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Exercise-induced cellular changes promote improved function in ischemic hearts

ABSTRACT: Ischemic heart disease (IHD) remains a leading cause of mortality worldwide, often culminating in myocardial infarction (MI) and subsequent heart failure due to adverse fibrotic remodeling of the myocardium. Despite the lack of effective treatments, exercise has emerged as a promising strategy to reduce mortality risk and improve cardiac function post-MI. This study investigates the molecular mechanisms underlying exercise-induced cardioprotection by analyzing changes in several key cardiac cell populations after MI in a murine model. We assessed the effect of exercise preconditioning in mouse MI model through echocardiography, followed by single nuclei RNA-seq of cardiac cells, and validation by microscopy and flow cytometry. Our findings demonstrate that exercise significantly enhances cardiac function post-MI, as evidenced by improved ejection fraction and stroke volume in exercised mice. These improvements are linked to adaptive changes across multiple cardiac cell types. Notably, in infarcted mice, exercise caused a downregulation of cardiomyopathy-associated pathways, accompanied by changes in ECs, macrophages, fibroblasts and cardiomyocytes. Exercise stimulated formation of new capillaries which post-MI resulted in a more vascularized infarct border zone. Additionally, exercised hearts displayed a shift in macrophage populations towards a pro-regenerative phenotype, marked by an increase in resident CCR2- macrophages and a reduction in pro-inflammatory M1-gene expression. In cardiomyocytes, exercise enhanced pathways related to endothelial support and ATP biosynthesis, mitigating the upregulation of cardiomyopathy-associated pathways observed post-MI. Importantly, exercise also restored calcium signaling and reversed pathological potassium signaling, thereby preserving contractile function. Fibroblast analysis revealed that exercise stimulated activation of these cells to participate in scar formation. In conclusion, this study provides new insights into the cellular and molecular mechanisms through which exercise enhances cardiac function and provides cardio-protection post-MI, offering potential avenues for targeted therapies in patients with IHD.

ORGANISM(S): Mus musculus

PROVIDER: GSE277123 | GEO | 2025/09/12

REPOSITORIES: GEO

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Project description:OBJECTIVE: To explore the cardioprotective effects of exercise-derived β-aminoisobutyric (BAIBA) on cardiomyocyte apoptosis and energy metabolism in a rat model of heart failure (HF).METHODS: In male Sprague-Dawley rats (8-week-old), myocardial infarction (MI) was used to induce HF by ligating the left anterior descending branch of the coronary artery. In the Sham group, the coronary artery was threaded but not ligated. After HF development, Sham and HF rats were exercised 60 min daily, 5 days per week on a treadmill for 8 weeks (50-60% maximal intensity) and exercise-induced cardiac remodeling after MI were assessed using echocardiography, hematoxylin and eosin (H&E), Masson’s Trichrome and TUNEL staining for the detection of apoptosis-associated factors in cardiac tissue. High-throughput sequencing and mass spectrometry were used to measure BAIBA production and to explore its cardioprotective effects and molecular actions. To further characterize the cardioprotective effects of BAIBA, an in vitro model of apoptosis was generated by applying H2O2 to H9C2 cells to induce mitochondrial dysfunction. In addition, cells were transfected with either a miR-208b analogue or a miR-208b inhibitor. Apoptosis-related proteins were detected by Western Blotting (WB). ATP production was also assessed by luminometry. After administration of BAIBA and Compound C, the expression of proteins related to apoptosis, mitochondrial function, lipid uptake and β-oxidative were determined. Changes in the levels of reactive oxygen species (ROS) were assessed by fluorescence microscopy. In addition, alterations in membrane potential (δψm) were obtained by confocal microscopy.RESULTS: Rats with HF after MI are accompanied by mitochondrial dysfunction, metabolic stress and apoptosis. Reduced expression of apoptosis-related proteins was observed, together with increased ATP production and reduced mitochondrial dysfunction in the exercised compared with the Sham (non-exercised) HF group. Importantly, exercise increased the production of BAIBA, irrespective of the presence of HF. To assess whether BAIBA had similar effects to exercise in ameliorating HF-induced adverse cardiac remodeling, rats were treated with 75 mg/kg/day of BAIBA and we found BAIBA had a similar cardioprotective effect. Transcriptomic analyses found that the expression of miR-208b was increased after BAIBA administration, and subsequent transfection with an miR-208b analogue ameliorated both the expression of apoptosis-related proteins and energy metabolism in H2O2-treated H9C2 cells. In combining transcriptomic with metabolomic analyses, we identified AMPK as a downstream target for BAIBA in attenuating metabolic stress in HF. Further cell experiments confirmed that BAIBA increased AMPK phosphorylation and had a cardioprotective effect on downstream fatty acid uptake, oxidative efficiency and mitochondrial function, which was prevented by the AMPK inhibitor Compound C.CONCLUSION: Exercise-generated BAIBA can reduce cardiomyocyte metabolic stress and apoptosis induced by mitochondrial dysfunction through the miR-208b/AMPK pathway.

Project description:Aims Ischemic cardiomyopathy with comorbid sleep apnea syndrome (SAS) is associated with worse long-term outcomes. Intermittent hypoxia (IH), a key feature of SAS, exacerbates sympathetic activity, hastening cardiac dysfunction and remodeling in ischemic cardiomyopathy rat models. This study explores whether targeted cardiac sympathetic denervation (CSD) can limit IH-induced progression of ischemic cardiomyopathy. Methods and results Male Wistar rats underwent myocardial infarction (MI) via permanent left coronary artery ligation, and CSD was simultaneously achieved through ablation of the left middle cervical and stellate ganglions. Rats were exposed to IH (21–5% fraction of inspired O2, 60 s cycle, 8 h/day) or normoxia (N) for 14 weeks starting 3 days post-surgery. Throughout the intervention period, cardiac sympathetic activity was assessed using spectral analysis of heart rate variability (HRV) from vigil ECG collected with a specialized jacket. Cardiac function and remodeling were monitored via echocardiography. Additionally, isolated cardiomyocytes from rats exposed to IH or N for 6 weeks were assessed for calcium transient, sarcomere shortening and adrenergic reserve using isoproterenol stimulation (100 nM). CSD reduced cardiac sympathetic activity and prevented IH-induced blunting of cardiomyocyte response to isoproterenol challenge. In hypoxic animals, CSD reduced alterations in long-term ejection fraction and mitigated cardiomyocyte hypertrophy. Transcriptomic analysis unveiled that CSD triggered biological processes related to cardiac repair and regeneration. Immunohistochemistry further supported these findings, demonstrating increased cardiomyocyte proliferation in the hypoxic group, as indicated by elevated Ki67 expression colocalized with MF20 markers. Conclusions Our data demonstrate that cardiac sympathetic denervation prevents IH-induced depletion of cardiac adrenergic reserve and deterioration of cardiac function in a rat model of ischemic cardiomyopathy. This study questions the role of sympathetic activity and hypoxia in cardiac regeneration and on the optimal management of sympathetic hyperactivity in ischemic cardiomyopathy in the specific context of associated SAS.

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Exercise-induced cellular changes promote improved function in ischemic hearts

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