Abdominal adiposity depots are correlates of adverse cardiometabolic risk factors in Caucasian and African-American adults

Sex-specific equations to estimate body composition: Derivation and validation of diagnostic prediction models using UK Biobank

BACKGROUND & AIMS

Body mass index and waist circumference are simple measures of obesity. However, they do not distinguish between visceral and subcutaneous fat, or muscle, potentially leading to biased relationships between individual body composition parameters and adverse health outcomes. The purpose of this study was to develop and validate prediction models for volumetric adipose and muscle.

METHODS

Based on cross-sectional data of 18,457, 18,260, and 17,052 White adults from the UK Biobank, we developed sex-specific equations to estimate visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (ASAT), and total thigh fat-free muscle (FFM) volumes, respectively. Volumetric magnetic resonance imaging served as the reference. We used the least absolute shrinkage and selection operator and the extreme gradient boosting methods separately to fit three sequential models, the inputs of which included demographics and anthropometrics and, in some, bioelectrical impedance analysis parameters. We applied comprehensive metrics to assess model performance in the temporal validation set.

RESULTS

The equations that included more predictors generally performed better. Accuracy of the equations was moderate for VAT (percentage of estimates that differed <30% from the measured values, 70 to 78 in males, 64 to 69 in females) and good for ASAT (85 to 91 in males, 90 to 95 in females) and FFM (99 to 100 in both sexes). All the equations appeared precise (interquartile range of the difference, 0.89 to 1.76 L for VAT, 1.16 to 1.61 L for ASAT, 0.81 to 1.39 L for FFM). Bias of all the equations was negligible (-0.17 to 0.05 L for VAT, -0.10 to 0.12 L for ASAT, -0.07 to 0.09 L for FFM). The equations achieved superior cardiometabolic correlations compared with body mass index and waist circumference.

CONCLUSIONS

The developed equations to estimate VAT, ASAT, and FFM volumes achieved moderate to good performance. They may be cost-effective tools to revisit the implications of diverse body components.

The Year in Cardiothoracic Transplantation Anesthesia: Selected Highlights from 2019

The highlights in cardiothoracic transplantation focus on the recent research pertaining to heart and lung transplantation, including expansion of the donor pool, the optimization of donors and recipients, the use of mechanical support, the perioperative and long-term outcomes in these patient populations, and the use of transthoracic echocardiography to diagnose rejection.

CT-defined visceral adipose tissue thresholds for identifying metabolic complications: a cross-sectional study in the United Arab Emirates

OBJECTIVES

Visceral adipose tissue (VAT) is closely related to obesity complications. We aimed to determine the optimal sex-specific and age-specific VAT thresholds for predicting metabolic complications among individuals living in the United Arab Emirates (UAE).

DESIGN

Retrospective cross-sectional study.

SETTING

We reviewed medical records of adults who visited a hospital in the UAE.

PARTICIPANTS

A total of 369 subjects were included in the final analysis after application of inclusion and exclusion criteria.

PRIMARY OUTCOME MEASURES

The prevalence of metabolic syndrome (MES).

RESULTS

MES measures excluding waist circumference were present in 73.4% of women and 78.5% of men. VAT areas adjusted for age were significantly greater in the MES group compared with the non-MES group regardless of sex (p<0.05 for all relations); however, subcutaneous adipose tissue areas adjusted for age were not significantly different. Areas under the curve used to predict MES were statistically significant for VAT and visceral to subcutaneous fat ratios among both men and women. Identified cut-off values of VAT to predict MES were 132.0 cm² in both sexes for individuals under the age of 50 years. For those over 50 years of age, VAT thresholds were greater in women compared with men (173 cm² vs 124.3 cm², respectively).

CONCLUSIONS

Optimal VAT cut-offs to predict MES were 132 cm² for individuals under 50 years old living in the UAE. These measures are potential target visceral fat values that could be used to reduce obesity-related morbidity in populations with pre-existing metabolic complications.

Adipose tissue quantification and primary graft dysfunction after lung transplantation: The Lung Transplant Body Composition study

BACKGROUND

Obesity is associated with an increased risk of primary graft dysfunction (PGD) after lung transplantation. The contribution of specific adipose tissue depots is unknown.

METHODS

We performed a prospective cohort study of adult lung transplant recipients at 4 U.S. transplant centers. We measured cross-sectional areas of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) on chest and abdominal computed tomography (CT) scans and indexed each measurement to height.2 We used logistic regression to examine the associations of adipose indices and adipose classes with grade 3 PGD at 48 or 72 hours, and Cox proportional hazards models to examine survival. We used latent class analyses to identify the patterns of adipose distribution. We examined the associations of adipose indices with plasma biomarkers of obesity and PGD.

RESULTS

A total of 262 and 117 subjects had available chest CT scans and underwent protocol abdominal CT scans, respectively. In the adjusted models, a greater abdominal SAT index was associated with an increased risk of PGD (odds ratio 1.9, 95% CI 1.02-3.4, p = 0.04) but not with survival time. VAT indices were not associated with PGD risk or survival time. A greater abdominal SAT index correlated with greater pre- and post-transplant leptin (r = 0.61, p < 0.001, and r = 0.44, p < 0.001), pre-transplant IL-1RA (r = 0.25, p = 0.04), and post-transplant ICAM-1 (r = 0.25, p = 0.04). We identified 3 latent patterns of adiposity. The class defined by high thoracic and abdominal SAT had the greatest risk of PGD.

CONCLUSIONS

Subcutaneous, but not visceral, adiposity is associated with an increased risk of PGD after lung transplantation.

Association of longitudinal risk profile trajectory clusters with adipose tissue depots measured by magnetic resonance imaging

The objective of the study was to identify associations of longitudinal trajectories of traditional cardiometabolic risk factors with abdominal and ectopic adipose tissue depots measured by magnetic resonance imaging (MRI). We measured total abdominal, visceral, and subcutaneous adipose tissue in liter and intrahepatic, intrapancreatic and renal sinus fat as fat fractions by MRI in 325 individuals free of cardiovascular disease at Exam 3 of a population-based cohort. We related these MRI measurements at Exam 3 to longitudinal risk profile trajectory clusters, based on risk factor measurements from Exam 3, Exam 2 (seven years prior to MRI) and Exam 1 (14 years prior to MRI). Based on the levels and longitudinal trajectories of several risk factors (blood pressure, lipid profile, anthropometric measurements, HbA1c), we identified three different trajectory clusters. These clusters displayed a graded association with all adipose tissue traits after adjustment for potential confounders (e.g. visceral adipose tissue: β_ClusterII = 1.30 l, 95%-CI:[0.84 l;1.75 l], β_ClusterIII = 3.32 l[2.74 l;3.90 l]; intrahepatic: Estimate_ClusterII = 1.54[1.27,1.86], Estimate_ClusterIII = 2.48[1.93,3.16]. Associations remained statistically significant after additional adjustment for the risk factor levels at Exam 1 or Exam 3, respectively. Trajectory clusters provided additional information in explaining variation in the different fat compartments beyond risk factor profiles obtained at individual exams. In conclusion, sustained high risk factor levels and unfavorable trajectories are associated with high levels of adipose tissue; however, the association with cardiometabolic risk factors varies substantially between different ectopic adipose tissues. Trajectory clusters, covering longitudinal risk profiles, provide additional information beyond single-point risk profiles. This emphasizes the need to incorporate longitudinal information in cardiometabolic risk estimation.

Testosterone a key factor in gender related metabolic syndrome

Metabolic syndrome (MetS) is highly correlated with cardiovascular diseases. Although an excess of body fat is a determinant factor for MetS development, a reduced level of testosterone plays a fundamental role in its regulation. Low testosterone level is highly related to insulin resistance, visceral obesity and MetS. We have searched in Pubmed clinical trial with the password: testosterone and insulin resistance, and testosterone and MetS. We found 19 studies on the correlation between testosterone level with insulin resistance and 18 on the effect of testosterone therapy on MetS. A high correlation between low testosterone and insulin resistance has been found in men, but not in women. Testosterone administration in hypogonadal men improved MetS and reduced the mortality risk. Androgen and oestrogen receptors are expressed in adipocytes, muscle and liver tissue, and their activation is necessary to improve metabolic control. Normalization of testosterone level should be the primary treatment in men, along with caloric restriction and physical exercise. These findings come mainly from correlative data, and there remains a need for randomized trials to strengthen this evidence. This review will consider the effects of testosterone on the regulation and development of MetS in men and women.

3D vascular anatomy of the presacral space: impact of age and adiposity

INTRODUCTION AND HYPOTHESIS

Defining patient characteristics that alter vascular anatomy at the sacrum is critical for avoiding life-threatening bleeding at the time of sacrocolpopexy. We tested the hypothesis that in thinner/older women, the bifurcations of the aorta and inferior vena cava (IVC) are lower relative to S1 resulting in less space accessible for suture/mesh placement, placing this group at increased risk of major vascular injury.

METHODS

In a retrospective cross-sectional study, CT scans were used to make 2D measurements and a 3D model of the aorta/IVC, intervertebral disc space, and bony anatomy using segmentation and modeling software. For analysis, Spearman's and Pearson's correlation, Student's t test and the Mann-Whitney U test were used along with multivariate analysis of variance.

RESULTS

Of eligible women who had undergone abdominal/pelvic CT, 107 were included. The median locations of the aortic and IVC bifurcations utilizing 2D analysis were at the inferior L4 and middle L5 vertebral body, respectively. In 10.2% of patients, the IVC was located at the L5-S1 disc space or lower; however, 3D modeling of this space which allowed assessment of the area below the S1 "drop off" showed that the amount of accessible space for suture/mesh placement was not decreased. Utilizing 2D analysis there was no statistically significant independent correlation between age or adiposity and the aortic or IVC bifurcation. Patients who were both elderly and thinner had a lower aortic bifurcation (p = 0.005) and a trend towards a lower IVC bifurcation (p = 0.082).

CONCLUSIONS

In 10.2% of women, the IVC bifurcation descended at or below the L5-S1 disc space, suggesting that this group of women is at increased risk of major vascular injury. Patients who were both thin and elderly had lower bifurcations, but there was no difference in accessible surface area for suture placement on 3D analysis. 3D modeling improved visualization of the anatomy beyond the S1 "drop off" and may provide a future tool for surgical planning once predictors of high-risk anatomy are defined.

Uncovering physiological mechanisms for health disparities in type 2 diabetes

Type 2 diabetes (T2D) prevalence in the United States is significantly higher in African Americans vs Whites. Yet, the physiological mechanisms contributing to this health disparity have been poorly described. To design effective strategies to reduce this disparity, there is a need to determine whether racial differences in diabetes prevalence are attributable to modifiable or non-modifiable factors. This review synthesizes and critically evaluates the potential physiological and genetic mechanisms that may contribute to the higher susceptibility of African Americans to T2D. These mechanisms include: 1) obesity and fat distribution; 2) metabolic flexibility; 3) muscle physiology; 4) energy expenditure and fitness; and 5) genetics. We focus on the clinical significance of findings and limitations of the recent literature.

Distribution of abdominal obesity and fitness level in overweight and obese korean adults

Background. Abdominal obesity and its relative distribution are known to differ in association with metabolic characteristics and cardiorespiratory fitness. This study aimed to determine an association between fitness level and abdominal adiposity in overweight and obese adults. Methods. 228 overweight and obese individuals were classified as either cardiorespiratory unfit or fit based on their recovery heart rate. Visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), the visceral-to-subcutaneous adipose tissue ratio (VAT/SAT ratio), and cardiometabolic characteristics were analyzed to examine the relationship between recovery heart rate and abdominal adiposity components. Results. After adjustments for age and sex, significant relationships of recovery heart rate and VAT, SAT, and VAT/SAT ratio were found; however, SAT was not significantly associated after further adjustment for body mass index (BMI) (r = 0.045, P = 0.499), whereas VAT (r = 0.232, P < 0.001) and VAT/SAT ratio (r = 0.214, P = 0.001) remained associated. Through stepwise multiple regression analyses after adjustment for age, sex, BMI, lifestyle factors, mean blood pressure, fasting glucose, HOMA-IR, lipid profiles, and hsCRP, recovery heart rate was identified as an independent variable associated with VAT (β = 0.204, P < 0.001) and VAT/SAT ratio (β = 0.163, P = 0.008) but not with SAT (β = 0.097, P = 0.111). Conclusions. Cardiorespiratory fitness level is independently associated with VAT and the VAT/SAT ratio but not with SAT in overweight and obese adults.

Adiposity in children and adolescents: correlates and clinical consequences of fat stored in specific body depots

The 2011 Pennington Biomedical Research Center's Scientific Symposium focused on adiposity in children and adolescents. The symposium was attended by 15 speakers and other invited experts. The specific objectives of the symposium were to (i) integrate the latest published and unpublished findings on the laboratory and clinical assessment of depot-specific adiposity in children and adolescents, (ii) understand the variation in depot-specific adiposity and related health outcomes associated with age, sex, maturation, ethnicity and other factors and (iii) identify opportunities for incorporating new markers of abdominal obesity into clinical practice guidelines for obesity in children and adolescents. This symposium provided an overview of important new advances in the field and identified directions for future research. The long-term goal of the symposium is to aid in the early identification of children and adolescents who are at increased health risk because of obesity and obesity-related conditions.