Isolated impaired fasting glucose and peripheral insulin sensitivity: not a simple relationship.
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.


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.
Kim
Sun H
SH
Department of Medicine, Stanford University School of Medicine, Stanford, California, USA. sunhkim@stanford.edu
Reaven
Gerald M
GM
D000328:Adult; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D001794:Blood Pressure; D015992:Body Mass Index; D005215:Fasting; D005260:Female; D018149:Glucose Intolerance / Q000097:blood / Q000503:physiopathology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology*; D000078790:Insulin Secretion; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood / Q000503:physiopathology
D001786:Blood Glucose; D007328:Insulin; D008055:Lipids