Abstract 17370: Precise Measures of Insulin Sensitivity, Adiposity, and Cardiorespiratory Fitness Explain Differences in Insulin Resistance Between South Asians and Europeans
Introduction: South Asians (SAs) are more insulin resistant (IR) and at substantially higher risk of Type 2 diabetes and coronary artery disease compared to Europeans (EURs). Whether SAs possess a unique predisposition to IR that is independent of differences in adiposity and cardiorespiratory fitness remains unclear.
Hypothesis: Increased insulin resistance in SAs compared to EURs at similar BMI is largely a consequence of suboptimal assessment of degree of adiposity, cardiorespiratory fitness, and insulin sensitivity.
Methods: Forty-six SAs (mean age: 43.0 ± 8.3, 18 women) and 40 EURs (mean age: 52.0 ± 12.3, 20 women) volunteers with no history of diabetes or CAD underwent ‘gold standard’ measures of adiposity, cardiorespiratory fitness, and insulin resistance including a dual energy X-ray absorptiometry scan to quantify truncal % fat, an exercise treadmill test with a metabolic cart to determine max V02, and an insulin suppression test (IST) to directly measure whole body insulin sensitivity. Physical activity in the week prior to the IST was assessed with the International Physical Activity Questionnaire (IPAQ).
Results: Mean insulin sensitivity, estimated by the steady state plasma glucose (SSPG) during the IST, was 113 mg/dl (SD= 55.9 mg/dl). The three strongest univariate predictors of SSPG were truncal % fat, max V02, and BMI (coefficient of determination R2 = 0.37, 0.27, 0.17, respectively, p < 0.0001 for all). Multivariate linear regression analyses restricted to age, sex, and BMI, confirmed a higher degree of insulin resistance in SAs (mean SSPG 38.4 mg/dl higher in SA compared to EUR, p=0.001), but race/ethnic differences in IR were substantially attenuated and no longer significant when truncal % fat and measures of cardiorespiratory fitness were added to multivariate models. A model restricted to truncal % fat, max V02, and the IPAQ determined MET-min/week resulted in the highest coefficient of determination (R2=0.40) and the lowest race/ethnic difference in IR (mean SSPG 7.9 higher in SA, p=0.45).
Conclusions: Differences in direct measures of IR between SAs and EURs can be explained by differences in adiposity and cardiorespiratory fitness, which may not be adequately captured through assessment of proxies of these variables.
Author Disclosures: S. Zarafshar: None. M. Srinivasan: None. K.N. Chan: None. J. Giacomini: None. M. Divakaruni: None. J.N. Myers: None. L. Palaniappan: None. F. Abbasi: None. T.L. Assimes: Research Grant; Significant; Telomere Diagnostics, Regeneron Genetics Center.
- © 2016 by American Heart Association, Inc.