title: Relation of nocturnal melatonin levels to serum matrix metalloproteinase-9 concentrations in patients with myocardial infarction.
abstract: BACKGROUND
  The aims of the present study were to characterize the day/night variation of matrix metalloproteinase (MMP)-9 in patients who have developed ST-segment elevation myocardial infarction (STEMI), in response to light/dark differences in circulating melatonin and to assess whether melatonin, a day/night variation regulator, modulates the nocturnal inflammatory changes in patients who have STEMI.
  
  
  METHODS
  The study included 75 patients diagnosed with STEMI and 75 control subjects. Each subject was studied under strictly controlled light/dark conditions. Blood samples for measurement of MMP-9 and melatonin were collected at 09:00 a.m. (light period) and 02:00 a.m. (dark period).
  
  
  RESULTS
  In patients with STEMI, melatonin concentrations maintained a light/dark variation but the difference between nocturnal and diurnal levels was smaller than that in controls (p<0.001). In contrast to melatonin, serum MMP-9 concentrations showed no day/night variation in control subjects. MMP-9 concentrations were significantly higher in patients with STEMI than in control subjects. In the STEMI subjects, MMP-9 serum concentrations in the light period were significantly higher than those during the dark phase (291.1+/-59.5 vs. 261.8+/-57.8 ng/ml, p<0.01). Furthermore in the control subjects there was no correlation between MMP-9 and melatonin levels, while in the STEMI group there was a significant correlation between these parameters (Pearson's r=0.40, p<0.0004).
  
  
  CONCLUSIONS
  Our results suggest that the light/dark variations in endogenous MMP-9 production in patients who have STEMI might be associated, at least in part, to the day/night variation of melatonin.
authors.affiliation: Coronary Care Unit, Department of Cardiology, Hospital Universitario de Canarias, La Laguna, Tenerife, Spain. adrvdg@hotmail.com
authors.forename: Alberto
authors.initials: A
authors.lastname: Dominguez-Rodriguez
authors.forename: Pedro
authors.initials: P
authors.lastname: Abreu-Gonzalez
authors.forename: Martín J
authors.initials: MJ
authors.lastname: Garcia-Gonzalez
authors.forename: Russel J
authors.initials: RJ
authors.lastname: Reiter
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000097:blood*; D008550:Melatonin / Q000378:metabolism*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000378:metabolism*
chemical_list: D020780:Matrix Metalloproteinase 9; D008550:Melatonin