Osteoporosis and Bone Marrow Adipose Tissue

GPx3 marks adipocyte lineage commitment in bone marrow stromal cells

BACKGROUND

Bone marrow adipose tissue (BMAT) plays an essential role in skeletal health and systemic metabolism, particularly under conditions of ageing and osteoporosis. Despite increasing recognition of BMAT as an active endocrine organ, the molecular mechanisms underlying its formation and expansion remain incompletely understood.

METHODS

We conducted a transcriptomic re-analysis of publicly available datasets focused on the adipogenic differentiation of bone marrow stromal cells (BMSCs). Differential gene expression and pathway enrichment analyses were performed to identify key molecular changes. Validation was conducted at both the transcript and protein levels. Furthermore, re-analysis of single-cell RNA sequencing (scRNA-seq) data was employed to determine the cell type-specific expression of candidate genes within the bone marrow. Functional assays using RNA interference were carried out to investigate the role of glutathione peroxidase 3 (GPx3) in adipogenesis.

RESULTS

Our analysis revealed a consistent activation of oxidative stress-related pathways during adipogenic differentiation. Among the upregulated antioxidant enzymes, GPx3 was selectively increased during adipogenic-but not osteogenic-differentiation. This pattern was validated at both mRNA and protein levels in vitro. scRNA-seq analysis showed that GPx3 expression is predominantly localized in BMSCs and adipocytes, with reduced expression observed in aged mice, corresponding to elevated levels of adipocyte-related genes. In vitro functional experiments demonstrated that GPx3 knockdown significantly promoted adipogenic differentiation of BMSCs.

CONCLUSION

These findings indicate that GPx3 is closely associated with adipocyte lineage commitment within the bone marrow microenvironment and may serve as a key modulator of BMSC fate. This study underscores the potential role of antioxidant enzymes such as GPx3 in the regulation of age-related bone-fat imbalance and highlights their relevance in metabolic bone disorders.

Association between visceral adiposity index and osteoarthritis in U.S. adults aged 50 and older: a cross-sectional study

Background

Existing evidence linking visceral adiposity index (VAI) to osteoarthritis (OA) remains limited and requires further investigation. This study aimed to evaluate the potential relationship between higher VAI scores and an increased risk of OA.

Methods

A retrospective cross-sectional analysis was conducted using data from 9,464 participants aged 50 and older, sourced from the 2011 to 2018 National Health and Nutrition Examination Survey (NHANES). The VAI was categorized into three tertiles, with the first tertile (T1) representing the lowest VAI and third tertile (T3) the highest. Weighted logistic regression was employed to examine the association between VAI and OA. To explore potential non-linear relationships, smoothed curve fitting and threshold effect analyses were performed. Subgroup analyses were performed to validate these findings.

Results

The average age of the study population was 63.16 ± 9.05 years, and 47.22% were male. After adjusting for confounding factors, a statistically significant positive correlation was observed between VAI and OA risk (OR = 1.03, 95% CI: 1.01-1.06, P < 0.01). Participants in the highest VAI tertile exhibited a 35% greater likelihood of developing OA compared to those in the lowest tertile (OR = 1.35, 95% CI: 1.06-1.70, P = 0.015). Furthermore, multivariate restricted cubic spline (RCS) regression analysis revealed a non-linear relationship (non-linear P < 0.05) with a threshold effect at a VAI value of 3.9. Subgroup analyses showed no significant interaction effects (all P-values for interaction > 0.05).

Conclusion

This study highlights a significant association between elevated VAI and an increased risk of developing OA in individuals aged 50 and older. These results emphasize the potential of the VAI as a risk factor for OA and warrant further research to explore its role in prevention and management strategies in older populations.

FABP4 inhibition suppresses bone resorption and protects against postmenopausal osteoporosis in ovariectomized mice

Postmenopausal osteoporosis (PMOP) is a condition in women caused by estrogen deficiency, characterized by reduced bone mass and increased fracture risk. Fatty acid-binding protein 4 (FABP4), a lipid-binding protein involved in metabolism and inflammation, has emerged as a key regulator in metabolic disorders and bone resorption; however, its direct role in PMOP remains unclear. Here, we show that serum FABP4 levels in PMOP patients negatively correlate with bone mineral density, a trend also observed in ovariectomized mice. FABP4 promotes osteoclast formation and bone resorption without affecting osteoblast differentiation. The FABP4 inhibitor BMS309403 suppresses osteoclast differentiation by modulating calcium signaling and inhibiting the Ca2+-Calcineurin-NFATc1 pathway. Oral BMS309403 increases bone mineral density in ovariectomized mice, though less effectively than alendronate. Notably, bone-targeted delivery of BMS309403 achieves comparable efficacy to alendronate. In this work, we demonstrate that FABP4 is a critical mediator in PMOP and that its inhibition offers a promising therapeutic strategy.

Implication of bone marrow adipose tissue in bone homeostasis during osteoarthritis

OBJECTIVE

To explore the role of bone marrow adipocytes (BMAds) in osteoarthritis (OA).

METHODS

Male and female C57BL/6 mice (n=4/group) underwent meniscectomy (MNX) or SHAM surgery. OA was determined using Osteoarthritis Research Society International (OARSI) score, and the number of perilipin+ adipocytes was quantified. Mesenchymal Stromal Cells (MSCs) from MNX and SHAM mice were differentiated into osteoblasts and adipocytes. Human adipocytes and MSCs (n=8) were enzymatically isolated from epiphyseal and metaphyseal marrow, and from subcutaneous adipose tissue (SCAT) of hip OA patients. Human OA MSCs were differentiated into osteoblasts and adipocytes (OA-Diff-hAdipo). Gene expression patterns of epiphyseal and metaphyseal BMAds, SCAT adipocytes and OA-Diff-hAdipo were evaluated by RNAseq (n=4). The effect conditioned media from OA epiphyseal bone (n=5) on the alkaline phosphatase (ALP) activity and mineralization kinetics was assessed in vitro.

RESULTS

Increase in BMAd density was positively correlated with cartilage degradation in MNX mice. OA modified the differentiation capacity of MSCs, accelerating adipocyte differentiation and failing to produce osteoblasts in both human and mice. Human epiphyseal, metaphyseal and SCAT adipocytes from the same OA patients each displayed a specific transcriptome, suggesting different functions. Enrichment analysis defined metaphyseal OA-BMAds as cells implicated in hematopoietic stem cell differentiation. On the other hand, epiphyseal OA-BMAds were considered as osteogenic cells showing an up-regulation of genes related to bone mineralization and remodeling. Specifically, OA epiphysis-secreted molecules decreased ALP activity and altered in vitro the mineralization process.

CONCLUSION

All these results support the emergence of BMAds as new cell partners in OA, opening new venues for therapeutic approaches.

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.

Effects of Exercise on Bone Marrow Adipose Tissue in Children With Overweight/Obesity: Role of Liver Fat

CONTEXT

Exercise reduces adiposity, but its influence on bone marrow fat fraction (BMFF) is unknown; nor is it known whether a reduction in liver fat content mediates this reduction.

OBJECTIVES

This work aimed to determine whether incorporating exercise into a lifestyle program reduces the lumbar spine (LS) BMFF and to investigate whether changes in liver fat mediate any such effect.

METHODS

Ancillary analysis of a 2-arm, parallel, nonrandomized clinical trial was conducted at primary care centers in Vitoria-Gasteiz, Spain. A total of 116 children with overweight/obesity were assigned to a 22-week family-based lifestyle program (control group [n = 57]) or the same program plus an exercise intervention (exercise group [n = 59]). The compared interventions consisted of a family-based lifestyle program (two 90-minute sessions/month) and the same program plus supervised exercise (three 90-minute sessions/week). The primary outcome examined was the change in LS-BMFF between baseline and 22 weeks, as estimated by magnetic resonance imaging. The effect of changes in hepatic fat on LS-BMFF were also recorded.

RESULTS

Mean weight loss difference between groups was 1.4 ± 0.5 kg in favor of the exercise group. Only the children in the exercise group experienced a reduction in LS-BMFF (effect size [Cohen d] -0.42; CI, -0.86 to -0.01). Importantly, 40.9% of the reductions in LS-BMFF were mediated by changes in percentage hepatic fat (indirect effect: β=-0.104; 95% CI, -0.213 to -0.019). The effect of changes in hepatic fat on LS-BMFF was independent of weight loss.

CONCLUSION

The addition of exercise to a family-based lifestyle program designed to reduce cardiometabolic risk improves bone health by reducing LS-BMFF in children with overweight or obesity. This beneficial effect on bone marrow appears to be mediated by reductions in liver fat.

Osteocyte connexin hemichannels and prostaglandin E2 release dictate bone marrow mesenchymal stromal cell commitment

Bone is a dynamic organ constantly undergoing remodeling with both bone formation and resorption. Bone formation is mediated by osteoblasts originating from the differentiation of bone marrow (BM) mesenchymal stem and progenitor cells (BM-MSPCs). However, how bone cells communicate with BM-MSPCs to coordinate bone formation remains largely elusive. Here, we unveil a key role of osteocyte connexin 43 (Cx43) hemichannels in regulating the lineage commitment of BM-MSPCs. Two transgenic mouse models expressing dominant negative Cx43 mutants in osteocytes were used: R76W (inhibiting gap junctions) and Δ130 to 136 (inhibiting both hemichannels and gap junctions). BM-MSPCs from Δ130 to 136 mice showed enhanced adipogenic differentiation and reduced osteogenic potential, leading to increased BM adipocytes. Flow cytometry and single-cell RNA sequencing revealed shifts in BM-MSPC subsets, less osteogenic-biased MSPCs, and more adipogenic-biased MSPCs in Δ130 to 136 mice. Conversely, R76W, with more functional hemichannels, exhibited effects similar to WT mice or even greater opposite effects than Δ130 to 136 mice. Prostaglandin E2 (PGE2), released from active Cx43 hemichannels, inhibited adipogenesis and promoted osteogenesis via the PGE2 receptor EP4 and ERK1/2 signaling. Inhibition of Cx43 hemichannels or EP4 led to increased adipogenic-biased MSPCs. Moreover, administration of a Cx43(M1) antibody, which inhibits hemichannels, substantially increased BM adipocytes, accompanied by increased adipogenic-biased MSPCs, and decreased osteogenic-biased MSPCs. Our study highlights the pivotal role of osteocyte Cx43 hemichannels in BM-MSPC fate decision through PGE2 release, providing insights into the precise and highly regulated communication between matrix-bound bone cells and BM-MSPCs, which dictates bone formation and remodeling.

Assessing fat fraction and R2* value of lumbar spine based on MRI as a marker of bone mineral density

OBJECTIVES

The study aimed to investigate the correlation between fat fraction (FF), R2* value of vertebrae based on IDEAL-IQ sequence and bone mineral density (BMD) based on QCT, and their diagnostic value for low BMD and osteoporosis.

METHODS

Subgroups were divided according to different gender, age, BMI, and bone mass to compare the differences in parametric variables. One-way ANOVA, independent samples t-test, correlation coefficient analysis, linear regression analysis, and ROC curve analysis were performed.

RESULTS

Significant differences were found in FF among different bone mass groups, and between different gender and age groups. While R2* only had a significant difference between different gender groups and males with different ages. BMD was significantly negatively correlated with FF, especially in women, and FF significantly negatively affected BMD after controlling for gender, age, and BMI. There was mildly positive correlation between BMD and R2* in men, and R2* significantly positively influenced BMD controlling for the confounders. In addition, FF was positively correlated with age, whereas R2* was negatively correlated with age in men. FF had high diagnostic efficacy for low bone mass and osteoporosis, while R2* alone was weakly diagnostic.

CONCLUSIONS

Vertebral FF can be served as a potentially important imaging biomarker for assessing low BMD and osteoporosis, and R2* of males can be utilized as a complementary parameter for evaluating osteoporosis.

ADVANCES IN KNOWLEDGE

The IDEAL-IQ sequence has the potential to be used as an accessory examination in the diagnosis of osteoporosis, assessment of treatment efficacy, and prediction of fracture risk.

Nutrition and Bone Marrow Adiposity in Relation to Bone Health

Bone remodeling is energetically demanding process. Energy coming from nutrients present in the diet contributes to function of different cell type including osteoblasts, osteocytes and osteoclasts in bone marrow participating in bone homeostasis. With aging, obesity and osteoporosis the function of key building blocks, bone marrow stromal cells (BMSCs), changes towards higher accumulation of bone marrow adipose tissue (BMAT) and decreased bone mass, which is affected by diet and sex dimorphism. Men and women have unique nutritional needs based on physiological and hormonal changes across the life span. However, the exact molecular mechanisms behind these pathophysiological conditions in bone are not well-known. In this review, we focus on bone and BMAT physiology in men and women and how this approach has been taken by animal studies. Furthermore, we discuss the different diet interventions and impact on bone and BMAT in respect to sex differences. We also discuss the future perspective on precision nutrition with a consideration of sex-based differences which could bring better understanding of the diet intervention in bone health and weight management.

circNDUFA13 stimulates adipogenesis of bone marrow-derived mesenchymal stem cells via interaction with STAT3

Circular RNAs (circRNAs) in controlling gene expression have been highlighted by increasing evidence, and their dysregulation has been linked to various diseases. However, the limited role of circRNAs in the adipogenesis of bone marrow-derived mesenchymal stem cells (BMSCs) has been explored. High-throughput sequencing of circRNA was carried out on BMSCs and AD induction 7d BMSCs. Then a substantial upregulation of circNDUFA13 was detected among circRNAs in AD induction 7d BMSCs. We found that the adipogenic differentiation of BMSCs was positively linked with circNDUFA13 expression levels. Adipogenesis in BMSCs was effectively inhibited by circNDUFA13 knockdown, whereas overexpression of circNDUFA13 promoted adipogenesis. It was noted that circNDUFA13 regulated the adipogenic differentiation of BMSCs by directly interacting with the signal transducer and activator of transcription 3 (STAT3), which activates CEBPβ transcription. The in vitro model also validated the in vivo findings. our results suggest that circNDUFA13 controlled the adipogenic differentiation of BMSCs by targeting STAT3 and CEBPβ activation.

NOX4-reactive oxygen species axis: critical regulators of bone health and metabolism

Bone marrow stromal cells (BMSCs) play a significant role in bone metabolism as they can differentiate into osteoblasts, bone marrow adipocytes (BMAds), and chondrocytes. BMSCs chronically exposed to nutrient overload undergo adipogenic programming, resulting in bone marrow adipose tissue (BMAT) formation. BMAT is a fat depot transcriptionally, metabolically, and morphologically distinct from peripheral adipose depots. Reactive oxygen species (ROS) are elevated in obesity and serve as important signals directing BMSC fate. ROS produced by the NADPH oxidase (NOX) family of enzymes, such as NOX4, may be responsible for driving BMSC adipogenesis at the expense of osteogenic differentiation. The dual nature of ROS as both cellular signaling mediators and contributors to oxidative stress complicates their effects on bone metabolism. This review discusses the complex interplay between ROS and BMSC differentiation in the context of metabolic bone diseases.Special attention is paid to the role of NOX4-ROS in regulating cellular processes within the bone marrow microenvironment and potential target in metabolic bone diseases.

Therapeutic effects of ginsenosides on osteoporosis for novel drug applications

Osteoporosis (OP) is a metabolic bone disease with a high incidence rate worldwide. Its main features are decreased bone mass, increased bone fragility and deterioration of bone microstructure. It is caused by an imbalance between bone formation and bone resorption. Ginsenoside is a safe and effective traditional Chinese medicine (TCM) usually extracted from ginseng plants, having various therapeutic effects, of which the effect against osteoporosis has been extensively studied. We searched a total of 44 relevant articles with using keywords including osteoporosis, ginsenosides, bone mesenchymal cells, osteoblasts, osteoclasts and bone remodeling, all of which investigated the cellular mechanisms of different types of ginsenosides affecting the activity of bone remodeling by mesenchymal stem cells, osteoblasts and osteoclasts to counteract osteoporosis. This review describes the different types of ginsenosides used to treat osteoporosis from different perspectives, providing a solid theoretical basis for future clinical applications.

Assessing osteoporosis in postmenopausal women: preliminary results using a novel lumbar spine phantom-based MRI scoring method

OBJECTIVE

To develop a novel magnetic resonance imaging (MRI) phantom for producing F-score (for fat) and W-score (for water) and to evaluate the performance of these scores in assessing osteoporosis and related vertebral fractures.

MATERIALS AND METHODS

First, a real-time phantom consisting of oil and water tubes was manufactured. Then, 30 female volunteers (age: 62.3 ± 6.3 years) underwent lumbar spine examination with MRI (using a novel phantom) and dual-energy X-ray absorptiometry (DXA), following ethical approval. MRI phantom-based F-score and W-score were defined by normalizing the vertebral signal intensities (SIs) by the oil and water SIs of the phantom on T1- and T2-weighted images, respectively. The diagnostic performances of the new scores for assessing osteoporosis and vertebral fractures were examined using receiver operating characteristic analysis and compared with DXA-measured areal bone mineral density (DXA-aBMD).

RESULTS

The F-score and W-score were greater in the osteoporotic patients (3.93 and 2.29) than the non-osteoporotic subjects (3.05 and 1.79) and achieved AUC values of 0.85 and 0.74 (p < 0.05), respectively, when detecting osteoporosis. Similarly, F-score and W-score had greater values for the fracture patients (3.94 and 2.53) than the non-fracture subjects (3.14 and 1.69) and produced better AUC values (0.90 for W-score and 0.79 for F-score) compared to DXA-aBMD (AUC: 0.27, p < 0.05). In addition, the F-score and W-score had a strong correlation (r = 0.77; p < 0.001).

CONCLUSION

A novel real-time lumber spine MRI phantom was developed, based upon which newly defined F-score and W-score were able to detect osteoporosis and demonstrated an improved ability over DXA-aBMD in differentiating patients with vertebral fractures.

Fatty-marrow transformation following radiotherapy for pancreatic cancer detected using dual-energy computed tomography: A case report

Bone damage, a late side effect of radiotherapy, occurs concurrently with the replacement of fat cells in the bone marrow, causing changes in bone composition. Changes in composition can affect bone quality and disease states, and reduced bone mass can reduce quality of life by increasing the risk of fractures. A 70-year-old woman presented to the orthopedic outpatient clinic with the chief complaint of lower-back pain. The patient reported no history of trauma but was in great pain and had difficulty walking. Since the patient had a history of pancreatic cancer, tumor-marker testing, bone scintigraphy, and dual-energy computed tomography were performed. Although the tumor-marker levels were normal, dual-energy computed tomography and bone scintigraphy revealed fresh compression fractures of the L1 and L3 vertebrae. In addition, dual-energy computed tomography material-discrimination analysis suggested high fat density in the L2 vertebral body. The patient had received approximately 30 Gy radiation to the L2 vertebral body for her pancreatic cancer, which resulted in fatty myelination in the bone. The diagnosis of fatty myelination is made on T1-weighted magnetic resonance images; however, diagnosis remains challenging because of the difficulty in assessing bone morphology on magnetic resonance images. Moreover, some patients are not candidates for magnetic resonance imaging. Dual-energy computed tomography-based material-discrimination analysis can visually depict changes in the bone marrow, and is a valuable diagnostic tool owing to its simplicity.

Bone marrow adipocytes and lung cancer bone metastasis: unraveling the role of adipokines in the tumor microenvironment

Bone is a common site of metastasis for lung cancer. The "seed and soil" hypothesis suggests that the bone marrow microenvironment ("soil") may provide a conducive survival environment for metastasizing tumor cells ("seeds"). The bone marrow microenvironment, comprising a complex array of cells, includes bone marrow adipocytes (BMAs), which constitute about 70% of the adult bone marrow volume and may play a significant role in tumor bone metastasis. BMAs can directly provide energy for tumor cells, promoting their proliferation and migration. Furthermore, BMAs participate in the tumor microenvironment's osteogenesis regulation, osteoclast(OC) regulation, and immune response through the secretion of adipokines, cytokines, and inflammatory factors. However, the precise mechanisms of BMAs in lung cancer bone metastasis remain largely unclear. This review primarily explores the role of BMAs and their secreted adipokines (leptin, adiponectin, Nesfatin-1, Resistin, chemerin, visfatin) in lung cancer bone metastasis, aiming to provide new insights into the mechanisms and clinical treatment of lung cancer bone metastasis.

Comparison of the accuracy of commercial two-point and multi-echo Dixon MRI for quantification of fat in liver, paravertebral muscles, and vertebral bone marrow

PURPOSE

Excess fat accumulation contributes significantly to metabolic dysfunction and diseases. This study aims to systematically compare the accuracy of commercially available Dixon techniques for quantification of fat fraction in liver, skeletal musculature, and vertebral bone marrow (BM) of healthy individuals, investigating biases and sex-specific influences.

METHOD

100 healthy White individuals (50 women) underwent abdominal MRI using two-point and multi-echo Dixon sequences. Fat fraction (FF), proton density fat fraction (PDFF) and T2* values were calculated for liver, paravertebral muscles (PVM) and vertebral BM (Th8-L5). Agreement and systematic deviations were assessed using linear correlation and Bland-Altman plots.

RESULTS

High correlations between FF and PDFF were observed in liver (r = 0.98 for women; r = 0.96 for men), PVM (r = 0.92 for women; r = 0.93 for men) and BM (r = 0.97 for women; r = 0.95 for men). Relative deviations between FF and PDFF in liver (18.92 % for women; 13.32 % for men) and PVM (1.96 % for women; 11.62 % for men) were not significant. Relative deviations in BM were significant (38.13 % for women; 27.62 % for men). Bias correction using linear models reduced discrepancies. T2* times were significantly shorter in BM (8.72 ms for women; 7.26 ms for men) compared to PVM (13.45 ms for women; 13.62 ms for men) and liver (29.47 ms for women; 26.35 ms for men).

CONCLUSION

While no significant differences were observed for liver and PVM, systematic errors in BM FF estimation using two-point Dixon imaging were observed. These discrepancies - mainly resulting from organ-specific T2* times - have to be considered when applying two-point Dixon approaches for assessment of fat content. As suitable correction tools, linear models could provide added value in large-scale epidemiological cohort studies. Sex-specific differences in T2* should be considered.

Effect of Tempeh and Daidzein on Calcium Status, Calcium Transporters, and Bone Metabolism Biomarkers in Ovariectomized Rats

Menopause marks a critical life stage characterized by hormonal changes that significantly impact bone health, leading to a heightened susceptibility to bone fractures. This research seeks to elucidate the impact of daidzein and tempeh on calcium status, calcium transporters, and bone metabolism in an ovariectomized rat model. Forty female Wistar rats, aged 3 months, participated in a two-phase experiment. The initial phase involved inducing a calcium deficit, while the second phase comprised dietary interventions across five groups: Sham (S) and Ovariectomy (O) with a standard diet, O with bisphosphonate (OB), O with pure daidzein (OD), and O with tempeh (OT). Multiple parameters, encompassing calcium levels, calcium transporters, bone histopathology, and serum bone metabolism markers, were evaluated. The findings revealed that the OT group showcased heightened levels of bone turnover markers, such as pyridinoline, C-telopeptide of type I collagen, bone alkaline phosphatase, and procollagen type I N-terminal propeptide, in contrast to S and O groups, with statistical significance (p < 0.05). Histopathologically, both the OD and OT groups exhibited effects akin to the OB group, indicating a decrease in the surface area occupied by adipocytes in the femoral bone structure, although statistically non-equivalent, supporting the directionally similar trends. Although TRPV5 and TRPV6 mRNA expression levels in the jejunum and duodenum did not display statistically significant differences (p > 0.05), the OD and OT groups exhibited increased expression compared to the O group. We hypothesized that obtained results may be related to the effect of isoflavones on estrogen pathways because of their structurally similar to endogenous estrogen and weak estrogenic properties. In conclusion, the daily consumption of pure daidzein and tempeh could potentially improve and reinstate calcium status, calcium transport, and bone metabolism in ovariectomized rats. Additionally, isoflavone products demonstrate effects similar to bisphosphonate drugs on these parameters in ovariectomized rats.

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.

Disturbed bone marrow adiposity in patients with Cushing's syndrome and glucocorticoid- and postmenopausal- induced osteoporosis

Background

Skeletal stem/progenitor cells (SSPCs) in the bone marrow can differentiate into osteoblasts or adipocytes in response to microenvironmental signalling input, including hormonal signalling. Glucocorticoids (GC) are corticosteroid hormones that promote adipogenic differentiation and are endogenously increased in patients with Cushing´s syndrome (CS). Here, we investigate bone marrow adiposity changes in response to endogenous or exogenous GC increases. For that, we characterize bone biopsies from patients with CS and post-menopausal women with glucocorticoid-induced osteoporosis (GC-O), compared to age-matched controls, including postmenopausal osteoporotic patients (PM-O).

Methods

Transiliac crest bone biopsies from CS patients and healthy controls, and from postmenopausal women with GC-O and matched controls were analysed; an additional cohort included biopsies from women with PM-O. Plastic-embedded biopsies were sectioned for histomorphometric characterization and quantification of adipocytes. The fraction of adipocyte area per tissue (Ad.Ar/T.Ar) and marrow area (Ad.Ar/Ma.Ar), mean adipocyte profile area (Ad.Pf.Ar) and adipocyte profile density (N.Ad.Pf/Ma.Ar) were determined and correlated to steroid levels. Furthermore, the spatial distribution of adipocytes in relation to trabecular bone was characterized and correlations between bone marrow adiposity and bone remodeling parameters investigated.

Results

Biopsies from patients with CS and GC-O presented increased Ad.Ar/Ma.Ar, along with adipocyte hypertrophy and hyperplasia. In patients with CS, both Ad.Ar/Ma.Ar and Ad.Pf.Ar significantly correlated with serum cortisol levels. Spatial distribution analyses revealed that, in CS, the increase in Ad.Ar/Ma.Ar near to trabecular bone (<100 µm) was mediated by both adipocyte hypertrophy and hyperplasia, while N.Ad.Pf/Ma.Ar further into the marrow (>100 µm) remained unchanged. In contrast, patients with GC-O only presented increased Ad.Ar/Ma.Ar and mean Ad.Pf.Ar>100 µm from trabecular bone surface, highlighting the differential effect of increased endogenous steroid accumulation. Finally, the Ad.Ar/Ma.Ar and Ad.Ar/T.Ar correlated with the canopy coverage above remodeling events.

Conclusion

Increased cortisol production in patients with CS induces increased bone marrow adiposity, primarily mediated by adipocyte hypertrophy. This adiposity is particularly evident near trabecular bone surfaces, where hyperplasia also occurs. The differential pattern of adiposity in patients with CS and GC-O highlights that bone marrow adipocytes and their progenitors may respond differently in these two GC-mediated bone diseases.

Global and local fat effects on bone mass and quality in obesity

Aims

The aim of this study was to investigate the global and local impact of fat on bone in obesity by using the diet-induced obese (DIO) mouse model.

Methods

In this study, we generated a diet-induced mouse model of obesity to conduct lipidomic and 3D imaging assessments of bone marrow fat, and evaluated the correlated bone adaptation indices and bone mechanical properties.

Results

Our results indicated that bone mass was reduced and bone mechanical properties were impaired in DIO mice. Lipidomic sequencing and bioinformatic analysis identified 373 differential lipids, 176 of which were upregulated and 197 downregulated. Functional enrichment analysis revealed a significant downregulation of the pathways: fat digestion and absorption (ko04975) and lipolysis regulation in adipocytes (ko04923) in DIO mice, leading to local fat accumulation. The use of 3D imaging confirmed the increase in fat accumulation within the bone marrow cavity of obese mice.

Conclusion

Our study sheds light on the intricate interplay between fat and bone, and provides a non-toxic and non-invasive method for measuring marrow adipose tissue.

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.