Glucagon-like peptide (GLP)-1 and leptin concentrations in obese patients with Type 2 diabetes mellitus.
OBJECTIVE
To assess differences in circulating leptin and glucagon-like peptide (GLP)-1 concentrations before and after an oral glucose load, in euglycaemic and isoinsulinaemic conditions, between obese patients with and without Type 2 diabetes mellitus.


METHODS
Ten male obese (body mass index (BMI) > 30 kg/m2) patients with Type 2 diabetes and 20 matched non-diabetic subjects were studied. Leptin, GLP-1(7-36)amide and GLP-1(7-37) concentrations were measured 0, 30, 60, and 90 min after a 50-g oral glucose load administered 90 min after the beginning of a euglycaemic hyperinsulinaemic clamp.


RESULTS
GLP-1(7-36)amide concentrations before the glucose load were significantly lower in diabetic patients than in controls (median (quartiles): 50.5 (44.7-53.2) vs. 128.7(100-172.5) pg/ml; P < 0.01), while no difference was observed in baseline GLP-1(7-37). In non-diabetic subjects, GLP-1(7-36)amide and GLP-1(7-37) concentrations increased significantly after the oral glucose load, while no glucose-induced increase in GLP-1 concentration was observed in diabetic patients. GLP-1(7-36)amide at 30, 60, and 90 min, and GLP-1(7-37) at 30 min, of the glucose challenge, were significantly lower in diabetic patients. Leptin concentrations were not significantly different in diabetic patients when compared to non-diabetic subjects, and they did not change after the oral glucose load.


CONCLUSIONS
Leptin concentrations are not significantly modified in obese Type 2 diabetic patients. GLP-1(7-36)amide baseline concentrations are reduced in Type 2 diabetes; moreover, diabetic subjects show an impaired response of GLP-1 to oral glucose in euglycaemic, isoinsulinaemic conditions. This impairment, which is not the result of differences in glycaemia or insulinaemia during assessment, could contribute to the pathogenesis of hyperglycaemia in Type 2 diabetes mellitus.
Mannucci
E
E
Department of Clinical Pathophysiology, University of Florence, Firenze, Italy.
Ognibene
A
A
Cremasco
F
F
Bardini
G
G
Mencucci
A
A
Pierazzuoli
E
E
Ciani
S
S
Fanelli
A
A
Messeri
G
G
Rotella
C M
CM
D001786:Blood Glucose / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005934:Glucagon / Q000097:blood*; D052216:Glucagon-Like Peptide 1; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D006946:Hyperinsulinism; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D011498:Protein Precursors / Q000097:blood*
D001786:Blood Glucose; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D006442:Glycated Hemoglobin; D007328:Insulin; D020738:Leptin; D010446:Peptide Fragments; D011498:Protein Precursors