Influence of Physical Exercise and Food Restriction on the Biomechanical Properties of the Femur of Ageing Male Rats

Abstract

Background: Voluntary running in wheels as well as food reduction increase the life spans of rats. Disparate parameters such as the collagen biomarker of ageing and the development of kidney pathologies are decreased by voluntary exercise. There are few reports on the influence of physical exercise and food restriction on the skeleton of male rats. Most investigations initiated rather short-term interventions in 4- to 5-week-old animals and thus studied more the influence of growth than the influence of ageing on the skeleton. Objective: To compare the effects of physical exercise and food restriction on the biomechanical properties of bone tissue of ageing male rats with the interventions starting at the age of 5 months with the end point at 23 months. This enables the study of the influence of these interventions on the ageing of the skeleton. Methods: Five groups of male Sprague-Dawley rats were used: baseline (BL), voluntarily running in wheels (RW), food restriction to attain pair weight with RW animals (PW), forced running in treadmills (TM), and sedentary controls (SE). The biomechanical properties of femoral neck, diaphysis, and distal metaphysis were measured. Results: While the body weights and fat-free mass increased from BL to SE group, the occiput-sacrum length did not increase and the length of the femur increased marginally. These lengths were slightly retarded in RW and PW groups compared to the SE group. The strength of the distal femoral metaphysis decreased from BL to SE group. This decrease was counteracted by physical exercise (RW and TM groups) as well as by food restriction (PW group). In contrast, the strength of the femoral mid-diaphysis did not differ between BL and SE groups. Conclusions: The distal metaphysis in the male rat femur is more prone to decreasing biomechanical strength than the diaphysis during ageing. Physical exercise, when started at the age of 5 months, when the skeleton has reached its adult size, is somewhat effective in counteracting these changes. There is also some retarding effect of food restriction.

Interaction between Exercise, Dietary Restriction and Age-Related Bone Loss in a Rodent Model of Male Senile Osteoporosis

“…However, in accordance with our finding that trabecular BMD at the distal femoral and proximal tibial metaphyses declined precipitously between baseline and the end of the trial, axial compression tests of the distal femoral metaphysis showed a pronounced reduction in bone strength between 5 and 23 months of age in all groups [12] .…”

Chronically inadequate sleep results in abnormal bone formation and abnormal bone marrow in rats

“…17 Not only are the effects of calorie restriction opposite to those of sleep restriction with regard to vital organ masses, but mild calorie restriction alone has been shown to have a beneficial effect on metaphyseal strength, as determined in sedentary, aging rats. 18 Comparisons of the sleep-deprived state with other examples of hypermetabolism also do not provide enough similarities to conclude that energy expenditure during sleep restriction has only a unidirectional effect of on bone formation. For example, hypermetabolism induced by thyroid hormone administration results not only in increased osteoclast surface areas and bone loss, but in increased osteoid and osteoblast surface areas.…”

Perinatal Exposure to Environmental Contaminants Detected in Canadian Arctic Human Populations Changes Bone Geometry and Biomechanical Properties in Rat Offspring

“…Experimental studies showed that rat bone strength increases with age up to 1 yr of age, after which there is a slow reduction in strength as the animal ages (Fukuda and Iida 2004;Thomsen et al 2008). Similarly, human bone strength decreases with age, and this fall is more pronounced than in rats (Mueller et al 2009).…”