HbA(1c) diagnostic categories and β-cell function relative to insulin sensitivity in overweight/obese adolescents

Diabetes Care. 2012 Dec;35(12):2559-63. doi: 10.2337/dc12-0747. Epub 2012 Aug 21.

Abstract

Objective: The recommended HbA(1c) diagnostic categories remain controversial and their utility in doubt in pediatrics. We hypothesized that alterations in the pathophysiologic mechanisms of type 2 diabetes may be evident in the American Diabetes Association recommended at-risk/prediabetes category (HbA(1c) 5.7 to <6.5%).

Research design and methods: We compared in vivo hepatic and peripheral insulin sensitivity by [6,6-(2)H(2)] glucose and a 3-h hyperinsulinemic-euglycemic clamp and β-cell function by a 2-h hyperglycemic clamp (∼225 mg/dL) in overweight/obese (BMI ≥85th percentile) adolescents with prediabetes (HbA(1c) 5.7 to <6.5%) (n = 160) to those with normal HbA(1c) (<5.7%) (n = 44). β-Cell function was expressed relative to insulin sensitivity (i.e., the disposition index = insulin sensitivity × first-phase insulin).

Results: In the prediabetes versus normal HbA(1c) category, fasting glucose, insulin, and oral glucose tolerance test (OGTT) area under the curve for glucose and insulin were significantly higher; hepatic and peripheral insulin sensitivity were lower; and β-cell function relative to insulin sensitivity was lower (366 ± 48 vs. 524 ± 25 mg/kg/min; P = 0.005). A total of 27% of youth in the normal HbA(1c) category and 41% in the prediabetes HbA(1c) category had dysglycemia (impaired fasting glucose and/or impaired glucose tolerance) by a 2-h OGTT.

Conclusions: Overweight/obese adolescents with HbA(1c) in the at-risk/prediabetes category demonstrate impaired β-cell function relative to insulin sensitivity, a metabolic marker for heightened risk of type 2 diabetes. Thus, HbA(1c) may be a suitable screening tool in large-scale epidemiological observational and/or interventional studies examining the progression or reversal of type 2 diabetes risk.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Blood Glucose / metabolism
  • Child
  • Female
  • Glucose Clamp Technique
  • Glycated Hemoglobin A / metabolism*
  • Humans
  • Insulin Resistance / physiology*
  • Insulin-Secreting Cells / metabolism*
  • Male
  • Obesity / blood*
  • Obesity / physiopathology*
  • Overweight / blood*
  • Overweight / physiopathology*
  • Young Adult

Substances

  • Blood Glucose
  • Glycated Hemoglobin A