Reduced MMP-2 activity contributes to cardiac fibrosis in experimental diabetic cardiomyopathy.
OBJECTIVE
To evaluate the regulation of matrix metalloproteinase (MMP)-2 in diabetic cardiomyopathy.


METHODS
Left ventricle (LV) function was determined by a micro-tip catheter in streptozotocin (STZ)-induced diabetic rats, 2 or 6 weeks (w) after STZ-application. LV total collagen, collagen type I and III content were immunohistologically analyzed and quantified by digital image analysis. LV collagen type I, III and MMP-2 mRNA expression was quantified by real-time RT-PCR. LV pro- and active MMP-2 levels were analyzed by zymography; Smad 7, membrane type (MT)1-MMP and tissue inhibitor metalloproteinase (TIMP)-2 protein levels by Western Blot.


RESULTS
STZ-induced diabetes was associated with a time-dependent impairment of LV diastolic and systolic function. This was paralleled by a time-dependent increase in LV total collagen content, despite reduced LV collagen type I and III mRNA levels, indicating a role of post-transcriptional/post-translational changes of extracellular matrix regulation. Six weeks (w) after STZ-injection, MMP-2 mRNA expression and pro-MMP-2 levels were 2.7-fold (P < 0.005) and 1.3-fold (P < 0.05) reduced versus controls, respectively, whereas active MMP-2 was decreased to undetectable levels 6 w post-STZ. Concomitantly, Smad 7 and TIMP-2 protein levels were 1.3-fold (P < 0.05) and 10-fold (P < 0.005) increased in diabetics versus controls, respectively, whereas the 45 kDa form of MT1-MMP was undetectable in diabetics.


CONCLUSIONS
Under STZ-diabetic conditions, cardiac fibrosis is associated with a dysregulation in extracellular matrix degradation. This condition is featured by reduced MMP-2 activity, concomitant with increased Smad 7 and TIMP-2 and decreased MT1-MMP protein expression, which differs from mechanisms involved in dilated and ischemic heart disease.
Van Linthout
Sophie
S
Dept. of Cardiology and Pneumology, Charité-University Medicine Berlin, Campus Benjamin Franklin Hindenburgdamm 30, 12200, Berlin, Germany.
Seeland
Ute
U
Riad
Alexander
A
Eckhardt
Oleg
O
Hohl
Mathias
M
Dhayat
Nasser
N
Richter
Utz
U
Fischer
Jens W
JW
Böhm
Michael
M
Pauschinger
Matthias
M
Schultheiss
Heinz-Peter
HP
Tschöpe
Carsten
C
D000818:Animals; D009202:Cardiomyopathies / Q000201:enzymology / Q000473:pathology*; D003094:Collagen / Q000378:metabolism; D048909:Diabetes Complications / Q000201:enzymology / Q000473:pathology*; D003921:Diabetes Mellitus, Experimental / Q000150:complications* / Q000201:enzymology / Q000473:pathology; D005355:Fibrosis; D008297:Male; D053511:Matrix Metalloproteinase 14 / Q000032:analysis; D020778:Matrix Metalloproteinase 2 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics; D009206:Myocardium / Q000473:pathology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D051906:Smad7 Protein / Q000032:analysis; D013311:Streptozocin; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000032:analysis
D012333:RNA, Messenger; D051906:Smad7 Protein; C497808:Smad7 protein, rat; D016212:Transforming Growth Factor beta; D019716:Tissue Inhibitor of Metalloproteinase-2; D013311:Streptozocin; D003094:Collagen; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D053511:Matrix Metalloproteinase 14