Abstract: Objective:To observe the occurrence of myocardial fibrosis and the change of MMP-14 in different courses of diabetic rats and analyze the possible mechanism.Methods:All male Sprague Dawley(SD) rats were randomly divided into five groups(n=6):control group(CON),high glucose and high caloric group(HC) group and type 2 diabetes mellitus groups at 4-week(DM4w),8-week(DM8w) and 12-week(DM12w).Plasma triglyceride (TG),total cholesterol(TC) and fasting blood glucose (FBG) levels were measured,body weight (BW),the ratio of heart weight/body weight(H/B),left ventricular weight index(LVWI) levels were calculated.The myocardial morphological and fibrotic changes were discovered by HE and Masson staining methods.The contents of col Ⅰ and col Ⅲ in heart tissue were evaluated by ELISA and the ratio of colⅠ/col Ⅲ was calculated.The protein expressions of MMP-14 and col Ⅰ were measured by Western blotting.Results:Compared with CON group,plasma TG and TC levels increased significantly in HC and DM groups.The FBG level increased in DM groups.With the course of diabetes extended,FBG,H/B,LVWI and plasma TG and TC levels further increased.HE staining showed cardiac cells were arranged irregularly and fractures were not continuous in DM groups,Masson staining showed that a large amount of interstitial collagen fiber hyperplasia,collagen accumulation or uneven distribution appeared in DM groups.The contents of col Ⅰ,col Ⅲ,the ratio of col Ⅰ/col Ⅲ and the protein expressions of col Ⅰ and MMP-14 in myocardial tissue were further increased with the extension of diabetes course.Conclusions:Type 2 diabetes can induced the happening of myocardial fibrosis,the fibrosis degree will gradually aggravated with the course of diabetes extended.The mechanism may be related to the continuously increase of the expression of MMP-14 in myocardium.