EZH2 (enhancer of zeste homolog 2) bound to the promoter of CPT1b via H3K27me3 (trimethylation of lysine 27 of histone H3) to induce CPT1b downregulation. And overexpression of CPT1b could block uc.323-mediated cardiomyocyte hypertrophy. Finally, we found that uc.323 deficiency induced cardiac hypertrophy. Our results reveal that uc.323 is a conserved T-UCR that inhibits cardiac hypertrophy, potentially by regulating the transcription of CPT1b via interaction with EZH2.