Introduction and Objective: Obesity, a primary cause of cardiometabolic diseases and type 2 diabetes, is associated with impaired brown adipose tissue (BAT) function. Activating Gs-protein-coupled receptors (GPCRs) in BAT is central for promoting thermogenesis and energy expenditure (EE), which play a key role in regulating body weight (BW). However, a complete understanding of altered GPCR signaling in BAT on obesity remains elusive. Methods: In our study, using a mouse model, we identified the adhesion Gi-GPCR brain angiogenesis inhibitor 3 (BAI3) as a negative regulator of EE. BAI3, expressed in BAT, was found to inhibit BAT function. Results: Excitingly, the deletion of BAI3 enhanced EE, reduced fat mass, and decreased adipocyte size, resulting in lower BW without affecting lean mass or food intake in mice on low- and high-fat diets. Importantly, BAI3-deficient mice displayed elevated glucose clearance and internal body temperature during cold exposure, while no EE enhancement occurred at thermoneutrality, indicating BAI3’s role in adaptive thermogenesis. Mechanistically, BAI3 loss enhanced lipogenesis, fatty acid oxidation, fatty acid uptake, mitochondrial function, and thermogenesis in BAT, improving glucose and fatty acid utilization. These changes improved the metabolic profile: glucose clearance, insulin sensitivity, circulating triglycerides, and non-esterified fatty acids. Conclusion: Our findings highlight that BAI3 inhibits BAT function and adaptive thermogenesis. BAI3 ablation protects against diet-induced obesity by enhancing BAT-mediated metabolic activity and EE. Targeting BAI3 signaling represents a promising therapeutic approach to treating obesity and related metabolic disorders through BAT activation. H. Alsharif: None. K. Perez: None. D. Tummala: None. J.B. Alexander: None. G. Ren: None. M. Rahman: None. M. Young: None. S. Bhatnagar: None.

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

OBJECTIVE:Obesity-associated metabolic dysfunction is a major public health concern worldwide. Endothelial dysfunction is a hallmark of metabolic dysfunction, and endothelial cells affect metabolic functions. Because autophagy-related gene 7 (ATG7) is involved in various cellular physiology, we investigated the roles of endothelial cell-ATG7 (EC-ATG7) on high-fat diet-induced obesity and its related metabolic dysfunction. METHODS:We generated an endothelial-specific Atg7 knock-out mouse by breeding Atg7flox/flox mouse with the Chd5-Cre mouse, and investigated the metabolic phenotypes associated with high-fat diet (HFD)-induced obesity. Body weight, food intake, glucose tolerance, insulin sensitivity, and liver fat accumulation were measured in endothelial Atg7 deficient (Atg7ΔEnd) and control mice (Atg7f/f). Adipose tissue inflammation was assessed by measuring the expression of pro-inflammatory genes. Furthermore, we performed indirect calorimetry and examined the insulin signaling pathway molecules. RESULTS:We found that deletion of EC-Atg7 ameliorated HFD-induced weight gain, fatty liver, and adipocyte hypertrophy and inflammatory response in adipose tissue, and improved insulin sensitivity without changing glucose tolerance. These metabolic effects seem to be due to the reduced food intake because there were no differences in energy expenditure, energy excretion to feces, and physical activity. Interestingly, the deletion of EC-Atg7 protected from HFD-induced vascular rarefaction, and the knock-down of Atg7 in endothelial cells protected from fatty acid-induced cell death. CONCLUSIONS:Our results suggest that EC-Atg7 deletion ameliorates HFD-induced obesity and its related metabolic dysfunction, such as insulin resistance and fatty liver by attenuating appetite and vascular rarefaction. The EC-Atg7 deletion may protect the endothelial cells from lipotoxicity and impaired angiogenesis, which preserves the endothelial function in metabolic tissues. These findings may have implications for developing new therapeutic strategies for preventing and treating obesity and its associated health risks.

Changes in circadian-related behaviors (e.g., the timing of food intake, sleep cycles) and the environment (e.g., light-dark cycles) increase the risk of numerous cardiometabolic diseases, including diabetes mellitus and cardiac disease. Recent studies indicate a close interrelationship between circadian clocks and the posttranslational modification, protein O-GlcNAcylation. The current study was designed to investigate whether a modest elevation of protein O-GlcNAcylation in the adult mouse heart, similar to levels observed during pathologic states, influenced circadian governance of the heart. Cardiomyocyte-specific expression of a dominant negative O-GlcNAcase (dnOGAh) for a 2-week period resulted in an approximate 1.5-fold increase in cardiac protein O-GlcNAcylation, impacting 70% of core circadian clock components in the heart at the mRNA level. Further interrogation of cardiac mRNA species in dnOGAh hearts at candidate (RT-PCR) and unbiased (RNAseq) levels revealed a 95% loss of circadian governance of the cardiac transcriptome. This was despite persistent/augmented 24 h oscillations of the core circadian clock proteins BMAL1, REVERBα, and PER2 in dnOGAh hearts. Direct comparison of dnOGAh hearts with cardiomyocyte-specific BMAL1 knockout (CBK) hearts underscored an apparent uncoupling of the core clock mechanism from clock control of downstream target genes in dnOGAh hearts, and highlighted that loss of circadian governance results in interstitial fibrosis. Sustained protein O-GlcNAcylation in the heart causes loss of circadian governance, likely downstream of the core circadian clock mechanism. Moreover, interstitial fibrosis appears to be a universal adverse outcome following impaired circadian governance.

ABSTRACTEnhancing protein O‐GlcNAcylation by pharmacological inhibition of the enzyme O‐GlcNAcase (OGA) has been considered as a strategy to decrease tau and amyloid‐beta phosphorylation, aggregation, and pathology in Alzheimer's disease (AD). There is still more to be learned about the impact of enhancing global protein O‐GlcNAcylation, which is important for understanding the potential of using OGA inhibition to treat neurodegenerative diseases. In this study, we investigated the acute effect of pharmacologically increasing O‐GlcNAc levels, using the OGA inhibitor Thiamet G (TG), in normal mouse brains. We hypothesized that the transcriptome signature in response to a 3 h TG treatment (50 mg/kg) provides a comprehensive view of the effect of OGA inhibition. We then performed mRNA sequencing of the brain using NovaSeq PE 150 (n = 5 each group). We identified 1234 significant differentially expressed genes with TG versus saline treatment. Functional enrichment analysis of the upregulated genes identified several upregulated pathways, including genes normally down in AD. Among the downregulated pathways were the cell adhesion pathway as well as genes normally up in AD and aging. When comparing acute to chronic TG treatment, protein autophosphorylation and kinase activity pathways were upregulated, whereas cell adhesion and astrocyte markers were downregulated in both datasets. AMPK subunit Prkab2 was one gene in the kinase activity pathway, and the increase after acute and chronic treatment was confirmed using qPCR. Interestingly, mitochondrial genes and genes normally down in AD were up in acute treatment and down in chronic treatment. Data from this analysis will enable the evaluation of the mechanisms underlying the impact of OGA inhibition in the treatment of AD. In particular, OGA inhibitors appear to have downstream effects related to bioenergetics which may limit their therapeutic benefits. image

O-GlcNAcylation is a dynamic and reversible protein posttranslational modification of serine or threonine residues which modulates the activity of transcriptional and signaling pathways and controls cellular responses to metabolic and inflammatory stressors. We and others have shown that O-GlcNAcylation has the potential to regulate autophagy and mitophagy to play a critical role in mitochondrial quality control, but this has not been assessed in vivo in the brain. This is important since mitochondrial dysfunction contributes to the development of neurodegenerative diseases. We used mito-QC reporter mice to assess mitophagy in diverse cells in the dentate gyrus in response to pharmacological inhibition of O-GlcNAcase (OGA) with thiamet G which leads to elevation of protein O-GlcNAcylation. We demonstrate that mitophagy occurs predominantly in the GFAP-positive astrocytes and is significantly decreased in response to elevated O-GlcNAcylation. Furthermore, with increased O-GlcNAcylation, the levels of astrocyte markers GFAP and S100B, and the microglial cell marker IBA1, decreased in the dentate gyrus, while the levels of microglial cell marker TMEM119 were increased, indicating significant changes in glia homeostasis. These results provide strong evidence of the regulation of mitophagy and glia signatures by the O-GlcNAc pathway.

Background: The heart adapts to pregnancy at transcriptional, metabolic, morphologic, and functional levels, ensuring that demands of both the mother and developing child are adequately met. How extra-cardiac signals coordinate cardiac adaptation to pregnancy is poorly understood. For various maternal tissues, including mammary glands, adipose and pancreatic β-cells, lactogenic hormones act via the prolactin receptor (PRLR) to orchestrate tissue adaptation during pregnancy. Objective: To determine whether cardiomyocyte prolactin signaling is required for cardiac adaptation to pregnancy. Approach: Timed pregnancies were performed in cardiomyocyte-specific PRLR knockout (cmPRLR-KO) and littermate control (CON) female mice at 9 weeks of age. Systolic and diastolic function were assessed by echocardiography at gestation day 16. Immediately following echocardiography, hearts were isolated for gravimetric, histologic, and molecular analyses. In a subset of studies, the impact of multiple (3) sequential pregnancies was investigated in cmPRLR-KO and CON mice. In all experiments, non-pregnant age-matched female mice were assessed in an identical manner. Results: As anticipated, a single pregnancy increased biventricular weight (+17%; p<0.001), cardiomyocyte size (+64%; p<0.001), left ventricular (LV) area (+8%; p=0.045), and cardiac output (+16%; p=0.032) in CON mice. In contrast, pregnancy-induced alterations in these parameters were either abolished or significantly (p<0.05) attenuated in cmPRLR-KO mice. Given impaired cardiac adaptation of cmPRLR-KO mice to a single pregnancy, we hypothesized that this may lead to maladaptation following multiple pregnancies. Consistent with this premise, 3 sequential pregnancies resulted in cardiomyopathy in cmPRLR-KO mice (but not in CON mice), characterized by reduced LV ejection fraction (-45%; p<0.001), increased LV volume (+196%; p<0.001), increased cardiomyocyte size (+69%; p=0.001), and induction of adverse cardiac remodeling markers (e.g., +266% nppa mRNA; p=0.002). Conclusions: Cardiomyocyte prolactin signaling is essential for adaptation of the heart to pregnancy. Loss of cardiomyocyte prolactin signaling precipitates cardiomyopathy following multiple pregnancies.

This review tracks the discovery of circadian biology in cardiovascular science, starting with early clinical observations of daily changes in heart rate, blood pressure, and cardiovascular events. These patterns suggested that time of day matters, but it was not until the past two decades that the mechanisms and knowledge translation of these rhythms were uncovered. We describe the heart's intrinsic circadian properties and importantly how this leads to regulation of cardiac gene and protein expression, neuroendocrine and vascular rhythms, metabolism, cellular electrophysiology, and cell signaling pathways. Next, we explore emerging themes, including the impact of circadian timing on ischemic injury, cardiac aging, and trends in circadian desynchrony, sex, and interorgan crosstalk. Building on these discoveries, circadian medicine is beginning to reshape clinical care including timing of surgery, chronotherapies, biomarkers, ICU design, novel molecular drugs targeting the circadian clock, the role of the microbiome and time restricted eating, the new field of rest, and the concept of One Health and applications to veterinary medicine. Looking ahead we address new frontiers such as epigenetics, gene editing, and spaceflight. Together, these advances offer a roadmap for how circadian rhythms can be harnessed to improve cardiovascular health and disease outcomes, supporting longer and healthier lives.

Histone deacetylase (HDAC) complexes regulate pathological gene programs during heart disease progression. The recently identified mitotic deacetylase complex (MiDAC), which includes DNTTIP1, ELMSAN1, and HDAC1/2, remains the least characterized among these complexes. ELMSAN1 has been implicated in left ventricular remodeling, and its global deletion in mice leads to heart malformation. To investigate its role in mouse heart, we generated cardiomyocyte-specific Elmsan1 knockout (ELM cKO) using αMHC-driven Cre recombinase. We analyzed both male and female animals across three experimental groups: αMHC-Cre (Cre control), ELM fl/fl (floxed control), and ELM cKO. In male ELM cKO mice, ejection fraction (EF) was significantly reduced by 12 wk (45.64 ± 3.12%), compared with αMHC-Cre (55.91 ± 1.29%) and ELM fl/fl (59.16 ± 3.70%) controls. By 24 wk, EF declined further to 20.79 ± 4.52%, representing a reduction of 46.4% (P < 0.01) and 62.1% (P < 0.0001) compared with αMHC-Cre and ELM fl/fl mice, respectively. The heart failure phenotype in ELM cKO mice was supported by cardiomyocyte hypertrophy morphology, ventricular dilation, and shortened lifespan. Female ELM cKO mice exhibited similar defects with delayed onset. To investigate early molecular changes, we performed RNA sequencing on presymptomatic hearts from 8-wk-old mice. A total of 1,055 genes were differentially expressed in ELM ckO hearts, with 460 upregulated and 595 downregulated. Gene enrichment analysis revealed suppression of tricarboxylic acid cycle and key cardiac genes. These transcriptional changes were accompanied by decreased mitochondrial respiratory chain complex proteins, ultrastructural mitochondrial abnormalities, and impaired calcium handling. Our study demonstrates that Elmsan1 is pivotal for maintaining heart function and hemostasis with advanced age.NEW & NOTEWORTHY Our study demonstrates that Elmsan1, a unique component of the mitotic deacetylase complex (MiDAC), is essential for maintaining cardiac function. Loss of Elmsan1 in cardiomyocytes leads to age-related cardiac dysfunction and mitochondrial abnormalities in mice. Using a cardiomyocyte-specific Elmsan1 knockout model, we show that Elmsan1 preserves adult heart function by regulating genes involved in calcium handling and energy metabolism, underscoring the specific role of MiDAC in maintaining heart hemostasis.

Circadian rhythms, controlled by the suprachiasmatic nucleus and peripheral clocks, regulate 24-h cycles in biological processes such as the cardiovascular system. Circadian rhythms influence autonomic balance, with parasympathetic dominance during sleep supporting cardiac recovery and sympathetic activation during the day supporting circulatory demand. Congruent with systemic and cellular circadian rhythmicity, 24-h patterns arise in the pathophysiology of cardiovascular diseases, including ischaemic heart disease, heart failure, and arrhythmias. Daily variations influence the timing and outcome of myocardial infarction, with studies reporting patterns in infarct size depending on the time of onset. Similar daily patterns are observed in cardio- and cerebrovascular complications. In heart failure, circadian rhythms are dampened but remain intact, suggesting the potential for incorporating timing in diagnostics and therapies. Sudden cardiac death follows a distinct pattern, with a higher incidence in the morning. Atrial fibrillation onset, on the other hand, occurs more frequently at night. Risk factors and modifiers, such as physiological, psychological, lifestyle, and environmental factors and comorbidities interact with circadian rhythms, thereby impacting cellular pathomechanisms and development of cardiovascular health and disease. Chronotherapy, which aligns treatments with circadian rhythms, has demonstrated potential for improving the efficacy of cardiovascular therapies. This review examines the influence of circadian rhythms on cardiovascular health in the context of specific cardiac diseases and risk factors, and it highlights the therapeutic opportunities informed by circadian patterns.

Cardiovascular disease (CVD) is a global health concern. Circadian medicine improves cardiovascular care by aligning treatments with our body’s daily rhythms and their underlying cellular circadian mechanisms. Time-based therapies, or chronotherapies, show special promise in clinical cardiology. They optimize treatment schedules for better outcomes with fewer side effects by recognizing the profound influence of rhythmic body cycles. In this review, we focus on three chronotherapy areas (medication, light, and meal timing) with potential to enhance cardiovascular care. We also highlight pioneering research in the new field of rest, the gut microbiome, novel chronotherapies for hypertension, pain management, and small molecules that targeting the circadian mechanism.

Enhancing protein O-GlcNAcylation by pharmacological inhibition of the enzyme O-GlcNAcase (OGA) is explored as a strategy to decrease tau and amyloid-beta phosphorylation, aggregation, and pathology in Alzheimer's disease (AD). There is still more to be learned about the impact of enhancing global protein O-GlcNAcylation, which is important for understanding the mechanistic path of using OGA inhibition to treat AD. In this study, we investigated the acute effect of pharmacologically increasing O-GlcNAc levels, using OGA inhibitor Thiamet G (TG), on normal mouse brains. We hypothesized that the transcritome signature in respones to TG treatment provides a comprehensive view of the effect of OGA inhibition. We sacrificed the mice and dissected their brains after 3 hours of saline or 50 mg/kg TG treatment, and then performed mRNA sequencing using NovaSeq PE 150 (n=5 each group). We identified 1,234 significant differentially expressed genes with TG versus saline treatment. Functional enrichment analysis of the upregulated genes identified several upregulated pathways, including genes normally down in AD. Among the downregulated pathways were the cell adhesion pathway as well as genes normally up in AD and aging. When comparing acute to chronic TG treatment, protein autophosphorylation and kinase activity pathways were upregulated, whereas cell adhesion and astrocyte markers were downregulated in both datasets. Interestingly, mitochondrial genes and genes normally down in AD were up in acute treatment and down in chronic treatment. Data from this analysis will enable the evaluation of the mechanisms underlying the potential benefits of OGA inhibition in the treatment of AD. In particular, although OGA inhibitors are promising to treat AD, their downstream chronic effects related to bioenergetics may be a limiting factor. Abstract Figure:

Energetic demand and nutrient supply fluctuate as a function of time-of-day, in alignment with sleep-wake and fasting-feeding cycles. These daily rhythms are mirrored by 24-hour oscillations in numerous cardiovascular functional parameters, including blood pressure, heart rate, and myocardial contractility. It is, therefore, not surprising that metabolic processes also fluctuate over the course of the day, to ensure temporal needs for ATP, building blocks, and metabolism-based signaling molecules are met. What has become increasingly clear is that in addition to classic signal-response coupling (termed reactionary mechanisms), cardiovascular-relevant cells use autonomous circadian clocks to temporally orchestrate metabolic pathways in preparation for predicted stimuli/stresses (termed anticipatory mechanisms). Here, we review current knowledge regarding circadian regulation of metabolism, how metabolic rhythms are synchronized with cardiovascular function, and whether circadian misalignment/disruption of metabolic processes contribute toward the pathogenesis of cardiovascular disease.

Time-of-day significantly influences the severity and incidence of stroke. Evidence has emerged not only for circadian governance over stroke risk factors, but also for important determinants of clinical outcome. In this review, we provide a comprehensive overview of the interplay between chronobiology and cerebrovascular disease. We discuss circadian regulation of pathophysiological mechanisms underlying stroke onset or tolerance as well as in vascular dementia. This includes cell death mechanisms, metabolism, mitochondrial function, and inflammation/immunity. Furthermore, we present clinical evidence supporting the link between disrupted circadian rhythms and increased susceptibility to stroke and dementia. We propose that circadian regulation of biochemical and physiological pathways in the brain increase susceptibility to damage after stroke in sleep and attenuate treatment effectiveness during the active phase. This review underscores the importance of considering circadian biology for understanding the pathology and treatment choice for stroke and vascular dementia and speculates that considering a patient’s chronotype may be an important factor in developing precision treatment following stroke.

Introduction: Ischemia/reperfusion (I/R) injury occurs after coronary revascularization, contributing to infarct size. Circulating mitochondrial DNA (mtDNA) levels are elevated in acute myocardial infarction (MI) patients, and act as Damage Associated Molecular Patterns (mtDNA DAMP), which are recognized by the Toll-like receptor 9 (TLR9), initiating pro-inflammatory responses. Prior studies have shown that loss of TLR9 prevents I/R injury in isolated mouse hearts. However, mtDNA DAMP levels have not been measured in ST-elevation MI (STEMI) patients, and whether blocking TLR9 in mice can reduce I/R injury remains unknown. Hypothesis: MtDNA DAMP levels serve as markers of STEMI related cardiac injury. Blocking the activation of TLR9 will decrease cardiac I/R injury. Methods: MtDNA DAMP levels in serum were measured pre- and 24 hours post- PCI in 55 STEMI patients and 37 healthy controls by qPCR. To evaluate the role of TLR9 on I/R injury, ODN2088 was used to block TLR9 receptor, wild type and TLR9 germline KO mice were subjected to close-chest I/R surgery with minimal systemic inflammation. The cardiac systolic function and infarct size were assessed. Immune cells were isolated from the injured left ventricle and spleens and detected by flow cytometry. Results: Pre- PCI mtDNA DAMP levels were increased ~200 folds in STEMI patients compared to healthy controls. After PCI, the elevated mtDNA DAMP levels reduced significantly, while the troponin T levels increased, suggesting mtDNA is an early marker of MI. Compared with negative ODN, ODN2088 treatment at reperfusion reduced infarct size and total leukocytes, myeloid cells, neutrophils and TNF-α + cells, and a trend of reduced IL-1β + cells, and there was no difference in IL-6 + cells, total macrophages and residential macrophages. Loss of TLR9 in male and female mice significantly reduced infarct size by ~40% and preserved the systolic function. Meanwhile, there is no difference between genders. Conclusions: Circulating mtDNA DAMP level is an early marker of STEMI and may predict the success of PCI. Blocking the mtDNA DAMP-TLR9 signaling pathway during reperfusion significantly reduces I/R injury, indicating it is a viable therapy to mitigate cardiac I/R injury after prompt coronary revascularization.

Ischemia/reperfusion (I/R) injury after revascularization contributes ∼50% of infarct size and causes heart failure, for which no established clinical treatment exists. β-hydroxybutyrate (β-OHB), which serves as both an energy source and a signaling molecule, has recently been reported to be cardioprotective when administered immediately before I/R and continuously after reperfusion. This study aims to determine whether administering β-OHB at the time of reperfusion with a single dose can alleviate I/R injury and, if so, to define the mechanisms involved. We found plasma β-OHB levels were elevated during ischemia in STEMI patients, albeit not to myocardial protection level, and decreased after revascularization. In mice, compared with normal saline, β-OHB administrated at reperfusion reduced infarct size (by 50%) and preserved cardiac function, as well as activated autophagy and preserved mtDNA levels in the border zone. Our treatment with one dose β-OHB reached a level achievable with fasting and strenuous physical activity. In neonatal rat ventricular myocytes (NRVMs) subjected to I/R, β-OHB at physiologic level reduced cell death, increased autophagy, preserved mitochondrial mass, function, and membrane potential, in addition to attenuating reactive oxygen species (ROS) levels. ATG7 knockdown/knockout abolished the protective effects of β-OHB observed both in vitro and in vivo. Mechanistically, β-OHB's cardioprotective effects were associated with inhibition of mTOR signaling. In conclusion, β-OHB, when administered at reperfusion, reduces infarct size and maintains mitochondrial homeostasis by increasing autophagic flux (potentially through mTOR inhibition). Since β-OHB has been safely tested in heart failure patients, it may be a viable therapeutic to reduce infarct size in STEMI patients.

Background: Cardiac fibrosis is pivotal in heart failure progression, where excessive extracellular matrix (ECM) secretion by activated fibroblasts leads to adverse remodeling and dysfunction. While Wnt/β-catenin signaling influences fibroblast activation and cardiac fibrosis post-MI, its precise regulation remains unclear. Emerging evidence suggests N6-methyladenosine (m 6 A) mRNA methylation's role in disease pathology, yet its specific contribution to post-MI cardiac fibrosis is not well understood. Thus, we hypothesized that “ MI-induced METTL3 (a Key m6A mRNA methyltransferase) activation stabilizes δ-catenin mRNA, facilitating cardiac fibrosis and adverse remodeling ”. Methods: The mice underwent sham/MI surgeries for 4 weeks, after which heart tissues were collected for biochemical and histological analysis following heart function measurements. Additionally, methyl-immunoprecipitation followed by RNA sequencing (MeRIP-sequencing) was performed on the heart tissue post-surgery, and the data were analyzed to identify fibrosis-associated targets. Results: Ischemic injury significant increase in m6A mRNA methylation in heart tissues. This increase in m 6 A RNA was also observed in adult cardiac fibroblasts (AMFs) following TGFb treatment. Interestingly, METTL3 inhibition (METTL3 siRNA) resulted in a significant reduction in TGFb-induced periostin and fibronectin gene expression, while METTL3 overexpression enhanced the expression of fibrotic genes in AMFs. To identify differentially regulated m6A target genes, MeRIP-seq was performed on RNA isolated from mice hearts post-MI. The sequencing data suggested hypermethylation of fibrosis-associated genes, including δ-catenin, post-MI. Notably, TGFb-induced increased δ-catenin mRNA methylation led to δ-catenin mRNA stabilization. In contrast, METTL3 inhibition using siMETTL3 in AMFs and in METTL3 KO mice significantly reduced fibroblast activation and cardiac fibrosis. Conclusion: Our data suggests that hypermethylation of δ-catenin mRNA plays a significant role in the progression of cardiac fibrosis following AMI. Therefore, regulating METTL3 could be a potential therapeutic target for attenuating cardiac fibrosis.