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Abstract: PO0341

The Vitamin D Metabolite Ratio Is Independent of Vitamin D Binding Protein Concentration

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Ginsberg, Charles, University of California San Diego, La Jolla, California, United States
  • Hoofnagle, Andrew N., University of Washington School of Medicine, Seattle, Washington, United States
  • Katz, Ronit, University of Washington School of Medicine, Seattle, Washington, United States
  • Becker, Jessica Osborn, University of Washington School of Medicine, Seattle, Washington, United States
  • Kritchevsky, Stephen B., Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States
  • Shlipak, Michael, University of California San Francisco, San Francisco, California, United States
  • Sarnak, Mark J., Tufts Medical Center, Boston, Massachusetts, United States
  • Ix, Joachim H., University of California San Diego, La Jolla, California, United States
Background

25-hydroxyvitamin D [25(OH)D] may be a poor marker of vitamin D status due to variability in vitamin D binding protein (VDBP) between individuals and groups. The vitamin D metabolite ratio [VMR, the ratio of 24,25(OH)2D3 to 25(OH)D3] is a marker of vitamin D status that has been hypothesized to be independent of variability in VDBP. This hypothesis has not been directly evaluated.

Methods

We measured 25(OH)D3, 24,25(OH)2D3, 1,25(OH)2D3, and VDBP in 377 community dwelling older adults that participated in the Health Aging and Body Composition Study. 24,25(OH)2D3 and 25(OH)D3 were used to calculate the VMR. We used linear regression to assess the relationship between VDBP with the VMR, 24,25(OH)2D3, 25(OH)D3, and 1,25(OH)2D3.

Results

Study participants had mean age 75+/- 3 years, 52% were female, 40% were black, and 24% had CKD. Lower VDBP concentrations were associated with male sex, lower serum albumin and Gc2/Gc2 VDBP phenotype in multivariable models. In fully adjusted models, each 1% higher VDBP was associated with a 0.92%, 0.76% and 0.57% higher 24,25(OH)2D3, 25(OH)D3, and the 1,25(OH)2D3 (Table 1). The VMR was independent of VDBP concentration, [0.16% (95% CI(-0.11, 0.44)) higher VMR per 1% higher VDBP, p=0.247].

Conclusion

In diverse cohort of community dwelling older adults, the VMR was independent of VDBP concentration whereas VDBP was strongly directly associated with the individual vitamin D metabolite concentrations. The VMR may serve as an important biomarker of vitamin D status and clinical outcomes that can be utilized in populations with a large spectrum of VDBP concentrations

Funding

  • NIDDK Support