DEXA-Measured VAT Robustly Predicts Impaired Glucose Tolerance and Metabolic Syndrome in Obese Women

Abdominal visceral adiposity (VAT) has been shown to be an independent risk factor for metabolic and cardiovascular disease. Using enCORE analysis version 13.6 on a GE Lunar iDXA, a new fully automated analysis software to measure VAT, we determined the strength of associations between DEXA-derived VAT and other known indicators for diabetes and cardiovascular disease risk in Caucasian and African American obese women. We collected anthropometrics, vital signs, lipid profile, and DXA whole body composition scan for 229 subjects with BMI 30.0 – 49.9 kg/m2 & age 21 to 69 y. We then performed the non-parametric Spearman correlation analysis and found that in subjects overall, DEXA-VAT is positively associated with triglyceride, fasting glucose, fasting insulin, and HOMA-IR, and negatively associated with HDL. Among all anthropometric, body composition and cardiometabolic variables, DEXA-VAT was the most robust predictor of impaired glucose tolerance (IGT) and metabolic syndrome (MetSx) in binary regression analysis, even after adjusting for race. LASSO regression after adjusting for covariates that best predicted IGT and MetSx showed that HOMAIR and DEXA-VAT most significantly predicted IGT (p<0.001, p<0.001, respectively), and DEXA-VAT most significantly predicted MetSx (p<0.001). These observations have implications for VAT associated risk in diabetes and cardiovascular disease. INTRODUCTION • Abdominal obesity, especially the visceral component of adipose tissue (VAT), is strongly associated with metabolic and cardiovascular risk in humans (1-2). • The differences in sex and race with regard to body composition and metabolic risk have also been demonstrated with VAT associated risk. • Although CT and MRI are considered the “gold standards” in the measurement of type and distribution of body fat, dual energy X-ray absorptiometry (DEXA) can accurately measure body composition with high-precision, low X-ray exposure, and short-scanning time (3). • We previously showed strong correlations between DEXA and MRI whole body composition, with coefficients of variation of ≤ 2% for DEXAderived adiposity measures (4). • In addition to whole body composition, we now have a newly available software to estimate VAT area (cm3) and mass (g) using enCORE analysis version 13.6 (5) on a GE Lunar iDXA. METHODS Study: Cross-sectional design of subjects previously recruited for studies at the Vanderbilt Clinical Research Center. Subjects: 229 subjects with BMI 30.0 – 49.9 kg/m2 & age 21 to 69 y. All records de-identified. Measures Anthropometrics Height, weight, BMI, Waist & hip circumference (WC & HC), waist-to-hip ratio (WHR), waist-toheight ratio (WHtR) Lipid profile Total cholesterol, HDL, LDL, triglyceride (TG) Fasting glucose, insulin, HOMA-IR DEXA whole body composition scan Metabolic disease states • Impaired Glucose tolerance (IGT): fasting glucose ≥100 mg/dL • Metabolic Syndrome defined as ≥ 3 of the following: 1. WC (>102 cm for , >88 cm for ); 2. TG (≥150 mg/dl); 3. HDL (<40 mg/dl in , <50 mg/dl in ); 4. hypertension (≥130/≥85 mmHg); 5. impaired fasting glucose (≥100 mg/dl). Analysis: R version 3.0. 1 analyzed with nonparametric distribution. RESULTS DEXA-VAT Associations with Metabolic Risk Factors Overall, DEXA-VAT was positively associated with SBP, DBP, TG, fasting glucose & insulin, HOMA-IR, and negatively associated with HDL. DEXA-VAT was still associated with SBP, DBP, insulin, and HOMA-IR after adjusting for race, and associated with hsCRP after adjusting for the int’n with race. RESULTS Multivariate LASSO Regression for IGT A: combination of anthropometric, body composition, and cardiometabolic variables guided by previous binary regressions presented with adjusted odds ratios (OR); B: ANOVA analysis of A adjusted for race; C: ANOVA analysis of A adjusted for interaction with race. Multivariate LASSO Regression for MetSx A: combination of anthropometric, body composition, and cardiometabolic variables guided by previous binary regressions presented with adjusted odds ratios (OR); B: ANOVA analysis of A adjusted for race; C: ANOVA analysis of A adjusted for interaction with race. CONCLUSION • DEXA-VAT was positively associated with TG, fasting glucose & insulin, and HOMA-IR, and negatively associated with HDL-C • In binary regression analysis, DEXA-VAT was a more robust predictor of IGT and MetSx than other anthropometric and body composition variables • In Mutivariate LASSO regression, the odds ratio for having IGT was most robustly predicted by HOMAIR and DEXA-VAT; the odds ratio for having MetSx was most robustly predicted by DEXA-VAT REFERENCES 1. Canoy D. Distribution of body fat and risk of coronary heart disease in men and women. Curr Opin Cardiol. 2008 Nov;23(6):591-8. 2. Shuster A, Patlas M, Pinthus JH, Mourtzakis M. The clinical importance of visceral adiposity: a critical review of methods for visceral adipose tissue analysis. Br J Radiol. 2012 Jan;85(1009):1-10. 3. Direk K et al. The relationship between DXA-based and anthropometric measures of visceral fat and morbidity in women. BMC Cardiovasc Disord. 2013 Apr 3;13:25. 4. Silver HJ et al. Comparison of gross body fat-water magnetic resonance imaging at 3 Tesla to dual-energy X-ray absorptiometry in obese women. Obesity. 2013 Apr;21(4): 765-74. 5. Kaul S, et al. Dual-energy X-ray absorptiometry for quantification of visceral fat. Obesity (Silver Spring). 2012 Jun;20(6):1313-8. ACKNOWLEDGEMENT Research supported by multiple sources obtained by Silver, Buchowski, Shibao & NIH T35DK007383 DEXA-Measured VAT Robustly Predicts Impaired Glucose Tolerance and Metabolic Syndrome in Obese Women 1Bi X. , 2Keil C.D. , 2Seabolt L. , 2Tyree R. , 2Buchowski M. , 2Kang H. , 2Shibao C. , 2Silver H.J. 1Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA 2Department of Medicine, School of Medicine of Vanderbilt University, Nashville, TN