Date Published: July 6, 2017
Publisher: Public Library of Science
Author(s): Tomasz Miazgowski, Robert Kucharski, Marta Sołtysiak, Aleksandra Taszarek, Bartosz Miazgowski, Krystyna Widecka, Vanessa Souza-Mello.
Dual energy X-ray absorptiometry (DXA) is an established technique used in clinical and research settings to evaluate total and regional fat. Additionally, recently developed software allow to quantify visceral adipose tissue (VAT). Currently, there are no reference values available for GE Healthcare DXA systems for VAT. The aim of this study was to develop reference values for VAT in healthy European adults aged 20–30 years using a GE Healthcare Prodigy densitometer along with the dedicated CoreScan application. We also assessed the associations of VAT with traditional cardiometabolic risk factors. In 421 participants (207 men; 214 women), we performed DXA whole-body scans and calculated total body fat (BF) and VAT (in gender-specific percentiles). We also measured blood pressure and fasting glucose, insulin, and blood lipids. Males, in comparison with females, had 2-fold greater VAT both in units of mass (542 ± 451 g; 95% CI: 479.6‒605.1 g vs. 258 ± 226 g; 95% CI: 226.9‒288.6 g) and volume (570 ± 468 cm3; 95% CI: 505.1‒635.2 cm3 vs. 273 ± 237 cm3; 95% CI: 240.6‒305.3 cm3). They also had significantly higher the VAT/BF ratio. VAT showed a stronger positive correlation than BF with blood pressure, triglycerides, LDL-cholesterol, glucose, insulin, and homeostasis model assessment-insulin resistance index and a stronger negative correlation with HDL-cholesterol. Among these variables, VAT had the highest area under the curve for triglycerides ≥150 mg/dL (0.727 in males and 0.712 in females). In conclusion, we provide reference values for VAT obtained from healthy adults using the GE Healthcare DXA. These values may be useful in the diagnosis of visceral obesity, for identifying subjects with high obesity-related risks, in epidemiological studies, as a target for therapies, and in physically trained individuals. In both genders, VAT was associated with traditional cardiometabolic risk factors, particularly hypertriglyceridemia.
The excessive accumulation of visceral adipose tissue (VAT) leads to visceral obesity and induces low-grade systemic inflammation, which is mediated by fat-infiltrating immune cells and increased release of proinflammatory cytokines [1–4]. Although the exact mechanisms that initiate VAT accumulation have not been fully elucidated, it is generally believed that excess VAT is closely associated with the development of a cluster of metabolic derangements, hypertension, cardiovascular disease, and malignancies. Visceral obesity can be estimated using several surrogate methods based on anthropometric measures, such as waist circumference, waist-to-hip ratio, waist-to-height ratio, or sagittal abdominal diameter. However, these indices do not allow distinguishing between VAT and subcutaneous abdominal fat and, in general, are fundamentally inaccurate in quantifying VAT . VAT is a relatively small component of total body fat; however, due to known metabolic effects of VAT, there is constantly increasing interest in this fat depot as an attractive target for non-pharmacological [6, 7] and pharmacological interventions .
Baseline characteristics of studied participants are shown in Table 1.
In this cross-sectional study using the GE Healthcare Lunar Prodigy densitometer, we developed reference values for VAT derived from a homogenous group of healthy European adults aged 20–30 years. These reference values may be useful for identifying subjects with excess visceral fat and high obesity-related risks, in epidemiological studies, as a target for therapies, and in physically trained individuals. However, whether the definition of visceral obesity based on the cutoffs calculated in this study is useful and appropriate requires further investigation. Future research should look at visceral obesity-related morbidity and outcomes using the same modality. This is because body composition is not only influenced by sex, age, geographic location, and ethnicity [16–19] but also the method of assessment. The VAT indices measured by CT, MRI, and DXA, although strongly correlated, may differ both in absolute values and type of units as they may be expressed in units of mass, area, or volume. Even if the same method is used but the measures are performed on instruments from different manufacturers, the results may vary significantly. Regarding DXA, inter-device differences in body composition between two dominant manufacturers (GE Healthcare and Hologic) have been demonstrated [20, 21], suggesting possible similar inter-machine differences in assessing VAT. Therefore, DXA-VAT reference values should be developed as specific for each manufacturer until they are cross-validated.