Altered White Matter Connectivity in Young Acutely Underweight Patients With Anorexia Nervosa

OBJECTIVE

Reductions of gray matter volume and cortical thickness in anorexia nervosa (AN) are well documented. However, findings regarding the integrity of white matter (WM) as studied via diffusion weighted imaging (DWI) are remarkably heterogeneous, and WM connectivity has been examined only in small samples using a limited number of regions of interest. The present study investigated whole-brain WM connectivity for the first time in a large sample of acutely underweight patients with AN.

METHOD

DWI data from predominantly adolescent patients with acute AN (n = 96, mean age = 16.3 years) and age-matched healthy control participants (n = 96, mean age = 17.2 years) were analyzed. WM connectivity networks were generated from fiber-tractography-derived streamlines connecting 233 cortical/subcortical regions. To identify group differences, network-based statistic was used while taking head motion, WM, and ventricular volume into account.

RESULTS

Patients with AN were characterized by 6 WM subnetworks with abnormal architecture, as indicated by increased fractional anisotropy located primarily in parietal-occipital regions and accompanied by reduced radial diffusivity. Group differences based on number of streamlines reached only nominal significance.

CONCLUSION

Our study reveals pronounced alterations in the WM connectome in young patients with AN. In contrast to known reductions in gray matter in the acutely underweight state of AN, this pattern does not necessarily indicate a deterioration of the WM network. Future studies using advanced MRI sequences will have to clarify interrelations with axonal packing or myelination, and whether the changes should be considered a consequence of undernutrition or a vulnerability for developing or maintaining AN.

Characterization of endogenous bile acid composition in individuals with cold-activated brown adipose tissue

INTRODUCTION

Bile acid signaling has been suggested to promote BAT activity in various experimental models. However, little is known if and how physiologic bile acid metabolism is linked to BAT function in humans. Here we investigated the association between BAT activity and circulating bile acid concentrations in lean and obese individuals.

METHODS

BAT ¹⁸F-fluorodeoxyglucose uptake was measured after a standardized cooling protocol by positron emission tomography/computed tomography. Cold-induced thermogenesis was assessed by indirect calorimetry. Fasting bile acid concentrations were determined by high performance liquid chromatography-high-resolution mass spectrometry.

RESULTS

In a cohort of 24 BAT-negative and 20 BAT-positive individuals matched by age, sex, and body mass index, circulating bile acid levels were similar between groups except for higher ursodeoxycholic acid and a trend towards a lower 12α-OH/non-12α-OH bile acid ratio in lean participants with active BAT compared to those without. Moreover, the 12α-OH/non-12α-OH ratio, a marker of CYP8B1 activity, correlated negatively with BAT volume and activity.

CONCLUSION

Fasting concentrations of major bile acids are not associated with cold-induced BAT activity in humans. However, the inverse association between BAT activity and 12α-OH/non-12α-OH ratio may suggest CYP8B1 as a potential new target in BAT function and warrants additional investigation.

Heterogeneity in insulin-stimulated glucose uptake among different muscle groups in healthy lean people and people with obesity

AIMS/HYPOTHESIS

It has been proposed that muscle fibre type composition and perfusion are key determinants of insulin-stimulated muscle glucose uptake, and alterations in muscle fibre type composition and perfusion contribute to muscle, and consequently whole-body, insulin resistance in people with obesity. The goal of the study was to evaluate the relationships among muscle fibre type composition, perfusion and insulin-stimulated glucose uptake rates in healthy, lean people and people with obesity.

METHODS

We measured insulin-stimulated whole-body glucose disposal and glucose uptake and perfusion rates in five major muscle groups (erector spinae, obliques, rectus abdominis, hamstrings, quadriceps) in 15 healthy lean people and 37 people with obesity by using the hyperinsulinaemic-euglycaemic clamp procedure in conjunction with [²H]glucose tracer infusion (to assess whole-body glucose disposal) and positron emission tomography after injections of [¹⁵O]H₂O (to assess muscle perfusion) and [¹⁸F]fluorodeoxyglucose (to assess muscle glucose uptake). A biopsy from the vastus lateralis was obtained to assess fibre type composition.

RESULTS

We found: (1) a twofold difference in glucose uptake rates among muscles in both the lean and obese groups (rectus abdominis: 67 [51, 78] and 32 [21, 55] μmol kg^-1 min^-1 in the lean and obese groups, respectively; erector spinae: 134 [103, 160] and 66 [24, 129] μmol kg^-1 min^-1, respectively; median [IQR]) that was unrelated to perfusion or fibre type composition (assessed in the vastus only); (2) the impairment in insulin action in the obese compared with the lean group was not different among muscle groups; and (3) insulin-stimulated whole-body glucose disposal expressed per kg fat-free mass was linearly related with muscle glucose uptake rate (r² = 0.65, p < 0.05).

CONCLUSIONS/INTERPRETATION

Obesity-associated insulin resistance is generalised across all major muscles, and is not caused by alterations in muscle fibre type composition or perfusion. In addition, insulin-stimulated whole-body glucose disposal relative to fat-free mass provides a reliable index of muscle glucose uptake rate.

Implications of Abdominal Adipose Tissue Distribution on Nonalcoholic Fatty Liver Disease and Metabolic Syndrome: A Chinese General Population Study

INTRODUCTION

Visceral adipose tissue (VAT) has been found to play a critical role in the development of metabolic syndrome and nonalcoholic fatty liver disease (NAFLD) independent of generalized obesity.

METHODS

In this secondary study of prospectively acquired data, 625 participants underwent magnetic resonance spectroscopy and chemical shift fat-water separation MRI (2-point Dixon) of the liver and whole abdomen, respectively, in a 3 Tesla magnet. Whole abdominal VAT and subcutaneous adipose tissue (SAT) were extracted from the 2-point Dixon image series using an automated method. Clinical/anthropometric/blood biochemistry parameters were measured. Using region-specific body mass index, participants were classified into 3 paired subgroups (lean, overweight, and obese) and presence of NAFLD (liver fat content ≥ 5.5%).

RESULTS

All relevant clinical/anthropometric/blood biochemistry characteristics and liver enzymes were statistically significant between groups (P < 0.001). NAFLD was found in 12.1%, 43.8%, and 68.3% and metabolic syndrome in 51.1%, 61.9%, and 65% of the lean, overweight, and obese, respectively. Odds ratio for metabolic syndrome and NAFLD was increased by 2.73 (95% confidence interval [CI] 2.18-3.40) and 2.53 (95% CI 2.04-3.12), respectively, for 1SD increase in VAT volume while prevalence of metabolic syndrome was increased by 2.26 (95% CI 1.83-2.79) for 1SD increase in liver fat content (%). VAT/SAT ratio in the lean with fatty liver showed the highest ratio (0.54) among all the subgroups, without a significant difference between the lean and obese with NAFLD (P = 0.127).

DISCUSSION

Increased VAT volume/disproportional distribution of VAT/SAT may be vital drivers to the development of metabolic syndrome and NAFLD irrespective of body mass index category.

The influence of obesity on cerebral blood flow in young adults using arterial spin labeling MRI

Obesity causes damage to several organs, including the brain. Recent studies have been focusing on understanding the mechanisms through which obesity affects brain structure and function using neuroimaging techniques. A functional biomarker, such as cerebral blood flow (CBF), is a powerful tool that can be used to explore neural dysfunction. However, there is currently limited information regarding the association between CBF and obesity. The study was conducted to investigate the potential effect of obesity on brain perfusion in a young cohort aged 20-30 years. A total of 21 obese (body mass index (BMI) > 26 kg/m² ) and 21 lean (BMI < 24 kg/m² ) right-handed volunteers were included in this study. CBF was acquired using the 2D single post-labeling delay (PLD) arterial spin labeling (ASL) technique on a 3 T MRI scanner. A multiple regression analysis was performed to examine the difference in global and regional gray matter (GM) CBF between the groups. CBF value was assigned as the dependent variable, whereas age, sex, and group (obese or lean) were considered as the independent variables. Results showed that group-related differences in CBF were homogeneous across brain regions, as obese subjects had significantly lower global GM CBF than lean subjects (P < 0.05). In the voxelwise analysis, obese individuals had significantly lower CBF in the left pulvinar of the thalamus and visual association areas, including Brodmann area (BA) 7, BA18, and BA19, than lean subjects. Although the signal-to-noise ratio was slightly compromised for 2D sequences and subject-specific arterial transit time was not estimated due to a single PLD sequence, this study demonstrated alterations in CBF in obese subjects, particularly in regions of the pulvinar of the thalamus and its synchronously related areas such as visual association areas. These results suggest that ASL provides a potential platform for further obesity-related research.

Relating anthropometric indicators to brain structure in 2-month-old Bangladeshi infants growing up in poverty: A pilot study

Anthropometric indicators, including stunting, underweight, and wasting, have previously been associated with poor neurocognitive outcomes. This link may exist because malnutrition and infection, which are known to affect height and weight, also impact brain structure according to animal models. However, a relationship between anthropometric indicators and brain structural measures has not been tested yet, perhaps because stunting, underweight, and wasting are uncommon in higher-resource settings. Further, with diminished anthropometric growth prevalent in low-resource settings, where biological and psychosocial hazards are most severe, one might expect additional links between measures of poverty, anthropometry, and brain structure. To begin to examine these relationships, we conducted an MRI study in 2-3-month-old infants growing up in the extremely impoverished urban setting of Dhaka, Bangladesh. The sample size was relatively small because the challenges of investigating infant brain structure in a low-resource setting needed to be realized and resolved before introducing a larger cohort. Initially, fifty-four infants underwent T1 sequences using 3T MRI, and resulting structural images were segmented into gray and white matter maps, which were carefully evaluated for accurate tissue labeling by a pediatric neuroradiologist. Gray and white matter volumes from 29 infants (79 ​± ​10 days-of-age; F/M ​= ​12/17), whose segmentations were of relatively high quality, were submitted to semi-partial correlation analyses with stunting, underweight, and wasting, which were measured using height-for-age (HAZ), weight-for-age (WAZ), and weight-for-height (WHZ) scores. Positive semi-partial correlations (after adjusting for chronological age and sex and correcting for multiple comparisons) were observed between white matter volume and HAZ and WAZ; however, WHZ was not correlated with any measure of brain volume. No associations were observed between income-to-needs or maternal education and brain volumetric measures, suggesting that measures of poverty were not associated with total brain tissue volume in this sample. Overall, these results provide the first link between diminished anthropometric growth and white matter volume in infancy. Challenges of conducting a developmental neuroimaging study in a low-resource country are also described.

Lean non-alcoholic fatty liver disease and development of diabetes: a cohort study

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD), a condition associated with multiple metabolic abnormalities, is frequently observed in normal weight individuals (lean NAFLD). The metabolic consequences of lean NAFLD, however, are not well characterized. Thus, this study aimed to evaluate the risk of incident diabetes in lean NAFLD.

METHODS

This is a cohort study of 51,463 adults without diabetes, history of liver disease or cancer at baseline who participated in a regular health screening exam. Fatty liver was diagnosed by ultrasonography. The study outcome was the development of diabetes during follow-up.

RESULTS

During 236,446.6 person-years of follow-up (median follow-up of 4.0 years), 5370 participants developed diabetes. In fully adjusted models, the hazard ratios (HRs) for incident diabetes comparing lean participants with NAFLD, overweight/obese participants without NAFLD and overweight/obese participants with NAFLD to lean participants without NAFLD, were 1.18 (95% CI: 1.03-1.35), 1.06 (0.98-1.14) and 1.45 (1.34-1.57), respectively. The fully adjusted HR for incident diabetes for lean NAFLD participants with low NAFLD fibrosis score (NFS) (<-1.455) and with intermediate-to-high NFS (≥-1.455) compared to lean participants without NAFLD were 1.32 (1.14-1.53) and 2.73 (2.10-3.55), respectively.

CONCLUSIONS

In this large cohort study, the presence and severity of NAFLD in normal weight adults was associated with an increased incidence of diabetes independently of established risk factors. Indeed, isolated lean NAFLD was a stronger risk factor for incident diabetes than the presence of overweight/obesity without NAFLD. Subjects with lean NAFLD require careful monitoring for the development of metabolic abnormalities.

Dynamic changes in white matter microstructure in anorexia nervosa: findings from a longitudinal study

BACKGROUND

Gray matter (GM) 'pseudoatrophy' is well-documented in patients with anorexia nervosa (AN), but changes in white matter (WM) are less well understood. Here we investigated the dynamics of microstructural WM brain changes in AN patients during short-term weight restoration in a combined longitudinal and cross-sectional study design.

METHODS

Diffusion-weighted images were acquired in young AN patients before (acAN-Tp1, n = 56) and after (acAN-Tp2, n = 44) short-term weight restoration as well as in age-matched healthy controls (HC, n = 60). Images were processed using Tract-Based-Spatial-Statistics to compare fractional anisotropy (FA) across groups and timepoints.

RESULTS

In the cross-sectional comparison, FA was significantly reduced in the callosal body in acAN-Tp1 compared with HC, while no differences were found between acAN-Tp2 and HC. In the longitudinal arm, FA increased with weight gain in acAN-Tp2 relative to acAN-Tp1 in large parts of the callosal body and the fornix, while it decreased in the right corticospinal tract.

CONCLUSIONS

Our findings reveal that dynamic, bidirectional changes in WM microstructure in young underweight patients with AN can be reversed with brief weight restoration therapy. These results parallel those previously observed in GM and suggest that alterations in WM in non-chronic AN are also state-dependent and rapidly reversible with successful intervention.

A requiem for BMI in the clinical setting

PURPOSE OF REVIEW

Quetelet reported in the nineteenth century that body weight varies across adults with the square of height. Quetelet's index, now known as BMI, is accepted by most health organizations as a first-level measure of body fat and as a screening tool for diagnosing excess adiposity. Modern imaging methods now, however, indicate that BMI has limited predictive value for estimating body fat and lean mass at the individual level. The use of BMI as a measure of body composition in the clinical setting should therefore be challenged.

RECENT FINDINGS

Recent studies enrolling cancer and surgical patients reported discrepant outcomes when BMI was used as a body composition surrogate. Sarcopenia, loss of muscle mass and function, which affects the elderly and those with chronic and acute diseases, is not accurately diagnosed with BMI. The distribution of adipose tissue is not characterized by BMI, specific measures of which have greater predictive value for metabolic impairments and clinical outcomes.

SUMMARY

BMI, as the traditional tool for assessing malnutrition and obesity, is not appropriate to accurately differentiate between important body weight components and therefore should not be used for making clinically important decisions at the individual patient level.

Factors Associated with Bone Health in Malaysian Middle-Aged and Elderly Women Assessed via Quantitative Ultrasound

Risk factors for osteoporosis may vary according to different populations. We aimed to investigate the relationship between risk factors of osteoporosis and bone health indices determined via calcaneal quantitative ultrasound (QUS) in a group of Malaysian women aged 50 years or above. A cross-sectional study was performed on 344 Malaysian women recruited from a tertiary medical centre in Kuala Lumpur, Malaysia. They answered a self-administered questionnaire on their social-demographic details, medical history, lifestyle, and physical activity status. Their height was measured using a stadiometer, and their body composition estimated using a bioelectrical impedance device. Their bone health status was determined using a water-based calcaneal QUS device that generated three indices, namely speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI). A T-score was computed from SI values using a reference database from a mainland Chinese population. Women with three or more lifetime pregnancies, who were underweight and not drinking coffee had a significantly lower BUA. Stepwise multiple linear regression showed that SOS was predicted by age alone, BUA and SI by years since menopause, body mass index (BMI), and number of lifetime pregnancies, and T-score by years since menopause and percentage of body fat. As a conclusion, suboptimal bone health in middle-aged and elderly Malaysian women as indicated by QUS is associated with old age, being underweight, having a high body fat percentage, and a high number of lifetime pregnancies. Women having several risk factors should be monitored more closely to protect their bones against accelerated bone loss.

Standardized Ultrasound Measurement of Subcutaneous Fat Patterning: High Reliability and Accuracy in Groups Ranging from Lean to Obese

A recently standardized ultrasound technique for measuring subcutaneous adipose tissue (SAT) was applied to normal-weight, overweight and obese persons. Eight measurement sites were used: upper abdomen, lower abdomen, erector spinae, distal triceps, brachioradialis, lateral thigh, front thigh and medial calf. Fat compression was avoided. Fat patterning in 38 participants (body mass index: 18.6-40.3 kgm^-2; SAT thickness sums from eight sites: 12-245 mm) was evaluated using a software specifically designed for semi-automatic multiple thickness measurements in SAT (sound speed: 1450 m/s) that also quantifies embedded fibrous structures. With respect to ultrasound intra-observer results, the correlation coefficient ρ = 0.999 (p < 0.01), standard error of the estimate = 1.1 mm and 95% of measurements were within ±2.2 mm. For the normal-weight subgroup, the median measurement deviation was 0.43 mm (1.1% of mean thickness), and for the obese/overweight subgroup it was 0.89 mm (0.5%). The eight sites used here are suggested to represent inter-individual differences in SAT patterning. High measurement accuracy and reliability can be obtained in all groups, from lean to overweight and obese, provided that measurers are trained appropriately.

Vertebral Volumetric Bone Density and Strength Are Impaired in Women With Low-Weight and Atypical Anorexia Nervosa

CONTEXT

Areal bone mineral density (BMD) is lower, particularly at the spine, in low-weight women with anorexia nervosa (AN). However, little is known about vertebral integral volumetric BMD (Int.vBMD) or vertebral strength across the AN weight spectrum, including "atypical" AN [body mass index (BMI) ≥18.5 kg/m2].

OBJECTIVE

To investigate Int.vBMD and vertebral strength, and their determinants, across the AN weight spectrum.

DESIGN

Cross-sectional observational study.

SETTING

Clinical research center.

PARTICIPANTS

153 women (age 18 to 45): 64 with low-weight AN (BMI <18.5 kg/m2; 58% amenorrheic), 44 with atypical AN (18.5≤BMI<23 kg/m2; 30% amenorrheic), 45 eumenorrheic controls (19.2≤BMI<25 kg/m2).

MEASURES

Int.vBMD and cross-sectional area (CSA) by quantitative computed tomography of L4; estimated vertebral strength (derived from Int.vBMD and CSA).

RESULTS

Int.vBMD and estimated vertebral strength were lowest in low-weight AN, intermediate in atypical AN, and highest in controls. CSA did not differ between groups; thus, vertebral strength (calculated using Int.vBMD and CSA) was driven by Int.vBMD. In AN, Int.vBMD and vertebral strength were associated positively with current BMI and nadir lifetime BMI (independent of current BMI). Int.vBMD and vertebral strength were lower in AN with current amenorrhea and longer lifetime amenorrhea duration. Among amenorrheic AN, Int.vBMD and vertebral strength were associated positively with testosterone.

CONCLUSIONS

Int.vBMD and estimated vertebral strength (driven by Int.vBMD) are impaired across the AN weight spectrum and are associated with low BMI and endocrine dysfunction, both current and previous. Women with atypical AN experience diminished vertebral strength, partially due to prior low-weight and/or amenorrhea. Lack of current low-weight or amenorrhea in atypical AN does not preclude compromise of vertebral strength.

Quantification of visceral fat using dual-energy x-ray absorptiometry and its reliability according to the amount of visceral fat in Korean adults

Recently, a fully automated method for segmenting abdominal fat into subcutaneous fat and visceral fat (VF) within the android region using dual-energy X-ray absorptiometry (DXA) has been newly developed. The purpose of this study was to validate a new DXA method by comparing it to the gold standard, computed tomography (CT), in the Korean population. Furthermore, we examined its reliability regarding VF and explored whether it is applicable to the Asian population, which has relatively larger amount of VF. We studied 123 adult men and women, aged 22-73 yr, representing a wide range of body mass index values (17.1-36.0 kg/m(2)), who underwent both DXA and CT in a fasting state within 1 h. The coefficient of determination (r(2)) for regression of the CT on DXA values was 0.892 for females, 0.838 for males, and 0.931 combined. Bland-Altman bias was -451.4 cm(3) with 95% limits of agreement of 149.8 to -1052.6 cm(3). The DXA-measured VF showed a better correlation with CT-measured VF volume than common indices for adiposity, including the body mass index and waist circumference. There was a lesser discrepancy ratio between DXA- and CT-measured VF with an increase of VF volume. DXA, a relatively convenient, inexpensive, and safe method with minimum radiation dosage, can be a reliable technique for VF assessment in the Asian population.

[Clinical and ultrasound features of gallbladder pathology in patients with a weight deficit]

We undertook analysis of clinical and instrumental features of gallbladder pathology in patients with a weight deficit for the elucidation of peculiarities of eating behavior, blood leptin level, and cytokine content of gastric biopsies. Underweight patients with inflammatory and dysfunctional diseases of gallbladder more frequently than others presented with abdominal pain syndrome. All patients enrolled in the study showed every type of eating disorders with the predominance of the limiting behavior. Weight deficit in patients with chronic cholecystitis was associated with hyperleptinemia and increased production of proinflammatory cytokines.

Evidence of brown fat activity in constitutional leanness

BACKGROUND

Brown adipose tissue (BAT) was considered essentially nonexistent in adults until recent evidence obtained using 18-fluorodeoxyglucose (18-FDG) positron emission tomography/computed tomography. It seems to play a role in whole body metabolism, but it has not been evaluated in underweight conditions, such as in young females with constitutional leanness (CL) or anorexia nervosa (AN).

SUBJECTS AND METHODS

Thirty-eight subjects were evaluated from October 2011 to March 2012 : 7 CL (21.7 ± 3.6 y, body mass index [BMI] 16.2 ± 1.0 kg/m(2)), 7 AN (23.4 ± 4.5 y, BMI 15.5 ± 0.8), 3 of the 7 AN after stable refeeding (R-AN, 21.3 ± 1.5 y, BMI 18.8 ± 1.1), and 24 normal weight (NW) women (25.6 ± 3.9 y, BMI 22.2 ± 1.5). Fasting resting metabolic rate and respiratory quotient were measured by indirect calorimetry, body composition by bioimpedentiometry (only in CL, AN, and refed AN), and BAT activity by 18-FDG positron emission tomography/computed tomography scan, all in standardized conditions.

RESULTS

All CL (100%), none of the AN and refed AN (0%), and 3 of the 24 NW (12%) subjects showed FDG uptake. Average FDG maximum standardized uptake value was 11.4 + 6.7 g/mL in CL and 5.5 ± 1.2 g/mL (min 3.7, max 8.3) in the 3 NW subjects. In CL, the maximum standardized uptake value was directly correlated to resting metabolic rate, corrected for fat-free mass, and inversely correlated with respiratory quotient.

CONCLUSION

BAT activity has been shown in CL in resting thermoneutral conditions and may exert a role against adipose tissue deposition.

The role of fat and lean mass in bone loss in older men: findings from the CHAMP study

PURPOSE

Weight loss is associated with bone loss; however, it is unclear whether loss of fat or loss of lean body mass plays the key role in this relationship. The aim of this longitudinal analysis was to clarify the relationship between hip BMD, hip BMC and whole body BMC with changes in fat and lean tissue mass in older men.

METHODS

The Concord Health and Aging in Men Project (CHAMP) is a population-based study in Sydney, Australia, involving 1705 men aged 70-97 years. Bone mineral density (BMD) of the total hip, and bone mineral content (BMC) of the hip and whole body (WB), lean mass and fat mass were measured with Dual X-ray Absorptiometry (DXA). Multivariate linear regression models were used to assess relationships.

RESULTS

Over 2.2 years of follow-up, 368(33%) men lost at least 2% of their body weight, which included a mean loss of 0.8 kg/year of lean body mass and 0.9 kg/year of fat body mass. Fat loss was strongly associated with BMD loss in men who lost weight. As a group, weight losers lost 1.0% of hip BMD annually compared to 0.2% in men who gained weight, with each kilo of fat loss associated with 0.6%/year hip BMD loss (p<0.0001). Lean mass was not associated with hip BMD loss in weight losers, however, lean mass change was associated with BMD change in men who gained weight (0.3% hip BMD increase per kilo increase of lean mass p<0.01).

CONCLUSION

Maintaining body weight is important for bone health in elderly men. Body fat plays an important role in this relationship, which may reflect the additional metabolic function of adipose tissue.

Small lesions detectability with the Biograph 16 Hi-Rez PET/CT scanner and fast imaging protocols: performance evaluation using an anthropomorphic thoracic phantom and ROC analyses

OBJECTIVES

The purpose of this study was to evaluate the impact on lesion detectability of fast imaging protocols using 18F-FDG and a 3-dimensional LSO-based PET/CT scanner.

METHODS

An anthropomorphic thoracic phantom was used simulating the anatomical structures of radioactivity distribution for the upper torso of an underweight patient. Irregularly shaped targets of small dimensions, the zeolites, were located inside the phantom in an unpredictable position for the observers. Target-to background ratios and target dimensions were selected in order to sample the range of detectability. Repeated imaging was performed to acquire PET images with varying emission scan duration (ESD) of 1, 2, 3 and 4 min/bed and background activity concentrations of 10, 5 and 3 kBq/mL in the torso cavity. Three observers ranked the targets and a receiver operating characteristic analysis was performed for each acquisition protocol.

RESULTS

Detection performances improved when passing from a short (ESD = 1 min) protocol to longer (ESD C 2 min) protocols. This improvement was established with adequate statistical significance.

CONCLUSIONS

Short image acquisition times of 1 min/bed using 18F-FDG and the specific scanner model considered in the study lead to reduced lesion detectability and should be avoided also in underweight patients.

Aortic and hepatic enhancement at multidetector CT: evaluation of optimal iodine dose determined by lean body weight

PURPOSE

To determine the optimal iodine dose for aortic and hepatic enhancement at MDCT by comparing lean body weight (LBW) with total body weight (TBW).

MATERIALS AND METHODS

This study was approved by our institutional review committee. One hundred and thirty-six patients were randomized into four groups: 550, 650, 750 mg iodine/(kg of LBW) and 600 mgI/(kg of TBW). The aortic and hepatic contrast enhancements (Δ HUs) during the portal venous-phase and variances of ΔHUs were compared.

RESULTS

Mean ΔHUs for 550, 650, 750 mgI/kg LBW and 600 mgI/kg TBW were: 95.1, 109.9, 122.4, and 131.2HU, respectively, for the aorta. For the liver, 43.1, 55.4, 60.8, and 63.5 HU. Mean Δ HUs increased with iodine dose per kg LBW (p<0.01), but no significant difference between 750 mgI/kg LBW and 600 mgI/kg TBW groups. Hepatic enhancement increased by ≥50 HU in 94% of patients with 750 mg/kg LBW. Variance of hepatic enhancement was marginally greater in the 600 mgI/kg TBW than in the 550 and 750 mgI/kg LBW.

CONCLUSION

Hepatic enhancement variation was reduced with iodine doses based on LBW. Iodine dose of 750 mg iodine/kg LBW was appropriate to achieve hepatic enhancement≥50 HU in 94% of patients.

Subepicardial adipose tissue thickness and its relation with anthropometric and clinical parameters in pubertal obese children

AIM

To determine the relation of echocardiographic subepicardial adipose tissue (SAT) thickness with anthropometric and clinical parameters in pubertal obese children.

SUBJECTS AND METHODS

A total of 52 obese pubertal subjects (13.1±1.56 yr, 27 male patients) and 39 age- and gender-matched lean pubertal subjects (13.0±1.28 yr, 16 male patients) were included in the study. Serum glucose, lipid profile, and insulin levels were measured during the fasting state. Each subject underwent a transthoracic echocardiography and the SAT thickness was measured during end-diastole from the parasternal long-axis views.

RESULTS

The obese pubertal subjects had significantly higher SAT, triceps skin fold (TSF) thickness (mm), waist (WC) and mid-arm circumference (MAC) values (cm) compared with lean pubertal subjects group (p<0.05). Correlation analysis showed that SAT thickness was significantly related with age, SD score-body mass index (SDS-BMI), BMI, WC, MAC, TSF, and homeostasis model assessment of insulin resistance (HOMA-IR) (p<0.05), whereas there was no significant relation of SAT with hip circumference and waist to hip ratio (p>0.05). As an optimal cut-off point, a SAT thickness of 5.25 mm determined IR with 92% sensitivity and 62.1% specificity.

CONCLUSIONS

Our study showed that SAT thickness in obese pubertal children shows a good correlation with age, SDS-BMI, BMI, WC, MAC, TSF, and HOMA-IR. In addition, our results suggest that SAT thickness might be used as a supportive data for risk stratification of metabolic syndrome in obese children.

Race and sex differences in bone mineral density and geometry at the femur

INTRODUCTION

Differences in osteoporotic hip fracture incidence between American whites and blacks and between women and men are considered to result, in part, from differences in bone mineral density and geometry at the femur. The aim of this study was to quantify differences in femoral bone density and geometry between a large sample of healthy American white and black women and men.

SUBJECTS AND METHODS

Healthy American white (n=612) and black (n=164) premenopausal women, aged 23 to 57 years, and healthy American white (n=492) and black (n=169) men, aged 20 to 63 years, had volumetric bone mineral density (vBMD) and geometry variables measured at the femur by computerized tomography (CT), and areal bone mineral density (aBMD) at femoral neck measured by dual X-ray absorptiometry (DXA).

RESULTS

American blacks had higher vBMD at the femoral neck and femoral shaft cortex than American whites whereas femoral axis length and femoral neck area were not different. Men had lower vBMD at the femoral neck and femoral cortex than women but had greater femoral axis length and femoral neck area than women. The higher aBMD in American blacks than whites persisted after correction for measured area whereas the higher aBMD in men than women disappeared.

CONCLUSIONS

At the femoral neck, American whites have lower bone density than American blacks but similar geometry. Women have higher bone density than men in both races but have smaller geometry variables. The differences in bone density may account in part for the differences in hip fracture incidence between American blacks and whites, whereas the differences in femur size may account for the differences in hip fracture rates between men and women.

Anti-mullerian hormone is associated with advanced glycosylated end products in lean women with polycystic ovary syndrome

OBJECTIVE

Oocyte maturation process characterizes polycystic ovary syndrome (PCOS). The mechanisms of this abnormality leading to chronic anovulation are under investigation. Advanced glycosylated end products (AGEs), a marker of oxidative stress linked with oocyte maturation are localized in granulosa cells and are increased in sera, in women with PCOS. The aim of this study was to investigate the relationship, whether there is an association between the anti-mullerian hormone (AMH), a hormone produced by granulosa cells and AGEs in ovulatory and anovulatory PCOS (PCOS-Anov), as well as in non-PCOS anovulatory (Non-PCOS Anov) women. Design Cross-sectional study.

METHODS

Data from sixty women with PCOS (37 anovulatory and 23 regularly ovulating) were compared with eleven Non-PCOS Anov women and 25 normal women. In each subject biochemical, hormonal, and ultrasonographic parameters were studied.

RESULTS

AMH values were statistically significantly higher in PCOS-Anov (7.63+/-3.12) in comparison with ovulatory PCOS (PCOS-Ov; 4.92+/-2.50), Non-PCOS Anov (3.66+/-1.4), and controls (4.02+/-1.27 ng/ml). AGEs demonstrated a similar pattern: 8.70+/-1.65 in PCOS-Anov, 7.43+/-1.79, PCOS-Ov, 5.21+/-0.09, Non-PCOS Anov, and 5.85+/-0.89 U/ml in controls (P<0.005 for all comparison respectively). Follicle number was significantly higher in PCOS-Anov in comparison with other groups. A significant positive correlation between AMH and AGEs was observed (r: 0.326, P<0.01), and with the estimated AMH/AGEs ratio to follicle number (r: 0.42, P: 0.0001) and the presence of anovulation.

CONCLUSIONS

These data suggest that an oxidative marker, AGEs, and AMH, may interact in the anovulatory mechanisms in women with PCOS.

High-throughput screening of mouse knockout lines identifies true lean and obese phenotypes

We developed a high-throughput approach to knockout (KO) and phenotype mouse orthologs of the 5,000 potential drug targets in the human genome. As part of the phenotypic screen, dual-energy X-ray absorptiometry (DXA) technology estimates body-fat stores in eight KO and four wild-type (WT) littermate chow-fed mice from each line. Normalized % body fat (nBF) (mean KO % body fat/mean WT littermate % body fat) values from the first 2322 lines with viable KO mice at 14 weeks of age showed a normal distribution. We chose to determine how well this screen identifies body-fat phenotypes by selecting 13 of these 2322 KO lines to serve as benchmarks based on their published lean or obese phenotype on a chow diet. The nBF values for the eight benchmark KO lines with a lean phenotype were > or =1 s.d. below the mean for seven (perilipin, SCD1, CB1, MCH1R, PTP1B, GPAT1, PIP5K2B) but close to the mean for NPY Y4R. The nBF values for the five benchmark KO lines with an obese phenotype were >2 s.d. above the mean for four (MC4R, MC3R, BRS3, translin) but close to the mean for 5HT2cR. This screen also identifies novel body-fat phenotypes as exemplified by the obese kinase suppressor of ras 2 (KSR2) KO mice. These body-fat phenotypes were confirmed upon studying additional cohorts of mice for KSR2 and all 13 benchmark KO lines. This simple and cost-effective screen appears capable of identifying genes with a role in regulating mammalian body fat.

Muscle-bone relationships in the lower leg of healthy pre-pubertal females and males

Muscle-bone relationships in healthy pre-pubertal children were investigated using four muscle measures as predictors of tibial strength: 66% tibia cross-sectional muscle area (CSMA) by pQCT; leg lean mass (LLM) by DXA; and muscle power (Power) and force (Force) measured during a two-footed jump. Polar strength strain index (pSSI), a calculated surrogate for bone strength at the 20% distal tibia, was obtained on 105 (54 male) self-assessed pre-pubertal children. The amount of muscle (CSMA, LLM) may influence bone strength more than muscle strength (Power, Force) during periods of rapid growth. Correlations and multiple regression partial-R values from models controlling for age, sex, height and weight were obtained for each muscle predictor. CSMA, LLM, Power and Force were positively correlated with pSSI (R=0.84, 0.92, 0.85; 0.66, respectively, all p<0.01). Partial-R values were highest for LLM (partial-R=0.21), similar for CSMA and Power (0.14, 0.15, respectively) and lowest for Force (0.04) in predicting pSSI. Muscle predictors were associated with total and cortical area (R=0.59 to 0.90; p<0.01 for all), but not cortical vBMD at the 20% distal tibia site. These data support relationships between muscle predictors and bone parameters measured by pQCT in healthy pre-pubertal children.

Less activation in the left dorsolateral prefrontal cortex in the reanalysis of the response to a meal in obese than in lean women and its association with successful weight loss

BACKGROUND

We previously found that obese men have less activation in the left dorsolateral prefrontal cortex (LDLPFC) in response to a meal than do lean men, which indicates an association between this altered neuronal response and the pathophysiology of obesity.

OBJECTIVES

The objectives of the study were to extend this finding in obese women and to investigate activity in this region in women with a history of severe obesity who have successfully lost weight (ie, formerly obese women, sometimes called postobese women).

DESIGN

We reanalyzed previously collected data to compare postmeal (after receiving a liquid meal) with premeal (after a 36-h fast) regional cerebral blood flow, a marker of neuronal activity, by using (15)O-water positron emission tomography in 10 lean [26 +/- 6% body fat (BF)], 9 obese (39 +/- 3%BF) and 8 formerly obese (28 +/- 4%BF) right-handed women. Data were analyzed by using a 2-level, random-effect analysis of variance.

RESULTS

The regional cerebral blood flow in the LDLPFC differed in response to the meal across the 3 groups (P < 0.001, uncorrected for multiple comparisons). Post hoc group comparisons showed that obese women had significantly less activation in this area than did lean and formerly obese women. No significant difference between formerly obese and lean women was found.

CONCLUSIONS

These results extend our previous findings, indicating that obese women have less activation in the LDLPFC in response to a meal than do lean or formerly obese women. Neuronal activity in this region did not differ significantly between the latter 2 groups. Longitudinal studies are needed to determine whether these differences in neuronal activity change with or predict weight change.

Hypovitaminosis D osteopathy: is it mediated through PTH, lean mass, or is it a direct effect?

Hypovitaminosis D is increasing worldwide and is associated with low bone mass. The effects of hypovitaminosis D on bone might be direct or mediated through decreased muscle mass and function and/or secondary hyperparathyroidism. This study systematically investigated the relative contribution of lean mass, PTH, and the direct effect of vitamin D as predictors of vitamin D mediated osteopathy in elderly individuals. 460 ambulatory subjects aged 65-85 years had their bone mass and lean body mass measured by a dual-energy X-ray absorptiometry. Serum calcium, phosphorus and alkaline phosphatase, intact parathyroid hormone (PTH) and 25-hydroxyvitamin D (25 OHD) were also measured. Serum 25 OHD correlated with lean body mass in men, r = 0.24, P = 0.002, but not in women; and with bone mass at all skeletal sites in men, r = 0.20-0.30, P < 0.02. Correlations were also noted at all skeletal sites in women except for the spine, r = 0.13-0.18, P < 0.04. In both genders, BMD at sites enriched in cortical bone was 0.4-0.7 SD lower in the group with the lowest vitamin D tertile than that in the group in the highest tertile. After controlling for PTH, the magnitude of the correlations between BMD and 25 OHD remained significant in both genders. After controlling for lean body mass, the magnitude of these correlations did not change in women and decreased but remained significant in men. After adjustment for age and height, both lean body mass and PTH had significant independent contributions to BMD variance at all skeletal sites. After adjustment for age, height, lean mass, and PTH, 25 OHD did not have any significant residual contribution to BMD variance except at the trochanter in men. This study demonstrates that vitamin D osteopathy in the elderly is in large part mediated through lean mass in men and through PTH levels in both genders, with a greater contribution of PTH in women than in men. There was little demonstrable independent relation between serum 25 OHD and bone mass.

The in vivo cardiac kinetics of Tc-99m N-NOET are accelerated in obese, hyperlipidemic Zucker rats

BACKGROUND

Previous studies demonstrated that the intrinsic myocardial washout of bis(N-ethoxy,N-ethyldithiocarbamato)nitrido technetium(V) (technetium 99m N-NOET) was affected by changes occurring in the intravascular compartment such as variations in circulating lipid levels. We sought to determine whether the myocardial kinetics of Tc-99m N-NOET were affected by hyperlipidemia in a clinically relevant experimental model.

METHODS AND RESULTS

Tc-99m N-NOET (50 MBq/kg) and thallium 201 (12 MBq/kg) were injected intravenously into hyperlipidemic fa/fa Zucker rats (n=6) and their lean, normolipidemic littermates (n=8), and dual-isotope in vivo planar imaging was performed for 60 minutes. In vivo image quantification indicated significantly faster cardiac washout of Tc-99m N-NOET in fa/fa animals versus lean animals (time constant, 411+/-64 minutes vs 1094+/-226 minutes, respectively; P<.05), whereas Tl-201 cardiac washout was not affected (356+/-85 minutes vs 337+/-53 minutes, respectively; P=not significant).

CONCLUSION

The cardiac kinetics of Tc-99m N-NOET, but not those of Tl-201, were accelerated after intravenous injection of the tracer in fa/fa Zucker rats with circulating lipid levels similar to those encountered clinically in hyperlipidemic patients. The relationship between lipidemia and the rate of Tc-99m N-NOET myocardial washout warrants further clinical investigation.

Dual-energy X-ray absorptiometry lean soft tissue hydration: independent contributions of intra- and extracellular water

Dual-energy X-ray absorptiometry (DEXA) provides a measure of lean soft tissue (LST). LST hydration, often assumed to be constant, is relevant to several aspects of DEXA body composition estimates. The aims of this study were to develop a theoretical model of LST total body water (TBW) content and to examine hydration effects with empirically derived model coefficients and then to experimentally test the model's prediction that, in healthy adults, LST hydration is not constant but varies as a function of extra- and intracellular water distribution (E/I). The initial phase involved TBW/LST model development and application with empirically derived model coefficients. Model predictions were then tested in a cross-sectional study of 215 healthy adults. LST was measured by DEXA, extracellular water (ECW) by NaBr dilution, intracellular water (ICW) by whole body (40)K counting, and TBW by (2)H(2)O dilution. TBW estimates, calculated as ECW + ICW, were highly correlated with (r = 0.97, SEE = 2.1 kg, P < 0.001) and showed no significant bias compared with TBW measured by (2)H(2)O. Model-predicted TBW/LST was almost identical to experimentally derived values (means +/- SD) in the total group (0.767 vs. 0.764 +/- 0.028). LST hydration was significantly correlated with E/I (total group, r = 0.30, SEE = 0.027, P < 0.001). Although E/I increased with age (men, r = 0.48; women, r = 0.37; both P < 0.001), the association between TBW/LST and age was nonsignificant. Hydration of the DEXA-derived LST compartment is thus not constant but varies predictably with ECW and ICW distribution. This observation has implications for the accuracy of body fat measurements by DEXA and the use of TBW as a means of checking DEXA system calibration.

Body composition of newborn twins: intrapair differences

OBJECTIVE

To measure body composition in newborn twins and to test the hypothesis that differences in body weights between twins are reflected proportionally by their differences in various components of body composition.

METHODS

48 pairs of newborn twins delivered at a tertiary teaching hospital had dual energy x-ray absorptiometry (DXA) body composition measurement for bone mineral content (BMC), lean and fat mass (LM, FM). Data analyzed with regression and analysis of variance.

RESULTS

Body weight, BMC, LM and FM increased with increased gestational age (p < 0.001). The percent difference in BW between each twin pair was significantly correlated with percent difference in BMC, LM, and FM (p < 0.001). However, mean (+/- SD) percent difference in body weight (14.3+/-10.0%) was significantly lower (p < 0.001) than FM (26.0+/-15.0%) but was not significantly different from LM (13.4+/-9.0%) or BMC (15.9+/-11.6%).

CONCLUSION

In newborn twins, body weight and body composition varies with gestational age. For any twin pair, a difference in body weight was correlated with but not proportional to differences in individual components of body composition.

2-[(18)F]fluoro-2-deoxy-D-glucose combined with microdialysis can be used for the comparison of tissue glucose metabolism in obese and lean rats

AIMS

Direct assessment of tissue metabolism in vivo is important to understand the pathogenesis of obesity. Labelled glucose analogues are potential candidates to be used for this purpose. The aim of this study was to compare the kinetics and metabolism of 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) in obese (fa/fa) and lean (Fa/?) Zucker rat tissues with microdialysis, and the measurement of uptake and phosphorylation with or without insulin bolus injection.

METHODS

Obese (n = 10) and lean (n = 11) anaesthetized rats underwent a microdialysis study after FDG-injection either with or without insulin stimulation. Microdialysis probes were inserted in the jugular vein, quadriceps muscle and liver. After 110 min, tissue [(18)F]-uptake and intracellular phosphorylation of FDG were studied in blood, liver, skeletal muscle, subcutaneous adipose tissue, intra-abdominal adipose tissue and hypothalamus.

RESULTS

When measured with microdialysis, insulin-enhanced FDG disappeared from the blood pool and interstitial space of skeletal muscle and liver more effectively in lean rather than in obese animals. Insulin-stimulated skeletal muscle and adipose tissue[(18)F]-uptake was impaired in obese Zucker rats compared with lean animals. Hypothalamic FDG uptake was six to sevenfold higher than in other measured tissues, but was attenuated in obese rats. In liver and in mesenteric fat, insulin-enhanced FDG phosphorylation in lean rats compared with obese animals.

CONCLUSIONS

Positron-emitting glucose analogue FDG, combined with microdialysis and tissue analysis, is a feasible method in studying glucose metabolism at the cellular level in animal studies.