The Mechanism Of KLF7/PFKL/ACADL Axis Regulating Cardiac Metabolic Remodelling During Cardiac Hypertrophy

The cardiac preference for metabolic substrates changes throughout the life cycle and under physiological and pathological stress.The fetal heart primarily utilizes glycolysis,while the fatty acid oxidation of the heart is the main source of ATP production in the transition to adulthood.In the pathological process of cardiac hypertrophy and heart failure(HF),the substrate of the myocardium gradually changes to the embryonal mode,and the cardiac fatty acid oxidation(FAO)capacity decreases and more dependence on glycolysis.The causal correlation between energy metabolism disorders and cardiac hypertrophy has long been controversial,which is essential for clinical research on its treatment options.However,the close association between energy metabolism and its mechanism leading to cardiac pathological remodeling remains unclear.The role of transcriptional regulatory mechanisms in metabolic remodeling has received increasing attention.Krüppel-like factors(Klfs)play an important role in myocardial hypertrophy and cardic metabolism.Krüppel-like factor 7(Klf7),as one of its members,is related to cardiovascular disease and is one of the core transcription factors regulating pathways related to coronary artery disease.The role of Klf7 in cardiomyopathy and cardiac metabolism has not been elucidated.This study revealed that Klf7 can simultaneously transcriptionally regulate the expression of metabolic enzymes to affect the balance of glycolysis and FAO metabolism in the heart and participate in the occurrence and development of pathological cardiac hypertrophy.In this study,we analyzed single cell sequencing database of patients with dilated cardiomyopathy,and found that Klf7 may be closely associated with cardiomyopathy.Then,in vivo and in vitro levels of cardiac hypertrophy,we determined that cardiac hypertrophy stimulated the downregulation of Klf7 m RNA and protein levels.In order to clarify the role of Klf7 in cardiac hypertrophy,we constructed mouse models of myocardial specific knockout and overexp ression of Klf7.Adult mice with myocardial specific knockout of Klf7 gradually developed concentric cardiac hypertrophy and HF,and infant mice with myocardial specific overexpression of Klf7 showed pathological phenotypes of eccentric cardiac hypertrophy and HF.In order to elucidate the specific molecular mechanism of Klf7 in cardiac hypertrophy,we used Ch IP-seq to analyze the target genes of Klf7,which mainly enriched the glucose and fatty acid metabolic pathway.Phosphofructokinase(PFK)activity and Acyl-co A dehydrogenase(CAD)activity were regulated by Klf7.Moreover,the results of double luciferase reporter gene assay and Ch IP-PCR assay were further clarified that Klf7 can negatively regulate liver isoform Phosphofructokinase(Pfkl)and positively regulate Acadl(long chain Acyl-co A dehydrogenase(Acadl).In addition,it was found that m RNA and protein levels of Pfkl and Acadl were up-regulated and down-regulated in both in vivo and in vitro models of cardiac hypertrophy.Overexpression of Pfkl or knockdown of Acadl could directly lead to changes in glycolysis and FAO capacity in cardiomyocytes,and thus induce the development of cardiomyocyte hypertrophy.Finally,we demonstrated that the up-regulated expression of Pfkl and down-regulated expression of Acadl in the hearts of adult myocardial specific knockout Klf7 mice resulted in enhanced glycolysis capacity and decreased FAO capacity,resulting in a pathological phenotype of concentric cardiac hypertrophy and HF.Conversely,the expression of Pfkl was down-regulated and Acadl was up-regulated in the hearts of young mice with specific myocardial overexpression of Klf7,resulting in significant inhibition of glycolysis and enhancement of FAO capacity,resulting in the pathological phenotype of eccentric cardiac hypertrophy and HF.To verify whether KLF7/PFKL/ACADL axis regulates cardiac hypertrophy in vivo and in vitro,in the presence or absence of Ang II stimulation,knockdown of Klf7 in cardiomyocytes can directly significantly up-regulate the expression of hypertrophy genes,followed by knockdown of Pfkl or overexpression of Acadl or both can effectively alleviate the hypertrophic growth of cardiomyocytes caused by Klf7 knockdown.At the animal level,adeno-associated virus was injected into the tail vein of Klf7 knockout mice to achieve myocardial specific Pfkl knockdown and Acadl overexpression.Pfkl knockdown or Acadl overexpression significantly improved cardiac systolic dysfunction in Klf7 knockout mice,and partially restored the imbalance of myocardial glycolysis and FAO metabolism.Moreover,the phenomenon of myocardial fibrosis and cardiomyocytes hypertrophy was also effectively restored.These results suggest that Klf7 may be involved in the regulation of the pathological process of cardiac hypertrophy by simultaneously regulating the expression of Pfkl and Acadl to affect the glycolysis and FAO balance of the heart.In summary,we reveal the key transcriptional regulatory role of Klf7 in pathological cardiac hypertrophy and cardic metabolism,which can simultaneously inhibit the expression of glycolysis and activate the expression of FAO related genes and mediate the pathological process of cardiac hypertrophy,and both myocardial specific knockout and overexpression of Klf7 can induce pathological cardiac hypertrophy and HF.The KLF7/PFKL/ACADL axis is a key regulatory mechanism that may provide feasible insights and therapeutic targets for the treatment of metabolic balance in hypertrophic and failing hearts.