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

Abstract

Background: The pathophysiology of age-related bone loss and whether age-related bone loss can be prevented by exercise are still a matter of debate. Objective: It was the aim of this study to investigate the long-term effects of exercise and mild food restriction on bone mineral density (BMD) and bone geometry in the appendicular skeleton of aging male rats. Methods: Male Sprague-Dawley rats were studied from 5 to 23 months of age. The rats were divided into 4 groups: baseline, free access to food and running wheels (RW), fed to pair weight with the RW group (PW) and sedentary control animals with free access to food (SED). All rats were housed individually. Volumetric BMD and geometry of femurs and tibiae were assessed by peripheral quantitative computed tomography (pQCT). In addition, the tibial shafts were analyzed by cortical bone histomorphometry. Results: At the end of the experiment, RW and PW rats had similar body weight. The body weight of SED rats was 31% greater than that of RW rats. pQCT analysis of femurs and tibiae as well as histomorphometric analysis of the tibial shafts showed that dietary restriction resulted in an enlargement of the marrow cavity and cortical thinning at the femoral and tibial shafts relative to the RW and SED groups. Voluntary running exercise provided no additional protection against age-related bone loss when compared with the 31% heavier SED control rats. Neither exercise nor increased body weight in SED animals could completely prevent age-related bone loss between 19 and 23 months of age. Conclusion: We conclude that dietary restriction had clear negative effects on BMD and bone geometry and that running wheel exercise provided partial protection but could not prevent age-related bone loss.

Hypothalamic leptin gene therapy reduces body weight without accelerating age-related bone loss

“…The trend for age-related cancellous bone loss observed in femur and lumbar vertebra in the present study is consistent with previous results where significant bone loss is noted between 8 months and 2 years of age (Turner et al 2013a; Turner, et al 2001). Caloric restriction accelerates age-related cancellous bone loss (Bodnar, et al 2012; Mardon, et al 2008a; Mardon, et al 2008b), a finding consistent with the hypothesis that a decrease in leptin levels in the context of low energy availability contributes to bone loss. Leptin treatment, in spite of drastically reducing body weight in growing ob/ob mice, results in increased longitudinal bone growth, increased bone formation, increased bone resorption, a net increase in bone mass and normalization of bone microarchitecture (Bartell et al 2011; Hamrick, et al 2005; Iwaniec, et al 2007; Turner et al 2013b).…”

Calorie restriction in rodents: Caveats to consider

“…As an example, Bodnar et al examined bone quality in male SD rats exercised in running wheels from 5 mo of age compared to a CR group fed to maintain the body weight of exercised rats (Bodnar et al, 2012). At 23 mo of age, the CR group had cortical thinning of femoral and tibial shafts compared to non-exercised controls.…”

Food Restriction Causes Low Bone Strength and Microarchitectural Deterioration in Exercised Growing Male Rats

“…androgen) essential for skeletal acquisition (12). However, few studies have examined the influence of a combination of food restriction and exercise training on bone strength and morphology using male animals (16), although many studies have examined either the effect of food restriction on bone tissue (15,17), or the effect of mechanical loading accompanied with physical activity on bone tissue (8,18). We reported that the BMD and the bone architecture had been little affected by food restriction combined with exercise training in mature male rats (19).…”