Muscle-bone interactions: basic and clinical aspects

Changes in Bone Mineral Density in Patients With Non-dialysis-Dependent Chronic Kidney Disease Are Associated With Body Composition

OBJECTIVE

Chronic kidney disease (CKD) and low bone mineral density (BMD) are highly prevalent and can co-exist. Parameters of mineral metabolism are associated with BMD in CKD, but other contributing factors may contribute. The aim of this study was to assess changes in BMD and its determinants in patients with nondialysis-dependent CKD (NDD-CKD).

METHODS

Body composition and biochemical profiles were assessed in a retrospective hospital-based cohort study of patients with NDD-CKD. BMD, lean soft tissue (LST), appendicular LST (ALST), and percentage fat mass were assessed by dual-energy X-ray absorptiometry. The ALST index (ALSTI, ALST/height2) and load-capacity index (LCI, fat mass/LST) were calculated. Low BMD was defined as T-score ≤ -1.0.

RESULTS

The mean time between assessments was 2.8 ± 1.3 years; 46 patients were included. A reduction in renal function was observed. Changes in body composition included reductions in ALST (P = .031), ALSTI (P = .021), a trend for BMD (P = .053), and an increase in percentage fat mass (P = .044) and LCI (P = .032). Females had a reduction in BMD (P = .034), ALST (P = .026), and ALSTI (P = .037). Patients with low BMD at baseline had lower LST (P = .013), ALST (P = .023), and percentage fat mass (P = .037) than those with normal BMD. Additionally, reductions in LST (P = .041), ALST (P = .006), and ALSTI (P = .008) were observed in patients who had low BMD at baseline, while no significant changes in body composition were observed in those with normal BMD at baseline. The following body composition parameters at baseline were determinants of BMD status at follow-up: LST (odds ratio [OR]: 0.899, 95% confidence interval [CI]: 0.829-0.976, P = .010), ALST (OR: 0.825, 95% CI: 0.704-0.967, P = .017), and ALSTI (OR: 0.586, 95% CI: 0.354-0.968, P = .037), independent of fat mass and LCI.

CONCLUSIONS

Detrimental body composition changes were observed without changes in body weight; these were more significant in females. Moreover, this is the first longitudinal study showing a protective effect of LST against BMD loss in patients with NDD-CKD.

Spikebot: A Multigait Tensegrity Robot with Linearly Extending Struts

Numerous recent research efforts have leveraged networks of rigid struts and flexible cables, called tensegrity structures, to create highly resilient and packable mobile robots. However, the locomotion of existing tensegrity robots is limited in terms of both speed and number of distinct locomotion modes, restricting the environments that a robot is capable of exploring. In this study, we present a tensegrity robot inspired by the volumetric expansion of Tetraodontidae. The robot, referred to herein as Spikebot, employs pneumatically actuated rigid struts to expand its global structure and produce diverse gaits. Spikebot is composed of linear actuators that dually serve as rigid struts linked by elastic cables for stability. The linearly actuating struts can selectively protrude to initiate thrust- and instability-driven locomotion primitives. Such motion primitives allow Spikebot to reliably locomote, achieving rolling, lifting, and jumping. To highlight Spikebot's potential for robotic exploration, we demonstrate how it achieves multi-dimensional locomotion over varied terrestrial conditions.

Dynamic Muscle Function Parameters in Indian Children and Adolescents with Type 1 Diabetes Mellitus: A Case-Control Study

Introduction

Recent evidence reveals that type 1 diabetes mellitus (T1DM) impairs muscle function (MF) in adolescents. However, despite its importance in physical well-being, data on dynamic MF in Indian children and adolescents (C and Y) with T1DM are scarce. We assessed MF using Jumping Mechanography (JM, a measurement method for motion analysis and assessment of muscle power and force). (1) To assess dynamic MF by JM in C and Y with T1DM as compared to healthy controls (2) To determine predictors of MF in children with T1DM.

Methods

A cross-sectional observational study on 266 children (133 - T1DM duration >1 year with no known comorbidities + 133 age and gender-matched healthy controls) aged 6-19 years. Anthropometry, body composition, and MF (maximum relative power Pmax/mass, maximum relative force Fmax/BW by JM) were recorded. The lean mass index (LMI) was calculated as lean mass (kg)/height (m2). HbA1c was assessed in T1DM. Independent sample t-test and linear regression were performed.

Results

MF parameters (Pmax/mass 33.5 ± 7.2 vs 38.0 ± 8.6 W/kg and Fmax/BW 10.5 ± 2.9 vs 11.4 ± 4.1 N/kg, P < 0.05) were significantly lower in T1DM group vs controls. Positive association of body mass index and LMI with both MF parameters and negative association of insulin requirement and HbA1c with Fmax was observed in T1DM. Predictors of MF identified were MMI (Pmax/mass:b = 1.6,95%CI = 0.6-2.6; Fmax/BW:b =2.0,95%CI = 1.6-2.4) and HbA1c (Pmax/mass:b = -2.1,95%CI = -4.5--0.5; Fmax/BW:b = -1.1,95%CI = -2.0--0.2) (P < 0.05).

Conclusion

C and Y with T1DM exhibits compromised muscle function. Poor glycaemic control increases the risk of having decreased MF, irrespective of diabetes duration and may contribute to sarcopenia in adulthood.

The critical impact of traumatic muscle loss on fracture healing: Basic science and clinical aspects

Musculoskeletal trauma, specifically fractures, is a leading cause of patient morbidity and disability worldwide. In approximately 20% of cases with fracture and related traumatic muscle loss, bone healing is impaired leading to fracture nonunion. Over the past few years, several studies have demonstrated that bone and the surrounding muscle tissue interact not only anatomically and mechanically but also through biochemical pathways and mediators. Severe damage to the surrounding musculature at the fracture site causes an insufficiency in muscle-derived osteoprogenitor cells that are crucial for fracture healing. As an endocrine tissue, skeletal muscle produces many myokines that act on different bone cells, such as osteoblasts, osteoclasts, osteocytes, and mesenchymal stem cells. Investigating how muscle influences fracture healing at cellular, molecular, and hormonal levels provides translational therapeutic solutions to this clinical challenge. This review provides an overview about the contributions of surrounding muscle tissue in directing fracture healing. The focus of the review is on describing the interactions between bone and muscle in both healthy and fractured environments. We discuss current progress in identifying the bone-muscle molecular pathways and strategies to harness these pathways as cues for accelerating fracture healing. In addition, we review the existing challenges and research opportunities in the field.

High-Protein Diets during either Resistance or Concurrent Training Have No Detrimental Effect on Bone Parameters in Resistance-Trained Males

BACKGROUND

The effects of combining resistance training (RT) and concurrent training (CT; resistance + endurance training) with varied protein doses on bone measures remain poorly understood. Hence, we conducted a comparison of the impacts of two high-protein diets (1.6 or 3.2 g kg-1 d-1) over 16 weeks in resistance-trained males, either with CT or RT alone.

METHODS

A total of forty-eight males, all of whom were resistance-trained, had the following demographics: 26.6 ± 6 years, body mass index: 25.6 ± 2.9 kg m-2 administered either 3.2 g kg-1 d-1 protein (CT2; n = 12; RT2; n = 12) or 1.6 g kg-1 d-1 protein (CT1; n = 12; RT1; n = 12) during 16 weeks (four sessions·w-1). Bone parameters were assessed pre- and post-intervention.

RESULTS

There was no significant interaction between the intervention group and time for the legs, arms, ribs, or pelvis area BMC and BMD (p > 0.05). For the BMD of the pelvis and the BMC of the right ribs, however, there were significant time effects noted (p < 0.05). Furthermore, there was a significant interaction between the intervention group and time in the lumbar and thoracic spines, with a particular time effect noted for the thoracic spine region (p < 0.05). The regional differences in skeletal responses to the intervention are highlighted by these data.

CONCLUSION

Our findings show that the intake of two high-protein diets combined with RT and CT during 16 weeks had no adverse effects on bone tissue parameters. While these findings indicate that protein intake between 2 and 3 times the current RDI does not promote bone demineralization when consumed in conjunction with exercise, future studies investigating the long-term effects of chronic high protein intake on bone tissue health are warranted.

The association between appendicular skeletal muscle index and bone mineral density in children and adolescents with chronic kidney disease: A cross-sectional study

Chronic kidney disease (CKD), a pervasive public health concern, can lead to complications like sarcopenia and reduced bone mineral density (BMD). However, it is still unclear exactly how muscle mass correlates with BMD in youngsters and adolescents with CKD. We aimed to investigate the association between appendicular skeletal muscle index (ASMI) and BMD among children and adolescents with CKD. In our research, we utilized data from the National Health and Nutrition Examination Survey (NHANES) collected between 2011 and 2014 to investigate the association of ASMI with BMD among this population. The association linking ASMI with total BMD was examined through multivariate linear regression models. Furthermore, fitted smoothing curves were employed, as well as generalized additive models. Our analysis finally included 503 CKD participants aged between 8 and 19 years. We found a significant association linking ASMI with total BMD among children and adolescents with CKD. The connection persisted even after accounting for covariates. Upon subgroup analysis, there was a statistically significant association of ASMI with total BMD for both males and females, as well as for Mexican-American and non-Hispanic White populations. However, no significant association was observed in other Hispanic, non-Hispanic Black, or populations of other races. We discovered a positive correlation linking the ASMI and the total BMD in children and teenagers with CKD. In CKD patients, maintaining skeletal muscle mass may be crucial for managing and preventing renal osteodystrophy.

A novel non-invasive method for predicting bone mineral density and fracture risk using demographic and anthropometric measures

Fractures are costly to treat and can significantly increase morbidity. Although dual-energy x-ray absorptiometry (DEXA) is used to screen at risk people with low bone mineral density (BMD), not all areas have access to one. We sought to create a readily accessible, inexpensive, high-throughput prediction tool for BMD that may identify people at risk of fracture for further evaluation. Anthropometric and demographic data were collected from 492 volunteers (♂275, ♀217; [44 ​± ​20] years; Body Mass Index (BMI) = [27.6 ​± ​6.0] kg/m2) in addition to total body bone mineral content (BMC, kg) and BMD measurements of the spine, pelvis, arms, legs and total body. Multiple-linear-regression with step-wise removal was used to develop a two-step prediction model for BMC followed by BMC. Model selection was determined by the highest adjusted R2, lowest error of estimate, and lowest level of variance inflation (α ​= ​0.05). Height (HTcm), age (years), sexm=1, f=0, %body fat (%fat), fat free mass (FFMkg), fat mass (FMkg), leg length (LLcm), shoulder width (SHWDTHcm), trunk length (TRNKLcm), and pelvis width (PWDTHcm) were observed to be significant predictors in the following two-step model (p ​< ​0.05). Step1: BMC (kg) = (0.006 3 × HT) ​+ ​(-0.002 4 × AGE) ​+ ​(0.171 2 × SEXm=1, f=0) ​+ ​(0.031 4 × FFM) ​+ ​(0.001 × FM) ​+ ​(0.008 9 × SHWDTH) ​+ ​(-0.014 5 × TRNKL) ​+ ​(-0.027 8 × PWDTH) - 0.507 3; R2 ​= ​0.819, SE ​± ​0.301. Step2: Total body BMD (g/cm2) = (-0.002 8 × HT) ​+ ​(-0.043 7 × SEXm=1, f=0) ​+ ​(0.000 8 × %FAT) ​+ ​(0.297 0 × BMC) ​+ ​(-0.002 3 × LL) ​+ ​(0.002 3 × SHWDTH) ​+ ​(-0.002 5 × TRNKL) ​+ ​(-0.011 3 × PWDTH) ​+ ​1.379; R2 ​= ​0.89, SE ​± ​0.054. Similar models were also developed to predict leg, arm, spine, and pelvis BMD (R2 ​= ​0.796-0.864, p ​< ​0.05). The equations developed here represent promising tools for identifying individuals with low BMD at risk of fracture who would benefit from further evaluation, especially in the resource or time restricted setting.

Role of Body Composition in the Prediction of Skeletal Fragility Induced by Hormone Deprivation Therapies in Cancer Patients

PURPOSE OF REVIEW

This review paper is intended to show that changes in body composition are key in the pathogenesis of bone fragility amongst patients with breast and prostate cancer receiving hormone deprivation therapies (HDTs) and that the mechanism is based on the development of alterations in bone quality rather than in bone quantity.

RECENT FINDINGS

Preclinical and clinical data suggest a tight connection amongst bone, adipose and muscular tissues by means of several soluble mediators, potentially leading to (1) bone resorption and bone quality deterioration in sarcopenic obese subjects, (2) bone mineral deposition in healthy trained subjects. Cancer patients treated with HDTs frequently fall into the first condition, named osteosarcopenic obesity. Current clinical guidelines for the prevention of treatment-induced osteoporosis focus on bone mineral density (BMD) as a main predictive factor for fracture risk; however, the pathophysiology underlying HDT-induced bone fragility differs from that of primary and postmenopausal osteoporosis, suggesting a prevalent role for bone quality alterations. Focusing on available data from clinical trials, in our review we suggest osteosarcopenic obesity as a common target for the prevention and treatment of HDTs-related metabolic and skeletal complications, beyond a BMD-centred approach.

Effects of blood flow restriction training on bone turnover markers, microstructure, and biomechanics in rats

Objective

The present study aimed to investigate the effects of blood flow restriction training on muscle strength, bone tissue structure material, and biomechanical properties in rats applying various exercise interventions and to analyze the process by identifying the bone turnover markers, it provides a theoretical basis for the application of BFRT in clinical rehabilitation.

Methods

A total of 24, 3-month-old male SD (Sprague Dawley) rats were randomly divided into pressurized control group (CON, n=6), low-intensity training group (LIRT, n=6), high-intensity training group (HIRT, n=6), and blood flow restriction training group (LIBFR, n=6) for 8-week ladder-climbing exercises. The pressured control group were given only ischemia treatments and did not undertake any burden. The low-intensity training group was allowed to climb the ladder with 30% of the maximum voluntary carrying capacity (MVCC). The rats in the high-intensity training group were allowed to climb the ladder with 70% MVCC. The blood flow restriction training group climbed the ladder with 30% MVCC while imposing blood flow restriction. Before sampling, the final MVCC was measured using a ladder-climbing protocol with progressively increasing weight loading. The serum, muscle, and bone were removed for sampling. The concentrations of the bone turnover markers PINP, BGP, and CTX in the serum were measured using ELISA. The bone mineral density and microstructure of femur bones were measured using micro-CT. Three-point bending and torsion tests were performed by a universal testing machine to measure the material mechanics and structural mechanics indexes of the femur bone.

Results

The results of maximum strength test showed that the MVCC in LIRT, HIRT, and LIBFR groups was significantly greater than in the CON group, while the MVCC in the HIRT group was significantly higher than that in the LIRT group (P<0.05). According to the results of the bone turnover marker test, the concentrations of bone formation indexes PINP (amino-terminal extension peptide of type I procollagen) and BGP (bone gla protein) were significantly lower in the CON group than in the HIRT group (P<0.01), while those were significantly higher in the LIRT group compared to the HIRT group (P<0.01). In terms of bone resorption indexes, significant differences were identified only between the HIRT and other groups (P<0.05). The micro-CT examination revealed that the HIRT group had significantly greater bone density index values than the CON and LIRT groups (P<0.05). The results of three-point bending and torsion test by the universal material testing machine showed that the elastic modulus and maximum load indexes of the HIRT group were significantly smaller than those of the LIBFR group (P<0.05). The fracture load indexes in the HIRT group were significantly smaller than in the LIBFR group (P<0.05).

Conclusion

1. LIRT, HIRT, LIBFR, and CON all have significant differences, and this training helps to improve maximum strength, with HIRT being the most effective. 2. Blood flow restriction training can improve the expression of bone turnover markers, such as PINP and BGP, which promote bone tissue formation. 3. Blood flow restriction training can improve muscle strength and increase the positive development of bone turnover markers, thereby improving bone biomechanical properties such as bone elastic modulus and maximum load.

Evaluation of mandibular trabecular and cortical bone by fractal analysis and radiomorphometric indices in bruxist and non-bruxist patients

BACKGROUND

The aim of this study was to evaluate the effect of bruxism on the cortical and trabecular bone of the mandible using the radiomorphometric indexes and fractal analysis (FA) additionally to examine the efficiency of FA as diagnostic test for bruxism.

METHODS

Evaluation was performed on panoramic radiographs of 94 bruxists and 94 non-bruxist individuals with the ImageJ program. Cortical bone was assessed with mandibular cortical index, mental index, and panoramic mental index. Trabecular bone in the condyle, gonial, and corpus region was evaluated by FA. An independent sample t and Mann-Whitney-U tests and Pearson and Spearman rank correlations were conducted for statistical analysis.

RESULTS

A total of 188 participants, 112 female, and 76 male, were included in the study. The sample age ranged from 18 to 43, with a mean of 27.55 (± 7.022) years. FA values of the angulus were significantly higher than those of the condyle and corpus, and the mean of the sample for the angulus, condyle, and corpus, respectively, were; 1.36 (± 10), 1.10 (± 0.9), 1.13 (± 0.8). There was a positive correlation between FA of the mandibular corpus and age (r = .163, p = .025). Females' values were smaller than males' in the FAs of three regions, and significant differences were found in FA of the condyle and angulus of the mandible, MCI, and PMI according to gender. There was no statistically significant difference between bruxist and non-bruxist patients in term of FAs of three regions, MCI, MI, and PMI values (p > .05).

CONCLUSIONS

FA of the condyle and angulus of the mandible, MCI, and PMI are significantly affected by gender. However bruxism doesn't cause a significant change in the fractal dimensions of the bone in the mandible and doesn't change substantially MCI, MI, and PMI.

Osteosarcopenia in the Spine Beyond Bone Mineral Density: Association Between Paraspinal Muscle Impairment and Advanced Glycation Endproducts

STUDY DESIGN

Prospective cross-sectional study.

OBJECTIVE

To determine if an accumulation of advanced glycation endproducts (AGEs) is associated with impaired paraspinal muscle composition.

BACKGROUND

Impaired bone integrity and muscle function are described as osteosarcopenia. Osteosarcopenia is associated with falls, fragility fractures, and reduced quality of life. Bone integrity is influenced by bone quantity (bone mineral density) and quality (microarchitecture and collagen). The accumulation of AGEs stiffens collagen fibers and increases bone fragility. The relationship between paraspinal muscle composition and bone collagen properties has not been evaluated.

METHODS

Intraoperative bone biopsies from the posterior superior iliac spine were obtained and evaluated with multiphoton microscopy for fluorescent AGE cross-link density (fAGEs). Preoperative magnetic resonance imaging measurements at level L4 included the musculus (m.) psoas and combined m. multifidus and m. erector spinae (posterior paraspinal musculature, PPM). Muscle segmentation on axial images (cross-sectional area, CSA) and calculation of a pixel intensity threshold method to differentiate muscle (functional cross-sectional area, fCSA) and intramuscular fat (FAT). Quantitative computed tomography was performed at the lumbar spine. Univariate and multivariable regression models were used to investigate associations between fAGEs and paraspinal musculature.

RESULTS

One hundred seven prospectively enrolled patients (50.5% female, age 60.7 y, BMI 28.9 kg/m 2 ) were analyzed. In all, 41.1% and 15.0% of the patients demonstrated osteopenia and osteoporosis, respectively. Univariate linear regression analysis demonstrated a significant association between cortical fAGEs and CSA in the psoas (ρ=0.220, P =0.039) but not in the PPM. Trabecular fAGEs revealed no significant associations to PPM or psoas musculature. In the multivariable analysis, higher cortical fAGEs were associated with increased FAT (β=1.556; P =0.002) and CSA (β=1.305; P =0.005) in the PPM after adjusting for covariates.

CONCLUSION

This is the first investigation demonstrating that an accumulation of nonenzymatic collagen cross-linking product fAGEs in cortical bone is associated with increased intramuscular fat in the lumbar paraspinal musculature.

Relationship between bruxism and mandibular bone modifications based on medical imaging: a scoping review

OBJECTIVES

This scoping review aimed to assess the current state of knowledge regarding the relationship between bruxism and changes in density or volume of mandibular bone, based on medical imaging.

METHODS

Literature review was conducted following the PRISMA-ScR protocol. PubMed, Web of Science and Cochrane library databases were searched for peer-reviewed articles by two blinded reviewers. Studies based on the evaluation of mandibular bone density and/or bone volume with imaging examination in adult patients were examined. The selected articles were summarized in PICOS tables and assessed for methodological quality.

RESULTS

Nine articles were included, according to the inclusion criteria. They showed that bruxer patients had more bony exostoses of the mandibular angle, smaller condyles, and morphological changes for cancellous and cortical mandibular bone compared to non-bruxer patients.

CONCLUSION

Bruxism seems to induce morphological and anatomical changes in the different regions of the mandibular bone (condyles, mandibular angle, mandible body). Given the heterogeneity of the included studies, these results should be interpreted with caution. Further studies are needed to support these results, in particular via the analysis of three-dimensional imaging to overcome the limitations of panoramic radiograph.

Morphological evaluation of gonial and antegonial regions in bruxers on panoramic radiographic images

BACKGROUND

This is the first study to report both cortical and trabecular bone evaluation of mandibles in bruxers, within the knowledge of the authors. The purpose of this study was to evaluate the effects of bruxism on both the cortical and the trabecular bone in antegonial and gonial regions of the mandible, which is the attachment of the masticatory muscles, by using panoramic radiographic images.

METHODS

In this study, the data of 65 bruxer (31 female, 34 male) and 71 non-bruxer (37 female, 34 male) young adult patients (20-30 years) were evaluated. Antegonial Notch Depth (AND), Antegonial-Index (AI), Gonial-Index, Fractal Dimension (FD) and Bone Peaks (BP) were evaluated on panoramic radiographic images. The effects of the bruxism, gender and side factors were investigated according to these findings. The statistical significance level was set atP ≤ 0.05.

RESULTS

The mean AND of bruxers (2.03 ± 0.91) was significantly higher than non-bruxers (1.57 ± 0.71; P < 0.001). The mean AND of males was significantly higher than females on both sides (P < 0.05). The mean AI of bruxers (2.95 ± 0.50) was significantly higher than non-bruxers (2.77 ± 0.43; P = 0.019). The mean FD on each side was significantly lower in bruxers than in non-bruxers (P < 0.05). The mean FD of males (1.39 ± 0.06) was significantly higher than females (1.37 ± 0.06; P = 0.049). BP were observed in 72.5% of bruxers and 27.5% of non-bruxers. The probability of existing BP, in bruxers was approximately 3.4 times higher than in non-bruxers (P = 0.003), in males was approximately 5.5 times higher than in females (P < 0.001).

CONCLUSION

According to the findings of this study, the morphological differences seen in cortical and trabecular bone in the antegonial and gonial regions of the mandible in bruxers can be emphasized as deeper AND, higher AI, increased of existing BPs, and lower FD, respectively. The appearance of these morphological changes on radiographs may be useful for indication and follow-up of bruxism. Gender is an effective factor on AND, existing BP and FD.

Zoledronic acid improves bone quality and muscle function in a high bone turnover state

SUMMARY

Zoledronic acid (ZA) prevents muscle weakness in mice with bone metastases; however, its role in muscle weakness in non-tumor-associated metabolic bone diseases and as an effective treatment modality for the prevention of muscle weakness associated with bone disorders, is unknown. We demonstrate the role of ZA-treatment on bone and muscle using a mouse model of accelerated bone remodeling, which represents the clinical manifestation of non-tumor associated metabolic bone disease. ZA increased bone mass and strength and rescued osteocyte lacunocanalicular organization. Short-term ZA treatment increased muscle mass, whereas prolonged, preventive treatment improved muscle mass and function. In these mice, muscle fiber-type shifted from oxidative to glycolytic and ZA restored normal muscle fiber distribution. By blocking TGFβ release from bone, ZA improved muscle function, promoted myoblast differentiation and stabilized Ryanodine Receptor-1 calcium channel. These data demonstrate the beneficial effects of ZA in maintaining bone health and preserving muscle mass and function in a model of metabolic bone disease.

Context and significance

TGFβ is a bone regulatory molecule which is stored in bone matrix, released during bone remodeling, and must be maintained at an optimal level for the good health of the bone. Excess TGFβ causes several bone disorders and skeletal muscle weakness. Reducing excess TGFβ release from bone using zoledronic acid in mice not only improved bone volume and strength but also increased muscle mass, and muscle function. Progressive muscle weakness coexists with bone disorders, decreasing quality of life and increasing morbidity and mortality. Currently, there is a critical need for treatments improving muscle mass and function in patients with debilitating weakness. Zoledronic acid's benefit extends beyond bone and could also be useful in treating muscle weakness associated with bone disorders.

Tridimensional assessment of the mandibular angle in patients with different skeletal patterns by cone-beam computed tomography scans: a retrospective study

BACKGROUND

Since the muscles of chewing are involved in the region of the mandibular angle, important structures in surgical and orthodontic procedures, to study its morphological aspects and the possible influence of different patterns of skeletal development would be of interest. Thus, this study aimed to assess the influence of patient characteristics - such as sex, skeletal malocclusion (Class I, Class II, and Class III) and facial type (brachycephalic, mesocephalic, and dolichocephalic) - on the width, height, thickness, and volume of the mandibular angle, using cone-beam computed tomography (CBCT) scans.

METHODS

CBCT scans were assessed - 144 men and 154 women, total of 298 - and classified according to skeletal patterns (skeletal malocclusions and facial types). Width, height, and thickness of the mandibular angle were measured using OnDemand 3D software. The volumetric measures of the mandibular angle were obtained using the ITK-SNAP software. Analysis of Variance (multiway ANOVA) with Tukey's post-hoc test compared the data, with a 5% significance level.

RESULTS

Among the factors studied, sex significantly influenced all the analyzed variables (height, width, thickness, and volume of the mandibular angle) (p < 0.05); in general, male individuals presented higher values than females. In some cases, the skeletal malocclusion and facial type factors influenced only the width and height variables (p < 0.05); in general, the Class III and dolichocephalic individuals presented higher values in relation to the other types of skeletal malocclusions and facial types.

CONCLUSIONS

Variations in the craniofacial growth pattern, considering the different skeletal malocclusions and facial types, had some influence in the width and height dimensions of the mandibular angle. Furthermore, sex influenced all the studied variables.

The association between paraspinal muscle parameters and vertebral pedicle microstructure in patients undergoing lumbar fusion surgery

PURPOSE

Lumbar fusion surgery has become a standard procedure in spine surgery and commonly includes the posterior placement of pedicle screws. Bone quality is a crucial factor that affects pedicle screw purchase. However, the relationship between paraspinal muscles and the bone quality of the pedicle is unknown. The aim of the study was to determine the relationship between paraspinal muscles and the ex vivo bony microstructure of the lumbar pedicle.

METHODS

Prospectively, collected data of patients undergoing posterior lumbar fusion for degenerative spinal conditions was analyzed. Pre-operative lumbar magnetic resonance imaging (MRI) scans were evaluated for a quantitative assessment of the cross-sectional area (CSA), functional cross-sectional area (fCSA), and the proportion of intramuscular fat (FI) for the psoas muscle and the posterior paraspinal muscles (PPM) at L4. Intra-operative bone biopsies of the lumbar pedicle were obtained and analyzed with microcomputed tomography (µCT) scans. The following cortical (Cort) and trabecular (Trab) bone parameters were assessed: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), connectivity density (CD), bone-specific surface (BS/BV), apparent density (AD), and tissue mineral density (TMD).

RESULTS

A total of 26 patients with a mean age of 59.1 years and a mean BMI of 29.8 kg/m2 were analyzed. fCSAPPM showed significant positive correlations with BV/TVTrab (ρ = 0.610; p < 0.001), CDTrab (ρ = 0.679; p < 0.001), Tb.NTrab (ρ = 0.522; p = 0.006), Tb.ThTrab (ρ = 0.415; p = 0.035), and ADTrab (ρ = 0.514; p = 0.007). Cortical bone parameters also demonstrated a significant positive correlation with fCSAPPM (BV/TVCort: ρ = 0.584; p = 0.002; ADCort: ρ = 0.519; p = 0.007). FIPsoas was negatively correlated with TMDCort (ρ =  - 0.622; p < 0.001).

CONCLUSION

This study highlights the close interactions between the bone microstructure of the lumbar pedicle and the paraspinal muscle morphology. These findings give us further insights into the interaction between the lumbar pedicle microstructure and paraspinal muscles.

Multiple Mechanisms Explain Genetic Effects at the CPED1-WNT16 Bone Mineral Density Locus

PURPOSE OF REVIEW

Chromosome region 7q31.31, also known as the CPED1-WNT16 locus, is robustly associated with BMD and fracture risk. The aim of the review is to highlight experimental studies examining the function of genes at the CPED1-WNT16 locus.

RECENT FINDINGS

Genes that reside at the CPED1-WNT16 locus include WNT16, FAM3C, ING3, CPED1, and TSPAN12. Experimental studies in mice strongly support the notion that Wnt16 is necessary for bone mass and strength. In addition, roles for Fam3c and Ing3 in regulating bone morphology in vivo and/or osteoblast differentiation in vitro have been identified. Finally, a role for wnt16 in dually influencing bone and muscle morphogenesis in zebrafish has recently been discovered, which has brought forth new questions related to whether the influence of WNT16 in muscle may conspire with its influence in bone to alter BMD and fracture risk.

Roles of miR-196a and miR-196b in Zebrafish Motor Function

Background: The exertion of motor function depends on various tissues, such as bones and muscles. miR-196 has been widely studied in cancer and other fields, but its effect on bone and skeletal muscle is rarely reported. In order to explore the role of miR-196 family in bone and skeletal muscle, we used the previously successfully constructed miR-196a-1 and miR-196b gene knockout zebrafish animal models for research. Methods: The behavioral trajectories of zebrafish from 4 days post-fertilization (dpf) to 7 dpf were detected to analyze the effect of miR-196a-1 and miR-196b on motor ability. Hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) were used to detect the dorsal muscle tissue of zebrafish. The bone tissue of zebrafish was detected by microcomputed tomography (micro-CT). Real-time PCR was used to detect the expression levels of related genes, including vcp, dpm1, acta1b, mylpfb, col1a1a, bmp8a, gdf6a, and fgfr3. Results: The behavioral test showed that the total behavioral trajectory, movement time, and movement speed of zebrafish larvae were decreased in the miR-196a-1 and miR-196b gene knockout lines. Muscle tissue analysis showed that the structure of muscle fibers in the zebrafish lacking miR-196a-1 and miR-196b was abnormal and was characterized by vacuolar degeneration of muscle fibers, intranuclear migration, melanin deposition, and inflammatory cell infiltration. Bone CT examination revealed decreased bone mineral density and trabecular bone number. The real-time PCR results showed that the expression levels of vcp, dpm1, gdf6a, fgfr3, and col1a1a were decreased in the miR-196b gene knockout group. The expression levels of dpm1, acta1b, mylpfb, gdf6a, and col1a1a were decreased, and the expression level of fgfr3 was increased in the miR-196b gene knockout group compared with the wild-type group. Conclusions: miR-196a-1 and miR-196b play an important role in muscle fiber structure, bone mineral density, and bone trabecular quantity by affecting the expression of vcp, dpm1, acta1b, mylpfb, gdf6a, fgfr3, and col1a1a and then affect the function of the motor system

Long-term human spaceflight and inflammaging: Does it promote aging?

Spaceflight and its associated stressors, such as microgravity, radiation exposure, confinement, circadian derailment and disruptive workloads represent an unprecedented type of exposome that is entirely novel from an evolutionary stand point. Within this perspective, we aimed to review the effects of prolonged spaceflight on immune-neuroendocrine systems, brain and brain-gut axis, cardiovascular system and musculoskeletal apparatus, highlighting in particular the similarities with an accelerated aging process. In particular, spaceflight-induced muscle atrophy/sarcopenia and bone loss, vascular and metabolic changes, hyper and hypo reaction of innate and adaptive immune system appear to be modifications shared with the aging process. Most of these modifications are mediated by molecular events that include oxidative and mitochondrial stress, autophagy, DNA damage repair and telomere length alteration, among others, which directly or indirectly converge on the activation of an inflammatory response. According to the inflammaging theory of aging, such an inflammatory response could be a driver of an acceleration of the normal, physiological rate of aging and it is likely that all the systemic modifications in turn lead to an increase of inflammaging in a sort of vicious cycle. The most updated countermeasures to fight these modifications will be also discussed in the light of their possible application not only for astronauts' benefit, but also for older adults on the ground.

Comparative evaluation of trabecular bone structures of bruxist and non-bruxist individuals with bone apposition in the mandible angle region by fractal analysis

OBJECTIVE

This study aimed to compare the trabecular internal structure of different regions of the mandible according to the grades of appositional classification in the mandible angle region in probable bruxist individuals and non-bruxist G0(Convex course of the basal cortex, no directional change, no bone apposition) individuals by measuring fractal dimension (FD) on panoramic radiographs.

METHODS

200 sample jaws, bilaterally, of 80 probable bruxists and 20 non-bruxist G0 individuals were included in the study. According to the classification in the literature, each mandible angle apposition severity was classified as G0-G1-G2-G3. FD was calculated by selecting the region of interest (ROI) area of 7 regions from each sample. Gender differences in changes between ROIs in radiographs and independent samples t-test were evaluated. Relation between categorical variables was determined by chi-square test (p < .05).

RESULTS

In the comparison of the probable bruxist and non-bruxist G0 groups, FD was found to be statistically significantly higher in the mandible angle (p = 0.013) and cortical bone (p = 0.000) regions in the probable bruxist group than in the non-bruxist G0 group. There is a statistically significant difference between probable bruxist G0 and non-bruxist G0 grades in terms of FD averages in cortical bone (p < 0.001). A statistically significant difference was found in the relationship of ROIs with gender in canine apex (p = 0.021) and canine distal (p = 0.041) regions.

CONCLUSION

FD was found to be higher in the mandibular angle region and cortical bone in probable bruxist individuals than in non-bruxist G0 individuals. Morphological changes seen in the mandible angulus region may be a finding that may raise suspicion for bruxism for clinicians.

Evaluation of mandibular trabecular bone by fractal analysis on panoramic radiograph in paediatric patients with sleep bruxism

OBJECTIVE

To evaluate the trabecular bone density in the mandible of paediatric patients diagnosed with sleep bruxism (SB) using the fractal analysis method on panoramic radiographs.

METHODS

A total of 37 patients whose anamnesis and clinical signs were compatible with SB were diagnosed with SB using BiteStrip^® . Three areas were identified on the panoramic radiographs of the patients: the geometric center of the condyle, the angulus region under the mandibular canal, and the distal region of the mental foramen. Regions of interest (ROIs) of 60 × 60 pixels were selected in these three locations, and fractal dimensions (FDs) were calculated. Results were compared with the control group.

RESULTS

There was no statistically significant difference between the right and left FD values, and male and female FD values in all regions and both groups (p > .05). In the angulus (p = .03) and condyle (p = .03) regions, the SB group had a significantly higher FD value than the control group. There was no statistically significant difference between the SB and control groups in the corpus region (p = .98). A moderate negative correlation arose between age and condyle FD values among controls (r = -0.38, p = .02).

CONCLUSION

Fractal dimension values evaluating trabeculation of the mandibular bone are affected by SB in the angulus and condyle regions.

Differences in lumbar paraspinal muscle morphology in patients with sagittal malalignment undergoing posterior lumbar fusion surgery

PURPOSE

To investigate whether (1) there is a difference between patients with normal or sagittal spinal and spinopelvic malalignment in terms of their paraspinal muscle composition and (2) if sagittal malalignment can be predicted using muscle parameters.

METHODS

A retrospective review of patients undergoing posterior lumbar fusion surgery was conducted. A MRI-based muscle measurement technique was used to assess the cross-sectional area, the functional cross-sectional area, the intramuscular fat and fat infiltration (FI) for the psoas and the posterior paraspinal muscles (PPM). Intervertebral disc degeneration was graded for levels L1 to S1. Sagittal vertical axis (SVA; ≥ 50 mm defined as spinal malalignment), pelvic incidence (PI) and lumbar lordosis (LL) were measured, and PI-LL mismatch (PI-LL; ≥ 10° defined as spinopelvic malalignment) was calculated. A receiver operating characteristic (ROC) analysis was conducted to determine the specificity and sensitivity of the FIPPM for predicting sagittal malalignment.

RESULTS

One hundred and fifty patients were analysed. The PI-LL and SVA malalignment groups were found to have a significantly higher FIPPM (PI-LL:47.0 vs. 42.1%; p = 0.019; SVA: 47.7 vs. 41.8%; p = 0.040). ROC analysis predicted sagittal spinal malalignment using FIPPM (cut-off value 42.69%) with a sensitivity of 73.4% and a specificity of 54.1% with an area under the curve of 0.662.

CONCLUSION

Significant differences in the muscle composition between normal and malalignment groups with respect to FIPPM in both sagittal spinal and spinopelvic alignment were found. This work underlines the imminent impact of the paraspinal musculature on the sagittal alignment.

Compartment-specific effects of muscle strength on bone microarchitecture in women at high risk of osteoporosis

BACKGROUND

It is well known that skeletal integrity is influenced by the musculature. Poor muscle strength (i.e. sarcopenia) is considered a major predictor of fragility fractures. While this observation appears particularly relevant for older women with increased risk of osteoporosis, there has been no comprehensive investigation to determine the influence of muscle performance on compartment-specific bone microarchitecture in multiple body regions.

METHODS

We retrospectively analysed data from different muscle performance and bone microarchitecture assessments in 230 women (aged 21 to 87 years) at high risk of osteoporosis. Muscle performance tests included grip strength and chair rising test (CRT) combined with mechanography. Balance was determined by Romberg posturography. Areal bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) at the hip and lumbar spine. Compartment-specific volumetric BMD, microarchitecture, and geometry were assessed by second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT) at multiple skeletal sites (distal radius, tibia, and fibula). Regression models were applied to test for interactions between muscle and bone parameters. Subgroups were defined to compare women with osteoporosis and osteosarcopenia regarding BMD and microarchitecture.

RESULTS

While osteoporosis was diagnosed in 115/230 (50.0%) women, sarcopenia was detected in 38/230 (16.5%). Positive associations of both grip strength and CRT maximum force with cortical geometric and microarchitectural parameters were detected at all measured sites, with the strongest effect applying to CRT maximum force and tibial parameters (e.g. tibial cortical area R²  = 0.36, P < 0.0001, and tibial cortical thickness R²  = 0.26, P < 0.0001). Balance parameters showed much weaker or no associations with HR-pQCT parameters. Major associations between muscle strength and trabecular parameters could not be confirmed. Age and body mass index were confirmed as negative and positive predictors for several microarchitectural parameters, respectively. An independent predictive value of grip strength on radial, tibial, and fibular (all P < 0.01) cortical area and of CRT maximum relative force on cortical thickness (all P < 0.05) was revealed. Women with osteosarcopenia showed significantly reduced cortical HR-pQCT parameters but no differences in DXA values compared with women with osteoporosis but no sarcopenia. Stratification by fracture and treatment status revealed that vertebral fractures and denosumab treatment altered the muscle-bone interaction.

CONCLUSIONS

A systemic interaction between muscle strength and bone microarchitecture was demonstrated, and this interaction appears to be primarily with the cortical bone compartment. The value of muscle assessments in fracture risk evaluation may be partly mediated by their effects on bone microarchitecture.

Childhood type 1 diabetes is associated with abnormal bone development

OBJECTIVE

To describe bone mineral density (BMD), bone structure, and fracture prevalence in adolescents with type 1 diabetes (T1D) and explore their associations with glycemic control and microvascular complications.

RESEARCH DESIGN AND METHODS

Cross sectional study of 64 adolescents (38 males) with T1D duration >10 years who underwent dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), fracture survey, plantar fascia thickness, and microvascular complications assessment.

RESULTS

Mean age was 16.6 ± 2.1 years, diabetes duration 12.8 ± 2.2 years and HbA1c 8.9 ± 1.7% (74 mmol/mol). Fracture prevalence was 50%. DXA areal BMD (Z-score) was reduced for femoral neck (-0.5 ± 1.3, p = 0.008) and arm (-0.4 ± 1.0, p < 0.001), while total areal BMD and lumbar spine BMD were normal. In pQCT (Z-score), trabecular volumetric BMD (vBMD) was reduced for tibia (-0.4 ± 0.8, p < 0.001) and radius (-0.8 ± 1.4, p < 0.001) whereas cortical vBMD was increased at both sites (tibia: 0.5 ± 0.6, p < 0.001, radius: 0.7 ± 1.5, p < 0.001). Muscle cross-sectional area (CSA) was reduced for upper (-0.6 ± 1.2, p < 0.001) and lower (-0.4 ± 0.7, p < 0.001) limbs. DXA total areal BMD was positively correlated with BMI (p < 0.01) and age at T1D diagnosis (p = 0.04). Lower radial bone CSA, total and lumbar spine BMD were associated with autonomic nerve dysfunction. HbA1c, diabetes duration, fracture history and other microvascular complications were not significantly associated with bone parameters.

CONCLUSIONS

Adolescents with childhood-onset T1D have site-specific bone deficits in upper and lower limbs but normal total and lumbar spine BMD. T1D appears to have differential effects on trabecular and cortical bone compartments. Future longitudinal analysis is warranted to examine whether these changes translate in to increased fracture risk.

Children with Spinal Muscular Atrophy Have Reduced Vertebral Body Height and Depth and Pedicle Size in Comparison to Age-Matched Healthy Controls

BACKGROUND

Most children with spinal muscular atrophy (SMA) develop spinal deformity, which may require surgical intervention. In addition to poor bone stock, vertebral body shape may hinder the placement of spinal implants resulting in complications and poor outcome. The aim of this study was to analyze whether vertebral body morphology of children and adolescents with SMA is altered in comparison to healthy age-matched controls.

METHODS

In this prospective cohort study, 17 children with SMA (mean age 8.7 ±1.0 years) and 13 adolescents with SMA (mean age 13.6 ±1.4 years), all with some degree of neuromuscular scoliosis, were analyzed by standardized radiographic measurements to evaluate vertebral body height and depth. Results were compared with age-matched healthy controls (n = 10 children; mean age 9.1 ± 1.6 years; n = 20 adolescents, mean age 13.1 ± 0.5 years). Computed tomography scans of 27 adolescents with SMA (13.5 ±1.2 years) and 25 healthy age-matched controls (13.8 ±2.0 years) were analyzed to define pedicle diameters.

RESULTS

All children and adolescents with SMA had decreased vertebral height and depth in comparison to age-matched healthy controls. In adolescents, reduced depth was more pronounced than height in the thoracic spine. Pedicle size was significantly reduced in the lower thoracic and lumbar area.

CONCLUSIONS

Reduced vertebral body height and depth and pedicle size in children and adolescents with SMA may influence surgical treatment of spinal deformity. Surgeons should be aware of anatomical differences and choose implant devices accordingly.

Mechanical Disturbance of Osteoclasts Induces ATP Release That Leads to Protein Synthesis in Skeletal Muscle through an Akt-mTOR Signaling Pathway

Muscle and bone are tightly integrated through mechanical and biochemical signals. Osteoclasts are cells mostly related to pathological bone loss; however, they also start physiological bone remodeling. Therefore, osteoclast signals released during bone remodeling could improve both bone and skeletal muscle mass. Extracellular ATP is an autocrine/paracrine signaling molecule released by bone and muscle cells. Then, in the present work, it was hypothesized that ATP is a paracrine mediator released by osteoclasts and leads to skeletal muscle protein synthesis. RAW264.7-derived osteoclasts were co-cultured in Transwell^® chambers with flexor digitorum brevis (FDB) muscle isolated from adult BalbC mice. The osteoclasts at the upper chamber were mechanically stimulated by controlled culture medium perturbation, resulting in a two-fold increase in protein synthesis in FDB muscle at the lower chamber. Osteoclasts released ATP to the extracellular medium in response to mechanical stimulation, proportional to the magnitude of the stimulus and partly dependent on the P2X₇ receptor. On the other hand, exogenous ATP promoted Akt phosphorylation (S473) in isolated FDB muscle in a time- and concentration-dependent manner. ATP also induced phosphorylation of proteins downstream Akt: mTOR (S2448), p70S6K (T389) and 4E-BP1 (T37/46). Exogenous ATP increased the protein synthesis rate in FDB muscle 2.2-fold; this effect was blocked by Suramin (general P2X/P2Y antagonist), LY294002 (phosphatidylinositol 3 kinase inhibitor) and Rapamycin (mTOR inhibitor). These blockers, as well as apyrase (ATP metabolizing enzyme), also abolished the induction of FDB protein synthesis evoked by mechanical stimulation of osteoclasts in the co-culture model. Therefore, the present findings suggest that mechanically stimulated osteoclasts release ATP, leading to protein synthesis in isolated FDB muscle, by activating the P2-PI3K-Akt-mTOR pathway. These results open a new area for research and clinical interest in bone-to-muscle crosstalk in adaptive processes related to muscle use/disuse or in musculoskeletal pathologies.

Effects of Muscles on Bone Metabolism—with a Focus on Myokines

Skeletal muscles and bones, the largest tissues in the body of a non-obese person, comprise the musculoskeletal system, which allows mobility and protects internal organs. Although muscles and bones are closely related throughout life, observations during development and aging and in human and animal disuse models have revealed the synchronization of tissue mass such that muscle phenotype changes precede alterations in bone mineral density and strength. This review discussed that mechanical forces, which have been the traditional research focus, are not the only mechanism by which muscle-derived signals may affect bone metabolism and emphasized the significance of skeletal muscles as an endocrine organ that secretes bone-regulatory factors. Consequently, both mechanical and biochemical aspects should be considered to fully understand muscle–bone crosstalk. This review also suggested that specific myokines could be ideal therapeutic targets for osteoporosis to both increase bone formation and reduce bone resorption; moreover, these myokines could also be potential circulating biomarkers to predict musculoskeletal health.

Is Radiographic Osteoporotic Hip Morphology A Predictor For High Mortality Following Intertrochanteric Femur Fractures?: Osteoporotic Hip Morphology & Mortality

INTRODUCTION

Factors related to mortality after intertrochanteric femur fractures (ITFF) have been investigated intensively in the literature except for radiographic osteoporotic hip morphology. The aim of this study is to investigate the relationship between mortality and radiographic osteoporotic hip morphology of patients with ITFF.

PATIENTS AND METHODS

Patients who underwent surgery between the dates of January 2012 and June 2018 due to ITFF were retrospectively reviewed. Osteoporotic status of the proximal femur was determined based on Singh Index grading and Dorr classification systems on preoperative anteroposterior pelvis radiographs of contralateral hips. The mortality rates of the patients were measured at 1st, 3rd, 6th, and 12th months. For controlling the confounders, multiple regression analysis was performed.

RESULTS

A total of 321 consecutive ITFFs were included in the study. The mean age of the patients was 81.5 ± 6.6 years. All patients were treated with osteosynthesis utilizing a cephalomedullary nail. The overall mortality rates at 1st, 3rd, 6th, and 12th months were 7.2%, 13.4%, 16.2%, 22.7%, respectively. There was 2.196 (1.140 - 4.229) folds increase in the mortality rate of patients with the Dorr type C femurs at 6th month (p=0.019). However, Singh index grade was not significantly associated with mortality.

CONCLUSION

Patients with Dorr type C femur seem to have 2.1 times increased mortality at 6th months following ITFFs. A simple anteroposterior pelvis radiograph obtained during the initial evaluation of the patients may be used to estimate the mortality rate after ITFF.

Association of decreased muscle mass with reduced bone mineral density in patients with Graves' disease

AIM

This study aimed to determine the association of decreased muscle mass with reduced bone mineral density in patients with Graves' disease.

METHODS

A total of 758 patients with Graves' disease at diagnosis (mean age 41.2 years) were enrolled for a cross-sectional study; of these, 287 were enrolled for a cohort study with a median follow-up of 24 months. Meanwhile, 1164 age- and sex-matched healthy controls were recruited. All participants underwent dual-energy x-ray absorptiometry and muscle mass index (ASMI) measurements. The changes in ASMI and bone mineral density (BMD) were calculated from the measurements made at a gap of 2 years.

RESULTS

The BMD of patients with Graves' disease was still significantly lower after normalizing serum thyroid hormone levels compared with that of healthy controls. ASMI positively correlated with BMD in patients with Graves' disease (lumbar BMD, r = 0.210; femoral neck BMD, r = 0.259; hip BMD, r = 0.235; P < 0.001), and this relationship persisted after successful anti-thyroid therapy (lumbar BMD, r = 0.169; femoral neck BMD, r = 0.281; hip BMD, r = 0.394; P < 0.001). Low muscle mass was associated with low BMD (OR, 1.436; 95% CI, 1.026-2.010). Improving the muscle mass led to changes in the bone mass of the femoral neck (OR, 0.420; 95% CI, 0.194-0.911) and hip (OR, 0.217; 95% CI, 0.092-0.511) during the follow-up. However, this phenomenon was not observed in lumbar and bone turnover markers.

CONCLUSIONS

The recovery of bone mass might be related to the recovery of the muscle mass. Patients with Graves' disease should be helped to regain their muscle mass and thus accelerate the recovery of bone mass while administering anti-thyroid therapy.

Muscle-bone axis in children with chronic kidney disease: current knowledge and future perspectives

Bone and muscle tissue are developed hand-in-hand during childhood and adolescence and interact through mechanical loads and biochemical pathways forming the musculoskeletal system. Chronic kidney disease (CKD) is widely considered as both a bone and muscle-weakening disease, eventually leading to frailty phenotype, with detrimental effects on overall morbidity. CKD also interferes in the biomechanical communication between two tissues. Pathogenetic mechanisms including systemic inflammation, anorexia, physical inactivity, vitamin D deficiency and secondary hyperparathyroidism, metabolic acidosis, impaired growth hormone/insulin growth factor 1 axis, insulin resistance, and activation of renin-angiotensin system are incriminated for longitudinal uncoordinated loss of bone mineral content, bone strength, muscle mass, and muscle strength, leading to mechanical impairment of the functional muscle-bone unit. At the same time, CKD may also interfere in the biochemical crosstalk between the two organs, through inhibiting or stimulating the expression of certain osteokines and myokines. This review focuses on presenting current knowledge, according to in vitro, in vivo, and clinical studies, concerning the pathogenetic pathways involved in the muscle-bone axis, and suggests approaches aimed at preventing bone loss and muscle wasting in the pediatric population. Novel therapeutic targets for preserving musculoskeletal health in the context of CKD are also discussed.

Bone Microarchitecture Decline and Risk of Fall and Fracture in Men With Poor Physical Performance-The STRAMBO Study

CONTEXT

High fracture risk in individuals with low muscle strength is attributed to high risk of falls.

OBJECTIVE

This work aims to study the association of muscle mass and physical performance with bone microarchitecture decline and risk of fall and nonvertebral fracture in men.

METHODS

A prospective, 8-year follow-up of a cohort was conducted among the general population. A total of 821 volunteer men aged 60 and older participated. Hip areal bone mineral density (aBMD) and appendicular lean mass (ALM) were assessed at baseline by dual x-ray absorptiometry. Lower-limb relative ALM (RALM-LL) is ALM-LL/(leg length)2. The physical performance score reflects the ability to perform chair stands and static and dynamic balance. Bone microarchitecture was assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) at baseline and after 4 and 8 years. Statistical analyses were adjusted for shared risk factors. Outcome measurements included the rate of change in the HR-pQCT indices, incident falls, and fractures.

RESULTS

Cortical bone loss and estimated bone strength decline were faster in men with low vs normal RALM-LL (failure load: -0.74 ± 0.09 vs -0.43 ± 0.10%/year; P < .005). Differences were similar between men with poor and those with normal physical performance (failure load: -1.12 ± 0.09 vs -0.40 ± 0.05%/year; P < .001). Differences were similar between men having poor performance and low RALM-LL and men having normal RALM-LL and performance (failure load: -1.40 ± 0.17 vs -0.47 ± 0.03%/year; P < .001). Men with poor physical performance had a higher risk of fall (hazard ratio [HR] = 3.52; 95% CI, 1.57-7.90, P < .05) and fracture (HR = 2.68; 95% CI, 1.08-6.66, P < .05).

CONCLUSION

Rapid decline of bone microarchitecture and estimated strength in men with poor physical performance and low RALM-LL may contribute to higher fracture risk.

Estrogen depletion on In vivo osteocyte calcium signaling responses to mechanical loading

Microstructural adaptation of bone in response to mechanical stimuli is diminished with estrogen deprivation. Here we tested in vivo whether ovariectomy (OVX) alters the acute response of osteocytes, the principal mechanosensory cells of bone, to mechanical loading in mice. We also used super resolution microscopy (Structured Illumination microscopy or SIM) in conjunction with immunohistochemistry to assess changes in the number and organization of "osteocyte mechanosomes" - complexes of Panx1 channels, P2X7 receptors and CaV3 voltage-gated Ca²⁺ channels clustered around α_vβ₃ integrin foci on osteocyte processes. Third metatarsals bones of mice expressing an osteocyte-targeted genetically encoded Ca²⁺ indicator (DMP1-GCaMP3) were cyclically loaded in vivo to strains from 250 to 3000 με and osteocyte intracellular Ca²⁺ signaling responses were assessed in mid-diaphyses using multiphoton microscopy. The number of Ca²⁺ signaling osteocytes in control mice increase monotonically with applied strain magnitude for the physiological range of strains. The relationship between the number of Ca²⁺ signaling osteocytes and loading was unchanged at 2 days post-OVX. However, it was altered markedly at 28 days post-OVX. At loads up to 1000 με, there was a dramatic reduction in number of responding (i.e. Ca²⁺ signaling) osteocytes; however, at higher strains the numbers of Ca²⁺ signaling osteocytes were similar to control mice. OVX significantly altered the abundance, make-up and organization of osteocyte mechanosome complexes on dendritic processes. Numbers of α_vβ₃ foci also staining with either Panx 1, P2X7R or CaV3 declined by nearly half after OVX, pointing to a loss of osteocyte mechanosomes on the dendritic processes with estrogen depletion. At the same time, the areas of the remaining foci that stained for α_vβ₃ and channel proteins increased significantly, a redistribution of mechanosome components suggesting a potential compensatory response. These results demonstrate that the deleterious effects of estrogen depletion on skeletal mechanical adaptation appear at the level of mechanosensation; osteocytes lose the ability to sense small (physiological) mechanical stimuli. This decline may result at least partly from changes in the structure and organization of osteocyte mechanosomes, which contribute to the distinctive sensitivity of osteocytes (particularly their dendritic processes) to mechanical stimulation.

Physical capability, physical activity, and their association with femoral bone mineral density in adults aged 40 years and older: The Tromsø study 2015-2016

Since muscles can influence bone growth and vice versa, we examined if level of physical activity and physical capability tests can predict areal bone mineral density (aBMD). Both high activity level and good test performance were associated with higher aBMD, especially in women.

INTRODUCTION

Muscle influences bone formation and vice versa. Tests of physical capability and level of physical activity reflect various muscle qualities. We assessed the associations between total hip aBMD and physical activity as well as a range of standardized physical capability tests in an adult general population.

METHODS

A total of 3 533 women and men aged 40-84 years, participating in the population-based cross-sectional Tromsø study in Norway in 2015-2016, were included. Linear regression was used to assess associations between aBMD and physical activity and the physical capability tests grip strength, Timed Up and Go (TUG), Short Physical Performance Battery (SPPB), and standing balance. Non-linear associations were examined in cubic spline models. Standardized regression coefficients were calculated to compare effect sizes across physical capability measures.

RESULTS

In fully adjusted models, higher physical activity was positively associated with total hip aBMD in both sexes compared to a sedentary lifestyle. All tests of physical capability were associated with aBMD in women, SPPB showing the strongest association although effect sizes were too small to indicate clinically significant differences (1 point increase corresponded to an aBMD increase of 0.009 g/cm², CI = 0.005 to 0.012). In men, SPPB and its subtests were associated with aBMD with chair rises showing the strongest association (1 s increase in execution time corresponded to an aBMD decrease of 0.005 g/cm², CI = 0.008 to 0.002).

CONCLUSION

Physical activity was associated with aBMD, and tests of physical capability can account for some of the aBMD variations in adults aged 40 years and older, especially in women.

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.

[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.

Effect of 12-weeks elastic band resistance training on MyomiRs and osteoporosis markers in elderly women with Osteosarcopenic obesity: a randomized controlled trial

Background

Interorgan communication networks established during exercise in several different tissues can be mediated by several exercise-induced factors. Therefore, the present study aimed to investigate the effects of resistance-type training using elastic band-induced changes of myomiRs (i.e., miR-206 and miR-133), vitamin D, CTX-I, ALP, and FRAX® score in elderly women with osteosarcopenic obesity (OSO).

Methods

In this randomized controlled trial, 63 women (aged 65–80 years) with Osteosarcopenic Obesity were recruited and assessed, using a dual-energy X-ray absorptiometry instrument. The resistance-type training via elastic bands was further designed three times per week for 12-weeks. The main outcomes were Fracture Risk Assessment Tool score, bone mineral content, bone mineral density, vitamin D, alkaline phosphatase, C-terminal telopeptides of type I collagen, expression of miR-206 and miR-133.

Results

There was no significant difference between the study groups in terms of the Fracture Risk Assessment Tool score (p = 0.067), vitamin D (p = 0.566), alkaline phosphatase (p = 0.334), C-terminal telopeptides of type I collagen (p = 0.067), microR-133 (p = 0.093) and miR-206 (p = 0.723).

Conclusion

Overall, the results of this study illustrated 12-weeks of elastic band resistance training causes a slight and insignificant improvement in osteoporosis markers in women affected with Osteosarcopenic Obesity.

Trial registration

Randomized controlled trial (RCT) (Iranian Registry of Clinical Trials, trial registration number: IRCT20180627040260N1.

Date of registration: 27/11/2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02374-9.

Identification of novel pleiotropic gene for bone mineral density and lean mass using the cFDR method

Bone mineral density (BMD) and whole-body lean mass (WBLM) are two important phenotypes of osteoporosis and sarcopenia. Previous studies have shown that BMD and lean mass were phenotypically and genetically correlated. To identify the novel common genetic factors shared between BMD and WBLM, we performed the conditional false discovery rate (cFDR) analysis using summary data of the genome-wide association study of femoral neck BMD (n = 53,236) and WBLM (n = 38,292) from the Genetic Factors for Osteoporosis Consortium (GEFOS). We identified eight pleiotropic Single Nucleotide Polymorphism (SNPs) (PLCL1 rs11684176 and rs2880389, JAZF1 rs198, ADAMTSL3 rs10906982, RFTN2/MARS2 rs7340470, SH3GL3 rs1896797, ST7L rs10776755, ANKRD44/SF3B1 rs11888760) significantly associated with femoral neck BMD and WBLM (ccFDR < 0.05). Bayesian fine-mapping analysis showed that rs11888760, rs198, and rs1896797 were the possible functional variants in the ANKRD44/SF3B1, JAZF1i, and SH3GL3 loci, respectively. Functional annotation suggested that rs11888760 was likely to comprise a DNA regulatory element and linked to the expression of RFTN2 and PLCL1. PLCL1 showed differential expression in laryngeal posterior cricoarytenoid muscle between rats of 6 months and 30 months of age. Our findings, together with PLCL1's potential functional relevance to bone and skeletal muscle function, suggested that rs11888760 was the possible pleiotropic functional variants appearing to coregulate both bone and muscle metabolism through regulating the expression of PLCL1. The findings enhanced our knowledge of genetic associations between BMD and lean mass and provide a rationale for subsequent functional studies of the implicated genes in the pathophysiology of diseases, such as osteoporosis and sarcopenia.

Deciphering Myostatin's Regulatory, Metabolic, and Developmental Influence in Skeletal Diseases

Current research findings in humans and other mammalian and non-mammalian species support the potent regulatory role of myostatin in the morphology and function of muscle as well as cellular differentiation and metabolism, with real-life implications in agricultural meat production and human disease. Myostatin null mice (mstn^−/−) exhibit skeletal muscle fiber hyperplasia and hypertrophy whereas myostatin deficiency in larger mammals like sheep and pigs engender muscle fiber hyperplasia. Myostatin’s impact extends beyond muscles, with alterations in myostatin present in the pathophysiology of myocardial infarctions, inflammation, insulin resistance, diabetes, aging, cancer cachexia, and musculoskeletal disease. In this review, we explore myostatin’s role in skeletal integrity and bone cell biology either due to direct biochemical signaling or indirect mechanisms of mechanotransduction. In vitro, myostatin inhibits osteoblast differentiation and stimulates osteoclast activity in a dose-dependent manner. Mice deficient in myostatin also have decreased osteoclast numbers, increased cortical thickness, cortical tissue mineral density in the tibia, and increased vertebral bone mineral density. Further, we explore the implications of these biochemical and biomechanical influences of myostatin signaling in the pathophysiology of human disorders that involve musculoskeletal degeneration. The pharmacological inhibition of myostatin directly or via decoy receptors has revealed improvements in muscle and bone properties in mouse models of osteogenesis imperfecta, osteoporosis, osteoarthritis, Duchenne muscular dystrophy, and diabetes. However, recent disappointing clinical trial outcomes of induced myostatin inhibition in diseases with significant neuromuscular wasting and atrophy reiterate complexity and further need for exploration of the translational application of myostatin inhibition in humans.

Maternal vitamin B12 in mice positively regulates bone, but not muscle mass and strength in post-weaning and mature offspring

Vitamin B₁₂ deficiency has been shown to affect bone mass in rodents and negatively impact bone formation in humans. In this study using mouse models, we define the effect of B₁₂ supplementation in the wild-type mother and B₁₂ deficiency in a mouse genetic model (Gif^−/− mice) during gestation on bone and muscle architecture and mechanical properties in the offspring. Analysis of bones from 4-wk-old offspring of the wild-type mother following vehicle or B₁₂ supplementation during gestation (from embryonic day 0.5 to 20.5) showed an increase in bone mass caused by an isolated increase in bone formation in the B₁₂-supplemented group compared with vehicle controls. Analysis of the effect of B₁₂ deficiency in the mother in a mouse genetic model (Gif^−/− mice) on the long bone architecture of the offspring showed a compromised cortical and trabecular bone mass, which was completely prevented by a single injection of B₁₂ in the B₁₂-deficient Gif^−/− mothers. Biomechanical analysis of long bones of the offspring born from B₁₂-supplemented wild-type mothers showed an increase in bone strength, and conversely, offspring born from B₁₂-deficient Gif^−/− mothers revealed a compromised bone strength, which could be rescued by a single injection of B₁₂ in the B₁₂-deficient Gif^−/− mother. Muscle structure and function analysis however revealed no significant effect on muscle mass, structure, and grip strength of B₁₂ deficiency or supplementation in Gif^−/− mice compared with littermate controls. Together, these results demonstrate the beneficial effect of maternally derived B₁₂ in the regulation of bone structure and function in the offspring.

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.

Identification of pleiotropic loci underlying hip bone mineral density and trunk lean mass

Bone mineral density (BMD) and lean body mass (LBM) not only have a considerable heritability each, but also are genetically correlated. However, common genetic determinants shared by both traits are largely unknown. In the present study, we performed a bivariate genome-wide association study (GWAS) meta-analysis of hip BMD and trunk lean mass (TLM) in 11,335 subjects from 6 samples, and performed replication in estimated heel BMD and TLM in 215,234 UK Biobank (UKB) participants. We identified 2 loci that nearly attained the genome-wide significance (GWS, p < 5.0 × 10-8) level in the discovery GWAS meta-analysis and that were successfully replicated in the UKB sample: 11p15.2 (lead SNP rs12800228, discovery p = 2.88 × 10-7, replication p = 1.95 × 10-4) and 18q21.32 (rs489693, discovery p = 1.67 × 10-7, replication p = 1.17 × 10-3). The above 2 pleiotropic loci may play a pleiotropic role for hip BMD and TLM development. So our findings provide useful insights that further enhance our understanding of genetic interplay between BMD and LBM.

The longitudinal associations between bone mineral density and appendicular skeletal muscle mass in Chinese community-dwelling middle aged and elderly men

Background

The present study aimed to investigate longitudinal associations between bone mineral densities (BMDs) and appendicular skeletal muscle (ASM) mass in different regions of the body using three different indicators, in Chinese community-dwelling middle-aged and elderly men.

Methods

A total of 1,343 men aged ≥ 40 years from a Chinese community were assessed at baseline (2014-2016), one-year follow-up (2016-2017; n = 648), two-year follow-up (2017-2018; n = 407), and three-year follow up (2018-2019; n = 208). At all the four time-points, measurements included ASM mass and BMDs for all regions of the body using dual-energy X-ray absorptiometry. A questionnaire was completed by patients and biochemical markers were assessed. We applied three different indicators to define ASM mass or lean mass respectively, including the appendicular skeletal muscle index (ASM adjusted by height, ASMI, according to the Asian Working Group for Sarcopenia), skeletal muscle index (ASM adjusted by weight, SMI, according to the International Working Group on Sarcopenia), and the appendicular skeletal muscle/body mass index (ratio of ASM and Body mass index (BMI), ASM/BMI, according to the Foundation for the National Institutes of Health). After adjusting for potential confounders, the generalized additive mixed model (GAMM) was used to analyze the trend in ASM mass over time, and to test the association between ASM mass and regional and whole-body BMDs.

Results

The incidence of low lean mass was 8.2% defined by ASMI, 16.3% defined by SMI, and 8.3% defined by ASM/BMI. There was a linear relationship between BMDs and ASM mass, and ASMI, ASM/BMI, and SMI gradually decreased with time. After adjusting for covariances, GAMM analysis determined longitudinal associations between BMDs and ASM mass by three indicators respectively: the skull BMD was negatively associated with ASM mass. For each unit increase in skull BMD, ASMI decreased by 0.28 kg/m² (95% confidence interval (CI) [-0.39 to -0.16]), ASM/BMI decreased by 0.02 m² (95% CI [-0.03 to -0.00]), and SMI decreased by 0.01% (95% CI[-0.01 to -0.00]). The remaining parameters (including whole-body mean BMD, thoracic spinal BMD, lumbar spinal BMD, hip BMD, femoral neck BMD, pelvic BMD, left arm BMD, right arm BMD, left leg BMD, right leg BMD) were positively correlated with ASM mass. The ASMI increased by 3.07 kg/m²for each unit increase in the femoral neck BMD (95% CI [2.31-3.84]). The ASM/BMI increased by 0.22 m²for each unit increase in the left arm BMD (95% CI [0.12-0.33]), and the SMI increased by 0.05% per unit increase in the left arm BMD (95% CI [0.02-0.08]).

Conclusions

Compared to ASMI and ASM/BMI, SMI was more sensitive to screen for the low lean mass. Skull BMD was negatively associated with ASM mass, while BMDs throughout the rest of the body were positively correlated with ASM mass among the middle-aged and elderly Chinese men.

Identification of Sclerostin as a Putative New Myokine Involved in the Muscle-to-Bone Crosstalk

Bone and muscle have been recognized as endocrine organs since they produce and secrete “hormone-like factors” that can mutually influence each other and other tissues, giving rise to a “bone–muscle crosstalk”. In our study, we made use of myogenic (C2C12 cells) and osteogenic (2T3 cells) cell lines to investigate the effects of muscle cell-produced factors on the maturation process of osteoblasts. We found that the myogenic medium has inhibitory effects on bone cell differentiation and we identified sclerostin as one of the myokines produced by muscle cells. Sclerostin is a secreted glycoprotein reportedly expressed by bone/cartilage cells and is considered a negative regulator of bone growth due to its role as an antagonist of the Wnt/β-catenin pathway. Given the inhibitory role of sclerostin in bone, we analyzed its expression by muscle cells and how it affects bone formation and homeostasis. Firstly, we characterized and quantified sclerostin synthesis by a myoblast cell line (C2C12) and by murine primary muscle cells by Western blotting, real-time PCR, immunofluorescence, and ELISA assay. Next, we investigated in vivo production of sclerostin in distinct muscle groups with different metabolic and mechanical loading characteristics. This analysis was done in mice of different ages (6 weeks, 5 and 18 months after birth) and revealed that sclerostin expression is dynamically modulated in a muscle-specific way during the lifespan. Finally, we transiently expressed sclerostin in the hind limb muscles of young mice (2 weeks of age) via in vivo electro-transfer of a plasmid containing the SOST gene in order to investigate the effects of muscle-specific overproduction of the protein. Our data disclosed an inhibitory role of the muscular sclerostin on the bones adjacent to the electroporated muscles. This observation suggests that sclerostin released by skeletal muscle might synergistically interact with osseous sclerostin and potentiate negative regulation of osteogenesis possibly by acting in a paracrine/local fashion. Our data point out a role for muscle as a new source of sclerostin.

Computed Tomography Evaluation of Forearm and Hand Muscles in Patients With Distal Radius Fracture

INTRODUCTION

Computed tomography (CT) can be used to assess bone status with measurement of Hounsfield unit (HU). The objective of this study was to evaluate whether HU of muscle might be associated with parameters of bone and muscle status.

METHODS

We reviewed 71 women aged over 50 yr of age who had distal radius fracture and underwent CT evaluation of affected wrist. We assessed HUs of forearm flexor muscles (flexor digitorum superficialis) and thenar muscles and bone HUs at the capitate and the ulnar head. Other parameters included femur neck and lumbar bone mineral density (BMD), upper extremity lean mass, hand grip strength, and muscle fiber cross-sectional area. We performed correlation analyses to determine associations between variables.

RESULTS

Thenar and forearm muscle HUs were significantly correlated with each other, but not with other parameters. HUs of the capitate and ulnar head were positively correlated with femur neck and lumbar BMDs and inversely correlated with age. Ulnar head HU was positively correlated hand grip strength.

CONCLUSIONS

HUs of forearm and thenar muscles did not show significant correlations with bone or muscle parameters, although bone HUs correlated well with bone mineral densities. These results support the opportunistic use of CT for evaluating bone fragility. Clinical usefulness of muscle HU measurement needs further studies.

Association between forearm cortical bone properties and handgrip strength in women with distal radius fractures: A cross-sectional study

OBJECTIVES

Mechanical and biochemical bone properties are influenced by muscles. However, the muscle-bone interaction has not been fully elucidated regarding the upper extremities. The objective of the present study was to evaluate the mechanical muscle-bone interaction at the forearm by evaluating the relationship between the properties of three-dimensional (3D) forearm cortical bone models derived from conventional computed tomography (CT) images and handgrip strength (HGS).

METHODS

A total of 108 women (mean age, 75.2 ± 9.4 years; range, 62-101 years) with a distal radius fracture who took conventional CT scans for the assessment of the fracture were included in this study. Distal radius 3D models were reconstructed and the average cortical bone density (Cd) and thickness (Ct) of the region of interest (ROI), which might be affected by the forearm flexor muscles, were calculated using a 3D modeling software. Clinical parameters including HGS, lumbar and hip bone mineral densities (BMDs), and other demographic factors were also obtained. A multivariate linear regression analysis was performed to identify relevant factors associated with HGS.

RESULTS

HGS was found to be independently associated with height and Cd, but no significant difference was found between HGS and Ct, age, weight, as well as lumber and hip BMDs.

CONCLUSIONS

Cortical bone density might be associated with HGS, which is generated by the forearm flexor muscles. Hence, the mechanical muscle-bone interaction in the upper extremities could be supported by the present study.

Bone-Muscle Mutual Interactions

PURPOSE OF REVIEW

The purpose of this review is to describe the current state of our thinking regarding bone-muscle interactions beyond the mechanical perspective.

RECENT FINDINGS

Recent and prior evidence has begun to dissect many of the molecular mechanisms that bone and muscle use to communicate with each other and to modify each other's function. Several signaling factors produced by muscle and bone have emerged as potential mediators of these biochemical/molecular interactions. These include muscle factors such as myostatin, Irisin, BAIBA, IL-6, and the IGF family and the bone factors FGF-23, Wnt1 and Wnt3a, PGE2, FGF9, RANKL, osteocalcin, and sclerostin. The identification of these signaling molecules and their underlying mechanisms offers the very real and exciting possibility that new pharmaceutical approaches can be developed that will permit the simultaneous treatments of diseases that often occur in combination, such as osteoporosis and sarcopenia.

Can bone mineral density loss in the non-weight bearing distal forearm predict mortality?

PURPOSE

Low bone mineral density (BMD) is associated with increased risk of fractures and mortality. We investigated if rate of BMD loss in the distal forearm over seven years predicted mortality.

METHODS

1725 postmenopausal women and 1879 men aged 50-74 who participated in the longitudinal Tromsø Study waves 4 (1994-95) and 5 (2001-2002) were included. Cox regression models adjusted for lifestyle- and health related variables were used to assess associations between BMD change over seven years and subsequent mortality during up to 17 years of follow-up in participants with normal and low BMD at baseline.

RESULTS

Baseline BMD decreased and seven-year bone loss increased with increasing age. Overall, mortality rates were higher among those with low versus normal BMD (38 vs 19 per 1000 py in women, 56 vs 34 in men) and at higher bone loss rates (rate ratio high:low = 1.2 in women, 1.7 in men). BMD change was associated with increased mortality only in men with normal baseline BMD. In this group, men with a BMD loss of >4% had significantly higher mortality (HR 1.50, 95% CI 1.21, 1.87) than men with increased or unchanged BMD. BMD change was not significantly associated with increased mortality in women or in men with low BMD at baseline.

CONCLUSIONS

BMD loss in the distal forearm was associated with increased mortality in men with normal BMD at baseline, but not in women. We found no clear association between BMD loss and mortality in those with low BMD at baseline.

The Systemic Effects of Exercise on Regulators of Muscle and Bone in Girls and Women

PURPOSE

To assess the systemic effects of an acute bout of moderate-intensity exercise on factors that are known to regulate muscle and bone growth in prepubertal girls and women.

METHODS

A total of 12 prepubertal girls (8-10 y) and 12 women (20-30 y) cycled at 60% maximal oxygen uptake for 1 hour followed by 1 hour recovery. Blood samples were collected at rest, mid-exercise, end of exercise, mid-recovery, and end of recovery. Plasma was analyzed for interleukin-6, chemokine ligand 1, fibroblast growth factor-2, total insulin growth factor-1 (IGF-1), and free IGF-1 using enzyme-linked immunosorbent assays assays.

RESULTS

Both groups had similar concentrations of systemic factors at baseline with the exception of free IGF-1, which was higher in girls (P = .001). Interleukin-6 response was lower in girls versus women (P = .04), with a difference of +105.1% at end of exercise (P < .001), +113.5% at mid-recovery (P = .001), and +93.2% at end of recovery (P = .02). Girls and women exhibited significant declines in chemokine ligand 1, fibroblast growth factor-2, and total IGF-1 during recovery.

CONCLUSION

Compared with women, an acute bout of moderate-intensity exercise in girls elicits a lower inflammatory response, suggesting that other mechanisms may be more important for driving the anabolic effects of exercise on muscle and bone in girls.