Effects of strength training on osteogenic differentiation and bone strength in aging female Wistar rats

Exercise alleviates osteoporosis by regulating the secretion of the Senescent Associated Secretory Phenotype

As the elderly population grows, the number of patients with metabolic bone diseases such as osteoporosis has increased sharply, posing a significant threat to public health and social economics. Although pharmacological therapies for osteoporosis demonstrate therapeutic benefits, their prolonged use is associated with varying degrees of adverse effects. As a non-pharmacological intervention, exercise is widely recognized for its cost-effectiveness, safety, and lack of toxic side effects, making it a recommended treatment for osteoporosis prevention and management. Previous studies have demonstrated that exercise can improve metabolic bone diseases by modulating the Senescent Associated Secretory Phenotype (SASP). However, the mechanisms through which exercise influences SASP remain unclear. Therefore, this review aims to summarize the effects of exercise on SASP and elucidate the specific mechanisms by which exercise regulates SASP to alleviate osteoporosis, providing a theoretical basis for osteoporosis through exercise and developing targeted therapies.

Increased deformations are dispensable for encapsulated cell mechanoresponse in engineered bone analogs mimicking aging bone marrow

Aged individuals and astronauts experience bone loss despite rigorous physical activity. Bone mechanoresponse is in-part regulated by mesenchymal stem cells (MSCs) that respond to mechanical stimuli. Direct delivery of low intensity vibration (LIV) recovers MSC proliferation in senescence and simulated microgravity models, indicating that age-related reductions in mechanical signal delivery within bone marrow may contribute to declining bone mechanoresponse. To answer this question, we developed a 3D bone marrow analog that controls trabecular geometry, marrow mechanics and external stimuli. Validated finite element (FE) models were developed to quantify strain environment within hydrogels during LIV. Bone marrow analogs with gyroid-based trabeculae of scaffold volume fractions (SV/TV) corresponding to adult (25 %) and aged (13 %) mice were printed using polylactic acid (PLA). MSCs encapsulated in migration-permissive hydrogels within printed trabeculae showed robust cell populations on both PLA surface and hydrogel within a week. Following 14 days of LIV treatment (1 g, 100 Hz, 1 h/day), cell proliferation, type-I collagen (Collagen-I) and filamentous actin (F-actin) were quantified for the cells in the hydrogel fraction. While LIV increased all measured outcomes, FE models predicted higher von Mises strains for the 13 % SV/TV groups (0.2 %) when compared to the 25 % SV/TV group (0.1 %). While LIV increased collagen-I volume 34 % more in 13 % SV/TV groups when compared to 25 % SV/TV groups, collagen-I and F-actin measures remained lower in the 13 % SV/TV groups when compared to 25 % SV/TV counterparts, indicating that both LIV-induced strains and scaffold volume fraction (i.e. available scaffold surface) affect cell behavior in the hydrogel phase. Overall, bone marrow analogs offer a robust and repeatable platform to study bone mechanobiology.

Exercise-induced adaptive response of different immune organs during ageing

The immune system plays a crucial role in the ageing process. As individuals age, significant alterations in the immune system experiences occur, marked by a decline in immune cell count, compromised immune function, and decreased immune regulation across various immune organs. These changes collectively weaken the capacity to combat diseases and infections, highlighting the vulnerability that accompanies ageing. Exercise is a potent intervention that profoundly influences holistic well-being and disease mitigation, with a notable emphasis on immune modulation. In general, regular moderate exercise holds significant potential to enhance immune defense mechanisms and metabolic well-being by augmenting the circulation and activation of immune cells. However, some exercise modalities would trigger detrimental effects on the immune system. It can be seen that the regulatory responses of various immune organs to diverse exercise patterns are different. This review aims to examine the immunological responses elicited by exercise across various immune organs, including the lymph nodes, spleen, bone marrow, and thymus, to underscore the nuanced interplay between exercise patterns and the immune organ. This underscores the importance of customizing exercise interventions to optimize immune function across the lifespan.

The impact of resistance training on memory, gait and oxidative stress during periestropause in rats

Aging, especially in female, is complex, involving various factors such as reproductive sensitivity, cognitive and functional decline, and an imbalance in the redox system. This study aims to assess the effectiveness of long-term resistance training as a non-pharmacological strategy to mitigate the impairment of recognition memory, hippocampal redox state, and ambulation in aging female Wistar rats during the periestropause period. Thirty Wistar rats aged 17 months, in periestropause, were distributed into non-trained (NT) and resistance training (RT; stair climbing 3 times per week for 4 months) groups. Before (17 months) and after (21 months) of the RT period, the rats underwent tests for ambulation, elevated plus maze (EPM), open field, and object recognition. Biochemical and histological analyses were conducted on the hippocampus of these animals. Analysis of the results revealed that at 21 months, females in the NT group (21Mo/NT) exhibited a decreased in length (p=0.0458) and an increased in past width (p<0.0479) compared to their measurements at 17 months. However, after 4 months of RT, the female rats aged 21 months (21Mo/RT group) experienced changes in gait components, showing an increase in length (p<0.0008) and a decrease in stride width. Regarding memory, the object recognition test indicated potential cognitive improvement in 21Mo/RT animals, with significant interaction between intervention and age across all three stages of the test (total exploration time, p=0.0001; Test 1, p=0.0003; Test 2, p=0.0014). This response was notable compared to animals in the 21Mo/NT group, which showed a decline in memory capacity (p<0.01). The data showed a significant difference in relation to the age of the animals (p<0.01). The hippocampal redox state markers showed reduced lipid oxidative (p=0.028), catalase (p=0.022), and superoxide dismutase (p=0.0067) in the RT group compared to the NT group. Hippocampal cells from the 21Mo/RT group showed increased citrate synthase enzyme activity (p<0.05) and Nissl body staining (p<0.05). The results of this study demonstrate that RT performed during the periestropause phase leads to significant improvements in functional abilities, cognitive performance, and neuroplasticity in aging female rats.

The microarchitecture and chemical composition of the femur neck of senescent female rats after different physical training protocols

A sedentary lifestyle, coupled with a decrease in estrogen, impairs bone homeostasis, favoring to the development of osteopenia and osteoporosis, both recognized as risk factors for fractures. Here, we investigated the quality of the femur, particularly the femur neck region, and the ambulation performance of senescent rats subjected to three different physical training protocols during the periestropause period. Forty-eight female rats, 18 months of age, were subjected to a 120-day training period, three times a week. The rats were distributed into four groups: aerobic training (AT), strength training (ST), concurrent training (CT), or no training (NT). After the experimental period, at 21 months of age, ambulation performance and femur were analyzed using microtomography, Raman stereology, densitometry, and mechanical strength tests. The results demonstrated greater remodeling activity and improvement in resistance and bone microarchitecture in the femur neck of senescent female rats after undergoing physical training. Our verified higher intensities of bands related to collagen, phosphate, amide III, and amide I. Furthermore, the analysis of the secondary collagen structures indicated alterations in the collagen network due to the exercise, resulting in increased bone strength. Both AT and strength-based training proved beneficial, with AT showing greater adaptations in bone density and stiffness in the femur, while strength-based training greater adaptations in trabecular and cortical structure. These insights contribute to the understanding of the potential interventions for preventing osteopenia and osteoporosis, which are critical risk factors for fractures.

Increased deformations are dispensable for cell mechanoresponse in engineered bone analogs mimicking aging bone marrow

Aged individuals and astronauts experience bone loss despite rigorous physical activity. Bone mechanoresponse is in-part regulated by mesenchymal stem cells (MSCs) that respond to mechanical stimuli. Direct delivery of low intensity vibration (LIV) recovers MSC proliferation in senescence and simulated microgravity models, indicating that age-related reductions in mechanical signal delivery within bone marrow may contribute to declining bone mechanoresponse. To answer this question, we developed a 3D bone marrow analog that controls trabecular geometry, marrow mechanics and external stimuli. Validated finite element (FE) models were developed to quantify strain environment within hydrogels during LIV. Bone marrow analogs with gyroid-based trabeculae of bone volume fractions (BV/TV) corresponding to adult (25%) and aged (13%) mice were printed using polylactic acid (PLA). MSCs encapsulated in migration-permissive hydrogels within printed trabeculae showed robust cell populations on both PLA surface and hydrogel within a week. Following 14 days of LIV treatment (1g, 100 Hz, 1 hour/day), type-I collagen and F-actin were quantified for the cells in the hydrogel fraction. While LIV increased all measured outcomes, FE models predicted higher von Mises strains for the 13% BV/TV groups (0.2%) when compared to the 25% BV/TV group (0.1%). Despite increased strains, collagen-I and F-actin measures remained lower in the 13% BV/TV groups when compared to 25% BV/TV counterparts, indicating that cell response to LIV does not depend on hydrogel strains and that bone volume fraction (i.e. available bone surface) directly affects cell behavior in the hydrogel phase independent of the external stimuli. Overall, bone marrow analogs offer a robust and repeatable platform to study bone mechanobiology.

Exercise-regulated white adipocyte differentitation: An insight into its role and mechanism

White adipocytes play a key role in the regulation of fat mass amount and energy balance. An appropriate level of white adipocyte differentiation is important for maintaining metabolic homeostasis. Exercise, an important way to improve metabolic health, can regulate white adipocyte differentiation. In this review, the effect of exercise on the differentiation of white adipocytes is summarized. Exercise could regulate adipocyte differentiation in multiple ways, such as exerkines, metabolites, microRNAs, and so on. The potential mechanism underlying the role of exercise in adipocyte differentiation is also reviewed and discussed. In-depth investigation of the role and mechanism of exercise in white adipocyte differentiation would provide new insights into exercise-mediated improvement of metabolism and facilitate the application of exercise-based strategy against obesity.

Combined Ursolic Acid and Resistance/Endurance Training Improve Type 3 Diabetes Biomarkers-Related Memory Deficits in Hippocampus of Aged Male Wistar Rats

Background

Both aging and diabetes are two well-established risk factors related to type 3 diabetes and memory deficits. Accordingly, diabetes multiplies the effects of aging on cognition impairments once these conditions occur simultaneously.

Methods

In this present experimental study, 56 male Wistar rats with HFD/STZ-induced T2D were randomized into seven groups (n = eight animals per group): (1) sedentary old non-diabetic (C); (2) sedentary HFD/STZ-induced T2D (D); (3) sedentary HFD/STZ-induced T2D plus UA (UA) (DU); (4) endurance-trained HFD/STZ-induced T2D (DE); (5) resistance-trained HFD/STZ-induced T2D (DR); (6) endurance-trained HFD/STZ-induced T2D plus UA (DEU); and (7) resistance-trained STZ-diabetic plus UA (DRU) rats. Two-way ANOVA was applied to measure the training, supplementation, and interaction effect on serum and gene expression outcomes.

Result

The study results established no significant interaction effect between the UA supplementation and the resistance/endurance training with regard to the levels of glucose (P = 0.534), insulin (P = 0.327), brain-derived neurotrophic factor (P = 0.191), and insulin-like growth factor-1 (P = 0.448).

Conclusions

To develop novel practical nutritional strategies involving UA intake, further studies are thus needed to clarify how chronic consumption of UA with/without resistance/endurance training reverses cognition disorder process in old male Wistar rats with HFD/STZ-induced T2D.

A low-intensity lifelong exercise routine changes miRNA expression in aging and prevents osteosarcopenic obesity by modulating inflammation

Osteosarcopenic obesity (OSO) has been associated with increase immobility, falls, fractures, and other dysfunctions, which could increase mortality risk during aging. However, its etiology remains unknown. Recent studies revealed that sedentarism, fat gain, and epigenetic regulators are critical in its development. One effective intervention to prevent and treat OSO is exercise. Therefore, in the present study, by keeping rats in conditions of sedentarism and others under a low-intensity exercise routine, we established an experimental model of OSO. We determined the degree of sarcopenia, obesity, and osteopenia at different ages and analyzed the miRNA expression during the lifespan using miRNA microarrays from gastrocnemius muscle. Interestingly microarrays results showed that there is a set of miRNAs that changed their expression with exercise. The pathway enrichment analysis showed that these miRNAs are strongly associated with immune regulation. Further inflammatory profiles with IL-6/IL-10 and TNF-α/IL-10 ratios showed that exercised rats presented a lower pro-inflammatory profile than sedentary rats. Also, the body fat gain in the sedentary group increased the inflammatory profile, ultimately leading to muscle dysfunction. Exercise prevented strength loss over time and maintained skeletal muscle functionality over time. Differential expression of miRNAs suggests that they might participate in this process by regulating the inflammatory response associated with aging, thus preventing the development of OSO.

Ursolic acid enhances the effect of exercise training on vascular aging by reducing oxidative stress in aged type 2 diabetic rats

Ursolic acid (UA) mediates the vasorelaxant activity via nitric oxide (NO) release, and upregulation of endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs) in disease conditions with increased oxidative stress (OS). The present study aimed to reflect on the impact of 8 weeks of a combination of UA supplementation and resistance/endurance training in old male Wistar rats having a high-fat diet and/or low-dose streptozotocin-induced type 2 diabetes (HFD/STZ-induced T2D), with an emphasis on Sirtuin 1 (SIRT1)-endothelial nitric oxide synthase (eNOS) axis and OS indices in their aortic tissues. A total number of56 21-month-old male Wistar rats with HFD/STZ-induced T2D were randomized into seven groups (n = eight animals per group): (1) sedentary old nondiabetic (Control [C]); (2) sedentary HFD/STZ-induced T2D (Diabetic [D]); (3) sedentary HFD/STZ-induced T2D plus UA (Diabetic + Ursolic Acid [DU]); (4) endurance-trained HFD/STZ-induced T2D (Diabetic + Endurance Training [DE]); (5) resistance-trained HFD/STZ-induced T2D (Diabetic + Resistance Training [DR]); (6) endurance-trained HFD/STZ-induced T2D plus UA (Diabetic + Endurance Training + Ursolic Acid [DEU]); and (7) resistance-trained STZ-diabetic plus UA (Diabetic + Resistance Training + Ursolic Acid [DRU]) rats. The ladder-based resistance training group performed the ladder resistance training at 60% of the maximum voluntary carrying capacity (MVCC), 14-20 climbs in each session, with a one-min rest between each two trials, 5 days a week. The treadmill-based endurance exercise training protocol consisted of repeated bouts of high- and low-intensity training with 60-75% maximal running speed and 30%-40% maximal running speed in the course of 8 weeks, respectively. The animals in the supplement groups also took 500 mg of UA/kg of high-fat diet/day, resulting in a daily UA intake of approximately 250 mg UA per kg of body weight rat/day. The resistance/endurance training plus the UA consumption could partially reverse the levels of malondialdehyde (MDA), nitric oxide (NO), as well as total antioxidant capacity (TAC). It was concluded that oral 0.5% UA supplementation can prevent vascular aging biomarkers in a HFD/STZ-induced T2D model. Further studies are also required to clarify how chronic consumption of UA with/without training protocols reverses vascular aging process.

Bone-muscle crosstalk following exercise plus Ursolic acid by myomiR-133a/Cx43-Runx2 axis in aged type 2 diabetes rat models

Natural bioactive compound, Ursolic acid (UA), plus different types of exercise may exert the action on glycemic control, leading to clinical benefits in the prevention and treatment of aging/diabetes-associated complications. So, this study examined the effects of eight weeks combination of 250 mg of UA per day per kilogram of body weight of rat as well as resistance/endurance training on miR-133a expression across serum, bone marrow, skeletal muscle, and Connexin 43 (Cx43)-Runt-related transcription factor 2 (Runx2) signaling axis in high-fat diet and low-dose streptozotocin-induced T2D (here, HFD/STZ-induced T2D). The study was conducted on 56 male Wistar rats (427 ± 44 g, 21 months old), having HFD/STZ-induced T2D randomly assigned into 7 groups of 8 including (1) sedentary non-diabetic old rats (C); (2) sedentary type 2 diabetes animal model (D); (3) sedentary type 2 diabetes animal model + UA (DU); (4) endurance-trained type 2 diabetes animal model (DE); (5) resistance-trained type 2 diabetes animal model (DR); (6) endurance-trained type 2 diabetes animal model + UA (DEU); and (7) resistance-trained type 2 diabetes animal model + UA (DRU). Resistance training included a model of eight weeks of ladder resistance training at 60-80% maximal voluntary carrying capacity (MVCC) for five days/week. Treadmill endurance exercise protocol included eight weeks of repetitive bouts of low-/high-intensity training with 30%-40% and 60%-75% maximal running speed for five days/week, respectively. UA Supplementary groups were treated with 500 mg of UA per kg of high-fat diet per day. The results revealed significant supplement and exercise interaction effects for the BM miR-133a (p = 0.001), the bone marrow Runx2 (p = 0.002), but not the serum miR-133a (p = 0.517), the skeletal muscle miR-133a (p = 0.097) and the Cx43 (p = 0.632). In conclusion, only eight weeks of resistance-type exercise could affect miR-133a profile in muscles and osteoblast differentiation biomarker RUNX2 in aged T2D model of rats. 250 mg of UA per kilogram of body weight rat per day was administered orally, less than the sufficient dose for biological and physiological impacts on osteoblast differentiation biomarkers in aged T2D model of rats following eight weeks.

Upregulation of Runt related transcription factor 1 (RUNX1) contributes to tendon-bone healing after anterior cruciate ligament reconstruction using bone mesenchymal stem cells

Background

Anterior cruciate ligament (ACL) injury could lead to functional impairment along with disabilities. ACL reconstruction often fails owing to the regeneration failure of tendon–bone interface. Herein, we aimed to investigate the effects of Runt related transcription factor 1 (RUNX1) on tendon–bone healing after ACL reconstruction using bone mesenchymal stem cells (BMSCs).

Methods

BMSCs were isolated from the marrow cavity of rat femur, followed by the modification of RUNX1 with lentiviral system. Then, an ACL reconstruction model of rats was established with autografts.

Results

Results of flow cytometry exhibited positive-antigen CD44 and CD90, as well as negative-antigen CD34 and CD45 of the BMSCs. Then, we found that RUNX1-upregulated BMSCs elevated the decreased biomechanical strength of the tendon grafts after ACL reconstruction. Moreover, based on the histological observation, upregulation of RUNX1 was linked with better recovery around the bone tunnel, a tighter tendon–bone interface, and more collagen fibers compared to the group of BMSCs infected with LV-NC. Next, RUNX1-upregulated BMSCs promoted osteogenesis after ACL reconstruction, as evidenced by the mitigation of severe loss and erosion of the cartilage and bone in the tibial and femur area, as well as the increased number of osteoblasts identified by the upregulation of alkaline phosphatase, osteocalcin, and osteopontin in the tendon–bone interface.

Conclusion

Elevated expression of RUNX1 contributed to tendon–bone healing after ACL reconstruction using BMSCs.

The action of oxytocin on the bone of senescent female rats

AIMS

This study verified the action of oxytocin (OT) as a preventive measure to control bone damage during aging in female rats.

MAIN METHODS

Wistar rats received saline (0.15 mol/L/IP; Vehicle Group), Atosiban/AT (300 μg/Kg/IP; At Group), OT (134 μg/Kg/IP; Ot Group), or AT+OT (OT injections 5 min after AT; At+Ot Group), at 19 and 20 months of age. A functional test was performed immediately before and 30 days after the injections to analyze the animals' gait.

KEY FINDINGS

Animals in the At group had higher alkaline phosphatase (ALP) activity, lower cortical and trabecular thickness, fewer trabeculae, higher expression of tartrate-resistant acid phosphatase (TRAP) and lower osteocalcin (OCN), higher cortical porosity, and lower moment of inertia and bone strength at the femoral neck. OT administration increased lipidic peroxidation and plasma superoxide dismutase (SOD), and provided, in the femoral neck, lower expression of TRAP and higher OCN, greater cortical and trabecular thickness, a greater number of trabeculae, bone mineral density (BMD), higher inertia bone strength, and lower cortical porosity. At + Ot group showed great similarity with the vehicle group, higher SOD, and BMD. An increase in stride length and no increase in base width of 21-month-old animals were observed after OT, unlike animal's vehicle or AT.

SIGNIFICANCE

Endogenous OT plays an important role in the regulation of bone remodeling during periestropause, and exogenous OT stands out as a potential preventive intervention in this period to improve bone quality with functional repercussions, possibly providing better gait activity.

Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis

Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.

Licochalcone A activation of glycolysis pathway has an anti-aging effect on human adipose stem cells

Licochalcone A (LA) is a chalcone flavonoid of Glycyrrhiza inflata, which has anti-cancer, antioxidant, anti-inflammatory, and neuroprotective effects. However, no anti-aging benefits of LA have been demonstrated in vitro or in vivo. In this study, we explored whether LA has an anti-aging effect in adipose-derived stem cells (ADSCs). We performed β-galactosidase staining and measured reactive oxygen species, relative telomere lengths, and P16^ink4a mRNA expression. Osteogenesis was assessed by Alizarin Red staining and adipogenesis by was assessed Oil Red O staining. Protein levels of related markers runt-related transcription factor 2 and lipoprotein lipase were also examined. RNA sequencing and measurement of glycolysis activities showed that LA significantly activated glycolysis in ADSCs. Together, our data strongly suggest that the LA have an anti-aging effect through activate the glycolysis pathway.

At the nuclear envelope of bone mechanobiology

The nuclear envelope and nucleoskeleton are emerging as signaling centers that regulate how physical information from the extracellular matrix is biochemically transduced into the nucleus, affecting chromatin and controlling cell function. Bone is a mechanically driven tissue that relies on physical information to maintain its physiological function and structure. Disorder that present with musculoskeletal and cardiac symptoms, such as Emery-Dreifuss muscular dystrophies and progeria, correlate with mutations in nuclear envelope proteins including Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, Lamin A/C, and emerin. However, the role of nuclear envelope mechanobiology on bone function remains underexplored. The mesenchymal stem cell (MSC) model is perhaps the most studied relationship between bone regulation and nuclear envelope function. MSCs maintain the musculoskeletal system by differentiating into multiple cell types including osteocytes and adipocytes, thus supporting the bone's ability to respond to mechanical challenge. In this review, we will focus on how MSC function is regulated by mechanical challenges both in vitro and in vivo within the context of bone function specifically focusing on integrin, β-catenin and YAP/TAZ signaling. The importance of the nuclear envelope will be explored within the context of musculoskeletal diseases related to nuclear envelope protein mutations and nuclear envelope regulation of signaling pathways relevant to bone mechanobiology in vitro and in vivo.

MyomiR-OsteomiR crosstalk induced by different modes and intensities of exercise training and its role in controlling osteogenic differentiation in old male Wistar rats

The crosstalk between skeletal muscles and other tissues such as bones is typically established via the secretion of myokines and myomiRs induced by exercise training (ET). The present study aimed at evaluating the relationship between changes made by different ET modes and intensities in myomiRs, osteomiRs, and other myogenic and osteogenic biomarkers in old male Wistar rats. To this end, a total number of 50 old (23 months of age) male Wistar rats were randomly assigned to four experimental groups, namely, moderate-intensity endurance training (MIET), high-intensity endurance training (HIET), moderate-intensity resistance training (MIRT), high-intensity resistance training (HIRT), and control (CON), each one comprised of 10 subjects. The study findings revealed positive correlations between myomiRs (i.e., miR-1) and myomiR-204a (r = 0.725; p = 0.042), myomiR-1, and runt-related transcription factor 2 (RUNX2) osteogenic marker (r = 0.869; p = 0.025) in the HIET group, myomiR-206 and peroxisome proliferator-activated receptor gamma (PPARγ) (r = 0.908; p = 0.012) in the MIRT group, myomiR-133a and osteomiR-133a (r = 0.971; p = 0.005) in the MIET group, myomiR-133a and osteomiR-204a in the MIRT group (r = 0.971; p = 0.004), and myomiR-133a and RUNX2 gene expression in the HIET group (r = 0.861; p = 0.027). It was concluded that myomiRs involved in myoblast-osteoblast differentiation might not alone regulate the myogenic and osteogenic targets in response to different modes and intensities of ET treatments.

Exercise and Diet: Uncovering Prospective Mediators of Skeletal Fragility in Bone and Marrow Adipose Tissue

PURPOSE OF REVIEW

To highlight recent basic, translational, and clinical works demonstrating exercise and diet regulation of marrow adipose tissue (MAT) and bone and how this informs current understanding of the relationship between marrow adiposity and musculoskeletal health.

RECENT FINDINGS

Marrow adipocytes accumulate in the bone in the setting of not only hypercaloric intake (calorie excess; e.g., diet-induced obesity) but also with hypocaloric intake (calorie restriction; e.g., anorexia), despite the fact that these states affect bone differently. With hypercaloric intake, bone quantity is largely unaffected, whereas with hypocaloric intake, bone quantity and quality are greatly diminished. Voluntary running exercise in rodents was found to lower MAT and promote bone in eucaloric and hypercaloric states, while degrading bone in hypocaloric states, suggesting differential modulation of MAT and bone, dependent upon whole-body energy status. Energy status alters bone metabolism and bioenergetics via substrate availability or excess, which plays a key role in the response of bone and MAT to mechanical stimuli. Marrow adipose tissue (MAT) is a fat depot with a potential role in-as well as responsivity to-whole-body energy metabolism. Understanding the localized function of this depot in bone cell bioenergetics and substrate storage, principally in the exercised state, will aid to uncover putative therapeutic targets for skeletal fragility.

Low Intensity Vibrations Augment Mesenchymal Stem Cell Proliferation and Differentiation Capacity during in vitro Expansion

A primary component of exercise, mechanical signals, when applied in the form of low intensity vibration (LIV), increases mesenchymal stem cell (MSC) osteogenesis and proliferation. While it is generally accepted that exercise effectively combats the deleterious effects of aging in the musculoskeletal system, how long-term exercise affects stem cell aging, which is typified by reduced proliferative and differentiative capacity, is not well explored. As a first step in understanding the effect of long-term application of mechanical signals on stem cell function, we investigated the effect of LIV during in vitro expansion of MSCs. Primary MSCs were subjected to either a control or to a twice-daily LIV regimen for up to sixty cell passages (P60) under in vitro cell expansion conditions. LIV effects were assessed at both early passage (EP) and late passage (LP). At the end of the experiment, P60 cultures exposed to LIV maintained a 28% increase of cell doubling and a 39% reduction in senescence-associated β-galactosidase activity (p < 0.01) but no changes in telomere lengths and p16^INK4a levels were observed. Prolonged culture-associated decreases in osteogenic and adipogenic capacity were partially protected by LIV in both EP and LP groups (p < 0.05). Mass spectroscopy of late passage MSC indicated a synergistic decrease of actin and microtubule cytoskeleton-associated proteins in both control and LIV groups while LIV induced a recovery of proteins associated with oxidative reductase activity. In summary, our findings show that the application of long-term mechanical challenge (+LIV) during in vitro expansion of MSCs for sixty passages significantly alters MSC proliferation, differentiation and structure. This suggests LIV as a potential tool to investigate the role of physical activity during aging.

Aging and low-intensity exercise change oxidative biomarkers in brain regions and radiographic measures of femur of Wistar rats

We investigated changes in oxidative biomarkers in brain regions such as brainstem, cerebellum, and cerebral cortex of 3-, 6-, 18-, 24-, and 30-month-old rats. We also assessed the effects of low-intensity exercise on these biomarkers in these regions of 6-, 18-, and 24-month-old rats that started exercise on a treadmill at 3, 15, and 21 months of age, respectively. Radiographic images of the femur were taken for all rats. A total of 25 rats (age: twelve 6-, ten 18-, ten 24-, and three 30-month-old rats) were used. Lipid hydroperoxide levels increased in cerebellum at 18 months. Total antioxidant activity exhibited lowest values in brainstem at 3 months. Superoxide dismutase activity did not exhibit significant changes during aging. Total thiol content exhibited lowest values in brain regions of 24- and 30-month-old rats. Exercise reduced total thiol content in brainstem at 6 months, but no change occurred in other regions and other ages. Femur increased its length and width and cortical thickness with advancing age. No change occurred in medullary width. Radiolucency increased and sclerosis was found in cortical and medullary bone with advancing age. Exercise reduced radiolucency and medullary sclerosis. Therefore, aging differentially changed oxidative biomarkers in different brain regions and radiographic measures of the femur. Low-intensity exercise only ameliorated some radiographic measurements of femur. Since the present study possessed limitations (small number of rats per group), a beneficial effect of regular low-intensity exercise on oxidative markers in brain cannot be ruled out.

Effects of different intensities of strength and endurance training on some osteometabolic miRNAs, Runx2 and PPARγ in bone marrow of old male wistar rats

Bone tissue is known as a living dynamic and complex organ in response to physical activity and mechanical loading such as exercise training; thus, the purpose of this study was to determine the effect of different intensities of strength and endurance training on expression of some osteometabolic miRNAs and runt-related transcription factor 2 (Runx2) and peroxisome proliferator-activated receptor γ (PPARγ) in bone marrow of old male Wistar rats. To this end, a total number of 50 male Wistar rats (aged 23 months, 438.27 g) were obtained from Pasteur Institute of Iran. The rats were randomized into five groups (10 rats/per group) including moderate endurance training (MET), high-intensity endurance training (HET), moderate-intensity resistance training (MRT), high-intensity resistance training (HRT), and control (CON). The four training groups completed 8 weeks of a training program, 5 days a week, according to the study protocol. To evaluate miR-133a, miR-103a, miR-204, and other adipogenic and osteogenic genes such as RUNX2 and PPARγ via real-time PCR, total RNA including mRNA and miRNA was isolated from the bone marrow. The statistical analysis was then performed using two-way analysis of variance (ANOVA). No significant differences in miR-133a (p = 0.197), miR-103a (p = 0.302), miR-204 (p = 0.539), RUNX2 (p = 0.960), and PPARγ (P = 0.872) were observed between the intervention groups and the control one. Furthermore, there were no significant differences in bone force (p = 0.641), fracture energy (p = 0.982), stress (p = 0.753), module (p = 0.147), and elongation (p = 0.292) variables between the intervention groups and the control group. Investigating molecular and cellular changes in the bone after such exercises in longer time could provide clearer results about the beneficial or harmful effects of these types of exercises in healthy and passive elderly people.

Oxytocin effects on osteoblastic differentiation of Bone Marrow Mesenchymal Stem Cells from adult and aging female Wistar rats

Recently, it has been suggested that oxytocin (OT) might play a role in the control of bone remodeling and in bone health of young and adult females. The purpose of this study was to evaluate the effect of osteogenic medium (OM) plus OT (OM + OT; 100 nmol/L) on osteoblastic differentiation of bone marrow mesenchymal stem cells (BMMSCs) from cyclic adult (12 months old) and acyclic aging (24 months old) female Wistar rats. After 14 days, OM + OT increased the oxytocin and oxytocin receptor in the BMMSCs from animals of both age groups relative to OM controls. Alkaline phosphatase activity was higher in the OM + OT than OM group in BMMSCs from 24-month-old female rats. OM + OT improved osteogenic differentiation, observed by anticipated mineralization and increased gene expression of bone morphogenetic protein 2, bone sialoprotein, osteopontin and osteocalcin in both aged relative to OM controls. These findings suggest a role for OT as an adjuvant to induce osteoblastic differentiation of BMMSCs from aged female rat.

Effects of strength training and raloxifene on femoral neck metabolism and microarchitecture of aging female Wistar rats

The aim of this study was to prevent female osteoporosis using strength training (ST), raloxifene (Ral) or a combination of ST plus Ral during the natural female aging process, specifically in the periestropause period. For a total of 120 days, aging female Wistar rats at 18-21 months of age performed ST on a ladder three times per week, and Ral was administered daily by gavage (1 mg/kg/day). Bone microarchitecture, areal bone mineral density, bone strength of the femoral neck, immunohistochemistry, osteoclast and osteoblast surface were assessed. We found that the treatments modulate the bone remodeling cycle in different ways. Both ST and Ral treatment resulted in improved bone microarchitecture in the femoral neck of rats in late periestropause. However, only ST improved cortical microarchitecture and bone strength in the femoral neck. Thus, we suggest that performing ST during the late period of periestropause is a valid intervention to prevent age-associated osteoporosis in females.