Impact of glucose tolerance status, sex, and body size on glucose absorption patterns during OGTTs.
OBJECTIVE
We studied whether patterns of glucose absorption during oral glucose tolerance tests (OGTTs) were abnormal in individuals with impaired glucose regulation and whether they were related to sex and body size (height and fat-free mass). We also examined how well differences in insulin sensitivity and β-cell function measured by gold-standard tests were reflected in the corresponding OGTT-derived estimates.


METHODS
With validated methods, various aspects of glucose absorption were estimated from 12-point, 3-h, 75-g OGTTs in 66 individuals with normal glucose tolerance (NGT), isolated impaired fasting glucose (i-IFG), or isolated impaired glucose tolerance (i-IGT). Insulin sensitivity and β-cell function were measured with the euglycemic-hyperinsulinemic clamp and intravenous glucose tolerance tests, respectively. Surrogate markers of both conditions were calculated from OGTTs.


RESULTS
More rapid glucose absorption (P ≤ 0.036) and reduced late glucose absorption (P ≤ 0.039) were observed in the i-IFG group relative to NGT and i-IGT groups. Women with i-IGT had a lower early glucose absorption than did men with i-IGT (P = 0.041); however, this difference did not persist when differences in body size were taken into account (P > 0.28). Faster glucose absorption was related to higher fasting (P = 0.001) and lower 2-h (P = 0.001) glucose levels and to greater height and fat-free mass (P < 0.001). All OGTT-derived measures of insulin sensitivity, but only one of three measures of β-cell function, reflected the differences for these parameters between those with normal and impaired glucose regulation as measured by gold-standard tests.


CONCLUSIONS
Glucose absorption patterns during an OGTT are significantly related to plasma glucose levels and body size, which should be taken into account when estimating β-cell function from OGTTs in epidemiological studies.
Corresponding author: Kristine Færch, krif@steno.dk.
Kristine
K
Færch
Giovanni
G
Pacini
John J
JJ
Nolan
Torben
T
Hansen
Andrea
A
Tura
Dorte
D
Vistisen
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D049628:Body Size; D005215:Fasting / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D018149:Glucose Intolerance / Q000097:blood / Q000503:physiopathology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000502:physiology; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000503:physiopathology*; D012737:Sex Factors
D001786:Blood Glucose; D007328:Insulin; D005947:Glucose