Linkage between muscle and bone: common catabolic signals resulting in osteoporosis and sarcopenia

Developing and comparing deep learning and machine learning algorithms for osteoporosis risk prediction

Introduction

Osteoporosis, characterized by low bone mineral density (BMD), is an increasingly serious public health issue. So far, several traditional regression models and machine learning (ML) algorithms have been proposed for predicting osteoporosis risk. However, these models have shown relatively low accuracy in clinical implementation. Recently proposed deep learning (DL) approaches, such as deep neural network (DNN), which can discover knowledge from complex hidden interactions, offer a new opportunity to improve predictive performance. In this study, we aimed to assess whether DNN can achieve a better performance in osteoporosis risk prediction.

Methods

By utilizing hip BMD and extensive demographic and routine clinical data of 8,134 subjects with age more than 40 from the Louisiana Osteoporosis Study (LOS), we developed and constructed a novel DNN framework for predicting osteoporosis risk and compared its performance in osteoporosis risk prediction with four conventional ML models, namely random forest (RF), artificial neural network (ANN), k-nearest neighbor (KNN), and support vector machine (SVM), as well as a traditional regression model termed osteoporosis self-assessment tool (OST). Model performance was assessed by area under 'receiver operating curve' (AUC) and accuracy.

Results

By using 16 discriminative variables, we observed that the DNN approach achieved the best predictive performance (AUC = 0.848) in classifying osteoporosis (hip BMD T-score ≤ -1.0) and non-osteoporosis risk (hip BMD T-score > -1.0) subjects, compared to the other approaches. Feature importance analysis showed that the top 10 most important variables identified by the DNN model were weight, age, gender, grip strength, height, beer drinking, diastolic pressure, alcohol drinking, smoke years, and economic level. Furthermore, we performed subsampling analysis to assess the effects of varying number of sample size and variables on the predictive performance of these tested models. Notably, we observed that the DNN model performed equally well (AUC = 0.846) even by utilizing only the top 10 most important variables for osteoporosis risk prediction. Meanwhile, the DNN model can still achieve a high predictive performance (AUC = 0.826) when sample size was reduced to 50% of the original dataset.

Conclusion

In conclusion, we developed a novel DNN model which was considered to be an effective algorithm for early diagnosis and intervention of osteoporosis in the aging population.

Correlation of body composition metrics with bone mineral density and computed tomography-based trabecular attenuation

PURPOSE

To investigate the relationship of body composition metrics with bone mineral density (BMD) and trabecular attenuation in a cohort of healthy individuals.

METHODS

We retrospectively analyzed data of consecutively evaluated individuals who underwent dual-energy X-ray absorptiometry (DXA) and abdominopelvic computed tomography (CT) on the same day during routine medical check-ups between January 2021 and December 2021. Trabecular attenuation was measured at L1 level, while body composition metrics, including skeletal muscle index (SMI), skeletal muscle attenuation (SMA), visceral fat index (VFI), and subcutaneous fat index (SFI), were measured at L3 level. The association of body composition metrics with BMD and trabecular attenuation was analyzed using partial correlation analysis.

RESULTS

A total of 634 patients (median age, 56 years; range 50-62 years; 392 men) were included. In men, the SMI and SMA were positively correlated with BMD and trabecular attenuation, both before (r, 0.157-0.344; p < 0.05) and after (r, 0.103-0.246; p < 0.05) adjusting for age and body mass index. The VFI showed negative correlations with trabecular attenuation in both men (r, -0.170; p = 0.001) and women (r, -0.394; p < 0.001), which remained significant after adjusting for age and body mass index (r, -0.181 to -0.122; p < 0.05).

CONCLUSION

Low skeletal muscle mass and attenuation were significantly correlated with low BMD and trabecular attenuation in men. Visceral adiposity was associated with reduced BMD and trabecular attenuation in both men and women, demonstrating a stronger correlation with trabecular attenuation.

Causal relationship between body mass index, type 2 diabetes and bone mineral density: Mendelian randomization

OBJECTIVE

To reveal the relationship between Body Mass Index(BMI), type 2 diabetes, and bone mineral density(BMD) using a mendelian randomization (MR) approach.

METHODS

GWAS data on BMI, type 2 diabetes, and BMD were selected from the IEU GWAS database at the University of Bristol.Univariable, multivariable, and mediated MR analyses were used to explore the relationship between BMI, type 2 diabetes, and BMD. beta(β) values were given, and three methods, including inverse variance weighting, MR-Egger regression, and weighted median, were used in this analysis.

RESULTS

Univariable mendelian randomization (UVMR) results showed that BMI and type 2 diabetes were positively associated with BMD. However, the association between BMI and BMD was insignificant in the multivariable Mendelian randomization (MVMR) analysis, while that between type 2 diabetes and BMD remained significant. Mediated MR analysis indicated that type 2 diabetes mediated the regulation of BMD by BMI.

CONCLUSION

This study provides evidence supporting a positive causal association between BMI, type 2 diabetes, and BMD. Type 2 diabetes acts as a mediator in the regulation of BMD by BMI, indicating that both BMI and type 2 diabetes exert a protective influence on BMD.

Global prevalence of osteosarcopenic obesity amongst middle aged and older adults: a systematic review and meta-analysis

PURPOSE

Osteosarcopenic obesity syndrome (OSO) is a recently recognized disorder encompassing osteopenia/osteoporosis, sarcopenia, and obesity. However, evidence in pooling knowledge regarding the prevalence of OSO worldwide is scarce. Hence, this review aimed to determine the pooled prevalence of OSO in middle-aged and older adults.

METHODS

We conducted systematic searches in Scopus, Embase, PubMed Central, MEDLINE, ScienceDirect, and Google Scholar from inception until October 2022. We evaluated the quality of the included studies using the Newcastle-Ottawa scale. The meta-analysis results using a random-effects model included the pooled prevalence and 95% confidence intervals (CIs).

RESULTS

We included 20 studies with a total of 23,909 participants. Most of the studies were of good quality. The final pooled prevalence of OSO in middle-aged and older adults worldwide was 8% (95% CI: 6%-11%; n = 20). Females (pooled prevalence = 9%; 95% CI:7%-12%; n = 17) had a higher burden of OSO than males (pooled prevalence = 5%; 95% CI:3%-8%; n = 11). We also found that the burden was higher among studies reporting OSO prevalence only in the elderly population (pooled prevalence = 13%; 95% CI: 9%-17%). The asymmetric nature of the funnel plot indicates the presence of publication bias. Additional sensitivity analysis did not reveal any significant variation in the pooled effect size estimation.

CONCLUSION

Approximately one in ten middle-aged and older adults suffer from OSO. The burden was highest among females and older adults. Diagnostic and intervention packages targeting such patients should be developed and implemented in high-risk settings.

Extracellular vesicles secreted from mouse muscle cells improve delayed bone repair in diabetic mice

Humoral factors that are secreted from skeletal muscles can regulate bone metabolism and contribute to muscle-bone relationships. Although extracellular vesicles (EVs) play important roles in physiological and pathophysiological processes, the roles of EVs that are secreted from skeletal muscles in bone repair have remained unclear. In the present study, we investigated the effects of the local administration of muscle cell-derived EVs on bone repair in control and streptozotocin-treated diabetic female mice. Muscle cell-derived EVs (Myo-EVs) were isolated from the conditioned medium from mouse muscle C2C12 cells by ultracentrifugation, after which Myo-EVs and gelatin hydrogel sheets were transplanted on femoral bone defect sites. The local administration of Myo-EVs significantly improved delayed bone repair that was induced by the diabetic state in mice 9 days after surgery. Moreover, this administration significantly enhanced the ratio of bone volume to tissue volume at the damaged sites 9 days after surgery in the control mice. Moreover, the local administration of Myo-EVs significantly blunted the number of Osterix-positive cells that were suppressed by the diabetic state at the damage sites after bone injury in mice. Additionally, Myo-EVs significantly blunted the mRNA levels of Osterix and alkaline phosphatase (ALP), and ALP activity was suppressed by advanced glycation end product 3 in ST2 cells that were treated with bone morphogenetic protein-2. In conclusion, we have shown for the first time that the local administration of Myo-EVs improves delayed bone repair that is induced by the diabetic state through an enhancement of osteoblastic differentiation in female mice.

Molecular basis and therapeutic potential of myostatin on bone formation and metabolism in orthopedic disease

Myostatin, a member of the transforming growth factor-β (TGF-β) superfamily, is a key autocrine/paracrine inhibitor of skeletal muscle growth. Recently, researchers have postulated that myostatin is a negative regulator of bone formation and metabolism. Reportedly, myostatin is highly expressed in the fracture area, affecting the endochondral ossification process during the early stages of fracture healing. Furthermore, myostatin is highly expressed in the synovium of patients with rheumatoid arthritis (RA) and is an effective therapeutic target for interfering with osteoclast formation and joint destruction in RA. Thus, myostatin is a potent anti-osteogenic factor and a direct modulator of osteoclast differentiation. Evaluation of the molecular pathway revealed that myostatin can activate SMAD and mitogen-activated protein kinase signaling pathways, inhibiting the Wnt/β-catenin pathway to synergistically regulate muscle and bone growth and metabolism. In summary, inhibition of myostatin or the myostatin signaling pathway has therapeutic potential in the treatment of orthopedic diseases. This review focused on the effects of myostatin on bone formation and metabolism and discussed the potential therapeutic effects of inhibiting myostatin and its pathways in related orthopedic diseases.

Sex differences in musculoskeletal injury and disease risks across the lifespan: Are there unique subsets of females at higher risk than males for these conditions at distinct stages of the life cycle?

Sex differences have been reported for diseases of the musculoskeletal system (MSK) as well as the risk for injuries to tissues of the MSK system. For females, some of these occur prior to the onset of puberty, following the onset of puberty, and following the onset of menopause. Therefore, they can occur across the lifespan. While some conditions are related to immune dysfunction, others are associated with specific tissues of the MSK more directly. Based on this life spectrum of sex differences in both risk for injury and onset of diseases, a role for sex hormones in the initiation and progression of this risk is somewhat variable. Sex hormone receptor expression and functioning can also vary with life events such as the menstrual cycle in females, with different tissues being affected. Furthermore, some sex hormone receptors can affect gene expression independent of sex hormones and some transitional events such as puberty are accompanied by epigenetic alterations that can further lead to sex differences in MSK gene regulation. Some of the sex differences in injury risk and the post-menopausal disease risk may be "imprinted" in the genomes of females and males during development and sex hormones and their consequences only modulators of such risks later in life as the sex hormone milieu changes. The purpose of this review is to discuss some of the relevant conditions associated with sex differences in risks for loss of MSK tissue integrity across the lifespan, and further discuss several of the implications of their variable relationship with sex hormones, their receptors and life events.

Osteoarthritis as an Umbrella Term for Different Subsets of Humans Undergoing Joint Degeneration: The Need to Address the Differences to Develop Effective Conservative Treatments and Prevention Strategies

Osteoarthritis (OA) of joints such as the knee and hip are very prevalent, and the number of individuals affected is expected to continue to rise. Currently, conservative treatments after OA diagnosis consist of a series of increasingly invasive interventions as the degeneration and pain increase, leading very often to joint replacement surgery. Most interventions are focused on alleviating pain, and there are no interventions currently available that stop and reverse OA-associated joint damage. For many decades OA was considered a disease of cartilage, but it is now considered a disease of the whole multi-tissue joint. As pain is the usual presenting symptom, for most patients, it is not known when the disease process was initiated and what the basis was for the initiation. The exception is post-traumatic OA which results from an overt injury to the joint that elevates the risk for OA development. This scenario leads to very long wait lists for joint replacement surgery in many jurisdictions. One aspect of why progress has been so slow in addressing the needs of patients is that OA has been used as an umbrella term that does not recognize that joint degeneration may arise from a variety of mechanistic causes that likely need separate analysis to identify interventions unique to each subtype (post-traumatic, metabolic, post-menopausal, growth and maturation associated). A second aspect of the slow pace of progress is that the bulk of research in the area is focused on post-traumatic OA (PTOA) in preclinical models that likely are not clearly relevant to human OA. That is, only ~12% of human OA is due to PTOA, but the bulk of studies investigate PTOA in rodents. Thus, much of the research community is failing the patient population affected by OA. A third aspect is that conservative treatment platforms are not specific to each OA subset, nor are they integrated into a coherent fashion for most patients. This review will discuss the literature relevant to the issues mentioned above and propose some of the directions that will be required going forward to enhance the impact of the research enterprise to affect patient outcomes.

Density and Fat Fraction of the Psoas, Paraspinal, and Oblique Muscle Groups Are Associated With Lumbar Vertebral Bone Mineral Density in a Multi-Ethnic Community-Living Population: The Multi-Ethnic Study of Atherosclerosis

Low vertebral bone mass is a major risk factor for vertebral compression fractures. Although sarcopenia has been shown to be associated with low bone mineral density (BMD), it is not known whether trunk musculature is directly associated with lumbar BMD, and whether exercise modifies this association. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we sought to determine the association of muscle density and fat fraction of the psoas, paraspinal, and oblique muscle groups with L₃ lumbar volumetric BMD, and whether these associations were modified by exercise. We obtained L₃ vBMD measurements, and fat and muscle measurements (in Hounsfield units [HU]) from abdominal computed tomography (CT) scans spanning the L₂ -L₄ intervertebral disc spaces. Muscle density was defined as the mean HU value for a muscle group area. Fat fraction was calculated as the mean HU value for the muscle group fat area/total muscle group area (cm² ). Exercise data were self-reported (MET-minute/week). We utilized multivariable linear regression to evaluate these associations, stratified by gender, and adjusting for demographics, body mass index (BMI), smoking status, impaired fasting glucose, and corticosteroid and anti-resorptive medication use. Among 1923 MESA participants, mean ± standard deviation (SD) age was 62 ± 10 years, 49% were female, 40% white, 21% black, 26% Hispanic/Latino, and 13% Chinese. In fully adjusted analysis, for every 1-SD higher psoas fat fraction, there was a 3.19-SD lower L₃ vBMD in men and 4.3-SD lower L₃ vBMD in women (p < 0.001). For every 1-SD higher psoas density, there was a 0.2-SD higher L₃ vBMD (p < 0.001) in men and 0.19-SD higher L₃ vBMD (p < 0.001) in women. Findings were similar for paraspinal and oblique muscles. Intentional exercise did not modify these associations. In men and women, trunk muscle density was positively associated with higher lumbar BMD, suggesting a local association. Future studies are warranted to determine the temporality of this association. © 2022 American Society for Bone and Mineral Research (ASBMR).

A bi-directional Mendelian randomization study of the sarcopenia-related traits and osteoporosis

Both sarcopenia and osteoporosis are common geriatric diseases causing huge socioeconomic burdens, and clinically, they often occur simultaneously. Observational studies have found a controversial correlation between sarcopenia and osteoporosis and their causal relationship is not clear. Therefore, we performed a bi-directional two-sample Mendelian randomization (MR) analysis to assess the potential causal relationship between sarcopenia-related traits (hand grip strength, lean mass, walking pace) and osteoporosis. Our analysis was performed by applying genetic variants obtained from the UK Biobank and the GEnetic Factors for OSteoporosis (GEFOS) datasets. We used inverse-variance weighted (IVW) and several sensitivity analyses to estimate and cross-validate the potential causal relationship in this study. We found that bone mineral density (BMD) was causally positively associated with left-hand grip strength (β = 0.017, p-value = 0.001), fat-free mass (FFM; right leg FFM, β = 0.014, p-value = 0.003; left arm FFM, β = 0.014, p-value = 0.005), but not walking pace. Higher hand grip strength was potentially causally associated with increased LS-BMD (right-hand grip strength, β = 0.318, p-value = 0.001; left-hand grip strength, β = 0.358, p-value = 3.97 × 10-4). In conclusion, osteoporosis may be a risk factor for sarcopenia-related traits and muscle strength may have a site-specific effect on BMD.

Role of peripheral myelin protein 22 in chronic exercise-induced interactions of muscle and bone in mice

Exercise is important for the prevention and treatment of sarcopenia and osteoporosis. Although the interactions between skeletal muscles and bone have recently been reported, the myokines linking muscle to bone during exercise remain unknown. We previously revealed that chronic exercise using treadmill running blunts ovariectomy-induced osteopenia in mice. We herein performed an RNA sequence analysis of the gastrocnemius and soleus muscles of male mice with or without chronic exercise to identify the myokines responsible for the effects of chronic exercise on the muscle/bone relationship. We extracted peripheral myelin protein 22 (PMP22) as a humoral factor that was putatively induced by chronic exercise in the soleus and gastrocnemius muscles of mice from the RNA sequence analysis. Chronic exercise significantly enhanced the expression of PMP22 in the gastrocnemius and soleus muscles of female mice. PMP22 suppressed macrophage-colony stimulating factor and receptor activator factor κB ligand-induced increases in the expression of osteoclast-related genes and osteoclast formation from mouse bone marrow cells. Moreover, PMP22 significantly inhibited osteoblast differentiation, alkaline phosphatase activity, and mineralization in mouse osteoblast cultures; however, the overexpression of PMP22 did not affect muscle phenotypes in mouse muscle C2C12 cells. A simple regression analysis revealed that PMP22 mRNA levels in the gastrocnemius and soleus muscles were positively related to cortical bone mineral density at the femurs of mice with or without chronic exercise. In conclusion, we identified PMP22 as a novel myokine induced by chronic exercise in mice. We first showed that PMP22 suppresses osteoclast formation and the osteoblast phenotype in vitro.

Evaluation of bone mineral density and body compositions interrelation in young and middle-aged male patients with Crohn's disease by quantitative computed tomography

BACKGROUND

The aim of this study was to investigate the characteristics of bone mineral density (BMD) and body compositions, and the impact of body compositions on BMD in young and middle-aged male patients with Crohn's disease (CD).

METHODS

Patients with CD (n = 198) and normal controls (n = 123) underwent quantitative computed tomography (QCT) examination of lumbar vertebrae 1-3 (L1-3). The BMD and bone geometric parameters were measured and outputted by QCT post-process software. Meanwhile, body composition parameters, including subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), lean mass (LM), and muscles mass around lumbar vertebrae were also acquired by QCT. Blood indicators [interleukin (IL)-6, IL-8, tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), Ca, and P] were collected from clinical medical records. Independent t-test was used to compare these variables between the CD group and the normal control group.

RESULTS

There was no significant difference in age, height, and weight between the CD group and the control group (p > 0.05), indicating that the sample size was relatively balanced. Mean BMD in the CD group were lower than those in the control group, but the difference was not statistically significant (p > 0.05). The bone geometric parameters of the CD group, including cortical area/density (Ct. Ar, Ct. BMD) and trabecular area/density (Tb. Ar and Tb. BMD), were significantly lower than those of the control group (p < 0.05), so were the body composition parameters including total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), lean mass (LM), and muscles mass (p < 0.05). In addition, the level of plasma IL-6, IL-8, CRP, and TNF-α of the CD group were higher than those of the control group (p < 0.05). On the contrary, the body mass index (BMI) and serum Ca and P levels of the CD group were lower than those of the control group (p < 0.05). Through multiple linear regression analysis, Tb. BMD, VAT, Ct. Ar, LM, Ca, and IL-8 entered the regression model and revealed a significant contribution to BMD.

CONCLUSIONS

Patients with CD could suffer from reduction in BMD. However, the parameters of bone geometric parameters are more sensitive and accurate than BMD changes. Among them, Tb. BMD, VAT, Ct. Ar, and LM have significant effects on BMD reduction.

Association of Sarcopenia with Osteopenia and Osteoporosis in Community-Dwelling Older Korean Adults: A Cross-Sectional Study

Sarcopenia and bone disorders, such as osteopenia and osteoporosis, are common musculoskeletal disorders in older adults. Therefore, this study aimed to establish the association between sarcopenia and bone disorders such as osteoporosis and osteopenia according to sex. We analyzed 3077 participants from the 2008-2011 Korean National Health and Nutrition Examination Survey aged 65 years or older. After adjusting for all covariates, such as physical examinations, exercise, and nutrient intake (model 4), the odds ratios for the association between sarcopenia and bone disorders were 2.051 (95% confidence interval [CI]: 1.498-2.808) in osteopenia and 2.258 (95% CI: 1.584-3.218) in osteoporosis. However, when sex was analyzed separately, the odds ratio was significantly different in men (osteopenia-2.068, 95% CI: 1.462-2.924; osteoporosis-3.247, 95% CI: 1.953-5.399), but not in women. Therefore, the results of this study show an association between sarcopenia and bone disorders in older Korean adults. Sarcopenia is significantly related to osteopenia and osteoporosis, especially in men, when stratified by sex.

Associations Between Surrogates of Skeletal Muscle Mass and History of Bone Fracture in Patients with Chronic Kidney Disease: The Fukuoka Kidney disease Registry (FKR) Study

Patients with chronic kidney disease (CKD) are at increased risks of both sarcopenia and fragility fractures. However, information on the association between skeletal muscle mass (SMM) and the risk of bone fractures in patients with CKD is lacking. We performed a cross-sectional analysis of 4146 patients with CKD using the baseline dataset of the Fukuoka Kidney disease Registry Study, as a multicenter, prospective cohort study of pre-dialysis CKD patients. The main measure was estimated SMM (eSMM) calculated using an equation validated by bioelectrical impedance analysis with two independent datasets of 100 and 81 CKD patients. The main outcome was historical bone fractures. The associations between sex-specific quartiles (Q1-Q4) of eSMM and fracture history were assessed by logistic regression analyses. The prevalence of a history of fractures increased and eSMM decreased with progressive CKD stages. Among the 4146 patients, 249 had prior bone fractures, including 111 patients in Q1 (lowest quartile), 65 in Q2, 46 in Q3, and 27 in Q4 (highest quartile). A multivariable-adjusted model revealed that patients in Q1 had a significantly higher odds ratio (95% confidence interval) for bone fracture history than those in Q4 (reference): Q1, 2.77 (1.32-5.80); Q2, 1.95 (1.05-3.65); and Q3, 1.57 (0.90-2.75) (P-value for trend < 0.001). Similar associations were obtained when other skeletal muscle surrogates were applied: serum creatinine to serum cystatin C and daily urinary creatinine excretion. These results suggest that a lower eSMM is associated with an increased prevalence of historical bone fractures in pre-dialysis CKD patients.

The role of estrogens in osteosarcopenia: from biology to potential dual therapeutic effects

Osteoporosis and sarcopenia are two conditions associated with aging and characterized by a simultaneous decline in bone and muscle mass, respectively. These conditions share common risk factors (genetic, endocrine, nutritional and lifestyle factors) and biological pathways that often co-exist in a syndrome known as osteosarcopenia. Among the endocrine causes, estrogens play a critical role, especially in women. Estrogens have been demonstrated to exert a positive effect on bone and muscle development and maintenance. For this reason, menopause is characterized by a loss in bone mineral density and skeletal muscle quality and quantity. To date, studies indicate a positive effect of hormonal therapy on the prevention and management of osteoporosis, to the point that estrogen is prescribed as a first-line treatment for osteoporosis by the major international authorities. While results on sarcopenia are still disputable, such that estrogens are not recommended to prevent muscle loss in postmenopausal women, increased response to anabolic stimuli with estrogen therapy suggests similar beneficial effects on muscle as seen with bone, particularly when combined with resistance exercise.

[Research progress on mechanism of myokines regulating bone tissue cells]

Objective

To review the effects and mechanisms of various myokines secreted by skeletal muscle on various bone tissue cells.

Methods

Literature related to myokines and their regulation of bone tissue cells was reviewed and analyzed comprehensively in recent years.

Results

Bone and skeletal muscle are important members of the motor system, and they are closely related in anatomy, genetics, and physiopathology. In recent years, it has been found that skeletal muscle can secrete a variety of myokines to regulate bone marrow mesenchymal stem cells, osteoblasts, osteoclasts, and bone cells; these factors mutual crosstalk between myoskeletal unit, contact each other and influence each other, forming a complex myoskeletal micro-environment, and to some extent, it has a positive impact on bone repair and reconstruction.

Conclusion

Myokines are potential targets for the dynamic balance of bone tissue cells. In-depth study of its mechanism is helpful to the prevention and treatment of myoskeletal diseases.

Type II collagen from squid cartilage mediated myogenic IGF-I and irisin to activate the Ihh/PThrp and Wnt/β-catenin pathways to promote fracture healing in mice

Fractures are the most common large-organ, traumatic injury in humans. The fracture healing stage includes the inflammatory stage (0-5d), cartilage callus stage (5-14d) and hard callus stage (14-21d). All mice underwent open tibial fracture surgery and were treated with saline, Glu or SCII for 21d. Calluses were harvested 5d, 10d and 21d after fracture. Compared with the model group, SCII significantly decreased TNF-α and increased aggrecan serum levels by 5d. H&E results showed that fibrous calluses were already formed in the SCII group and that chondrocytes had begun to proliferate. By 10d, the chondrocytes in the SCII group became hypertrophic and mineralized, and the serum TGF-β and Col-Iα levels were significantly increased, which indicated that the mice with SCII treatment rapidly passed the cartilage repair period and new bone formation was accelerated. Skeletal muscle repaired bones through muscle paracrine factors. IGF-1 and irisin are the two major secretory cytokines. The results showed that the content of muscle homogenate IGF-1 in the SCII group reached the peak at 10d, followed by the up-regulation of Ihh, Patched, Gli1 and Col10α in the callus through the bone surface receptor IGF-1R. Besides, SCII also significantly elevated the muscle irisin level (10 and 21d), and then increased Wnt10b, LRP5, β-catenin and Runx2 expression in the callus by receptor αVβ5. These results suggest that SCII can accelerate the process of endochondral osteogenesis and promote fracture healing through activating the Ihh/PThrp and Wnt/β-catenin pathways by regulating muscle paracrine factors. To our knowledge, this is the first study to investigate the effect of marine-derived collagen on fracture healing. This study may provide a theoretical basis for the high-value application of the laryngeal cartilage of squid in the future.

Effects of fluid flow shear stress to mouse muscle cells on the bone actions of muscle cell-derived extracellular vesicless

The interactions between skeletal muscle and bone have been recently noted, and muscle-derived humoral factors related to bone metabolism play crucial roles in the muscle/bone relationships. We previously reported that extracellular vesicles from mouse muscle C2C12 cells (Myo-EVs) suppress osteoclast formation in mice. Although mechanical stress is included in extrinsic factors which are important for both muscle and bone, the detailed roles of mechanical stress in the muscle/bone interactions have still remained unknown. In present study, we examined the effects of fluid flow shear stress (FFSS) to C2C12 cells on the physiological actions of muscle cell-derived EV. Applying FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed osteoclast formation and several osteoclast-related gene levels in mouse bone marrow cells in the presence of receptor activator nuclear factor κB ligand (RANKL). Moreover, FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed mitochondria biogenesis genes during osteoclast formation with RANKL treatment. In addition, FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed osteoclast formation and several osteoclast-related gene levels in Raw264.7 cells in the presence of RANKL. Small RNA-seq-analysis showed that FFSS elevated the expression of miR196a-5p and miR155-5p with the suppressive actions of osteoclast formation and low expression in mouse bone cells. On the other hand, muscle cell-derived EVs with or without FFSS to C2C12 cells did not affect the expression of osteogenic genes, alkaline phosphatase activity and mineralization in mouse osteoblasts. In conclusion, we first showed that FFSS to C2C12 cells enhances the suppressive effects of muscle cell-derived EVs on osteoclast formation in mouse cells. Muscle cell-derived EVs might be partly involved in the effects of mechanical stress on the muscle/bone relationships.

Evaluation of myostatin as a possible regulator and marker of skeletal muscle-cortical bone interaction in adults

INTRODUCTION

Bone mass was recently reported to be related to skeletal muscle mass in humans, and a decrease in cortical bone is a risk factor for osteoporosis. Because circulating myostatin is a factor that primarily controls muscle metabolism, this study examined the role of myostatin in bone mass-skeletal muscle mass interactions.

METHODS

The subjects were 375 middle-aged community residents with no history of osteoporosis or sarcopenia who participated in a health check-up. Cortical bone thickness and cancellous bone density were measured by ultrasonic bone densitometry in a health check-up survey. The subjects were divided into those with low cortical bone thickness (LCT) or low cancellous bone density (LBD) and those with normal values (NCT/NBD). Bone metabolism markers (TRACP-5b, etc.), skeletal muscle mass, serum myostatin levels, and lifestyle were then compared between the groups.

RESULTS

The percentage of diabetic participants, TRACP-5b, and myostatin levels were significantly higher, and the frequency of physical activity, skeletal muscle mass, grip strength, and leg strength were significantly lower in the LCT group than in the NCT group. The odds ratio (OR) of high myostatin levels in the LCT group compared with the NCT group was significant (OR 2.17) even after adjusting for related factors. Between the low cancellous bone density (LBD) and normal cancellous bone density (NBD) groups, significant differences were observed in the same items as between the LCT and NCT groups, but no significant differences were observed in skeletal muscle mass and blood myostatin levels. The myostatin level was significantly negatively correlated with cortical bone thickness and skeletal muscle mass.

CONCLUSIONS

A decrease in cortical bone thickness was associated with a decrease in skeletal muscle mass accompanied by an increase in the blood myostatin level. Blood myostatin may regulate the bone-skeletal muscle relationship and serve as a surrogate marker of bone metabolism, potentially linking muscle mass to bone structure.

Sarcopenia, obesity, osteoporosis and old age

Modern concepts about body composition in the elderly are described in the review. Particular attention is paid to possible causes and pathogenetic aspects of sarcopenia, as well as modern diagnostic approaches to its recognition. The ageing process is inevitably combined with diverse changes in body composition. This age-related evolution can be described by three main processes: a decrease in the growth and mineral density of bone tissue (osteopenia and osteoporosis); progressive decrease in muscle mass; an increase in adipose tissue (sarcopenia and sarcopenic obesity) with its redistribution towards central and visceral fat accumulation. Sarcopenia and osteoporosis are considered the main geriatric syndromes. These pathological conditions contribute to a significant decrease in the quality of life in the elderly; create conditions for the loss of independence and require long-term care, increase the frequency of hospitalizations and ultimately result in adverse outcomes.

Association of some dietary ingredients, vitamin D, estrogen, and obesity polymorphic receptor genes with bone mineral density in a sample of obese Egyptian women

Background

Although many environmental factors play an important role in bone mass density (BMD) variation, genetic influences account for 60–85% of individual variance. The aim of this study was to find the interaction between some dietary ingredients, vitamin D, estrogen, and obesity polymorphic receptor genes, among a sample of obese Egyptian women. This was a cross sectional study included 97 women (aged 25–60 years). Data on anthropometry, dietary intake, BMD, biochemical, and genetic analyses were collected.

Results

Osteoporosis was high among women had dominant Taq1 vitamin D receptor gene while osteoporosis was less common among the homozygous Apa1 receptor gene women. Both genes in their two forms did not show any effect on serum vitamin D. Heterozygous types of osteoporotic women carried both genes revealed a slight but significant decrease in level of serum calcium. Xba1 estrogen receptor gene was identified only in a homozygous type while the heterozygous Pvu11 estrogen receptors gene has been identified among both osteoporotic and non-osteoporotic women, this gene was associated with higher BMI in both groups compared to the homozygous receptor gene. Mutant types of genotype FTOrs99 and FTOrs80 obesity receptors genes were less common (4.44%, 11%) among participants. Both of these genes were associated with the highest value of BMI and caloric daily intake, fat, and saturated fatty acid that were more prominent among osteoporotic women.

Conclusion

There is significant association between vitamin D, estrogen, obesity receptors genes, special nutrients, and osteoporosis. Increased BMI, calories, and fat intake lead to rise of genetic predisposition and susceptibility to osteoporosis.

The muscle to bone axis (and viceversa): An encrypted language affecting tissues and organs and yet to be codified?

Skeletal muscles and bone tissue form the musculoskeletal apparatus, a complex system essential for the voluntary movement. The loss of muscle mass and muscle strength is often associated with a loss of bone mass, in a "hazardous duet" which implies the co-existence of sarcopenia-osteoporosis and exposes patients to a deterioration in quality of life and increased mortality. From the mechanostat theory to the recent definition of the osteosarcopenia syndrome, many aspects of muscle-bone interaction have been investigated in recent decades. The mechanical interaction is now accepted, considering the close anatomical relationship between the two tissues, however, much remains to be discovered regarding the biochemical muscle-bone interaction. Skeletal muscle has been defined as an endocrine organ capable of exerting an action on other tissues. Myokines, bioactive polypeptides released by the muscle, could represent the encrypted message in the communication between muscle and bone. These two tissues have a reciprocal influence on their metabolisms and respond in a similar way to the multiple external factors. The aim of this review is to stimulate the understanding of the encrypted language between muscle and bone, highlighting the role of catabolic pathways and oxidative stress in the musculoskeletal apparatus to elucidate the shared mechanisms and the similarity of response to the same stimuli by different tissues. Our understanding of muscle-bone interactions it could be useful to identify and develop new strategies to treat musculoskeletal diseases, together with pharmacological, nutritional and exercise-based approaches, which are already in use for the treatment of these pathologies.

Hand grip strength and early mortality after hip fracture

This research describes the risk of death in elderly after hip fracture according to their strength, measured by hand grip. The result is that the weaker the patient, the greater the risk of death after hip fracture, highlighting the need to assess the force in those patients. For the coming years, most of hip fractures will occur in developing countries. It has been described that low muscular strength, measured by grip strength, increases the risk of mortality in those with hip fracture, in both high-and low- income countries. The objective of this study was to determine the mortality among patients with hip fracture and lower hand grip strength (HGS).

MATERIAL AND METHODS

We conducted a cohort and longitudinal study at Hip and Pelvic Surgery Department of a tertiary hospital, in Monterrey, Mexico. The study included patients aged over of 69, admitted for hip fracture surgery from February 1st 2013 to July 31st 2014. HGS measurement was performed by a trained physician at arrival to emergency department prior to surgery; clinimetric variables were asked, and a complete medical history was included.

RESULTS

A total of 670 patients were included in the study and grouped in different tertiles according to hand grip strength. During follow-up, there were 112 deaths (17.4%), 61 (27.5%) in tertile 1, 37 (17.1%) in tertile 2, and 14 (6.8%) in tertile 3, p < 0.001. The association remained significant after adjusting for confounding variables. Less than 5% of patients discharged from hospital were identified with osteoporosis.

CONCLUSION

Lower hand grip strength in patients with a hip fracture is associated with high mortality after hip fracture.

Circulating irisin is linked to bone mineral density in geriatric Chinese men

Background

While there is evidence of a link between irisin and bone metabolism, prior clinical evaluations have been limited to women with postmenopausal osteoporosis. The primary goal of this evaluation is to examine the relationship between irisin and bone mineral density (BMD) in geriatric Chinese men experiencing osteoporosis or osteopenia.

Methods

In this case-control study, 43 geriatric Chinese men were verified as having osteoporosis or osteopenia via dual-energy X-ray light absorption spectrophotometry, and 24 subjects were accepted as the controls. Serum irisin levels were detected by a commercial ELISA kit.

Results

Serum irisin levels were lowered in geriatric Chinese men with osteopenia and osteoporosis, and multiple linear regression analysis revealed that the serum irisin level is an independent factor impacting BMD.

Conclusions and discussion

Our data confirm a positive correlation between irisin levels and BMD in geriatric Chinese men. Irisin has a protective effect on bone health dependent on BMD, but large clinical trials are still required to verify the irisin and BMD relationship.

Roles of Olfactomedin 1 in Muscle and Bone Alterations Induced by Gravity Change in Mice

Microgravity causes both muscle and bone loss. Although we previously revealed that gravity change influences muscle and bone through the vestibular system in mice, its detailed mechanism has not been elucidated. In this study, we investigated the roles of olfactomedin 1 (OLFM1), whose expression was upregulated during hypergravity in the soleus muscle, in mouse bone cells. Vestibular lesion significantly blunted OLFM1 expression in the soleus muscle and serum OLFM1 levels enhanced by hypergravity in mice. Moreover, a phosphatidylinositol 3-kinase inhibitor antagonized shear stress-enhanced OLFM1 expression in C2C12 myotubes. As for the effects of OLFM1 on bone cells, OLFM1 inhibited osteoclast formation from mouse bone marrow cells and mouse preosteoclastic RAW264.7 cells. Moreover, OLFM1 suppressed RANKL expression and nuclear factor-κB signaling in mouse osteoblasts. Serum OLFM1 levels were positively related to OLFM1 mRNA levels in the soleus muscle and trabecular bone mineral density of mice. In conclusion, we first showed that OLFM1 suppresses osteoclast formation and RANKL expression in mouse cells.

Extracellular vesicles secreted from mouse muscle cells suppress osteoclast formation: Roles of mitochondrial energy metabolism

Recent reports have described the interactions of muscle and bone. Various muscle-derived humoral factors, known as myokines, affect bone. Although extracellular vesicles (EVs) play a vital role in physiological and pathophysiological processes by transferring their contents to distant tissues during bone metabolism, the roles of EVs in the muscle-bone interactions remain unknown. In the present study, we investigated the effects of EVs secreted from mouse muscle C2C12 cells on mouse bone cells and mitochondrial biogenesis. EVs secreted from C2C12 cells (Myo-EVs) were isolated from the conditioned medium of C2C12 cells by ultracentrifugation. Myo-EVs suppressed osteoclast formation as well as the expression of tartrate-resistant acid phosphatase, cathepsin K, nuclear factor of activated T-cells cytoplasmic 1 and dendritic cell-specific transmembrane protein induced by receptor activator of nuclear factor κB ligand (RANKL) in mouse bone marrow cells and preosteoclastic Raw264.7 cells. Moreover, Myo-EVs suppressed oxygen consumption and mRNA expression of the mitochondrial biogenesis markers enhanced by RANKL in these cells. However, Myo-EVs did not affect the phenotypes or mitochondrial biogenesis of mouse primary osteoblasts. In conclusion, the present study showed for the first time that Myo-EVs suppress osteoclast formation and mitochondrial energy metabolism in mouse bone marrow and Raw264.7 cells. EVs secreted from skeletal muscles might be a crucial mediator of muscle-bone interactions.

Sarcopenia: Current treatments and new regenerative therapeutic approaches

Sarcopenia is characterized by loss of muscle and reduction in muscle strength that contributes to higher mortality rate and increased incidence of fall and hospitalization in the elderly. Mitochondria dysfunction and age-associated inflammation in muscle are two of the main attributors to sarcopenia progression. Recent clinical trials on sarcopenia therapies such as physical exercise, nutraceutical, and pharmaceutical interventions have revealed that exercise is the only effective strategy shown to alleviate sarcopenia. Unlike nutraceutical and pharmaceutical interventions that showed controversial results in sarcopenia alleviation, exercise was found to restore mitochondria homeostasis and dampen inflammatory responses via a complex exchange of myokines and osteokines signalling between muscle and bone. However, as exercise have limited benefit to immobile patients, the use of stem cells and their secretome are being suggested to be novel therapeutics that can be catered to a larger patient population owing to their mitochondria restoration effects and immune modulatory abilities. As such, we reviewed the potential pros and cons associated with various stem cell types/secretome in sarcopenia treatment and the regulatory and production barriers that need to be overcome to translate such novel therapeutic agents into bedside application.

Translational potential: This review summarizes the causes underlying sarcopenia from the perspective of mitochondria dysfunction and age-associated inflammation, and the progress of clinical trials for the treatment of sarcopenia. We also propose therapeutic potential of stem cell therapy and bioactive secretome for sarcopenia.

Understanding vestibular-related physiological functions could provide clues on adapting to a new gravitational environment

The peripheral vestibular organs are sensors for linear acceleration (gravity and head tilt) and rotation. Further, they regulate various body functions, including body stability, ocular movement, autonomic nerve activity, arterial pressure, body temperature, and muscle and bone metabolism. The gravitational environment influences these functions given the highly plastic responsiveness of the vestibular system. This review demonstrates that hypergravity or microgravity induces changes in vestibular-related physiological functions, including arterial pressure, muscle and bone metabolism, feeding behavior, and body temperature. Hopefully, this review contributes to understanding how human beings can adapt to a new gravitational environment, including the moon and Mars, in future.

Low muscle mass is associated with osteoporosis: A nationwide population-based study

OBJECTIVES

To assess the association between low muscle mass and osteoporosis in the Korean general population.

METHODS

We analyzed 14,429 participants (6,261 men and 8,168 women) from the 2009-2011 Korean National Health and Nutrition Examination Survey (KNHANES) aged 20 years or more.

MAIN OUTCOME MEASURE

The association of low muscle mass with osteoporosis was investigated using multivariate logistic regression models that included age, marital status, residence, current smoking, monthly drinking, physical activities, strength exercise, comorbidity, and the use of dietary supplements, and in women postmenopausal status and experience of pregnancy.

RESULTS

After adjusting for covariates, low muscle mass was significantly associated with osteoporosis in the lumbar spine and femoral neck in both men (lumbar spine: OR 1.73, 95 % CI 1.08-2.76; femoral neck: OR 3.39, 95 % CI 1.69-6.80) and women (lumbar spine: OR 1.52, 95 % CI 1.17-1.97; femoral neck: OR 2.09, 95 % CI 1.56-2.80). Also, the association between low muscle mass and osteoporosis was significant in men and women in every age group except for men aged 50-64 years.

CONCLUSION

Low muscle mass was significantly associated with osteoporosis in both men and women for all age groups, except for men aged 50-64 years.

A High-Intensity Exercise Intervention Improves Older Women Lumbar Spine and Distal Tibia Bone Microstructure and Function: A 20-Week Randomized Controlled Trial

Introduction: The effects of ageing on bone can be mitigated with different types of physical training, such as power training. However, stimuli that combine increasing external and internal loads concomitantly may improve bone quality. The goal of this study was to assess the efficacy of a combined power and plyometric training on lumbar spine and distal tibia microstructure and function. Methods: 38 sedentary elderly women between 60 and 70 years were randomly allocated in experimental (N = 21) and control group (N = 17). The effects of the 20-week protocol on lumbar spine microstructure and tibia microstructure and function were assessed by trabecular bone score (TBS), high resolution peripheral quantitative computed tomography (HR-pQCT) and microfinite element analysis. Results: when compared to the effects found in the control group, the experimental group showed significant improvements in lumbar spine TBS (Hedges' g = 0.77); and in distal tibia trabecular thickness (g = 0.82) and trabecular bone mineral density (g=0.63). Conclusion: our findings underscore the effectiveness of the proposed intervention, suggesting it as a new strategy to slow down and even reverse the structural and functional losses in the skeletal system due to ageing.

Myokines: The endocrine coupling of skeletal muscle and bone

Bone and skeletal muscle are integrated organs and their coupling has been considered mainly a mechanical one in which bone serves as attachment site to muscle while muscle applies load to bone and regulates bone metabolism. However, skeletal muscle can affect bone homeostasis also in a non-mechanical fashion, i.e., through its endocrine activity. Being recognized as an endocrine organ itself, skeletal muscle secretes a panel of cytokines and proteins named myokines, synthesized and secreted by myocytes in response to muscle contraction. Myokines exert an autocrine function in regulating muscle metabolism as well as a paracrine/endocrine regulatory function on distant organs and tissues, such as bone, adipose tissue, brain and liver. Physical activity is the primary physiological stimulus for bone anabolism (and/or catabolism) through the production and secretion of myokines, such as IL-6, irisin, IGF-1, FGF2, beside the direct effect of loading. Importantly, exercise-induced myokine can exert an anti-inflammatory action that is able to counteract not only acute inflammation due to an infection, but also a condition of chronic low-grade inflammation raised as consequence of physical inactivity, aging or metabolic disorders (i.e., obesity, type 2 diabetes mellitus). In this review article, we will discuss the effects that some of the most studied exercise-induced myokines exert on bone formation and bone resorption, as well as a brief overview of the anti-inflammatory effects of myokines during the onset pathological conditions characterized by the development a systemic low-grade inflammation, such as sarcopenia, obesity and aging.

Fibroblast growth factor 9 (FGF9) inhibits myogenic differentiation of C2C12 and human muscle cells

Osteoporosis and sarcopenia (osteosarcopenia (OS)) are twin-aging diseases. The biochemical crosstalk between muscle and bone seems to play a role in OS. We have previously shown that osteocytes produce soluble factors with beneficial effects on muscle and vice versa. Recently, enhanced FGF9 production was observed in the OmGFP66 osteogenic cell line. To test its role in myogenic differentiation, C2C12 myoblasts were treated with recombinant FGF9. FGF9 as low as 10 ng/mL inhibited myogenic differentiation, suggesting that FGF9 might be a potential inhibitory factor produced from bone cells with effects on muscle cells. FGF9 (10–50 ng/mL) significantly decreased mRNA expression of MyoG and Mhc while increasing the expression of Myostatin. Consistent with the phenotype, RT-qPCR array revealed that FGF9 (10 ng/mL) increased the expression of Icam1 while decreased the expression of Wnt1 and Wnt6 decreased, respectively. FGF9 decreased caffeine-induced Ca²⁺ release from the sarcoplasmic reticulum (SR) of C2C12 myotubes and reduced the expression of genes (i.e. Cacna1s, RyR2, Naftc3) directly associated with intracellular Ca²⁺ homeostasis. Myogenic differentiation in human skeletal muscle cells was similarly inhibited by FGF9 but required higher doses of 200 ng/mL FGF9. FGF9 was also shown to stimulate C2C12 myoblast proliferation. FGF2 and the FGF9 subfamily members FGF16 and FGF20 also inhibited C2C12 myoblast differentiation and enhanced proliferation. Intriguingly, the differentiation inhibition was independent of proliferation enhancement. These findings suggest that FGF9 may modulate myogenesis via a complex signaling mechanism.

Osteosarcopenia: A case of geroscience

Many older persons lose their mobility and independence due to multiple diseases occurring simultaneously. Geroscience is aimed at developing innovative approaches to better identify relationships among the biological processes of aging. Osteoporosis and sarcopenia are two of the most prevalent chronic diseases in older people, with both conditions sharing overlapping risk factors and pathogenesis. When occurring together, these diseases form a geriatric syndrome termed "osteosarcopenia," which increases the risk of frailty, hospitalizations, and death. Findings from basic and clinical sciences aiming to understand osteosarcopenia have provided evidence of this syndrome as a case of geroscience. Genetic, endocrine, and mechanical stimuli, in addition to fat infiltration, sedentarism, and nutritional deficiencies, affect muscle and bone homeostasis to characterize this syndrome. However, research is in its infancy regarding accurate diagnostic markers and effective treatments with dual effects on muscle and bone. To date, resistance exercise remains the most promising strategy to increase muscle and bone mass, while sufficient quantities of protein, vitamin D, calcium, and creatine may preserve these tissues with aging. More recent findings, from rodent models, suggest treating ectopic fat in muscle and bone marrow as a possible avenue to curb osteosarcopenia, although this needs testing in human clinical trials.

Statistical Models to Assess Leg Muscle Mass in Ambulatory Children With Spastic Cerebral Palsy Using Dual-Energy X-Ray Absorptiometry

Cerebral palsy (CP) is a movement disorder associated with small and weak muscles. Methods that accurately assess muscle mass in children with CP are scarce. The purpose of this study was to determine whether dual-energy X-ray absorptiometry (DXA) accurately estimates midleg muscle mass in ambulatory children with spastic CP. Ambulatory children with spastic CP and typically developing children 5-11 y were studied (n = 15/group). Fat-free soft tissue mass (FFST) and fat mass at the middle third of the tibia (i.e., midleg) were estimated using DXA. Muscle mass (muscle_MRI) and muscle mass corrected for intramuscular fat (muscle_MRIfc) in the midleg were estimated using magnetic resonance imaging (MRI). Statistical models were created to predict muscle_MRI and muscle_MRIfc using DXA. Children with CP compared to typically developing children had lower FFST (38%), muscle_MRI (40%) and muscle_MRIfc (47%) (all p < 0.05) and a lower ratio of muscle_MRIfc to FFST (17%, p < 0.05). DXA-based models developed using data from typically developing children overestimated muscle_MRI (13%) and muscle_MRIfc (22%) (both p < 0.05) in children with CP. DXA-based models developed using data from children with CP explained 91% of the variance in muscle_MRI and 90% of the variance in muscle_MRIfc in children with CP (both p < 0.05). Moreover, the estimates were not different from muscle_MRI and muscle_MRIfc (both p > 0.99). We conclude that DXA-based statistical models accurately estimate midleg muscle mass in children with CP when the models are composed using data from children with CP rather than typically developing children.

Identification of a single-nucleotide polymorphism within CDH2 gene associated with bone morbidity in childhood acute lymphoblastic leukemia survivors

Aim: To identify genetic markers associated with late treatment-related skeletal morbidity in survivors of childhood acute lymphoblastic leukemia (ALL). Patients & methods: To this end, we measured the association between reduction in bone mineral density or vertebral fractures prevalence and variants from 1039 genes derived through whole exome sequencing in 242 childhood ALL survivors. Top-ranking variants were confirmed through genotyping, and further explored with stratified analyses and multivariable models. Results: The minor allele of rs1944294 in CDH2 gene was associated with bone geometrical parameter, trabecular cross-sectional area (p = 0.001). The association was modulated by radiation therapy (p = 0.001) and post-treatment time (p = 0.0002). Conclusion: The variant in CDH2 gene is a potential novel risk factor of bone morbidity in survivors of childhood ALL.

Osteosarcopenic Obesity: Current Knowledge, Revised Identification Criteria and Treatment Principles

Osteosarcopenic obesity (OSO) syndrome describes the simultaneous deterioration of bone, muscle and excess fat, resulting in reduced functionality and systemic metabolic dysregulation. The key component contributing to this may be ectopic fat in the viscera, bone and muscle. OSO research to date is summarized, and the revised criteria for its identification for research purposes are reviewed and proposed, including new criteria to assess visceral fat in males and females. Finally, nutritional and physical activity recommendations are consolidated into a treatment algorithm, which can be validated in future studies and which may also be applied to preventative management.

Body compositions differently contribute to BMD in different age and gender: a pilot study by QCT

The study was to investigate the correlation between body compositions and bone mineral density (BMD) and to evaluate the body composition contribution to BMD. In male, LM showed positive effect on BMD. In female, SAT showed positive, and FM and F/L showed negative effect on BMD.

PURPOSE

The purpose of the study was to investigate the correlation between body compositions and bone mineral density (BMD) performed by quantitative computed tomography (QCT), and to evaluate the body composition contribution to BMD.

METHODS

Three hundred ninety-four participants, including 122 male (31%) and 272 female (69%), were divided into groups by gender, age, and BMD. BMD and body compositions [including fat mass (FM), lean mass (LM), bone mass/lean mass ratio (B/L), fat mass/lean mass ratio (F/L), total adipose tissue (TAT), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT)] were retrospectively compared among groups using one-way ANOVA or t test. A stepwise multivariate analysis was used to evaluate the body composition contribution to BMD and produced models.

RESULTS

In male, BMD got decreased with age (P < 0.05). LM increased before 30-49 years, then decreased (P < 0.05). TAT and SAT decreased with age (P < 0.05). LM in OP group was lower than those in the other two groups (P < 0.05). Through stepwise multivariate analysis, LM firstly got into model 1 (M1, β = 0.589). In female, BMD, LM TAT, and VAT were increased before 30-49 years, then decreased (P < 0.05). FM and F/L increased with age (P < 0.05). SAT decreased with age (P < 0.05). FM and F/L in OP group were higher than those in other groups. LM, B/L, TAT, and SAT in the OP group were lower than those in the other groups (P < 0.05). SAT entered the M1 with a maximum β value (β = 0.584).

CONCLUSIONS

BMD and body compositions displayed different characteristics with age. In male, LM showed positive effect on BMD. In female, SAT showed positive, and FM and F/L showed negative effect on BMD.

Body fat has stronger associations with bone mass density than body mass index in metabolically healthy obesity

Objective

The effect of obesity-induced metabolic abnormalities on bone mineral density (BMD) and osteoporosis are well established. However, the association between metabolically healthy obesity (MHO) and BMD remains unclear. Our aim was to investigate whether different obesity phenotypes in MHO were associated with BMD in a cross-sectional study.

Methods

All eligible adults receiving a health examination at the Tri-Service General Hospital from 2010 to 2016 were included. They were categorized based on body mass index (BMI) or percentage body fat (PBF). The associations between BMI or PBF and BMD were analyzed by adjusting for pertinent covariables.

Results

Males with normal weight and overweight and females with underweight and normal weight were associated with reduced BMD (β = 0.221, 95%CI = -0.354, -0.088; β = -0.155, 95%CI = -0.286, -0.023) (β = -0.736, 95%CI = -1.043, 0.429; β = -0.340, 95%CI = -0.567, -0.112), respectively. Females in Q1 had close to significant associations with reduced BMD (β = -0.253, 95%CI = -0.465, -0.041). Normal weight, overweight, Q2, and Q3 had stronger prediction of low BMD with ORs of 0.402 (95%CI = 0.204–0.791), 0.539 (95%CI = 0.321–0.905), 0.694 (95%CI = 0.490–0.982), and 0.466 (95%CI = 0.342–0.636), respectively. The relationship remained significant in male population that PBF was associated with reduced BMD with ORs of 0.435 (95%CI = 0.203, 0.935), 0.494 (95%CI = 0.247, 0.991), 0.268 (95%CI = 0.120, 0.597) in Q1, Q2, Q3 respectively.

Conclusion

Increased PBF had a significant association with low BMD in the MHO population. Obesity defined by PBF might be a useful indicator for low BMD. The association between body fat and bone health deserves further investigation regarding the potential pathophysiological mechanisms.

Diagnostic imaging of two related chronic diseases: Sarcopenia and Osteoporosis

Sarcopenia and osteoporosis are two major health problems worldwide, responsible for a serious clinical and financial burden due to the increasing life expectancy. Both when presented as a single entity and, in particular, in the form of “osteosarcopenia”, they lead to an important increased risk of falls, fractures, hospitalization and mortality. In dealing with these two pathological conditions, it is important to understand that between bone and muscle there is not only a functional correlation but also a close relationship in the development and in maintenance, which is well expressed by the concept of “bone-muscle unit”. This close relationship agrees with the existence of a linear association between sarcopenia and osteoporosis, in particular in elderly population. It is mandatory, in the clinical assessment of both diseases, to do an early diagnosis or to delay as far as possible the appearance of an established form in order to prevent the onset of complications. The aim of this review is to present the different imaging modalities available for a non-invasive investigation of bone and muscle mass and quality in osteoporosis and sarcopenia, with their application and limitations.

Effect of Strontium Ranelate on the Muscle and Vertebrae of Ovariectomized Rats

Osteoporosis is often accompanied by sarcopenia. The effect of strontium ranelate (SR) on muscle tissue has not been investigated sufficiently. In this study, the effect of different SR treatments on muscle was studied. Additionally, the lumbar vertebrae were analyzed. Three-month-old female rats were divided into five groups (n = 12): Group 1: untreated (NON-OVX); Group 2: ovariectomized and left untreated (OVX); Group 3: SR after OVX until the study ended (13 weeks, SR prophylaxis and therapy = pr+th); Group 4: OVX and SR for 8 weeks (SR prophylaxis = pr); Group 5: SR for 5 weeks from the 8 week after OVX (SR therapy = SR th). SR was applied in food (630 mg/kg body weight). The size of muscle fibers, capillary density, metabolic enzymes, and mRNA expression were assessed in soleus, gastrocnemius, and longissimus muscles. The vertebral bodies underwent micro-CT, biomechanical, and ashing analyses. In general, SR did not alter the muscle histological parameters. The changes in fiber size and capillary ratio were related to the body weight. Myostatin mRNA was decreased in Sr pr+th; protein expression was not changed. SR th led to increase in mRNA expression of vascular endothelial growth factor (Vegf-B). In lumbar spine, SR pr+th enhanced biomechanical properties, bone mineral density, trabecular area, density, and thickness and cortical density. The reduced calcium/phosphate ratio in the SR pr+th group indicates the replacement of calcium by strontium ions. SR has no adverse effects on muscle tissue and it shows a favorable time-dependent effect on vertebrae. A functional analysis of muscles could verify these findings.

Activation of AKT-mTOR Signaling Directs Tenogenesis of Mesenchymal Stem Cells

Tendon repair is a clinical challenge because of the limited understanding on tenogenesis. The synthesis of type I collagen (Collagen I) and other extracellular matrix are essential for tendon differentiation and homeostasis. Current studies on tenogenesis focused mostly on the tenogenic transcriptional factors while the signaling controlling tenogenesis on translational level remains largely unknown. Here, we showed that mechanistic target of rapamycin (mTOR) signaling was activated by protenogenic growth factor, transforming growth factors beta1, and insulin-like growth factor-I. The expression of mTOR was upregulated during tenogenesis of mesenchymal stem cells (MSCs). Moreover, mTOR was downregulated in human tendinopathy tissues and was inactivated upon statin treatment. Both inhibition and depletion of AKT or mTOR significantly reduced type I collagen production and impaired tenogenesis of MSCs. Tendon specific-ablation of mTOR resulted in tendon defect and reduction of Collagen I. However, there is no evident downregulation of tendon associated collagens at the transcription level. Our study demonstrated that AKT-mTOR axis is a key mediator of tendon differentiation and provided a novel therapeutic target for tendinopathy and tendon injuries. Stem Cells 2018;36:527-539.

Relative abundance of mature myostatin rather than total myostatin is negatively associated with bone mineral density in Chinese

Myostatin is mainly secreted by skeletal muscle and negatively regulates skeletal muscle growth. However, the roles of myostatin on bone metabolism are still largely unknown. Here, we recruited two large populations containing 6308 elderly Chinese and conducted comprehensive statistical analyses to evaluate the associations among lean body mass (LBM), plasma myostatin, and bone mineral density (BMD). Our data revealed that total myostatin in plasma was mainly determined by LBM. The relative abundance of mature myostatin (mature/total) was significantly lower in high versus low BMD subjects. Moreover, the relative abundance of mature myostatin was positively correlated with bone resorption marker. Finally, we carried out in vitro experiments and found that myostatin has inhibitory effects on the proliferation and differentiation of human osteoprogenitor cells. Taken together, our results have demonstrated that the relative abundance of mature myostatin in plasma is negatively associated with BMD, and the underlying functional mechanism for the association is most likely through inhibiting osteoblastogenesis and promoting osteoclastogenesis.

Crosstalk between MLO-Y4 osteocytes and C2C12 muscle cells is mediated by the Wnt/β-catenin pathway

We examined the effects of osteocyte secreted factors on myogenesis and muscle function. MLO-Y4 osteocyte-like cell conditioned media (CM) (10%) increased ex vivo soleus muscle contractile force by ~25%. MLO-Y4 and primary osteocyte CM (1-10%) stimulated myogenic differentiation of C2C12 myoblasts, but 10% osteoblast CMs did not enhance C2C12 cell differentiation. Since WNT3a and WNT1 are secreted by osteocytes, and the expression level of Wnt3a is increased in MLO-Y4 cells by fluid flow shear stress, both were compared, showing WNT3a more potent than WNT1 in inducing myogenesis. Treatment of C2C12 myoblasts with WNT3a at concentrations as low as 0.5ng/mL mirrored the effects of both primary osteocyte and MLO-Y4 CM by inducing nuclear translocation of β-catenin with myogenic differentiation, suggesting that Wnts might be potential factors secreted by osteocytes that signal to muscle cells. Knocking down Wnt3a in MLO-Y4 osteocytes inhibited the effect of CM on C2C12 myogenic differentiation. Sclerostin (100ng/mL) inhibited both the effects of MLO-Y4 CM and WNT3a on C2C12 cell differentiation. RT-PCR array results supported the activation of the Wnt/β-catenin pathway by MLO-Y4 CM and WNT3a. These results were confirmed by qPCR showing up-regulation of myogenic markers and two Wnt/β-catenin downstream genes, Numb and Flh1. We postulated that MLO-Y4 CM/WNT3a could modulate intracellular calcium homeostasis as the trigger mechanism for the enhanced myogenesis and contractile force. MLO-Y4 CM and WNT3a increased caffeine-induced Ca²⁺ release from the sarcoplasmic reticulum (SR) of C2C12 myotubes and the expression of genes directly associated with intracellular Ca²⁺ signaling and homeostasis. Together, these data show that in vitro and ex vivo, osteocytes can stimulate myogenesis and enhance muscle contractile function and suggest that Wnts could be mediators of bone to muscle signaling, likely via modulation of intracellular Ca²⁺ signaling and the Wnt/β-Catenin pathway.

Relationship between obesity, sarcopenia, sarcopenic obesity, and bone mineral density in elderly subjects aged 80 years and over

Objective

This study sought to analyze the relationship between the components and aggravations of body composition (obesity, sarcopenia, and sarcopenic obesity) and bone mineral density in elderly subjects aged ≥80 years.

Methods

A cross-sectional study design was utilized to assess 128 subjects aged between 80 and 95 years. Body composition and bone mineral density were measured by dual energy X-ray absorptiometry. Gait speed was assessment by walking test. The statistical analyses included Spearman's correlation, one-way analysis of variance, the chi-squared test, and binary logistic regression analysis.

Results

The elderly subjects with sarcopenia had lower bone mineral density compared to the obesity group, with higher risk for presence of osteopenia/osteoporosis in the spine (OR: 2.81; CI: 1.11-7.11) and femur (OR: 2.75; CI: 1.02-7.44). Obesity was shown to be a protective factor for osteopenia/osteoporosis in the spine (OR: 0.43; CI: 0.20-0.93) and femur (OR: 0.27; CI: 0.12-0.62).

Conclusion

It was found that lean mass is more directly related to bone mineral density (total, femur, and spine) and sarcopenia is associated with osteopenia/osteoporosis. Obesity represents a possible protective factor for osteopenia/osteoporosis in elderly subjects aged 80 years and over.