Relationship between GLP-1 levels and dipeptidyl peptidase-4 activity in different glucose tolerance conditions.
OBJECTIVE
The reduced levels of glucagon-like peptide 1 (GLP-1) after an oral glucose load in Type 2 diabetic patients could be dependent either on a reduced synthesis or an increased degradation; but GLP-1 and dipeptidyl peptidase IV (DPP-IV) levels during an oral glucose tolerance test (OGTT) have not been studied together. The aim of the present study was to investigate GLP-1 and DPP-IV levels during an OGTT in patients with different degrees of glucose tolerance.


METHODS
Fifty six subjects (34 female, 22 male) matched for sex, age, body mass index (BMI) and waist circumference underwent a 75 g oral glucose tolerance test. Twenty-eight had normal glucose tolerance, 15 had impaired glucose tolerance and 13 had Type 2 diabetes mellitus. GLP-1 assay was performed with an ELISA kit, and DPP-IV assay using a colorimetric method.


RESULTS
At 30 min GLP-1 levels were significantly lower in subjects with impaired glucose tolerance and type 2 diabetes mellitus compared to those with normal glucose tolerance. The area under the GLP-1 curve was significantly different among the three groups; there was a significant decrease between subjects with normal and impaired glucose tolerance(P = 0.004) and between those with normal glucose tolerance and type 2 diabetes mellitus. (P < 0.001), while the area under the curve for DPP-IV showed no significant difference between the groups.


CONCLUSIONS
These results suggest that an increase of GLP-1 degradation does not play a role in the early stages of diabetes mellitus.
Pala
L
L
Section of Endocrinology, Department of Clinical Pathophysiology, University of Florence, Florence, Italy.
Ciani
S
S
Dicembrini
I
I
Bardini
G
G
Cresci
B
B
Pezzatini
A
A
Giannini
S
S
Mannucci
E
E
Rotella
C M
CM
D000368:Aged; D019540:Area Under Curve; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D005215:Fasting / Q000378:metabolism; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D008297:Male; D008875:Middle Aged; D055105:Waist Circumference
D052216:Glucagon-Like Peptide 1; D018819:Dipeptidyl Peptidase 4