Lower uncarboxylated osteocalcin concentrations in children with prediabetes is associated with beta-cell function.

Academic Article

Abstract

  • CONTEXT: Although animal studies suggest that it is the uncarboxylated rather than carboxylated form of osteocalcin that affects glucose homeostasis, the human data are scant and equivocal. OBJECTIVE: This study investigated associations of uncarboxylated and carboxylated forms of osteocalcin with insulin sensitivity and β-cell function in 140 overweight prepubertal children (43% female, 46% black, 84% obese) with normal glucose levels (n = 99) and prediabetes (n = 41). METHODS: An oral glucose tolerance test was used to identify prediabetes and for measurement of insulin sensitivity (Matsuda index), β-cell function [oral glucose tolerance test derived insulinogenic index and disposition index (DI(OGTT))] and uncarboxylated and carboxylated forms of osteocalcin. Visceral adipose tissue (VAT) was assessed using magnetic resonance imaging. RESULTS: After controlling for age, sex and race, lower uncarboxylated osteocalcin concentrations, Matsuda index, insulinogenic index, and DI(OGTT) and higher VAT levels were found in the prediabetes vs. normal-glucose group (all P < 0.03). Carboxylated osteocalcin levels were not different between groups. Multiple linear regression adjusting for age, sex, race, and VAT revealed that uncarboxylated osteocalcin was associated with insulinogenic index and DI(OGTT) (β = 0.34, 0.36, respectively, both P < 0.04) in the prediabetes group but not the normal-glucose group. In both the normal-glucose and prediabetes groups, carboxylated osteocalcin was associated with insulin sensitivity (β = 0.26, 0.47, respectively, both P < 0.02). CONCLUSIONS: These data suggest that the lower uncarboxylated osteocalcin concentrations found in children with prediabetes may be associated with β-cell dysfunction. In addition, our findings between carboxylated osteocalcin and insulin sensitivity suggest that carboxylated osteocalcin plays a role in human glucose homeostasis.
  • Keywords

  • Blood Glucose, Child, Female, Glucose Tolerance Test, Humans, Insulin Resistance, Insulin-Secreting Cells, Male, Osteocalcin, Prediabetic State
  • Digital Object Identifier (doi)

    Author List

  • Pollock NK; Bernard PJ; Gower BA; Gundberg CM; Wenger K; Misra S; Bassali RW; Davis CL
  • Start Page

  • E1092
  • End Page

  • E1099
  • Volume

  • 96
  • Issue

  • 7