| OBJECTIVE: The aim of this study is to investigate the effects of exercise,metformin,and the the combination intervention on myocardial fibrosis in db/db mice and their molecular mechanisms based on AMPK,NF-κB and TGF-β1/Smad signaling pathways,and to investigate whether there is a superimposed effect of the combined intervention.METHODS: Ten BKS mice were quiet control group(WT,n=10),and 40 BKSdb/db mice were randomly divided into four groups: diabetic control group(C,n=10),exercise group(E,n=10),metformin group(M,n=10),and exercise combined with metformin group(EM,n=10).After one week of adaptive feeding,mice in the M and EM groups were given intragastric administration of metformin every day,and mice in the E and EM groups were trained with aerobic endurance exercise on a treadmill for 8 weeks(5 days/week).Body weight,fasting blood glucose,and echocardiography were performed during the experiment.The mice were anesthetized and executed after 8 weeks,the tibiae were stripped and the lengths were measured,and the heart and pericardial adipose tissue were collected and weighed.Morphological changes in myocardial tissue were detected by H&E staining,the degree of myocardial fibrosis were detected by Masson staining,the expression of TGF-β1,Collagen I,and Collagen III were detected by immunohistochemistry staining,the expression of α-SMA in the myocardium was detected by immunofluorescence staining,and the Collagen I,Collagen III,α-SMA protein expression,and AMPK,NF-κB and TGF-β1/Smad signaling pathway-related protein expression in the myocardium were detected by Western Blot.RESULTS:(1)In 16-week-old db/db mice,body weight and fasting blood glucose levels were significantly increased,and interstitial fibrosis was observed in the myocardium,while no significant abnormalities were observed in the gross structure and function of the heart.(2)Exercise,metformin,and the combination intervention significantly reduced body weight in db/db mice,and metformin alone significantly reduced fasting blood glucose levels in db/db mice.(3)Exercise,metformin,and the combination intervention significantly reduced the expression levels of myocardial Collagen I,Collagen III,and α-SMA in db/db mice.(4)Exercise,metformin,and the combination intervention significantly reduced the expression of TNF-α and inhibited the activation of NF-κB and TGF-β1/Smad signaling pathways;exercise alone significantly upregulated IL-6expression in the myocardium,while there was no significant difference in the expression of IL-6 after metformin alone and exercise combined with metformin intervention.(5)Metformin alone significantly upregulated myocardial pAMPK/AMPK and decreased HNF4α expression,while no significant differences were found between exercise alone and exercise combined with metformin intervention for myocardial p-AMPK/AMPK and HNF4α.CONCLUSION: In early diabetes,morphological changes in the heart of db/db mice were dominated by interstitial fibrosis without gross structural and functional alterations.Exercise and metformin improved myocardial fibrosis by reducing NF-κB-mediated inflammatory responses and enhancing the inhibition of the TGF-β1/Smad signaling pathway through upregulation of IL-6and activation of AMPK,respectively,whereas the antifibrotic effect of exercise combined with metformin did not show significant synergistic effects. |
