New insights into osteoporosis: the bone-fat connection

Apoptotic vesicles inhibit bone marrow adiposity via wnt/β-catenin signaling

Background

There is currently increasing focus on aging-related diseases. Osteoporosis is a common disease the incidence of which increases with age. In older patients with osteoporosis, bone marrow mesenchymal stem cells (BMMSCs) have a decreased capacity for osteogenesis and an increased capacity for adipogenesis, causing excessive accumulation of adipose tissue in the bone marrow. Therefore, means of reducing bone marrow adiposity may have therapeutic potential for osteoporosis. Apoptotic vesicles (apoVs) participate in a wide range of physiological processes and have been shown to have therapeutic effects in a variety of diseases. The principal objective of this study was to examine the special properties and regulatory mechanisms of BMMSC-derived apoVs in the treatment of bone marrow adiposity.

Results

The results showed that apoVs could decrease bone marrow adiposity in osteoporotic mice and prevent adipogenic differentiation of MSCs by activating the Wnt/β-catenin pathway.

Conclusion

New apoV-based therapies have potential for the treatment of bone marrow adiposity in patients with aging-related osteoporosis and may be further applicable to the treatment of obesity and aging-related diseases.

Higher serum resistin levels and increased frailty risk in older adults: Implications beyond metabolic function

BACKGROUND

Despite the pleiotropic role of resistin as an adipokine, its association with frailty-an indicator of biologic age and overall well-being in humans-remains largely unexplored. This study aims to investigate the potential of circulating resistin as a biomarker for frailty.

METHODS

The study included 228 older adults aged 65 years or older who underwent a comprehensive geriatric assessment. Frailty was evaluated using both the phenotypic frailty model by Fried and the deficit-accumulation frailty index (FI) by Rockwood. Serum resistin levels were measured using a competitive enzyme-linked immunosorbent assay.

RESULTS

After adjusting for sex, age, body mass index, smoking, alcohol, exercise, diabetes, and serum creatinine, serum resistin levels were 52.2% higher in individuals with phenotypic frailty than in robust controls (P =  0.001) and showed a positive correlation with the Rockwood FI (P =  0.015). Furthermore, for every 1 standard deviation increase in serum resistin levels, the risk of frailty increased by 67% (P =  0.021). When participants were divided into four groups based on serum resistin levels, individuals in the highest quartile had a 38% higher FI and exhibited a 12.5-fold higher odds ratio for frailty compared to those in the lowest quartile (P =  0.016 and 0.024, respectively).

CONCLUSION

These findings suggest that circulating resistin may serve as a candidate blood-based biomarker for frailty, encompassing the multifaceted physical, cognitive, and social dimensions, extending beyond its well-established role in metabolic regulation.

Proton Density Fat Fraction Micro-MRI for Non-Invasive Quantification of Bone Marrow Aging and Radiation Effects in Mice

BACKGROUND

Bone marrow (BM) adipocytes play a critical role in the progression of both solid tumor metastases and expansion of hematological malignancies across a spectrum of ages, from pediatric to aging populations. Single-point biopsies remain the gold standard for monitoring BM diseases, including hematologic malignancies, but these are limited in capturing the full complexity of loco-regional and global BM microenvironments. Non-invasive imaging techniques such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT), and Positron Emission Tomography (PET) could provide valuable alternatives for real-time evaluation in both preclinical translational and clinical studies.

METHODS

We developed a preclinical proton density fat fraction (PDFF) MRI technique for the quantitative assessment of BM composition, focusing on the fat fraction (FF) within mouse femurs. We validated this method using aging mice and young mice subjected to 10 Gy X-ray irradiation, compared to young control mice. Water-fat phantoms with varying fat percentages (0% to 100%) were used to optimize the imaging sequence, and immunohistochemical (IHC) staining with H&E validated equivalent adipose content in the femur BM region.

RESULTS

Significant differences in FF were observed across age groups (p = 0.001 for histology and p < 0.001 for PDFF) and between irradiated and control mice (p = 0.005 for histology and p = 0.002 for PDFF). A strong correlation (R2~0.84) between FF values from PDFF-MRI and histology validated the accuracy of the technique.

CONCLUSIONS

These findings highlight PDFF-MRI's potential as a non-invasive, real-time, in vivo biomarker for quantitatively assessing the BM fat fraction in preclinical studies, particularly in studies evaluating the effects of aging, disease progression, and cytotoxic cancer therapies, including chemotherapy and radiation.

Primary components of MCT ketogenic diet are detrimental to bone loss associated with accelerated aging and age-related neurotoxicity in mice

Medium chained triglycerides (MCT) ketogenic diet is being extensively investigated for its neuroprotective effects against adverse effects associated with aging and neurodegenerative disorders. Aging is a common risk factor for the development of both osteoporosis and neurological disorders. Hence, suppression of aging and age-related neurodegeneration might contribute to delaying skeletal aging. The present study was designed to investigate the effects of the primary components of the MCT diet, against bone resorption associated with D-gal-induced accelerated aging and D-gal /AlCl3-induced age-related toxicity. We report bone loss in accelerated aged mice and age-related neurotoxic mice through declined Sirtuin1 (SIRT1) expression, depleted bone turnover markers, (P1NP and β-CTX-1), low bone mineral density (BMD), and deterioration of trabecular bone microarchitecture in both the distal femur and proximal tibia bones. Administration of MCT dietary components decanoic acid and octanoic acid, led to a decrease in body weight and only octanoic acid increased serum levels of ketone body, β-hydroxybutyrate (β-HB), but both of them failed to reverse the diminishing effects on bone health associated with aging and age-related neurotoxicity. Surprisingly, decanoic acid, octanoic acid, and their combination also exhibited negative effects on trabecular bone microarchitecture and BMD in the distal femur and proximal tibia bones of healthy mice. The findings from this study provide supporting evidence on the deterioration of bone health associated with aging and age-related neurotoxicity, and the bone resorption potential of MCT dietary supplements that are being prescribed in healthy older populations and elderly persons diagnosed with neurological disorders.

The crucial role of beta-catenin in the osteoprotective effect of semaglutide in an ovariectomized rat model of osteoporosis

Postmenopausal osteoporosis is a common chronic medical illness resulting from an imbalance between bone resorption and bone formation along with microarchitecture degeneration attributed to estrogen deficiency and often accompanied by other medical conditions such as weight gain, depression, and insomnia. Semaglutide (SEM) is a recently introduced GLP-1 receptor agonist (GLP-1RA) for the treatment of obesity and type 2 diabetes mellitus by mitigating insulin resistance. It has been discovered that the beneficial effects of GLP-1 are associated with alterations in lipolysis, adipogenesis, and anti-inflammatory processes. GLP-1 analogs transmit signals directly to adipose tissue. Mesenchymal stem cells (MSCs) are multidisciplinary cells that originate from bone marrow, migrate to injury sites, and promote bone regeneration. MSCs can differentiate into osteoblasts, adipose cells, and cartilage cells. Our aim is to investigate the role of semaglutide on bone formation and the Wnt signaling pathway. Osteoporosis was induced in female rats by ovariectomy, and the ovariectomized rats were treated with alendronate as standard treatment with a dose of 3 mg/kg orally and semaglutide with two doses (150 mcg/kg and 300 mcg/kg) S.C. for 10 successive weeks. Semaglutide ameliorates bone detrimental changes induced by ovariectomy. It improves bone microarchitecture and preserves bone mineral content. Semaglutide ameliorates ovariectomy-induced osteoporosis and increases the expression of β-catenin, leading to increased bone formation and halted receptor activator of nuclear factor kappa-Β ligand (RANKL's) activation. Semaglutide can be used as a potential prophylactic and therapeutic drug against osteoporosis, possibly by activating Wnt signaling and decreasing bone resorption.

ALG5 downregulation inhibits osteogenesis and promotes adipogenesis by regulating the N-glycosylation of SLC6A9 in osteoporosis

Osteoporosis is characterized by decreased bone mass and accumulation of adipocytes in the bone marrow. The mechanism underlying the imbalance between osteoblastogenesis and adipogenesis in bone marrow mesenchymal stem cells (BMSCs) remains unclear. We found that ALG5 was significantly downregulated in BMSCs from osteoporotic specimens. ALG5 knockdown inhibited osteogenic differentiation and increased adipogenic differentiation of BMSCs. ALG5 deficiency diminished the N-glycosylation of SLC6A9, thereby altering its protein stability and disrupting SLC6A9-mediated glycine uptake in BMSCs. ALG5 overexpression by adeno-associated virus serotype 9 (rAAV9) alleviated bone loss in OVX mice. Taken together, our findings suggest a novel role for the ALG5-SLC6A9-glycine axis in the imbalance of BMSC differentiation in osteoporosis. Moreover, we identify ALG5 overexpression as a potential therapeutic strategy for treating osteoporosis.

Evaluating the role of biological age in osteoporosis risk among middle-aged and older adults: A nationwide perspective

OBJECTIVES

This study aimed to investigate the association between biological age acceleration and osteoporosis (OP) risk in middle-aged and older adults using data from the National Health and Nutrition Examination Survey (NHANES). The research focused on analyzing the relationship between two biological aging metrics, Klemera-Doubal Method Age (KDMAge) and Phenotypic Age (PhenoAge), and OP risk.

METHODS

The study analyzed data from NHANES, which included 6550 participants aged 50 and above from survey cycles 2005-2010 and 2017-2018. Linear and logistic regression were used to investigate the relationship between biological age acceleration (KDMAgeAccel and PhenoAgeAccel) and OP. Subgroup analysis was performed by age, gender and other factors. Multivariable Cox regression analysis yielded Hazard Ratios (HRs) relating biological age acceleration to mortality were evaluated. The study also considered the mediating roles of body mass index (BMI).

RESULTS

KDMAgeAccel (odds ratio [OR] = 2.34, 95 % CI, 1.72-3.18) and PhenoAgeAccel (OR = 2.03, 95 % CI, 1.48-2.78) were significantly associated with increased OP risk and reduced bone mineral density (BMD). Specifically, higher KDMAgeAccel and PhenoAgeAccel were linked to higher OP prevalence and lower BMD at multiple sites. Subgroup analyses indicated that the association between accelerated biological age acceleration and OP risk was consistent across different demographics. Mediation analysis revealed that BMI partially mediated the relationship between accelerated biological age and OP, although other mechanisms are likely involved. Statistical analysis indicated that individuals with higher biological age metrics had increased mortality risk related to OP.

CONCLUSION

The findings suggest that accelerated biological age is a robust predictor of OP risk and related mortality. KDMAgeAccel and PhenoAgeAccel could serve as valuable biomarkers for identifying individuals at high risk for OP, guiding preventive strategies.

What Is the Best Method for Diagnosing Osteosarcopenic Adiposity in Women After Long-Term Bariatric Surgery? A Comparison and Validation of Different Criteria

BACKGROUND/OBJECTIVES

To evaluate the agreement and discriminant validation of different osteosarcopenic adiposity (OSAd) diagnostic criteria in women post-Roux-en-Y gastric bypass (RYGB) surgery.

METHODS

Surgery. This is a cross-sectional study with women ≥2 years post-RYGB. OSAd was diagnosed using three criteria: Kelly for OSAd; ESPEN/EASO and SDOC for SO, associated with WHO osteopenia, respectively. Agreement was assessed with Cohen's Kappa, and the predictive discriminatory capability was evaluated by sensitivity, specificity, and accuracy, using impairment of physical function and the increased risk of fracture as reference standards.; Results: A total of 178 women were evaluated, with a mean age of 45.2 ± 9.6 years old and postoperative time of 6.6 ± 3.6 years. The prevalence of OSAd was 2.2% [Kelly]; 2.8% [ESPEN/EASO + WHO]; 6.2% [SDOC + WHO]. Moderate agreement was found between Kelly and ESPEN/EASO (k = 0.658, p < 0.001), but agreement with SDOC was null (k = 0.104, p = 0.114). All criteria demonstrated high specificity (94.0-98.2%) and low sensitivity (0.0-16.7%), with Kelly showing the highest accuracy (92.7%); Conclusions: Among the evaluated criteria, Kelly presented the highest accuracy and 2.2% of OSAd prevalence. Despite consistently high specificity, all criteria exhibited low sensitivity. These findings highlight the need for more sensitive diagnostic approaches for OSAd in postoperative RYGB populations.

Atorvastatin exerts a preventive effect against steroid-induced necrosis of the femoral head by modulating Wnt5a release

Steroid-induced osteonecrosis of the femoral head (SONFH) is a prevalent form of osteonecrosis in young individuals. More efficacious clinical strategies must be used to prevent and treat this condition. One of the mechanisms through which SONFH operates is the disruption of normal differentiation in bone marrow adipocytes and osteoblasts due to prolonged and extensive use of glucocorticoids (GCs). In vitro, it was observed that atorvastatin (ATO) effectively suppressed the impact of dexamethasone (DEX) on bone marrow mesenchymal stem cells (BMSCs), specifically by augmenting their lipogenic differentiation while impeding their osteogenic differentiation. To investigate the underlying mechanisms further, we conducted transcriptome sequencing of BMSCs subjected to different treatments, leading to the identification of Wnt5a as a crucial gene regulated by ATO. The analyses showed that ATO exhibited the ability to enhance the expression of Wnt5a and modulate the MAPK pathway while regulating the Wnt canonical signaling pathway via the WNT5A/LRP5 pathway. Our experimental findings provide further evidence that the combined treatment of ATO and DEX effectively mitigates the effects of DEX, resulting in the upregulation of osteogenic genes (Runx2, Alpl, Tnfrsf11b, Ctnnb1, Col1a) and the downregulation of adipogenic genes (Pparg, Cebpb, Lpl), meanwhile leading to the upregulation of Wnt5a expression. So, this study offers valuable insights into the potential mechanism by which ATO can be utilized in the prevention of SONFH, thereby holding significant implications for the prevention and treatment of SONFH in clinical settings.

Combined Effects of Cyclic Hypoxic and Mechanical Stimuli on Human Bone Marrow Mesenchymal Stem Cell Differentiation: A New Approach to the Treatment of Bone Loss

Background: The prevention and treatment of bone loss and osteoporotic fractures is a public health challenge. Combined with normobaric hypoxia, whole-body vibration has a high clinic potential in bone health and body composition. The effect of this therapy may be mediated by its action on bone marrow mesenchymal stem cells (MSCs). Objectives: Evaluate the effects of cyclic low-vibration stimuli and/or hypoxia on bone marrow-derived human MSC differentiation. Methods: MSCs were exposed four days per week, two hours/day, to hypoxia (3% O2) and/or vibration before they were induced to differentiate or during differentiation into osteoblasts or adipocytes. Gene and protein expression of osteoblastic, adipogenic, and cytoskeletal markers were studied, as well as extracellular matrix mineralization and lipid accumulation. Results: early osteoblastic markers increased in undifferentiated MSCs, pretreated in hypoxia and vibration. This pretreatment also increased mRNA levels of osteoblastic genes and beta-catenin protein in the early stages of differentiation into osteoblasts without increasing mineralization. When MSCs were exposed to vibration under hypoxia or normoxia during osteoblastic differentiation, mineralization increased with respect to cultures without vibrational stimuli. In MSCs differentiated into adipocytes, both in those pretreated as well as exposed to different conditions during differentiation, lipid formation decreased. Changes in adipogenic gene expression and increased beta-catenin protein were observed in cultures treated during differentiation. Conclusions: Exposure to cyclic hypoxia in combination with low-intensity vibratory stimuli had positive effects on osteoblastic differentiation and negative ones on adipogenesis of bone marrow-derived MSCs. These results suggest that in elderly or frail people with difficulty performing physical activity, exposure to normobaric cyclic hypoxia and low-density vibratory stimuli could improve bone metabolism and health.

Role of extracellular vesicles associated with microRNAs and their interplay with cuproptosis in osteoporosis

Osteoporosis (OP)-associated fractures can result in severe morbidity and disability, reduced quality of life, and death. Previous studies have suggested that small noncoding RNAs, for example, small regulatory microRNAs (miRNAs), play a key role in OP by inhibiting target gene expression. Cuproptosis, a recently proposed copper-induced cell death pathway, is linked with OP. Here, we describe the contribution of exosomal miRNAs and cuproptosis to OP. First, we highlight the characteristics of exosomes and roles of exosome-related miRNAs. Next, we discuss the relationship between cuproptosis and OP. Subsequently, we analyze the crosstalk of exosomal miRNAs with cuproptosis in the development of OP. This review aims to investigate a new clinical treatment method for OP.

Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and disease

Wnts are secreted, lipid-modified proteins that bind to different receptors on the cell surface to activate canonical or non-canonical Wnt signaling pathways, which control various biological processes throughout embryonic development and adult life. Aberrant Wnt signaling pathway underlies a wide range of human disease pathogeneses. In this review, we provide an update of Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and diseases. The Wnt proteins, receptors, activators, inhibitors, and the crosstalk of Wnt signaling pathways with other signaling pathways are summarized and discussed. We mainly review Wnt signaling functions in bone formation, homeostasis, and related diseases, and summarize mouse models carrying genetic modifications of Wnt signaling components. Moreover, the therapeutic strategies for treating bone diseases by targeting Wnt signaling, including the extracellular molecules, cytosol components, and nuclear components of Wnt signaling are reviewed. In summary, this paper reviews our current understanding of the mechanisms by which Wnt signaling regulates bone formation, homeostasis, and the efforts targeting Wnt signaling for treating bone diseases. Finally, the paper evaluates the important questions in Wnt signaling to be further explored based on the progress of new biological analytical technologies.

Bone-organ axes: bidirectional crosstalk

In addition to its recognized role in providing structural support, bone plays a crucial role in maintaining the functionality and balance of various organs by secreting specific cytokines (also known as osteokines). This reciprocal influence extends to these organs modulating bone homeostasis and development, although this aspect has yet to be systematically reviewed. This review aims to elucidate this bidirectional crosstalk, with a particular focus on the role of osteokines. Additionally, it presents a unique compilation of evidence highlighting the critical function of extracellular vesicles (EVs) within bone-organ axes for the first time. Moreover, it explores the implications of this crosstalk for designing and implementing bone-on-chips and assembloids, underscoring the importance of comprehending these interactions for advancing physiologically relevant in vitro models. Consequently, this review establishes a robust theoretical foundation for preventing, diagnosing, and treating diseases related to the bone-organ axis from the perspective of cytokines, EVs, hormones, and metabolites.

Associations of abdominal obesity with different types of bone fractures in adults: A systematic review and dose-response meta-analysis of prospective cohort studies

Findings on the association between abdominal obesity and hip fracture were summarized in a meta-analysis in 2017; however, no study has examined the dose-response association between abdominal fat indices and hip fracture. Also, we found no meta-analysis investigating other types of bone fractures including any vertebral fractures in relation to abdominal obesity. Therefore, the present systematic review and dose-response meta-analysis of prospective cohort studies were conducted to examine the association between abdominal obesity and different types of bone fractures. A comprehensive literature search was done by searching PubMed, Scopus, Web of Science, and Google Scholar until October 2021. In total, 23 articles from prospective cohort studies with a total sample size of 3,456,631 participants were included. During the follow-up periods ranging between 4 and 26 years, 137,989 cases of bone fracture were recorded. After comparing the highest and lowest categories of abdominal fat indices, the summary relative risks (RRs) of any, hip, and vertebral fractures were 0.99 (95% CI: 0.81-1.20), 1.09 (95% CI: 0.82-1.43), and 1.18 (95% CI: 1.05-1.33), respectively, indicating a significant positive association between abdominal obesity and risk of vertebral fracture. In the non-linear dose-response analysis, abdominal obesity based on the waist-to-hip ratio (WHR) was positively associated with an increased risk of hip fracture from 0.7 to 1.1 units of WHR. In the linear analysis, a 10 cm increase in waist circumference (WC) was associated with a 3% higher risk of vertebral fracture. We found no other dose-response association for other types of bone fractures. In conclusion, abdominal obesity may be associated with a higher risk of hip and vertebral fractures.

Links among Obesity, Type 2 Diabetes Mellitus, and Osteoporosis: Bone as a Target

Obesity, type 2 diabetes mellitus (T2DM) and osteoporosis are serious diseases with an ever-increasing incidence that quite often coexist, especially in the elderly. Individuals with obesity and T2DM have impaired bone quality and an elevated risk of fragility fractures, despite higher and/or unchanged bone mineral density (BMD). The effect of obesity on fracture risk is site-specific, with reduced risk for several fractures (e.g., hip, pelvis, and wrist) and increased risk for others (e.g., humerus, ankle, upper leg, elbow, vertebrae, and rib). Patients with T2DM have a greater risk of hip, upper leg, foot, humerus, and total fractures. A chronic pro-inflammatory state, increased risk of falls, secondary complications, and pharmacotherapy can contribute to the pathophysiology of aforementioned fractures. Bisphosphonates and denosumab significantly reduced the risk of vertebral fractures in patients with both obesity and T2DM. Teriparatide significantly lowered non-vertebral fracture risk in T2DM subjects. It is important to recognize elevated fracture risk and osteoporosis in obese and T2DM patients, as they are currently considered low risk and tend to be underdiagnosed and undertreated. The implementation of better diagnostic tools, including trabecular bone score, lumbar spine BMD/body mass index (BMI) ratio, and microRNAs to predict bone fragility, could improve fracture prevention in this patient group.

The effect of overweight or obesity on osteoporosis: A systematic review and meta-analysis

BACKGROUND

Osteoporosis and obesity are closely related, and the relationships between different types of obesity and osteoporosis are inconsistent.

OBJECTIVE

Our objective was to summarize earlier data concerning the association between osteoporosis and obesity (general and central), and to compare the impacts of these two obesity indicators on osteoporosis.

METHODS

From inception to May 2021, a comprehensive search in electronic bibliographic databases was conducted, and the search was updated in December 2021, July 2022 and June 2023. The data were independently extracted and evaluated by two investigators from epidemiological studies that reported the impact of obesity on the odds of incident osteoporosis.

RESULTS

There were 24 studies included in the final analysis when it came to general obesity measured by body mass index (BMI). Individuals with overweight and obesity had decreased odds of osteoporosis (odds ratio (OR), 0.451, 95% confidence intervals (CIs): 0.366-0.557). Sensitivity analyses showed that both overweight and obesity were decreased odds of osteoporosis, with reductions of 48.6% and 70.1%, respectively (OR, 0.514, 95% CI: 0.407-0.649; OR, 0.299, 95% CI: 0.207-0.433). Conversely, individuals classified as underweight were found to have higher odds of osteoporosis (OR, 2.540, 95% CI: 1.483-4.350). In term of central obesity, the final analysis consisted of 7 studies. No significant association was observed between central obesity and osteoporosis (OR, 0.913, 95% CI: 0.761-1.096).

CONCLUSIONS

General overweight and obesity were associated with lower odds of developing osteoporosis, whereas underweight was associated with higher odds. However, central obesity did not show a significant association with osteoporosis. These findings underscore the importance of considering the impact of obesity on osteoporosis. Further research is necessary to reinforce the evidence and validate our findings.

Vascular and lymphatic heterogeneity and age-related variations of dental pulps

OBJECTIVES

Dental pulp tissue is highly vascularized. However, age-related vascular changes of the dental pulp in mice and humans remain poorly understood. We modified a novel tissue clearing method, mapped the vasculature, pericytes, and perivascular matrix in the dental pulp via high-resolution 3D imaging.

METHODS

We isolated young and aged pulps from mouse teeth, and mapped vasculature through a high-resolution thick frozen sections imaging method and a modified tissue clearing method. Human dental pulps were also mapped for vasculature studying. Furthermore, young and aged human dental pulps were collected and were compared with mouse pulps through RNA- sequencing.

RESULTS

Five vascular subtypes of blood vessels were found in the mouse dental pulp, which constituted the arterioles-capillaries-venules network. The density of capillaries and venules of molars declined obviously in aged mice. Among the age-dependent changes in the perivascular pulp matrix, the perivascular macrophages remarkably increased, lymphatic capillaries increased, while the nerves and extracellular matrix remained unchanged. Furthermore, the vascular patterns of human formed a complex vascular network. Both mouse and human dental pulps exhibited an inflammaging state. TNF pathway and Rap1 pathway might become promising targets for combating inflammaging and promoting angiogenesis.

CONCLUSIONS

Five subtypes of blood vessels were identified within the dental pulp of mice. Notably, the density of capillaries and venules in pulps of aged mice was reduced. Furthermore, partial similarities were observed in the vascular patterns between the dental pulps of humans and mice. RNA-sequencing analysis revealed that both mouse and human dental pulps exhibit indications of an inflammaging state.

CLINICAL SIGNIFICANCE

This study may contribute to unraveling potential therapeutic targets in the pulp regeneration and treatment of relevant diseases in the elderly.

Understanding the Consequences of Fatty Bone and Fatty Muscle: How the Osteosarcopenic Adiposity Phenotype Uncovers the Deterioration of Body Composition

Adiposity is central to aging and several chronic diseases. Adiposity encompasses not just the excess adipose tissue but also body fat redistribution, fat infiltration, hypertrophy of adipocytes, and the shifting of mesenchymal stem cell commitment to adipogenesis. Bone marrow adipose tissue expansion, inflammatory adipokines, and adipocyte-derived extracellular vesicles are central to the development of osteopenic adiposity. Adipose tissue infiltration and local adipogenesis within the muscle are critical in developing sarcopenic adiposity and subsequent poorer functional outcomes. Ultimately, osteosarcopenic adiposity syndrome is the result of all the processes noted above: fat infiltration and adipocyte expansion and redistribution within the bone, muscle, and adipose tissues, resulting in bone loss, muscle mass/strength loss, deteriorated adipose tissue, and subsequent functional decline. Increased fat tissue, typically referred to as obesity and expressed by body mass index (the latter often used inadequately), is now occurring in younger age groups, suggesting people will live longer with the negative effects of adiposity. This review discusses the role of adiposity in the deterioration of bone and muscle, as well as adipose tissue itself. It reveals how considering and including adiposity in the definition and diagnosis of osteopenic adiposity, sarcopenic adiposity, and osteosarcopenic adiposity will help in better understanding the pathophysiology of each and accelerate possible therapies and prevention approaches for both relatively healthy individuals or those with chronic disease.

Association between lean body mass to visceral fat mass ratio and bone mineral density in United States population: a cross-sectional study

BACKGROUND

Studies have explored the correlation between body composition and bone mineral density (BMD), but there has yet to be a consensus. Thus, the present study aims to comprehensively investigate the association between lean body mass, adipose tissue, and BMD.

METHODS

We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES) (2011-2018) with 11,227 subjects. Multiple linear regression, smoothed curve fitting, threshold, and saturation effect analysis were used to explore the association between lean body mass, visceral fat mass, and BMD. Also, we used the lean body mass to visceral fat mass ratio (Log LM/VFM) as a proxy variable to analyze its association with BMD alone.

RESULTS

After adjusting for potential confounding factors, the results showed a positive correlation between lean mass and total BMD (for continuous: β = 0.078, P < 0.001; for quartile: β = 0.138, P < 0.001), while visceral fat mass was negatively correlated (for continuous: β = -0.027, P < 0.001; for quartile: β = -0.065, P < 0.001). A positive correlation was observed when the alternative variable Log LM/VFM was analyzed separately for its association with BMD (for continuous: β = 0.034, P < 0.001; for quartile: β = 0.084, P < 0.001). In addition, subgroup analyses for gender, age, body mass index, hypertension, and diabetes showed that all subgroups except the diabetes subgroup showed a substantial degree of robustness (P < 0.05). The smoothed curve fitting showed a nonlinear relationship between Log LM/VFM and BMD, and there was a threshold effect with a critical value of 2.60.

CONCLUSION

Maintaining a proper ratio of lean body mass and visceral fat mass is beneficial for increasing BMD.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

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.

Gender-specific associations between abdominal adipose mass and bone mineral density in the middle-aged US population

OBJECTIVES

The relationship between abdominal adipose tissue and osteoporosis is poorly understood. The purpose of this study was to examine the associations of abdominal adipose tissue with bone mineral density (BMD) among a nationally representative sample of US middle-aged adults.

MATERIAL AND METHODS

This study included 1498 participants from the National Health and Nutrition Examination Survey 2013-2014 and 2017-2018. Dual-energy x-ray absorptiometry was used to measure BMD at the lumbar spine and femoral neck, as well as to assess abdominal adipose mass by categorizing total adipose tissue (TAT) into visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT). Linear regression was used to assess the relationship between abdominal adipose tissue and BMD, and logistic regression and generalized additive model were used to assess the associations of abdominal adipose tissue with the development of low BMD.

RESULTS

In our study, men accounted for 51.3%, and the mean age and body mass index for men and women were 49.3 and 49.6 years, and 23.9 and 28.3 kg/m2, respectively. In the univariate model, we found that abdominal adipose mass was positively associated with BMD at femoral neck and spine in both genders. In the multivariate model, among men, a negative correlation was observed between TAT and SAT and BMD at the femoral neck. Additionally, higher masses of TAT, SAT, and VAT were found to significantly increase the risk of low BMD at both the femoral neck and lumbar spine. In contrast, there was no significant association between abdominal adipose mass and BMD in middle-aged women, regardless of menopausal status.

CONCLUSIONS

Our finding suggested that abdominal adipose tissue, regardless of its location (SAT or VAT), may have a negative impact on BMD in middle-aged men independently of body weight, but this relationship was not observed in women. Further research is needed to confirm these findings and investigate potential mechanisms underlying these associations.

TMT-based quantitative proteomic analysis revealed that FBLN2 and NPR3 are involved in the early osteogenic differentiation of mesenchymal stem cells (MSCs)

The delicate equilibrium between osteoblast and adipocyte differentiation of MSCs is highly regulated. We screened for early-stage osteogenesis- or adipogenesis-based MSCs protein expression profiles using TMT-based quantitative proteomic analysis to identify novel participating molecules. Protein annotation, hierarchical clustering, functional stratification, and protein-protein association assessments were performed. Moreover, two upregulated proteins, namely, FBLN2 and NPR3, were validated to participate in the osteogenic differentiation process of MSCs. After that, we independently downregulated FBLN2 and NPR3 over seven days of osteogenic differentiation, and we performed quantitative proteomics analysis to determine how different proteins were regulated in knockdown vs. control cells. Based on gene ontology (GO) and network analyses, FBLN2 deficiency induced functional alterations associated with biological regulation and stimulus-response, whereas NPR3 deficiency induced functional alterations related to cellular and metabolic processes, and so on. These findings suggested that proteomics remains a useful method for an in-depth study of the MSCs differentiation process. This will assist in comprehensively evaluating its role in osteoporosis and provide additional approaches for identifying as-yet-unidentified effector molecules.

MR-based techniques for intracortical vessel visualization and characterization: understanding the impact of microvascular disease on skeletal health

PURPOSE OF REVIEW

The relationships between bone vasculature and bone microstructure and strength remain incompletely understood. Addressing this gap will require in vivo imaging capabilities. We describe the relevant vascular anatomy of compact bone, review current magnetic resonance imaging (MRI)-based techniques that allow in vivo assessment of intracortical vasculature, and finally present preliminary studies that apply these techniques to investigate changes in intracortical vessels in aging and disease.

RECENT FINDINGS

Ultra-short echo time MRI (UTE MRI), dynamic contrast-enhanced MRI (DCE-MRI), and susceptibility-weighted MRI techniques are able to probe intracortical vasculature. Applied to patients with type 2 diabetes, DCE-MRI was able to find significantly larger intracortical vessels compared to nondiabetic controls. Using the same technique, a significantly larger number of smaller vessels was observed in patients with microvascular disease compared to those without. Preliminary data on perfusion MRI showed decreased cortical perfusion with age.

SUMMARY

Development of in vivo techniques for intracortical vessel visualization and characterization will enable the exploration of interactions between the vascular and skeletal systems, and further our understanding of drivers of cortical pore expansion. As we investigate potential pathways of cortical pore expansion, appropriate treatment and prevention strategies will be clarified.

Added value of waist circumference to body mass index for predicting fracture risk in obesity: a prospective study from the CARTaGENE cohort

Larger waist circumference is significantly associated with an increased risk of distal lower limb fractures in individuals aged 40-70 years with a body mass index within the normal or overweight category. Therefore, waist circumference provides additive information to body mass index for the identification of individuals at risk of obesity-related fractures.

INTRODUCTION

Waist circumference (WC) is a stronger risk factor of metabolic disorders than body mass index (BMI), but whether it holds true for fracture risk prediction remains unclear. We aimed to evaluate relationships between WC and fracture incidence within BMI categories and evaluate whether BMI modifies these relationships.

METHODS

Men and women aged 40-70 years from the CARTaGENE cohort were divided by BMI category at baseline: normal weight, overweight, and obesity. Incident fractures were identified over 7 years via linkage with healthcare administrative databases. Cox proportional hazard models estimated the relationships between WC and incident fractures at any site and by skeletal site within each BMI category. Results are reported as adjusted hazard ratios (95% confidence intervals) per 10 cm increase in WC. Effect modification was evaluated qualitatively by comparing relationships between BMI categories.

RESULTS

Of the 18 236 individuals included, 754 sustained a fracture. Significant relationships were found between WC and distal lower limb fractures in the normal (1.25 [1.08, 1.45]) and overweight (1.28 [1.07, 1.52]) BMI categories, but not in the obesity category. In the overweight category, we found an increased risk of distal upper limb fractures with increasing WC (1.49 [1.04, 2.15]). No significant relationship was observed regarding WC and fracture risk at any site or major osteoporotic fractures. An effect modification of BMI on the relationships between WC and distal lower limb fractures was observed.

CONCLUSION

WC provides both independent and additive information to BMI for the identification of individuals at risk of obesity-related fractures.

The Role of BIA Analysis in Osteoporosis Risk Development: Hierarchical Clustering Approach

Osteoporosis is a common musculoskeletal disorder among the elderly and a chronic condition which, like many other chronic conditions, requires long-term clinical management. It is caused by many factors, including lifestyle and obesity. Bioelectrical impedance analysis (BIA) is a method to estimate body composition based on a weak electric current flow through the body. The measured voltage is used to calculate body bioelectrical impedance, divided into resistance and reactance, which can be used to estimate body parameters such as total body water (TBW), fat-free mass (FFM), fat mass (FM), and muscle mass (MM). This study aims to find the tendency of osteoporosis in obese subjects, presenting a method based on hierarchical clustering, which, using BIA parameters, can group patients who show homogeneous characteristics. Grouping similar patients into clusters can be helpful in the field of medicine to identify disorders, pathologies, or more generally, characteristics of significant importance. Another added value of the clustering process is the possibility to define cluster prototypes, i.e., imaginary patients who represent models of "states", which can be used together with clustering results to identify subjects with similar characteristics in a classification context. The results show that hierarchical clustering is a method that can be used to provide the detection of states and, consequently, supply a more personalized medicine approach. In addition, this method allowed us to elect BIA as a potential prognostic and diagnostic instrument in osteoporosis risk development.

Role of Resistin in Various Diseases with Special Emphasis on Periodontal and Periapical Inflammation - A Review

Resistin is a small adipocyte-specific secretory hormone molecule. It has been associated with a number of cellular and metabolic processes. It has also been essentially implicated to have a vital role in the interplay between insulin resistance, obesity, and type II diabetes. Numerous clinical studies have demonstrated an association between many pathological illnesses with elevated serum resistin levels. It has also been shown to affect and modulate various molecular processes such as atherosclerosis, cancer cell metabolism, and inflammation. Periodontitis is a widespread inflammatory disease affecting human beings. Periapical periodontitis is an inflammatory disease that manifests as a sequela of untreated dental caries. Therefore, in this article, we summarize the divergent physiological roles played by resistin and its association with the mechanism of various pathologies. Moreover, current scientific studies discussing its association and role in common dental pathologies, periodontitis, and apical periodontitis are reviewed.

Enhanced efficiency of calcium-derived oleoyl serine on osteoporosis via Wnt/β-catenin pathway

Osteoporosis is a common disease of the elderly that affects millions of patients worldwide. It is mainly characterized by low bone mineral density and increased risk of fracture due to the deterioration of the bone structure, leading to difficulties in functional recovery, reduced quality of life, increased disability risk and mortality in the population. It has already been a major public health problem. Osteoporosis is a chronic disease that is difficult to treat in the elderly population, so it is crucial to develop new drugs for the treatment of osteoporosis. Oleoyl serine, an endogenous fatty acyl amide found in bone, has been shown to have excellent anti-osteoporosis effects, but it is easily hydrolyzed by amidases in vivo. The aim of this study is to determine the anti-osteoporotic effect of calcium-derived oleoyl serine, a novel oleoyl serine derivative and the molecular mechanism underneath. In vitro experiments demonstrated that calcium-derived oleoyl serine suppressed the expression of Fabp4, and Cebpα while Alp, and Runx2 was significantly upregulated compared with the oleoyl serine group and control. With the activation of β-catenin, calcium-derived oleoyl serine restored the abnormal osteogenesis and lipogenesis, indicating calcium-derived oleoyl serine compared with oleoyl serine has better effects on promoting osteogenesis and suppressing lipogenesis. In vivo experiment agreed with these findings that calcium-derived oleoyl serine promotes osteogenesis and suppresses its lipogenesis to ameliorate osteoporosis via a β-catenin dependent method. It is a new candidate for treating osteoporosis.

MiR-422a promotes adipogenesis via MeCP2 downregulation in human bone marrow mesenchymal stem cells

Methyl-CpG binding protein 2 (MeCP2) is a ubiquitous transcriptional regulator. The study of this protein has been mainly focused on the central nervous system because alterations of its expression are associated with neurological disorders such as Rett syndrome. However, young patients with Rett syndrome also suffer from osteoporosis, suggesting a role of MeCP2 in the differentiation of human bone marrow mesenchymal stromal cells (hBMSCs), the precursors of osteoblasts and adipocytes. Here, we report an in vitro downregulation of MeCP2 in hBMSCs undergoing adipogenic differentiation (AD) and in adipocytes of human and rat bone marrow tissue samples. This modulation does not depend on MeCP2 DNA methylation nor on mRNA levels but on differentially expressed miRNAs during AD. MiRNA profiling revealed that miR-422a and miR-483-5p are upregulated in hBMSC-derived adipocytes compared to their precursors. MiR-483-5p, but not miR-422a, is also up-regulated in hBMSC-derived osteoblasts, suggesting a specific role of the latter in the adipogenic process. Experimental modulation of intracellular levels of miR-422a and miR-483-5p affected MeCP2 expression through direct interaction with its 3' UTR elements, and the adipogenic process. Accordingly, the knockdown of MeCP2 in hBMSCs through MeCP2-targeting shRNA lentiviral vectors increased the levels of adipogenesis-related genes. Finally, since adipocytes released a higher amount of miR-422a in culture medium compared to hBMSCs we analyzed the levels of circulating miR-422a in patients with osteoporosis-a condition characterized by increased marrow adiposity-demonstrating that its levels are negatively correlated with T- and Z-scores. Overall, our findings suggest that miR-422a has a role in hBMSC adipogenesis by downregulating MeCP2 and its circulating levels are associated with bone mass loss in primary osteoporosis.

Recent advances in the application of ionomics in metabolic diseases

Trace elements and minerals play a significant role in human health and diseases. In recent years, ionomics has been rapidly and widely applied to explore the distribution, regulation, and crosstalk of different elements in various physiological and pathological processes. On the basis of multi-elemental analytical techniques and bioinformatics methods, it is possible to elucidate the relationship between the metabolism and homeostasis of diverse elements and common diseases. The current review aims to provide an overview of recent advances in the application of ionomics in metabolic disease research. We mainly focuses on the studies about ionomic or multi-elemental profiling of different biological samples for several major types of metabolic diseases, such as diabetes mellitus, obesity, and metabolic syndrome, which reveal distinct and dynamic patterns of ion contents and their potential benefits in the detection and prognosis of these illnesses. Accumulation of copper, selenium, and environmental toxic metals as well as deficiency of zinc and magnesium appear to be the most significant risk factors for the majority of metabolic diseases, suggesting that imbalance of these elements may be involved in the pathogenesis of these diseases. Moreover, each type of metabolic diseases has shown a relatively unique distribution of ions in biofluids and hair/nails from patients, which might serve as potential indicators for the respective disease. Overall, ionomics not only improves our understanding of the association between elemental dyshomeostasis and the development of metabolic disease but also assists in the identification of new potential diagnostic and prognostic markers in translational medicine.

Metabolically favorable adiposity and bone mineral density: a Mendelian randomization analysis

OBJECTIVE

This analysis assessed the putative causal association between genetically predicted percent body fat and areal bone mineral density (aBMD) and, more specifically, the association between genetically predicted metabolically "favorable adiposity" (MFA) and aBMD at clinically relevant bone sites.

METHODS

Mendelian randomization was used to assess the relationship of MFA and percent body fat with whole-body, lumbar spine, femoral neck, and forearm aBMD. Sex-stratified and age-stratified exploratory analyses were conducted.

RESULTS

In all MR analyses, genetically predicted MFA was inversely associated with aBMD for the whole body (β = -0.053, p = 0.0002), lumbar spine (β = -0.075; p = 0.0001), femoral neck (β = -0.045; p = 0.008), and forearm (β = -0.115; p = 0.001). This negative relationship was strongest in older individuals and did not differ by sex. The relationship between genetically predicted percent body fat and aBMD was nonsignificant across all Mendelian randomization analyses. Several loci that were associated at a genome-wide significance level (p < 5 × 10^-8 ) in opposite directions with body fat and aBMD measures were also identified.

CONCLUSIONS

This study did not support the hypothesis that MFA protects against low aBMD. Instead, it showed that MFA may result in lower aBMD. Further research is needed to understand how MFA affects aBMD and other components of bone health such as bone turnover, bone architecture, and osteoporotic fractures.

Altered bone and body composition in children and adolescents with confirmed prenatal alcohol exposure

Prenatal alcohol exposure can contribute to long term adverse health outcomes. Development of the skeletal system begins at the early embryonic stage and continues into early adulthood but the effect of prenatal alcohol exposure on skeletal growth is relatively unexplored in a clinical population. Here, we performed dual X-ray absorptiometry to examine bone, fat, and muscle accrual in children and adolescents diagnosed with, or at risk of, fetal alcohol spectrum disorders (FASDs). Children (aged 4-9 years) with FASD or at risk of FASD (n = 10) had similar growth to age matched controls (n = 27). By adolescence (aged ≥10 years), those with FASDs (n = 13) were shorter and had lower areal bone mineral density and lean tissue mass than typically developing peers (n = 29). Overall, adolescents diagnosed with FASDs had greater odds of impairments to bone and body composition. These findings highlight the importance of early FASD diagnosis and appropriate post-diagnostic medical follow-up to enable timely, effective interventions to optimize bone and body composition during paediatric growth.

Hyunganol II Exerts Antiadipogenic Properties via MAPK-Mediated Suppression of PPARγ Expression in Human Bone Marrow-Derived Mesenchymal Stromal Cells

Bone marrow adiposity has been associated with several metabolic syndromes such as diabetes and osteoporosis. Imbalance in adipogenic and osteoblastogenic differentiation of human bone marrow mesenchymal stromal cells (hBM-MSCs) was suggested to be the cause of elevated bone marrow adiposity. There are several drugs, of both natural and synthetic origin, to treat bone loss. In this study, as a part of a recent trend to discover natural products with more biocompatibility and fewer side effects to treat bone loss, the effect of hyunganol II (HNG), a coumarin isolated from Corydalis heterocarpa, on hBM-MSC adipogenesis was investigated. Cells treated with HNG showed decreased lipid accumulation indicating a diminished adipocyte phenotype. Treatment with HNG also suppressed the mRNA and protein expressions of PPARγ, C/EBPα, and SREBP1c, and three adipogenic marker genes. Further analysis of MAPK signaling pathway exhibited that HNG treatment elevated ERK activation and suppressed the JNK-mediated cFos and cJun phosphorylation, which inhibits PPARγ transcriptional activity. Taken together, HNG treatment was shown to inhibit adipogenesis via suppressed PPARγ expression as a result of altered MAPK signaling. Therefore, it was suggested that HNG might prevent bone marrow adiposity by inhibiting hBM-MSC adipogenesis and can be utilized as a drug or nutraceutical with beneficial effects on bone. Thus, further studies should be conducted to analyze its effect in vivo.

Oestrogen enforces the integrity of blood vessels in the bone during pregnancy and menopause

The mammalian skeletal system shows sex differences in structure, functions, ageing and disease incidences. The role of blood vessels in physiological, regenerative and pathological bone functions indicates the requisite to understanding their sex specificity. Here, we find oestrogen regulates blood vessel physiology during pregnancy and menopause through oestrogen receptor alpha (ERα) and G-protein coupled oestrogen receptor-1 (Gper1) but not ERβ-dependent signalling in mice. Oestrogen regulates BECs' lipid use and promotes lipolysis of adipocytes and FA uptake from the microenvironment. Low oestrogen conditions skew endothelial FA metabolism to accumulate lipid peroxides (LPO), leading to vascular ageing. High ferrous ion levels in female BECs intensify LPO accumulation and accelerate the ageing process. Importantly, inhibiting LPO generation using liproxstatin-1 in aged mice significantly improved bone heath. Thus, our findings illustrate oestrogen's effects on BECs and suggest LPO targeting could be an efficient strategy to manage blood and bone health in females.

The Association of Lipids and Lipoproteins with Hip Fracture Risk: The Cardiovascular Health Study

BACKGROUND

It is uncertain if lipids or lipoproteins are associated with osteoporotic fractures. In this study, incident hip fracture risk according to conventional lipid levels and lipoprotein levels and sizes was examined.

METHODS

We followed 5832 participants aged ≥65 years from the Cardiovascular Health Study for hip fracture for a mean of 13.5 (SD 5.7) years. Standard enzymatic methods were used to determine lipid levels (ie, high-density lipoprotein-cholesterol [HDL-c], low-density lipoprotein-cholesterol [LDL-c], and triglycerides). Nuclear magnetic resonance spectroscopy was used to measure lipoprotein fractions (ie, very-low-density lipoprotein-particle [VLDL-P], low-density lipoprotein-particle [LDL-P], high-density lipoprotein-particle [HDL-P]) in a subset of 1849 participants.

RESULTS

We documented 755 incident hip fractures among women (1.19 fractures per 100 participant years [95% confidence interval, 1.04, 1.35]) and 197 among men (0.67 fractures per 100 participant years [95% CI, 0.41, 1.10]) over an average follow-up. HDL-c and LDL-c levels had statistically significant nonlinear U-shaped relationships with hip fracture risk (HDL-c, P = .009; LDL-c, P = .02). Triglyceride levels were not significantly associated with hip fracture risk. In fully adjusted conjoint models, higher VLDL-P concentration (hazard ratio [HR] per 1 standard deviation [SD] increment 1.47 [1.13, 1.91] and size [HR per 1 SD increment 1.24 [1.05, 1.46]) and higher high-density lipoprotein particle size (HR per 1 SD increment 1.81 [1.25, 2.62]) were all associated with higher hip fracture risk.

CONCLUSIONS

Lipids and lipoproteins are associated with hip fracture risk in older adults. The associations are complex. Mechanistic studies are needed to understand these findings.

People living with HIV have low trabecular bone mineral density, high bone marrow adiposity, and poor trabecular bone microarchitecture at the proximal femur

People living with HIV (PLWH) have increased risk of osteoporosis and fractures. We assessed the proximal femur of PLWH and age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging. Results suggest that the trabecular compartment is compromised at fracture-prone regions in the proximal femur of PLWH.

INTRODUCTION

People living with HIV (PLWH) have increased risk of osteoporosis and fractures. However, studies assessing the main determinants of bone strength in the proximal femur exclude this vulnerable population. We assessed the proximal femur of 40 PLWH and 26 age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging.

METHODS

We examined cortical volumetric bone mineral density (Ct.vBMD), trabecular vBMD (Tb.vBMD), cortical thickness (Ct.Th), bone marrow adiposity (BMA), and trabecular number, separation, and bone volume fraction. Parametric comparisons between the two groups were made for the femoral head, femoral neck, trochanter, and total hip using linear regression adjusting for several covariates, including metrics of body composition. In addition, we investigated the associations of BMA with Tb.vBMD and trabecular microarchitecture with Spearman's rank partial correlations.

RESULTS

PLWH had lower Tb.vBMD and deteriorated trabecular microarchitecture in the femoral neck, trochanter and total hip, and elevated BMA in the femoral head, femoral neck, and total hip. Ct.vBMD and Ct.Th were not significantly different between the two groups. BMA was significantly associated with lower Tb.vBMD and deteriorated trabecular microarchitecture in both groups albeit at different femoral regions.

CONCLUSIONS

Our findings suggest that the trabecular, and not the cortical, compartment is compromised in the proximal femur of PLWH. The observed impairments in fracture-prone regions in PLWH indicate lower femoral strength and suggest higher fracture risk. The inverse associations of BMA with trabecular bone density and microarchitecture quality agree with findings at other anatomic sites and in other populations, suggesting that excess BMA possibly due to a switch from the osteoblast to the adipocyte lineage may be implicated in the pathogenesis of bone fragility at the femur in PLWH.

Linagliptin in Combination With Metformin Ameliorates Diabetic Osteoporosis Through Modulating BMP-2 and Sclerostin in the High-Fat Diet Fed C57BL/6 Mice

BACKGROUND

Diabetic osteoporosis is a poorly managed serious skeletal complication, characterized by high fracture risk, increased bone resorption, reduced bone formation, and disrupted bone architecture. There is a need to investigate drugs that can improve bone health along with managing glycemic control. DPP-4 inhibitors and metformin have proven benefits in improving bone health. Here, we investigated the effects of linagliptin, a DPP inhibitor, and metformin alone and in combination to treat diabetic osteoporosis in high-fat-fed mice.

METHODS

C57BL/6 mice were kept on the high-fat diet (HFD) for 22 weeks to induce diabetic osteoporosis. Linagliptin (10mg/Kg), metformin (150mg/Kg), and their combination were orally administered to the diabetic mice from the 18th-22nd week. Femur and tibial bone microarchitecture together with bone mineral density (BMD) were evaluated using µCT and histopathological changes were assessed. Further, bone turnover biomarkers namely bone morphogenetic protein-2 (BMP-2), sclerostin, tartrate-resistant acid phosphatase (TRAP), osteocalcin, alkaline phosphatase (ALP), calcium, and pro-inflammatory cytokines were assessed. Additionally, metabolic parameters including body weight, fasting blood glucose (FBG), glucose & insulin tolerance, lipids profile, and leptin were measured.

RESULTS

HFD feeding resulted in impaired bone microarchitecture, reduced BMD, distorted bone histology, and altered bone turnover biomarkers as indicated by the significant reduction in bone ALP, BMP-2, osteocalcin, and an increase in sclerostin, TRAP, and serum calcium. Interestingly, treatment with linagliptin and its combination with metformin significantly reverted the impaired bone architecture, BMD, and positively modulated bone turnover biomarkers, while metformin alone did not exhibit any significant improvement. Further, HFD induced diabetes and metabolic abnormalities (including an increase in body weight, FBG, impaired glucose and insulin tolerance, leptin, triglycerides, cholesterol), and pro-inflammatory cytokines (TNF-alpha and IL-1β) were successfully reversed by treatment with linagliptin, metformin, and their combination.

CONCLUSION

Linagliptin and its combination with metformin successfully ameliorated diabetic osteoporosis in HFD-fed mice possibly through modulation of BMP-2 and sclerostin. The study provides the first evidence for the possible use of linagliptin and metformin combination for managing diabetic osteoporosis.

General and abdominal obesity operate differently as influencing factors of fracture risk in old adults

To infer the causality between obesity and fracture and the difference between general and abdominal obesity, a prospective study was performed in 456,921 participants, and 10,142 participants developed an incident fracture with follow-up period of 7.96 years. A U-shape relationship was observed between BMI and fracture, with the lowest risk of fracture in overweight participants. The obesity individuals had higher fracture risk when BMD was adjusted, and the protective effect of moderate-high BMI on fracture was mostly mediated by bone mineral density (BMD). However, for abdominal obesity, the higher WCadjBMI (linear) and HCadjBMI (J-shape) were found to be related to higher fracture risk, and less than 30% of the effect was mediated by BMD. By leveraging genetic instrumental variables, it provided additional evidences to support the aforementioned findings. In conclusion, keeping moderate-high BMI might be of benefit to old people in terms of fracture risk, whereas abdominal adiposity might increase risk of fracture.

Subcutaneous adipose tissue is a positive predictor for bone mineral density in prepubertal children with Prader-Willi syndrome independent of lean mass

OBJECTIVES

Emerging evidence suggests a fat depot-specific relationship with bone mineral density (BMD) in children, particularly in those who are overweight/obese. However, this has not yet been investigated in detail in children with Prader-Willi syndrome (PWS), a genetic syndrome characterized by a decreased lean mass (LM) and increased fat mass (FM). The objective of this study is to investigate the relationships of LM and FM, particularly fat distribution, with bone mineral parameters.

METHODS

This is a retrospective and cross-sectional study. Forty-seven prepubertal Japanese children with PWS (22 males, mean age: 6.86 years) were included. No subjects had type 2 diabetes mellitus or osteoporotic medications. LM, FM, and BMD and bone mineral content in the total body less head and the lumbar spine were measured using dual-energy x-ray absorptiometry, in addition to subcutaneous/visceral adipose tissue (SAT/VAT), and the ratio of VAT to SAT (V/S) by computed tomography at the umbilical level. Bone mineral apparent density was calculated to correct for bone size.

RESULTS

LM positively correlated with bone mineral parameters after controlling for age, sex, growth hormone (GH) treatment, and FM. Although FM did not correlate with bone mineral parameters, compartment-specific analysis revealed that SAT positively and V/S negatively correlated with bone mineral parameters after controlling for age, sex, GH treatment and LM.

CONCLUSIONS

A compartment-specific effect of FM on bone mineral parameters was noted such that SAT was a positive predictor for BMD independent of LM in prepubertal children with PWS.

Opportunistic Use of Lumbar Magnetic Resonance Imaging for Osteoporosis Screening

Magnetic resonance imaging (MRI) is a routine assessment before spine surgery. We found that the opportunistic use of MRI with the vertebral bone quality (VBQ) score has good diagnostic ability, with a threshold value of VBQ > 3.0, in recognizing patients who may need further osteoporosis evaluation.

INTRODUCTION

The purpose of this study was to determine whether the opportunistic use of magnetic resonance imaging (MRI) is useful for identifying spine surgical patients who need further osteoporosis evaluation.

METHODS

This retrospective study evaluated 83 thoracolumbar spine surgery patients age ≥ 50 who received T1-weighted MRI. Opportunistic MRI was evaluated with the vertebral bone quality (VBQ) score, VBQ (fat) score, and signal-to-noise ratio (SNR). Each uses the median L1-L4 vertebral body signal intensities (SI) divided by either the L3 cerebrospinal fluid (CSF) SI, average SI of the L1 and S1 dorsal fat, or standard deviation (SD) of the background SI dorsal to the skin. Single-level VBQ was calculated as the ratio of the L1 vertebral body and L1 CSF SIs. Receiver-operator curve analysis was performed to determine diagnostic ability.

RESULTS

The mean age was 70.10, 80% were female, and 96% were Caucasian. The mean ± SD VBQ, single-level VBQ, VBQ (fat), and SNR were 3.39 ± 0.68, 3.56 ± 0.81, 3.95 ± 1.89, and 113.18 ± 77.26, respectively. Using area under the curve, the diagnostic ability of VBQ, single-level VBQ, VBQ (fat), and SNR for clinical osteoporosis were 0.806, 0.779, 0.608, and 0.586, respectively. Diagnostic threshold values identified with optimal sensitivity and specificity were VBQ of 2.95 and single-level VBQ of 3.06.

CONCLUSION

Opportunistic use of MRI is a simple, effective tool that may help recognize patients who are at risk for complications related to bone disease. A VBQ > 3.0 can identify patients who need additional diagnostic evaluation.

Pathophysiological aspects of insulin resistance in Atrial Fibrillation: novel therapeutic approaches

Background

Insulin resistance is associated with metabolic disorders including diabetes, obesity, hypertension, and inflammation which are the risk factors for Atrial Fibrillation. Many studies have reported that type 2 diabetes and AF are related and also their prevalence is increasing globally. Moreover, insulin resistance begins the type 2 diabetes.

Main body

This review explains the pathophysiological aspects of insulin resistance in AF patients and discusses the drugs that are used to manage insulin resistance including Biguanides (metformin), thiazolidinediones (TZDs) [Pioglitazone, rosiglitazone], Sodium-glucose cotransporter 2 (SGLT2) inhibitors, Concentrated Insulin Products, Dipeptidyl peptidase-4 (DPP-4) Inhibitors, Glucagon-like peptide 1 (GLP-1) receptor Agonists, Pramlintide, Sulfonylureas, Meglitinides, α-Glucosidase Inhibitors, Colesevelam, Bromocriptine. This review will highlight a few major drugs that played a significant role in AF patients. For this purpose, many databases were used for reviewing the literature and keywords are used such as Insulin Resistance, Pathophysiology, Atrial Fibrillation, and Drugs.

Conclusion

This review article concludes that insulin resistance is related to AF. It also provides an outlook on the recent pathophysiological aspects of insulin resistance in AF; however, more studies are needed to clarify the management of insulin resistance in AF patients to prevent the development of type 2 diabetes.

Sarcopenic obesity defined by visceral adiposity was associated with osteoporotic vertebral fracture

BACKGROUND

Previous studies have reported that the fracture risk related to sarcopenic obesity (SO) may be influenced by the distribution of fat mass. Therefore, it is useful to explore a body component suitable for defining obesity when predicting fracture risk. This study was an attempt to explore the contribution of SO defined by visceral adiposity on the incidence of osteoporotic fracture.

METHODS

We enrolled 736 Chinese patients aged > 60 years in this prospective study. Sarcopenia was defined as low skeletal muscle index (SMI) with muscle strength or low SMI with low physical performance. Obesity was categorized as follows: (1) android to gynoid ratio (A/G ratio, men > 0.82, women > 0.65) as an indicator of visceral adiposity; (2) body fat percentage (men > 27.8%; women > 34.5%); and (3) body mass index (≥ 25 kg/m²). A Cox proportional hazard model was used to determine the association between SO and the risk of osteoporotic fracture.

RESULTS

The incidence of SO was 8.7%; 9.0% in females and 8.1% in males. Of 223 (30.2%) patients with self-reported fractures. SO classified by A/G was associated with an increased risk of osteoporotic vertebral fracture (HR: 1.71, 95% CI: 1.07-2.72). High SMI was associated with a reduced risk of osteoporotic vertebral fracture (HR: 0.82, 95% CI: 0.72-0.93), higher BMI was associated with a higher risk vertebral fracture (HR: 1.12, 95% CI: 0.94-1.63), and higher A/G ratio was associated with a higher risk of any fracture (HR: 1.28, 95% CI: 1.14-1.43) and osteoporotic vertebral fracture (HR: 1.19, 95% CI: 1.05-1.36).

CONCLUSIONS

Our findings suggest that SO, defined by visceral adiposity, was associated with the risk of osteoporotic vertebral fracture. Moreover, low SMI, low muscle strength and visceral adiposity were independently associated with osteoporotic fracture.

The Implications of Bone Marrow Adipose Tissue on Inflammaging

Once considered an inert filler of the bone cavity, bone marrow adipose tissue (BMAT) is now regarded as a metabolically active organ that plays versatile roles in endocrine function, hematopoiesis, bone homeostasis and metabolism, and, potentially, energy conservation. While the regulation of BMAT is inadequately understood, it is recognized as a unique and dynamic fat depot that is distinct from peripheral fat. As we age, bone marrow adipocytes (BMAds) accumulate throughout the bone marrow (BM) milieu to influence the microenvironment. This process is conceivably signaled by the secretion of adipocyte-derived factors including pro-inflammatory cytokines and adipokines. Adipokines participate in the development of a chronic state of low-grade systemic inflammation (inflammaging), which trigger changes in the immune system that are characterized by declining fidelity and efficiency and cause an imbalance between pro-inflammatory and anti-inflammatory networks. In this review, we discuss the local effects of BMAT on bone homeostasis and the hematopoietic niche, age-related inflammatory changes associated with BMAT accrual, and the downstream effect on endocrine function, energy expenditure, and metabolism. Furthermore, we address therapeutic strategies to prevent BMAT accumulation and associated dysfunction during aging. In sum, BMAT is emerging as a critical player in aging and its explicit characterization still requires further research.

Gender and Body Mass Index-Related Serum Level of Adipokines and Metabolic Syndrome Components in Bipolar Patients who received Lithium and Valproic Acid

Background: This is the study to assess alterations on adiponectin, leptin, and metabolic syndrome components in women and men bipolar disorder (BD) patients with normal weight and obesity who received valproic acid (VPA) and lithium (Li). Methods: Thirty-six women and 51 men were included. Commercial kits were used to determine all parameters. Metabolic syndrome components were determined according to the NCEP ATP III criteria. Results: Patients who received Li and VPA significantly differ in waist circumference (WC) and triglyceride (TG) levels (in women and men). Normal weight patients received both drugs, significant differences were considered in high-density lipoprotein-cholesterol (HDL-C), WC, and TG levels compared to healthy controls, but there were significant differences in TG, leptin, and adiponectin levels in obese patients who received VPA. There were significant negative and positive correlation between leptin and adiponectin and WC and TG in women and men BD patients treated with VPA and Li. There were significant positive correlation between leptin and adiponectin and WC and TG and significant negative correlation with HDL-C in normal weight BD patients treated with VPA and Li, respectively, while there was only a significant positive correlation between leptin and adiponectin, and TG in obese BD patients treated with VPA. Conclusions: It looks like that patients treated with both drugs for our suggested time may increase leptin and adiponectin levels. Correlation differences between leptin and adiponectin, and metabolic syndrome components may be important parameters in women, men, normal weight, and obese BD patients. Monitoring of body composition and adipokines may benefit in medical care of these patients.

Promotion of osteogenesis by Sweroside via BMP2-involved signaling in postmenopausal osteoporosis

Phlomis umbrosa has been traditionally used for bone diseases in traditional Korean Medicine. Sweroside (SOS), marker compounds of P. umbrosa, has been known to promote osteoblast differentiation. In this study, ameliorative effects of SOS on osteoporosis and potential target pathway were investigated. Ovariectomized mice were administered three doses of SOS three times a week for 4 weeks after inducing osteoporosis. Bone mineral content (BMC) and bone mineral density (BMD) were analyzed by dual energy X-ray absorptiometry. A human osteosarcoma cell line (SaOS-2) was differentiated to clarify the promoting effects of SOS on osteoblast differentiation and bone formation. Osteoblastic bone-forming markers were evaluated in lumbar vertebrae (LV) and mineralized SaOS-2 cells. SOS markedly elevated BMC and BMD levels and attenuated the bone marrow adipocytes in the femoral shaft. SOS increased the formation of bone matrix in SaOS-2 cells. Bone morphogenetic protein-2 (BMP2) and runt-related transcription factor 2 (CBFA1) in LV and SaOS-2 cells were up-regulated by SOS. SOS increased alkaline phosphatase (ALPL), osteopontin (SPP1), and bone sialoprotein-1 (BSPH1). In conclusion, SOS induced the formation of mineralized bone matrix by regulating BMP2/CBFA1-mediated molecules. Therefore, SOS could be a therapeutic compound of treatment for osteoporosis by producing the new bone matrix.

Bone Mineral Density in Congenital Generalized Lipodystrophy: The Role of Bone Marrow Tissue, Adipokines, and Insulin Resistance

Congenital Generalized Lipodystrophy (CGL) is a rare syndrome characterized by the almost total absence of subcutaneous adipose tissue due to the inability of storing lipid in adipocytes. Patients present generalized lack of subcutaneous fat and normal to low weight. They evolve with severe metabolic disorders, non-alcoholic fatty liver disease, early cardiac abnormalities, and infectious complications. Although low body weight is a known risk factor for osteoporosis, it has been reported that type 1 and 2 CGL have a tendency of high bone mineral density (BMD). In this review, we discuss the role of bone marrow tissue, adipokines, and insulin resistance in the setting of the normal to high BMD of CGL patients. Data bases from Pubmed and LILACS were searched, and 113 articles published until 10 April 2021 were obtained. Of these, 76 were excluded for not covering the review topic. A manual search for additional literature was performed using the bibliographies of the studies located. The elucidation of the mechanisms responsible for the increase in BMD in this unique model of insulin resistance may contribute to the understanding of the interrelationships between bone, muscle, and adipose tissue in a pathophysiological and therapeutic perspective.

Differential Iron Requirements for Osteoblast and Adipocyte Differentiation

Bone marrow mesenchymal progenitor cells are precursors for various cell types including osteoblasts, adipocytes, and chondrocytes. The external environment and signals act to direct the pathway of differentiation. Importantly, situations such as aging and chronic kidney disease display alterations in the balance of osteoblast and adipocyte differentiation, adversely affecting bone integrity. Iron deficiency, which can often occur during aging and chronic kidney disease, is associated with reduced bone density. The purpose of this study was to assess the effects of iron deficiency on the capacity of progenitor cell differentiation pathways. Mouse and human progenitor cells, differentiated under standard osteoblast and adipocyte protocols in the presence of the iron chelator deferoxamine (DFO), were used. Under osteogenic conditions, 5μM DFO significantly impaired expression of critical osteoblast genes, including osteocalcin, type 1 collagen, and dentin matrix protein 1. This led to a reduction in alkaline phosphatase activity and impaired mineralization. Despite prolonged exposure to chronic iron deficiency, cells retained viability as well as normal hypoxic responses with significant increases in transferrin receptor and protein accumulation of hypoxia inducible factor 1α. Similar concentrations of DFO were used when cells were maintained in adipogenic conditions. In contrast to osteoblast differentiation, DFO modestly suppressed adipocyte gene expression of peroxisome-proliferating activated receptor gamma, lipoprotein lipase, and adiponectin at earlier time points with normalization at later stages. Lipid accumulation was also similar in all conditions. These data suggest the critical importance of iron in osteoblast differentiation, and as long as the external stimuli are present, iron deficiency does not impede adipogenesis. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Habitual use of fish oil supplements, genetic predisposition, and risk of fractures: a large population-based study

BACKGROUND

Epidemiologic studies have suggested an inverse association between circulating concentrations of long-chain ω-3 PUFAs and fracture risk. However, whether supplementation of long-chain ω-3 PUFA (i.e. fish oil) is associated with fracture risk, and whether the association is modified by genetic predisposition to fracture risk remain unclear.

OBJECTIVES

To evaluate the associations of habitual fish oil supplement use with fracture risk, and to explore the potential effect modification by genetic predisposition.

METHODS

This study included 492,713 participants from the UK Biobank who completed a questionnaire on habitual fish oil supplement use between 2006 and 2010. HRs and 95% CIs for fractures were estimated from multivariable Cox proportional hazards models. A weighted fracture-genetic risk score (GRS) was derived from 14 validated single nucleotide polymorphisms.

RESULTS

During a median follow-up of 8.1 y, 12,070 incident fractures occurred among participants free of fracture at baseline (n = 441,756). Compared with nonuse, habitual use of fish oil supplements was associated with a lower risk of total fractures (HR = 0.93; 95% CI: 0.89, 0.97), hip fractures (HR = 0.83; 95% CI: 0.75, 0.92), and vertebrae fractures (HR = 0.85; 95% CI: 0.72, 0.99). The inverse association for total fractures was more pronounced among participants having a higher fracture-GRS than among those with a lower fracture-GRS (P-interaction <0.001). Among participants with a history of fracture at baseline (n = 50,957), fish oil use was associated with a lower risk of total recurrent fractures (HR = 0.88; 95% CI: 0.82, 0.96) and vertebrae recurrent fractures (HR = 0.64; 95% CI: 0.46, 0.88) but not with hip fracture recurrence.

CONCLUSIONS

Our findings suggest that habitual fish oil supplement use is associated with lower risks of both incident and recurrent fractures. The inverse associations of fish oil use with total fractures appeared to be more pronounced among individuals at higher genetic risk of fractures than those with lower genetic risk.