SIMPLE MEASUREMENT AND FORMULAS FROM ORAL GLUCOSE TOLERANCE TEST PROVIDE ACCURATE AND BETTER EVALUATION OF INSULIN SENSITIVITY AND SECRETION THAN THE MORE ELABORATE MODELS: COMPARISON WITH THE MINIMAL MODEL ANALYSIS OF INTRAVENOUS GLUCOSE TOLERANCE TEST

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 780-806-Determinants of Insulin Resistance & Associated Metabolic Disturbances
Basic/Translational
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-789
Buvana Manickam*1, Arfana Akbar2, Yuval Eisenberg1 and Elena Barengolts3
1University of Illinois at Chicago, College of Medicine, Chicago, IL, 2Jesse Brown VAMC, Chicago, IL, 3University of Illinois, College of Medicine, Chicago, IL
Introduction: Several indices of insulin sensitivity (SI) and β-cell function derived from oral glucose tolerance test (OGTT) have been proposed and validated against the clamp or the intravenous glucose tolerance test (IVGTT) (1). These indices are not validated in African American men (AAM) with high burden of chronic disease.

Objective: To determine which OGTT-derived indices give the best prediction of indices from IVGTT, i.e. SI and its reciprocal insulin resistance (1/SI), AIRg (acute-insulin-response-to-glucose measuring insulin secretion), and DI (disposition index =SIxAIRg measuring b-cell compensation).

Methods: AAM (N=50, A1C 5.7-6.9%, not on any anti-diabetic medications) were recruited from an inner city VA as part of an ongoing clinical trial and underwent OGTT and IVGTT. We calculated 29 OGTT-derived indices based on the formulas from the previous studies and our own and correlated these with IVGTT-derived indices. The accuracy of the empiric formulas obtained were evaluated with Bland-Altman plots.

Results: Subject characteristics and OGTT-derived values were (Mean±SD): age 60.0±4.8yrs; BMI 32.2±2.5kg/m2; glucose (G, mg/dl) fasting (Gf) 98.6 ±15.0, mean (Gm) 129±22, peak (Gp) 185±40; insulin (I) (µU/ml) fasting (If) 18.6±16.5, mean (Im) 13.9±6.2, peak (Ip) 223.3±92.8; mean area under the glucose curve (AUCGm=AUCGtotal/number of time points) 2707±533; and Charlson index of chronic disease 2.2±1.2. Prevalence of hypertension, hyperlipidemia, and psychiatric problems was 68%, 55%, and 73%, respectively. The IVGTT-derived values were (standard Minmod units for all) SI 2.9±1.1, AIRg 449±291, DI 1159±798. Correlation analysis between IVGTT and OGTT-derived indices showed the highest r values for 1/SI: Insulinogenic Index peak [IGIp=(Ip-If)/(Gp-Gf)] r=.590, Ip/Gp r=.589, Ip r=.562 (p≤.0001 for all) while for SI, AIRg and DI the highest r values varied between -.50 and -.42 and included Gm, Gp, AUCGm, and IGIp (p≤0.01 for all). Correlations of 1/SI with widely accepted and commonly used indices were: Matsuda-DeFronzo (2) ISI r=-.13 p=.4, Mari’s (3) OGIS r=-.29 p=.04, and Retnakaran’s (4) ISSI-2 -.21 p=.2. Among other indices only ISSI-2 correlated with AIRg r=.37 and DI r=.31 (p<.05 for both). 

Conclusion: Simple measurements and formulas based on OGTT provide accurate and better evaluation of IVGTT-derived indices than more elaborated models in AAM with high disease burden. Further studies in other populations are needed to validate our results.

(1) Aloulou I, Brun JF, Mercier J. Evaluation of insulin sensitivity and glucose effectiveness during a standardized breakfast test: comparison with the minimal model analysis of an intravenous glucose tolerance test. Metabolism. 2006;55:676-690. (2) Matsuda M, DeFronzo RA. Insulin sensitivity indices obtained from oral glucose tolerance testing: comparison with the euglycemic insulin clamp. Diabetes Care. 1999;22:1462-70. (3) Mari A, Pacini G, Murphy E, Ludvik B, Nolan JJ. A Model-Based Method for Assessing Insulin Sensitivity From the Oral Glucose Tolerance Test. Diabetes Care 2001;24:539-548. (4) Retnakaran R, Shen S, Hanley AJ, Vuksan V, Hamilton JK, Zinman B. Hyperbolic relationship between insulin secretion and sensitivity on oral glucose tolerance test. Obesity 2008;16:1901-1907.

Nothing to Disclose: BM, AA, YE, EB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported in part by Merit Review grant from the Department of Veterans Affairs awarded to EB and NIH grant # UL1RR029879 awarded to CCTS at UIC.