Voluntary exercise and mild food restriction effectively retard the collagen biomarker of aging

Effect of training and sudden detraining on the patellar tendon and its enthesis in rats

Background

Different conditions may alter tendon characteristics. Clinical evidence suggests that tendon injuries are more frequent in athletes that change type, intensity and duration of training. Aim of the study was the assessment of training and especially detraining on the patellar tendon (PT) and its enthesis.

Methods

27 male adult Sprague-Dawley rats were divided into 3 groups: 20 rats were trained on a treadmill for 10 weeks. Of these, 10 rats were euthanized immediately after training (trained group), and 10 were caged without exercise for 4 weeks before being euthanized (de-trained group). The remaining 7 rats were used as controls (untrained rats). PT insertion, structure (collagen fiber organization and proteoglycan, PG, content), PT thickness, enthesis area, and subchondral bone volume at the enthesis were measured by histomorphometry and microtomography.

Results

Both PG content and collagen fiber organization were significantly lower in untrained and detrained animals than in trained ones (p < 0.05 and p < 0.0001). In the detrained group, fiber organization and PG content were worse than that of the untrained groups and the untrained group showed a significantly higher score than the detrained group (p < 0.05). In the trained group, the PT was significantly thicker than in untrained group (p < 0.05). No significant differences in the enthesis area and subchondral bone volume among the three groups were seen.

Conclusions

Moderate exercise exerts a protective effect on the PT structure while sudden discontinuation of physical activity has a negative effect on tendons. The present results suggest that after a period of sudden de-training (such as after an injury) physical activity should be restarted with caution and with appropriate rehabilitation programs.

Running has a negative effect on bone metabolism and proinflammatory status in male aged rats

Animal models for male osteoporosis are scarce. This study aimed at identifying the impact of different living conditions on bone structure and metabolism as well as the inflammatory status in a rat model of age-related male osteoporosis. Bone mineral density, bone histomorphometric data, ex vivo osteoclast generation, and bone metabolism serum marker as well as intracellular cytokine expressions were evaluated in 23-month-old male Sprague-Dawley rats subjected to different housing conditions from the age of 5 months. Running rats were housed individually and were exercised voluntarily in running wheels attached to their cages. Dieting rats were housed individually, too, but were fed to pair weight with the running rats. Walking rats were exercised mildly by use of a treadmill (800m/day, 5 days a week) and social rats were kept as four in a cage and fed ad libitum. Whereas no marked differences could be found for bone mineral density, trabecular bone volume as well as trabecular bone surface were diminished in walking rats. The ex vivo osteoclast generation assay revealed no significant differences between groups. Osteoblasts of running rats were not only decreased in number, but displayed also a lower activity as indicated by decreased serum osteocalcin levels. Osteoclast activity was increased in the same group as indicated by elevated CTX (c-terminal telopeptide of type I collagen) levels. Additionally, production of tumor necrosis factor (TNF)-alpha and interferone (IFN)-gamma by CD8(+) T cells was elevated in running rats. In conclusion, running has a negative effect on bone metabolism and proinflammatory status in male aged rats.

Influence of physical exercise and food restriction on the biomechanical properties of the femur of ageing male rats

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.

Impact of moderate physical exercise--in comparison with dietary restrictions--on age-associated decline in cell-mediated immunity of Sprague-Dawley rats

BACKGROUND AND AIMS

Moderate physical exercise and dietary restriction have both been demonstrated to delay some of the adverse effects of aging. In order to elucidate similarities or dissimilarities in their mode of action on the aging immune system in a comparative setting, we examined significant parameters of cell-mediated immunity in Sprague- Dawley rats.

METHODS

Male Sprague-Dawley rats, housed individually, were divided into four groups, living from 5 months (baseline group BL) up to 15, 19 and 23 months of age as follows: voluntary running in wheels (RW), food restricted by feeding to pair weight with RW animals (PW), forced running on treadmills (TM), and sedentary controls with ad libitum access to food (S1). White blood cell counts, capacity for lymphocyte proliferation in response to Concanavalin A, and interleukin-2 (IL-2) plasma concentrations were determined.

RESULTS

White blood cell counts and the cell numbers of lymphocytes, neutrophil and eosinophil granulocytes were significantly lower in the older RW and PW groups. We observed influences of forced exercise on lymphocyte proliferation: blastogenic reactivity was higher in TM animals compared with RW and PW animals at 23 months of age. Exclusively for RW animals, we found lower plasma concentrations of IL-2 at 23 months.

CONCLUSIONS

Our data support the idea that moderate physical exercise modulates age-associated decline in the cell-mediated immunity of old Sprague-Dawley rats significantly more than corresponding dietary restrictions.

Physical Exercise Retards the Development of Chronic Nephropathy in the Ageing Rat as Efficiently as Food Restriction Does

BACKGROUND

Obesity combined with decreasing physical fitness in the ageing Western populations promotes a number of degenerative diseases, including chronic kidney disease. It has further been shown in rodent models that prevention of obesity by food restriction mitigates development of kidney lesions. Whether lifelong physical activity also has a positive effect is not known.

OBJECTIVE

To compare the effects of physical exercise and food restriction on the development of chronic kidney lesions in ageing rats.

METHODS

Male Sprague-Dawley rats were divided into groups: voluntarily running in wheels (RW), food restriction to the degree necessary to attain pair weight to RW rats (PW), forced running in treadmills (TM) and sedentary controls housed individually (S1) or 4 in each cage (S4). The interventions began at the age of 5 months and kidneys were sampled and analysed histologically at the ages of 15, 19 and 23 months.

RESULTS

Total score for kidney lesions (sum of the scores for glomerular changes, interstitial non-purulent inflammation, proteinaceous casts in tubules and increased amount of connective tissue, the possible maximum being 10.0) increased from 0.5 +/- 0.2 at 5 months of age to 1.6 +/- 0.3 for RW, 2.3 +/- 0.4 for PW, 4.5 +/- 0.4 for TM, 3.6 +/- 0.5 for S1 and 5.4 +/- 0.6 for S4 at the age of 23 months. The increase from 5 months of age was gradual for all groups through 15, 19 and 23 months. The patterns for the various lesions followed the same pattern with the exception of connective tissue, which did not increase.

CONCLUSION

Voluntary running in wheels is as effective in mitigating kidney lesions as is food restriction, while forced running in a treadmill is not effective in this respect.

Effects of life-long exercise on circulating free fatty acids and muscle triglyceride content in ageing rats

Regular physical exercise has emerged, together with dietary restriction, as an effective intervention in delaying degenerative diseases and augmenting life span in rodents. The mechanisms involved remain largely unknown, although a beneficial influence on the age-related alteration of insulin sensitivity has been hypothesized. As muscle triglyceride (TG) accumulation is considered a reliable index of muscle insulin resistance, in this study we explored muscle TG content in 23-month-old male Sprague-Dawley rats subjected to life-long training. Plasma glucose, insulin, free fatty acid (FFA) and leptin levels were also measured. Both voluntary running in wheels (RW) and forced training in treadmill (TM) were studied. As RW rats weighed less than controls, a cohort of untrained animals, fed to pair weight (PW) with RW, was added to discriminate the effect of exercise from that of food restriction. Sedentary ad libitum fed rats served as controls. In 23-month-old RW rats, muscle TG content was reduced by 50% with respect to age-matched sedentary controls, while in TM group this reduction was smaller but still highly significant, and occurred independently on the changes in body fat mass. In both the trained rat groups, there was a significant decrease in circulating FFA levels and a trend to reduced insulin levels. In PW rats, muscle TG levels decreased similarly to RW rats, while plasma parameters were less modified. In particular, RW training was more effective than PW in preventing the age-related increase in circulating leptin levels. Our results suggest that voluntary exercise effectively counteracts the development of insulin resistance in the muscles of ageing rats as well as other related changes such as hyperlipacidaemia and compensatory hyperleptinaemia. Forced training or moderate food restriction appear slightly less effective than voluntary exercise in preventing age-dependent alterations in nutrient distribution and/or utilization.