Risk of Progression to Type 2 Diabetes Based on Relationship Between Postload Plasma Glucose and Fasting Plasma Glucose
- Muhammad A. Abdul-Ghani, MD, PHD1,
- Ken Williams, MS2,
- Ralph DeFronzo, MD1 and
- Michael Stern, MD2
- 1Diabetes Division, University of Texas Health Science Center, San Antonio, Texas
- 2Clinical Epidemiology Unit, University of Texas Health Science Center, San Antonio, Texas
- Address correspondence and reprint requests to Muhammad A. Abdul-Ghani, MD, PhD, Diabetes Division, University of Texas Health Science Center, 7703 Floyd Curl Dr., MS 7886, San Antonio, TX 78229. E-mail: gonzalese1{at}uthscsa.edu
Abstract
OBJECTIVE—We sought to assess the risk of progression to type 2 diabetes in normal glucose tolerance (NGT) subjects based on the relationship between the plasma glucose concentration during oral glucose tolerance tests (OGTTs) and the fasting plasma glucose (FPG) concentration.
RESEARCH DESIGN AND METHODS—Subjects with NGT (n = 1,282) from the San Antonio Heart Study received an OGTT with measurement of the plasma glucose concentration at 0, 30, 60, and 120 min at baseline and after 7–8 years of follow-up. Subjects were divided into four groups based on the relationship between the plasma glucose concentration during the OGTT and the FPG concentration on the same day as the OGTT. Insulin resistance was calculated by the homeostasis model assessment of insulin resistance (HOMA-IR) and Matsuda index. Early-phase insulin secretion was calculated as the ratio between the incremental plasma insulin and glucose concentrations during the first 30 min of the OGTT (ΔI0–30/ΔG0–30). Total insulin secretion was calculated as the ratio between the incremental areas under the insulin and glucose curves during the OGTT [ΔG(AUC)/ΔI(AUC)].
RESULTS—In 23 subjects (group I), the plasma glucose concentration during the OGTT returned to levels below the FPG concentration at 30 min; in 111 subjects (group II) and in 313 subjects (group III), the plasma glucose concentration during the OGTT returned to levels below the FPG concentration at 60 and 120 min, respectively. In the remaining 835 subjects (group IV), the plasma glucose concentration during the OGTT never fell below the FPG concentration. Insulin resistance, measured by HOMA-IR and the Matsuda index, increased progressively from group I through group IV, while insulin secretion measured by ΔI0–30/ΔG0–30 and ΔG(AUC)/ΔI(AUC) decreased progressively from group I through group IV. The incidence of type 2 diabetes was 0% in group I and progressively increased to 0.9% in group II, 3.2% in group III, and 6.4% in group IV.
CONCLUSIONS—Subjects whose postload plasma glucose concentration returned to baseline (i.e., FPG level) more quickly had greater insulin sensitivity, a higher insulinogenic index, and a lower risk of developing type 2 diabetes after 8 years of follow-up compared with subjects whose postload glucose concentration returned to baseline more slowly.
- AUC, area under the curve
- FPG, fasting plasma glucose
- HOMA-IR, homeostasis model assessment of insulin resistance
- IFG, impaired fasting glucose
- IGT, impaired glucose tolerance
- NFG, normal fasting glucose; NGT, normal glucose tolerance
- OGTT, oral glucose tolerance test
Footnotes
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A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C Section 1734 solely to indicate this fact.
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- Accepted April 7, 2006.
- Received September 12, 2005.
- DIABETES CARE
