Islet amyloid polypeptide response to maximal hyperglycemia and arginine is altered in impaired glucose tolerance and type 2 diabetes mellitus.
OBJECTIVE
Pancreatic islet amyloid deposition is a characteristic feature of type 2 diabetes mellitus (T2DM). Islet amyloid polypeptide (IAPP) is co-secreted with insulin, but its secretion profile and relationship to insulin and C-peptide in response to glucose and non-glucose stimuli has not been clearly defined.


METHODS
Forty subjects (13 NGT, 12 IGT and 15 T2DM) participated in an OGTT and two-step hyperglycemic (225 and 400 mg/dl) clamp (80 min/step) followed by an IV arginine bolus. Acute insulin (AIR), C-peptide (ACPR) and IAPP (AIAR) responses during each hyperglycemic step and following arginine (AIRArg) were assessed.


RESULTS
AIR and ACPR during both hyperglycemic steps and after arginine progressively decreased from NGT to IGT to T2DM. Fasting IAPP concentrations were higher in T2DM compared to NGT and IGT subjects. The acute IAPP0-10was markedly decreased only in T2DM, while the acute IAPP80-90response during the second step (80-160 min) of hyperglycemic clamp and in response to arginine was markedly impaired in both IGT and T2DM. The ratio of IAPP/C-peptide during the first (225 mg/dl) and second step (400 mg/dl), and in response to arginine, was decreased in T2DM versus both NGT and IGT (p < 0.01). The acute IAPP0-10correlated with ACPR0-10(r = 0.665, p < 0.001) and AIR0-10(r = 0.543, p < 0.001).


CONCLUSIONS
Basal IAPP secretion is higher in T2DM and IGT versus NGT but is reduced in response to hyperglycemia and arginine. The IAPP/C-peptide ratio is reduced with prolonged and more severe hyperglycemia in T2DM individuals.


BACKGROUND
NCT00845182.
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.|Division of Health Sciences, Department of Medicine and Nutrition, University of Guanajuato, Guanajuato, Mexico.|Departamento de Investigación, Hospital Regional de Alta Especialidad del Bajío, Guanajuato, Mexico.
Rodolfo
R
Guardado-Mendoza
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.
Alberto O
AO
Chávez
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.|Division of Health Sciences, Department of Medicine and Nutrition, University of Guanajuato, Guanajuato, Mexico.|Departamento de Investigación, Hospital Regional de Alta Especialidad del Bajío, Guanajuato, Mexico.
Lilia M
LM
Jiménez-Ceja
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.
Andrea
A
Hansis-Diarte
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.|Audie L Murphy VA Hospital, South Texas Veteran Health Care System, San Antonio, TX, USA.
Ralph A
RA
DeFronzo
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA.
Franco
F
Folli
Diabetes Division, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, 78229, TX, USA. tripathy@uthscsa.edu.|Audie L Murphy VA Hospital, South Texas Veteran Health Care System, San Antonio, TX, USA. tripathy@uthscsa.edu.
Devjit
D
Tripathy
D000328:Adult; D001120:Arginine / Q000494:pharmacology*; D002096:C-Peptide / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005260:Female; D015309:Glucose Clamp Technique; D018149:Glucose Intolerance / Q000097:blood*; D005951:Glucose Tolerance Test; D006801:Humans; D006943:Hyperglycemia / Q000097:blood*; D007328:Insulin / Q000097:blood; D058228:Islet Amyloid Polypeptide / Q000097:blood*; D008297:Male; D008875:Middle Aged
D002096:C-Peptide; D007328:Insulin; D058228:Islet Amyloid Polypeptide; D001120:Arginine
Amylin; Hyperglycemic clamp; Insulin secretion