Normal Glucose Tolerance with a High 1-Hour Postload Plasma Glucose Level Exhibits Decreased β-Cell Function Similar to Impaired Glucose Tolerance.
BACKGROUND
Subjects with normal glucose tolerance (NGT) who have a high 1-hour postload plasma glucose level (≥155 mg/dL; NGT 1 hour-high) have been shown to be at higher risk for type 2 diabetes than subjects with NGT 1 hour-low postload plasma glucose level (<155 mg/dL). We compared β-cell function in subjects with NGT 1 hour-high, NGT 1 hour-low, and impaired glucose tolerance (IGT).


METHODS
We classified subjects into NGT 1 hour-low (n=149), NGT 1 hour-high (n=43), and IGT (n=52). The β-cell function was assessed based on insulinogenic index (IGI), oral disposition index (DI), and insulin secretion-sensitivity index-2 (ISSI-2).


RESULTS
Insulin sensitivity was comparable between the subjects with NGT 1 hour-high and NGT 1 hour-low. The β-cell function with/without adjusting insulin sensitivity was significantly different among the three groups. The IGI (pmol/mmol) was 116.8±107.3 vs. 64.8±47.8 vs. 65.8±80.6 (P=0.141), oral DI was 3.5±4.2 vs. 1.8±1.4 vs. 1.8±3.1 (P<0.001), and ISSI-2 was 301.2±113.7 vs. 213.2±67.3 vs. 172.5±87.5 (P<0.001) in NGT 1 hour-low, NGT 1 hour-high, and IGT, respectively. Post hoc analyses revealed that oral DI and ISSI-2 were significantly different between NGT 1 hour-low and NGT 1 hour-high but comparable between NGT 1 hour-high and IGT.


CONCLUSIONS
Among Korean subjects with NGT, those who have a higher 1-hour postload glucose level have a compromised insulin-sensitivity adjusted β-cell function to a similar degree as IGT subjects.
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Tae Jung
TJ
Oh
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Se Hee
SH
Min
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Chang Ho
CH
Ahn
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Eun Ky
EK
Kim
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Soo Heon
SH
Kwak
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Hye Seung
HS
Jung
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Kyong Soo
KS
Park
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Young Min
YM
Cho
Impaired glucose tolerance; Normal glucose tolerance; Oral glucose tolerance test; β-Cell function