Ectopic and serum lipid levels are positively associated with bone marrow fat in obesity

Resistance Training for Older Adults: Position Statement From the National Strength and Conditioning Association

Fragala, MS, Cadore, EL, Dorgo, S, Izquierdo, M, Kraemer, WJ, Peterson, MD, and Ryan, ED. Resistance training for older adults: position statement from the national strength and conditioning association. J Strength Cond Res 33(8): 2019-2052, 2019-Aging, even in the absence of chronic disease, is associated with a variety of biological changes that can contribute to decreases in skeletal muscle mass, strength, and function. Such losses decrease physiologic resilience and increase vulnerability to catastrophic events. As such, strategies for both prevention and treatment are necessary for the health and well-being of older adults. The purpose of this Position Statement is to provide an overview of the current and relevant literature and provide evidence-based recommendations for resistance training for older adults. As presented in this Position Statement, current research has demonstrated that countering muscle disuse through resistance training is a powerful intervention to combat the loss of muscle strength and muscle mass, physiological vulnerability, and their debilitating consequences on physical functioning, mobility, independence, chronic disease management, psychological well-being, quality of life, and healthy life expectancy. This Position Statement provides evidence to support recommendations for successful resistance training in older adults related to 4 parts: (a) program design variables, (b) physiological adaptations, (c) functional benefits, and (d) considerations for frailty, sarcopenia, and other chronic conditions. The goal of this Position Statement is to a) help foster a more unified and holistic approach to resistance training for older adults, b) promote the health and functional benefits of resistance training for older adults, and c) prevent or minimize fears and other barriers to implementation of resistance training programs for older adults.

The effect of excessive fat tissue on the measure of bone mineral density by dual X-ray absorptiometry: the impact of substantial weight loss following sleeve gastrectomy

PURPOSE

Dual-energy X-ray absorptiometry (DXA) is used in clinical routine to determine areal bone mineral density (aBMD). However, it is not clear whether excessive fat mass or substantial weight loss modify the aBMD measurements. The aim of this study was to evaluate the effect of soft tissue composition on aBMD measured by DXA using a clinical model (i.e. sleeve gastrectomy: SG) that induces substantial body weight loss.

METHODS

Areal bone mineral density and body composition (fat mass: FM and lean tissue mass: LTM) were determined by DXA in 41 obese patients (33 women, 80.5%) just before SG and 1 month later.

RESULTS

One month after SG, mean weight loss was -9.8 ± 2.6 kg, with a significant decrease in LTM and FM (kg) ranging from -7.3% to -9.5%. The relative variation in aBMD was increased at the lumbar spine (2.45 ± 3.44%) and decreased at the hip (-1.47 ± 2.28%), whereas no variation was observed for the whole body and radius. The variation in aBMD at the lumbar spine was inversely correlated with variations in weight, whole-body FM and trunk FM, but not LTM.

CONCLUSION

This study shows evidence of a potential effect of body composition, particularly FM, on aBMD. However, given the modest change in aBMD, which was close to the precision error of aBMD measurements, it appears that significant weight loss does not have a clinically significant impact on the evaluation of aBMD using DXA.

Modulation of Bone and Marrow Niche by Cholesterol

Bone is a complex tissue composing of mineralized bone, bone cells, hematopoietic cells, marrow adipocytes, and supportive stromal cells. The homeostasis of bone and marrow niche is dynamically regulated by nutrients. The positive correlation between cardiovascular disease and osteoporosis risk suggests a close relationship between hyperlipidemia and/or hypercholesterolemia and the bone metabolism. Cholesterol and its metabolites influence the bone homeostasis through modulating the differentiation and activation of osteoblasts and osteoclasts. The effects of cholesterol on hematopoietic stem cells, including proliferation, migration, and differentiation, are also well-documented and further relate to atherosclerotic lesions. Correlation between circulating cholesterol and bone marrow adipocytes remains elusive, which seems opposite to its effects on osteoblasts. Epidemiological evidence has demonstrated that cholesterol deteriorates or benefits bone metabolism depending on the types, such as low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. In this review, we will summarize the latest progress of how cholesterol regulates bone metabolism and bone marrow microenvironment, including the hematopoiesis and marrow adiposity. Elucidation of these association and factors is of great importance in developing therapeutic options for bone related diseases under hypercholesterolemic conditions.

The Relationship between Risk Factors for Metabolic Syndrome and Bone Mineral Density in Menopausal Korean Women

BACKGROUND

The risk factors of metabolic syndrome (MetS) in menopausal women are potential causes of osteoporosis. However, there is no consensus on this. We aimed to determine the relationship between risk factors of MetS and bone mineral density (BMD) in menopausal Korean women.

METHODS

We enrolled 205 menopausal Korean women who visited a health promotion center in Seoul in 2015 and divided them into the following two groups according to the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III) criteria with modified waist-circumference criteria: the non-MetS group (Group 1, n=90) and the MetS group (Group 2, n=115). Anthropometric parameters and clinical parameters, including blood pressure, blood lipid profile (cholesterol, triglycerides), and fasting blood sugar levels were recorded for all participants. BMD at the lumbar spine was determined using dual-energy X-ray absorptiometry (DEXA). The relationship between the risk factors of MetS and bone mineral density was analyzed by statistical methods.

RESULTS

There was no significant difference in risk factors of MetS between the groups. In correlation tests, waist circumference showed a significant association with body surface area (BSA) (r = -0.242, P < 0.001). Diastolic blood pressure was correlated with BSA (r = 0.186, P < 0.01) and bone mineral content (BMC) (r = 0.161, P < 0.05). However, multiple regression analysis showed no significant relationship between MetS risk factors and BMD.

CONCLUSION

The risk factors of MetS did not affect BMD in menopausal Korean women. Follow-up studies with a larger study population are necessary size to allow the investigation of other research variables.

Marrow adipose tissue imaging in humans

Bone strength is affected not only by bone mineral density (BMD) and bone microarchitecture but also its microenvironment. Recent studies have focused on the role of marrow adipose tissue (MAT) in the pathogenesis of bone loss. Osteoblasts and adipocytes arise from a common mesenchymal stem cell within bone marrow and many osteoporotic states, including aging, medication use, immobility, over - and undernutrition are associated with increased marrow adiposity. Advancements in imaging technology allow the non-invasive quantification of MAT. This article will review magnetic resonance imaging (MRI)- and computed tomography (CT)-based imaging technologies to assess the amount and composition of MAT. The techniques that will be discussed are anatomic T1-weighted MRI, water-fat imaging, proton MR spectroscopy, single energy CT and dual energy CT. Clinical applications of MRI and CT techniques to determine the role of MAT in patients with obesity, anorexia nervosa, and type 2 diabetes will be reviewed.

Differential associations between appendicular and axial marrow adipose tissue with bone microarchitecture in adolescents and young adults with obesity

Marrow adipose tissue (MAT) in humans is distributed differentially across age and skeletal site. We have shown impaired microarchitecture and reduced bone strength at appendicular sites in conditions associated with high MAT of the axial skeleton in adults (including conditions of over- and undernutrition). Data are lacking regarding differences in MAT content of the appendicular versus the axial skeleton, and its relationship with bone microarchitecture and strength. Furthermore, data are conspicuously lacking in adolescents, a time when hematopoietic marrow is progressively converted to fatty marrow. The purpose of our study was to examine differential associations between appendicular (distal tibia) and axial (lumbar spine) MAT and bone microarchitecture and strength estimates of the distal tibia in adolescents with obesity. We hypothesized that compared to MAT of the axial skeleton (lumbar spine), MAT of the appendicular skeleton (distal tibia) would show stronger associations with bone microarchitecture and strength estimates of the appendicular skeleton (distal tibia). We evaluated 32 adolescents and young adults (27 females) with obesity; with a mean age of 17.8 ± 2.1 years and median body mass index (BMI) of 41.34 kg/m², who underwent dual energy X-ray absorptiometry (DXA) for total fat mass, proton MR spectroscopy (1H-MRS) of the distal tibia and 4th lumbar vertebra for MAT, high resolution peripheral quantitative computed tomography (HR-pQCT) of the distal tibia for volumetric bone mineral density (vBMD) and microarchitecture, and micro finite element analysis (FEA) for distal tibial strength estimates. Linear correlations between bone parameters and MAT were determined using the Spearman or Pearson methods, depending on data distribution. Lumbar spine MAT was inversely associated with age (r = -0.36; p = 0.037). Total and trabecular vBMD and trabecular number at the distal tibia were inversely associated with MAT at the distal tibia (r = -0.39, p = 0.025; r = -0.51, p = 0.003; r = -0.42, p = 0.015 respectively) but not with lumbar spine MAT (r = -0.19, p = 0.27; r = -0.18, p = 0.3; r = 0.005, p = 0.97 respectively). In adolescents and young adults with obesity, the associations between MAT and appendicular bone parameters differ depending on the site of MAT assessment i.e. axial vs. appendicular. Studies evaluating these endpoints in adolescents and young adults with obesity should take the site of MAT assessment into consideration.

Differential effects of high-fat diet and exercise training on bone and energy metabolism

Bone microarchitecture and strength are impaired by obesity and physical inactivity, but the underlying molecular regulation of bone metabolism in response to these factors is not well understood. Therefore, we analyzed bone and energy metabolism in male mice fed a high-fat or standard chow diet for 12 weeks with or without free access to running wheels. High-fat diet (HFD) mimicked the human condition of obesity and insulin resistance, including symptoms such as elevated serum glucose and insulin levels and reduced insulin-stimulated glucose uptake into muscle and adipose tissue. Interestingly, HFD also decreased (-44%) glucose uptake into bone marrow. Bone mass was reduced (-45%) by HFD due to a diminished (-45%) bone remodeling rate. Bone matrix quality aspects, such as biomechanical stability, were additionally decreased. Concurrently, the bone marrow adiposity increased (+63%) in response to a HFD. Further, we detected elevated expression of the Wnt signaling inhibitor dickkopf-1 (Dkk-1, +42%) in mice fed a HFD, but this was not reflected in serum samples obtained from obese humans. In mice, exercise attenuated the adverse effects of HFD by reversing the glucose uptake into bone marrow, improving the bone mass and bone matrix quality while decreasing the bone marrow adiposity. This data shows that exercise prevents some, but not all of the negative effects of HFD on bone health and suggests that insulin signaling in bone marrow and Dkk-1 signaling may be involved in the pathogenesis of bone loss induced by HFD.

Evaluation of cross-sectional and longitudinal changes in volumetric bone mineral density in postmenopausal women using single- versus dual-energy quantitative computed tomography

Central quantitative computed tomography (QCT) is increasingly used in clinical trials and practice to assess bone mass or strength and to evaluate longitudinal changes in response to drug treatment. Current studies utilize single-energy (SE) QCT scans, which may be confounded both by the amount of bone marrow fat at baseline and changes in marrow fat over time. However, the extent to which marrow fat changes either underestimate volumetric BMD (vBMD) measurements at baseline or under-/overestimate longitudinal changes in vivo in humans remains unclear. To address this issue, 197 early postmenopausal women [median age (IQR) 56.7 (54.4-58.7) years] underwent spine and hip QCT scans at baseline and 3 years using a 128-slice dual-source dual-energy (DE) scanner. The scans were analyzed as either SE scans (100 kVp) or DE scans (100 kVp and 140 kVp), with the latter accounting for bone marrow fat. At baseline, vertebral trabecular vBMD was (median) 17.6% lower (P < 0.001) while femur neck (FN) cortical vBMD was only 3.2% lower (P < 0.001) when assessed by SE vs DE scanning. SE scanning overestimated the 3 year rate of bone loss for trabecular bone at the spine by 24.2% (P < 0.001 vs DE rates of loss) but only by 8.8% for changes in FN cortical vBMD (P < 0.001 vs DE rates of loss). The deviation between SE and DE rates of bone loss in trabecular vBMD became progressively greater as the rate of bone loss increased. These findings demonstrate that SE QCT scans underestimate trabecular vBMD and substantially overestimate rates of age-related bone loss due to ongoing conversion of red to yellow marrow. Further, the greater the rate of bone loss, the greater the overestimation of bone loss by SE scans. Although our findings are based on normal aging, recent evidence from animal studies demonstrates that the skeletal anabolic drugs teriparatide and romosozumab may markedly reduce marrow fat, perhaps accounting for the disproportionate increases in trabecular vBMD by SE QCT as compared to dual-energy X-ray absorptiometry with these agents. As such, future studies using recently available DE scanning technology that has satisfactory precision and radiation exposure are needed to evaluate changes in trabecular vBMD independent of changes in marrow fat with aging and drugs that may alter marrow fat composition.

Sex differences in body composition and association with cardiometabolic risk

Background

Body composition differs between men and women, with women having proportionally more fat mass and men more muscle mass. Although men and women are both susceptible to obesity, health consequences differ between the sexes. The purpose of our study was to assess sex differences in body composition using anatomic and functional imaging techniques, and its relationship to cardiometabolic risk markers in subjects with overweight/obesity.

Methods

After written informed consent, we prospectively recruited 208 subjects with overweight/obesity who were otherwise healthy (94 men, 114 women, age 37 ± 10 years, BMI 35 ± 6 kg/m²). Subjects underwent dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) for fat and muscle mass, proton MR spectroscopy (1H-MRS) for intrahepatic (IHL) and intramyocellular lipids (IMCL), an oral glucose tolerance test, serum insulin, lipids, and inflammatory markers. Men and women were compared by Wilcoxon signed rank test. Linear correlation and multivariate analyses between body composition and cardiometabolic risk markers were performed.

Results

Women and men were of similar mean age and BMI (p ≥ 0.2). Women had higher %fat mass, extremity fat, and lower lean mass compared to men (p ≤ 0.0005). However, men had higher visceral adipose tissue (VAT) and IMCL and higher age-and BMI-adjusted IHL (p < 0.05). At similar age and BMI, men had a more detrimental cardiometabolic risk profile compared to women (p < 0.01). However, VAT in women, and IMCL in men, were more strongly associated with cardiometabolic risk markers, while more lower extremity fat was associated with a more favorable cardiometabolic profile in women compared to men (p ≤ 0.03).

Conclusions

Although the male pattern of fat distribution is associated with a more detrimental cardiometabolic risk profile compared to women of similar age and BMI, VAT is more strongly associated with cardiometabolic risk markers in women, while IMCL are more detrimental in men. Lower extremity fat is relatively protective, in women more than in men. This suggests that detailed anatomic and functional imaging, rather than BMI, provides a more complete understanding of metabolic risk associated with sex differences in fat distribution.

Marrow Adipose Tissue: Its Origin, Function, and Regulation in Bone Remodeling and Regeneration

Marrow adipose tissue (MAT) is a unique fat depot in the bone marrow and exhibits close relationship with hematopoiesis and bone homeostasis. MAT is distinct from peripheral adipose tissue in respect of its heterogeneous origin, site-specific distribution, and complex and perplexing function. Though MAT is indicated to function in hematopoiesis, skeletal remodeling, and energy metabolism, its explicit characterization still requires further research. In this review, we highlight recent advancement made in MAT regarding the origin and distribution of MAT, the local interaction with bone homeostasis and hematopoietic niche, the systemic endocrine regulation of metabolism, and MAT-based strategies to enhance bone formation.

Prevalence of excessive body fat among adolescents of a south Brazilian metropolitan region and State capital, associated risk factors, and consequences

BACKGROUND

The prevalence of overweight/obesity has become a major concern for public health in developing countries. Risk factors need to be well documented so that these countries develop public policies to fight the problem. Thus, the objective of this study is to determine the prevalence of excess fat among adolescents of a South Brazilian State Capital associated with risk factors and their consequences.

METHODS

This study was conducted between 2014 and 2016 with adolescents aged 11-18 years. The following body composition measurements were collected: body mass, height, waist circumference, fat mass and bone mineral density (this latter through dual energy X-ray absorptiometry). Biochemical data as glucose, total cholesterol, and triglycerides were also collected. Finally, socioeconomic questionnaires were applied, as well as questionnaires regarding: the education level of guardians, active transportation, time spent with sedentary activities and physical activities. Odds ratios and chi-square test were applied in statistical analysis.

RESULTS

Data from 675 adolescents, from which 70% were males, were analyzed. The mean age was 14.7 ± 1.8 years. The prevalence of excess fat was 18.2% in boys and 92.1% in girls. As for sedentary lifestyle and physical inactivity, having one of these factors increased the risk of being overweight by 7.9 times for boys and 3.0 times for girls. In boys, there was a significant association between excess fat and waist circumference (p = 0.000; OR = 13.5; CI = 7.0-25.9), physical activity level (p = 0.000; OR = 4.0; CI = 2.5-6.5), triglycerides (p = 0.019; OR = 2.2; CI = 1.1-4.2) and total cholesterol (p = 0.000; OR = 2.6; CI = 1.6-4.5). In girls, there was an association between having excess fat and an increase in total cholesterol (p = 0.000; OR = 8.0; CI = 2.6-24.4).

CONCLUSIONS

The high prevalence of excess fat was greater than what was described by some studies conducted in developed countries. This reality demonstrates the need to implement public policies that can directly promote the reduction of sedentary habits and reinforce the importance of adopting an active lifestyle.

Bone marrow fat contributes to insulin sensitivity and adiponectin secretion in premenopausal women

PURPOSE

Bone marrow fat is a functionally distinct adipose tissue that may contribute to systemic metabolism. This study aimed at evaluating a possible association between bone marrow fat and insulin sensitivity indices.

METHODS

Fifty obese (n = 23) and non-obese (n = 27) premenopausal women underwent proton magnetic resonance spectroscopy to measure vertebral bone marrow fat content and unsaturation index at L4 level. Abdominal visceral, subcutaneous fat, and epicardial fat were also measured using magnetic resonance imaging. Bone mineral density was measured by dual-energy X-ray absorptiometry. Body composition was assessed by bioelectrical impedance analysis. Fasting serum glucose, insulin, lipids, adiponectin were measured; the insulin resistance index HOMA (HOMA-IR) was calculated.

RESULTS

Bone marrow fat content and unsaturation index were similar in obese and non-obese women (38.5 ± 0.1 vs. 38.6 ± 0.1%, p = 0.994; 0.162 ± 0.065 vs. 0.175 ± 0.048, p = 0.473, respectively). Bone marrow fat content negatively correlated with insulin and HOMA-IR (r = -0.342, r = -0.352, respectively, p = 0.01) and positively with high density lipoprotein cholesterol (r = 0.270, p = 0.043). From a multivariate regression model including lnHOMA-IR as a dependent variable and visceral, subcutaneous, epicardial fat, and bone marrow fat as independent variables, lnHOMA-IR was significantly associated with bone marrow fat (β = -0.008 ± 0.004, p = 0.04) and subcutaneous fat (β = 0.003 ± 0.001, p = 0.04). Bone marrow fat, among the other adipose depots, was a significant predictor of circulating adiponectin (β = 0.147 ± 0.060, p = 0.021). Bone marrow fat unsaturation index negatively correlated with visceral fat (r = -0.316, p = 0.026).

CONCLUSIONS

There is a relationship between bone marrow fat content and insulin sensitivity in obese and non-obese premenopausal women, possibly mediated by adiponectin secretion. Visceral fat does not seem to regulate bone marrow fat content while it may affect bone marrow fat composition.

Clinical implications of bone marrow adiposity

Marrow adipocytes, collectively termed marrow adipose tissue (MAT), reside in the bone marrow in close contact to bone cells and haematopoietic cells. Marrow adipocytes arise from the mesenchymal stem cell and share their origin with the osteoblast. Shifts in the lineage allocation of the mesenchymal stromal cell could potentially explain the association between increased MAT and increased fracture risk in diseases such as postmenopausal osteoporosis, anorexia nervosa and diabetes. Functionally, marrow adipocytes secrete adipokines, such as adiponectin, and cytokines, such as RANK ligand and stem cell factor. These mediators can influence both bone remodelling and haematopoiesis by promoting bone resorption and haematopoietic recovery following chemotherapy. In addition, marrow adipocytes can secrete free fatty acids, acting as a energy supply for bone and haematopoietic cells. However, this induced lipolysis is also used by neoplastic cells to promote survival and proliferation. Therefore, MAT could represent a new therapeutic target for multiple diseases from osteoporosis to leukaemia, although the exact characteristics and role of the marrow adipocyte in health and diseases remain to be determined.

Anatomical Variation of Age-Related Changes in Vertebral Bone Marrow Composition Using Chemical Shift Encoding-Based Water-Fat Magnetic Resonance Imaging

Assessment of vertebral bone marrow composition has been proposed as imaging biomarker for osteoporosis, hematopoietic, and metabolic disorders. We investigated the anatomical variation of age-related changes of vertebral proton density fat fraction (PDFF) using chemical shift encoding-based water-fat magnetic resonance imaging (MRI). 156 healthy subjects were recruited (age range 20-29 years: 12/30 males/females; 30-39: 15/9; 40-49: 4/14; 50-59: 9/27; 60-69: 5/19; 70-79: 4/8). An eight-echo 3D spoiled gradient-echo sequence at 3T MRI was used for chemical shift-encoding based water-fat separation at the lumbar spine. Vertebral bodies of L1-L4 were manually segmented to extract PDFF values at each vertebral level. PDFF averaged over L1-L4 was significantly (p < 0.05) higher in males than females in the twenties (32.0 ± 8.0 vs. 27.2 ± 6.0%) and thirties (35.3 ± 6.7 vs. 27.3 ± 6.2%). With increasing age, females showed an accelerated fatty conversion of the bone marrow compared to men with no significant (p > 0.05) mean PDFF differences in the forties (32.4 ± 8.4 vs. 34.5 ± 6.8%) and fifties (42.0 ± 6.1 vs. 40.5 ± 9.7%). The accelerated conversion process continued resulting in greater mean PDFF values in females than males in the sixties (40.2 ± 6.9 vs. 48.8 ± 7.7%; p = 0.033) and seventies (43.9 ± 7.6 vs. 50.5 ± 8.2%; p = 0.208), though the latter did not reach statistical significance. Relative age-related PDFF change from the twenties to the seventies increased from 16.7% (L1) to 51.4% (L4) in males and 76.8% (L1) to 85.7% (L4) in females. An accelerated fatty conversion of bone marrow was observed in females with increasing age particularly evident after menopause. Relative age-related PDFF changes showed an anatomical variation with most pronounced changes at lower lumbar vertebral levels in both sexes.

A study on dynamic monitoring, components, and risk factors of embolism during total knee arthroplasty

BACKGROUND

Fat embolism is a common complication of orthopedic surgery. However, the exact component and risk factor responsible for this complication remains unelucidated. This study aimed to detect the origin of the pulmonary embolus and identify relevant risk factors of pulmonary embolism in total knee replacement.

METHODS

A total of 40 osteoarthritis patients who underwent primary unilateral TKA were recruited into this study. Transesophageal echocardiography (TEE) was utilized to dynamically monitor the embolism. Pulmonary arterial pressure was recorded and biopsies were obtained from the medullary cavity during surgery.

RESULTS

After tourniquet release, the arterial embolism was observed by TEE to have a peak signal at 30 seconds when pulmonary arterial pressure was increased by 25% to 40% (P = .002). The pathology study of the embolism revealed its bone marrow origin. Total embolus quantity was positively correlated with age (P = .021), body mass index (BMI, P = .041), and fat content of the bone marrow (P = .003). Logistic regression analysis revealed that the fat content of the marrow (OR: 1.432, 95% CI: 1.335-1.592), age (OR: 1.632, 95% CI: 1.445-1.832), and BMI (OR: 1.231, 95% CI: 1.032-1.381) were risk factors for pulmonary hypertension.

CONCLUSION

This study revealed that the embolus detected in the right atrium was derived from bone marrow tissues, and this led to pulmonary arterial pressure fluctuations after tourniquet release. Therefore, elderly patients who have high BMI or bone marrow fat content are at high-risk for pulmonary fat embolism during TKA.

Differential Aging Signals in Abdominal CT Scans

RATIONALE AND OBJECTIVES

Changes in the composition of body tissues are major aging phenotypes, but they have been difficult to study in depth. Here we describe age-related change in abdominal tissues observable in computed tomography (CT) scans. We used pattern recognition and machine learning to detect and quantify these changes in a model-agnostic fashion.

MATERIALS AND METHODS

CT scans of abdominal L4 sections were obtained from Baltimore Longitudinal Study of Aging (BLSA) participants. Age-related change in the constituent tissues were determined by training machine classifiers to differentiate age groups within male and female strata ("Younger" at 50-70 years old vs "Older" at 80-99 years old). The accuracy achieved by the classifiers in differentiating the age cohorts was used as a surrogate measure of the aging signal in the different tissues.

RESULTS

The highest accuracy for discriminating age differences was 0.76 and 0.72 for males and females, respectively. The classification accuracy was 0.79 and 0.71 for adipose tissue, 0.70 and 0.68 for soft tissue, and 0.65 and 0.64 for bone.

CONCLUSIONS

Using image data from a large sample of well-characterized pool of participants dispersed over a wide age range, we explored age-related differences in gross morphology and texture of abdominal tissues. This technology is advantageous for tracking effects of biological aging and predicting adverse outcomes when compared to the traditional use of specific molecular biomarkers. Application of pattern recognition and machine learning as a tool for analyzing medical images may provide much needed insight into tissue changes occurring with aging and, further, connect these changes with their metabolic and functional consequences.

Bone Marrow Fat Changes After Gastric Bypass Surgery Are Associated With Loss of Bone Mass

Bone marrow fat is a unique fat depot that may regulate bone metabolism. Marrow fat is increased in states of low bone mass, severe underweight, and diabetes. However, longitudinal effects of weight loss and improved glucose homeostasis on marrow fat are unclear, as is the relationship between marrow fat and bone mineral density (BMD) changes. We hypothesized that after Roux-en-Y gastric bypass (RYGB) surgery, marrow fat changes are associated with BMD loss. We enrolled 30 obese women, stratified by diabetes status. Before and 6 months after RYGB, we measured BMD by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) and vertebral marrow fat content by magnetic resonance spectroscopy. At baseline, those with higher marrow fat had lower BMD. Postoperatively, total body fat declined dramatically in all participants. Effects of RYGB on marrow fat differed by diabetes status (p = 0.03). Nondiabetic women showed no significant mean change in marrow fat (+1.8%, 95% confidence interval [CI] -1.8% to +5.4%, p = 0.29), although those who lost more total body fat were more likely to have marrow fat increases (r = -0.70, p = 0.01). In contrast, diabetic women demonstrated a mean marrow fat change of -6.5% (95% CI -13.1% to 0%, p = 0.05). Overall, those with greater improvements in hemoglobin A1c had decreases in marrow fat (r = 0.50, p = 0.01). Increases in IGF-1, a potential mediator of the marrow fat-bone relationship, were associated with marrow fat declines (r = -0.40, p = 0.05). Spinal volumetric BMD decreased by 6.4% ± 5.9% (p < 0.01), and femoral neck areal BMD decreased by 4.3% ± 4.1% (p < 0.01). Marrow fat and BMD changes were negatively associated, such that those with marrow fat increases had more BMD loss at both spine (r = -0.58, p < 0.01) and femoral neck (r = -0.49, p = 0.01), independent of age and menopause. Our findings suggest that glucose metabolism and weight loss may influence marrow fat behavior, and marrow fat may be a determinant of bone metabolism. © 2017 American Society for Bone and Mineral Research.

Body Composition and Ectopic Lipid Changes With Biochemical Control of Acromegaly

CONTEXT

Acromegaly is characterized by growth hormone (GH) and insulinlike growth factor-1 (IGF-1) hypersecretion, and GH and IGF-1 play important roles in regulating body composition and glucose homeostasis.

OBJECTIVE

The purpose of our study was to investigate body composition including ectopic lipids, measures of glucose homeostasis, and gonadal steroids in patients with active acromegaly compared with age-, body mass index (BMI)-, and sex-matched controls and to determine changes in these parameters after biochemical control of acromegaly.

DESIGN

Cross-sectional study of 20 patients with active acromegaly and 20 healthy matched controls. Prospective study of 16 patients before and after biochemical control of acromegaly.

MAIN OUTCOME MEASURES

Body composition including ectopic lipids by magnetic resonance imaging/proton magnetic resonance spectroscopy; measures of glucose homeostasis by an oral glucose tolerance test; gonadal steroids.

RESULTS

Patients with active acromegaly had lower mean intrahepatic lipid (IHL) and higher mean fasting insulin and insulin area under the curve (AUC) values than controls. Men with acromegaly had lower mean total testosterone, sex hormone-binding globulin, and estradiol values than male controls. After therapy, homeostasis model assessment of insulin resistance, fasting insulin level, and insulin AUC decreased despite an increase in IHL and abdominal and thigh adipose tissues and a decrease in muscle mass.

CONCLUSIONS

Patients with acromegaly were characterized by insulin resistance and hyperinsulinemia but lower IHL compared with age-, BMI-, and sex-matched healthy controls. Biochemical control of acromegaly improved insulin resistance but led to a less favorable anthropometric phenotype with increased IHL and abdominal adiposity and decreased muscle mass.

Osteoporosis self-reported in the elderly: a population-based survey in the city of Campinas, São Paulo, Brazil

INTRODUCTION

Osteoporosis is a multifactorial disease that predisposes individuals to suffer falls and fractures, causing functional impairment and a consequent reduction in quality of life.

OBJECTIVE

To assess the prevalence and factors associated with self-reported osteoporosis in the elderly population living in Campinas, São Paulo, Brazil (ISACAMP 2008).

METHODS

Cross-sectional study with a random sample taken by conglomerates in 2 stages totaling 1,419 elderly people living in the urban area. The self-reported prevalence of osteoporosis was estimated according to socioeconomic and demographic variables, morbidity, health behaviors and problems. Crude prevalence ratios were estimated and adjusted by means of simple and multiple regressions using the Poisson svy commands in Stata 11.0 software.

RESULTS

We found a prevalence of osteoporosis of 14.8%, and significantly higher in females, in individuals who reported white skin, those who reported less than 7 hours of sleep/day, in patients with rheumatism/arthritis/arthrosis, asthma/bronchitis/emphysema, tendinitis, dizziness, insomnia, common mental disorders, BMI < 27, health self-related as bad and very bad, and reporting falls occurring in the last 12 months.

CONCLUSION

The present study, by identifying the factors associated with osteoporosis, identified segments of older people with a higher prevalence of the disease; to this information may contribute to the planning of public health policies and programs aimed at controlling the disease and its consequences.

Meeting report of the 2016 bone marrow adiposity meeting

There is considerable interest in the physiology and pathology, as well as the cellular and molecular biology, of bone marrow adipose tissue (BMAT). Because bone marrow adiposity is linked not only to systemic energy metabolism, but also to both bone marrow and musculoskeletal disorders, this biologic compartment has become of major interest to investigators from diverse disciplines. Bone marrow adiposity represents a virtual multi-tissue endocrine organ, which encompasses cells from multiple developmental lineages (e.g., mesenchymal, myeloid, lymphoid) and occupies all the non-osseous and non-cartilaginous space within long bones. A number of research groups are now focusing on bone marrow adiposity to understand a range of clinical afflictions associated with bone marrow disorders and to consider mechanisms-based strategies for future therapies.

Quantitative MRI and spectroscopy of bone marrow

Bone marrow is one of the largest organs in the human body, enclosing adipocytes, hematopoietic stem cells, which are responsible for blood cell production, and mesenchymal stem cells, which are responsible for the production of adipocytes and bone cells. Magnetic resonance imaging (MRI) is the ideal imaging modality to monitor bone marrow changes in healthy and pathological states, thanks to its inherent rich soft‐tissue contrast. Quantitative bone marrow MRI and magnetic resonance spectroscopy (MRS) techniques have been also developed in order to quantify changes in bone marrow water–fat composition, cellularity and perfusion in different pathologies, and to assist in understanding the role of bone marrow in the pathophysiology of systemic diseases (e.g. osteoporosis). The present review summarizes a large selection of studies published until March 2017 in proton‐based quantitative MRI and MRS of bone marrow. Some basic knowledge about bone marrow anatomy and physiology is first reviewed. The most important technical aspects of quantitative MR methods measuring bone marrow water–fat composition, fatty acid composition, perfusion, and diffusion are then described. Finally, previous MR studies are reviewed on the application of quantitative MR techniques in both healthy aging and diseased bone marrow affected by osteoporosis, fractures, metabolic diseases, multiple myeloma, and bone metastases.

Level of Evidence: 3

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2018;47:332–353.

Bone marrow fat content is correlated with hepatic fat content in paediatric non-alcoholic fatty liver disease

AIM

To investigate the relationship between bone marrow fat content and hepatic fat content in children with known or suspected non-alcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This was an institutional review board-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant, cross-sectional, prospective analysis of data collected between October 2010 to March 2013 in 125 children with known or suspected NAFLD. Written informed consent was obtained for same-day research magnetic resonance imaging (MRI) of the lumbar spine, liver, and abdominal adiposity. Lumbar spine bone marrow proton density fat fraction (PDFF) and hepatic PDFF were estimated using complex-based MRI (C-MRI) techniques and magnitude-based MRI (M-MRI), respectively. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SCAT) were quantified using high-resolution MRI. All images were acquired by two MRI technologists. Hepatic M-MRI images were analysed by an image analyst; all other images were analysed by a single investigator. The relationship between lumbar spine bone marrow PDFF and hepatic PDFF was assessed with and without adjusting for the presence of covariates using correlation and regression analysis.

RESULTS

Lumbar spine bone marrow PDFF was positively associated with hepatic PDFF in children with known or suspected NAFLD prior to adjusting for covariates (r=0.33, p=0.0002). Lumbar spine bone marrow PDFF was positively associated with hepatic PDFF in children with known or suspected NAFLD (r=0.24, p=0.0079) after adjusting for age, sex, body mass index z-score, VAT, and SCAT in a multivariable regression analysis.

CONCLUSION

Bone marrow fat content is positively associated with hepatic fat content in children with known or suspected NAFLD. Further research is needed to confirm these results and understand their clinical and biological implications.

Measurement of vertebral bone marrow proton density fat fraction in children using quantitative water-fat MRI

OBJECTIVES

To investigate the feasibility of employing a 3D time-interleaved multi-echo gradient-echo (TIMGRE) sequence to measure the proton density fat fraction (PDFF) in the vertebral bone marrow (VBM) of children and to examine cross-sectional changes with age and intra-individual variations from the lumbar to the cervical region in the first two decades of life.

MATERIALS AND METHODS

Quantitative water-fat imaging of the spine was performed in 93 patients (49 girls; 44 boys; age median 4.5 years; range 0.1-17.6 years). For data acquisition, a six-echo 3D TIMGRE sequence was used with phase correction and complex-based water-fat separation. Additionally, single-voxel MR spectroscopy (MRS) was performed in the L4 vertebrae of 37 patients. VBM was manually segmented in the midsagittal slice of each vertebra. Univariable and multivariable linear regression models were calculated between averaged lumbar, thoracic and cervical bone marrow PDFF and age with adjustments for sex, height, weight, and body mass index percentile.

RESULTS

Measured VBM PDFF correlated strongly between imaging and MRS (R ² = 0.92, slope = 0.94, intercept = -0.72%). Lumbar, thoracic and cervical VBM PDFF correlated significantly (all p < 0.001) with the natural logarithm of age. Differences between female and male patients were not significant (p > 0.05).

CONCLUSION

VBM development in children showed a sex-independent cross-sectional increase of PDFF correlating with the natural logarithm of age and an intra-individual decrease of PDFF from the lumbar to the cervical region in all age groups. The present results demonstrate the feasibility of using a 3D TIMGRE sequence for PDFF assessment in VBM of children.

Marrow adipose tissue composition in adults with morbid obesity

Patients with type 2 diabetes mellitus (T2DM) have increased fracture risk despite normal or increased bone mineral density (BMD). Elevations in marrow adipose tissue (MAT) and declines in MAT unsaturation are both associated with increased skeletal fragility. The objective of our study was to characterize the quantity and composition of MAT in adults with morbid obesity and T2DM, and to evaluate determinants of MAT. We studied 21 adults with morbid obesity prior to bariatric surgery, 8 of whom had T2DM. All subjects underwent 1H-MR spectroscopy of the lumbar spine and femur for assessment of MAT and dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT) of the lumbar spine and hip for assessment of areal BMD (aBMD) and volumetric BMD (vBMD). Visceral (VAT) and subcutaneous adipose tissue (SAT) were quantified by CT at L1-L2. Subjects with T2DM had higher vBMD of the femoral neck and higher total MAT at the lumbar spine and femoral metaphysis compared to non-diabetic controls (p≤0.04). Lipid unsaturation index (UI) was significantly lower at the femoral diaphysis in T2DM (p=0.03). Within the entire cohort, HbA1c was positively associated with MAT (p≤0.03), and age was associated with higher MAT and lower MAT unsaturation (p≤0.05). Lumbar spine vBMD was inversely associated with lumbar spine MAT (p=0.04). There was an inverse association between SAT and diaphyseal MAT (p<0.05) while there were no associations with VAT. Subjects with morbid obesity and T2DM have higher MAT with a lower proportion of unsaturated lipids, despite higher femoral neck vBMD. MAT is positively associated with age and HbA1c, and inversely associated with vBMD, suggesting that MAT may serve as an imaging biomarker of skeletal health and metabolic risk.

Bone marrow adipose tissue as an endocrine organ: close to the bone?

White adipose tissue (WAT) is a major endocrine organ, secreting a diverse range of hormones, lipid species, cytokines and other factors to exert diverse local and systemic effects. These secreted products, known as 'adipokines', contribute extensively to WAT's impact on physiology and disease. Adipocytes also exist in the bone marrow (BM), but unlike WAT, study of this bone marrow adipose tissue (MAT) has been relatively limited. We recently discovered that MAT contributes to circulating adiponectin, an adipokine that mediates cardiometabolic benefits. Moreover, we found that MAT expansion exerts systemic effects. Together, these observations identify MAT as an endocrine organ. Additional studies are revealing further secretory functions of MAT, including production of other adipokines, cytokines and lipids that exert local effects within bone. These observations suggest that, like WAT, MAT has secretory functions with diverse potential effects, both locally and systemically. A major limitation is that these findings are often based on in vitro approaches that may not faithfully recapitulate the characteristics and functions of BM adipocytes in vivo. This underscores the need to develop improved methods for in vivo analysis of MAT function, including more robust transgenic models for MAT targeting, and continued development of techniques for non-invasive analysis of MAT quantity and quality in humans. Although many aspects of MAT formation and function remain poorly understood, MAT is now attracting increasing research focus; hence, there is much promise for further advances in our understanding of MAT as an endocrine organ, and how MAT impacts human health and disease.

Bone-Fat Interaction

Marrow adipose tissue (MAT) is a recently identified endocrine organ capable of modulating a host of responses. Given its intimate proximity to the bone microenvironment, the impact marrow adipocytes exert on bone has attracted much interest and scientific inquiry. Although many questions and controversies remain about marrow adipocytes, multiple conditions/disease states in which alterations occur have provided clues about their function. The consensus is that MAT is associated inversely with bone density and quality. While further investigation is warranted, MAT has clearly been demonstrated as an active dynamic depot that contributes to bone turnover and overall metabolic homeostasis.

Effects of Roux-en-Y gastric bypass and sleeve gastrectomy on bone mineral density and marrow adipose tissue

Bariatric surgery is associated with bone loss but skeletal consequences may differ between Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), the two most commonly performed bariatric procedures. Furthermore, severe weight loss is associated with high marrow adipose tissue (MAT); however, MAT is also increased in visceral adiposity. The purpose of our study was to determine the effects of RYGB and SG on BMD and MAT. We hypothesized that both bariatric procedures would lead to a decrease in BMD and MAT. We studied 21 adults with morbid obesity (mean BMI 44.1±5.1kg/m²) prior to and 12months after RYGB (n=11) and SG (n=10). All subjects underwent DXA and QCT of the lumbar spine and hip to assess aBMD and vBMD. Visceral (VAT) and subcutaneous (SAT) adipose tissue was quantified at L1-L2. MAT of the lumbar spine and femur was assessed by 1H-MR spectroscopy. Calcitropic hormones and bone turnover markers were determined. At 12months after surgery, mean weight and abdominal fat loss was similar between the RYGB and SG groups. Mean serum calcium, 25(OH)-vitamin D, and PTH levels were unchanged after surgery and within the normal range in both groups. Bone turnover markers P1NP and CTX increased within both groups and P1NP increased to a greater extent in the RYGB group (p=0.03). There were significant declines from baseline in spine aBMD and vBMD within the RYGB and SG groups, although the changes were not significantly different between groups (p=0.3). Total hip and femoral neck aBMD by DXA decreased to a greater extent in the RYGB than the SG group (p<0.04) although the change in femoral vBMD by QCT was not significantly different between groups (p>0.2). MAT content of the lumbar spine and femoral diaphysis did not change from baseline in the RYGB group but increased after SG (p=0.03). Within the SG group, 12-month change in weight and VAT were positively associated with 12-month change in MAT (p<0.04), suggesting that subjects with less weight and VAT loss had higher MAT. In conclusion, RYGB and SG are associated with declines in lumbar spine BMD, however, the changes are not significantly different between the groups. RYGB may be associated with greater decline of aBMD at the total hip and femoral neck compared to SG. MAT content increased after SG and this was associated with lower weight and VAT loss.

Do metabolic syndrome and its components have an impact on bone mineral density in adolescents?

In recent years, there has been growing concern about the occurrence of metabolic syndrome (MetS) at an early age and its effects on bone mass in adolescents. Adolescence is considered a critical period for bone mass gain. Impaired bone acquisition during this phase can lead to “suboptimal” peak bone mass and increase the risk of osteopenia/osteoporosis and fractures in old age. The objective of this review was to perform a critical analysis of articles that specifically focus on this age group, evaluating the influence of MetS and its components on bone mineral density in adolescents. A possible relationship between this syndrome and bone mass has been demonstrated, but the number of studies addressing this topic in adolescents is small. Despite the scarcity of evidence, the results of those studies show that Metabolic Syndrome is negatively correlated with bone mass and also that some components of MetS are negatively correlated with bone mineral density in adolescents. However, the associations between MetS and bone mass development need to be further explored in the age group corresponding to adolescence. Further good-quality studies are necessary to complement the understanding of this relationship.

Marrow Fat Quality Differences by Sex in Healthy Adults

Several studies have demonstrated the relationship between bone marrow adiposity (BMAT) and bone mass. ¹H magnetic resonance spectroscopy is a noninvasive technique able to assess both BMAT quantity and quality. The aim of our study was to perform quantitative and qualitative analyses of BMAT and to investigate its association with bone mineral density (BMD) in healthy nonobese volunteers. Fifty-one healthy volunteers, 21 men and 30 women, underwent 1.5 T ¹H magnetic resonance spectroscopy of the lumbar spine. BMD was determined by dual-energy X-ray absorptiometry of the lumbar spine. Correlation analysis was performed to evaluate association among lipids fractions, BMD, and age. The female and male volunteers had similar body mass index and BMD (p > 0.05). Our data demonstrated an inverse correlation of BMD and BMAT with age, with a stronger correlation of saturated lipids (r = 0.701; p < 0.0001) compared with unsaturated lipids (UL) (r = 0.278; p = 0.004). Importantly, female subjects had the highest amount of UL (confidence interval: 0.685%-1.722%; p < 0.001). Our study reports that men and women with similar BMD and body mass index have striking differences in bone marrow lipids composition, namely women have higher UL than men. In addition, we believe that our study brings new insights to the complex network involving BMAT and other factors that influence bone integrity.

Marrow adipose tissue spectrum in obesity and type 2 diabetes mellitus

OBJECTIVE

To assess the association of bone mass and marrow adipose tissue (MAT) with other fat depots, insulin resistance, bone remodeling markers, adipokines and glucose control in type 2 diabetes and obesity.

DESIGN AND METHODS

The study groups comprised 24 controls (C), 26 obese (O) and 28 type 2 diabetes. Dual-energy X-ray absorptiometry was used to determine bone mineral density (BMD). Blood samples were collected for biochemical measurements. ¹H Magnetic resonance spectroscopy was used to assess MAT in the L3 vertebra, and abdominal magnetic resonance imaging was used to assess intrahepatic lipids in visceral (VAT) and subcutaneous adipose tissue. Regression analysis models were used to test the association between parameters.

RESULTS

At all sites tested, BMD was higher in type 2 diabetes than in O and C subjects. The C group showed lower VAT values than the type 2 diabetes group and lower IHL than the O and type 2 diabetes groups. However, MAT was similar in the 3 groups. Osteocalcin and C-terminal telopeptide of type 1 collagen were lower in type 2 diabetes than those in C and O subjects. Moreover, at all sites, BMD was negatively associated with osteocalcin. No association was observed between MAT and VAT. No relationship was observed among MAT and HOMA-IR, leptin, adiponectin or Pref-1, but MAT was positively associated with glycated hemoglobin.

CONCLUSIONS

MAT is not a niche for fat accumulation under conditions of energy surplus and type 2 diabetes, also is not associated with VAT or insulin resistance. MAT is associated with glycated hemoglobin.

Diabetes and Bone Marrow Adiposity

PURPOSE OF REVIEW

This study aims to describe bone marrow fat changes in diabetes and to discuss the potential role of marrow fat in skeletal fragility.

RECENT FINDINGS

Advances in non-invasive imaging have facilitated marrow fat research in humans. In contrast to animal studies which clearly demonstrate higher levels of marrow fat in diabetes, human studies have shown smaller and less certain differences. Marrow fat has been reported to correlate with A1c, and there may be a distinct marrow lipid saturation profile in diabetes. Greater marrow fat is associated with impaired skeletal health. Marrow fat may be a mediator of skeletal fragility in diabetes. Circulating lipids, growth hormone alterations, visceral adiposity, and hypoleptinemia have been associated with greater marrow fat and may represent potential mechanisms for the putative effects of diabetes on marrow fat, although other factors likely contribute. Additional research is needed to further define the role of marrow fat in diabetic skeletal fragility and to determine whether marrow fat is a therapeutic target.

Body Fat and Physical Activity Modulate the Association Between Sarcopenia and Osteoporosis in Elderly Korean Women

This study examined whether modifiable lifestyle factors, such as body fatness and physical activity, modulate the association between sarcopenia and osteoporosis. In a cross-sectional design, 269 postmenopausal women, aged 65 years and older, underwent dual-energy X-ray absorptiometry (DEXA) scans to measure their body fat percentage, total fat mass, total fat-free mass, appendicular lean mass, bone mineral density (BMD) and bone mineral content. The participants wore a uniaxial accelerometer for seven consecutive days to quantify daily physical activity. The collected data were analyzed using descriptive statistics, Pearson correlation, and a binary logistic regression. Pearson correlation analyses showed that total neck/femur BMD was positively associated with weight-adjusted appendicular skeletal muscle mass (ASM) and objectively-measured physical activities. ASM was positively associated with body fatness. Binary logistic regression analyses showed that the odds ratio (OR) of sarcopenia for osteopenia and/or osteoporosis was substantially attenuated but remained marginally significant when adjusted for age and postmenopausal period (OR = 2.370 and p = 0.050). However, the OR was no longer significant when additionally adjusted for body fatness (OR = 2.218 and p = 0.117) and physical activity (OR = 1.240 and p = 0.448). The findings of the study showed that, in this sample of elderly Korean women, modifiable lifestyle risk factors such as body fatness and physical inactivity played an important role in determining the association between sarcopenia and osteopenia/osteoporosis.

Triglyceride Levels and Fracture Risk in Midlife Women: Study of Women's Health Across the Nation (SWAN)

CONTEXT

Unfavorable lipid levels contribute to cardiovascular disease and may also harm bone health.

OBJECTIVE

Our objective was to investigate relationships between fasting plasma lipid levels and incident fracture in midlife women undergoing the menopausal transition.

DESIGN AND SETTING

This was a 13-year prospective, longitudinal study of multiethnic women in five US communities, with near-annual assessments.

PARTICIPANTS

At baseline, 2062 premenopausal or early perimenopausal women who had no history of fracture were included.

EXPOSURES

Fasting plasma total cholesterol, triglycerides (TG), low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol at baseline and follow-up visits 1 and 3-7.

MAIN OUTCOME MEASURE(S)

Incident nontraumatic fractures 1) 2 or more years after baseline, in relation to a single baseline level of lipids; and 2) 2-5 years later, in relation to time-varying lipid levels. Cox proportional hazards modelings estimated hazard ratios and 95% confidence interval (CI).

RESULTS

Among the lipids, TG levels changed the most, with median levels increased by 16% during follow-up. An increase of 50 mg/dl in baseline TG level was associated with a 1.1-fold increased hazards of fracture (adjusted hazard ratio, 1.11; 95% CI, 1.04-1.18). Women with baseline TG higher than 300 mg/dl had an adjusted 2.5-fold greater hazards for fractures (95% CI, 1.13-5.44) than women with baseline TG lower than 150 mg/dl. Time-varying analyses showed a comparable TG level-fracture risk relationship. Associations between total cholesterol, low-density lipoprotein cholesterol, or high-density lipoprotein cholesterol levels and fractures were not observed.

CONCLUSIONS

Midlife women with high fasting plasma TG had an increased risk of incident nontraumatic fracture. Secondary Abstract: Midlife women with fasting plasma triglyceride (TG) of at least 300 mg/dl had 2.5-fold greater hazards of fracture in 2 years later and onward, compared to those with TG below 150 mg/dl, in a multiethnic cohort. Time-varying analyses revealed comparable results.

Marrow Adipose Tissue: Trimming the Fat

Marrow adipose tissue (MAT) is a unique fat depot, located in the skeleton, that has the potential to contribute to both local and systemic metabolic processes. In this review we highlight several recent conceptual developments pertaining to the origin and function of MAT adipocytes; consider the relationship of MAT to beige, brown, and white adipose depots; explore MAT expansion and turnover in humans and rodents; and discuss future directions for MAT research in the context of endocrine function and metabolic disease. MAT has the potential to exert both local and systemic effects on metabolic homeostasis, skeletal remodeling, hematopoiesis, and the development of bone metastases. The diversity of these functions highlights the breadth of the potential impact of MAT on health and disease.

BMI and BMD: The Potential Interplay between Obesity and Bone Fragility

Recent evidence demonstrating an increased fracture risk among obese individuals suggests that adipose tissue may negatively impact bone health, challenging the traditional paradigm of fat mass playing a protective role towards bone health. White adipose tissue, far from being a mere energy depot, is a dynamic tissue actively implicated in metabolic reactions, and in fact secretes several hormones called adipokines and inflammatory factors that may in turn promote bone resorption. More specifically, Visceral Adipose Tissue (VAT) may potentially prove detrimental. It is widely acknowledged that obesity is positively associated to many chronic disorders such as metabolic syndrome, dyslipidemia and type 2 diabetes, conditions that could themselves affect bone health. Although aging is largely known to decrease bone strength, little is yet known on the mechanisms via which obesity and its comorbidities may contribute to such damage. Given the exponentially growing obesity rate in recent years and the increased life expectancy of western countries it appears of utmost importance to timely focus on this topic.

Quantification of liver, pancreas, kidney, and vertebral body MRI-PDFF in non-alcoholic fatty liver disease

PURPOSE

The purpose of the present study was to determine liver, pancreas, kidney, and vertebral fat deposition in NAFLD patients by proton density fat fraction (PDFF) using magnetic resonance imaging (MRI) and to evaluate the relationships among them.

METHODS

A total of 41 biopsy-proven NAFLD patients underwent MRI-PDFF with IDEAL-IQ. MRI protocol included T1-independent volumetric multi-echo gradient-echo imaging with T2* correction and spectral fat modeling. The MR examinations were performed on a 1.5 HDx MRI system. MRI-PDFF measurements were obtained from liver, pancreas, renal cortex and sinus, and vertebral body. Liver biopsy specimens were retrieved from the archives and evaluated by one pathologist according to NASH CRN.

RESULTS

The median age of the patients was 47 years. The median interval between liver biopsy and MRI examination was 16 days. Mean liver, pancreas, renal cortex, renal sinus, T12 and L1 vertebral body MRI-PDFFs were 18.7%, 5.7%, 1.7%, 51%, 43.2%, and 43.5%, respectively. No correlation between either liver MRI-PDFF or histological steatosis, and other organ MRI-PDFFs was observed. A good correlation between pancreas and vertebral body MRI-PDFFs, and pancreas and renal sinus MRI-PDFFs was observed. Diabetic patients had higher average pancreas MRI-PDFF compared to non-diabetics (12.2%, vs., 4.8%; P = 0.028).

CONCLUSIONS

Pancreas and vertebral body MRI-PDFF is well correlated in NAFLD patients and both of them are higher in diabetic patients which may explain increased bone fractures in diabetics. MRI-PDFF can be used to demonstrate fat fractions of different organs and tissues and to understand fat metabolism.

High-fat diet-induced obesity stimulates ketone body utilization in osteoclasts of the mouse bone

Previous studies have shown that high-fat diet (HFD)-induced obesity increases the acetoacetyl-CoA synthetase (AACS) gene expression in lipogenic tissue. To investigate the effect of obesity on the AACS gene in other tissues, we examined the alteration of AACS mRNA levels in HFD-fed mice. In situ hybridization revealed that AACS was observed in several regions of the embryo, including the backbone region (especially in the somite), and in the epiphysis of the adult femur. AACS mRNA expression in the adult femur was higher in HFD-fed mice than in normal-diet fed mice, but this increase was not observed in high sucrose diet (HSD)-induced obese mice. In addition, HFD-specific increases were observed in the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and interleukin (IL)-6 genes. Moreover, we detected higher AACS mRNA expression in the differentiated osteoclast cells (RAW 264), and found that AACS mRNA expression was significantly up-regulated by IL-6 treatment only in osteoclasts. These results indicate the novel function of the ketone body in bone metabolism. Because the abnormal activation of osteoclasts by IL-6 induces bone resorption, our data suggest that AACS and ketone bodies are important factors in the relationship between obesity and osteoporosis.

MR-based assessment of body fat distribution and characteristics

The assessment of body fat distribution and characteristics using magnetic resonance (MR) methods has recently gained significant attention as it further extends our pathophysiological understanding of diseases including obesity, metabolic syndrome, or type 2 diabetes mellitus, and allows more detailed insights into treatment response and effects of lifestyle interventions. Therefore, the purpose of this study was to review the current literature on MR-based assessment of body fat distribution and characteristics. PubMed search was performed to identify relevant studies on the assessment of body fat distribution and characteristics using MR methods. T1-, T2-weighted MR Imaging (MRI), Magnetic Resonance Spectroscopy (MRS), and chemical shift-encoding based water-fat MRI have been successfully used for the assessment of body fat distribution and characteristics. The relationship of insulin resistance and serum lipids with abdominal adipose tissue (i.e. subcutaneous and visceral adipose tissue), liver, muscle, and bone marrow fat content have been extensively investigated and may help to understand the underlying pathophysiological mechanisms and the multifaceted obese phenotype. MR methods have also been used to monitor changes of body fat distribution and characteristics after interventions (e.g. diet or physical activity) and revealed distinct, adipose tissue-specific properties. Lastly, chemical shift-encoding based water-fat MRI can detect brown adipose tissue which is currently the focus of intense research as a potential treatment target for obesity. In conclusion, MR methods reliably allow the assessment of body fat distribution and characteristics. Irrespective of the promising findings based on these MR methods the clinical usefulness remains to be established.

Short- and long-term reproducibility of marrow adipose tissue quantification by 1H-MR spectroscopy

OBJECTIVE

To assess short- and long-term reproducibility of marrow adipose tissue (MAT) quantification by 1H-MR spectroscopy.

MATERIALS AND METHODS

Our study was IRB-approved and HIPAA compliant. Written informed consent was obtained. We studied 20 overweight/obese but otherwise healthy subjects (12 female, 8 male) with a mean age of 37 ± 6 years. All subjects underwent proton magnetic resonance spectroscopy (1H-MRS) of the fourth lumbar vertebral body using a single-voxel point-resolved spatially localized spectroscopy sequence without water suppression at 3 T. Measurements were repeated after 6 weeks and 6 months using identical scanning protocols. The following clinical parameters were collected, weight, BMI, exercise status, and trabecular bone mineral density (BMD), by quantitative computed tomography. Short- (baseline, 6 weeks) and long-term (baseline, 6 months) reproducibility of MAT was assessed by the coefficient of variance (CV), standard deviation (SD), and interclass correlation coefficients (ICCs). Short- and long-term changes in clinical parameters were assessed by paired t-test.

RESULTS

For short-term reproducibility between baseline and 6-week scans, the CV was 9.9 %, SD was 0.08, and ICC was 0.97 (95 % CI 0.94-099). For long-term reproducibility between baseline and 6-month scans, the CV was 12.0 %, SD was 0.10, and ICC was 0.95 (95 % CI 0.88 to 0.98). There was no significant short- or long-term change in clinical parameters (weight, BMI, exercise status, BMD) (p > 0.2).

CONCLUSION

1H-MRS is a reproducible method for short- and long-term quantification of MAT. Our results can guide sample size calculations for interventional and longitudinal studies.

Influences of teriparatide administration on marrow fat content in postmenopausal osteopenic women using MR spectroscopy

Objective Teriparatide could induce osteoblast differentiation of mesenchymal stem cells while inhibiting adipocyte differentiation. However, there are significant differences between ex vivo and in vivo models. We aimed to evaluate the impact of teriparatide on marrow and abdominal fat accumulation in postmenopausal osteopenic women. Methods Postmenopausal osteopenic women were randomly assigned to receive teriparatide or placebo for 12 months. Subcutaneous (SAT) and visceral adipose tissue (VAT), marrow fat fraction (MFF), bone density (BMD) and bone biomarkers were measured at baseline, 6 and 12 months. Results At 12 months, mean percentage changes in BMD from baseline were 3.51%, 2.21% and 1.80% at lumbar spine, total hip and femoral neck for the teriparatide group, respectively. Relative to baseline conditions, teriparatide reduced MFF (-3.54% at 6 months; -5.87% at 12 months, all p < 0.01). A significant difference in MFF, but not BMD, was first detected at 6 months (p = 0.012) between groups. MFF was negatively associated with SAT (r = -0.479) and positively associated with VAT (r = 0.531) and VAT/SAT (r = 0.415, all p < 0.05). Teriparatide treatment did not alter abdominal fat composition. Conclusion Teriparatide effectively lowers marrow adiposity but not abdominal fat accumulation in postmenopausal osteopenic women.

Impact of Obesity and Metabolic Syndrome on Immunity

Obesity is associated with metabolic disturbances that cause tissue stress and dysfunction. Obese individuals are at a greater risk for chronic disease and often present with clinical parameters of metabolic syndrome (MetS), insulin resistance, and systemic markers of chronic low-grade inflammation. It has been well established that cells of the immune system play an important role in the pathogenesis of obesity- and MetS-related chronic diseases, as evidenced by leukocyte activation and dysfunction in metabolic tissues such as adipose tissue, liver, pancreas, and the vasculature. However, recent findings have highlighted the substantial impact that obesity and MetS parameters have on immunity and pathogen defense, including the disruption of lymphoid tissue integrity; alterations in leukocyte development, phenotypes, and activity; and the coordination of innate and adaptive immune responses. These changes are associated with an overall negative impact on chronic disease progression, immunity from infection, and vaccine efficacy. This review presents an overview of the impact that obesity and MetS parameters have on immune system function.

Impact of Obesity and Metabolic Syndrome on Immunity

Obesity is associated with metabolic disturbances that cause tissue stress and dysfunction. Obese individuals are at a greater risk for chronic disease and often present with clinical parameters of metabolic syndrome (MetS), insulin resistance, and systemic markers of chronic low-grade inflammation. It has been well established that cells of the immune system play an important role in the pathogenesis of obesity- and MetS-related chronic diseases, as evidenced by leukocyte activation and dysfunction in metabolic tissues such as adipose tissue, liver, pancreas, and the vasculature. However, recent findings have highlighted the substantial impact that obesity and MetS parameters have on immunity and pathogen defense, including the disruption of lymphoid tissue integrity; alterations in leukocyte development, phenotypes, and activity; and the coordination of innate and adaptive immune responses. These changes are associated with an overall negative impact on chronic disease progression, immunity from infection, and vaccine efficacy. This review presents an overview of the impact that obesity and MetS parameters have on immune system function.

MR-Based Assessment of Bone Marrow Fat in Osteoporosis, Diabetes, and Obesity

Bone consists of the mineralized component (i.e., cortex and trabeculae) and the non-mineralized component (i.e., bone marrow). Most of the routine clinical bone imaging uses X-ray-based techniques and focuses on the mineralized component. However, bone marrow adiposity has been also shown to have a strong linkage with bone health. Specifically, multiple previous studies have demonstrated a negative association between bone marrow fat fraction (BMFF) and bone mineral density. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are ideal imaging techniques for non-invasively investigating the properties of bone marrow fat. In the present work, we first review the most important MRI and MRS methods for assessing properties of bone marrow fat, including methodologies for measuring BMFF and bone marrow fatty acid composition parameters. Previous MRI and MRS studies measuring BMFF and fat unsaturation in the context of osteoporosis are then reviewed. Finally, previous studies investigating the relationship between bone marrow fat, other fat depots, and bone health in patients with obesity and type 2 diabetes are presented. In summary, MRI and MRS are powerful non-invasive techniques for measuring properties of bone marrow fat in osteoporosis, obesity, and type 2 diabetes and can assist in future studies investigating the pathophysiology of bone changes in the above clinical scenarios.

Anti-adipogenic effects of sesamol on human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) from adult bone marrow are able to differentiate into adipocytes, osteoblasts, chondrocytes and neuronal cells. Adipocytes in bone marrow are primarily responsible for the maintenance of bone structure by maintaining cell number balance with other stromal cells. However, the number of adipocytes in the bone marrow increases with age, leading to an imbalance of the bone marrow microenvironment, which results in a disruption of bone structure. In addition, the excessive number of adipocytes in bone marrow can cause diseases, such as osteoporosis or anemia. In this study, we investigated the effect of sesamol, a major natural phenolic compound of sesame oil, on the adipogenic differentiation of hMSCs. Numerous studies have reported the anti-oxidant property of sesamol, but its effect on cell differentiation has not yet been shown. We first found that sesamol treatment during adipogenic differentiation of hMSCs reduced intracellular lipid accumulation, which was unrelated to lipolysis. Interestingly, sesamol diminished the expression of genes responsible for adipogenesis, but increased the expression of osteogenic genes. In addition, sesamol decreased the expression of genes necessary for adipocyte maturation without affecting the expression of hMSC-specific genes. Studies concerning intracellular signaling in hMSCs showed that the extracellular signal-regulated kinase 1/2 (ERK1/2) was decreased by sesamol, which was similar with the effect of an ERK1/2 inhibitor. Overall, this study demonstrates that sesamol can attenuate the adipogenic differentiation of hMSCs without affecting its characteristics through the inhibition of ERK1/2 pathway. Herein, this study reports for the first time the effect of sesamol on hMSC differentiation and suggests the possibility of using sesamol as a therapeutic agent to treat intraosseous disruption triggered by the excessive adipogenesis of hMSCs.

An Evolutionary and Life-History Perspective on Osteoporosis

Osteoporosis is a systemic disease characterized by bone mass reductions and heightened fracture risk; its global prevalence rates are projected to increase precipitously over the next few decades. Evolutionary and life-history perspectives have proven valuable for offering a different lens with which to consider the etiologies of common chronic diseases, and in this review, these approaches are applied to osteoporosis. Although there are many perspectives on human susceptibility to bone loss, this article explores the most prominent and empirically studied theories. Osteoporosis is considered within the context of theories on aging (e.g., antagonistic pleiotropy, disposable soma) and mismatch theory. Female vulnerability is considered within a separate evolutionary framework and has been articulated as a trade-off between reproduction and skeletal health. Recent advancements in bone imaging techniques for skeletal and living human and nonhuman primate populations (i.e., CT scans, ultrasonometry) have facilitated huge strides in contextualizing osteoporosis within evolutionary theory.

Greater Adipose Tissue Distribution and Diminished Spinal Musculoskeletal Density in Adults With Cerebral Palsy

OBJECTIVES

To examine differences in adipose tissue distribution, lumbar vertebral bone mineral density (BMD), and muscle attenuation in adults with and without cerebral palsy (CP), and to determine the associations between morphologic characteristics.

DESIGN

Cross-sectional, retrospective analyses of archived computed tomography scans.

SETTING

Clinical treatment and rehabilitation center.

PARTICIPANTS

Adults (N=352) with CP (age, 38.8±14.4y; body mass, 61.3±17.1kg; Gross Motor Function Classification System levels, I-V) and a matched cohort of neurotypical adults. Of the 41 adults with CP included in the study, 10 were not matchable because of low body masses.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Computed tomography scans were assessed for visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) areas, psoas major area and attenuation in Hounsfield units (Hu), and cortical and trabecular BMDs.

RESULTS

Adults with CP had lower cortical (β=-63.41 Hu, P<.001) and trabecular (β=-42.24 Hu, P<.001) BMDs and psoas major areas (β=-374.51mm(2), P<.001) and attenuation (β=-9.21 Hu, P<.001) after controlling for age, sex, and body mass. Adults with CP had greater VAT (β=3914.81mm(2), P<.001) and SAT (β=4615.68mm(2), P<.001). Muscle attenuation was significantly correlated with trabecular (r=.51, P=.002) and cortical (r=.46, P<.01) BMD, whereas VAT was negatively associated with cortical BMD (β=-.037 Hu/cm(2), r(2)=.13, P=.03).

CONCLUSIONS

Adults with CP had lower BMDs, smaller psoas major area, greater intermuscular adipose tissue, and greater trunk adiposity than neurotypical adults. VAT and cortical BMD were inversely associated.

The Relationship of Fat Distribution and Insulin Resistance with Lumbar Spine Bone Mass in Women

Bone marrow harbors a significant amount of body adipose tissue (BMAT). While BMAT might be a source of energy for bone modeling and remodeling, its increment can also represent impairment of osteoblast differentiation. The relationship between BMAT, bone mass and insulin sensitivity is only partially understood and seems to depend on the circumstances. The present study was designed to assess the association of BMAT with bone mineral density in the lumbar spine as well as with visceral adipose tissue, intrahepatic lipids, HOMA-IR, and serum levels of insulin and glucose. This cross-sectional clinical investigation included 31 non-diabetic women, but 11 had a pre-diabetes status. Dual X-ray energy absorptiometry was used to measure bone mineral density and magnetic resonance imaging was used to assess fat deposition in BMAT, visceral adipose tissue and liver. Our results suggest that in non-diabetic, there is an inverse relationship between bone mineral density in lumbar spine and BMAT and a trend persists after adjustment for weight, age, BMI and height. While there is a positive association between visceral adipose tissue and intrahepatic lipids with serum insulin levels, there is no association between BMAT and serum levels of insulin. Conversely, a positive relationship was observed between BMAT and serum glucose levels, whereas this association was not observed with other fat deposits. These relationships did not apply after adjustment for body weight, BMI, height and age. The present study shows that in a group of predominantly non-obese women the association between insulin resistance and BMAT is not an early event, as occurs with visceral adipose tissue and intrahepatic lipids. On the other hand, BMAT has a negative relationship with bone mineral density. Taken together, the results support the view that bone has a complex and non-linear relationship with energy metabolism.

Marrow Adipose Tissue Quantification of the Lumbar Spine by Using Dual-Energy CT and Single-Voxel (1)H MR Spectroscopy: A Feasibility Study

PURPOSE

To test the performance of dual-energy computed tomography (CT) in the assessment of marrow adipose tissue (MAT) content of the lumbar spine by using proton (hydrogen 1 [(1)H]) magnetic resonance (MR) spectroscopy as a reference standard and to determine the influence of MAT on the assessment of bone mineral density (BMD).

MATERIALS AND METHODS

This study was institutional review board approved and complied with HIPAA guidelines. Written informed consent was obtained. Twelve obese osteopenic but otherwise healthy subjects (mean age ± standard deviation, 43 years ± 13) underwent 3-T (1)H MR spectroscopy of the L2 vertebra by using a point-resolved spatially localized spectroscopy sequence without water suppression. The L2 vertebra was scanned with dual-energy CT (80 and 140 kV) by using a dual-source multi-detector row CT scanner with a calibration phantom. Mean basis material composition relative to the phantom was estimated in the L2 vertebra. Volumetric BMD was measured with and without correction for MAT. Bland-Altman 95% limits of agreement and Pearson correlation coefficients were calculated.

RESULTS

There was excellent agreement between (1)H MR spectroscopy and dual-energy CT, with a mean difference in fat fraction of -0.02 between the techniques, with a 95% confidence interval of -0.24, 0.20. There was a strong correlation between marrow fat fraction obtained with (1)H MR spectroscopy and that obtained with dual-energy CT (r = 0.91, P < .001). The presence of MAT led to underestimation of BMD, and this bias increased with increasing MAT content (P < .001).

CONCLUSION

Dual-energy CT can be used to assess MAT content and BMD of the lumbar spine in a single examination and provides data that closely agree and correlate with (1)H MR spectroscopy data.