Research On The Mechanism Of FIT1 In Myocardial Energy Metabolism

Objective(s): In the process of myocardial metabolism,a large number of fatty acids(FA)are used as substrates to provide energy.The neutral lipid stored in lipid droplets(LD)is the main energy source of myocardial metabolism.LD is mainly composed of a monolayer of phospholipids and a neutral core,with lipid droplet associated proteins(LDAPs)embedded on the surface to regulate intracellular lipid metabolism.LDAPs are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism.including the fat storage-induced transmembrane protein(FIT)family.FIT family is a highly conserved transmembrane protein located in the ER,which is critical for LDs budding from the ER.The FIT family has two members,FIT1 and FIT2.FIT1 is mainly expressed in oxidized tissues(skeletal muscle,myocardium,etc.),producing small LD;However,the expression of FIT2 is g highly expressed in adipose tissues,resulting in large LD.Since the abundance of FIT1 in myocardium,and the small size of LD in myocardial cells which is closely associated with mitochondria,we speculate that FIT1 may play an important role in linking the triglyceride(TAG)energy pool of myocardial cells with mitochondrial respiration.Further,this linkage plays an important role in maintaining the energy homeostasis of myocardial tissue.However,the details of regulation of myocardial energy metabolism via FIT1 is not clear.Therefore,we further explored the role of FIT1 in myocardial energy metabolism and its regulatory mechanism.Methods: Firstly,we constructed a cell model(H9C2,HL1)of FIT1 overexpression under normal and abnormal myocardial energy metabolism(diabetic cardiomyopathy),and analyzed it by staining(Bodipy,Mitotracker,etc.),q PCR and western blot.Next,we successfully constructed normal model(CD)and diabetic cardiomyopathy(DCM)myocardial tissue-specific FIT1 knock-in(KI)mice by using Myh6-cre tool mice.By counting the weight,blood glucose,GTT,ITT,running wheel detection,staining(HE,oil red O staining),western blot and other methods,we explored the influence of increased expression of FIT1 on myocardial metabolism in normal and diabetic cardiomyopathy models.Results: Over-expression of FIT1 promotes the oxidation and absorption of LD in both normal and diabetic cardiomyopathy models.However,the effect in normal and diabetic cardiomyopathy models are inconsistent.Under normal treatment,over-expression of FIT1 leads to LD accumulation,abnormal mitochondrial morphology and impaired function;On the contrary,in the model of diabetic cardiomyopathy,FIT1 overexpression can improve the LD accumulation and mitochondrial damage caused by the disease,which may be related to the change of the ratio of energy metabolism substrate-glucose and lipid utilization in normal and pathological conditions.Conclusion(s): FIT1 regulates the absorption and oxidation of LD in myocardium,and then regulates the quantity and function of LD,revealing the important role of FIT1 in the process of myocardial energy metabolism,and providing a new idea for further study of myocardial metabolism-related diseases.