title: Longitudinal decline of β-cell function: comparison of a direct method vs a fasting surrogate measure: the Insulin Resistance Atherosclerosis Study.
abstract: BACKGROUND
  β-Cell function (BCF) declines over the course of type 2 diabetes, but little is known about BCF changes across glucose tolerance status (GTS) categories, and comparisons of direct vs surrogate measures.
  
  
  OBJECTIVE
  To assess longitudinal changes in BCF across GTS.
  
  
  METHODS
  The Insulin Resistance Atherosclerosis Study is a multicenter, observational, epidemiologic study.
  
  
  METHODS
  Four clinical centers in the US that could identify subjects likely to have impaired fasting glucose (IFG) or impaired glucose tolerance (IGT).
  
  
  METHODS
  We compared longitudinal changes in BCF in 1052 subjects over 5 years. Subjects were categorized according to baseline GTS: normal glucose tolerance (NGT: n = 547), impaired fasting glucose or impaired glucose tolerance (IFG/IGT: n = 341), and newly diagnosed type 2 diabetes (n = 164).
  
  
  METHODS
  None.
  
  
  METHODS
  BCF was assessed from a frequently sampled iv glucose tolerance test (AIR, acute insulin response), and the homeostasis model assessment of BCF (HOMA B).
  
  
  RESULTS
  NGT and IFG/IGT subjects increased their insulin secretion over time, whereas those with type 2 diabetes experienced either decline or little change in BCF. After adjustment for demographic variables and change in insulin resistance, change in HOMA B underestimated the magnitude of changes in BCF, as assessed by change in AIR. Relative to NGT, the 5-year change in insulin secretion in IFG/IGT and type 2 diabetes was 31% and 70% lower (by HOMA B) and 50% and 80% lower (by AIR).
  
  
  CONCLUSIONS
  The decline in BCF over time in IFG/IGT and type 2 diabetes may be more pronounced than previously estimated; HOMA B may underestimate this decline significantly.
authors.affiliation: PhD, University of Toronto, 150 College Street, Room 341, Toronto, ON, M5S 3E2. anthony.hanley@utoronto.ca.
authors.forename: A
authors.initials: A
authors.lastname: Festa
authors.forename: S M
authors.initials: SM
authors.lastname: Haffner
authors.forename: L E
authors.initials: LE
authors.lastname: Wagenknecht
authors.forename: C
authors.initials: C
authors.lastname: Lorenzo
authors.forename: A J G
authors.initials: AJ
authors.lastname: Hanley
mesh_terms: D000328:Adult; D000368:Aged; D050197:Atherosclerosis / Q000503:physiopathology; D001786:Blood Glucose; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D005215:Fasting / Q000502:physiology; D005260:Female; D018149:Glucose Intolerance / Q000503:physiopathology*; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000503:physiopathology*
chemical_list: D001786:Blood Glucose