Long-term voluntary exercise of male mice induces more beneficial effects on cancellous and cortical bone than on the collagenous matrix

Hanna Isaksson , Viivi Tolvanen , Mikko A.J. Finnilä , Jarkko Iivarinen , Antti Turunen , Tuomo S. Silvast , Juha Tuukkanen , Kari Seppänen , Jari P.A. Arokoski , Pieter A. Brama , Jukka S. Jurvelin , Heikki J. Helminen

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 the present 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 3-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.

Mots clés: Collagen; Rodent; Mechanical properties; Running; Sedentary

Hanna Isaksson, Viivi Tolvanen, Mikko A.J. Finnilä, Jarkko Iivarinen, Antti Turunen, et al.. Long-term voluntary exercise of male mice induces more beneficial effects on cancellous and cortical bone than on the collagenous matrix. Experimental Gerontology, 2009, 44 (11), pp.708. ⟨10.1016/j.exger.2009.08.005⟩. ⟨hal-00536002⟩