title: Assessment of the relationship between circadian variations of salivary melatonin levels and type I collagen metabolism in postmenopausal obese women.
abstract: BACKGROUND
  Few experimental and clinical studies show that melatonin (MEL) can play a significant part to modulate circadian bone metabolism. On this basis it was suggested that MEL secretion which altered during 24-h in obese women could be of importance to regulate bony mass defect after menopause.
  
  
  OBJECTIVE
  The aim of the study was to prove if there were any connection between changes in 24-h profile of serum MEL levels and circadian metabolism of type I collagen in postmenopausal women with visceral obesity.
  
  
  METHODS
  The relationship of 24-h profile of salivary MEL and circadian metabolism of type I collagen (as assessed by measuring saliva concentrations of carboxyterminal propeptide of type I procollagen--PICP and cross-linked carboxyterminal telopeptide of type I collagen--ICTP) was investigated in 26 women with visceral obesity (33.5 < BMI < 42.1 kg/m(2)) and 18 healthy volunteers with correct body mass (21 < BMI < 24.5 kg/m(2); 0.73 < WHR < 0.76). The specimens were collected at subjects' home at 3 h intervals during a 24 h span. The age range of all subjects was 52-60 years.
  
  
  RESULTS
  In all the obese women studied a tendency to suppress circadian levels of tested biochemical markers of bone metabolism was observed (especially regarding ICTP); those alterations were accompanied by substantial increment in MEL concentrations during the day. Significant and negative correlation was found between values of acrophase MEL and PICP rhythms and both amplitude and acrophase of MEL and ICTP rhythms.
  
  
  CONCLUSIONS
  Our results confirm hypothesis that alterations in MEL concentrations might have a protective effect against postmenopausal loss of bone mass.
authors.affiliation: Department of Clinical Biochemistry, Silesian Medical Academy, Pl. Traugutta 2, 41-800 Zabrze, Poland.
authors.forename: Z
authors.initials: Z
authors.lastname: Ostrowska
authors.forename: B
authors.initials: B
authors.lastname: Kos-Kudla
authors.forename: B
authors.initials: B
authors.lastname: Marek
authors.forename: E
authors.initials: E
authors.lastname: Swietochowska
authors.forename: J
authors.initials: J
authors.lastname: Górski
mesh_terms: D001824:Body Constitution; D015992:Body Mass Index; D001842:Bone and Bones / Q000378:metabolism; D002940:Circadian Rhythm; D003094:Collagen / Q000032:analysis / Q000378:metabolism*; D024042:Collagen Type I; D005260:Female; D006801:Humans; D008550:Melatonin / Q000032:analysis*; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control; D010446:Peptide Fragments / Q000032:analysis; D010455:Peptides / Q000032:analysis; D017698:Postmenopause; D011347:Procollagen / Q000032:analysis; D012463:Saliva / Q000737:chemistry*
chemical_list: D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D003094:Collagen; D008550:Melatonin