Cited by 1,933Vitamin D Research StudiesParathyroid Disorders and TreatmentsVitamin K Research Studies

Vitamin D metabolism, mechanism of action, and clinical applications

Open access
Bikle, Daniel D.·2014·Chemistry & Biology

Abstract

Vitamin D3 is made in the skin from 7-dehydrocholesterol under the influence of UV light. Vitamin D2 (ergocalciferol) is derived from the plant sterol ergosterol. Vitamin D is metabolized first to 25 hydroxyvitamin D (25OHD), then to the hormonal form 1,25-dihydroxyvitamin D (1,25(OH)2D). CYP2R1 is the most important 25-hydroxylase; CYP27B1 is the key 1-hydroxylase. Both 25OHD and 1,25(OH)2D are catabolized by CYP24A1. 1,25(OH)2D is the ligand for the vitamin D receptor (VDR), a transcription factor, binding to sites in the DNA called vitamin D response elements (VDREs). There are thousands of these binding sites regulating hundreds of genes in a cell-specific fashion. VDR-regulated transcription is dependent on comodulators, the profile of which is also cell specific. Analogs of 1,25(OH)2D are being developed to target specific diseases with minimal side effects. This review will examine these different aspects of vitamin D metabolism, mechanism of action, and clinical application.

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Crossref · 10.1016/j.chembiol.2013.12.016

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131 of 131 references verified0 citation errors · 0 not checkable

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  • Vitamin D3 is modified through mitochondria in liver and kidney to assume its active form, 1,25 vitamin D.

    “Vitamin D3 is modified through the mitochondria in the liver and kidney to assume its active form, 1,25 vitamin D (Bikle, 2014).”

    From Comprehensive Multi-omics Analysis Reveals Mitochondrial Stress as a Central Biological Hub for Spaceflight Impact (2020) · cites this paper as Bikle, 2014

    The Summary and Conclusions and the 1α-hydroxylase section describe conversion of vitamin D to active 1,25(OH)2D, with the kidney the main source of its circulating form. The 25-hydroxylase section reports mitochondrial activity in the liver, but identifies the most important hepatic enzyme, CYP2R1, in the microsomal fraction. Thus the claim overstates that conversion proceeds through mitochondria in both organs. Page numbers were not supplied. (LLM, conf=0.87)

    Experimental — accuracy not yet measured
  • Supplementation effects depend strongly on baseline vitamin D status, assay standardization, dose, formulation, adherence, and population context.

    “supplementation effects depend strongly on baseline status, assay standardization, dose, formulation, adherence, and population context [1,2,3,4,5,6].”

    From Vitamin D Supplementation, Total Testosterone, and Androgen Bioavailability Markers in Adult Men: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (2026) · cites this paper as [2]

    In Vitamin D Production (page unavailable), Bikle reports that D2 and D3 supplementation produce different 25OHD levels unless D2 is given daily. Clinical Applications > The Skeleton (page unavailable) reports a dose-response relationship for fracture prevention. The paper also discusses differences in vitamin D measurement and clinical contexts, but these passages do not establish that supplementation effects depend strongly on baseline status, assay standardization, or adherence. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • 3-Epi-1α,25(OH)2D3 generally has lower biological activity than 1α,25(OH)2D3.

    “3-Epi-1α,25(OH)2D3 generally has reduced biological activity compared to 1α,25(OH)2D3 [14, 73–75] and is discussed further in Sections 2.1.3 and 3.6.”
  • Many other tissues express CYP27B1, which can modulate local 1α,25(OH)2D levels using plasma 25(OH)D as substrate.

    “Many other tissues express CYP27B1 too which can modulate the local level of this hormone utilizing plasma 25(OH)D as substrate [10, 14, 51].”
  • Serum 1α,25(OH)2D3 and 1α,25(OH)2D2 are produced in the kidney by CYP27B1 acting on circulating 25(OH)D.

    “Serum 1α,25(OH)2D3 and 1α,25(OH)2D2 are produced in the kidney by the action of CYP27B1 on 25(OH)D obtained from the circulation [14].”

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Authors
Bikle, D. D.
Affiliations
San Francisco VA Medical Center (US)
Corresponding author
Bikle, Daniel D.
Venue
Chemistry & Biology
Publisher
Elsevier BV
Published
2014-03
Volume
21
Issue
3
Pages
319-329
ISSN
1074-5521 (ISSN-L)
OpenAlex
W1976776496
Cited by
1,933
References
133
Citations by year
2026: 148 · 2025: 189 · 2024: 196 · 2023: 272 · 2022: 219 · 2021: 211 · 2020: 228 · 2019: 142 · 2018: 135 · 2017: 84 · 2016: 60 · 2015: 37 · 2014: 10 · 2013: 1
FWCI
9.02
Type
journal article
Language
en
Open access
Locations
  • Chemistry & Biology (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • U.S. Department of Defense
  • National Institutes of Health (AR050023)
  • National Cancer Institute (CA110338)
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases (R01AR038386, R01AR050023, P01AR039448)
  • National Center for Research Resources (P41RR001614)
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Vitamin D Research Studies
  • Health Sciences › Medicine › Nephrology › Parathyroid Disorders and Treatments
  • Health Sciences › Nursing › Nutrition and Dietetics › Vitamin K Research Studies
Keywords
vitamin D metabolism, vitamin D3, vitamin D2, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, CYP2R1, CYP27B1, CYP24A1, vitamin D receptor, vitamin D response element, transcriptional regulation, vitamin D analogs, 7-dehydrocholesterol, ergosterol
MeSH terms
Cytochrome P-450 Enzyme System, DNA, Humans, Immune System, Metabolic Diseases, Neoplasms, Vitamin D, Receptors, Calcitriol, Response Elements

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