Associations between fat distribution and volumetric bone mineral density in Chinese adults

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

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

Feasibility analysis of low-dose CT with asynchronous quantitative computed tomography to assess vBMD

BACKGROUND

To explore the feasibility of low-dose computed tomography (LDCT) with asynchronous quantitative computed tomography (asynchronous QCT) for assessing the volumetric bone mineral density (vBMD).

METHODS

416 women patients, categorized into 4 groups, were included and underwent chest CT examinations combined with asynchronous QCT, and CT scanning dose protocols (LDCT or CDCT) were self-determined by the participants. Radiation dose estimations were retrieved from patient protocols, including volume CT dose index (CTDIvol) and dose-length-product (DLP), and then calculated effective dose (ED). Delimiting ED by 1.0 mSv, chest CT examinations were categorized into 2 groups, LDCT group and CDCT group. vBMD of T12-L2 was obtained by transferring the LDCT and CDCT images to the QCT workstation, without extra radiation.

RESULTS

There was no difference of vBMD among 4 age groups in LDCT group (P = 0.965), and no difference in CDCT group (P = 0.988). In LDCT group and CDCT group, vBMD was not correlated to mAs, CTDIvol and DLP (P > 0.05), respectively. Between LDCT group and CDCT group, there was no difference of vBMD (P ≥ 0.480), while differences of mAs, CTDIvol and DLP.

CONCLUSION

There was no difference of vBMD between LDCT group and CDCT group and vBMD was not correlated to mAs. While screening for diseases such as lung cancer and mediastinal lesions, LDCT combined with asynchronous QCT can be also used to assess vBMD simultaneously with no extra imaging equipment, patient visit time, radiation dose and no additional economic cost.

Association of visceral and subcutaneous fat with bone mineral density in US adults: a cross-sectional study

The relationship between the accumulation of fat in visceral or subcutaneous tissue and bone mineral density (BMD) remains unclear. Our primary objective in this study was to illuminate this relationship by conducting an investigation on a vast scale, encompassing a nationally representative population in the United States. A weighted multiple linear regression model was established to evaluate the relationship between visceral fat, subcutaneous fat, and BMD. Additionally, the exploration of the potential nonlinear relationship was conducted employing the methodology of smooth curve fitting. In order to determine potential inflection points, a two-stage linear regression model was utilized. A total of 10,455 participants between the ages of 20 and 59 were included in this study. Various weighted multiple linear regression models revealed a negative correlation between lumbar BMD and visceral mass index (VMI) and subcutaneous mass index (SMI). However, the association between VMI and lumbar BMD displayed a U-shaped pattern upon employing the smooth curve fitting, and the inflection point of 0.304 kg/m2was determined using a two-stage linear regression model. Our findings indicated a negative association between subcutaneous fat and BMD. A U-shaped relationship was observed between visceral fat and BMD.

Associations of visceral adipose tissue with bone mineral density and fracture: observational and Mendelian randomization studies

BACKGROUND

The associations between visceral adipose tissue (VAT) and bone mineral density (BMD) or fracture have been controversial and the causality of the associations remains to be assessed. This study aimed to explore the associations of VAT^ (predicted value of VAT mass) with BMD and fracture risk in men and women, and to examine their potential causation by two-sample Mendelian randomization (MR) analyses.

METHODS

UK Biobank is a large, population-based prospective cohort study that recruited more than 500,000 participants aged 40-69 in the United Kingdom from 2006 to 2010. In this study, we used a validated and reliable prediction model to estimate the VAT amount of the participants. On this basis, linear and nonlinear multivariable statistical models were used to explore the association of VAT^ with BMD and fracture risk in different groups of sex and BMI. In observational analyses, the multivariable linear regression model and Cox proportional-hazards model were used to assess VAT^ association with BMD and fracture risk, respectively. Inverse variance weighting was used as the main result of MR analysis.

RESULTS

In 190,836 men, an inverted U-shaped association was observed between VAT^ and heel BMD (P for nonlinearity < 0.001), with a turning point of VAT^ = 1.25 kg. Per kg increase in VAT^ was associated with a 0.13 standard deviation (SD) increase in heel BMD (P = 1.5 × 10^-16) among men with lower amounts of VAT^, and associated with a 0.05 SD decrease in heel BMD (P = 1.3 × 10^-15) among men with higher amounts of VAT^. In 193,592 women, per kg increase in VAT^ was monotonically associated with a 0.16 SD increase in heel BMD (P = 1.2 × 10^-136, P for VAT^-sex interaction = 8.4 × 10^-51). During a median follow-up of 8.2 years, VAT^ was associated with lower risks of hip fractures in the overall men and women (P for VAT^-sex interaction = 1.9 × 10^-4 for total fractures; 1.5 × 10^-4 for other fractures). There were significant interactions of VAT^ and BMI on heel BMD and fracture risks in men only (P for VAT^-BMI interaction = 5.9 × 10^-31 for heel BMD; 2.7 × 10^-4 for total fractures; 5.7 × 10^-3 for hip fractures; 6.8 × 10^-3 for other fractures). In two-sample MR analyses, evidence of causality was not observed between VAT^ and DXA-derived BMD or fractures.

CONCLUSIONS

These novel findings demonstrated gender-dependent associations of VAT^ with BMD and fracture risk, with the association in men being modified by adiposity. Evidence of causality was not observed, suggesting that the observational association of VAT^ with BMD and fracture risk could be the result of confounding.

The association between body fat distribution and bone mineral density: evidence from the US population

OBJECTIVE

To investigate the association between different body fat distribution and different sites of BMD in male and female populations.

METHODS

Use the National Health and Nutrition Examination Survey (NHANES) datasets to select participants. The weighted linear regression model investigated the difference in body fat and Bone Mineral Density (BMD) in different gender. Multivariate adjusted smoothing curve-fitting and multiple linear regression models were used to explore whether an association existed between body fat distribution and BMD. Last, a subgroup analysis was performed according to age and gender group.

RESULTS

Overall, 2881 participants were included in this study. Compared to males, female participants had lower BMD (P < 0.05) and higher Gynoid fat mass (P < 0.00001), while there was no difference between Android fat mass (P = 0.91). Android fat mass was positively associated with Total femur BMD (Males, β = 0.044, 95% CI = 0.037, 0.051, P < 0.00001; Females, β = 0.044, 95% CI = 0.039, 0.049, P < 0.00001), Femoral neck BMD (Males, β = 0.034, 95% CI = 0.027, 0.041, P < 0.00001; Females, β = 0.032, 95% CI = 0.027, 0.037, P < 0.00001), and Total spine BMD (Males, β = 0.036, 95% CI = 0.029, 0.044, P < 0.00001; Females, β = 0.025, 95% CI = 0.019, 0.031, P < 0.00001). The Gynoid fat mass, subgroup analysis of age and ethnicity reached similar results.

CONCLUSION

Body fat in different regions was positively associated with BMD in different sites, and this association persisted in subgroup analyses across age and race in different gender.

Biomechanical analysis of vertebral wedge deformity in elderly women with quantitative CT-based finite element analysis

BACKGROUND

To explore the vertebral deformity angle (VD angle) of 1^st lumbar vertebral body (L1) in elderly women, investigate the influence of VD on vertebral stiffness (VS) by biomechanical analysis using quantitative computed tomography-based finite element analysis (QCT-FEA).

METHODS

Two hundred seventy eight participants were recruited, and underwent QCT scan. Measured VD angles of L1, and constructed QCT-FEA models of L1 with the minimum (0.59°), median (5.79°) and maximum (11.15°) VD angles, respectively. Loads in two directions were applied on the upper edge of L1 with a force of 700 N, and vertebral stiffness (VS) was defined as the ratio of 700 N and displacement at the superior reference point: (1) perpendicular to the upper edge of L1 (defined as VS-U); (2) perpendicular to the lower edge of L1(defined as VS-L).

RESULTS

Age was very weak positively correlated with VD angle, moderate negatively correlated with vBMD, and moderate negatively correlated with VS (P < 0.05). VS-U was significantly different among three VD angles, so was VS-L (P < 0.001). VS-U was higher than VS-L in 5.79° and 11.15° VD angles (P < 0.05), however no difference in 0.59° VD angles (P > 0.10).

CONCLUSIONS

VD angle of L1 was slightly increased with age and not correlated with vBMD, and VS was moderate negatively correlated with age, showing that the vertebral body was more likely to fracture with aging. VS-U and VS-L were gradually decreased with the increase of VD angle, and VS-L was lower than VS-U with the increase of VD angle, which showed that vertebral body was more prone to fracture when the load was perpendicular to the lower edge of the vertebral body as the VD angle increasing.

The associations between body fat distribution and bone mineral density in the Oxford Biobank: a cross sectional study

BACKGROUND

Body composition is associated with bone mineral density (BMD), but the precise associations between body fat distribution and BMD remain unclear. The regional adipose tissue depots have different metabolic profiles. We hypothesized that they would have independent associations with BMD.

RESEARCH DESIGN AND METHODS

We used data from 4,900 healthy individuals aged 30-50 years old from the Oxford Biobank to analyze associations between regional fat mass, lean mass and total BMD.

RESULTS

Total lean mass was strongly positively associated with BMD. An increase in total BMD was observed with increasing mass of all the fat depots, as measured either by anthropometry or DXA, when accounting for lean mass. However, on adjustment for both total fat mass and lean mass, fat depot specific associations emerged. Increased android and visceral adipose tissue mass in men, and increased visceral adipose tissue mass in women, were associated with lower BMD.

CONCLUSIONS

Fat distribution alters the association between adiposity and BMD.

How Does Obesity Influence the Risk of Vertebral Fracture? Findings From the UK Biobank Participants

Obesity and osteoporotic‐related fractures are two common public health problems, although it is unclear how obesity affects the risk of vertebral fractures. The purpose of this study was to examine the association between different measures of obesity and the risk of vertebral fracture, and to establish the various clinical factors that can predict such risk. We analyzed data obtained from 502,543 participants in the UK Biobank (229,138 men and 273,405 women), aged 40 to 69 years. Imaging information was available in a subset of this cohort (5189 participants: 2473 men and 2716 women). We further examined how BMD and geometry of the vertebrae were related to body fat measures. It was shown that a larger waist circumference (WC), but not BMI, was associated with an increase in fracture risk in men, but in women, neither BMI nor WC affected the risk. Trunk fat mass, visceral adipose tissue (VAT) mass, and limb fat mass were negatively associated with vertebral body BMD and geometry in men and women. BMD and geometry are related to vertebral strength, but may not be directly related to the risk of fractures, which is also influenced by other factors. The binary logistic regression equation established in this study may be useful to clinicians for the prediction of vertebral fracture risks, and may provide further information to supplement the fracture risk assessment tool, which assesses general fracture risks. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Contribution of Android and Gynoid Adiposity to Bone Mineral Density in Healthy Postmenopausal Thai Women

Dual-energy X-ray absorptiometry (DXA) is one of the major tools for assessing the whole body and regional body composition and body adiposity. Various body composition parameters including android fat mass (AFM), gynoid fat mass (GFM), and android-to-gynoid fat ratio (AG fat ratio) obtained from whole body DXA can be used as a reliable surrogate marker for regional body composition analysis. This study aimed to explore the contribution of android and gynoid adiposity to bone mineral density (BMD) in healthy postmenopausal Thai women. This cross-sectional study enrolled 1448 healthy Thai women, ages 40-90 without medication history or known disease affecting the BMD. Lumbar spine (LS), total femur, and femoral neck BMDs, AFM, GFM, and AG fat ratio were measured by DXA. To evaluate the contribution of android and gynoid adiposity with various measures of BMDs, univariable and multivariable linear regression analyses were used to estimate the regression coefficients. AFM, GFM, and AG fat ratio had a significant positive association with BMD of all measured sites (p < 0.001) in the univariate analysis. The strongest association was found between AG fat ratio and LS BMD (β = 0.156, p ≤ 0.001). In multivariate linear regression analysis, the results continued to show a positive association between AFM and GFM at all skeletal sites after adjusting for age, height, and total body lean mass. Relationship between AG fat ratio and BMD was found only in LS region. GFM had a strongest positive effect with BMD at the LS, total femur, and femoral neck regions. Higher android and gynoid adiposity was associated with higher BMD. GFM rather than AFM shows the strongest positive association with BMDs in postmenopausal Thai women.

Vertebral Strength and Estimated Fracture Risk Across the BMI Spectrum in Women

Somewhat paradoxically, fracture risk, which depends on applied loads and bone strength, is elevated in both anorexia nervosa and obesity at certain skeletal sites. Factor-of-risk (Φ), the ratio of applied load to bone strength, is a biomechanically based method to estimate fracture risk; theoretically, higher Φ reflects increased fracture risk. We estimated vertebral strength (linear combination of integral volumetric bone mineral density [Int.vBMD] and cross-sectional area from quantitative computed tomography [QCT]), vertebral compressive loads, and Φ at L4 in 176 women (65 anorexia nervosa, 45 lean controls, and 66 obese). Using biomechanical models, applied loads were estimated for: 1) standing; 2) arms flexed 90°, holding 5 kg in each hand (holding); 3) 45° trunk flexion, 5 kg in each hand (lifting); 4) 20° trunk right lateral bend, 10 kg in right hand (bending). We also investigated associations of Int.vBMD and vertebral strength with lean mass (from dual-energy X-ray absorptiometry [DXA]) and visceral adipose tissue (VAT, from QCT). Women with anorexia nervosa had lower, whereas obese women had similar, Int.vBMD and estimated vertebral strength compared with controls. Vertebral loads were highest in obesity and lowest in anorexia nervosa for standing, holding, and lifting (p < 0.0001) but were highest in anorexia nervosa for bending (p < 0.02). Obese women had highest Φ for standing and lifting, whereas women with anorexia nervosa had highest Φ for bending (p < 0.0001). Obese and anorexia nervosa subjects had higher Φ for holding than controls (p < 0.03). Int.vBMD and estimated vertebral strength were associated positively with lean mass (R = 0.28 to 0.45, p ≤ 0.0001) in all groups combined and negatively with VAT (R = -[0.36 to 0.38], p < 0.003) within the obese group. Therefore, women with anorexia nervosa had higher estimated vertebral fracture risk (Φ) for holding and bending because of inferior vertebral strength. Despite similar vertebral strength as controls, obese women had higher vertebral fracture risk for standing, holding, and lifting because of higher applied loads from higher body weight. Examining the load-to-strength ratio helps explain increased fracture risk in both low-weight and obese women.

Increased bone mineral density according to increase of skeletal muscle mass in 534 Korean women: A retrospective cohort study conducted over 2.7 years

OBJECTIVE

To determine the impact of the changes in the amount of abdominal fat, directly measured by computed tomography, body composition, and the metabolic syndrome (MetS) risk factors on the bone mineral density (BMD) of Korean women.

METHODS

A retrospective cohort study involving 534 Korean women aged 29 to 78 years, who had undergone both dual-energy X-ray absorptiometry and abdominal adipose tissue analysis by computed tomography scan more than twice between January 2004 and December 2010. The changes in the BMD values were examined in association with the changes in fat amount, body composition parameters, and risk factors of MetS.

RESULTS

On cross sectional analysis, there was a significant positive correlation between femoral BMD and total abdominal fat amount at the initial visit. However, the correlation disappeared when the impact of change of the fat amount on the change in BMD was analyzed over the study period. When the MetS and body composition parameters were analyzed, a significantly positive correlation was found between skeletal muscle mass and BMD. There was no significant relationship between the MetS risk factors or other body composition parameters and BMD throughout the study period after adjusting for age (time interval).

CONCLUSION

Among body composition parameters, only increased skeletal muscle mass had a positive correlation with increased BMD over the study period of 2.7 years.