Follistatin Attenuates Myocardial Fibrosis In Diabetic Cardiomyopathy Via TGFβ-Smad3 Pathway

Background and objective—As one of the most common public health problems around the world,diabetes is associated with cardiovascular complications,which is the leading cause of mortality in diabetic patients.As a common pathological feature,fibrosis is involved in the pathophysiological progress of diabetic cardiomyopathy.As an endogenous protein,Follistatin(FST)is widely distributed in various tissues.Follistatin could inhibit the transforming growth factor beta(TGF-β)superfamily irreversibly and plays an anti-fibrosis role in other diseases.Previous studies on follistatin have mostly focused on skeletal muscle development,embryonic development,fat cell browning,energy metabolism,etc.However,the relationship between follistatin and diabetic cardiomyopathy is rarely reported.This study aims to explore the relationship between follistatin and diabetic cardiomyopathy and the role of follistatin in the pathogenesis of diabetic cardiomyopathy.Methods—Recombinant adeno-associated virus type 9 combined with cardiac Troponin T promoter were used to increase follistatin expression in the heart of db/db mice,which is the model of diabetic cardiomyopathy.Mice were randomly divided into four groups(BKS+AAV9-GFP 、 BKS+AAV9-FST 、 db/db+AAV9-GFP 、 db/db+AAV9-FST).Hematoxylin-eosin staining and Picro Sirius Red Staining were used to detect the shape and structure of cardic paraffin section.Cardiac structure and functions were determined by echocardiography and hemodynamic analysis.The activity of matrix metalloproteinase2 and matrix metalloproteinase 9 were detected by gelatin zymography.The changes of related molecules at the RNA level are detected by RT-PCR(reverse transcription-polymerase chain reaction);the changes of related molecules at the protein level are detected by Western blot.DHE(dihydroethidium)staining detects the level of oxidative stress in heart slices;ELISA(enzyme-linked immunosorbent assay)detects the expression of follistatin in serum and tissues.Results—A significant reduction of follistatin were observed in the serum of patients with diabetic cardiomyopathy and in the heart of db/db mice.Remarkably,overexpressing follistatin efficiently protected against cardiac dysfunction,represented by increased E/A ratio、d P/dt max and d P/dt min rate.In addition,although increasing the content of follostatin in the heart promoted myocardial hypertrophy,the expression levels of molecules related to pathological myocardial hypertrophy did not change,while molecules related to physiological myocardial hypertrophy increased significantly.Furthermore,follistatin reduces cardiac fibrosis and enhanced MMP9 activity in db/db mice.We also observed that overexpressing follistatin decreased the level of TGFβsuperfamily and the phosphorylation of Smad3,consistently,experiments in vitro also verify above results.Moreover,increasing the content of follostatin in the heart can not only reduce the oxidative stress level in the heart of diabetic mice,but also reduce the uptake,synthesis andβ-oxidation of fatty acids in the heart of diabetic mice.Conclusion—Our findings revealed a cardioprotective role of follistatin in reducing the heart damage in diabetic cardiomyopathy by its anti-fibrosis effects through TGFβ-Smad3 pathway.