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Posts Tagged ‘bone mineral density (BMD)’


Larry, H. Bernstein, MD, FCAP, Author and Curator
Http://pharmaceuticalintelligence.com/2013-12-4/larryhbern/Vitamin_D_-_Binding_Protein_and_Vitamin_D_Status

Vitamin D–Binding Protein and Vitamin D Status of Black Americans and White Americans

CE Powe, MK Evans, J Wenger, AB Zonderman, AH Berg, M Nalls, H Tamez, et al.
N Engl J Med 21 Nov,2013; 369:1991-2000
http://dx.doi.org/10.1056/NEJMoa1306357

Summary

BACKGROUND

Low levels of total 25-hydroxyvitamin D are common among black Americans. Vitamin D–binding protein has not been considered in the assessment of vitamin D deficiency.

METHODS

In the Healthy Aging in Neighborhoods of Diversity across the Life Span cohort of blacks and whites (2085 participants), we measured
  • levels of total 25-hydroxyvitamin D,
  • vitamin D–binding protein, and
  • parathyroid hormone as well as
  • bone mineral density (BMD).

We genotyped study participants for two common polymorphisms in the vitamin D–binding protein gene (rs7041 and rs4588). We estimated levels of bioavailable 25-hydroxyvitamin D in homozygous participants. 

RESULTS

Mean (±SE) levels of both total 25-hydroxyvitamin D and vitamin D–binding protein were lower in blacks than in whites (total 25-hydroxyvitamin D, 15.6±0.2 ng per milliliter vs. 25.8±0.4 ng per milliliter, P<0.001; vitamin D–binding protein, 168±3 μg per milliliter vs. 337±5 μg per milliliter, P<0.001).
  • Genetic polymorphisms independently appeared to explain 79.4% and 9.9% of the variation in levels of vitamin D–binding protein and total 25-hydroxyvitamin D, respectively.
  • BMD was higher in blacks than in whites (1.05±0.01 g per square centimeter vs. 0.94±0.01 g per square centimeter, P<0.001).
  • Levels of parathyroid hormone increased with decreasing levels of total or bioavailable 25-hydroxyvitamin D (P<0.001 for both relationships),
    • yet within each quintile of parathyroid hormone concentration, blacks had significantly lower levels of total 25-hydroxyvitamin D than whites.

Among homozygous participants, blacks and whites had similar levels of bioavailable 25-hydroxyvitamin D overall (2.9±0.1 ng per milliliter and 3.1±0.1 ng per milliliter, respectively; P=0.71) and

  • within quintiles of parathyroid hormone concentration.

CONCLUSIONS

Community-dwelling black Americans, as compared with whites, had low levels of total 25-hydroxyvitamin D and vitamin D–binding protein,
  • resulting in similar concentrations of estimated bioavailable 25-hydroxyvitamin D.

Racial differences in the prevalence of common genetic polymorphisms provide a likely explanation for this observation. (Funded by the National Institute on Aging and others.)

 

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