title: Elevated plasma glucose-dependent insulinotropic polypeptide associates with hyperinsulinemia in metabolic syndrome.
abstract: OBJECTIVE
  Metabolic syndrome (MS) is a high-risk condition for type 2 diabetes, a disease characterized by insulin resistance and insulin secretion abnormalities. Insulin resistance has been widely characterized in MS subjects while insulin secretion has been poorly investigated. The present study was hence undertaken to further investigate the α and β cell function and entero-insular axis in this pre-diabetic condition.
  
  
  METHODS
  Using 120' oral glucose tolerance test (OGTT, 75  g) and 60' intravenous glucose tolerance test (IVGTT, 0.3  g/kg), we studied α and β cell function, insulin resistance, and incretin levels in 96 subjects with normal fasting glucose and normal glucose tolerance to OGTT, with (MS+, n=29) and without MS (MS-, n=67).
  
  
  RESULTS
  MS+ individuals showed in comparison with MS-: higher insulinogenic index (IG30) and higher area under the curve (AUC) (0-120) for glucose and insulin during the OGTT, P<0.05; higher AUC (0-10) for glucose (P<0.05) but similar first phase insulin secretion (P=NS) as measured by ΔAIRG and AUC (0-10) for insulin during the IVGTT; increased AUC (0-60) for insulin during the IVGTT (P=0.04); higher GIP levels at 30' (P=0.03), 60' (P=0.01), 90' (P=0.003), and 120' (P=0.004); higher AUC (0-120) for GIP (P=0.007); similar AUC (0-120) for GLP-1 during the OGTT; and delayed glucagon suppression after the OGTT.
  
  
  CONCLUSIONS
  NGT subjects with MS showed increased GIP secretion that could be responsible for the delayed glucagon suppression during the OGTT, thereby suggesting a role for incretins in regulating glucose homeostasis in this condition.
authors.affiliation: Department of Clinical and Molecular Biomedicine, University of Catania, Ospedale Garibaldi Nesima, Via Palermo 636, 95122 Catania, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Calanna
authors.forename: Francesca
authors.initials: F
authors.lastname: Urbano
authors.forename: Salvatore
authors.initials: S
authors.lastname: Piro
authors.forename: Rose Maria
authors.initials: RM
authors.lastname: Zagami
authors.forename: Antonino
authors.initials: A
authors.lastname: Di Pino
authors.forename: Luisa
authors.initials: L
authors.lastname: Spadaro
authors.forename: Francesco
authors.initials: F
authors.lastname: Purrello
authors.forename: Agata Maria
authors.initials: AM
authors.lastname: Rabuazzo
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000502:physiology*; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000097:blood* / Q000502:physiology; D005951:Glucose Tolerance Test; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood* / Q000453:epidemiology*; D007328:Insulin / Q000097:blood; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000453:epidemiology*; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide