Interaction between exercise, dietary restriction and age-related bone loss in a rodent model of male senile osteoporosis.

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.

Differential associations between white blood cell counts and fatigue in young and older adults.

BACKGROUND AND AIMS: The aims of this exploratory study were to study whether fatigue might be related to the cellular immune system by 1) analysing if the number of white blood cell subsets are related to fatigue and 2) if possible relationships vary in younger and older community-dwelling individuals. METHODS: The participants were recruited from nine general practitioners in Aarhus County, Denmark and included 196 individuals aged 20-35 years and 314 individuals aged 70-85 years. The white blood cell counts included number of total leukocytes, lymphocytes, monocytes, neutrophils, eosinophils, and basophils. General fatigue was measured by a question from the SF-12 Vitality-Scale and mobility-related fatigue by the Avlund Mob-T Scale. RESULTS: Total number of lymphocytes was associated with fatigue in the old sample, both in the crude and adjusted analyses. Total number of leukocytes and netrophils were associated with fatigue in both age groups in the crude analyses. In the old sample the estimates were attenuated to non-significance when adjusting for physical activity and disability. In the young sample the estimates stayed statistically significant in the fully adjusted analyses regarding number of neutrophils, while the associations between fatigue and number of leukocytes were attenuated to non-significance when adjusting for depressive mood. CONCLUSION: Total number of leukocytes, lymphocytes and neutrophils were associated with fatigue in both age groups, while the explanatory factors for the associations differed by age group, in that the associations were partly explained by physical activity and disability in the old sample and partly by depressive mood in the young sample. The findings provide initial insight into the potential role of leukocyte, neutrophil and lymphocyte counts in the development of fatigue.

Decline of bone marrow-derived hematopoietic progenitor cell quality during aging in the rat.

Several studies have shown that aging is associated with quantitative and qualitative alterations of the stem and progenitor cell compartment. The current results indicate that there is a significant age-associated decline in the proliferative capacity of rat myeloid progenitor cells. In contrast, no difference was found in the frequency of myeloid progenitor cells in the bone marrow of young versus old rats. Furthermore, a significant shift towards higher proliferative capacity of myeloid progenitors was observed after lifelong voluntary exercise. These data emphasize that aging is accompanied by a loss of proliferative capacity and that voluntary exercise could retard this process.

Modulation of the hippocampal protein machinery in voluntary and treadmill exercising rats.

Information about protein expression studies in the brain of exercising and sedentary animals is limited. Cognitive functions change during exercise and the aim of this study was to investigate rat protein levels of the protein machinery in the hippocampus, the main cognitive brain area for spatial learning and memory, in exercising rats. Protein fluctuations may reflect functional variation during exercise. Male Sprague-Dawley rats, 23 months old, were used for the study: the first group consisted of sedentary rats, the second of rats undertaking voluntary exercise from 5 months to 23 months and the third undertaking involuntary exercise on a treadmill from 5 months to 23 months. Two-dimensional gel electrophoresis with subsequent mass spectrometrical identification assigning spots to proteins and determination of coomassie-densities was carried out. Heterogeneous nuclear ribonucleoprotein K, one protein variant of heat shock cognate 71 kDa protein and BAG family molecular chaperone regulator 5 showed differential protein levels in the three groups when a p-value of <0.005 was considered as statistically significant thus respecting multiple testing. The biological meaning of changed protein levels in hippocampus under different conditions of exercise is not known but warrants further investigation.

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.

Physical functioning and use of health services in a young and old sample. The influence of fatigue.

INTRODUCTION: The purpose was to analyse 1) whether fatigue is related to physical functioning and utilization of health services at one-year follow-up in a young and old sample and 2) to compare the results of two different measures of fatigue. METHODOLOGY: The study is a longitudinal cohort study based on 182 young (age 20-35) and 199 older (age 70-85) community-dwelling individuals recruited from nine general practitioners in Aarhus, Denmark. Physical functioning was measured by the physical health scale from the SF-12-questionnaire. Data on health care utilization were extracted from the county's central register during one year. Fatigue was measured as Vitality-Tiredness by a question from the SF-12 questionnaire and Mobility-Tiredness by the Avlund Mobility-Tiredness Scale on fatigue in six daily activities. RESULTS: The predictive value of the two measures varied by the age of the participants. The Vitality-Tiredness Scale was related to the outcome measures in both samples, while the Mobility-Tiredness Scale was only predictive in the old population. In the young sample the associations were attenuated by the covariates, while the estimates in the old sample remained strong and significant in the adjusted analyses. CONCLUSION: Fatigue is related to subsequent physical functioning and use of health services at one year follow-up, both in young and old individuals.

Norepinephrine treatment and aging lead to systemic and intracellular oxidative stress in rats.

Reactive oxygen species (ROS) play important roles in cellular senescence and organismic aging. Furthermore, they have been implicated in some of the adverse effects of chronic stress due to elevated peripheral levels of catecholamines. Here, we applied three different techniques to individually compare the systemic and intracellular oxidative stress in aged (23 months) and young (5 months) Sprague-Dawley rats, and in young rats treated for 12 or 24 h with norepinephrine (NE). Thiol groups of blood serum proteins (RSH) were determined by means of Ellman's reaction. Intracellular ROS were assessed in spleen cells and peripheral blood lymphocytes (PBL) by carbonylation of cellular (spleen) proteins as determined by immunoblotting (Oxyblot) and/or by means of 2',7'-dichlorofluorescein (DCF) fluorescence. As compared to the young, untreated controls, both old rats and NE treated young rats showed similarly lowered RSH values paralleled by elevated intracellular ROS levels or enhanced Oxyblot signals. Individual RSH values were highly significantly, negatively correlated with respective Oxyblot data as well as with DCF fluorescence. The results confirm the roles of ROS in aging and adrenergic stress in the rat model, and suggest that the decrease in RSH of blood serum may be taken as a valid indicator for the enhanced oxidative stress in lymphocytes.

Bone structure and metabolism in a rodent model of male senile osteoporosis.

Osteoporosis is a common and severe condition in elderly men, which is poorly characterized. In order to identify the hallmarks of age-related bone loss in the male mammalian skeleton, we studied several aspects of bone structure and metabolism in 23-month-old male Sprague-Dawley rats and compared them to 5-month-old animals. Cancellous bone mineral density, bone volume and trabecular number were markedly reduced in the proximal tibia of aged rats when compared to the young rats. An increase in bone matrix material density indicating a reduced deposition of new bone matrix was seen. Also, serum levels of osteocalcin, a marker of bone formation, were reduced in old males. The decreased bone formation could in part be linked to the decreased serum insulin-like growth factor 1 (IGF-1) levels which were observed in these animals. Serum levels of RatLaps (c-terminal telopeptide of type I collagen) were increased. Interestingly, an ex vivo osteoclast generation assay revealed that bone marrow from aged rats formed fewer osteoclasts than that from young rats. Consistent with this observation, serum levels of soluble RANKL, a critical osteoblast derived factor for osteoclastogenesis, were decreased in aged rats and RANKL mRNA expression was slightly reduced in bone marrow cells. Elevated leptin and adiponectin levels present in these animals could have contributed further to impaired osteoclastogenesis. We conclude that aged male rodents are characterized by a severely diminished cancellous bone network and a bone turnover situation in which bone formation is decreased to such an extent that it is outweighed by bone resorption, despite a blunted osteoclast generation potential of the bone marrow.

Impairment of water maze behaviour with ageing is counteracted by maze learning earlier in life but not by physical exercise, food restriction or housing conditions.

Spatial learning and memory decline with ageing in humans as well as rats. We examined the influence of different interventions on male Sprague Dawley rats with respect to learning ability and memory at the age of 5, 10 and 18 months. The intervention and control groups were: (RW) voluntary exercise in running wheels, (PW) sedentary, food restricted (by about 25%) to keep them at pair weight with RW, (S1) sedentary, fed ad libitum, (TM) forced training in a treadmill, and, (S4) sedentary, fed ad libitum. The animals in all groups were housed individually except those in group S4, which were housed four in each cage. The ability of learning and memory was determined in the Morris water maze. The results showed a significantly better learning ability when young in comparison with their ability when having grown older. At the age of 18 months, the performance was significantly better in the subgroups which had received training also at the age of 10 months compared to the subgroups receiving their first training. None of the various interventions had any significant effect on these functions. Repeated training seems to be the best intervention with respect to retaining learning ability and memory.

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.

Negative thoughts and health: associations among rumination, immunity, and health care utilization in a young and elderly sample.

OBJECTIVE: In the present study, it was tested whether rumination-negative, recurrent thoughts-would be associated with immune parameters and health care utilization. Because rumination has been associated with sadness and subjective sleep quality, it was tested whether these factors mediated the possible effects of rumination. A young sample and an elderly sample were included to test for age differences in the association between rumination and health-related measures. METHODS: A representative sample of 196 young subjects (20 to 35 years) and 314 elderly subjects (70 to 85 years) completed questionnaire measures of rumination, sadness, and subjective sleep quality. Immune measures included leukocyte counts, lymphocyte subsets, natural killer cell activity, and T-cell proliferation. Contacts with primary care physicians were registered for 1 year through central registers. RESULTS: Rumination displayed a positive association with total leukocyte count, total lymphocyte count, and number of B cells among the elderly, and this was not mediated by sadness or subjective sleep quality. Rumination was also positively associated with number of telephone consultations during the follow-up for the elderly, and this was partly mediated by sadness and subjective sleep quality. Although total leukocyte counts correlated with number of telephone consultations at the follow-up, none of the immune parameters mediated the association between rumination and health care utilization. No significant associations were found for the young participants. CONCLUSION: The results suggest that rumination may be associated with health-related measures in the elderly. Thus, negative thoughts may be detrimental to health, independently of negative affect.