Threshold for effects of vitamin D deficiency on glucose metabolism in obese female African-American adolescents

J Clin Endocrinol Metab. 2009 Sep;94(9):3200-6. doi: 10.1210/jc.2009-0445. Epub 2009 Jun 23.

Abstract

Context: Vitamin D status can influence insulin resistance.

Objective: The aim of the study was to determine the prevalence of vitamin D deficiency in obese African-American (AA) adolescent females in a southeastern latitude and to determine the relationship of 25-hydroxyvitamin D [25(OH)D] with insulin and glucose dynamics.

Design: We conducted a cross-sectional study in a University Children's Hospital.

Methods: Serum 25(OH)D, fasting glucose, PTH, serum calcium, serum lipids, serum transaminases, and C-reactive protein were assessed. Indices of insulin sensitivity and resistance were determined from an oral glucose tolerance test. Subjects were classified as vitamin D deficient or sufficient, based on the traditional vitamin D deficiency definition [serum 25(OH)D <20 ng/ml] and also by a lower 25(OH)D cut-point of 15 ng/ml or less.

Results: A total of 51 AA adolescent females (body mass index, 43.3 +/- 9.9 kg/m(2); age, 14 +/- 2 yr) were studied. Serum 25(OH)D concentrations were 20 ng/ml or less in 78.4% and 15 ng/ml or less in 60.8% of subjects. There were no significant group differences in the metabolic outcomes when subjects were classified using the traditional vitamin D deficiency definition. The Matsuda index of insulin sensitivity was significantly lower (P = 0.02), and insulin area under the curve was significantly higher (P = 0.04) in subjects with 25(OH)D concentrations of 15 ng/ml or less vs. those with higher concentrations.

Conclusions: Vitamin D deficiency is highly prevalent in obese, AA female adolescents and may promote insulin resistance. Our data suggest that a 25(OH)D concentration of 15 ng/ml or less may be the threshold by which vitamin D deficiency confers negative effects on insulin sensitivity.

Publication types

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

MeSH terms

  • Adolescent
  • African Americans*
  • Area Under Curve
  • Child
  • Cross-Sectional Studies
  • Female
  • Glucose / metabolism*
  • Humans
  • Insulin Resistance
  • Obesity / metabolism*
  • Parathyroid Hormone / blood
  • Vitamin D / analogs & derivatives
  • Vitamin D / blood
  • Vitamin D Deficiency / metabolism*

Substances

  • Parathyroid Hormone
  • Vitamin D
  • 25-hydroxyvitamin D
  • Glucose