title: Effect of aging on glucose homeostasis: accelerated deterioration of beta-cell function in individuals with impaired glucose tolerance.
abstract: OBJECTIVE
  To examine the effect of aging on insulin secretion (first- and second-phase insulin release) and insulin sensitivity in people with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT).
  
  
  METHODS
  First- and second-phase insulin secretion and insulin sensitivity were assessed in hyperglycemic clamp experiments in 266 individuals with NGT and 130 individuals with IGT, ranging in age from approximately 20 to approximately 70 years. Changes in beta-cell function were compared using the disposition index to adjust for differences in insulin sensitivity.
  
  
  RESULTS
  As expected, both phases of insulin release and insulin sensitivity were reduced in individuals with IGT (all P < 0.01). Insulin sensitivity was not independently correlated with age in either group. In people with NGT, the disposition index for first- and second-phase insulin release decreased similarly at a rate of approximately 0.7% per year. In people with IGT, the disposition indexes for first- and second-phase insulin release decreased at greater rates ( approximately 2.2 and 1.4% per year, P = 0.002 and 0.009, respectively, vs. NGT), with the decrease in first phase being greater than that of second phase (P = 0.025).
  
  
  CONCLUSIONS
  Insulin secretion (both first and second phase) normally decreases at a rate of approximately 0.7% per year with aging; this decrease in beta-cell function is accelerated about two-fold in people with impaired glucose tolerance-first phase to a greater extent than second phase. Finally, aging per se has no effect on insulin sensitivity independent of changes in body composition.
authors: Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA.
authors: Ervin
authors: E
authors: Szoke
authors: Muhammad Z
authors: MZ
authors: Shrayyef
authors: Susan
authors: S
authors: Messing
authors: Hans J
authors: HJ
authors: Woerle
authors: Timon W
authors: TW
authors: van Haeften
authors: Christian
authors: C
authors: Meyer
authors: Asimina
authors: A
authors: Mitrakou
authors: Walkyria
authors: W
authors: Pimenta
authors: John E
authors: JE
authors: Gerich
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D005260:Female; D018149:Glucose Intolerance / Q000097:blood* / Q000378:metabolism / Q000503:physiopathology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D007328:Insulin