β-Cell Function and Insulin Sensitivity in Normal Glucose-Tolerant Subjects Stratified by 1-Hour Plasma Glucose Values

Abstract

Aim: This study was designed to assess b-cell function and insulin sensitivity indices among normal glucose tolerance (NGT) subjects stratified by 1-h plasma glucose (1hPG) values during an oral glucose tolerance test (OGTT). Materials and Methods: One hundred sixty-six NGT subjects underwent a five-point OGTT, and glucose and insulin levels were estimated. We calculated the following indices: (a) b-cell function (homeostasis assessment model—b-cell function [HOMA-b] and Insulinogenic Index [IGI]) and (b) insulin sensitivity (homeostasis assessment model—insulin resistance [HOMA-IR], Matsuda Index, and Insulin Sensitivity Index [ISI]). Results: NGT subgroups with elevated 1hPG values (i.e., 1hPG ‡143 to <155 mg/dL and 1hPG ‡155 mg/dL)did not differ from those with 1hPG <143 mg/dL by HOMA-b (P = 0.236) but had significantly lower IGIs (367 – 239 vs. 257 – 243 vs. 246 – 239; P = 0.019). With respect to ISIs, HOMA-IR was not significantly different among the groups (P = 0.103). However, the Matsuda Index (11.2 – 5.0 vs. 7.4 – 4.8 vs. 5.5 – 4.9; P < 0.001) and ISI (0.015 – 0.010 vs. 0.012 – 0.006 vs. 0.011 – 0.011; P = 0.028) were significantly lower in subjects with elevated 1hPG values. Conclusions: NGT subjects with elevated 1hPG levels have alterations in b-cell function and insulin sensitivity compared with those with normal 1hPG levels.