title: Long-term voluntary exercise of male mice induces more beneficial effects on cancellous and cortical bone than on the collagenous matrix.
abstract: The effects of lifelong physical exercise on the composition, structure and mechanical properties of bone are not well understood. Earlier, we found that voluntary physical exercise improved various properties of bone in maturing male mice up to 6 months of age. In this study, we extended the previous study to 18 months. Half of the mice (total N=144) had access to running wheels while half were kept sedentary. The collagen network was assessed biochemically and by tensile testing of decalcified bone. The mineralized femur was analyzed with pQCT and three-point-bending of the diaphysis and neck-strength-test. The proximal tibia was analyzed with microCT. The bone collagen revealed inferior tensional properties with aging and the mineralized femur demonstrated decreased stiffness with age. In the running mice, tensile properties and the BMD were reduced at 18 months of age compared to the sedentary mice. In contrast, the stiffness of both the diaphysis and femoral neck was higher, and trabecular architecture and structure were improved in the running mice. In summary, the results suggest that lifelong exercise training of male mice results in more beneficial effects on intact mineralized bone in both the diaphysis and epiphysis than on bone collagenous matrix.
authors.affiliation: Biophysics of Bone and Cartilage, Department of Physics, University of Kuopio, Kuopio, Finland. hanna.isaksson@uku.fi
authors.forename: Hanna
authors.initials: H
authors.lastname: Isaksson
authors.forename: Viivi
authors.initials: V
authors.lastname: Tolvanen
authors.forename: Mikko A J
authors.initials: MA
authors.lastname: Finnilä
authors.forename: Jarkko
authors.initials: J
authors.lastname: Iivarinen
authors.forename: Antti
authors.initials: A
authors.lastname: Turunen
authors.forename: Tuomo S
authors.initials: TS
authors.lastname: Silvast
authors.forename: Juha
authors.initials: J
authors.lastname: Tuukkanen
authors.forename: Kari
authors.initials: K
authors.lastname: Seppänen
authors.forename: Jari P A
authors.initials: JP
authors.lastname: Arokoski
authors.forename: Pieter A
authors.initials: PA
authors.lastname: Brama
authors.forename: Jukka S
authors.initials: JS
authors.lastname: Jurvelin
authors.forename: Heikki J
authors.initials: HJ
authors.lastname: Helminen
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology*; D001846:Bone Development / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005272:Femur Neck / Q000033:anatomy & histology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010805:Physical Conditioning, Animal / Q000502:physiology; D012420:Running / Q000502:physiology
chemical_list: D003094:Collagen