Dual-energy X-ray Absorptiometry Measurements Research Articles

Changes in the Visceral Adiposity Index (VAI) Among Obese Older Adults After a 12-Month Exercise and Diet Intervention

ObjectivesThe Visceral Adiposity Index (VAI) was developed to estimate adipose tissue dysfunction as well as visceral fat distribution. In an ancillary analysis of the CROSSROADS Study (clinicaltrials.gov #NCT00955903), this study investigated the effects of exercise with and without intentional energy restriction on VAI changes among older adults with obesity. MethodsParticipants (n = 163, 37.4% male, 70.3 ± 4.7 years) were randomized to the following groups: exercise only, exercise + nutrient-dense weight maintenance diet, and exercise + nutrient-dense energy restriction of 500 kcal/d. Visceral adiposity determined by magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA), anthropometrics, and cardiometabolic biomarkers were assessed at baseline and 12 months. Waist circumference, body mass index, triglycerides, and high-density lipoprotein (HDL) cholesterol were used to compute VAI at both time points. Data were analyzed utilizing Spearman’s correlations and general linear models to determine differences among groups following adjustment for covariates. ResultsAmong all participants, significant correlations were observed between VAI and glucose, insulin, tumor necrosis factor-alpha (TNF-α), and the adiponectin: leptin ratio at baseline (r = 0.343, P < 0.001; r = 0.363, P < 0.001; r = 0.200, P = 0.011; r = –0.246, P = 0.002, respectively). DXA and MRI measures of visceral adiposity were not significantly correlated with VAI. Upon completion of the 12-month study period, there were significant differences in VAI among groups [F (2,137) = 5.957, P = 0.003)]. Post hoc analysis revealed that VAI was significantly lower in the exercise + nutrient-dense energy restriction group compared to the exercise only group (P = 0.002). ConclusionsResults suggest that VAI may be an adequate measure of adipose tissue dysfunction, yet its ability to estimate levels of visceral adiposity warrants further investigation to determine clinical utility. Nonetheless, results suggest that an exercise + nutrient-dense energy restriction intervention may reduce VAI among older adults with obesity. Funding SourcesNIH.

Accuracy of dual-energy x-ray absorptiometry for assessing longitudinal change in visceral adipose tissue in patients with coronary artery disease.

Visceral adipose tissue (VAT) is a key target of interventions for obesity-related diseases. Dual-energy x-ray absorptiometry (DXA) can estimate VAT, however its accuracy to measure longitudinal change in VAT compared to gold-standard techniques such as magnetic resonance imaging (MRI), has not been studied in adults. This study aimed to determine the accuracy of DXA compared with gold-standard MRI for cross-sectional VAT assessment, and for detecting longitudinal change in VAT. Adults with coronary artery disease (64 ± 8 years; BMI 27.8 ± 3.5 kg/m2; 88% male) were assessed for VAT by DXA and MRI at baseline (n = 34) and during implementation of an exercise intervention study at 3- and 12-months (n = 29). To match the 5.2 cm DXA measurement site for Hologic software (InnerCoreTM), VAT cross-sectional area (CSA) was measured by MRI using a single slice at L4/L5 junction, and VAT volume measured by 10 × 5 mm slices over the L4/L5 junction. MRI slices were quantified for VAT using semi-automated specialised software. Relationships between DXA and MRI for cross-sectional VAT and longitudinal change in VAT were determined by linear regression. Accuracy between the methods was assessed by Bland-Altman analysis, with data presented as mean difference (95% confidence interval), lower and upper limits of agreement (LoA). Strong correlations were found between DXA-VAT and MRI-VAT at baseline (r = 0.90; p < 0.001), and longitudinal change in DXA-VAT and MRI-VAT over 3- and 12-months (r = 0.67; p < 0.001). In contrast, Bland-Altman analysis revealed significant overestimation by DXA-VAT volume at baseline by 13% [-104 cm3 (-157, -52 cm3), p < 0.001; LoA (-398, 189 cm3)], and underestimation of change in DXA-VAT volume over 3-months by 33% [-41 cm3 (-77, -4 cm3), p = 0.030; LoA (-228, 147 cm3)] and 12-months by 47% [-65 cm3 (-114, -17 cm3), p = 0.010; LoA (-316, 185 cm3)]. Results were similar for VAT CSA. Compared with MRI, DXA substantially underestimated longitudinal changes in VAT. Therefore, DXA is not currently a valid alternative to MRI for quantifying VAT changes and may under-represent the effectiveness of interventions for obesity management.

Predictive equation for assessing appendicular lean soft tissue mass using bioelectric impedance analysis in older adults: Effect of body fat distribution.

Low muscle mass is associated with sarcopenia and increased mortality. Muscle mass, especially that of the limbs, is commonly estimated by dual-energy X-ray absorptiometry (DXA) or bioimpedance analysis (BIA). However, BIA-based predictive equations for estimating lean appendicular soft tissue mass (ALST) do not take into account body fat distribution, an important factor influencing DXA and BIA measurements. To develop and cross-validate a BIA-based equation for estimating ALST with DXA as criterion, and to compare our new formula to three previously published models. One-hundred eighty-four older adults (140 women and 44 men) (age 71.5 ± 7.3 years, body mass index 27.9 ± 5.3 kg/m2) were recruited. Participants were randomly split into validation (n = 118) and cross-validation groups (n = 66). Bioelectrical resistance was obtained with a phase-sensitive 50 kHz BIA device. A BIA-based model was developed for appendicular lean soft tissue mass [ALST (kg) = 5.982 + (0.188 × S2 / resistance) + (0.014 × waist circumference) + (0.046 × Wt) + (3.881 × sex) - (0.053 × age), where sex is 0 if female or 1 if male, Wt is weight (kg), and S is stature (cm) (R2 = 0.86, SEE = 1.35 kg)]. Cross validation revealed r2 of 0.91 and no mean bias. Two of three previously published models showed a trend to significantly overestimate ALST in our sample (p < 0.01). The new equation can be considered valid, with no observed bias and trend, thus affording practical means to quantify ALST mass in older adults.

Measurements of Bone Health after Thyroid-Stimulating Suppression Therapy in Postmenopausal Women with Differentiated Thyroid Carcinoma: Bone Mineral Density versus the Trabecular Bone Score

Background: Thyroid-stimulating hormone (TSH) suppression therapy is an important treatment modality for differentiated thyroid carcinoma (DTC), but it increases fracture risk. The aim of this study was to evaluate changes in bone mineral density (BMD) and trabecular bone score (TBS) in postmenopausal DTC patients receiving TSH suppression therapy. Methods: A total of 410 postmenopausal DTC patients who underwent thyroidectomy and had at least two dual-energy X-ray absorptiometry measurements, including a preoperative measurement, were included. Patients who had osteoporosis medication for more than 1 year were classified as ‘patients with osteoporosis’. Results: In patients without osteoporosis, the change in %BMD was similar between TSH suppression (−) and (+) groups, while the decrease in %TBS was significantly greater in the TSH suppression (+) group than that of the TSH suppression (−) group. The relative risk of vertebral fracture was decreased by TBS changes but not by BMD changes. In patients with osteoporosis, both BMD and TBS showed significant increases in the TSH suppression (−) group but not in TSH suppression (+) group. At year 4, TBS was significantly lower in the TSH suppression (+) group than that in the TSH suppression (−) group, while BMD showed no difference between groups. Conclusions: TBS may better reflect bone health than BMD in postmenopausal DTC patients with TSH suppression therapy.

Risk Factors of Metabolic Syndrome among Polish Nurses.

The metabolic syndrome, also known as syndrome X or the insulin resistance, is defined by the World Health Organization as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Both all over the world and in Poland, there is a shortage of nurses; most of those employed are in the pre-retirement age. However, the requirements in this profession and the patient’s right to care at the highest level remain unchanged and do not take into account the poor condition or age of working nurses, so special attention should be paid to the state of health in this professional group. There is an emphasis on the importance of the adopted attitude toward health and the resulting behaviors, such as regular weight control, following dietary recommendations, regular physical activity and participation in preventive examinations. The aim of the study was to assess the frequency of the occurrence of the metabolic syndrome, its individual components and determining the factors influencing its development in Polish nurses. The research conducted among the nurses in question included DXA (Dual Energy X-ray Absorptiometry) measurements, assessment of glucose concentration, lipid profile, blood pressure and a questionnaire survey. Almost half of the surveyed nurses have metabolic syndrome, which significantly increases the risk of developing cardiovascular diseases or diabetes. After multivariate analysis, it was found that being overweight and obesity were significant factors influenced the MS (metabolic syndrome) occurrence among Polish nurses. Being overweight increases the chances of MS occurrence 8.58 times in relation to BMI (Body Mass Index) <25, obesity increases the chances of MS occurrence 8.085 times in relation to BMI <25, and obesity class II/III increases the chances of MS occurrence 16.505 times in relation to BMI <25. Preventive and supportive measures for this professional group are needed.

Current Applications and Selected Technical Details of Dual-Energy X-Ray Absorptiometry.

The application of dual-energy X-ray absorptiometry (DXA) examinations in the assessment of bone mineral density (BMD) in the lumbar spine, hip, and forearm is the basic diagnostic method for recognition of osteoporosis. The constant development of DXA technique is due to the aging of societies and the increasing importance of osteoporosis as a public health problem. In order to assess the degree of bone demineralization in patients with hyperparathyroidism, forearm DXA examination is recommended. The vertebral fracture assessment (VFA) of the thoracic and lumbar spine, performed by a highly-skilled technician, is an interesting alternative to the X-ray examination. The DXA total body examination can be useful in the evaluation of fat redistribution among patients after bariatric surgery, in patients infected with HIV and receiving antiretroviral therapy, and in patients with metabolic diseases and suspected to have sarcopenia. The assessment of visceral adipose tissue (VAT) and detection of abdominal aortic calcifications may be useful in the prediction of cardiovascular events. The positive effect of anti-resorptive therapy may affect some parameters of DXA hip structure analysis (HSA). Long-term anti-resorptive therapy, especially with the use of bisphosphonates, may result in changes in the DXA image, which may herald atypical femur fractures (AFF). Reduction of the periprosthetic BMD in the DXA measurements can be used to estimate the likelihood of loosening the prosthesis and periprosthetic fractures. The present review aims to present current applications and selected technical details of DXA.

Quantification of adipose tissues by Dual-Energy X-Ray Absorptiometry and Computed Tomography in colorectal cancer patients

Excess adipose tissue may affect colorectal cancer (CRC) patients' disease progression and treatment. In contrast to the commonly used anthropometric measurements, Dual-Energy X-Ray Absorptiometry (DXA) and Computed Tomography (CT) can differentiate adipose tissues. However, these modalities are rarely used in the clinic despite providing high-quality estimates. This study aimed to compare DXA's measurement of abdominal visceral adipose tissue (VAT) and fat mass (FM) against a corresponding volume by CT in a CRC population. Secondly, we aimed to identify the best single lumbar CT slice for abdominal VAT. Lastly, we investigated the associations between anthropometric measurements and VAT estimated by DXA and CT. Non-metastatic CRC patients between 50-80 years from the ongoing randomized controlled trial CRC-NORDIET were included in this cross-sectional study. Corresponding abdominal volumes were acquired by Lunar iDXA and from clinically acquired CT examinations. Also, single CT slices at L2-, L3-and L4-level were obtained. Agreement between the methods was investigated using univariate linear regression and Bland-Altman plots. Sixty-six CRC patients were included. Abdominal volumetric VAT and FM measured by DXA explained up to 91% and 96% of the variance in VAT and FM by CT, respectively. Bland-Altman plots demonstrated an overestimation of VAT by DXA compared to CT (mean difference of 76cm3) concurrent with an underestimation of FM (mean difference of-319 cm3). A higher overestimation of VAT (p=0.015) and underestimation of FM (p=0.036) were observed in obese relative to normal weight subjects. VAT in a single slice at L3-level showed the highest explained variance against CT volume (R2=0.97), but a combination of three slices (L2, L3, L4) explained a significantly higher variance than L3 alone (R2=0.98, p<0.006). The anthropometric measurements explained between 31-65% of the variance of volumetric VAT measured by DXA and CT. DXA and the combined use of three CT slices (L2-L4) are valid to predict abdominal volumetric VAT and FM in CRC patients when using volumetric CT as a reference method. Due to the poor performance of anthropometric measurements we recommend exploring the added value of advanced body composition by DXA and CT integrated into CRC care.

Bone quality assessed by trabecular bone score in severe anorexia nervosa: A brief report.

Low bone mineral density (BMD) in anorexia nervosa (AN) leads to increased risk of fractures. Debate exists whether to medicinally treat young patients with AN based on abnormal dual-energy x-ray absorptiometry (DXA) scores or to weight restore and reassess when older. Trabecular bone score (TBS), a technology measuring bone quality, is used in conjunction with DXA. This report explores the potential additional value of TBS, in adults with severe AN, to augment the DXA diagnostic information. Seventy-one DXA scans were reanalyzed to obtain TBS results from patients (mean age: 36.3 years). Differences in laboratory, anthropometric values and concomitant DXA measurements in relation to TBS results are reported. For the cohort, mean body mass index (BMI) was 13.6 kg/m2 (SD: 2.1). The vast majority of patients had normal TBS with a mean of 1.395 (SD: 0.08) but, most patients (69%) had abnormal average DXA BMD Z-scores of -2.2 (SD: 1.2). The patients who also demonstrated degraded bone quality on TBS had significantly lower percent ideal body weight and elevated alkaline phosphatase compared to patients with normal TBS (p's < .05). Low BMD treatment decisions in AN may be optimized by considering both DXA and TBS results.

A multi-center trial of exercise and testosterone therapy in women after hip fracture: Design, methods and impact of the COVID-19 pandemic

BackgroundUp to 75% of hip fracture patients never recover to their pre-fracture functional status. Supervised exercise that includes strength training can improve functional recovery after hip fracture. The role of testosterone replacement for augmenting the effects of exercise in older women after hip fracture is unknown. MethodsThe Starting Testosterone and Exercise after Hip Injury (STEP-HI) Study is a 6-month Phase 3 multicenter randomized placebo-controlled trial designed to compare supervised exercise (EX) plus 1% testosterone topical gel, with EX plus placebo gel, and with enhanced usual care (EUC). Female hip fracture patients age ≥ 65 years are being recruited from clinical centers across the United States. Participants are community dwelling and enrolled within 24 weeks after surgical repair of the fracture. The EX intervention is a center-based program of progressive resistance training. The EUC group receives a home exercise program and health education. Participants receive dietary counseling, calcium and vitamin D. The primary outcome is the Six Minute Walk Distance. Secondary outcomes include physical performance measures, self-reported function and quality of life, and dual energy x-ray absorptiometry measures of body composition and bone mineral density. ResultsEnrollment, interventions, and follow-up are ongoing. We describe the impact of the coronavirus disease 2019 pandemic on the trial, including modifications made to allow continuation of the interventions and outcome data collection using remote video and audio technology. ConclusionsResults from the STEP-HI study are expected to have important clinical and public health implications for management of the growing population of hip fracture patients.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy.

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

A long-term trajectory of bone mineral density in childhood cancer survivors after discontinuation of treatment: retrospective cohort study.

Childhood cancer survivors (CCS) are at risk of premature bone loss, although published studies are inconsistent. The objective of this study was to evaluate the prevalence and pattern of low bone mineral density (BMD) in short- and long-term CCS, and to determine clinical factors affecting skeleton after anticancer treatment. This retrospective study was conducted in a cohort of 326 children and young adult CCS (147 females) who completed anticancer treatment. BMD was determined by dual-energy X-ray absorptiometry (DXA). Low BMD was defined as a Z-score ≤ - 1.0, and the very low BMD as a Z-score ≤ - 2.0. Additionally, the changes in BMD over time were studied in 123 CCS who had been re-examined by DXA during follow-up. Median age at diagnosis was 7.27 years (range, 4.4-10.6); median time between end of treatment and DXA was 6.12 (range, 4.0-22.0). Low BMD was found in 24% of CCS, while very low BMD was relatively uncommon (8%). Based on multivariate analysis, the following were significantly associated with low BMD at the follow-up: hematopoietic stem cell transplantation (OR 3.13, 95% CI 1.02-9.63), head and neck radiotherapy (OR 2.54, 95% CI 1.32-4.90), and body weight below the standard reference (OR 3.57, 95% CI 1.24-10.23). The time-related trajectory showed an improvement (BMDLS) or stabilization (BMDTB) in Z-scores values. These data based on serial DXA measurements, encompassing a long-lasting observation period, show that CCS may not be at risk of premature bone loss in young adulthood. However, it is unknown how the scenario for skeletal mass is until the CCS will achieve older or postmenopausal age.

Evaluation of SUVlean consistency in FDG and PSMA PET/MR with Dixon-, James-, and Janma-based lean body mass correction

PurposeTo systematically evaluate the consistency of various standardized uptake value (SUV) lean body mass (LBM) normalization methods in a clinical positron emission tomography/magnetic resonance imaging (PET/MR) setting.MethodsSUV of brain, liver, prostate, parotid, blood, and muscle were measured in 90 18F-FDG and 28 18F-PSMA PET/MR scans and corrected for LBM using the James, Janma (short for Janmahasatian), and Dixon approaches. The prospective study was performed from December 2018 to August 2020 at Shanghai East Hospital. Forty dual energy X-ray absorptiometry (DXA) measurements of non-fat mass were used as the reference standard. Agreement between different LBM methods was assessed by linear regression and Bland-Altman statistics. SUV’s dependency on BMI was evaluated by means of linear regression and Pearson correlation.ResultsCompared to DXA, the Dixon approach presented the least bias in LBM/weight% than James and Janma models (bias 0.4±7.3%, − 8.0±9.4%, and − 3.3±8.3% respectively). SUV normalized by body weight (SUVbw) was positively correlated with body mass index (BMI) for both FDG (e.g., liver: r = 0.45, p < 0.001) and PSMA scans (r = 0.20, p = 0.31), while SUV normalized by lean body mass (SUVlean) revealed a decreased dependency on BMI (r = 0.22, 0.08, 0.14, p = 0.04, 0.46, 0.18 for Dixon, James, and Janma models, respectively). The liver SUVbw of obese/overweight patients was significantly larger (p < 0.001) than that of normal patients, whereas the bias was mostly eliminated in SUVlean. One-way ANOVA showed significant difference (p < 0.001) between SUVlean in major organs measured using Dixon method vs James and Janma models.ConclusionSignificant systematic variation was found using different approaches to calculate SUVlean. A consistent correction method should be applied for serial PET/MR scans. The Dixon method provides the most accurate measure of LBM, yielding the least bias of all approaches when compared to DXA.

High prevalence and undertreatment of osteoporosis in elderly patients undergoing total hip arthroplasty

SummaryWe detected a high prevalence of low bone mineral density assessed by DXA in 268 elderly patients with end-stage osteoarthritis scheduled for total hip arthroplasty (18% osteoporosis, 41% osteopenia). Therefore, and due to the identified concomitant undertreatment, routine DXA measurements should be considered in elderly patients prior to surgery.IntroductionBone quality represents a decisive factor for osseointegration, durability, and complications of an implanted prosthesis. Although the risk of osteoporosis increases with age and the assessment of bone mineral density (BMD) prior to total hip arthroplasty (THA) is recommended in elderly patients, a systematic, unbiased analysis of such patients is not available in the literature.MethodsIn this retrospective study, we examined 268 elderly patients (age ≥70 years) who underwent dual-energy X-ray absorptiometry (DXA) within 3 months prior to primary THA. Demographics, medical history, radiographic OA grade, and stem fixation method (i.e., cemented or cementless) were obtained.ResultsIn total, 153 (57%) cemented and 115 (43%) cementless stem fixations during THA were performed. Forty-nine patients (18%) were diagnosed with osteoporosis (T-score ≤−2.5), 110 patients (41%) with osteopenia (T-score ≤−1.0), and 109 patients (41%) with normal BMD (T-score >−1.0). Importantly, 36/49 patients (73%) with osteoporosis were not diagnosed before, resulting in a relevant undertreatment. Female sex and low body mass index (BMI) were the main factors negatively influencing the bone mineral density (BMD).ConclusionsDue to a high incidence of undiagnosed and untreated osteoporosis in elderly patients with potential effects on the success of osseointegration as well as other clinical outcomes, DXA measurements should be included in the clinical routine for these patients prior to THA.

Bone mineral density assessment by DXA in rheumatic patients with end-stage osteoarthritis undergoing total joint arthroplasty

BackgroundPatients with rheumatic diseases have a high risk for joint destruction and secondary osteoarthritis (OA) as well as low bone mineral density (BMD, i.e., osteoporosis). While several factors may lead to low BMD in these patients, the value of BMD measurements in rheumatic patients with end-stage OA scheduled for total joint arthroplasty is unknown.MethodsIn this retrospective cross-sectional study of 50 adults with secondary OA due to rheumatic diseases, we evaluated dual energy X-ray absorptiometry (DXA) measurements of both hips and the spine performed within 3 months prior to arthroplasty (n = 25 total hip arthroplasty, THA; n = 25 total knee arthroplasty, TKA). We analyzed various demographic and disease-specific characteristics and their effect on DXA results by using group comparisons and multivariate linear regression models.ResultsAlthough patients undergoing TKA were younger (63.2 ± 14.2 vs. 71.0 ± 10.8 yr., p = 0.035), osteoporosis was observed more frequently in patients scheduled for TKA than THA (32% vs. 12%). Osteopenia was detected in 13/25 patients (52%) in both the THA and TKA cohort. In the THA cohort, female sex, lower BMI and prednisolone use were associated with lower T-score in the hip. In TKA patients, higher OA grade determined by Kellgren-Lawrence score was associated with lower T-score in the hip of the affected side.ConclusionsOsteoporosis is present in a considerable frequency of rheumatic patients with end-stage OA, and THA and TKA patients show distinct frequencies and risk factors of low BMD. Our findings point to a potential value of DXA regarding preoperative evaluation of bone status.

The potential for dual energy X-ray absorptiometry to predict lamb eating quality

Data were obtained from 120 lambs which were slaughtered, scanned using dual energy X-ray absorptiometry (DEXA) and underwent eating quality assessment. DEXA images were used to determine R values, reflecting atomic mass, to predict carcass lean %. Additionally, bone regions (humerus, lumbar, femur and “all carcass bone”) were isolated from images to determine bone specific R values (DEXA R Mean and SDev). Prediction of overall liking of cuts across the carcass (scored between 0 and 100) using lean % and bone DEXA was variable. Loin grill overall liking demonstrated significant associations with lumbar DEXA R Mean and SDev, decreasing by 8.6 and 7.6 units across the increasing range of these bone DEXA measures. This association is somewhat independent of carcass lean % and intramuscular fat % of the loin. Given the association of DEXA with eating quality, there are potential benefits for the lamb industry with respect to carcass sorting and marketing during routine processing and DEXA scanning.

Measuring body condition of lizards: a comparison between non-invasive dual-energy X-ray absorptiometry, chemical fat extraction and calculated indices

BackgroundCondition indices (CIs) are used in ecological studies as a way of measuring an individual animal’s health and fitness. Noninvasive CIs are estimations of a relative score of fat content or rely on a ratio of body mass compared to some measure of size, usually a linear dimension such as tarsus or snout-vent length. CIs are generally validated invasively by lethal fat extraction as in a seasonal sample of individuals in a population. Many alternatives to lethal fat extraction are costly or time consuming. As an alternative, dual-energy X-ray absorptiometry (DXA) allows for non-destructive analysis of body composition and enables multiple measurements during an animal’s life time. DXA has never been used for ecological studies in a small, free-ranging lizard before, therefore we calibrated this method against a chemical extraction of fat from a sample of 6 geckos (Israeli fan toed gecko Ptyodactylus guttatus) ranging in body mass between 4.2–11.5 g. We then used this calibrated DXA measurements to determine the best linear measurement calculated CI for this species. ResultsWe found that fat mass measured with DXA was significantly correlated with the mass of chemically extracted fat for specimens more than 4.8 g (N = 5, R2 = 0.995, P < 0.001). Fat percentage regressed with body mass significantly predicted the DXA fat percentage (N = 29, R2adj. = 0.862, p < 0.001). Live wet mass was significantly correlated with predicted fat mass (N = 30, R2 = 0.984, P < 0.001) for specimens more than 4.8 g. Among the five calculated non-invasive CIs that we tested, the best was mass/SVL.ConclusionsWe recommend that in situations where DXA cannot be used, that the most accurate of the body condition estimators for this species is mass/SVL (snout-vent length) for both sexes.

Classifying Abdominal Fat Distribution Patterns by Using Body Measurement Data

This study aims to explore new categorization that characterizes the distribution clusters of visceral and subcutaneous adipose tissues (VAT and SAT) measured by magnetic resonance imaging (MRI), to analyze the relationship between the VAT-SAT distribution patterns and the novel body shape descriptors (BSDs), and to develop a classifier to predict the fat distribution clusters using the BSDs. In the study, 66 male and 54 female participants were scanned by MRI and a stereovision body imaging (SBI) to measure participants’ abdominal VAT and SAT volumes and the BSDs. A fuzzy c-means algorithm was used to form the inherent grouping clusters of abdominal fat distributions. A support-vector-machine (SVM) classifier, with an embedded feature selection scheme, was employed to determine an optimal subset of the BSDs for predicting internal fat distributions. A five-fold cross-validation procedure was used to prevent over-fitting in the classification. The classification results of the BSDs were compared with those of the traditional anthropometric measurements and the Dual Energy X-Ray Absorptiometry (DXA) measurements. Four clusters were identified for abdominal fat distributions: (1) low VAT and SAT, (2) elevated VAT and SAT, (3) higher SAT, and (4) higher VAT. The cross-validation accuracies of the traditional anthropometric, DXA and BSD measurements were 85.0%, 87.5% and 90%, respectively. Compared to the traditional anthropometric and DXA measurements, the BSDs appeared to be effective and efficient in predicting abdominal fat distributions.

Effect of HIV Infection on Growth and Bone Density in Peripubertal Children in the Era of Antiretroviral Therapy: A Cross-Sectional Study in Zimbabwe

Background: Poor linear growth and pubertal delay, both common in children with HIV (CWH) in sub-Saharan Africa, may affect adolescent bone accrual and future fragility fracture risk. We investigated the association of HIV with size-adjusted bone density in peri-pubertal children in Zimbabwe. Methods: CWH aged 8-16 years taking ART for ≥2 years from public-sector HIV clinics in Harare, and HIV-uninfected children from schools in the same catchment area, were recruited into a cross-sectional study. Sociodemographic, clinical and anthropometric data were collected. Outcomes were dual-energy X-ray absorptiometry (DXA) measured total-body less-head bone mineral content-for-lean mass adjusted for height (TBLH-BMCLBM) and lumbar spine bone mineral apparent density (LS-BMAD). Linear regression models using multiple imputation for missing data, assessed relationships between risk factors and DXA measures by HIV status, and interaction by sex and pubertal (Tanner) stage. Findings: We recruited 303 CWH and 306 without HIV, mean (SD) age 12.5 (2.5) years and 50% female. Mean ART duration was 7.9 (2.6) years; for 34% ART included tenofovir disproxil fumarate (TDF). The prevalence of low TBLH-BMCLBM and LS-BMAD (Z-Score<-2) was higher in children with than without HIV (10.4% vs. 6.2%, p=0.066; 14.3% vs. 5.8%, p=0.001 respectively). HIV and male sex were associated with earlier Tanner stage. The negative effects of HIV on TBLH-BMCLBM and LS-BMAD were more pronounced with pubertal maturation, particularly in females. Among CWH, years of TDF exposure and orphanhood were strongly associated with lower TBLH-BMCLBM Z-Score in both unadjusted and adjusted analyses. Current TDF use was associated with 0.40 (95%CI 0.07, 0.73; p=0.018) and 0.31 (0.07, 0.69; p=0.110) lower TBLH-BMCLBM and LS-BMAD Z-Scores respectively. Interpretation: Despite ART, HIV is associated with substantial skeletal deficits by the end of puberty. The size of bone deficits associated with TDF and its widespread use in children in sub-Saharan Africa raise concern for future adult fracture risk. Funding Statement: Wellcome Trust. Declaration of Interests: RR (206764/Z/17/Z) RAF (206316/Z/17/Z) are funded by the Wellcome Trust. CK is funded by a National Institute of Health (NIH) Fogarty Trent Fellowship. AMR is partially supported by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement which is also part of the EDCTP2 programme supported by the European Union Grant Ref: MR/R010161/1. All other authors declare no competing interests. Ethics Approval Statement: Ethical and governance approvals were granted by the London School of Hygiene and Tropical Medicine Ethics Committee (Ref: 15333), the Institutional Review Board of the Biomedical Research and Training Institute in Harare (Ref: AP145/2018), the Joint Research Ethics Committee for University of Zimbabwe College of Health Sciences and the Parirenyatwa Group of Hospitals (Ref: 11/18), Harare Central Hospital Ethics Committee (Ref: 170118/04), the Medical Research Council of Zimbabwe (Ref: MRCZ/A/2297) and the Ministry of Primary and Secondary Education Zimbabwe (Ref: C/426/Harare). Guardians provided written informed consent and children provided written assent.

Association of Baseline and Longitudinal Changes in Body Composition Measures With Risk of Heart Failure and Myocardial Infarction in Type 2 Diabetes: Findings From the Look AHEAD Trial.

Intentional weight loss is associated with lower risk of heart failure (HF) and atherosclerotic cardiovascular disease among patients with type 2 diabetes. However, the contribution of baseline measures and longitudinal changes in fat mass (FM), lean mass (LM), and waist circumference (WC) to the risk of HF and myocardial infarction (MI) in type 2 diabetes is not well established. Adults from the Look AHEAD trial (Action for Health in Diabetes) without prevalent HF were included. FM and LM were predicted using validated equations and compared with dual-energy x-ray absorptiometry measurements in a subgroup. Adjusted Cox models were used to evaluate the associations of baseline and longitudinal changes in FM, LM, and WC over 1- and 4-year follow-up with risk of overall HF, HF with preserved ejection fraction (EF; EF ≥50%), HF with reduced EF (EF <50%), and MI. Among 5103 participants, there were 257 incident HF events over 12.4 years of follow-up. Predicted and measured FM/LM were highly correlated (R2=0.87-0.90; n=1369). FM and LM decreased over 4-year follow-up with greater declines in the intensive lifestyle intervention arm. In adjusted analysis, baseline body composition measures were not significantly associated with HF risk. Decline in FM and WC, but not LM, over 1 year were each significantly associated with lower risk of overall HF (adjusted hazard ratio per 10% decrease in FM, 0.80 [95% CI, 0.68-0.95]; adjusted hazard ratio per 10% decrease in WC, 0.77 [95% CI, 0.62-0.95]). Decline in FM was significantly associated with lower risk of both HF subtypes. In contrast, decline in WC was significantly associated with lower risk of HF with preserved EF but not HF with reduced EF. Similar patterns of association were observed for 4-year changes in body composition and HF risk. Longitudinal changes in body composition were not significantly associated with risk of MI. In adults with type 2 diabetes, a lifestyle intervention is associated with significant loss of FM and LM. Declines in FM and WC, but not LM, were each significantly associated with lower risk of HF but not MI. Furthermore, decline in WC was significantly associated with lower risk of HF with preserved EF but not HF with reduced EF. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00017953.

Significant improvement in bone mineral density in pediatric celiac disease: even at six months with gluten-free diet.

Patients with celiac disease had significantly decreased bone mineral density even in patients with no gastrointestinal symptoms. Only few bone studies are available on pediatric patients with celiac disease. Forty-six patients underwent measurement of areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) before the initiation of gluten-free diet. Anthropometric, laboratory and DXA measurements at baseline and at sixth month of the treatment were compared. The frequency of low aBMD Z-score (≤-1SDS) in both or any site was found to be 78.2% in this study. Of 16 patients with an aBMD Z-score of <-2SDS five gained more than 1SDS, and one gained more than 2SDS. Nine of 20 patients with an aBMD Z-score of <-1SDS completely normalized. The results of the study showed that low BMD is common in children with celiac disease at the time of diagnosis and could improve in a short period of six months with a strict gluten-free diet and adequate supplementation of calcium and vitamin D.