title: Bone resorption is induced on the second day of bed rest: results of a controlled crossover trial.
abstract: The aim of the study was to analyze the kinetics of short-term changes in bone turnover. We studied in a randomized crossover design the effects of 6 days of bed rest on eight healthy male subjects (mean body wt: 70.1 +/- 5.7 kg; mean age: 25.5 +/- 2.9 yr). The metabolic ward period was divided into three parts: 4 ambulatory days, 6 days of either bed rest or non-bed rest periods, and 1 recovery day. The diet was identical in both bed rest and non-bed rest phases. Continuous urine collection started on the first day in the metabolic ward to analyze excretion of bone resorption markers, namely C-telopeptide (CTX) and N-telopeptide (NTX), creatinine, urea, and 3-methylhistidine. On the second ambulatory day and on the fifth day of bed rest or during the non-bed rest phase, blood was drawn to analyze bone formation markers and amino acid concentrations. Urinary calcium excretion was increased as early as the first day of bed rest (P < 0.01). CTX and NTX excretion stayed unchanged during the first 24 h of bed rest compared with the non-bed rest period. However, already on the second day, both resorption markers had increased significantly. NTX excretion increased by 28.7 +/- 14.0% (P < 0.01), whereas CTX excretion rose by 17.8 +/- 8.3% (P < 0.001). Creatinine, urea, and 3-methylhistidine excretion did not change. We conclude that 24 h of bed rest are sufficient to induce a significant rise in osteoclast activity in healthy subjects.
authors.affiliation: German Aerospace Center-Institute of Aerospace Medicine, Linder Hoehe, 51170 Cologne, Germany.
authors.forename: Natalie
authors.initials: N
authors.lastname: Baecker
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Tomic
authors.forename: Claudia
authors.initials: C
authors.lastname: Mika
authors.forename: Andrea
authors.initials: A
authors.lastname: Gotzmann
authors.forename: Petra
authors.initials: P
authors.lastname: Platen
authors.forename: Rupert
authors.initials: R
authors.lastname: Gerzer
authors.forename: Martina
authors.initials: M
authors.lastname: Heer
mesh_terms: D000328:Adult; D000601:Amino Acids, Essential / Q000378:metabolism; D001510:Bed Rest / Q000009:adverse effects*; D015415:Biomarkers; D001835:Body Weight / Q000502:physiology; D001862:Bone Resorption / Q000473:pathology*; D002118:Calcium / Q000652:urine; D003094:Collagen / Q000652:urine; D024042:Collagen Type I; D003404:Creatinine / Q000652:urine; D018592:Cross-Over Studies; D004032:Diet; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007700:Kinetics; D008297:Male; D008762:Methylhistidines / Q000652:urine; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology; D010455:Peptides / Q000652:urine; D013997:Time Factors; D014508:Urea / Q000652:urine; D014563:Urodynamics / Q000502:physiology
chemical_list: D000601:Amino Acids, Essential; D015415:Biomarkers; D024042:Collagen Type I; D008762:Methylhistidines; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014508:Urea; D003094:Collagen; D003404:Creatinine; C028118:3-methylhistidine; D002118:Calcium