Volume estimates by imaging methods: model comparisons with visible woman as the reference

Paired-agent imaging as a rapid en face margin screening method in Mohs micrographic surgery

Background

Mohs micrographic surgery is a procedure used for non-melanoma skin cancers that has 97-99% cure rates largely owing to 100% margin analysis enabled by en face sectioning with real-time, iterative histologic assessment. However, the technique is limited to small and aggressive tumors in high-risk areas because the histopathological preparation and assessment is very time intensive. To address this, paired-agent imaging (PAI) can be used to rapidly screen excised specimens and identify tumor positive margins for guided and more efficient microscopic evaluation.

Methods

A mouse xenograft model of human squamous cell carcinoma (n = 8 mice, 13 tumors) underwent PAI. Targeted (ABY-029, anti-epidermal growth factor receptor (EGFR) affibody molecule) and untargeted (IRDye 680LT carboxylate) imaging agents were simultaneously injected 3-4 h prior to surgical tumor resection. Fluorescence imaging was performed on main, unprocessed excised specimens and en face margins (tissue sections tangential to the deep margin surface). Binding potential (BP) - a quantity proportional to receptor concentration - and targeted fluorescence signal were measured for each, and respective mean and maximum values were analyzed to compare diagnostic ability and contrast. The BP and targeted fluorescence of the main specimen and margin samples were also correlated with EGFR immunohistochemistry (IHC).

Results

PAI consistently outperformed targeted fluorescence alone in terms of diagnostic ability and contrast-to-variance ratio (CVR). Mean and maximum measures of BP resulted in 100% accuracy, while mean and maximum targeted fluorescence signal offered 97% and 98% accuracy, respectively. Moreover, maximum BP had the greatest average CVR for both main specimen and margin samples (average 1.7 ± 0.4 times improvement over other measures). Fresh tissue margin imaging improved similarity with EGFR IHC volume estimates compared to main specimen imaging in line profile analysis; and margin BP specifically had the strongest concordance (average 3.6 ± 2.2 times improvement over other measures).

Conclusions

PAI was able to reliably distinguish tumor from normal tissue in fresh en face margin samples using the single metric of maximum BP. This demonstrated the potential for PAI to act as a highly sensitive screening tool to eliminate the extra time wasted on real-time pathological assessment of low-risk margins.

Changes in abdominal adipose tissue depots assessed by MRI correlate with hepatic histologic improvement in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is prevalent in adults with obesity and can progress to cirrhosis. In a secondary analysis of prospectively acquired data from the multicenter, randomized, placebo-controlled FLINT trial, we investigated the relationship between reduction in adipose tissue compartment volumes and hepatic histologic improvement.

METHODS

Adult participants in the FLINT trial with paired liver biopsies and abdominal MRI exams at baseline and end-of-treatment (72 weeks) were included (n = 76). Adipose tissue compartment volumes were obtained using MRI.

RESULTS

Treatment and placebo groups did not differ in baseline adipose tissue volumes, or in change in adipose tissue volumes longitudinally (p = 0.107 to 0.745). Deep subcutaneous adipose tissue (dSAT) and visceral adipose tissue volume reductions were associated with histologic improvement in NASH (i.e., NAS [non-alcoholic fatty liver disease activity score] reductions of ≥2 points, at least 1 point from lobular inflammation and hepatocellular ballooning, and no worsening of fibrosis) (p = 0.031, and 0.030, respectively). In a stepwise logistic regression procedure, which included demographics, treatment group, baseline histology, baseline and changes in adipose tissue volumes, MRI hepatic proton density fat fraction (PDFF), and serum aminotransferases as potential predictors, reductions in dSAT and PDFF were associated with histologic improvement in NASH (regression coefficient = -2.001 and -0.083, p = 0.044 and 0.033, respectively).

CONCLUSIONS

In adults with NASH in the FLINT trial, those with greater longitudinal reductions in dSAT and potentially visceral adipose tissue volumes showed greater hepatic histologic improvements, independent of reductions in hepatic PDFF.

CLINICAL TRIAL NUMBER

NCT01265498.

IMPACT AND IMPLICATIONS

Although central obesity has been identified as a risk factor for obesity-related disorders including insulin resistance and cardiovascular disease, the role of central obesity in non-alcoholic steatohepatitis (NASH) warrants further clarification. Our results highlight that a reduction in central obesity, specifically deep subcutaneous adipose tissue and visceral adipose tissue, may be related to histologic improvement in NASH. The findings from this analysis should increase awareness of the importance of lifestyle intervention in NASH for clinical researchers and clinicians. Future studies and clinical practice may design interventions that assess the reduction of deep subcutaneous adipose tissue and visceral adipose tissue as outcome measures, rather than simply weight reduction.

Estimation of Spleen Volume Using MRI Segmentation: Would One Slice Be Enough?

This study aimed to establish spleen volume in adult Sudanese using manual segmentation and the Cavalieri method with magnetic resonance images (MRI). A total of 345 abdominal MRI scans for adults were retrospectively studied for patients who underwent abdomen MRI between September to October 2016. The data were collected from two scanning centers in Khartoum, Sudan. For each series of sectional images, the spleen was manually segmented, and the volume was calculated using matrix laboratory (MATLAB) code. Furthermore, abdominal circumferences and diameters, in addition to L1 body dimension and spinal canal, were measured.  The mean splenic volume in our study was 187.2 cm³, without a significant change with age (P = 0.269). The average volume in males was 223.5 cm³ while in females it was 170.27 cm³. The average coefficient error (CE) was 0.029. A positive significant correlation was found between the volume and spleen length (beta standardized coefficient = 0.781, P < 0.05). The mean length was 9.18 cm. Additionally, our data showed an insignificant correlation between the volume and the other measurements, except for the abdomen transverse diameter (beta standardized coefficient = 0.267, P < 0.05).  The results of our study coincided with previous studies in the normal range of spleen volume and the strong correlation with length, regardless of the irregular shape of the spleen. In addition, manual segmentation was a reliable method to measure spleen volume objectively. However, our single-slice measurements were insufficient.

Identifying metabolic syndrome in migrant Asian Indian adults with anthropometric and visceral fat action points

BACKGROUND

Metabolic syndrome (MetS) is a clustering of metabolic risk factors, including large waist circumference (WC). Other anthropometric parameters and visceral fat mass (VFM) predicted from these may improve MetS detection. Our aim was to assess the ability of such parameters to predict this clustering in a cross-sectional, diagnostic study.

METHOD

Participants were 82 males and 86 females, aged 20-74 years, of Asian Indian ethnicity. VFM was estimated by dual-energy X-ray absorptiometry (DXA) through identification of abdominal subcutaneous fat layer boundaries. Non-anthropometric metabolic risk factors (triglycerides, HDL cholesterol, blood pressure and glucose) were defined using MetS criteria. We estimated the ability of anthropometry and VFM to detect ≥ 2 of these factors by receiver operating characteristic (ROC) and precision-recall curves.

RESULTS

Two or more non-anthropometric metabolic risk factors were present in 45 (55%) males and 29 (34%) females. The area under the ROC curve (AUC) to predict ≥ 2 of these factors using WC was 0.67 (95% confidence interval: 0.55-0.79) in males and 0.65 (0.53-0.77) in females. Optimal WC cut-points were 92 cm for males (63% accuracy) and 79 cm for females (53% accuracy). VFM, DXA-measured sagittal diameter and suprailiac skinfold thickness yielded higher AUC point estimates (by up to 0.06), especially in females where these measures improved accuracy to 69%, 69% and 65%, respectively. Pairwise combinations that included WC further improved accuracy.

CONCLUSION

Our findings indicate that cut-points for readily obtained measures other than WC, or in combination with WC, may provide improved detection of MetS risk factor clusters.

The Impact of Slice Interval and Equation on the Accuracy of Magnetic Resonance Image Estimation of Quadriceps Muscle Volume in End Stage Liver Disease

Introduction

End stage liver disease (ESLD) is associated with loss of muscle mass and function, known as sarcopenia, which can increase the risk of complications of ESLD, hospitalization and mortality. Therefore, the accurate assessment of muscle mass is essential to evaluate sarcopenia in ESLD. However, manual segmentation of muscle volume (MV) can be laborious on cross-sectional imaging, due to the number of slices that require analysis. This study aimed to investigate the impact of reducing the number of slices required for MV estimation. Further, we aimed to compare two equations utilized in estimating MV (cylindrical and truncated cone).

Methods

Thirty eight ESLD patients (23 males; 54.8 ± 10.7 years) were recruited from the Queen Elizabeth University Hospital Birmingham. A 3T MRI scan was completed of the lower limbs. Quadriceps MV was estimated utilizing 1-, 2-, 3-, and 4 cm slice intervals with both cylindrical and truncated cone equations. Absolute and relative error (compared to 1 cm slice interval) was generated for 2-, 3-, and 4 cm slice intervals. L3 skeletal muscle index (SMI) was also calculated in 30 patients.

Results

Relative error increased with slice interval using the cylindrical (0.45 vs. 1.06 vs. 1.72%) and truncated cone equation (0.27 vs. 0.58 vs. 0.74%) for 2, 3, and 4 cm, respectively. Significantly, the cylindrical equation produced approximately twice the error compared to truncated cone, with 3 cm (0.58 vs. 1.06%, P < 0.01) and 4 cm intervals (0.74 vs. 1.72%, P < 0.001). Finally, quadriceps MV was significantly correlated to L3 SMI (r² = 0.44, P < 0.0001).

Conclusion

The use of the truncated equation with a 4 cm slice interval on MRI offers an efficient but accurate estimation of quadricep muscle volume in ESLD patients.

Evaluation of aging changes of the superficial fat compartments of the midface over time: A computed tomography study

BACKGROUND

Previous studies on alterations in superficial fat compartments with age yielded contradictory results; the superficial fat tissue volume or thickness was reported to increase, decrease, or remain unchanged.

AIMS

To investigate volumetric and dimensional changes in superficial midfacial fat tissue retrospectively in patients who underwent a repeated computed tomography (CT).

METHODS

A total of 262 patients (mean age, 46 years; median elapsed time between two CT imagings, 56 months) were included. Axial and sagittal planes were used for measurements of the medial part of the superficial cheek fat (SCF), which is divided into three compartments. The thickness, width, and height of each compartment were measured, and volumes were calculated for both hemifaces. Additionally, results were compared between males and females, and between three age groups: <45, 45-54, and ≥55 years.

RESULTS

The total volume of SCF and inferior compartment was significantly increased compared with the first CT findings (p < 0.05). Upper and middle compartment volumes were found to decrease with age (p < 0.05). Thickness was decreased in the upper and middle compartments but not in the lower compartment. The width of the lower and middle compartments increased (p < 0.05), while the upper compartment did not show a significant change with age (p > 0.05). The height of the superficial fat layer was significantly increased at follow-up (p < 0.05). The results were similar for both sexes and all age groups (p > 0.05).

CONCLUSIONS

SCF undergoes significant volume and dimensional changes with aging. Therefore, superficial fat tissue should be considered for enhancement of cosmetic treatments.

Aging Changes of the Superficial Fat Compartments of the Midface Over Time: A Magnetic Resonance Imaging Study

BACKGROUND

Studies involving superficial facial fat compartments are few in number with conflicting results. Most of them involved small study groups and compared measurements between different populations of young and old subjects either on cadavers or living subjects.

OBJECTIVE

To clarify volumetric and dimensional changes in midfacial superficial fat compartment retrospectively in patients who underwent a repeat magnetic resonance imaging (MRI) without gross pathology.

MATERIALS AND METHODS

A total of 70 patients with a mean age of 60 years (range: 33-82 years) and a median elapsed time of 44.5 months (range: 32-64 months) between 2 MRIs were included. Magnetic resonance imaging scans were analyzed in the axial and sagittal planes to obtain measurements of the medial part of the superficial cheek fat. Superficial cheek fat was divided into 3 compartments. Thickness, width, and height were measured, and volumes were calculated for each compartment on both hemifaces.

RESULTS

Volume and thickness were decreased significantly in all compartments (p < .05). The width was decreased in superior and middle compartments, whereas increased in lower compartment indicating dislocation of the fat tissue (p < .05). Height was also significantly increased (p < .05). A subgroup analysis has shown that there was no significant difference between men and women.

CONCLUSION

This study clarifies that aging is associated with a significant decrease in superficial midfacial fat tissue volume and thickness both in women and men. The decrease in width in upper and middle compartments, but increase in lower compartment suggests a volume shift within superficial fat tissue.

Imaging Software-Based Sarcopenia Assessment in Gastroenterology: Evolution and Clinical Meaning

Sarcopenia is gaining attention as a negative prognostic factor in different fields of medicine, including chronic liver failure. However, the assessment of sarcopenia in patients with liver diseases is often neglected due to unawareness of reliable tools and methods and thus is limited to research studies. Cross-sectional imaging is a diffuse diagnostic tool and is commonly performed in patients with chronic liver failure. The last advancements in radiology image analysis using dedicated software allow an easy and standardized method to assess skeletal muscle volume. Several measures can be obtained from cross-sectional imaging analysis to evaluate sarcopenia in patients affected by chronic liver disease. We aimed to review the recent advances in imaging-based sarcopenia assessment, in particular in patients with chronic liver diseases. As a result, we found that the skeletal muscle index (SMI) seems to be a reliable method to assess sarcopenia in cirrhotic patients. Even if further studies are needed to validate proper cut-offs for each clinical endpoint, physicians are invited to consider the assessment of sarcopenia in the work-up of patients with chronic liver disease.

Estimation of skeletal muscle mass by bioimpedance and differences among skeletal muscle mass indices for assessing sarcopenia

BACKGROUND

It is crucial to assess age-related muscle mass changes and derived indices differences in geriatric medicine. We aimed to develop and validate four bioimpedance analysis (BIA) prediction equations against dual-energy X-ray absorptiometry (DEXA) and magnetic resonance image (MRI) in estimating skeletal muscle mass and to compare the differences among skeletal muscle mass indices, cutoff values, and corresponding prevalence rates of low muscle mass for assessing sarcopenia in Chinese adults.

METHODS

We measured the height (Ht), weight (Wt), appendicular lean mass (ALM) or skeletal muscle mass (ASM), total lean body mass (LBM) or skeletal muscle mass (TSM) obtained using DEXA or MRI, and a multi-frequency BIA (BCA _II;50, 250 kHz), in 371 adults aged 18.0-87.0 years. We also collected gender, age, Ht, Wt, and impedance indexes (Ht²/R₅₀, Ht²/R₂₅₀, R₅₀/Ht², R₂₅₀/Ht²) from 30,500 adults aged 18-96 years living in China. Multiple regression analyses were used to derive four prediction equations by BIA, and double cross-validation techniques and Bland-Altman analyses were used to test agreement. Various muscle mass indices and prevalence rates were depicted by line plots in regard to age trends.

RESULTS

Satisfactory results were found in the four prediction models as they had the larger R² (0.833-0.930) values and low SEE (1.409-2.335 kg) values. The predictive variables included impedance indexes (Ht²/R₅₀, R₅₀/Ht², R₂₅₀/Ht²), gender, age, Wt, and Ht. The corresponding prevalence rates of low muscle mass exhibited significant differences according to the various muscle mass indices adjusted for Ht, Wt, or body mass index (BMI), in addition to the cutoff values based on two standard deviations (2SD) of young people or the lower 20% of the study group.

CONCLUSIONS

The BIA equations have the potential to be applied as a practical method of quantifying skeletal muscle mass in Chinese adults. However, the operational methods that are most appropriate for determining the degree of low muscle mass that actually contributes to sarcopenia remains inconclusive.

Bipolar ablation with contact force-sensing of swine ventricles shows improved acute lesion features compared to sequential unipolar ablation

INTRODUCTION

Despite technical progress, ventricular tachycardia (VT) recurrence after unipolar ablation remains relatively high (12%-47%). Bipolar ablation has been proposed as an appealing solution that may overcome limitations associated with unipolar ablation settings. We designed an animal study to compare bipolar (BPA) vs sequential unipolar ablation (UPA) using contact force-sensing technology on both ablation catheters.

METHODS

Twenty large white female pigs (6-months-old, 50-60 kg) underwent multiple RF ablations (30 W, 60 seconds, 30 mL/min irrigation) on the ventricular myocardium from the epicardial and endocardial sides. The hearts were fixed and scanned with high-resolution cardiac magnetic resonance imaging. Thermal lesions were located and characterized in volume, depth, width, and transmurality.

RESULTS

Lesion volume was calculated as the sum of epicardial or endocardial conjoined/isolated lesions at one location. Linear dimensions (width and depth) were measured twice for each location, on the endocardial and epicardial side. We evaluated 35 lesions across the intraventricular septum (UPA, N = 17 vs BPA, N = 18). No difference in volume, linear dimensions or impedance drop was observed in this area between UPA and BPA. However, BPA required half RF time and showed an increased transmurality trend. We then analyzed 73 lesions from the endocardial side (UPA, N = 35 vs BPA, N = 38) and 50 from the epicardial side (UPA, N = 11 vs BPA N = 39) of the ventricular free walls. Lesion transmurality was markedly improved by BPA (P = .030, odds ratio, 23.73 [4.71,31.96]). Ventricular BPA lesions were significantly deeper on the epicardial side (P < .0001) and endocardial side (P = .015).

CONCLUSION

Bipolar ablation is more likely to create transmural and epicardial lesions in the ventricle wall. Half the time is needed for the creation of comparably deep and large lesions.

Volumetric Estimation of the Damaged Area in the Human Brain from 2D MR Image

In this article, we present a volumetric estimate of the mutilated part in the human brain from a typical 2D MR image that is directly rendered from the scanner, which is first of its kind in the field of medical imaging. The proposed concept necessitates segmentation of the MR image for the identification of dimensions in the damaged region. Once the dimensions are identified from the resultant segmented image, the volume of the damaged region is evaluated through the Gauss Derivation theorem. The pixel to the distance scaling, which is fed as an input for the Gauss Derivation is from an earlier medical diagnosis from another researcher. The proposed algorithm was experimented with real-time images and the obtained results were examined against the real-time scenarios and were observed to exhibit better accuracy.

Magnetic Resonance Imaging for Characterization of a Chick Embryo Model of Cancer Cell Metastases

Metastasis is the most common cause of death for patients with cancer. To fully understand the steps involved in metastatic dissemination, in vivo models are required, of which murine ones are the most common. Therefore, preclinical imaging methods such as magnetic resonance imaging (MRI) have mainly been developed for small mammals and their potential to monitor cancer growth and metastasis in nonmammalian models is not fully harnessed. We have here used MRI to measure primary neuroblastoma tumor size and metastasis in a chick embryo model. We compared its sensitivity and accuracy to end-point fluorescence detection upon dissection. Human neuroblastoma cells labeled with green fluorescent protein (GFP) and micron-sized iron particles were implanted on the extraembryonic chorioallantoic membrane of the chick at E7. T₂ RARE, T₂-weighted fast low angle shot (FLASH) as well as time-of-flight MR angiography imaging were applied at E14. Micron-sized iron particle labeling of neuroblastoma cells allowed in ovo observation of the primary tumor and tumor volume measurement noninvasively. Moreover, T₂ weighted and FLASH imaging permitted the detection of small metastatic deposits in the chick embryo, thereby reinforcing the potential of this convenient, 3R compliant, in vivo model for cancer research.

Muscle Atrophy Measurement as Assessment Method for Low Back Pain Patients

Low back pain is one of the most common pain disorders defined as pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, sometimes with accompanying leg pain. The meaning of the symptomatic atrophy of paraspinal muscles and some pelvic muscles has been proved. Nowadays, a need for new diagnostic tools for specific examination of low back pain patients is posited, and it has been proposed that magnetic resonance imaging assessment toward muscle atrophy may provide some additional information enabling the subclassification of that group of patients.

High-Resolution Magnetic Resonance Imaging of Aging Upper Face Fat Compartments

BACKGROUND

Age-related changes in fat compartments have yet to be fully characterized. Uncertainty remains in terms of volume gains/losses or shape fluctuations over time. The authors' aim was to determine the evolution of subcutaneous fat in the aging upper face, focusing on shifts in volume and dimension.

METHODS

Over the course of 4.5 years, 100 faces of living female Caucasian patients were prospectively studied using high-resolution magnetic resonance imaging. Subjects were stratified by age as follows: group 1, 18 to 30 years; group 2, 30 to 60 years; and group 3, older than 60 years. Superficial temporal and central forehead compartments were delimited, analyzing respective volumes and dimensions by group.

RESULTS

In 85 patients studied, superficial temporal fat (mean volume, 5.14 cm) increased 35.48 percent in total volume between youth and old age (p = 0.046). Overall height and magnitude of the lower one-third also increased with aging. Central forehead fat (mean volume, 2.56 cm), studied in 83 patients, showed a 209.75 percent volume gain in group 2 (versus group 1) and a 17.59 percent volume loss in group 3 (versus group 2) (p = 0.001).

CONCLUSION

Subcutaneous facial fat fluctuates with aging, increasing in the upper face and promoting ptosis through basal compartmental expansion.

Architectural differences in the anterior and middle compartments of the pelvic floor of young-adult and postmenopausal females

The pelvic floor guards the passage of the pelvic organs to the exterior. The near-epidemic prevalence of incontinence in women continues to generate interest in the functional anatomy of the pelvic floor. However, due to its complex architecture and poor accessibility, the classical 'dissectional' approach has been unable to come up with a satisfactory description, so that many aspects of its anatomy continue to raise debate. For this reason, we opted for a 'sectional' approach, using the Chinese Visible Human project (four females, 21-35 years) and the Visible Human Project (USA; one female, 59 years) datasets to investigate age-related changes in the architecture of the anterior and middle compartments of the pelvic floor. The puborectal component of the levator ani muscle defined the levator hiatus boundary. The urethral sphincter complex consisted of a circular proximal portion (urethral sphincter proper), a sling that passed on the vaginal wall laterally to attach to the puborectal muscle (urethral compressor), and a circular portion that surrounded the distal urethra and vagina (urethrovaginal sphincter). The exclusive attachment of the urethral sphincter to soft tissues implies dependence on pelvic-floor integrity for optimal function. The vagina was circular at the introitus and gradually flattened between bladder and rectum. Well-developed fibrous tissue connected the inferior vaginal wall with urethra, rectum and pelvic floor. With eight-muscle insertions, the perineal body was a strong, irregular fibrous node that guarded the levator hiatus. Only loose areolar tissue comprising a remarkably well developed venous plexus connecting the middle and superior parts of the vagina with the lateral pelvic wall. The posterolateral boundary of the putative cardinal and sacrouterine ligaments coincided with the adventitia surrounding the mesorectum. The major difference between the young-adult and postmenopausal pelvic floor was the expansion of fat in between the components of the pelvic floor. We hypothesize that accumulation of pelvic fat compromises pelvic-floor cohesion, because the pre-pubertal pelvis contains very little fibrous and adipose tissue, and fat is an excellent lubricant.

Design of a lifestyle intervention to slow menopause-related progression of intra-abdominal adipose tissue in women: The Women in the Southside Health and Fitness (WISHFIT) study

Background

Changes in reproductive hormones during menopause are associated with accumulation of intra-abdominal adipose tissue (IAAT), a subclinical indicator of cardiometabolic disease risk. Independent of reproductive hormones, unhealthy lifestyle contributes to IAAT gain. The Women in the Southside Health and Fitness (WISHFIT) Study aims to develop a lifestyle approach to slowing IAAT accumulation as women begin the menopausal transition.

Methods

The primary aim is to develop and conduct a proof-of-concept test of a multi-component, multi-level behavioral intervention targeting jointly physical activity, diet, and psychological well-being. Participants attend group sessions over 2 years to experiment with healthy living through both experiential and didactic learning, cultivate a health network, and draw on community resources to sustain change. The primary endpoint is 2-year IAAT progression, assessed using computerized tomography. Behavioral targets of treatment and secondary endpoints will be evaluated at 6, 12, 18 and 24 months. Change in social networks and community support will be assessed at 2 years.

Results

WISHFIT recruited 71 pre- and peri-menopausal Caucasian and African American women (mean ± SD age = 47.6 ± 3.4 yrs; BMI = 33.6 ± 7.3 kg/m²; 52% African American). Baseline IAAT was 2104.1 ± 1201.3 cm³. IAAT, physical activity, BMI, and self-reported family income and resilience differed by ethnicity at baseline.

Conclusions

WISHFIT is a multi-component, multi-level intervention aimed at producing a sustained improvement in physical activity, diet, and psychological well-being early in the menopausal transition to slow menopause-related accumulation of IAAT. It provides a model for the process of developing a behavioral treatment to manage a chronic disease.

Derivation and validation of simple anthropometric equations to predict adipose tissue mass and total fat mass with MRI as the reference method

The reference organ-level body composition measurement method is MRI. Practical estimations of total adipose tissue mass (TATM), total adipose tissue fat mass (TATFM) and total body fat are valuable for epidemiology, but validated prediction equations based on MRI are not currently available. We aimed to derive and validate new anthropometric equations to estimate MRI-measured TATM/TATFM/total body fat and compare them with existing prediction equations using older methods. The derivation sample included 416 participants (222 women), aged between 18 and 88 years with BMI between 15·9 and 40·8 (kg/m2). The validation sample included 204 participants (110 women), aged between 18 and 86 years with BMI between 15·7 and 36·4 (kg/m2). Both samples included mixed ethnic/racial groups. All the participants underwent whole-body MRI to quantify TATM (dependent variable) and anthropometry (independent variables). Prediction equations developed using stepwise multiple regression were further investigated for agreement and bias before validation in separate data sets. Simplest equations with optimal R (2) and Bland-Altman plots demonstrated good agreement without bias in the validation analyses: men: TATM (kg)=0·198 weight (kg)+0·478 waist (cm)-0·147 height (cm)-12·8 (validation: R 2 0·79, CV=20 %, standard error of the estimate (SEE)=3·8 kg) and women: TATM (kg)=0·789 weight (kg)+0·0786 age (years)-0·342 height (cm)+24·5 (validation: R (2) 0·84, CV=13 %, SEE=3·0 kg). Published anthropometric prediction equations, based on MRI and computed tomographic scans, correlated strongly with MRI-measured TATM: (R (2) 0·70-0·82). Estimated TATFM correlated well with published prediction equations for total body fat based on underwater weighing (R (2) 0·70-0·80), with mean bias of 2·5-4·9 kg, correctable with log-transformation in most equations. In conclusion, new equations, using simple anthropometric measurements, estimated MRI-measured TATM with correlations and agreements suitable for use in groups and populations across a wide range of fatness.

Best single-slice location to measure visceral adipose tissue on paediatric CT scans and the relationship between anthropometric measurements, gender and VAT volume in children

OBJECTIVE

Visceral adipose tissue (VAT) is a significant risk factor for obesity-related metabolic diseases. This study investigates (1) the best single CT slice location for predicting total abdominal VAT volume in paediatrics and (2) the relationship between waist circumference (WC), sagittal diameter (SD), gender and VAT volume.

METHODS

A random sample of 130 paediatric abdomen CT scans, stratified according to age and gender, was collected. Three readers measured VAT area at each intervertebral level between T12 and S1 using ImageJ analysis (National Institute of Health, Bethesda, MD) software by thresholding -190 to -30 HU and manually segmenting VAT. Single-slice VAT measurements were correlated with total VAT volume to identify the most representative slice. WC and SD were measured at L3-L4 and L4-L5 slices, respectively. Regression analysis was used to evaluate WC, SD and gender as VAT volume predictors.

RESULTS

Interviewer and intraviewer reliability were excellent (intraclass correlation coefficient = 0.99). Although VAT measured at multiple slices correlated strongly with abdominal VAT, only one slice in females at L2-L3 and two slices in males at L1-L2 and L5-S1 were strongly correlated across all age groups. Linear regression analysis showed that WC was strongly correlated with VAT volume (beta = 0.970, p < 0.001).

CONCLUSION

Single-slice VAT measurements are highly reproducible. Measurements performed at L2-L3 in females and L1-L2 or L5-S1 in males were most representative of VAT. WC is indicative of VAT.

ADVANCES IN KNOWLEDGE

VAT should be measured at L2-L3 in female children and at either L1-L2 or L5-S1 in males. WC is a strong indicator of VAT in children.

The association of adiposity with kidney function decline among HIV-infected adults: findings from the Fat Redistribution and Metabolic Changes in HIV Infection (FRAM) study

OBJECTIVES

The aim of the study was to investigate the association of adiposity with longitudinal kidney function change in 544 HIV-infected persons in the Study of Fat Redistribution and Metabolic Change in HIV infection (FRAM) cohort over 5 years of follow-up.

METHODS

The regional distribution of muscle and adipose tissue was quantified by whole-body magnetic resonance imaging (MRI), and total adiponectin and leptin levels were measured in serum. Kidney function was assessed using the estimated glomerular filtration rate from serum cystatin C (eGFRCys), obtained at baseline and follow-up. Rapid kidney function decline was defined as annual loss of eGFRCys ≥ 3 mL/min/1.73 m(2) , and incident chronic kidney disease (CKD) was defined as eGFRCys <60 mL/min/1.73 m(2) . Multivariate regression analysis was adjusted for age, race, gender, glucose, antihypertensive use, serum albumin, baseline and change in HIV viral load.

RESULTS

At baseline, mean age was 43 years, mean eGFRCys was 86 mL/min/1.73 m(2) , and 21% of patients had albuminuria. The mean (± standard deviation) eGFRCys decline was -0.11 ± 4.87 mL/min/1.73 m(2) per year; 23% of participants had rapid kidney function decline, and 10% developed incident CKD. The lowest tertile of visceral adipose tissue and the highest tertile of adiponectin were both marginally associated with annual kidney function decline of -0.5 mL/min/1.73 m(2) each, but these associations were not statistically significant after adjustment. We found no statistically significant associations of MRI-measured regional adiposity or serum adipokines with rapid kidney function decline or incident CKD (all P-values>0.1 in adjusted models).

CONCLUSIONS

Contrary to findings in the general population, adiposity did not have a substantial association with longitudinal change in kidney function among HIV-infected persons.

Skeletal muscle loss is negatively associated with single-pool Kt/V and dialysis duration in hemodialysis patients

We evaluated the skeletal muscle loss in hemodialysis (HD) patients by bioelectrical impedance analysis (BIA) and handgrip strength test. Thirty-four HD patients and 16 healthy subjects (control group) were measured for skeletal muscle mass normalized as the skeletal muscle mass index (SMI), calculated as skeletal muscle mass (kg)/height (m)(2) using a tetrapolar bioelectrical impedance plethysmograph. Handgrip strength test was also performed using a hand dynamometer in both groups. In HD patients, the associations of SMI and handgrip strength with age, sex, HD conditions, and HD parameters such as body mass index (BMI), single-pool Kt/V (spKt/V), normalized protein catabolic rate (nPCR), creatinine generation rate (CGR) and serum albumin level (Alb) were investigated. SMI of HD patients (4.58 ± 0.95 kg/m(2) ) was significantly lower than that of the control group (5.55 ± 0.80 kg/m(2) , P<0.01). The handgrip strength of HD patients (19.9 ± 7.74 kg) was also significantly lower than that of the control group (33.0 ± 8.94 kg, P<0.01). In HD patients, HD duration was associated with both SMI and handgrip strength. Among HD parameters, spKt/V was negatively associated with both SMI and handgrip strength, BMI and Alb were positively associated with SMI, while nPCR and CGR were associated with neither SMI nor handgrip strength. HD duration independently contributed to skeletal muscle loss and the value of spKt/V may be affected by skeletal muscle loss in HD patients.

Quantitative proton MR techniques for measuring fat

Accurate, precise and reliable techniques for the quantification of body and organ fat distributions are important tools in physiology research. They are critically needed in studies of obesity and diseases involving excess fat accumulation. Proton MR methods address this need by providing an array of relaxometry-based (T1, T2) and chemical shift-based approaches. These techniques can generate informative visualizations of regional and whole-body fat distributions, yield measurements of fat volumes within specific body depots and quantify fat accumulation in abdominal organs and muscles. MR methods are commonly used to investigate the role of fat in nutrition and metabolism, to measure the efficacy of short- and long-term dietary and exercise interventions, to study the implications of fat in organ steatosis and muscular dystrophies and to elucidate pathophysiological mechanisms in the context of obesity and its comorbidities. The purpose of this review is to provide a summary of mainstream MR strategies for fat quantification. The article succinctly describes the principles that differentiate water and fat proton signals, summarizes the advantages and limitations of various techniques and offers a few illustrative examples. The article also highlights recent efforts in the MR of brown adipose tissue and concludes by briefly discussing some future research directions.

Exercise training favors increased insulin-stimulated glucose uptake in skeletal muscle in contrast to adipose tissue: a randomized study using FDG PET imaging

Physical exercise increases peripheral insulin sensitivity, but regional differences are poorly elucidated in humans. We investigated the effect of aerobic exercise training on insulin-stimulated glucose uptake in five individual femoral muscle groups and four different adipose tissue regions, using dynamic (femoral region) and static (abdominal region) 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) PET/CT methodology during steady-state insulin infusion (40 mU·m⁻²·min⁻¹). Body composition was measured by dual X-ray absorptiometry and MRI. Sixty-one healthy, sedentary [V(O2max) 36(5) ml·kg⁻¹·min⁻¹; mean(SD)], moderately overweight [BMI 28.1(1.8) kg/m²], young [age: 30(6) yr] men were randomized to sedentary living (CON; n = 17 completers) or moderate (MOD; 300 kcal/day, n = 18) or high (HIGH; 600 kcal/day, n = 18) dose physical exercise for 11 wk. At baseline, insulin-stimulated glucose uptake was highest in femoral skeletal muscle followed by intraperitoneal visceral adipose tissue (VAT), retroperitoneal VAT, abdominal (anterior + posterior) subcutaneous adipose tissue (SAT), and femoral SAT (P < 0.0001 between tissues). Metabolic rate of glucose increased similarly (~30%) in the two exercise groups in femoral skeletal muscle (MOD 24[9, 39] μmol·kg⁻¹·min⁻¹, P = 0.004; HIGH 22[9, 35] μmol·kg⁻¹·min⁻¹, P = 0.003) (mean[95% CI]) and in five individual femoral muscle groups but not in femoral SAT. Standardized uptake value of FDG decreased ~24% in anterior abdominal SAT and ~20% in posterior abdominal SAT compared with CON but not in either intra- or retroperitoneal VAT. Total adipose tissue mass decreased in both exercise groups, and the decrease was distributed equally among subcutaneous and intra-abdominal depots. In conclusion, aerobic exercise training increases insulin-stimulated glucose uptake in skeletal muscle but not in adipose tissue, which demonstrates some interregional differences.

Whole body fat: content and distribution

Obesity and its co-morbidities, including type II diabetes, insulin resistance and cardiovascular diseases, have become one of the biggest health issues of present times. The impact of obesity goes well beyond the individual and is so far-reaching that, if it continues unabated, it will cause havoc with the economies of most countries. In order to be able to fully understand the relationship between increased adiposity (obesity) and its co-morbidity, it has been necessary to develop proper methodology to accurately and reproducibly determine both body fat content and distribution, including ectopic fat depots. Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) have recently emerged as the gold-standard for accomplishing this task. Here, we will review the use of different MRI techniques currently being used to determine body fat content and distribution. We also discuss the pros and cons of MRS to determine ectopic fat depots in liver, muscle, pancreas and heart and compare these to emerging MRI techniques currently being put forward to create ectopic fat maps. Finally, we will discuss how MRI/MRS techniques are helping in changing the perception of what is healthy and what is normal and desirable body-fat content and distribution.

Estimation of total body skeletal muscle mass in Chinese adults: prediction model by dual-energy X-ray absorptiometry

BACKGROUND

There are few reports on total body skeletal muscle mass (SM) in Chinese. The objective of this study is to establish a prediction model of SM for Chinese adults.

METHODOLOGY

Appendicular lean soft tissue (ALST) was measured by dual energy X-ray absorptiometry (DXA) and SM by magnetic resonance image (MRI) in 66 Chinese adults (52 men and 14 women). Images of MRI were segmented into compartments including intermuscular adipose tissue (IMAT) and IMAT-free SM. Regression was used to fit the prediction model SM = c + k × ALST. Age and gender were adjusted in the fitted model. The piece-wise linear function was performed to further explore the effect of age on SM. 'Leave-One-Out Cross Validation' was utilized to evaluate the prediction performance. The significance of observed differences between predicted and actual SM was tested by t test and the level of agreement was assessed by the method of Bland and Altman.

RESULTS

Men had greater ALST and IMAT-free SM than women. ALST was the primary predictor and highly correlated with IMAT-free SM (R(2) = 0.94, SEE = 1.11 kg, P<0.001). Age was an additional predictor (SM prediction model with age adjusted R(2) = 0.95, SEE = 1.05 kg, P<0.001). There was a piece-wise linear relationship between age and IMAT-free SM: IMAT-free SM = 1.21×ALST-0.98, (Age <45 years) and IMAT-free SM = 1.21×ALST-0.98-0.04× (Age-45), (Age ≥45 years). The prediction performance of this age-adjusted model was good due to 'Leave-One-Out Cross Validation'. No significant difference between measured and predicted IMAT-free SM was detected.

CONCLUSION

Previous SM prediction model developed in multi-ethnic groups underestimated SM by 2.3% and 3.4% for Chinese men and women. A new prediction model by DXA has been established to predict SM in Chinese adults.

Ethnic and sex differences in bone marrow adipose tissue and bone mineral density relationship

The relationship between bone marrow adipose tissue and bone mineral density is different between African Americans and Caucasians as well as between men and women. This suggests that the mechanisms that regulate the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

INTRODUCTION

It has long been established that there are ethnic and sex differences in bone mineral density (BMD) and fracture risk. Recent studies suggest that bone marrow adipose tissue (BMAT) may play a role in the pathogenesis of osteoporosis. It is unknown whether ethnic and sex differences exist in the relationship between BMAT and BMD.

METHODS

Pelvic BMAT was evaluated in 455 healthy African American and Caucasian men and women (age 18-88 years) using whole-body T1-weighted magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

A negative correlation was observed between pelvic BMAT and total body BMD or pelvic BMD (r = -0.533, -0.576, respectively; P < 0.001). In multiple regression analyses with BMD as the dependent variable, ethnicity significantly entered the regression models as either an individual term or an interaction with BMAT. Menopausal status significantly entered the regression model with total body BMD as the dependent variable. African Americans had higher total body BMD than Caucasians for the same amount of BMAT, and the ethnic difference for pelvic BMD was greater in those participants with a higher BMAT. Men and premenopausal women had higher total body BMD levels than postmenopausal women for the same amount of BMAT.

CONCLUSIONS

An inverse relationship exists between BMAT and BMD in African American and Caucasian men and women. The observed ethnic and sex differences between BMAT and BMD in the present study suggest the possibility that the mechanisms regulating the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

Genes linked to energy metabolism and immunoregulatory mechanisms are associated with subcutaneous adipose tissue distribution in HIV-infected men

OBJECTIVE

Genetic studies may help explain abnormalities of fat distribution in HIV-infected patients treated with antiretroviral therapy (ARV).

METHODS

Subcutaneous adipose tissue (SAT) volume measured by MRI in the leg, the lower trunk, the upper trunk, and the arm was examined in 192 HIV-infected White men, ARV-treated from the Fat Redistribution and Metabolic Change in HIV infection study. Single-nucleotide polymorphisms were assayed using the Illumina Human CNV370-quad beadchip. Multivariate and univariate genome-wide association analyses of the four SAT depots were implemented in PLINK software adjusted for age and ARV duration. Functional annotation analysis using Ingenuity Systems Pathway Analysis tool was carried out for markers with P lower than 10(-3) near known genes identified by multivariate analysis.

RESULTS

Loci (rs10504906, rs13267998, rs921231) in or near the anion exchanger solute carrier family 26, member 7 isoform a (SLC26A7) were strongly associated with the upper trunk and the arm SAT (9.8×10(-7) ≤P<7.8×10(-6)). Loci (rs193139, rs7523050, rs1761621) in and near a gene-rich region including G-protein-signaling modulator 2 (GPSM2) and syntaxin-binding protein 3 (STXBP3) were significantly associated with the lower body SAT depots (9.9×10(-7) ≤P<9.5×10(-6)). GPSM2 is associated with cell division and cancer whereas STXBP3 is associated with glucose metabolism in adipoctyes. Ingenuity Systems Pathway Analysis identified atherosclerosis, mitochondrial function, and T-cell-mediated apoptosis as processes related to SAT volume in HIV-infected individuals (P<5×10(-3)).

CONCLUSION

Our results are limited by the small sample size and replication is needed; however, this genomic scan uncovered new genes associated with metabolism and inflammatory pathways that may affect SAT volume in ARV-treated HIV-infected patients.

Body composition and cardiovascular risk markers after remission of Cushing's disease: a prospective study using whole-body MRI

CONTEXT

Cushing's Disease (CD) alters fat distribution, muscle mass, adipokine profile, and cardiovascular risk factors. It is not known whether remission entirely reverses these changes.

OBJECTIVES

Our objective was to determine whether the adverse body composition and cardiovascular risk profile in CD change after remission.

DESIGN, SETTING, AND PATIENTS

Fourteen CD patients were studied prospectively: before surgery (active disease) and again postoperatively 6 months after discontinuing oral glucocorticoids (remission). Whole-body magnetic resonance imaging was used to examine lean and fat tissue distributions.

OUTCOME MEASURES

Body composition (skeletal muscle and fat in the visceral, bone marrow, sc, and inter-muscular compartments) and cardiovascular risk factors (serum insulin, glucose, leptin, high-molecular-weight adiponectin, C-reactive protein, and lipid profile) were measured in active CD and remission (mean 20 months after surgery).

RESULTS

Remission decreased visceral, pelvic bone marrow, sc (including trunk and limb sc), and total fat; waist circumference; and weight (P < 0.05). Remission altered fat distribution, resulting in decreased visceral/total fat (P = 0.04) and visceral fat/skeletal muscle ratios (P = 0.006). Remission decreased the absolute muscle mass (P = 0.015). Cardiovascular risk factors changed: insulin resistance, leptin, and total cholesterol decreased (P < 0.05), but adiponectin, C-reactive protein, and other lipid measures did not change.

CONCLUSIONS

CD remission reduced nearly all fat depots and reverted fat to a distribution more consistent with favorable cardiovascular risk but decreased skeletal muscle. Remission improved some but not all cardiovascular risk markers. Remission from CD dramatically improves body composition abnormalities but may still be associated with persistent cardiovascular risk.

Thigh muscle volume measured by magnetic resonance imaging is stable over a 6-month interval in spinal muscular atrophy

Changes in thigh muscle volume over 6 months were assessed using magnetic resonance imaging in 11 subjects aged 6 to 47 years with spinal muscular atrophy (4 type 2 and 7 type 3; 4 ambulatory and 3 nonambulatory). Muscle volume with normal and abnormal signal was measured using blinded, semiautomated analysis of reconstructed data. Volumes at baseline and 6 months were correlated with clinical function at each epoch. There was minimal increase in normal (0.3 ± 1.4 mL/cm) and total (0.1 ± 1.3 mL/cm) muscle. Muscle volume correlated closely with clinical function. Minimal interval change in muscle volume is consistent with the established clinical history of minimal disease progression over intervals shorter than 1 year. Relative constancy of muscle volume estimation and correlation with established functional measures suggest a role for segmental magnetic resonance imaging as a biomarker of treatment effect in future therapeutic trials.

Muscle volume estimation by magnetic resonance imaging in spinal muscular atrophy

Thigh muscle volume was assessed using magnetic resonance imaging in 16 subjects with spinal muscular atrophy. Scans were successful for 14 of 16 subjects (1 type 1, 6 type 2, and 7 type 3) as young as 5.7 years. Muscle volume with normal and abnormal signal was measured using blinded, semiautomated analysis of reconstructed data. Results were compared with segmental lean mass estimated by dual-energy X-ray absorptiometry and correlated with clinical and electrophysiological measures of disease severity. Muscle volume was reduced with abnormal signal quality. Test-retest reliability (r = .99) and correlation with dual-energy X-ray absorptiometry (r = .91) were excellent. Type 2 subjects had lower volume (3.5 ± 1.6 vs 6.3 ± 2.8 mL/cm height; P = .06) and higher percentage of muscle with abnormal signal (68% ± 20% vs 47% ± 27%; P = .14) than type 3. Reproducibility, tolerability, and strong correlation with clinical measures make magnetic resonance imaging a candidate biomarker for clinical research.

Regional adipose tissue measured by MRI over 5 years in HIV-infected and control participants indicates persistence of HIV-associated lipoatrophy

OBJECTIVE

Peripheral fat loss and visceral fat gain have been reported in HIV infection. There are limited data on long-term change in adipose tissue in HIV-infected patients vs. controls. Therefore, we determined change in regional adipose tissue from baseline examination to 5 years later among participants in the study of Fat Redistribution and Metabolic Change in HIV Infection.

METHODS

Regional adipose tissue volume was measured using MRI at both examinations in 477 HIV-infected and 214 control men and women. Lipoatrophy was defined as leg subcutaneous adipose tissue (SAT) below the cutoff point marking the lowest decile (10%) of controls at each examination.

RESULTS

HIV-infected and control participants showed similar adipose tissue gains. In men, all SAT depots and visceral adipose tissue started lower and remained lower on average in HIV-infected vs. controls. In women, leg and arm SAT also started lower and remained lower in HIV-infected vs. controls. Mean leg SAT of HIV-infected men was 67% of control men at baseline and 65% at follow-up; for women 83% and 77%. At baseline, 48% of HIV-infected participants had lipoatrophy; on average those with baseline lipoatrophy gained 0.96L of leg SAT compared with 1.23L gain for controls in the lowest decile (P = 0.16). At follow-up, 53% of HIV-infected participants had lipoatrophy. In multivariable models, discontinuation of stavudine appeared to produce little gain in leg SAT ( approximately 1.1%/year).

CONCLUSION

HIV-infected participants did not substantially recover SAT compared with controls, although both showed average gains. HIV-associated lipoatrophy persisted after 5 years of follow-up.

Between-slice intervals in quantification of adipose tissue and muscle in children

Magnetic Resonance Imaging (MRI) is increasingly being used in children to quantify adipose tissue (AT) and skeletal muscle (SM) in vivo. It is unclear whether the every 5 cm whole body MRI protocol used in adults is appropriate when applied in children. Whole body MRI continuous 1 cm thick slices were acquired in 73, aged 5-17-year-old healthy children. Images were segmented into subcutaneous (SAT), visceral (VAT), intermuscular AT (IMAT), and SM. The percentage difference between volumes measured by the continuous protocol and volumes estimated with protocols of different between-slice intervals (i.e., interval = 2, 3, 4 and 5 cm) was larger with an increase in interval size, depot size, weight and body mass index percentile. For group comparisons, studies will require less than 5.4% more subjects if an every 5 cm protocol is used for equivalent power as the every 1 cm protocol. For individual subject comparisons, interval protocols can be used to reliably distinguish between subjects who differ in SM or SAT volume by 0.14 to 0.64 L (i.e., 1 to 5% of SM or SAT volume) or more, or in VAT or IMAT volume by 0.06 to 0.21 L (i.e., 10 to 30% of VAT or IMAT volume) or more. The every 5 cm image acquisition protocol can be considered as accurate as the contiguous protocol for group comparisons in children, as well as for comparison of SM and SAT among individual children. However, a smaller slice interval protocol would be more accurate for comparison of VAT or IMAT among individual children.

Adipose tissue distribution after weight restoration and weight maintenance in women with anorexia nervosa

BACKGROUND

Body image distortions are a core feature of anorexia nervosa (AN). We, and others, previously reported abnormalities in adipose tissue distribution after acute weight restoration in adult women with AN compared with body mass index-matched healthy control women. Whether these abnormalities persist over time remains unknown.

OBJECTIVES

We aimed to 1) replicate previous findings that showed preferential central accumulation of adipose tissue in recently weight-restored AN women compared with control subjects, 2) describe the change within patients with longer-term (1-y) weight maintenance, and 3) compare adipose tissue distribution after 1-y maintenance with that of control subjects.

DESIGN

Body composition and adipose tissue distribution were assessed by whole-body magnetic resonance imaging in women with AN shortly after weight normalization (n = 30) and again 1 y after hospital discharge (n = 16) and in 8 female control subjects at 2 time points.

RESULTS

With acute weight restoration, AN patients had significantly greater visceral and intermuscular adipose tissue compared with control women [visceral: 0.75 +/- 0.26 compared with 0.51 +/- 0.26 kg in AN patients and controls, respectively (P = 0.02); intermuscular: 0.46 +/- 0.17 compared with 0.29 +/- 0.13 kg in AN patients and controls, respectively (P = 0.01)]. With maintenance of normal weight for approximately 1 y, visceral adipose tissue distribution in AN patients was not different from that in healthy control subjects.

CONCLUSIONS

In adult women with AN, normalization of weight in the short term is associated with a distribution of adipose tissue that is consistent with a central adiposity phenotype. This abnormal distribution appears to normalize within a 1-y period of weight maintenance. This research was registered at clinicaltrials.gov as NCT 00271921 and NCT 00368667.

Comparison of dual-energy X-ray absorptiometry and magnetic resonance imaging-measured adipose tissue depots in HIV-infected and control subjects

BACKGROUND

Studies in persons without HIV infection have compared adipose tissue measured by dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI), but no such study has been conducted in HIV-infected (HIV+) subjects, who have a high prevalence of regional fat loss.

OBJECTIVE

We compared DXA- with MRI-measured trunk, leg, arm, and total fat in HIV+ and control subjects.

DESIGN

A cross-sectional analysis was conducted in 877 HIV+ subjects and 260 control subjects in FRAM (Study of Fat Redistribution and Metabolic Change in HIV Infection), stratified by sex and HIV status.

RESULTS

Univariate associations of DXA with MRI were strongest for total and trunk fat (r > or = 0.92) and slightly weaker for leg (r > or = 0.87) and arm (r > or = 0.71) fat. The average estimated limb fat was substantially greater for DXA than for MRI for HIV+ and control men and women (all P < 0.0001). Less of a difference was observed in trunk fat measured by DXA and MRI, but the difference was still statistically significant (P < 0.0001). Bland-Altman plots showed increasing differences and variability. Greater average limb fat in control and HIV+ subjects (both P < 0.0001) was associated with greater differences between DXA and MRI measurements. Because the control subjects had more limb fat than did the HIV+ subjects, greater amounts of fat were measured by DXA than by MRI when control subjects were compared with HIV+ subjects. More HIV+ subjects had leg fat in the bottom decile of the control subjects by DXA than by MRI (P < 0.0001).

CONCLUSIONS

Although DXA- and MRI-measured adipose tissue depots correlate strongly in HIV+ and control subjects, differences increase as average fat increases, particularly for limb fat. DXA may estimate a higher prevalence of peripheral lipoatrophy than does MRI in HIV+ subjects.

Regional adipose tissue and elevations in serum aminotransferases in HIV-infected individuals

BACKGROUND

The association of fat distribution with alanine aminotransferase (ALT) and aspartate aminotransferase (AST) elevations is not well-defined in HIV-infected individuals. Obesity is associated with hepatic steatosis, and ALT is a marker of steatosis in the general population.

METHODS

Cross-sectional analysis of 1119 HIV-infected and 284 control subjects. Hepatitis C virus (HCV) RNA testing determined HCV infection. Magnetic resonance imaging measured regional adipose tissue volume.

RESULTS

After adjustment for demographic and lifestyle factors, visceral adipose tissue (VAT) was positively associated with ALT in HIV/HCV-coinfected subjects (+9.8%, 95% confidence interval [CI]: 2.8 to 17.6), HIV-monoinfected subjects (+8.0%, 95% CI: 4.2 to 12.1), and controls (+5.9%, 95% CI: 2.0 to 10.1). In contrast, lower trunk subcutaneous adipose tissue (SAT) was negatively associated with ALT in HIV/HCV-coinfected subjects (-14.3%, 95% CI: -24.7 to -4.2) and HIV-monoinfected subjects (-11.9%, 95% CI: -18.4 to -5.3); there was a trend toward an association in controls (-7.1%, 95% CI: -22.7 to 5.9). Estimated associations between regional adipose tissue and AST were small and did not reach statistical significance.

CONCLUSIONS

More VAT and less lower trunk SAT are associated with elevated ALT, which likely reflects the presence of steatosis. There was little association with AST. HCV infection and having more VAT or less lower trunk SAT are independently associated with elevated ALT in HIV infection. Study regarding the association between VAT, trunk SAT, HCV, and progression of steatosis and fibrosis is needed in HIV-infected individuals.

Regional adipose tissue and lipid and lipoprotein levels in HIV-infected women

BACKGROUND

HIV infection and antiretroviral therapy are associated with dyslipidemia, but the association between regional body fat and lipid levels is not well described.

METHODS

Multivariable linear regression analyzed the association between magnetic resonance imaging-measured regional adipose tissue and fasting lipids in 284 HIV-infected and 129 control women.

RESULTS

Among African Americans, HIV-infected women had higher triglyceride (116 vs. 83 mg/dL; P < 0.001), similar high-density lipoprotein (HDL; 52 vs. 50 mg/dL; P = 0.60), and lower low-density lipoprotein (LDL; 99 vs. 118 mg/dL; P = 0.008) levels than controls. Among whites, HIV-infected women had higher triglyceride (141 vs. 78 mg/dL; P < 0.001), lower HDL (46 vs. 57 mg/dL; P < 0.001), and slightly lower LDL (100 vs. 107 mg/dL; P = 0.059) levels than controls. After adjustment for demographic and lifestyle factors, the highest tertile of visceral adipose tissue (VAT) was associated with higher triglyceride (+85%, 95% confidence interval [CI]: 55 to 121) and lower HDL (-9%, 95% CI: -18 to 0) levels in HIV-infected women; the highest tertile of leg subcutaneous adipose tissue (SAT) was associated with lower triglyceride levels in HIV-infected women (-28%, 95% CI: -41 to -11) and controls (-39%, 95% CI: -5 to -18). After further adjustment for adipose tissue, HIV infection remained associated with higher triglyceride (+40%, 95% CI: 21 to 63) and lower LDL (-17%, 95% CI: -26 to -8) levels, whereas HIV infection remained associated with lower HDL levels (-21%, 95% CI: -29 to -12) in whites but not in African Americans (+8%, 95% CI: -2 to 19).

CONCLUSIONS

HIV-infected white women are more likely to have proatherogenic lipid profiles than HIV-infected African American women. Less leg SAT and more VAT are important factors associated with adverse lipid levels. HIV-infected women may be at particular risk for dyslipidemia because of the risk for HIV-associated lipoatrophy.

The associations of regional adipose tissue with lipid and lipoprotein levels in HIV-infected men

BACKGROUND

HIV infection and antiretroviral therapy are associated with dyslipidemia, but the association between regional adipose tissue depots and lipid levels is not defined.

METHODS

The association of magnetic resonance imaging-measured visceral adipose tissue (VAT) and regional subcutaneous adipose tissue (SAT) volume with fasting lipid parameters was analyzed by multivariable linear regression in 737 HIV-infected and 145 control men from the study of Fat Redistribution and Metabolic Change in HIV Infection.

RESULTS

HIV-infected men had higher median triglycerides (170 mg/dL vs. 107 mg/dL; P < 0.0001), lower high-density lipoprotein cholesterol (HDL-C; 38 mg/dL vs. 46 mg/dL; P < 0.0001), and lower low-density lipoprotein cholesterol (LDL-C; 105 mg/dL vs. 125 mg/dL; P < 0.0001) than controls. After adjustment, greater VAT was associated with higher triglycerides and lower HDL-C in HIV-infected and control men, whereas greater leg SAT was associated with lower triglycerides in HIV-infected men with a similar trend in controls. More upper trunk SAT was associated with higher LDL-C and lower HDL-C in controls, whereas more lower trunk SAT was associated with higher triglycerides in controls. After adjustment, HIV infection remained strongly associated (P < 0.0001) with higher triglycerides (+76%, 95% confidence interval [CI]: 53 to 103), lower LDL-C (-19%, 95% CI: -25 to -12), and lower HDL-C (-18%, 95% CI: -22 to -12).

CONCLUSIONS

HIV-infected men are more likely than controls to have higher triglycerides and lower HDL-C, which promote atherosclerosis, but also lower LDL-C. Less leg SAT and more VAT are important factors associated with high triglycerides and low HDL-C in HIV-infected men. The reduced leg SAT in HIV-infected men with lipoatrophy places them at increased risk for proatherogenic dyslipidemia.

Does insulin resistance, visceral adiposity, or a sex hormone alteration underlie the metabolic syndrome? Studies in women

Insulin resistance, obesity, and a sex hormone alteration have each been suggested as the underlying link for the constellation of risk factors for myocardial infarction (MI) commonly referred to as the metabolic syndrome or the insulin resistance syndrome. In an attempt to identify in women which of these variables is the most likely link, insulin, adiposity variables, sex hormones, and risk factors for MI were measured and their relationships analyzed statistically in 58 premenopausal and 20 postmenopausal healthy women. On controlling for age, visceral adipose tissue (VAT) correlated more strongly with risk factors for MI, insulin, and free testosterone (FT) than did total adipose tissue or subcutaneous adipose tissue. VAT, therefore, was used as the adiposity variable for further data analysis. Waist circumference was a better surrogate of VAT than was waist-hip ratio, which was a poor surrogate of VAT. VAT correlated positively with insulin, FT, triglyceride, and glucose, and negatively with high-density lipoprotein and sex hormone-binding globulin. On controlling for age, FT and insulin correlated with risk factors for MI and with each other, but on controlling for age and VAT, all of their correlations lost statistical significance except for FT-triglyceride and FT-insulin in the postmenopausal women. In conclusion, VAT accumulation in women, independently of other measures of adiposity, may largely explain the correlations of insulin, obesity, and sex hormones with risk factors for MI and may be the immediate underlying factor that links risk factors for MI to form the metabolic syndrome. Insulin resistance, which has been generally accepted to be the underlying factor, may be a component of the syndrome rather than its underlying link. We hypothesize that in women FT may effect preferential VAT accumulation and induce insulin resistance directly, as well as via VAT accumulation, so that a sex hormone alteration may underlie VAT accumulation and thus ultimately underlie the metabolic syndrome (with insulin resistance as a component).

Simple anthropometric measures correlate with metabolic risk indicators as strongly as magnetic resonance imaging-measured adipose tissue depots in both HIV-infected and control subjects

BACKGROUND

Studies in persons without HIV infection have compared percentage body fat (%BF) and waist circumference as markers of risk for the complications of excess adiposity, but only limited study has been conducted in HIV-infected subjects.

OBJECTIVE

We compared anthropometric and magnetic resonance imaging (MRI)-based adiposity measures as correlates of metabolic complications of adiposity in HIV-infected and control subjects.

DESIGN

The study was a cross-sectional analysis of 666 HIV-positive and 242 control subjects in the Fat Redistribution and Metabolic Change in HIV Infection (FRAM) study assessing body mass index (BMI), waist (WC) and hip (HC) circumferences, waist-to-hip ratio (WHR), %BF, and MRI-measured regional adipose tissue. Study outcomes were 3 metabolic risk variables [homeostatic model assessment (HOMA), triglycerides, and HDL cholesterol]. Analyses were stratified by sex and HIV status and adjusted for demographic, lifestyle, and HIV-related factors.

RESULTS

In HIV-infected and control subjects, univariate associations with HOMA, triglycerides, and HDL were strongest for WC, MRI-measured visceral adipose tissue, and WHR; in all cases, differences in correlation between the strongest measures for each outcome were small (r

CONCLUSION

Relations of simple anthropometric measures with HOMA, triglycerides, and HDL cholesterol are approximately as strong as MRI-measured whole-body adipose tissue depots in both HIV-infected and control subjects.

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Key Words Collapse

MESH Headings

• Adipose Tissue/anatomy & histology
• Adult
• Anthropometry/methods
• Body Mass Index
• Body Size
• Cross-Sectional Studies
• Female
• HIV Infections/complications
• HIV Infections/epidemiology
• Humans
• Magnetic Resonance Imaging/methods
• Male
• Middle Aged
• Patient Selection
• Predictive Value of Tests
• Reference Values
• Risk Assessment
• Waist-Hip Ratio

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Grants

• HL74814 NHLBI NIH HHS
• R01 HL074814-06 NHLBI NIH HHS
• R01 DK057508-03S1 NIDDK NIH HHS
• M01 RR000054 NCRR NIH HHS
• RR00052 NCRR NIH HHS
• RR0636 NCRR NIH HHS
• M01 RR000083 NCRR NIH HHS
• RR00054 NCRR NIH HHS
• R01 DK057508-03 NIDDK NIH HHS
• R01 DK057508-01S1 NIDDK NIH HHS
• RR00865 NCRR NIH HHS
• R01-DK57508 NIDDK NIH HHS
• R01 DK057508 NIDDK NIH HHS
• R01 HL074814-07 NHLBI NIH HHS
• R01 DK057508-01 NIDDK NIH HHS
• RR00083 NCRR NIH HHS
• M01 RR000865 NCRR NIH HHS
• M01 RR000036 NCRR NIH HHS
• HL 53359 NHLBI NIH HHS
• R01 HL074814-04 NHLBI NIH HHS
• RR00051 NCRR NIH HHS
• R01 DK057508-03S2 NIDDK NIH HHS
• M01 RR000052 NCRR NIH HHS
• R01 HL074814-05 NHLBI NIH HHS
• M01 RR000051 NCRR NIH HHS
• M01-RR00036 NCRR NIH HHS
• R01 HL074814 NHLBI NIH HHS
• R01 DK057508-02 NIDDK NIH HHS

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Affiliation(s)

Rebecca Scherzer Northern California Institute for Research and Education, San Francisco, CA, USA
Wei Shen
Peter Bacchetti
Donald Kotler
Cora E Lewis
Michael G Shlipak
Steven B Heymsfield
Carl Grunfeld

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Preclinical cancer therapy in a mouse model of neurofibromatosis-1 optic glioma

Mouse models of human cancers afford unique opportunities to evaluate novel therapies in preclinical trials. For this purpose, we analyzed three genetically engineered mouse (GEM) models of low-grade glioma resulting from either inactivation of the neurofibromatosis-1 (Nf1) tumor suppressor gene or constitutive activation of KRas in glial cells. Based on tumor proliferation, location, and penetrance, we selected one of these Nf1 GEM models for preclinical drug evaluation. After detection of an optic glioma by manganese-enhanced magnetic resonance imaging, we randomized mice to either treatment or control groups. We first validated the Nf1 optic glioma model using conventional single-agent chemotherapy (temozolomide) currently used for children with low-grade glioma and showed that treatment resulted in decreased proliferation and increased apoptosis of tumor cells in vivo as well as reduced tumor volume. Because neurofibromin negatively regulates mammalian target of rapamycin (mTOR) signaling, we showed that pharmacologic mTOR inhibition in vivo led to decreased tumor cell proliferation in a dose-dependent fashion associated with a decrease in tumor volume. Interestingly, no additive effect of combined rapamycin and temozolomide treatment was observed. Lastly, to determine the effect of these therapies on the normal brain, we showed that treatments that affect tumor cell proliferation or apoptosis did not have a significant effect on the proliferation of progenitor cells within brain germinal zones. Collectively, these findings suggest that this Nf1 optic glioma model may be a potential preclinical benchmark for identifying novel therapies that have a high likelihood of success in human clinical trials.

Application of imaging and other noninvasive techniques in determining adipose tissue mass

In vivo adipose tissue quantification is an important tool to characterize phenotypes of obesity, especially in the human. The amount and distribution of adipose tissue is associated with many of the adverse consequences of obesity. Recent studies suggest that adipose tissue is not a single homogeneous compartment. Regional adipose tissue depots vary in biological functions and individual adipose tissue compartments have stronger associations with metabolic conditions than does total adipose tissue mass. Currently there is intense and increasing interest in regional adipose tissue compartments. Computed tomography and magnetic resonance imaging often are used to quantify adipose tissue volumes or cross-sectional adipose tissue areas. Other modalities, including dual-energy absorptiometry and magnetic resonance spectroscopy, provide whole-body or regional fat measures instead of adipose tissue mass quantification.

Modeling upper and lower limb muscle volume by bioelectrical impedance analysis

Most studies employing bioelectrical impedance analysis (BIA) for estimating appendicular skeletal muscle mass using descriptive BIA models rely on statistical rather than biophysical principles. The aim of the present study was to evaluate the feasibility of estimating arm and leg muscle volume (MV) based on multiple bioimpedance measurements and using a recently proposed mathematical model and to compare this technique to conventional segmental BIA at high and low frequencies. MV of the arm and leg, respectively, was determined in 15 young, healthy, active men [age 22 ± 2 (SD) yr, total body fat 15.6 ± 5.1%] by magnetic resonance imaging (MRI) and BIA using a conventional and new bioimpedance model. MRI-determined MV for leg and arm was 6,268 ± 1,099 and 1,173 ± 172 cm3, respectively. Estimated MV by the new BIA model [leg: 6,294 ± 1,155 cm3 (50 kHz), 6,278 ± 1,103 cm3 (500 kHz); arm: 1,216 ± 172 cm3 (50 kHz), 1,155 ± 157 cm3 (500 kHz)] was not statistically different from MRI-determined MV (leg: P= 0.958; arm: P= 0.188). The new BIA model was superior to conventional BIA and performed best at 500 kHz for estimating leg MV as indicated by the lower relative total error [new: 3.6% (500 kHz), 5.2% (50 kHz); conventional: 7.6% (500 kHz) and 8.3% (50 kHz)]. In contrast, the new BIA model, both at 50 and 500 kHz, did not improve the accuracy for estimating arm MV [new: 10.8% (500 kHz), 10.6% (50 kHz); conventional: 11.8% (500 kHz), 11.4% (50 kHz)]. It was concluded that modeling of multiple BIA measurements has advantages for the determination of lower limb muscle volume in healthy, active adult men.