Marrow adiposity and bone: Review of clinical implications

Bioinformatics-Based Analysis of Ferroptosis-Related Biomarkers and the Prediction of Drugs Affecting the Adipogenic Differentiation of MSCs

Background: The imbalance between the osteogenic and adipogenic differentiation of mesenchymal stem cells (MSCs) is a key factor in the progression of osteoporosis; therefore, it is crucial to study the regulatory mechanisms that maintain this balance. Ferroptosis is a form of regulated cell death caused by the accumulation of lipid peroxides and is closely associated with various diseases. Changes in intracellular oxidative stress levels can affect the lineage allocation of MSCs. However, it remains unclear whether the disruption of intracellular oxidative stress levels caused by ferroptosis can influence the osteogenic-adipogenic differentiation balance of MSCs, and the mechanism underlying this influence in osteoporosis has not been fully elucidated. This study is the first to demonstrate through in vitro cell experiments that inhibiting ferroptosis can decrease the adipogenic differentiation of MSCs. Methods and Results: Through bioinformatics analysis, differentially expressed genes (DEGs) associated with the adipogenic differentiation of MSCs were identified from the GEO database. We then intersected these differentially expressed genes with a ferroptosis-related gene dataset and identified 118 ferroptosis-related differentially expressed genes (FRDEGs). Additionally, we explored the functional roles of FRDEGs through GO and KEGG analyses and found that these genes significantly impacted intracellular oxidative stress. Furthermore, we identified 10 key FRDEGs via protein-protein interaction (PPI) analysis. The diagnostic performance of these genes was evaluated by plotting receiver operating characteristic (ROC) curves, and the reliability of the diagmodel was validated using data from osteoporosis patients. We then constructed a mouse osteoporosis model and validated the mRNA expression levels of key FRDEGs via qRT-PCR, which revealed significant differences in expression in the osteoporosis group. Finally, molecular docking technology was used to identify two small molecules from the DrugBank database that are able to negatively regulate MSC adipogenic differentiation by inhibiting ferroptosis. Conclusions: The identified FRDEGs and small molecules offer novel diagnostic markers and therapeutic candidates for osteoporosis.

NELL2, a novel osteoinductive factor, regulates osteoblast differentiation and bone homeostasis through fibronectin 1/integrin-mediated FAK/AKT signaling

Neural EGFL-like 2 (NELL2) is a secreted protein known for its regulatory functions in the nervous and reproductive systems, yet its role in bone biology remains unexplored. In this study, we observed that NELL2 was diminished in the bone of aged and ovariectomized (OVX) mice, as well as in the serum of osteopenia and osteoporosis patients. In vitro loss-of-function and gain-of-function studies revealed that NELL2 facilitated osteoblast differentiation and impeded adipocyte differentiation from stromal progenitor cells. In vivo studies further demonstrated that the deletion of NELL2 in preosteoblasts resulted in decreased cancellous bone mass in mice. Mechanistically, NELL2 interacted with the FNI-type domain located at the C-terminus of Fibronectin 1 (Fn1). Moreover, we found that NELL2 activated the focal adhesion kinase (FAK)/AKT signaling pathway through Fn1/integrin β1 (ITGB1), leading to the promotion of osteogenesis and the inhibition of adipogenesis. Notably, administration of NELL2-AAV was found to ameliorate bone loss in OVX mice. These findings underscore the significant role of NELL2 in osteoblast differentiation and bone homeostasis, suggesting its potential as a therapeutic target for managing osteoporosis.

Effect of artificial gravity on calcaneal bone marrow adipose tissue and mineral content in female and male participants in 60 days of bed rest

Modulation of bone marrow adipose tissue (BMAT) with prolonged inactivity was reported in haemopoietic but not in non-haemopoietic bones. This prospective randomized controlled trial submitted 16 men and 8 women to 60 days of 6° head-down-tilt bed rest. They were assigned to control, continuous or intermittent artificial gravity (AG) interventions. The AG consisted of daily centrifugation at 2g for 30 min. The serial foot pain questionnaire, MRI and dual-energy X-ray absorptiometry of the calcaneus were performed at baseline, during bed rest and at reambulation. At baseline, all groups had comparable calcaneal BMAT (P = 0.581) and bone mineral density (BMD) (P = 0.574). After bed rest, 83% of participants reported foot pain. Calcaneal BMAT was not significantly modulated after 60 days of bed rest (control, +0.2% ± 0.8%; continuous AG, +0.5% ± 1.1%; and intermittent AG, +0.1% ± 1.5%; P = 0.368). Calcaneal BMD was reduced at reambulation days 3 and 11 after 60 days of bed rest (-0.05 ± 0.06 and -0.06 ± 0.12 g/cm2, respectively; P = 0.008 and P = 0.020). The AG interventions did not significantly alter calcaneal BMAT or BMD. Sex-based analyses demonstrated calcaneal BMD loss in men but not in women. Calcaneal BMAT and BMD were inversely correlated in women and in men (Spearman's ρ, -0.40 and -0.28, respectively; both P = 0.020). Sixty days of bed rest caused foot pain and calcaneal demineralization not rescued by AG interventions. Although inversely correlated with BMD, calcaneal BMAT was not statistically increased by 60 days of head-down-tilt bed rest, possibly owing to a ceiling effect, and no bone marrow reconversion was measured at reambulation. These results have clinical relevance when returning to activities after prolonged bed rest or returning from space.

Marrow Adiposity Content and Composition Are Not Associated With Incident Fragility Fractures in Postmenopausal Women: The ADIMOS Fracture Study

Context

Noninvasive measurement of bone marrow adipose tissue using magnetic resonance imaging and proton density fat fraction (PDFF) may enhance clinical fractures prediction in postmenopausal women.

Objective

This study aimed to assess the association between PDFF measurements and clinical fracture incidence.

Methods

A longitudinal study was conducted. Postmenopausal women with recent osteoporotic fractures (<12 months) and with osteoarthritis without fractures were included. Lumbar spine and proximal femur PDFFs were measured at baseline using water-fat imaging (WFI) and dual-energy x-ray absorptiometry scans. Clinical fractures were recorded during follow-up.

Results

Among 195 participants (mean age 67.4 ± 10.0 years, body mass index 27.2 ± 5.9 kg/m²), the PDFF (WFI-based) was higher at the proximal femur, particularly at the femoral head (90.0% ± 4.9%), compared to the lumbar spine (57.8% ± 9.6%). Over a mean follow-up period of 37.2 ± 11.6 months, 7 participants died, 29 (14.9%) experienced incident clinical fractures, and 1 was lost to follow-up. The lack of an association between WFI-based PDFFs and the incidence of clinical fractures was demonstrated regardless of the region of measurement (hazard ratio [HR] = 0.95 [95% CI 0.67-1.35], P = 0.77 at the lumbar spine, HR = 1.07 [95% CI 0.71-1.63], P = 0.74 at the femoral neck). Stepwise regression analysis did not alter these findings, and the variable "recent osteoporotic fractures" was found to be significantly associated with incident clinical fractures.

Conclusion

This study found no evidence of a relationship between PDFF and clinical fracture incidence in postmenopausal women. Further studies are necessary involving larger cohorts and longer follow-up periods.

Targeting p38 MAPK: A potential bridge between ER stress and age-related bone loss

The endoplasmic reticulum (ER) is crucial in the development of numerous age-related bone disorders. Notably, ER stress can precipitate bone loss by orchestrating inflammatory responses, apoptosis, and autophagy through the activation of the p38 MAPK pathway. Age-related bone loss diseases pose a significant burden on society and healthcare as the global population ages. This review provides a comprehensive analysis of recent research advancements, delving into the critical role of ER stress-activated p38 MAPK in inflammation, apoptosis, and autophagy, as well as its impact on bone formation and bone resorption. This review elucidates the molecular mechanisms underlying the involvement of ER stress-activated p38 MAPK in osteoporosis, rheumatoid arthritis, periodontitis, and osteoarthritis and discusses the therapeutic potential of targeting p38 MAPK. Furthermore, this review provides a scientific foundation for new therapeutic strategies by highlighting prospective research directions.

Preliminary study of proton magnetic resonance spectroscopy to assess bone marrow adiposity in the third metacarpus or metatarsus in Thoroughbred racehorses

BACKGROUND

Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses.

OBJECTIVES

To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the 1H spectra for the MC/MTIII to calculate fat content (FC).

STUDY DESIGN

Observational cross-sectional study.

METHODS

Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses. Each limb underwent magnetic resonance imaging (MRI) at 3 T followed by single-voxel MRS at three regions of interest (ROI) within MC/MTIII (lateral condyle, medial condyle, proximal bone marrow [PBM]). Percentage FC was calculated at each ROI. Each limb underwent computed tomography (CT) and bone mineral density (BMD) was calculated for the same ROIs. All MR and CT images were graded for sclerosis. Histology slides were graded for sclerosis and proximal marrow space was calculated. Pearson or Spearman correlations were used to assess the relationship between BMD, FC and marrow space. Kruskal-Wallis tests were used to check for differences between sclerosis groups for BMD or FC.

RESULTS

Eighteen limbs from 10 horses were included. A negative correlation was identified for mean BMD and FC for the lateral condyle (correlation coefficient = -0.60, p = 0.01) and PBM (correlation coefficient = -0.5, p = 0.04). There was a significant difference between median BMD for different sclerosis grades in the condyles on both MRI and CT. A significant difference in FC was identified between sclerosis groups in the lateral condyle on MRI and CT.

MAIN LIMITATIONS

Small sample size.

CONCLUSIONS

1H Proton MRS is feasible in the equine MC/MTIII. Further work is required to evaluate the use of this technique to predict fracture risk in racehorses.

The assessment of marrow adiposity in type 1 diabetic rabbits through magnetic resonance spectroscopy is linked to bone resorption

Background

Enhanced marrow adiposity is frequently linked with a decline in bone density. The underlying mechanisms responsible for bone loss in diabetes are not well understood. In this investigation, we employed an alloxan-induced diabetes rabbit model to unravel the association between marrow fat content and bone resorption, utilizing magnetic resonance spectroscopy.

Methods

Forty 4-month-old male New Zealand rabbits were randomly allocated into two groups: a control group and an alloxan-induced diabetic group, each consisting of 20 rabbits. Biochemical analyses covered plasma glucose, enzyme levels, lipid profiles, blood urea nitrogen, creatinine levels, and markers of bone turnover. Quantification of bone marrow adipose tissue utilized both MR spectroscopy and histological examinations. Dual-energy X-ray absorptiometry and microcomputed tomography were employed to determine bone density and trabecular bone microarchitectures. The expression levels of marrow adipocyte markers (peroxisome proliferator-activated receptor-gamma2, CCAAT/enhancer-binding protein-α, and fatty acid binding protein 4) and markers of bone resorption [tartrate-resistant acid phosphatase (TRACP) and cathepsin K] were assessed using RT-PCR.

Results

Diabetic rabbits exhibited significant increases in marrow fat fraction (MFF) over time (MFF increased by 13.2% at 1.5 months and 24.9% at 3 months relative to baseline conditions, respectively). These changes were accompanied by the deterioration of trabecular microarchitectures. Marrow adipogenesis was evident through a 31.0% increase in adipocyte size, a 60.0% rise in adipocyte number, a 103.3% increase in the percentage of adipocyte area, and elevated mRNA expressions of marrow adipocyte markers. Osteoclast markers (TRACP and cathepsin K RNA and serum TRACP5b levels) were elevated in diabetic rabbits. MFF exhibited a robust correlation with trabecular bone microarchitectures. A significant positive correlation was identified between ΔMFF and serum ΔTRACP5b levels. Moreover, MFF at 3 months showed a strong positive correlation with serum TRACP5b levels (r = 0.763), as well as with the mRNA expression of osteoclast markers, including TRACP (r = 0.784) and cathepsin K (r = 0.659), all with p <0.001.

Conclusions

Rabbits with type 1 diabetes experience an expansion of marrow adiposity, and this enhanced marrow adiposity is associated with increased osteoclast activity.

Skeletal Site-Specific Lipid Profile and Hematopoietic Progenitors of Bone Marrow Adipose Tissue in Patients Undergoing Primary Hip Arthroplasty

BACKGROUND/OBJECTIVES

Bone marrow adipose tissue (BMAT) has been described as an important biomechanic and lipotoxic factor with negative impacts on skeletal and hematopoietic system regeneration. BMAT undergoes metabolic and cellular adaptations with age and disease, being a source of potential biomarkers. However, there is no evidence on the lipid profile and cellularity at different skeletal locations in osteoarthritis patients undergoing primary hip arthroplasty.

METHODS

Acetabular and femoral bone marrow (BM) and gluteofemoral subcutaneous adipose tissue (gfSAT) were obtained from matched patients undergoing hip replacement surgery. BM, BMAT, and gfSAT were explored at the levels of total lipids, fatty acids, and cells by using thin-layerand gas chromatography, ex vivo cellular assays, and flow cytometry.

RESULTS

BMAT content was significantly higher in femoral than in acetabular BM. Total lipid analyses revealed significantly lower triglyceride content in femoral than in acetabular BMAT and gfSAT. Frequencies of saturated palmitic, myristic, and stearic acids were higher in femoral than in acetabular BMAT and gfSAT. The content of CD45+CD34+ cells within femoral BMAT was higher than in acetabular BMAT or gfSAT. This was associated with a higher incidence of total clonogenic hematopoietic progenitors and late erythroid colonies CFU-E in femoral BMAT when compared to acetabular BMAT, similar to their BM counterparts.

CONCLUSIONS

Collectively, our results indicate that the lipid profiles of hip bone and femoral BMAT impose significantly different microenvironments and distributions of cells with hematopoietic potential. These findings might bring forth new inputs for defining BMAT biology and setting novel directions in OA disease investigations.

Adiposity and Mineral Balance in Chronic Kidney Disease

PURPOSE OF REVIEW

Bone homeostasis is balanced between formation and resorption activities and remain in relative equilibrium. Under disease states this process is disrupted, favoring more resorption over formation, leading to significant bone loss and fracture incidence. This aspect is a hallmark for patients with chronic kidney disease mineral and bone disorder (CKD-MBD) affecting a significant portion of the population, both in the United States and worldwide. Further study into the underlying effects of the uremic microenvironment within bone during CKD-MBD are critical as fracture incidence in this patient population not only leads to increased morbidity, but also increased mortality. Lack of bone homeostasis also leads to mineral imbalance contributing to cardiovascular calcifications. One area understudied is the possible involvement of bone marrow adipose tissue (BMAT) during the progression of CKD-MBD.

RECENT FINDINGS

BMAT accumulation is found during aging and in several disease states, some of which overlap as CKD etiologies. Importantly, research has found presence of BMAT inversely correlates with bone density and volume. Understanding the underlying molecular mechanisms for BMAT formation and accumulation during CKD-MBD may offer a potential therapeutic avenue to improve bone homeostasis and ultimately mineral metabolism.

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Long-Term Follow-up After Ovariectomy Reveals Correlations Between Bone Marrow Adiposity and Trabecular Bone Quality in the Proximal Metaphysis of Tibiae in Rats

This study aimed to evaluate the correlation between BMAT and bone quality, describe the long-term effects of ovariectomy on bone, and investigate BMAT's spatial distribution. Fifteen-months-old female Sprague‒Dawley rats were studied, comparing ovariectomized (OVX, n = 22) and sham-operated (SHAM, n = 11) groups at 6 months. Tibias were analyzed for bone microarchitecture, BMAT (microcomputed tomography), mineral parameters (quantitative backscattered electron imaging), and bone composition (Raman microspectroscopy). The OVX tibias showed severe trabecular bone loss (lower bone volume/total volume, p < 0.001) with increased BMAT (higher adipose volume per marrow volume, p < 0.001), decreased mineral content (lower calcium concentration, p < 0.001), and altered organic components (lower mineral/matrix ratio in new bone, p = 0.03 trabecular surface, p < 0.001 trabecular core). When the data are pooled over both groups (SHAM and OVX), the adipose volume/marrow volume ratio was negatively correlated with bone volume/total volume (r =  - 0.79, p < 0.001) and mineral/matrix ratio (r =  - 0.37, p = 0.04 trabecular surface; r =  - 0.65, p < 0.001 trabecular core) and positively correlated with crystallinity (r = 0.55, p = 0.001 trabecular surface; r = 0.49, p = 0.006 trabecular core). The mineral/matrix ratio of trabecular surface new bone was strongly negatively correlated with the adipose compartment nearest to the bone surface. These findings suggest mechanisms underlying BMAT's role in bone resorption.

Bone Marrow Adiposity Alterations in Postmenopausal Women With Type 2 Diabetes Are Site-Specific

Context

Bone marrow adiposity (BMAT) alterations in patients with type 2 diabetes mellitus (T2DM) may contribute to adverse bone effects.

Objective

Characterization of BMAT content and composition in patients with well-controlled T2DM.

Methods

This cross-sectional study included 2 groups of postmenopausal women: one with T2DM and the other without. The proton density fat fraction (PDFF) of the lumbar spine and proximal femur, comprising the femoral head, neck, and diaphysis, was assessed using chemical shift-based water-fat separation imaging (WFI). Magnetic resonance imaging with spectroscopy (1H-MRS) was performed in a subgroup of participants to confirm the PDFF measurements and determine the apparent lipid unsaturation level (aLUL) at the L3 vertebrae and femoral neck. The association of imaging-based PDFFs and aLUL between diabetes groups was investigated by adjusting for confounding factors using a linear mixed model.

Results

Among 199 participants, patients with T2DM (n = 29) were significantly heavier (P < .001) and had a higher bone mineral density (BMD) (P < .001 for all sites) than nondiabetic patients (n = 170). When PDFFs were compared after adjusting for age, body mass index (BMI), and BMD, the femoral head WFI-based PDFF was lower in patients with T2DM (mean [standard error] 88.0% [0.7] vs 90.6% [0.3], P < .001). Moreover, the aLUL at the L3 vertebrae was lower in patients with T2DM (n = 16) than in without (n = 97) (mean [standard error] 3.9% [0.1] vs 4.3% [0.1], P = .02).

Conclusion

The content and composition of BMAT are modified in postmenopausal women with T2DM and these changes occur at specific sites.

Withaferin A Ameliorated the Bone Marrow Fat Content in Obese Male Mice by Favoring Osteogenesis in Bone Marrow Mesenchymal Stem Cells and Preserving the Bone Mineral Density

Obesity and osteoporosis are two prevalent conditions that are becoming increasingly common worldwide, primarily due to aging populations, imbalanced energy intake, and sedentary lifestyles. Obesity, characterized by excessive fat accumulation, and osteoporosis, marked by reduced bone density and increased fracture risk, are often interconnected. High-fat diets (HFDs) can exacerbate both conditions by promoting bone marrow adiposity and bone loss. The effect of WFA on the osteogenesis and adipogenesis was studied on the C3H10T1/2 cell line and bone marrow mesenchymal stem cells (BM-MSCs) isolated from mice. We used oil red O and alkaline phosphatase (ALP) staining to observe adipogenesis and osteogenesis, respectively, in MSCs. Real-time PCR and Western blot analyses were used to study the molecular effects of WFA on MSCs. We employed micro-CT to analyze the bone microarchitecture, bone mineral density (BMD), and abdominal fat mass in male mice. We have used osmium tetroxide (OsO4) staining to study the bone marrow fat. WFA induced the C3H10T1/2 cell line and BM-MSCs toward osteogenic lineage as evidenced by the higher ALP activity. WFA also downregulated the lipid droplet formation and adipocyte specific genes in MSCs. In the in vivo study, WFA also suppressed the bone catabolic effects of the HFD and maintained the bone microarchitecture and BMD in WFA-treated animals. The bone marrow adipose tissue was reduced in the tibia of WFA-treated groups in comparison with only HFD-fed animals. Withaferin A was able to improve the bone microarchitecture and BMD by committing BM-MSCs toward osteogenic differentiation and reducing marrow adiposity. The findings of this study could provide valuable insights into the therapeutic potential of Withaferin A for combating bone marrow obesity and osteoporosis, particularly in the context of diet-induced metabolic disturbances.

Bone Fragility in High Fat Diet-induced Obesity is Partially Independent of Type 2 Diabetes in Mice

Obesity and type 2 diabetes (T2D) are risk factors for fragility fractures. It is unknown whether this elevated risk is due to a diet favoring obesity or the diabetes that often occurs with obesity. Therefore, we hypothesized that the fracture resistance of bone is lower in mice fed with a high fat diet (45% kcal; HFD) than in mice that fed on a similar, control diet (10% kcal; LFD), regardless of whether the mice developed overt T2D. Sixteen-week-old, male NON/ShiLtJ mice (resistant to T2D) and age-matched, male NONcNZO10/LtJ (prone to T2D) received a control LFD or HFD for 21 weeks. HFD increased the bodyweight to a greater extent in the ShiLtJ mice compared to the NZO10 mice, while blood glucose levels were significantly higher in NZO10 than in ShiLtJ mice. As such, the glycated hemoglobin A1c (HbA1c) levels exceeded 10% in NZO10 mice, but it remained below 6% in ShiLtJ mice. Diet did not affect HbA1c. HFD lowered trabecular number and bone volume fraction of the distal femur metaphysis (micro-computed tomography or μCT) in both strains. For the femur mid-diaphysis, HFD significantly reduced the yield moment (mechanical testing by three-point bending) in both strains but did not affect cross-sectional bone area, cortical thickness, nor cortical tissue mineral density (μCT). Furthermore, the effect of diet on yield moment was independent of the structural resistance of the femur mid-diaphysis suggesting a negative effect of HFD on characteristics of the bone matrix. However, neither Raman spectroscopy nor assays of advanced glycation end-products identified how HFD affected the matrix. HFD also lowered the resistance of cortical bone to crack growth in only the diabetic NZO10 mice (fracture toughness testing of other femur), while HFD reduced the ultimate force of the L6 vertebra in both strains (compression testing). In conclusion, the HFD-related decrease in bone strength can occur in mice resistant and prone to diabetes indicating that a diet high in fat deleteriously affects bone without necessarily causing hyperglycemia.

Bone mineral density T-scores comparison between obese and non-obese individuals included in a Fracture Liaison Service following a recent fragility fracture

We used data from a Fracture Liaison Service to compare the mean T-scores of obese and non-obese patients after a recent fragility fracture. After adjusting for age, sex, and diabetes mellitus, T-score values were significantly higher at all measurement sites in obese patients, with a mean difference of 1 SD.

PURPOSE

This study aimed to compare the mean T-scores of obese and non-obese patients after recent fragility fractures.

METHODS

Over a period of 5 and a half years, from January 2016 to May 2021, patients from a fracture liaison service were identified and their demographic characteristics, osteoporosis risk factors, BMD T-scores, and fracture sites were compared between obese (BMI ≥ 30 kg/m2) and non-obese (19 kg/m2 < BMI < 30 kg/m2) patients.

RESULTS

A total of 712 patients were included (80.1% women; mean age 73.8 ± 11.3 years). Sixteen % had type 2 diabetes mellitus and 80% had a major osteoporotic fracture (MOF). 135 patients were obese and 577 non-obese, with obese patients younger (p < 0.001) and more frequently female (p = 0.03). Obese patients presented with fewer hip fractures (10% vs. 21%, p = 0.003) and more proximal humerus fractures (16% vs. 7%, p < 0.001) than non-obese patients. After adjusting for age, sex, and diabetes mellitus, BMD T-score values were significantly higher at all measurement sites (lumbar spine, total hip, and femoral neck) in obese patients than in non-obese patients for all types of fractures, with a mean difference of 1 standard deviation (p < 0.001 for all comparisons). The same results were observed in the population limited to MOF.

CONCLUSIONS

Given the crucial role of BMD T-score in determining the need for anti-osteoporotic medication following fragility fractures, it is reasonable to question the existing T-score thresholds in obese patients.

Usefulness of fat-containing agents: an initial study on estimating fat content for magnetic resonance imaging

This initial study aimed at testing whether fat-containing agents can be used for the fat mass estimation methods using magnetic resonance imaging (MRI). As an example for clinical application, fat-containing agents (based on soybean oil, 10% and 20%), 100% soybean oil, and saline as reference substances were placed outside the proximal femurs obtained from 14 participants and analyzed by 0.3 T MRI. Fat content was the estimated fat fraction (FF) based on signal intensity (SIeFF, %). The SIeFF values of the femoral bone marrow, including the femoral head, neck, shaft, and trochanter area, were measured. MRI data were compared in terms of bone mineral content (BMC) and bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) in the proximal femur. Twelve pig femurs were also used to confirm the correlation between FF by the DIXON method and SIeFF. According to Pearson's correlation coefficient, the SIeFF and total BMC and BMD data revealed strong and moderate negative correlations in the femoral head (r <  - 0.74) and other sites (r =  - 0.66 to - 0.45). FF and SIeFF showed a strong correlation (r = 0.96). This study was an initial investigation of a method for estimating fat mass with fat-containing agents and showed the potential for use in MRI. SIeFF and FF showed a strong correlation, and SIeFF and BMD and BMC showed correlation; however, further studies are needed to use SIeFF as a substitute for DXA.

Iron accumulation induced by hepcidin1 knockout accelerates the progression of aging osteoporosis

OBJECTIVE

Iron accumulation is associated with osteoporosis. This study aims to explore the effect of chronic iron accumulation induced by hepcidin1 deficiency on aging osteoporosis.

METHODS

Iron accumulation in hepcidin1 knockout aging mice was assessed by atomic absorption spectroscopy and Perl's staining. Bone microarchitecture was observed using Micro-CT. Hepcidin, ferritin, oxidative stress, and markers of bone turnover in serum were detected by enzyme-linked immunosorbent assay. Bone formation and resorption markers were measured by real-time quantitative PCR. Cell aging was induced by D-galactose treatment. CCK-8, flow cytometry, EdU assays, and Alizarin red staining were performed to reveal the role of hepcidin1 knockout in cell model. Iron Colorimetric Assay Kit and western blot were applied to detect iron and ferritin levels in cells, respectively.

RESULTS

In hepcidin1-knockout mice, the ferritin and iron contents in liver and tibia were significantly increased. Iron accumulation induced by hepcidin1 knockout caused a phenotype of low bone mass and deteriorated bone microarchitecture. Osteogenic marker was decreased and osteoclast marker was increased in mice, accompanied by increased oxidative stress level. The mRNA expression levels of osteoclast differentiation markers (RANKL, Mmp9, OPG, Trap, and CTSK) were up-regulated, while bone formation markers (OCN, ALP, Runx2, SP7, and Col-1) were down-regulated in model group, compared to wild type mice. In vitro, hepcidin1 knockdown inhibited proliferation and osteogenic differentiation, while promoted apoptosis, with increased levels of iron and ferritin.

CONCLUSION

Iron accumulation induced by hepcidin1 deficiency aggravates the progression of aging osteoporosis via inhibiting osteogenesis and promoting osteoclast genesis.

Mouse models of accelerated aging in musculoskeletal research for assessing frailty, sarcopenia, and osteoporosis - A review

Musculoskeletal aging encompasses the decline in bone and muscle function, leading to conditions such as frailty, osteoporosis, and sarcopenia. Unraveling the underlying molecular mechanisms and developing effective treatments are crucial for improving the quality of life for those affected. In this context, accelerated aging models offer valuable insights into these conditions by displaying the hallmarks of human aging. Herein, this review focuses on relevant mouse models of musculoskeletal aging with particular emphasis on frailty, osteoporosis, and sarcopenia. Among the discussed models, PolgA mice in particular exhibit hallmarks of musculoskeletal aging, presenting early-onset frailty, as well as reduced bone and muscle mass that closely resemble human musculoskeletal aging. Ultimately, findings from these models hold promise for advancing interventions targeted at age-related musculoskeletal disorders, effectively addressing the challenges posed by musculoskeletal aging and associated conditions in humans.

Relationship between bone marrow adipose tissue and kidney function in postmenopausal women

Introduction

Bone marrow adipose tissue (BMAT) is associated with aging, osteoporosis, and chronic kidney disease (CKD). To date, the association between BMAT and kidney function in postmenopausal women has not been thoroughly investigated. The main purpose of this study was to determine whether a relationship exists between proton density fat fraction (PDFF) and kidney function in postmenopausal women.

Methods

We investigated the cross-sectional association between estimated glomerular filtration rate (eGFR) - calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation - and PDFF - measured at the lumbar spine and proximal femur using Water Fat Imaging (WFI) MRI - in 199 postmenopausal women from the ADIMOS cohort study. We also performed DXA scans and laboratory measurements of sclerostin and c-terminal Fibroblast Growth Factor 23 (cFGF23).

Results

Participants' mean age was 67.5 (standard deviation, SD 10.0) years. Their median eGFR was 85.0 (interquartile range, IQR 72.2-95.0) ml/min/1.73 cm2, and their mean lumbar spine PDFF was 57.9 % (SD 9.6). When classified by eGFR-based CKD stages, 41.7 % of the cohort had an eGFR ≥ 90 (n = 83), 47.2 % had an eGFR of 60-89.9 (n = 94), and 11.1 % had an eGFR of 30-59.9 (n = 22). Participants with eGFR ≥ 90 had a lower lumbar spine PDFF than those with eGFR 60-89.9 (mean 55.8 % (9.8) vs. 58.9 % (9.0), p = 0.031) and those with eGFR 30-59.9 (55.8 % (9.8) vs. 60.8 % (9.8), p = 0.043). However, the differences did not remain significant after adjusting for predetermined confounders, including age, diabetes, Charlson comorbidity index, recent history of fragility fracture, appendicular lean mass, and lumbar spine BMD. The inclusion of sclerostin and/or cFGF23 as suspected mediators did not alter the findings. When proximal hip imaging-based PDFF was considered, no significant differences were found between the eGFR categories in the unadjusted and adjusted analyses.

Conclusion

No evidence of an association between kidney function and bone marrow adiposity was found either in the lumbar spine or proximal femur in a cohort of postmenopausal women.

The Impact of Interventional Weight Loss on Bone Marrow Adipose Tissue in People Living with Obesity and Its Connection to Bone Metabolism

This review focuses on providing physicians with insights into the complex relationship between bone marrow adipose tissue (BMAT) and bone health, in the context of weight loss through caloric restriction or metabolic and bariatric surgery (MBS), in people living with obesity (PwO). We summarize the complex relationship between BMAT and bone health, provide an overview of noninvasive imaging techniques to quantify human BMAT, and discuss clinical studies measuring BMAT in PwO before and after weight loss. The relationship between BMAT and bone is subject to variations based on factors such as age, sex, menopausal status, skeletal sites, nutritional status, and metabolic conditions. The Bone Marrow Adiposity Society (BMAS) recommends standardizing imaging protocols to increase comparability across studies and sites, they have identified both water-fat imaging (WFI) and spectroscopy (1H-MRS) as accepted standards for in vivo quantification of BMAT. Clinical studies measuring BMAT in PwO are limited and have shown contradictory results. However, BMAT tends to be higher in patients with the highest visceral adiposity, and inverse associations between BMAT and bone mineral density (BMD) have been consistently found in PwO. Furthermore, BMAT levels tend to decrease after caloric restriction-induced weight loss. Although weight loss was associated with overall fat loss, a reduction in BMAT did not always follow the changes in fat volume in other tissues. The effects of MBS on BMAT are not consistent among the studies, which is at least partly related to the differences in the study population, skeletal site, and duration of the follow-up. Overall, gastric bypass appears to decrease BMAT, particularly in patients with diabetes and postmenopausal women, whereas sleeve gastrectomy appears to increase BMAT. More research is necessary to evaluate changes in BMAT and its connection to bone metabolism, either in PwO or in cases of weight loss through caloric restriction or MBS, to better understand the role of BMAT in this context and determine the local or systemic factors involved.

Cellular senescence in skeletal disease: mechanisms and treatment

The musculoskeletal system supports the movement of the entire body and provides blood production while acting as an endocrine organ. With aging, the balance of bone homeostasis is disrupted, leading to bone loss and degenerative diseases, such as osteoporosis, osteoarthritis, and intervertebral disc degeneration. Skeletal diseases have a profound impact on the motor and cognitive abilities of the elderly, thus creating a major challenge for both global health and the economy. Cellular senescence is caused by various genotoxic stressors and results in permanent cell cycle arrest, which is considered to be the underlying mechanism of aging. During aging, senescent cells (SnCs) tend to aggregate in the bone and trigger chronic inflammation by releasing senescence-associated secretory phenotypic factors. Multiple signalling pathways are involved in regulating cellular senescence in bone and bone marrow microenvironments. Targeted SnCs alleviate age-related degenerative diseases. However, the association between senescence and age-related diseases remains unclear. This review summarises the fundamental role of senescence in age-related skeletal diseases, highlights the signalling pathways that mediate senescence, and discusses potential therapeutic strategies for targeting SnCs.

Bone Marrow Adiposity and Fragility Fractures in Postmenopausal Women: The ADIMOS Case-Control Study

CONTEXT

Noninvasive assessment of proton density fat fraction (PDFF) by magnetic resonance imaging (MRI) may improve the prediction of fractures.

OBJECTIVE

This work aimed to determine if an association exists between PDFF and fractures.

METHODS

A case-control study was conducted at Lille University Hospital, Lille, France, with 2 groups of postmenopausal women: one with recent osteoporotic fractures, and the other with no fractures. Lumbar spine and proximal femur (femoral head, neck, and diaphysis) PDFF were determined using chemical shift-based water-fat separation MRI (WFI) and dual-energy x-ray absorptiometry scans of the lumbar spine and hip. Our primary objective was to determine the relationship between lumbar spine PDFF and osteoporotic fractures in postmenopausal women. Analysis of covariance was used to compare PDFF measurements between patient cases (overall and according to the type of fracture) and controls, after adjusting for age, Charlson comorbidity index (CCI) and BMD.

RESULTS

In 199 participants, controls (n = 99) were significantly younger (P < .001) and had significantly higher BMD (P < 0.001 for all sites) than patient cases (n = 100). A total of 52 women with clinical vertebral fractures and 48 with nonvertebral fractures were included. When PDFFs in patient cases and controls were compared, after adjustment on age, CCI, and BMD, no statistically significant differences between the groups were found at the lumbar spine or proximal femur. When PDFFs in participants with clinical vertebral fractures (n = 52) and controls were compared, femoral neck PDFF and femoral diaphysis PDFF were detected to be lower in participants with clinical vertebral fractures than in controls (adjusted mean [SE] 79.3% [1.2] vs 83.0% [0.8]; P = 0.020, and 77.7% [1.4] vs 81.6% [0.9]; P = 0.029, respectively).

CONCLUSION

No difference in lumbar spine PDFF was found between those with osteoporotic fractures and controls. However, imaging-based proximal femur PDFF may discriminate between postmenopausal women with and without clinical vertebral fractures, independently of age, CCI, and BMD.

Bone marrow adiposity modulation after long duration spaceflight in astronauts

Space travel requires metabolic adaptations from multiple systems. While vital to bone and blood production, human bone marrow adipose (BMA) tissue modulation in space is unknown. Here we show significant downregulation of the lumbar vertebrae BMA in 14 astronauts, 41 days after landing from six months' missions on the International Space Station. Spectral analyses indicated depletion of marrow adipose reserves. We then demonstrate enhanced erythropoiesis temporally related to low BMA. Next, we demonstrated systemic and then, local lumbar vertebrae bone anabolism temporally related to low BMA. These support the hypothesis that BMA is a preferential local energy source supplying the hypermetabolic bone marrow postflight, leading to its downregulation. A late postflight upregulation abolished the lower BMA of female astronauts and BMA modulation amplitude was higher in younger astronauts. The study design in the extreme environment of space can limit these conclusions. BMA modulation in astronauts can help explain observations on Earth.

Bone in Anorexia

Anorexia nervosa is a feeding disorder involving intentional weight loss. Restricted dietary intake leads to disturbed bone metabolism due to various factors, notably endocrine, that affect bone microarchitecture and incur risk of fracture. Mild to moderate anorexia shows a paradoxical increase in bone marrow adipose tissue, whereas severe forms show gelatinous transformation known as serous atrophy of bone marrow (SABM). Imaging assessment of the mineralized and adipose components uses several techniques: dual-energy X-ray absorptiometry, computed tomography, chemical shift magnetic resonance imaging (MRI), and single-voxel MR spectroscopy. SABM induces MRI bone signal disturbances that can be hard to interpret and may hinder visualization of the fracture line.

Myosteatosis and bone marrow adiposity are not associated among postmenopausal women with fragility fractures

Objectives

Although paravertebral intramuscular fatty infiltration (known as myosteatosis) following a vertebral fracture is well-known, scarce data are available regarding interactions between muscle, bone, and other fat depots. Based on a homogeneous cohort comprising postmenopausal women with or without a history of fragility fracture, we aimed to better depict the interrelationship between myosteatosis and bone marrow adiposity (BMA).

Methods

102 postmenopausal women were included, 56 of whom had a fragility fracture. Mean proton density fat fraction (PDFF) was measured in the psoas (PDFF_Psoas) and paravertebral (PDFF_{Paravertebral}) muscles at the lumbar level, as well as in the lumbar spine and non-dominant hip using chemical shift encoding-based water-fat imaging. Visceral adipose tissue (VAT) and total body fat (TBF) were assessed using dual X-ray absorptiometry. Statistical models were adjusted for age, weight, height (all comparisons), and bone mineral density (when considering BMA).

Results

PDFF in the psoas and paravertebral muscles was higher in the fracture group compared to controls even after adjustment for age, weight, and height (PDFF_Psoas = 17.1 ± 6.1% versus 13.5 ± 4.9%, p=0.004; PDFF_{Paravertebral} = 34.4 ± 13.6% versus 24.9 ± 8.8%, p=0.002). Higher PDFF_{Paravertebral} was associated with lower PDFF at the lumbar spine (β = -6.80 ± 2.85, p=0.022) among controls but not in the fracture group. In both groups, a significant relationship between higher PDFF_Psoas and higher VAT was observed (β = 20.27 ± 9.62, p=0.040 in the fracture group, and β = 37.49 ± 8.65, p<0.001 in the control group). Although solely observed among controls, a similar relationship was observed between PDFF_{Paravertebral} and TBF (β = 6.57 ± 1.80, p<0.001). No significant association was observed between BMA and other fat depots.

Conclusion

Myosteatosis is not associated with BMA among postmenopausal women with fragility fractures. Whereas myosteatosis was associated with other fat depots, BMA appears uniquely regulated.

Alterations in the microenvironment and the effects produced of TRPV5 in osteoporosis

The pathogenesis of osteoporosis involves multiple factors, among which alterations in the bone microenvironment play a crucial role in disrupting normal bone metabolic balance. Transient receptor potential vanilloid 5 (TRPV5), a member of the TRPV family, is an essential determinant of the bone microenvironment, acting at multiple levels to influence its properties. TRPV5 exerts a pivotal influence on bone through the regulation of calcium reabsorption and transportation while also responding to steroid hormones and agonists. Although the metabolic consequences of osteoporosis, such as loss of bone calcium, reduced mineralization capacity, and active osteoclasts, have received significant attention, this review focuses on the changes in the osteoporotic microenvironment and the specific effects of TRPV5 at various levels.

Downregulation of the RNA-binding protein PUM2 facilitates MSC-driven bone regeneration and prevents OVX-induced bone loss

BACKGROUND

Although mRNA dysregulation can induce changes in mesenchymal stem cell (MSC) homeostasis, the mechanisms by which post-transcriptional regulation influences MSC differentiation potential remain understudied. PUMILIO2 (PUM2) represses translation by binding target mRNAs in a sequence-specific manner.

METHODS

In vitro osteogenic differentiation assays were conducted using human bone marrow-derived MSCs. Alkaline phosphatase and alizarin red S staining were used to evaluate the osteogenic potential of MSCs. A rat xenograft model featuring a calvarial defect to examine effects of MSC-driven bone regeneration. RNA-immunoprecipitation (RNA-IP) assay was used to determine the interaction between PUM2 protein and Distal-Less Homeobox 5 (DLX5) mRNA. Ovariectomized (OVX) mice were employed to evaluate the effect of gene therapy for postmenopausal osteoporosis.

RESULTS

Here, we elucidated the molecular mechanism of PUM2 in MSC osteogenesis and evaluated the applicability of PUM2 knockdown (KD) as a potential cell-based or gene therapy. PUM2 level was downregulated during MSC osteogenic differentiation, and PUM2 KD enhanced MSC osteogenic potential. Following PUM2 KD, MSCs were transplanted onto calvarial defects in 12-week-old rats; after 8 weeks, transplanted MSCs promoted bone regeneration. PUM2 KD upregulated the expression of DLX5 mRNA and protein and the reporter activity of its 3'-untranslated region. RNA-IP revealed direct binding of PUM2 to DLX5 mRNA. We then evaluated the potential of adeno-associated virus serotype 9 (AAV9)-siPum2 as a gene therapy for osteoporosis in OVX mice.

CONCLUSION

Our findings suggest a novel role for PUM2 in MSC osteogenesis and highlight the potential of PUM2 KD-MSCs in bone regeneration. Additionally, we showed that AAV9-siPum2 is a potential gene therapy for osteoporosis.

Vertebrae but not femur marrow fat transiently decreases in response to body weight loss in an 18-month randomized control trial

BACKGROUND

Increased levels of bone marrow adipose tissue (BMAT) are negatively associated with skeletal health and hematopoiesis. BMAT is known to increase with age; however, the effect of long-term weight loss on BMAT is still unknown.

OBJECTIVE

In this study, we examined BMAT response to lifestyle-induced weight loss in 138 participants (mean age 48 y; mean body mass index 31 kg/m²), who participated in the CENTRAL-MRI trial.

METHODS

Participants were randomized for dietary intervention of low-fat or low-carb, with or without physical activity. Magnetic resonance imaging (MRI) was used to quantify BMAT and other fat depots at baseline, six and eighteen months of intervention. Blood biomarkers were also measured at the same time points.

RESULTS

At baseline, the L3 vertebrae BMAT is positively associated with age, HDL cholesterol, HbA1c and adiponectin; but not with other fat depots or other metabolic markers tested. Following six months of dietary intervention, the L3 BMAT declined by an average of 3.1 %, followed by a return to baseline after eighteen months (p < 0.001 and p = 0.189 compared to baseline, respectively). The decrease of BMAT during the first six months was associated with a decrease in waist circumference, cholesterol, proximal-femur BMAT, and superficial subcutaneous adipose tissue (SAT), as well as with younger age. Nevertheless, BMAT changes did not correlate with changes in other fat depots.

CONCLUSIONS

We conclude that physiological weight loss can transiently reduce BMAT in adults, and this effect is more prominent in younger adults. Our findings suggest that BMAT storage and dynamics are largely independent of other fat depots or cardio-metabolic risk markers, highlighting its unique functions.

Osteoporosis and Bone Marrow Adipose Tissue

PURPOSE OF REVIEW

This review focuses on the recent findings regarding bone marrow adipose tissue (BMAT) concerning bone health. We summarize the variations in BMAT in relation to age, sex, and skeletal sites, and provide an update on noninvasive imaging techniques to quantify human BMAT. Next, we discuss the role of BMAT in patients with osteoporosis and interventions that affect BMAT.

RECENT FINDINGS

There are wide individual variations with region-specific fluctuation and age- and gender-specific differences in BMAT content and composition. The Bone Marrow Adiposity Society (BMAS) recommendations aim to standardize imaging protocols to increase comparability across studies and sites. Water-fat imaging (WFI) seems an accurate and efficient alternative for spectroscopy (¹H-MRS). Most studies indicate that greater BMAT is associated with lower bone mineral density (BMD) and a higher prevalence of vertebral fractures. The proton density fat fraction (PDFF) and changes in lipid composition have been associated with an increased risk of fractures independently of BMD. Therefore, PDFF and lipid composition could potentially be future imaging biomarkers for assessing fracture risk. Evidence of the inhibitory effect of osteoporosis treatments on BMAT is still limited to a few randomized controlled trials. Moreover, results from the FRAME biopsy sub-study highlight contradictory findings on the effect of the sclerostin antibody romosozumab on BMAT. Further understanding of the role(s) of BMAT will provide insight into the pathogenesis of osteoporosis and may lead to targeted preventive and therapeutic strategies.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

Bone Cells Metabolic Changes Induced by Ageing

Bone is a living organ that exhibits active metabolic processes, presenting constant bone formation and resorption. The bone cells that maintain local homeostasis are osteoblasts, osteoclasts, osteocytes and bone marrow stem cells, their progenitor cells. Osteoblasts are the main cells that govern bone formation, osteoclasts are involved in bone resorption, and osteocytes, the most abundant bone cells, also participate in bone remodeling. All these cells have active metabolic activities, are interconnected and influence each other, having both autocrine and paracrine effects. Ageing is associated with multiple and complex bone metabolic changes, some of which are currently incompletely elucidated. Ageing causes important functional changes in bone metabolism, influencing all resident cells, including the mineralization process of the extracellular matrix. With advancing age, a decrease in bone mass, the appearance of specific changes in the local microarchitecture, a reduction in mineralized components and in load-bearing capacity, as well as the appearance of an abnormal response to different humoral molecules have been observed. The present review points out the most important data regarding the formation, activation, functioning, and interconnection of these bone cells, as well as data on the metabolic changes that occur due to ageing.

Libanoridin Isolated from Corydalis heterocarpa Inhibits Adipogenic Differentiation of Bone Marrow-Derived Mesenchymal Stromal Cells

Bone marrow adiposity is a complication in osteoporotic patients. It is a result of the imbalance between adipogenic and osteogenic differentiation of bone marrow cells. Phytochemicals can alleviate osteoporotic complications by hindering bone loss and decreasing bone marrow adiposity. Corydalis heterocarpa is a biennial halophyte with reported bioactivities, and it is a source of different coumarin derivatives. Libanoridin is a coumarin isolated from C. heterocarpa, and the effect of libanoridin on adipogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBM-MSCs) was evaluated in the present study. Cells were induced to undergo adipogenesis, and their intracellular lipid accumulation and expression of adipogenic markers were observed under libanoridin treatment. Results showed that 10 μM libanoridin-treated adipocytes accumulated 44.94% less lipid compared to untreated adipocytes. In addition, mRNA levels of PPARγ, C/EBPα, and SREBP1c were dose-dependently suppressed with libanoridin treatment, whereas only protein levels of PPARγ were decreased in the presence of libanoridin. Fluorescence staining of adipocytes also revealed that cells treated with 10 μM libanoridin expressed less PPARγ compared to untreated adipocytes. Protein levels of perilipin and leptin, markers of mature adipocytes, were also suppressed in adipocytes treated with 10 μM libanoridin. Analysis of MAPK phosphorylation levels showed that treatment with libanoridin inhibited the activation of p38 and JNK MAPKs observed by decreased levels of phosphorylated p38 and JNK protein. It was suggested that libanoridin inhibited adipogenic differentiation of hBM-MSCs via suppressing MAPK-mediated PPARγ signaling. Future studies revealing the anti-adipogenic effects of libanoridin in vivo and elucidating its action mechanism will pave the way for libanoridin to be utilized as a nutraceutical with anti-osteoporotic properties.

Exercise Promotes Bone Marrow Microenvironment by Inhibiting Adipsin in Diet-Induced Male Obese Mice

Obesity is a growing global epidemic linked to many diseases, including diabetes, cardiovascular diseases, and musculoskeletal disorders. Exercise can improve bone density and decrease excess bone marrow adipose tissue (BMAT) in obese individuals. However, the mechanism of exercise regulating bone marrow microenvironment remains unclear. This study examines how exercise induces bone marrow remodeling in diet-induced obesity. We employed unbiased RNA-Seq to investigate the effect of exercise on the bone marrow of diet-induced obese male mice. Bone mesenchymal stem cells (BMSCs) were isolated to explore the regulatory effects of exercise in vitro. Our data demonstrated that exercise could slow down the progression of obesity and improve trabecular bone density. RNA-seq data revealed that exercise inhibited secreted phosphoprotein 1 (Spp1), which was shown to mediate bone resorption through mechanosensing mechanisms. Interactome analysis of Spp1 using the HINT database showed that Spp1 interacted with the adipokine adipsin. Moreover, exercise decreased BMAT, which induced osteoclast differentiation and promoted bone loss. Our study reveals that exercise improves the bone marrow microenvironment by at least partially inhibiting the adipsin-Spp1 signaling pathway so as to inhibit the alternative complement system from activating osteoclasts in diet-induced obese mice.

Dietary Saturated Fat and Bone Health in Young Adults: The Young Finns Cohort

Previous studies suggest that saturated fat (SFA) intake may negatively impact on bone. However, few human studies on the topic exist. Women and men aged 31-46 years from the Cardiovascular Risk in Young Finns study attended the peripheral quantitative computed tomography and ultrasound bone measurements in 2008 (n = 1884-1953, ~ 56% women). In addition, fracture diagnoses in 1980-2018 were searched for the national health care registers and 431 participants had at least one fracture. Food consumption was gathered with the 48-h dietary recall interviews and food frequency questionnaire in 1980-2007. In the present study, radial, tibial, and calcaneal bone traits, and fractures were examined relative to the long-term intake of SFA. No consistent associations were seen between bone outcomes and SFA intake that would have replicated in both women and men. The only evidence for differential distributions was seen in cortical density and cortical-to-total area ratio at the radial shaft, and speed of sound at the calcaneus, which were 0.1-0.4% higher in women in the lowest tertile of SFA intake compared with the highest tertile. In addition, among men, the odds ratio (OR) of fractures was greater in the second (OR 1.86, 95% confidence interval (CI) 1.03-3.33) and third tertile of SFA intake (OR 2.45, 95% CI 1.38-4.36) compared with the lowest tertile, independently of many risk factors of osteoporosis. In this observational study, we found no robust evidence of the associations of dietary long-term SFA intake with bone outcomes. Therefore, additional studies are needed to confirm the association of dietary SFA with bone health in humans.

Associations of Texture Features of Proton Density Fat Fraction Maps between Lumbar Vertebral Bone Marrow and Paraspinal Musculature

Chemical shift encoding-based water−fat MRI (CSE-MRI)-derived proton density fat fraction (PDFF) has been used for non-invasive assessment of regional body fat distributions. More recently, texture analysis (TA) has been proposed to reveal even more detailed information about the vertebral or muscular composition beyond PDFF. The aim of this study was to investigate associations between vertebral bone marrow and paraspinal muscle texture features derived from CSE-MRI-based PDFF maps in a cohort of healthy subjects. In this study, 44 healthy subjects (13 males, 55 ± 30 years; 31 females, 39 ± 17 years) underwent 3T MRI including a six-echo three-dimensional (3D) spoiled gradient echo sequence used for CSE-MRI at the lumbar spine and the paraspinal musculature. The erector spinae muscles (ES), the psoas muscles (PS), and the vertebral bodies L1-4 (LS) were manually segmented. Mean PDFF values and texture features were extracted for each compartment. Features were compared between males and females using logistic regression analysis adjusted for age and body mass index (BMI). All texture features of ES except for Sum Average were significantly (p < 0.05) different between men and women. The three global texture features (Variance, Skewness, Kurtosis) for PS as well as LS showed a significant difference between male and female subjects (p < 0.05). Mean PDFF measured in PS and ES was significantly higher in females, but no difference was found for the vertebral bone marrow’s PDFF. Partial correlation analysis between the texture features of the spine and the paraspinal muscles revealed a highly significant correlation for Variance(global) (r = 0.61 for ES, r = 0.62 for PS; p < 0.001 respectively). Texture analysis using PDFF maps based on CSE-MRI revealed differences between healthy male and female subjects. Global texture features in the lumbar vertebral bone marrow allowed for differentiation between men and women, when the overall PDFF was not significantly different, indicating that PDFF maps may contain detailed and subtle textural information beyond fat fraction. The observed significant correlation of Variance(global) suggests a metabolic interrelationship between vertebral bone marrow and the paraspinal muscles.

3T-MRI-based age, sex and site-specific markers of musculoskeletal health in healthy children and young adults

Objective

The aim of this study is to investigate the role of 3T-MRI in assessing musculoskeletal health in children and young people.

Design

Bone, muscle and bone marrow imaging was performed in 161 healthy participants with a median age of 15.0 years (range, 8.0, 30.0).

Methods

Detailed assessment of bone microarchitecture (constructive interference in the steady state (CISS) sequence, voxel size 0.2 × 0.2 × 0.4 mm3), bone geometry (T1-weighted turbo spin echo (TSE) sequence, voxel size 0.4 × 0.4 × 2 mm3) and bone marrow (1H-MRS, point resolved spectroscopy sequence (PRESS) (single voxel size 20 × 20 × 20 mm3) size and muscle adiposity (Dixon, voxel size 1.1 × 1.1 × 2 mm3).

Results

There was an inverse association of apparent bone volume/total volume (appBV/TV) with age (r = -0.5, P < 0.0005). Cortical area, endosteal and periosteal circumferences and muscle cross-sectional area showed a positive association to age (r > 0.49, P < 0.0001). In those over 17 years of age, these parameters were also higher in males than females (P < 0.05). This sex difference was also evident for appBV/TV and bone marrow adiposity (BMA) in the older participants (P < 0.05). AppBV/TV showed a negative correlation with BMA (r = -0.22, P = 0.01) which also showed an association with muscle adiposity (r = 0.24, P = 0.04). Cortical geometric parameters were highly correlated with muscle area (r > 0.57, P < 0.01).

Conclusions

In addition to providing deep insight into the normal relationships between bone, fat and muscle in young people, these novel data emphasize the role of MRI as a non-invasive method for performing a comprehensive and integrated assessment of musculoskeletal health in the growing skeleton.

Determination of Sr2+ mobility in viscous bovine bone marrow by cryo-time-of-flight secondary ion mass spectrometry

RATIONALE

In osteoporosis research, strontium ions (Sr²⁺ ) have emerged as promising therapeutic agent in modified bone cements for better fracture healing. Modeling of Sr²⁺ dispersion in bone could be used as a predictive tool for the evaluation of functionalized biomaterials in future. Therefore, determination of experimental parameters for Sr²⁺ transport in bone is essential. In this study, we focus on the determination of Sr²⁺ diffusion in viscous bovine bone marrow by time-of-flight secondary ion mass spectrometry (ToF-SIMS).

METHODS

For this comparatively fast diffusion (FD) experiment, a specific experimental protocol of ToF-SIMS depth profiling under cryogenic conditions was developed. The validity of our experimental approach is proven by a time-dependent experimental series. Furthermore, 2D and 3D mass spectrometric imaging analysis was used to study Sr²⁺ surface and bulk distribution within bovine bone marrow.

RESULTS

Detailed 2D and 3D mass spectrometric imaging analysis revealed that Sr²⁺ diffusion is slower in bone marrow areas with high intensity of lipid and fatty acid signals than in areas with less lipid content. The Sr²⁺ transport within this passive model can be described by Fickian diffusion. Average diffusion coefficients of Sr²⁺ in bovine bone marrow were obtained from diffusion profiles in FD areas (D_bovine,FD  = [2.09 ± 2.39]·10^-9 cm² s^-1 ), slow diffusion areas (D_bovine,SD  = [1.52 ± 1.80]·10^-10 cm² s^-1 ), and total area diffusion (D_bovine,TA  = [1.94 ± 2.40]·10^-9 cm² s^-1 ).

CONCLUSIONS

We were able to show that cryo-ToF-SIMS is a useful tool for the characterization of rapid diffusion in water-containing highly viscous media. To the best of our knowledge, this is the first reported experimental approach for the investigation of the distribution of low concentrated therapeutic agents in bone marrow. Overall, our results provide important insights about Sr²⁺ diffusion in bovine bone marrow.

Bariatric Surgery and Osteoporosis

It has been increasingly acknowledged that bariatric surgery adversely affects skeletal health. After bariatric surgery, the extent of high-turnover bone loss is much greater than what would be expected in the absence of a severe skeletal insult. Patients also experience a significant deterioration in bone microarchitecture and strength. There is now a growing body of evidence that suggests an association between bariatric surgery and higher fracture risk. Although the mechanisms underlying the high-turnover bone loss and increase in fracture risk after bariatric surgery are not fully understood, many factors seem to be involved. The usual suspects are nutritional factors and mechanical unloading, and the roles of gut hormones, adipokines, and bone marrow adiposity should be investigated further. Roux-en-Y gastric bypass (RYGB) was once the most commonly performed bariatric procedure worldwide, but sleeve gastrectomy (SG) has now become the predominant bariatric procedure. Accumulating evidence suggests that RYGB is associated with a greater reduction in BMD, a greater increase in markers of bone turnover, and a higher risk of fracture than SG. These findings should be taken into consideration in determining the most appropriate bariatric procedure for patients, especially those at higher fracture risk. Before and after all bariatric procedures, sufficient calcium, vitamin D and protein intake, and adequate physical activity, are needed to counteract negative impacts on bone. There are no studies to date that have evaluated the effect of osteoporosis treatment on high-turnover bone loss after bariatric surgery. However, in patients with a diagnosis of osteoporosis, anti-resorptive agents may be considered.

The Diagnostic Value of the Osteoporosis Self-assessment Tool for Asians in Vietnamese Postmenopausal Women

Introduction: Osteoporosis is a common disease that affects many women in the postmenopausal period. Dual-energy X-ray absorptiometry (DXA) is a simple and noninvasive method used to diagnose osteoporosis. The Osteoporosis Self-Assessment Tool for Asians (OSTA) is an osteoporosis risk assessment toolkit, used for menopausal women in Asia. This study aimed to evaluate the diagnostic values of the OSTA index in determining the risk of osteoporosis in postmenopausal women. Material and Methods:  This cross-sectional study was conducted on 919 postmenopausal women to determine the value of OSTA in osteoporosis risk assessment. The bone density was measured using the DXA method in the lumbar spine and femoral neck. Results: Based on the ROC curve, the sensitivity and specitivity of OSTA were 70.3% and 63.6% at the cut-off of ≤ -1.4 at the femoral neck or lumber spine or both (p = 0.005) . At a cut-off point of ≤-1 at one of two position or both, the OSTA index showed a specificity of 87.23%, sensitivity of 66.08%, positive predictive value of 46.90%, and negative predictive value of 93.78% in predicting the osteoporosis risk. Conclusions: The OSTA index is a simple tool that is highly sensitive and specific in predicting the risk of osteoporosis in postmenopausal women.

Characterisation of Sr2+ mobility in osteoporotic rat bone marrow by cryo-ToF-SIMS and cryo-OrbiSIMS

Mass spectrometric imaging approach for ex vivo monitoring of drug transport in bone sections. Cryo-ToF-SIMS depth profiling and high-resolution imaging as well as OrbiSIMS analysis revealed inhomogeneous Sr2+ transport in rat bone marrow.

Stimulatory Effect of Tofacitinib on Bone Marrow Adipocytes Differentiation

BACKGROUND

Systemic inflammation is the main factor underlying secondary osteoporosis in patients with rheumatoid arthritis (RA). Janus kinase inhibitors (JAKi), such as tofacitinib (Tofa), can control systemic inflammation and may have beneficial effects on bone in various models. This might be due to direct effects on the bone microenvironment and not exclusively based on their anti-inflammatory function. Bone marrow adipocytes (BMAds) are abundant in the bone microenvironment. The effect of JAKi on BMAds is unknown, but evidence suggests that there is competition between human bone marrow-derived stromal cell (hBMSC) differentiation routes towards BMAds and osteoblasts (Ob) in osteoporosis.

OBJECTIVES

The aims of the study are to determine whether Tofa influences BMAds and Ob derived from hBMSCs and to investigate the potential effects of Tofa on bone marrow adiposity in RA patients.

METHODS

To determine the effect of Tofa on cellular commitment, hBMSCs were differentiated to BMAds or OBs for 3 days together with Tofa at 200, 400, or 800 nM and TNFα. This study was also conducted using differentiated BMAds. The impact of Tofa was determined by gene and protein expression analysis and cell density monitoring. In parallel, in a pilot study of 9 RA patients treated with Tofa 5 mg twice a day (NCT04175886), the proton density fat fraction (PDFF) was measured using MRI at the lumbar spine at baseline and at 6 months.

RESULTS

In non-inflammatory conditions, the gene expression of Runx2 and Dlx5 decreased in Ob treated with Tofa (p <0.05). The gene expression of PPARγ2, C/EBPα, and Perilipin 1 were increased compared to controls (p <0.05) in BMAds treated with Tofa. Under inflammatory conditions, Tofa did not change the expression profiles of Ob compared to TNFα controls. In contrast, Tofa limited the negative effect of TNFα on BMAd differentiation (p <0.05). An increase in the density of differentiated BMAds treated with Tofa under TNFα was noted (p <0.001). These findings were consolidated by an increase in PDFF at 6 months of treatment with Tofa in RA patients (46.3 ± 7.0% versus 53.2 ± 9.2% p <0.01).

CONCLUSION

Together, these results suggest a stimulatory effect of Tofa on BMAd commitment and differentiation, which does not support a positive effect of Tofa on bone.

Bone Response to Weight Loss Following Bariatric Surgery

Obesity is a global health challenge that warrants effective treatments to avoid its multiple comorbidities. Bariatric surgery, a cornerstone treatment to control bodyweight excess and relieve the health-related burdens of obesity, can promote accelerated bone loss and affect skeletal strength, particularly after malabsorptive and mixed surgical procedures, and probably after restrictive surgeries. The increase in bone resorption markers occurs early and persist for up to 12 months or longer after bariatric surgery, while bone formation markers increase but to a lesser extent, suggesting a potential uncoupling process between resorption and formation. The skeletal response to bariatric surgery, as investigated by dual-energy X-ray absorptiometry (DXA), has shown significant loss in bone mineral density (BMD) at the hip with less consistent results for the lumbar spine. Supporting DXA studies, analyses by high-resolution peripheral quantitative computed tomography (HR-pQCT) showed lower cortical density and thickness, higher cortical porosity, and lower trabecular density and number for up to 5 years after bariatric surgery. These alterations translate into an increased risk of fall injury, which contributes to increase the fracture risk in patients who have been subjected to bariatric surgery procedures. As bone deterioration continues for years following bariatric surgery, the fracture risk does not seem to be dependent on acute weight loss but, rather, is a chronic condition with an increasing impact over time. Among the post-bariatric surgery mechanisms that have been claimed to act globally on bone health, there is evidence that micro- and macro-nutrient malabsorptive factors, mechanical unloading and changes in molecules partaking in the crosstalk between adipose tissue, bone and muscle may play a determining role. Given these circumstances, it is conceivable that bone health should be adequately investigated in candidates to bariatric surgery through bone-specific work-up and dedicated postsurgical follow-up. Specific protocols of nutrients supplementation, motor activity, structured rehabilitative programs and, when needed, targeted therapeutic strategies should be deemed as an integral part of post-bariatric surgery clinical support.

Bariatric surgery and skeletal health: A narrative review and position statement for management by the European Calcified Tissue Society (ECTS)

CONTEXT

Numerous studies have demonstrated detrimental skeletal consequences following bariatric surgery.

METHODS

A working group of the European Calcified Tissue Society (ECTS) performed an updated review of existing literature on changes of bone turnover markers (BTMs), bone mineral density (BMD), and fracture risk following bariatric surgery and provided advice on management based on expert opinion.

LITERATURE REVIEW

Based on observational studies, bariatric surgery is associated with a 21-44% higher risk of all fractures. Fracture risk is time-dependent and increases approximately 3 years after bariatric surgery. The bariatric procedures that have a malabsorptive component (including Roux-en-Y Gastric bypass (RYGB) and biliopancreatic diversion (BPD)) have clearly been associated with the highest risk of fracture. The extent of high-turnover bone loss suggests a severe skeletal insult. This is associated with diminished bone strength and compromised microarchitecture. RYGB was the most performed bariatric procedure worldwide until very recently, when sleeve gastrectomy (SG) became more prominent. There is growing evidence that RYGB is associated with greater reduction in BMD, greater increase in BTMs, and higher risk of fractures compared with SG but RCTs on optimal management are still lacking.

EXPERT OPINION

In all patients, it is mandatory to treat vitamin D deficiency, to achieve adequate daily calcium and protein intake and to promote physical activity before and following bariatric surgery. In post-menopausal women and men older than 50 years, osteoporosis treatment would be reasonable in the presence of any of the following criteria: i) history of recent fragility fracture after 40 years of age, ii) BMD T-score ≤ -2 at hip or spine, iii) FRAX score with femoral neck BMD exceeding 20% for the 10-year major osteoporotic fracture probability or exceeding 3% for hip fracture. Zoledronate as first choice should be preferred due to intolerance of oral formulations and malabsorption. Zoledronate should be used with caution due to hypocemia risk. It is recommended to ensure adequate 25-OH vitamin D level and calcium supplementation before administering zoledronate.

CONCLUSIONS

The bariatric procedures that have a malabsorptive component have been associated with the highest turnover bone loss and risk of fracture. There is a knowledge gap on osteoporosis treatment in patients undergoing bariatric surgery. More research is necessary to direct and support guidelines.

A comparison of changes in bone turnover markers after gastric bypass and sleeve gastrectomy, and their association with markers of interest

BACKGROUND

It is still debated whether differences in bone turnover markers (BTMs) exist between the 2 most popular bariatric surgery procedures (Roux-en-Y gastric bypass [RYGB] and sleeve gastrectomy [SG]).

OBJECTIVES

To compare changes in BTMs after RYGB and SG, and to investigate their association with predefined markers of interest.

SETTING

University hospital, Lille, France.

METHODS

An ancillary investigation of a prospective cohort was conducted. SG patients with severe obesity ≥40 years were matched one-to-one to RYGB patients for age, sex, body mass index (BMI), and menopausal status. BTMs, as well as predefined markers of interest, were measured at baseline, 12, and 24 months after bariatric surgery.

RESULTS

Sixty-four patients (66% women) had a mean (standard deviation [SD]) age of 49.6 years (5.1) and a mean (SD) BMI of 45.0 kg/m² (6.0). From baseline to 12 months, a significant increase in BTMs was observed in both groups (P < .001). Moreover, RYGB was associated with a greater increase in C-terminal telopeptide (β-CTX) and procollagen type 1 N-terminal propeptide (PINP) compared with SG (P < .0001). From 12 to 24 months, a significant decrease in BTMs was observed in both groups, but no significant differences were found between RYGB and SG. However, BTMs did not return to baseline levels. The changes in PINP and β-CTX at 12 months were independently associated with the type of surgical procedure, after adjusting for weight or each predefined marker of interest (all P < .0001).

CONCLUSION

RYGB was associated with a greater increase in BTMs than SG at 12 and 24 months.

PFAS and Potential Adverse Effects on Bone and Adipose Tissue Through Interactions With PPARγ

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a widely dispersed, broad class of synthetic chemicals with diverse biological effects, including effects on adipose and bone differentiation. PFAS most commonly occur as mixtures and only rarely, if ever, as single environmental contaminants. This poses significant regulatory questions and a pronounced need for chemical risk assessments, analytical methods, and technological solutions to reduce the risk to public and environmental health. The effects of PFAS on biological systems may be complex. Each may have several molecular targets initiating multiple biochemical events leading to a number of different adverse outcomes. An exposure to mixtures or coexposures of PFAS complicates the picture further. This review illustrates how PFAS target peroxisome proliferator-activated receptors. Additionally, we describe how such activation leads to changes in cell differentiation and bone development that contributes to metabolic disorder and bone weakness. This discussion sheds light on the importance of seemingly modest outcomes observed in test animals and highlights why the most sensitive end points identified in some chemical risk assessments are significant from a public health perspective.

Bone Marrow Adiposity in Premenopausal Women With Type 2 Diabetes With Observations on Peri-Trabecular Adipocytes

CONTEXT

No study has yet evaluated the relationships among bone marrow adiposity (BMA), bone histomorphometry (BH), and glycemic control in premenopausal women with type 2 diabetes (T2DM).

OBJECTIVE

We aimed to assess the effect of glycemic control on BMA, correlate the parameters of BH with BMA, and correlate BMA with the use of hypoglycemic agents and with bone mineral density (BMD).

METHODS

This was a cross-sectional study that evaluated 26 premenopausal women with T2DM who were divided into groups with HbA1c < 7% (good control [GC], n = 10) and HbA1c > 7% (poor control [PC], n = 16). BMA parameters (adipocyte number [Ad.N], total adipocyte perimeter [Ad.Pm], total adipocyte area [Ad.Ar], percentage adipocyte volume per marrow volume [Ad.V/Ma.V]) and peri-trabecular adipocyte number divided by bone surface (Ad.N/BS) were evaluated. BH static (bone volume fraction [BV/TV], osteoid thickness [O.Th], osteoid surface/bone surface [OS/BS]) and dynamic parameters and serum insulin-like growth factor-1 were measured. BMA data were compared between the GC and PC groups. Correlations were performed.

RESULTS

Ad.N, Ad.Pm, and Ad.Ar were higher in PC (all, P = 0.04). HbA1c correlated positively with Ad.N/BS (P < 0.01) and Ad.N/BS correlated negatively with O.Th (P < 0.01) and OS/BS (P = 0.02). Positive and negative correlations were observed between insulin and metformin use, respectively, with all adipocyte parameters except Ad.N/BS (P < 0.05). Structural parameters were negatively correlated with the BMA. BMD of the femoral neck (r = -549, P < 0.01) and total femur (r = -0.502, P < 0.01) were negatively correlated with Ad.V/Ma.V.

CONCLUSION

Poor glycemic control is associated with hyperplasia and hypertrophy of BMAs and with lower BV/TV. Ad.N/BS, a new BMA parameter, is correlated with HbA1c and negatively with O.Th. The use of insulin seems to stimulate the expansion of BMA while that of metformin has the opposite effect. These findings suggest that the increase in BMA may play a role in the T2DM bone disease; on the other hand, good glycemic control might help prevent it.

Diffusion-weighted magnetic resonance imaging of mandibular bone marrow: do apparent diffusion coefficient values of the cervical vertebrae and mandible correlate with age?

OBJECTIVES

The objective of this investigation was to assess the correlation between the mandible and cervical vertebrae bone marrow apparent diffusion coefficient (ADC), obtained by diffusion-weighted magnetic resonance imaging (DWI), with age; to verify the correlation between ADC values from the mandible and the cervical vertebrae; to describe and assess the differences between ADC values obtained from DWI examinations of distinct mandible areas as well as cervical vertebrae.

METHODS

Thirty imaging examinations with DWI for that included the mandible and C1, C2, C3, and C4 vertebrae in the same examination were included. ADC values were collected from 7 distinct areas in the mandible and the cervical vertebrae. Differences between ADC values and non-parametric correlations were performed.

RESULTS

A total of 270 regions were assessed. No significant difference was found between ADC values of all areas tested. An inverse correlation was found between C2, C3, and C4 vertebrae ADC values and age. The significant correlation of anatomic area ADC values and age were presented as graphics to verify if the linear trend of ADC values and age are in accordance with the literature CONCLUSIONS: The mandible area that most correlates with the cervical vertebrae, using ADC values, is the posterior trabecular area, below the inferior molars. Also, C2, C3, and C4 vertebrae ADC values inversely correlate with age, which demonstrates the bone qualitative changes in bone composition. ADC values may be useful for the qualitative assessment of bone quality to screen patients at osteoporosis risk.

Bone Aging, Cellular Senescence, and Osteoporosis

Changes in aging bone that lead to osteoporosis are mediated at multiple levels, including hormonal alterations, skeletal unloading, and accumulation of senescent cells. This pathological interplay is superimposed upon medical conditions, potentially bone-wasting medications, modifiable and unmodifiable personal risk factors, and genetic predisposition that accelerate bone loss with aging. In this study, the focus is on bone hemostasis and its dysregulation with aging. The major physiological changes with aging in bone and the role of cellular senescence in contributing to age-related osteoporosis are summarized. The aspects of bone aging are reviewed including remodeling deficits, uncoupling phenomena, inducers of cellular senescence related to bone aging, roles of the senescence-associated secretory phenotype, radiation-induced bone loss as a model for bone aging, and the accumulation of senescent cells in the bone microenvironment as a predominant mechanism for age-related osteoporosis. The study also addresses the rationale and potential for therapeutic interventions based on the clearance of senescent cells or suppression of the senescence-associated secretory phenotype. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.