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J Clin Endocrinol Metab. 2011 Jul;96(7):E1092-9. doi: 10.1210/jc.2010-2731. Epub 2011 Apr 20.

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

Author information

  • 1Department of Pediatrics, Georgia Prevention Institute, Georgia Health Sciences University, Augusta, Georgia 30912, USA. npollock@georgiahealth.edu

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.

PMID:
21508147
[PubMed - indexed for MEDLINE]
PMCID:
PMC3135188
Free PMC Article
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