title: Cross-sectional and longitudinal changes of glucose effectiveness in relation to glucose tolerance: the insulin resistance atherosclerosis study.
abstract: OBJECTIVE
  Glucose effectiveness (S(G)), the capacity of glucose to enhance its own disposition, is an independent predictor of future diabetes. However, there are data on cross-sectional and longitudinal changes of S(G) and its components, basal insulin effect on S(G) (BIE) and S(G) at zero insulin (GEZI), but the natural course of S(G) has not been described in a large population.
  
  
  METHODS
  S(G) was measured at baseline in 1,265 participants (aged 40-69 years) and at the 5-year examination in 827 participants in the Insulin Resistance Atherosclerosis Study (IRAS) using the frequently sampled intravenous glucose tolerance test. None of these participants were treated with glucose-lowering agents.
  
  
  RESULTS
  In cross-sectional analyses, S(G), BIE, and GEZI deteriorated with worsening of glucose tolerance (P < 0.001 for all three associations). In longitudinal analyses among subjects with normal glucose tolerance (NGT) at baseline, S(G), BIE, and GEZI declined in those who progressed to impaired glucose tolerance (IGT) or diabetes (P < 0.001 for all three measures). More modest longitudinal changes were demonstrated in individuals with IGT. The transition back to NGT (as opposed to no change) compared with the transition to diabetes was statistically significant for S(G) (P = 0.049) and BIE (P = 0.042) and was not a statistically significant trend for GEZI (P = 0.332). In individuals with diabetes, only BIE had a significant decline (P = 0.003).
  
  
  CONCLUSIONS
  S(G), BIE, and GEZI decline in subjects whose glycemic status worsens. S(G) and GEZI deteriorate more in the initial stages of the disease process.
authors.affiliation: Division of Clinical Epidemiology, University of Texas Health Science Center, San Antonio, TX, USA. lorenzo@uthscsa.edu
authors.forename: Carlos
authors.initials: C
authors.lastname: Lorenzo
authors.forename: Lynne E
authors.initials: LE
authors.lastname: Wagenknecht
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Karter
authors.forename: Anthony J G
authors.initials: AJ
authors.lastname: Hanley
authors.forename: Marian J
authors.initials: MJ
authors.lastname: Rewers
authors.forename: Steven M
authors.initials: SM
authors.lastname: Haffner
mesh_terms: D000328:Adult; D000368:Aged; D050197:Atherosclerosis / Q000097:blood* / Q000503:physiopathology; D001786:Blood Glucose / Q000378:metabolism*; D003430:Cross-Sectional Studies; D005215:Fasting / Q000097:blood; D005260:Female; D018149:Glucose Intolerance / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D007328:Insulin