title: PTH Signaling During Exercise Contributes to Bone Adaptation.
abstract: Improving the structural integrity of bone reduces fracture risk and development of osteoporosis later in life. Exercise can increase the mechanical properties of bone, and this increase is often attributed to the dynamic loading created during exercise. However, the increase in systemic parathyroid hormone (PTH) levels during exercise gives reason to hypothesize that PTH signaling also regulates bone adaptation in response to exercise. Therefore, the first aim of this study was to establish the impact PTH signaling has on bone adaptation during exercise by inhibiting PTH signaling with PTH(7-34); the second aim was to determine whether increasing PTH levels during exercise with PTH(1-34) can augment bone adaptation. Thirty minutes after a single bout of running on a treadmill, mice exhibited a twofold increase in systemic PTH levels. Under the same exercise regimen, the influence of PTH signaling on bone adaptation during exercise was then evaluated in mice after 21 consecutive days of exercise and treatment with PTH(7-34), PTH(1-34), or vehicle. Exercise alone caused a significant increase in trabecular bone volume with adaptation to a more platelike structure, which was inhibited with PTH(7-34) during exercise. Changes in structural-level and tissue-level mechanical properties during exercise occurred in the absence of significant changes to cortical bone geometry. Inhibition of PTH signaling during exercise attenuated the changes in structural-level mechanical properties, but not tissue-level properties. Enhanced PTH signaling during exercise with PTH(1-34) increased trabecular and cortical bone volume, but had little effect on the structural-level and tissue-level mechanical properties compared to exercise alone. Our study is the first to demonstrate that bone adaptation during exercise is not only a function of dynamic loading, but also PTH release, and that PTH signaling contributes differently at the structural and tissue levels.
authors.affiliation: Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Gardinier
authors.affiliation: Oral Health Sciences Program, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Fatma
authors.initials: F
authors.lastname: Mohamed
authors.affiliation: Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA.|Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Kohn
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001846:Bone Development / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology / Q000378:metabolism*; D008297:Male; D051379:Mice; D009929:Organ Size / Q000502:physiology; D010281:Parathyroid Hormone / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; C058350:parathyroid hormone (7-34)
keywords: ANABOLICS; ANALYSIS/QUANTITATION OF BONE; BIOMECHANICS; EXERCISE; PTH