Obesity and fractures

Effects of Pregnancy and Lactation on Bone Microstructure and Material Properties in a Rat Model of Bariatric Surgery

Obesity is a major public health issue worldwide. Despite various approaches to weight loss, the most effective technique for reducing obesity, as well as diabetes and associated diseases, is bariatric surgery. Increasingly, young women without children are undergoing bariatric surgery, vertical sleeve gastrectomy (VSG) being the most common procedure nowadays. However, despite several reports suggesting bone loss after VSG, little is known about the potential additive effects of gestation and lactation after VSG to bone health. This study investigated the combined effects of pre-gestational VSG and subsequent gestation/lactation on bone metabolism in a rat model fed a high fat high sugar (HFHS) diet, with a focus on bone biomechanics, mass, microarchitecture and material properties. Furthermore, bone mass and remodelling were followed longitudinally by microCT prior to surgery, 4 weeks post-surgery, after weaning and at sacrifice. Significant alterations in bone mass and microarchitecture, characterized by changes in trabecular thickness and number, as well as changes in bone formation and resorption were influenced by both surgery and reproductive demands. Mechanical testing at sacrifice demonstrated compromised long bone fragility, in rat with HFHS regardless of the surgical procedure (Sham or VSG). Furthermore, analysis of bone material properties highlighted potential disruptions in the pattern of bone mineralization in sham and VSG animals fed a HFHS diet. These findings underscore the complex interplay between pre-gestational VSG and subsequent gestation/lactation in modulating bone metabolism in the investigated rat model. The preclinical rat model may help with optimizing surgical strategies and developing targeted interventions to mitigate potential bone-related complications associated with VSG in reproductive-aged individuals.

Ectopic fat in muscle and poor glycemic control are negatively associated with trabecular bone score in type 2 diabetes

INTRODUCTION

Type 2 Diabetes (T2D) is associated with fractures, despite preserved Bone Mineral Density (BMD). This study aimed to evaluate the relationship between BMD and trabecular bone score (TBS) with the reallocation of fat within muscle in individuals with eutrophy, obesity, and T2D.

METHODS

The subjects were divided into three groups: eutrophic controls paired by age and sex with the T2D group (n = 23), controls diagnosed with obesity paired by age, sex, and body mass index with the T2D group (n = 27), and the T2D group (n = 29). BMD and body fat percentage were determined using dual-energy X-Ray absorptiometry. TBS was determined using TBS iNsight software. Intra and extramyocellular lipids in the soleus were measured using proton magnetic resonance spectroscopy.

RESULTS

TBS was lower in the T2D group than in the other two groups. Glycated hemoglobin (A1c) was negatively associated with TBS. Body fat percentage was negatively associated with TBS and Total Hip (TH) BMD. TH BMD was positively associated with intramuscular lipids. A trend of negative association was observed between intramuscular lipids and TBS.

CONCLUSION

This study showed for the first time that the reallocation of lipids within muscle has a negative association with TBS. Moreover, these results are consistent with previous studies showing a negative association between a parameter related to insulin resistance (intramuscular lipids) and TBS.

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

French recommendations on the prevention and treatment of osteoporosis secondary to bariatric surgery

INTRODUCTION

This article presents the initial recommendations of the Groupe de Recherche et d'Information sur les Ostéoporoses (Osteoporosis Research and Information Group [GRIO]) and the Société Française de Rhumatologie (French Rheumatology Society [SFR]) on the prevention and treatment of osteoporosis secondary to bariatric surgery.

METHODS

The recommendations were produced by a working group comprising 4 expert rheumatologists, 3 medically qualified nutritionists, 2 obesity surgeons, 1 physical activity specialist, and 1 patient-association representative.

RESULTS

The following generally recommended measures apply to all patients with an indication for bariatric surgery or who have already undergone bariatric surgery: normalize calcium and protein intake, attain a 25(OH) vitamin D concentration of between 30 and 60ng/mL; prevent the risk of falls, and introduce a suitable regimen of physical activity. An initial assessment of fracture risk should be routinely performed - ideally before the first bariatric surgery procedure - (i) in the case of RYGB and biliopancreatic diversion, regardless of age, (ii) in patients at high risk of fracture, regardless of age, and (iii) in all menopausal women and all men ≥ 50 years old, regardless of the type of bariatric surgical procedure. The fracture risk assessment is based on a determination of osteoporosis risk factors and bone mineral density measurements. Anti-osteoporosis treatment - zoledronic acid as the first line of treatment - is indicated for menopausal women and men ≥ 50 years old with (i) a history of severe fracture, regardless of T-score, (ii) a history of non-severe fracture and a T-score ≤ -1, and (iii) no history of fracture and a T-score ≤ -2.

CONCLUSIONS

There is an increased risk of fracture after bariatric surgery. Clinicians should focus their attention on patients at high fracture risk such as postmenopausal women and men older than 50 years. More research is necessary to direct and support guidelines.

Association Between Body Mass Index and Functional Outcomes in Elderly Patients with Extra-articular Distal Radius Fracture: A Prospective Observational Study

INTRODUCTION

The association between body mass index (BMI) and functional outcomes is unknown in elderly individuals with distal radius fracture (DRF).

OBJECTIVE

The aim of this study is to evaluate if there is association between BMI and functional outcomes in patients older than 60 years with DRF treated conservatively.

MATERIALS AND METHODS

A prospective observational study was performed. A total of 228 patients with extra-articular DRF were prospectively recruited. All patients were categorized by their BMI as normal, overweight, or obese. Functional outcomes were assessed after cast removal and at 1-year follow-up. The Disabilities of the Arm, Shoulder and Hand Outcome Measure (DASH), and Patient-Rated Wrist Evaluation (PRWE) questionnaires were used to assess upper limb and wrist/hand function, respectively, while the Jamar Dynamometer was used to assess grip strength.

RESULTS

Of the total number of patients, 184 were female (80.7%), 87 were overweight (38.2%), and 111 were obese (48.7%). After cast removal, the correlations between BMI and functional outcomes were DASH 0.06 (p = 0.578), PRWE 0.04 (p = 0.692), and grip strength - 0.02 (p = 0.763). At 1-year follow-up, the correlations were DASH 0.55 (p = 0.036), PRWE 0.32 (p = 0.041), and grip strength - 0.21 (p = 0.043).

CONCLUSION

This study suggests that at 1-year follow-up, there was a low-to-moderate association between BMI and poor functional outcomes in elderly patients with extra-articular DRF treated conservatively.

LEVEL OF EVIDENCE

Level IV, observational prospective study.

Obesity and Bone Health: A Complex Link

So far, the connections between obesity and skeleton have been extensively explored, but the results are inconsistent. Obesity is thought to affect bone health through a variety of mechanisms, including body weight, fat volume, bone formation/resorption, proinflammatory cytokines together with bone marrow microenvironment. In this review, we will mainly describe the effects of adipokines secreted by white adipose tissue on bone cells, as well as the interaction between brown adipose tissue, bone marrow adipose tissue, and bone metabolism. Meanwhile, this review also reviews the evidence for the effects of adipose tissue and its distribution on bone mass and bone-related diseases, along with the correlation between different populations with obesity and bone health. And we describe changes in bone metabolism in patients with anorexia nervosa or type 2 diabetes. In summary, all of these findings show that the response of skeleton to obesity is complex and depends on diversified factors, such as mechanical loading, obesity type, the location of adipose tissue, gender, age, bone sites, and secreted cytokines, and that these factors may exert a primary function in bone health.

Obesity, Bariatric Surgery, and Fractures

CONTEXT

Obesity and its associated comorbidities are a recognized and growing public health problem. For a long time, obesity-associated effects on bone were considered to strengthen the bone, mainly because of the known relationship between body weight and bone mass and the long-term weight-bearing load effect on bone. However, recent epidemiologic studies have shown that obesity may not have a fully protective effect on the occurrence of fragility fractures. The goal of this article is to review updated information on the link between obesity, bariatric surgery, and fractures.

METHODS

The primary source literature for this review was acquired by searching a published database for reviews and articles up to January 2018. Additional references were selected through the in-depth analysis of the relevant studies.

RESULTS

We present data showing that overweight and obesity are often encountered in fracture cases. We also analyzed possible reasons and risk factors for fractures associated with overweight and patients with obesity. In addition, this review focuses on the complex effects of dramatic changes in body composition when interpreting dual-energy X-ray absorptiometry readings and findings. Finally, we review the data on the effects and consequences of bariatric surgery on bone metabolism and the risk of fractures in patients undergoing these procedures.

CONCLUSION

Because of various adiposity-induced effects, patients with obesity are at risk for fracture in certain sites. Bariatric surgery increases the risk of fractures in patients undergoing malabsorptive procedures.

Effects of obesity on the healing of bone fracture in mice

Background

Obesity affects bone health to varying degrees, depending on the skeletal site (weight-bearing or non-weight-bearing) and compartment (cortical or trabecular), and is a risk factor for orthopedic disorders, including bone fractures. However, the effect and mechanisms of obesity on healing of bone fracture is little understood.

Methods

The healing bone fractures of the tibia in genetically obese mice was evaluated relative to normal mice at weekly intervals for 28 days using X-ray scans, hematoxylin and eosin (H&E) stain, and alcian blue (AB) stain. Plasma concentrations of relevant proteins were also compared via enzyme-linked immunosorbent assay (ELISA). These included calcitonin gene-related peptide (CGRP), fibroblast growth factor (FGF), transforming growth factor beta 1 (TGF-β1), and tumor necrosis factor-α (TNF-α).

Results

Bone fracture healing was delayed in the obese mice compared with the control group of normal mice, based on X-ray, H&E stain, and AB stain analysis. This was accompanied with significantly low plasma CGRP, FGF, and TGF-β1 (ELISA). However, TNF-α was significantly higher in obese mice compared with the control.

Conclusion

Bone fracture healing was significantly slower in the obese mice, relative to that of normal mice. The lower levels of CGRP, FGF, and TGF-β, and higher level of TNF-α, observed in obese mice may contribute to this observed delay in fracture healing.

Effects of obesity and diabetes on rate of bone density loss

In this large registry-based study, women with diabetes had marginally greater bone mineral density (BMD) loss at the femoral neck but not at other measurement sites, whereas obesity was not associated with greater BMD loss. Our data do not support the hypothesis that rapid BMD loss explains the increased fracture risk associated with type 2 diabetes and obesity observed in prior studies.

INTRODUCTION

Type 2 diabetes and obesity are associated with higher bone mineral density (BMD) which may be less protective against fracture than previously assumed. Inconsistent data suggest that rapid BMD loss may be a contributing factor.

METHODS

We examined the rate of BMD loss in women with diabetes and/or obesity in a population-based BMD registry for Manitoba, Canada. We identified 4960 women aged ≥ 40 years undergoing baseline and follow-up BMD assessments (mean interval 4.3 years) without confounding medication use or large weight fluctuation. We calculated annualized rate of BMD change for the lumbar spine, total hip, and femoral neck in relation to diagnosed diabetes and body mass index (BMI) category.

RESULTS

Baseline age-adjusted BMD was greater in women with diabetes and for increasing BMI category (all P < 0.001). In women with diabetes, unadjusted BMD loss was less at the lumbar spine (P = 0.017), non-significantly greater at the femoral neck (P = 0.085), and similar at the total hip (P = 0.488). When adjusted for age and BMI, diabetes was associated with slightly greater femoral neck BMD loss (- 0.0018 g/cm²/year, P = 0.012) but not at the lumbar spine or total hip. There was a strong linear effect of increasing BMI on attenuated BMI loss at the lumbar spine with negligible effects on hip BMD.

CONCLUSIONS

Diabetes was associated with slightly greater BMD loss at the femoral neck but not at other measurement sites. BMD loss at the lumbar spine was reduced in overweight and obese women but BMI did not significantly affect hip BMD loss.

Obesity Is Associated With High Perioperative Complications Among Surgically Treated Intertrochanteric Fracture of the Femur

OBJECTIVES

To document the complications among obese patients who underwent surgical fixation for intertrochanteric femur (IT) fractures and to compare with nonobese patients.

DESIGN

Retrospective cohort study.

SETTING

Four level I trauma centers.

PATIENTS

1078 IT fracture patients.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Patient and fracture characteristics, surgical duration, surgical delay intraoperative and postoperative complications, inpatient mortality, and length of stay.

METHOD

A retrospective review at 4 academic level I trauma centers was conducted to identify skeletally mature patients who underwent surgical fixation of intertrochanteric fractures between June 2008 and December 2014. Descriptive data, injury characteristics, OTA fracture classification, and associated medical comorbidities were documented. The outcomes measured included in-hospital complications, length of stay, rate of blood transfusion, change in hemoglobin levels, operative time, and wound infection.

RESULTS

Of 1078 unique patients who were treated for an IT fracture, 257 patients had a Body mass index (BMI) of 30 or greater. Patients with a high BMI (≥30) had a significantly lower mean age (73 vs. 77 years, P < 0.0001), higher percentage of high-energy injuries (18% vs. 9%, P = 0.0004), greater mean duration of surgery (96 vs. 86 minutes, P = 0.02), and higher mean length of stay (6.5 vs. 5.9 days, P = 0.004). The high-BMI group (n = 257) had significantly higher percentages of patients with complications overall (43% vs. 28%, P < 0.0001), respiratory complications (11% vs. 3%, P < 0.0001), electrolyte abnormalities (4% vs. 2%, P = 0.01), and sepsis (4% vs. 1%, P = 0.002). Patients with BMI ≥ 40 had a much higher rate of respiratory complications (18%) and wound complications (5%) than obese (BMI: 30-39.9) and nonobese patients (BMI < 30).

CONCLUSION

Intertrochanteric hip fracture patients with a BMI of >30 kg/m are much more likely to sustain systemic complications including respiratory complications, electrolyte abnormalities, and sepsis. In addition, morbidly obese patients are more likely to sustain respiratory complications and wound infections than obese (BMI: 30-39.9 kg/m) and nonobese patients (BMI: < 30 kg/m). The findings from this study can help direct surgeons in the counseling to obese patients and their family, and perhaps increase hospital reimbursement for this group of patients.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Low-trauma fractures without osteoporosis

In clinical practice, areal bone mineral density (aBMD) is usually measured using dual-energy X-ray absorptiometry (DXA) to assess bone status in patients with or without osteoporotic fracture. As BMD has a Gaussian distribution, it is difficult to define a cutoff for osteoporosis diagnosis. Based on epidemiological considerations, WHO defined a DXA-based osteoporosis diagnosis with a T-score <-2.5. However, the majority of individuals who have low-trauma fractures do not have osteoporosis with DXA (i.e., T-score <-2.5), and some of them have no decreased BMD at all. Some medical conditions (spondyloarthropathies, chronic kidney disease and mineral bone disorder, diabetes, obesity) or drugs (glucocorticoids, aromatase inhibitors) are more prone to cause fractures with subnormal BMD. In the situation of fragility fractures with subnormal or normal BMD, clinicians face a difficulty as almost all the pharmacologic treatments have proved their efficacy in patients with low BMD. However, some data are available in post hoc analyses in patients with T score >-2. Overall, in patients with a previous fragility fracture (especially vertebra or hip), treatments appear to be effective. Thus, the authors recommend treating some patients with a major fragility fracture even if areal BMD T score is above -2.5.

Correlation between obesity and severity of distal radius fractures

INTRODUCTION

The incidence of obesity has increased significantly worldwide. Our hypothesis was that patients with obesity have a more severe distal radius fracture and we realized a study to evaluate this correlation between obesity and severity of distal radius fractures caused by low-energy injuries.

MATERIALS AND METHODS

A total of 114 patients with distal radius fracture were examined in a cross-sectional, observational study. Fractures were classified according to the international AO-Müller/Orthopedic Trauma Association (AO/OTA) classification in order to determine the severity. The patient's Body Mass Index (BMI) was calculated and a Pearson correlation was performed.

RESULTS

The patients were predominantly female, and left side was more frequently affected. Most of the fractures were AO/OTA type A (71 patients). The majority of the involved patients in our study were overweighed or obese. We do not observe a direct correlation between grade of obesity and distal radius fracture severity.

CONCLUSIONS

Based on the results of this study obesity and severity of distal radius fractures do not correlate.

LEVEL OF EVIDENCE

Prognostic. Level IV.

Vitamin D alteration associated with obesity and bariatric surgery

Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries. Interactions and relationships between obesity and bone tissue and its metabolism are complex but are more and more studied and recognized. Obesity is associated with an altered hormonal profile including particularly bone-regulating hormones like vitamin D. Bariatric surgery procedures, thanks to their effectiveness to achieve therapeutic endpoints for comorbidities associated with obesity, have had an increasing success. However, these surgeries by producing mechanical restriction and or malabsorption syndrome lead to nutritional deficiencies including vitamin D. In this review, we aim to (1) discuss the nutritional deficiency of vitamin D in the obese, (2) to summarize the different surgical options in bariatric surgery and to present the evidence concerning these procedures and their associated profile in vitamin D post-operative insufficiency, (3) to present the different recommendations in clinical practice to prevent or treat vitamin D deficiencies or insufficiencies in patients treated by bariatric surgery and finally to introduce emerging assumptions on the relationship between vitamin D, microbiota composition and circulating bile acids. Impact statement Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries with a prevalence increasing from 6.4 in 1975 to 14.9% in 2014. This present review summarizes currently available data on vitamin D deficiencies in the obese population before and after bariatric surgery. The important evidence emerging from our evaluation confirms that obese patients are at risk of multiple nutritional deficiencies, especially vitamin D deficiency, before bariatric surgery. Our survey confirms that the precise role of the gut microbiome and its associated changes on the vitamin D metabolism after the different bariatric surgery procedures has not yet been studied. Furthermore, whether differences in the microbiota may alter the therapeutic responses to vitamin D is not known.

Association of Body Mass Index With the Pattern of Surgically Treated Ankle Fractures Using Two Different Classification Systems

The present retrospective cohort study assessed the association of body mass index (BMI) with the pattern of ankle fractures using 2 classifications systems. Of the 1011 consecutive patients who underwent surgery for ankle fractures in 2 hospitals from January 2009 to December 2011, 837 had a classifiable fracture according to 1 of 2 classification systems and complete information available for covariates. The association of BMI, adjusted for age, sex, corticosteroid use, diabetes, and smoking status with having a more proximal fibula fracture (Weber class A to C) and an increasing number of malleoli involved (uni-, bi-, or trimalleolar) was assessed using multivariable ordered logistic regression analysis. The mean age of the patients was 50.9 ± 16.9 years, and 461 (55%) were female. On multivariable analysis, BMI and male sex were associated with having a more proximal fibula fracture using the Weber classification, with an odds ratio (OR) of 1.07 (95% confidence interval [CI] 1.04 to 1.11; p < .001) per 1 kg/m² increase and OR of 2.96 (95% CI 2.13 to 4.11; p < .001) compared with female sex, respectively. Age was not associated with this fracture classification. In an analysis of uni-, bi-, and trimalleolar fractures, age per 10 years showed higher odds (OR 1.24, 95% CI 1.14 to 1.36; p < .001) and male sex lower odds compared with female sex (OR 0.36, 95% CI 0.27 to 0.48; p < .001) of having trimalleolar fractures than uni- or bimalleolar fractures. An increasing BMI did not seem to be a risk factor, although an inverse U-shaped relationship was seen between quintiles of BMI and the OR of having trimalleolar versus uni- or bimalleolar fractures. Corticosteroid use, diabetes, and smoking status were not significantly associated with the pattern of the ankle fractures using either classification system. In conclusion, an increasing BMI and male sex were risk factors for proximal fibula fractures, and female sex and age were risk factors for bi- and trimalleolar fractures.

Radiographic and functional outcomes after displaced intra-articular calcaneal fractures: a comparative cohort study among the traditional open technique (ORIF) and percutaneous surgical procedures (PS)

BACKGROUND

Open reduction with internal fixation (ORIF) and percutaneous surgery (PS) are the most common surgical procedures for the treatment of displaced intra-articular calcaneal fractures. The purpose of this retrospective study was to compare the clinical and radiological results of these techniques and to verify the prognostic value of the radiographic measurement tools proposed in the literature.

METHODS

A consecutive series of 104 calcaneal fractures was included in this analysis. Essex-Lopresti and Sanders classifications were used to evaluate the injuries, and their prognostic correlation was tested. Böhler's angle was measured pre- and postoperatively and evaluated as radiological outcome. Clinical outcomes were evaluated using the American Orthopaedic Foot and Ankle Society hindfoot scale (AOFAS), Maryland Foot Scale (MFS), 17-Foot Function Index (FFI), Short Form-36 (PCS), and a 10-point visual analogue scale (VAS).

RESULTS

A total of 87 fractures (5 bilateral), 54 in males and 28 in females, were evaluated with a mean follow-up of 77.0 months. Overall mean age was 51.6 years old. The most frequent cause of trauma was a fall from a height. According to Essex-Lopresti, there were 58 joint depression fractures, 26 tongue, and 3 comminute. According to Sanders: 37 type II, 31 type III, and 19 type IV. Patients were divided into three groups according to surgical treatment: 19 in the ORIF group, 35 in the PS Screw group, and 33 in PS K-wire group. The ORIF group obtained significantly better results (82 AOFAS, 86 MFS, 19.6 FFI, 46.2 PCS, 8 VAS) with respect to the PS K-wire group (74 AOFAS, 76 MSF, 26.4 FFI, 40.8 PCS, 6 VAS). The PS Screw group obtained intermediate results (79 AOFAS, 82 MFS, 22.4 FFI, 41.6 PCS, 7 VAS). The restoration of the Böhler's angle was achieved most frequently (p = 0.02) in the ORIF group, without better clinical results.

CONCLUSION

The results were best in the ORIF group, despite its risk of complications, inferior in the PS Screw group, however without statistical significance (p > 0.05), and worse in the PS K-wire group. Finally, our data confirmed the prognostic correlation between the two radiographic classifications used and the clinical outcomes.

Changes in Skeletal Integrity and Marrow Adiposity during High-Fat Diet and after Weight Loss

The prevalence of obesity has continued to rise over the past three decades leading to significant increases in obesity-related medical care costs from metabolic and non-metabolic sequelae. It is now clear that expansion of body fat leads to an increase in inflammation with systemic effects on metabolism. In mouse models of diet-induced obesity, there is also an expansion of bone marrow adipocytes. However, the persistence of these changes after weight loss has not been well described. The objective of this study was to investigate the impact of high-fat diet (HFD) and subsequent weight loss on skeletal parameters in C57Bl6/J mice. Male mice were given a normal chow diet (ND) or 60% HFD at 6 weeks of age for 12, 16, or 20 weeks. A third group of mice was put on HFD for 12 weeks and then on ND for 8 weeks to mimic weight loss. After these dietary challenges, the tibia and femur were removed and analyzed by micro computed-tomography for bone morphology. Decalcification followed by osmium staining was used to assess bone marrow adiposity, and mechanical testing was performed to assess bone strength. After 12, 16, or 20 weeks of HFD, mice had significant weight gain relative to controls. Body mass returned to normal after weight loss. Marrow adipose tissue (MAT) volume in the tibia increased after 16 weeks of HFD and persisted in the 20-week HFD group. Weight loss prevented HFD-induced MAT expansion. Trabecular bone volume fraction, mineral content, and number were decreased after 12, 16, or 20 weeks of HFD, relative to ND controls, with only partial recovery after weight loss. Mechanical testing demonstrated decreased fracture resistance after 20 weeks of HFD. Loss of mechanical integrity did not recover after weight loss. Our study demonstrates that HFD causes long-term, persistent changes in bone quality, despite prevention of marrow adipose tissue accumulation, as demonstrated through changes in bone morphology and mechanical strength in a mouse model of diet-induced obesity and weight loss.

Estimated lean mass and fat mass differentially affect femoral bone density and strength index but are not FRAX independent risk factors for fracture

Although increasing body weight has been regarded as protective against osteoporosis and fractures, there is accumulating evidence that fat mass adversely affects skeletal health compared with lean mass. We examined skeletal health as a function of estimated total body lean and fat mass in 40,050 women and 3600 men age ≥50 years at the time of baseline dual-energy X-ray absorptiometry (DXA) testing from a clinical registry from Manitoba, Canada. Femoral neck bone mineral density (BMD), strength index (SI), cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI) were derived from DXA. Multivariable models showed that increasing lean mass was associated with near-linear increases in femoral BMD, CSA, and CSMI in both women and men, whereas increasing fat mass showed a small initial increase in these measurements followed by a plateau. In contrast, femoral SI was relatively unaffected by increasing lean mass but was associated with a continuous linear decline with increasing fat mass, which should predict higher fracture risk. During mean 5-year follow-up, incident major osteoporosis fractures and hip fractures were observed in 2505 women and 180 men (626 and 45 hip fractures, respectively). After adjustment for fracture risk assessment tool (FRAX) scores (with or without BMD), we found no evidence that lean mass, fat mass, or femoral SI affected prediction of major osteoporosis fractures or hip fractures. Findings were similar in men and women, without significant interactions with sex or obesity. In conclusion, skeletal adaptation to increasing lean mass was positively associated with BMD but had no effect on femoral SI, whereas increasing fat mass had no effect on BMD but adversely affected femoral SI. Greater fat mass was not independently associated with a greater risk of fractures over 5-year follow-up. FRAX robustly predicts fractures and was not affected by variations in body composition.