Myocardial infarction in diabetic rats: role of hyperglycaemia on infarct size and early expression of hypoxia-inducible factor 1.
OBJECTIVE
This study aimed to evaluate the effects of hyperglycaemia on the evolution of myocardial infarction and the expression of the transcriptional factor for angiogenesis hypoxia-inducible factor 1alpha (HIF-1alpha) in the rat.


METHODS
We studied the effects of streptozotocin induced diabetes on infarct size and HIF-1 alpha gene expression. These parameters were also evaluated in isolated hearts of non-diabetic rat, in condition of high glucose concentration.


RESULTS
In streptozotocin (STZ)-diabetic rats (in vivo study), myocardial infarct size was greater (p<0.01) in hyperglycaemic rats (22 mmol/l) than in normoglycaemic (7 mmol/l) or non-diabetic rats. In euglycaemic conditions, basal expression of HIF-1alpha mRNA was not appreciable, but increased steadily after ischaemia (762+/-86%, p<0.001); this response was blunted in hyperglycaemic STZ-rats (6.8+/-6% of the control, p<0.001) and improved in euglycaemic STZ-rats (58+/-10%). The changes in myocardial Rac1 mRNA expression paralleled those of HIF-1alpha. In isolated hearts from non-diabetic rats (in vitro study), perfusion with high glucose (33 mmol/l) produced an infarct size (58+/-2% of the area at risk) not different from that obtained in hyperglycaemic STZ-rats (57+/-2%). Similar changes in the expression of HIF-1alpha and Rac1, which were prevented by glutathione infusion (0.3 mmol/l) were also observed.


CONCLUSIONS
Both hyperglycaemia and high glucose concentrations increased basal HIF-1alpha and Rac1 expression, suggesting a state of pseudohypoxia. These findings show that myocardial infarct size in the rat is increased in hyperglycaemic conditions and is associated with a reduced expression of the HIF-1alpha gene. These changes are reversed, totally or partially, by normoglycaemia or glutathione suggesting a role for reactive oxygen species generation brought about by hyperglycaemia.
Department of Geriatrics and Metabolic Diseases, Second University of Naples, Italy. raffaele.marfella@unina2.it
R
R
Marfella
M
M
D'Amico
C
C
Di Filippo
E
E
Piegari
F
F
Nappo
K
K
Esposito
L
L
Berrino
F
F
Rossi
D
D
Giugliano
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000378:metabolism* / Q000473:pathology*; D006439:Hemodynamics; D006943:Hyperglycemia / Q000209:etiology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008297:Male; D009203:Myocardial Infarction / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D014157:Transcription Factors; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D001786:Blood Glucose; D004268:DNA-Binding Proteins; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D014157:Transcription Factors; D020830:rac1 GTP-Binding Protein