Isolated Impaired Fasting Glucose and Peripheral Insulin Sensitivity
Not a simple relationship
- Sun H. Kim, MD, MS and
- Gerald M. Reaven, MD
- Address correspondence and reprint requests to Sun H. Kim, MD, Stanford University Medical Center, 300 Pasteur Dr., Room S025, Stanford, CA 94305-5103. E-mail: sunhkim{at}stanford.edu
Abstract
OBJECTIVE—In a recent consensus statement, the American Diabetes Association (ADA) concluded that individuals with impaired fasting glucose (IFG) have “normal muscle insulin sensitivity.” To subject this conclusion to further validation, we evaluated the relationship between glucose tolerance categories and peripheral insulin sensitivity in a large nondiabetic population.
RESEARCH DESIGN AND METHODS—Insulin sensitivity was directly quantified by determining the steady-state plasma glucose (SSPG) concentration during an insulin suppression test in 446 nondiabetic individuals divided into four groups: normal glucose tolerance (NGT, n = 318), isolated IFG (n = 63), isolated impaired glucose tolerance (IGT, n = 33), and combined IFG and IGT (IFG/IGT, n = 32).
RESULTS—Insulin sensitivity was significantly different in all three groups with pre-diabetes (IFG, IGT, IFG/IGT) as compared with NGT (P < 0.05). Using tertiles of SSPG concentration in the NGT group as operational definitions of insulin resistance (highest tertile) and insulin sensitivity (lowest tertile), there was considerable heterogeneity within the pre-diabetic groups. Thus, 57% of IFG individuals were insulin resistant, and 13% were insulin sensitive. The IFG/IGT group was most homogeneous, with 94% classified as insulin resistant and only 3% as insulin sensitive.
CONCLUSIONS—Peripheral insulin sensitivity varies considerably in nondiabetic individuals, with IFG individuals showing the most heterogeneity within the pre-diabetes group. We believe that this heterogeneity in insulin sensitivity, and the relatively few patients in whom insulin sensitivity has been measured directly in the past, explain the discrepancy between our findings and those of the recent ADA consensus statement.
- ADA, American Diabetes Association
- HOMA-IR, homeostasis model assessment of insulin resistance
- IFG, impaired fasting glucose
- IGT, impaired glucose tolerance
- IST, insulin suppression test
- NGT, normal glucose tolerance
- SSPG, steady-state plasma glucose
Footnotes
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Published ahead of print at http://care.diabetesjournals.org on 13 November 2007. DOI: 10.2337/dc07-1574.
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 November 6, 2007.
- Received August 9, 2007.
- DIABETES CARE
