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

Challenges in establishing animal models for studying osteoimmunology of hypoparathyroidism

Hypoparathyroidism is a relatively rare human and veterinary disease characterized by deficient or absent production of parathyroid hormone (PTH). PTH is known as a classical regulator of calcium and phosphorus homeostasis. Nevertheless, the hormone also appears to modulate immune functions. For example, increased CD4:CD8 T-cell ratios and elevated interleukin (IL)-6 and IL-17A levels were observed in patients with hyperparathyroidism, whereas gene expression of tumor necrosis factor-α (TNF-α) and granulocyte macrophage-colony stimulating factor (GM-CSF) was decreased in patients with chronic postsurgical hypoparathyroidism. Various immune cell populations are affected differently. So, there is a need for validated animal models for the further characterization of this disease for identifying targeted immune-modulatory therapies. In addition to genetically modified mouse models of hypoparathyroidism, there are surgical rodent models. Parathyroidectomy (PTX) can be well performed in rats-for pharmacological and associated osteoimmunological research and bone mechanical studies, a large animal model could be preferable, however. A major drawback for successfully performing total PTX in large animal species (pigs and sheep) is the presence of accessory glands, thus demanding to develop new approaches for real-time detection of all parathyroid tissues.

Low-carbohydrate, high-fat diet and running exercise influence bone parameters in old mice

We examined the effects and interactions of a low-carbohydrate, high-fat (LCHF) diet and voluntary running exercise on bone in older mice. Male 19-month-old mice were divided into four groups by diet (control vs. LCHF) and exercise (sedentary vs. voluntary running). The control diet was 55% carbohydrate, 23% protein, and 22% fat, and the LCHF diet was 10% carbohydrate, 33% protein, and 57% fat as percentages of calories. The experiment ended when the mice reached 24 months old. Statistical analysis was conducted using two-way analysis of variance with diet and exercise. The LCHF diet decreased bone mineral content (BMC), bone mineral density, bone volume fraction, and trabecular number. There was no significant interaction between diet and exercise on many bone parameters. However, there were significant diet and exercise interactions on lumbar BMC and tibial trabecular total tissue volume and average cortical thickness. The LCHF diet attenuated the benefit of running exercise on lumbar BMC and caused running to have a negative effect on tibial trabecular total tissue volume. Our study suggests that the LCHF diet impairs bone mass and some trabecular microstructure and reduces the benefit of exercise on lumbar BMC in old mice.

Regulation of bone health through physical exercise: Mechanisms and types

Osteoporosis, characterized by bone mineral density reduction, bone mass loss, increased bone fragility, and propensity to fractures, is a common disease in older individuals and one of the most serious health problems worldwide. The imbalance between osteoblasts and osteoclasts results in the predominance of bone resorption and decreased bone formation. In recent years, it has been found that regular and proper exercise not only helps prevent the occurrence of osteoporosis but also adds benefits to osteoporosis therapy; accordingly, bone homeostasis is closely associated with mechanical stress and the intricate crosstalk between osteoblasts and osteoclasts. In this review, we summarize the mechanisms of exercise on osteoporosis and provide new proposals for the prevention and treatment of osteoporosis.

Effects of Different Types of Mechanical Loading on Trabecular Bone Microarchitecture in Rats

Mechanical loading is generally considered to have a positive impact on the skeleton; however, not all types of mechanical loading have the same beneficial effect. Many researchers have investigated which types of mechanical loading are more effective for improving bone mass and strength. Among the various mechanical loads, high-impact loading, such as jumping, appears to be more beneficial for bones than low-impact loadings such as walking, running, or swimming. Therefore, the different forms of mechanical loading exerted by running, swimming, and jumping exercises may have different effects on bone adaptations. However, little is known about the relationships between the types of mechanical loading and their effects on trabecular bone structure. The purpose of this article is to review the recent reports on the effects of treadmill running, jumping, and swimming on the trabecular bone microarchitecture in small animals. The effects of loading on trabecular bone architecture appear to differ among these different exercises, as several reports have shown that jumping increases the trabecular bone mass by thickening the trabeculae, whereas treadmill running and swimming add to the trabecular bone mass by increasing the trabecular number, rather than the thickness. This suggests that different types of exercise promote gains in trabecular bone mass through different architectural patterns in small animals.

Does Physical Exercise Always Improve Bone Quality in Rats?

For decades, the osteogenic effect from different physical activities on bone in rodents remained uncertain. This literature review presents for the first time the effects on five exercise models (treadmill running, wheel running, swimming, resistance training and vibration modes) in three different experimental rat groups (males, females, osteopenic) on bone quality. The bone parameters presented are bone mineral density, micro-architectural and mechanical properties, and osteoblast/osteocyte and osteoclast parameters. This review shows that physical activities have a positive effect (65% of the results) on bone status, but we clearly observed a difference amongst the different protocols. Even if treadmill running is the most used protocol, the resistance training constitutes the first exercise model in term of osteogenic effects (87% of the whole results obtained on this model). The less osteogenic model is the vibration mode procedure (31%). It clearly appears that the gender plays a role on the bone response to swimming and wheel running exercises. Besides, we did not observe negative results in the osteopenic population with impact training, wheel running and vibration activities. Moreover, about osteoblast/osteocyte parameters, we conclude that high impact and resistance exercise (such jumps and tower climbing) seems to increase bone formation more than running or aerobic exercise. Among the different protocols, literature has shown that the treadmill running procedure mainly induces osteogenic effects on the viability of the osteocyte lineage in both males and females or ovariectomized rats; running in voluntary wheels contributes to a negative effect on bone metabolism in older male models; whole-body vertical vibration is not an osteogenic exercise in female and ovariectomized rats; whereas swimming provides controversial results in female models. For osteoclast parameters only, running in a voluntary wheel for old males, the treadmill running program at high intensity in ovariectomized rats, and the swimming program in a specific ovariectomy condition have detrimental consequences.

Effects of treadmill with different intensities on bone quality and muscle properties in adult rats

BACKGROUND

Bone is a dynamically hierarchical material that can be divided into length scales of several orders of magnitude. Exercise can cause bone deformation, which in turn affects bone mass and structure. This study aimed to study the effects of treadmill running with different intensities on the long bone integrity and muscle biomechanical properties of adult male rats.

METHODS

Forty-eight 5-month-old male SD rats were randomly divided into 4 groups: i.e., sedentary group (SED), exercise with speed of 12 m/min group (EX12), 16 m/min group (EX16), and 20 m/min group (EX20). The exercise was carried out for 30 min every day, 5 days a week for 4 weeks. The femurs were examined using three-point bending test, microcomputer tomography scanning and nanoindentation test; the soleus muscle was dissected for tensile test; ALP and TRACP concentrations were measured by serum analysis.

RESULTS

The failure load was significantly increased by the EX12 group, whereas the elastic modulus was not significantly changed. The microstructure and mineral densities of the trabecular and cortical bone were significantly improved by the EX12 group. The mechanical properties of the soleus muscle were significantly increased by treadmill exercise. Bone formation showed significant increase by the EX12 group. Statistically higher nanomechanical properties of cortical bone were detected in the EX12 group.

CONCLUSION

The speed of 12 m/min resulted in significant changes in the microstructure and biomechanical properties of bone; besides, it significantly increased the ultimate load of the soleus muscle. The different intensities of treadmill running in this study provide an experimental basis for the selection of exercise intensity for adult male rats.

Effect of free running wheel exercise on renal expression of parathyroid hormone receptor type 1 in spontaneously hypertensive rats

An active lifestyle is generally recommended for hypertensive patients to prevent subsequent end-organ damage. However, experimental data on long-term effects of exercise on hypertension are insufficient and underlying mechanisms are not well understood. This study was aimed to investigate the effect of exercise on renal expression of parathyroid hormone-related protein (PTHrP) and parathyroid hormone receptor type 1 (PTHR1) in spontaneously hypertensive rats (SHR). Twenty-four rats started free running wheel exercise at the age of 1.5 months (pre-hypertensive state) and proceeded for 1.5, 3.0, 6.0, and 10.0 months. Thirty rats kept under standard housing conditions were used as sedentary controls. Kidney function was assessed by measuring plasma creatinine levels and urine albumin-to-creatinine ratios. Renal expression of PTHrP and PTHR1 was analyzed by qRT-PCR and western blot. Renal expression of PTHR1 was markedly increased between the 6th and 10th months in sedentary rats and this increase was significantly lower in SHRs with high physical activity on mRNA (-30%) and protein level (-27%). At the same time, urine albumin-to-creatinine ratio increased (from 65 to 231 mg/g) but somehow lower in exercise performing SHRs (48-196 mg/g). Our data suggest that enhanced exercise, stimulated by allocation of a free running wheel, is associated with lower PTHR1 expression in SHRs and this may contribute to preserved kidney function.

Effects of a moderately high-protein diet and interval aerobic training combined with strength-endurance exercise on markers of bone metabolism, microarchitecture and turnover in obese Zucker rats

BACKGROUND

Weight loss is a public health concern in obesity-related diseases such as metabolic syndrome, and the protein level of the diets seem to be crucial for the development and maintenance of bone. The nature of exercise and whether exercise in combination with moderately high-protein dietary interventions could protect against potential bone mass deficits remains unclear.

OBJECTIVES

To investigate the effects of a moderately high-protein diet and interval aerobic training combined with strength-endurance exercise (IASE) protocol on bone status, and to assess potential interaction effects (i.e. diet*IASE).

METHODS

Male Zucker fatty rats were randomized distributed into 4 groups (n=8): normoprotein+sedentary; normoprotein+exercise; moderately high-protein+sedentary, and moderately high-protein+exercise. Training groups conducted an IASE program, 5days/week for 2months. Markers of bone metabolism were measured in plasma. Parameters of bone mass and 3D outcomes for trabecular and cortical bone microarchitecture were assessed by micro-computed tomography.

RESULTS

Femur length, plasma osteocalcin, sclerostin, osteoprotegerin, receptor activator of nuclear factor kappa-B ligand, insulin, leptin, PTH, uric acid and urinary phosphorus levels were lower in the moderately high-protein compared to the normoprotein groups (all, p<0.05), whereas plasma alkaline phosphatase, aspartate aminotransferase, alanine transaminase, and urinary uric acid concentrations, and cortical total volume (TV) and bone volume (BV) were higher in the moderately high-protein (all, p<0.01). Final body weight and alkaline phosphatase levels were lower in the exercise compared to the sedentary (both, p<0.05), whereas femur length and weight, aminoterminal propeptides of type I procollagen and C-terminal telopeptides of type I collagen concentrations, and cortical TV and BV were higher in the exercise compared to the sedentary groups (all, p<0.05).

CONCLUSION

The combination of interventions may be effective to enhance trabecular bone microarchitecture and BMD, and has a partial impact on cortical bone in obese rats. Nevertheless, they do not induce any alteration on the bone turnover markers.

Obesity-related changes in bone structural and material properties in hyperphagic OLETF rats and protection by voluntary wheel running

PURPOSE

To examine how the development of obesity and the associated insulin resistance affect bone structural and material properties, and bone formation and resorption markers in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat model.

METHODS

This was a 36-week study of sedentary, hyperphagic, male OLETF rats (OLETF-SED), exercise-treated OLETF rats (OLETF-EX) and sedentary non-hyperphagic controls (LETO-SED) with data collection at 13, 20, and 40 weeks of age (n = 5-8 animals per group per timepoint).

RESULTS

Body mass and fat (%) were significantly greater in OLETF-SED versus controls. OLETF-SED were insulin resistant at 13 and 20 weeks, with overt diabetes by 40 weeks. At 13weeks, OLETF-SED had lower total body BMC and BMD and serum P1NP compared with LETO-SED. Differences in total body BMC and BMD between OLETF-SED and LETO-SED persisted at 20 weeks, with reductions in total and cortical BMD of the tibia. OLETF-SED also had lesser femur diameter, cross-sectional area, polar moment of area, and torque at fracture than LETO-SED. By 40 weeks, OLETF-SED had elevated bone resorption and reduced intrinsic bone strength. OLETF-EX did not show the excessive weight gain, obesity, insulin resistance or diabetes observed in OLETF-SED. OLETF-EX had greater BMD than OLETF-SED, and structural and material properties of the femur were significantly increased in OLETF-EX relative to OLETF-SED and LETO-SED.

CONCLUSIONS

The negative skeletal effects of excessive adiposity and insulin resistance were evident early in the progressive obesity with lasting negative impacts on intrinsic and extrinsic bone strength. Exercise protected against obesity-associated skeletal changes with marked benefits on the biomechanical properties of bone.

Changes in Serum Levels of Myokines and Wnt-Antagonists after an Ultramarathon Race

BACKGROUND

Regular physical activities have a positive effect on the muscular skeletal system but overstrenuous exercise may be different. Transiently suppressed bone formation and increased bone resorption after participation in a 246-km ultradistance race has been demonstrated.

PURPOSE

The aim of this study was to analyze effects of the Spartathlon race on novel musculoskeletal markers.

METHODS

Venous blood samples were obtained before and immediately after the race from 19 participants of the Spartathlon. From 9 runners who were available 3 days after the start blood was drawn for a third time. Serum levels of myostatin, an inhibitor of myogenic differentiation, and its opponent follistatin as well as sclerostin and dickkopf-1, both of them inhibitors of the wnt signaling pathway, and markers of bone turnover were determined.

RESULTS

Serum levels of myostatin were significantly higher after the race. Serum follistatin only showed a transient increase. Sclerostin levels did not significantly differ before and after the race, whereas dickkopf-1 levels were significantly decreased. At follow-up a decrement of sclerostin and dickkopf-1 levels was seen. Serum cathepsin K levels did not change.

CONCLUSION

The increase of serum levels of myostatin appears to reflect muscle catabolic processes induced by overstrenuous exercise. After the short-term uncoupling of bone turnover participation in an ultradistance race seems to initiate a long-term positive effect on bone indicated by the low-level inhibition of the Wnt/β-catenin signaling pathway.

The effects of risedronate and exercise on osteoporotic lumbar rat vertebrae and their sensory innervation

STUDY DESIGN

Investigation of sensory innervation of rat osteoporotic lumbar vertebrae using in vitro and in vivo models.

OBJECTIVE

To investigate (1) sensory innervation of osteoporotic rat vertebrae, (2) effects of risedronate on sensory neurons, (3) effects of osteoporosis treatment on bone mineral densities (BMDs) and the sensory innervation.

SUMMARY OF BACKGROUND DATA

Osteoporotic patients without fractures sometimes experience vague low back pain of unknown origin. The mechanisms of osteoporosis treatments against the pain are unclear.

METHODS

(1) The expression of calcitonin gene-related peptide (CGRP) immunoreactive (-ir) or transient receptor potential vanilloid 1 (TRPV1)-ir nerve fibers in vertebrae and dorsal root ganglions (DRG) innervating L3 vertebrae of Sprague Dawley rats labeled with neurotracer were examined in control, sham, and ovariectomized (OVX) rats. (2) Cultured rat neonate DRG neurons in media containing different concentrations of risedronate were immunostained for CGRP, and we measured its activity using axonal length and proportion of CGRP-ir neurons. (3) BMDs and CGRP expression in DRG neurons innervating L3 vertebrae were examined in the following 5 groups: sham (treated with saline), OVX (saline), OVX+EXE (treadmill exercise), OVX+RIS (risedronate), and OVX+RIS+EXE (risedronate and exercise).

RESULTS

(1) A few CGRP-ir or TRPV1-ir nerve fibers were observed in the bone marrow. CGRP or TRPV1 expression in DRG was elevated in the OVX group (P < 0.05). (2) The axonal length and proportion of CGRP-ir neurons were dose-dependently suppressed (P < 0.05). (3) BMDs improved and the CGRP expression decreased in the risedronate-treated groups (P < 0.05), especially in the OVX+RIS+EXE group.

CONCLUSION

Sensory innervation of osteoporotic rat vertebrae showed increased expression of CGRP and TRPV1 in DRG neurons. Risedronate suppressed activity of CGRP-ir neurons in vitro, improved BMD, and decreased CGRP expression, especially together with exercise in vivo.

Short-term voluntary exercise in the rat causes bone modeling without initiating a physiological stress response

Recent research has revealed a neuroendocrine connection between the skeleton and metabolism. Exercise alters both bone modeling and energy balance and may be useful in further developing our understanding of this complex interplay. However, research in this field requires an animal model of exercise that does not cause a physiological stress response in the exercised subjects. In this study, we develop a model of short-term voluntary exercise in the female rat that causes bone modeling without causing stress. Rats were randomly assigned to one of three age-matched groups: control, tower climbing, and squat exercise (rising to an erect bipedal stance). Exercise for 21 days resulted in bone modeling as assessed by peripheral quantitative computed tomography. Fecal corticosterone output was used to assess physiological stress at three time points during the study (preexercise, early exercise, and late in the exercise period). There were no differences in fecal corticosterone levels between groups or time points. This model of voluntary exercise in the rat will be useful for future studies of the influence of exercise on the relationship between skeletal and metabolic health and may be appropriate for investigation of the developmental origins of those effects.

The influence of long-term treadmill exercise on bone mass and articular cartilage in ovariectomized rats

Background

Loss of bone quality and deterioration of articular cartilage are commonly seen after menopause. While exercise may protect against tissue degeneration, a clear link has yet to be established. The aim of the present study is to investigate the influence of long-term treadmill exercise on changes in bone mass and articular cartilage in ovariectomized rats.

Methods

Sixty female Sprague-Dawley rats were randomly assigned to 4 groups: ovariectomized (OVX), ovariectomized plus treadmill exercise (OVX-RUN), treadmill exercise alone (RUN), and control (CON) groups. After 36 weeks, the following variables were compared among the 4 groups. Bone mass was evaluated by trabecular bone volume and bone mineral density (BMD). Articular cartilage in the knee joints was evaluated by histology analysis and a modified Mankin score.

Results

Rats in the ovariectomized groups (OVX and OVX-RUN) had significantly lower BMD and bone mass than the non-ovariectomized rats (CON and RUN), indicating that exercise did little to preserve bone mass. However, the sedentary OVX group had a significantly worse modified Mankin score (7.7 ± 1.4) than the OVX-RUN group (4.8 ± 1.0), whose scores did not differ significantly from the other 2 non-operated groups. The articular cartilage in the sedentary OVX rats was relatively thinner, hypocellular, and had more clefts than in the other 3 groups.

Conclusion

This study suggests that long-term exercise protects articular cartilage in OVX rats but does not retard the loss of bone mass seen in after menopause.

Biogerontology in Austria

In Austria significant progress in the field of biogerontology has been achieved in the past years. Biogerontological research is performed in academic and extramural institutions. The Institute for Biomedical Aging Research of the Austrian Academy of Science at Innsbruck is the largest institution dealing with biogerontology in Austria. Moreover, gerontologic research is performed at the Universities of Salzburg and Graz, the Medical Universities of Vienna, Innsbruck and Graz, the University of Veterinary Medicine (Vienna) and the University of Natural Resources and Applied Life Sciences (Vienna). This article describes the work of selected research groups involved in biogerontology in a geographic arrangement.