Mechanistic homeostasis of vitamin D metabolism in the kidney through reciprocal modulation of Cyp27b1 and Cyp24a1 expression.
Level 5 - mechanism / opinion, no new human data
Narrative review of preclinical mechanistic animal studies with no human data.
PubMed 31629064 · doi:10.1016/j.jsbmb.2019.105500
What was done
The authors reviewed findings from mouse genetic and genomic knockout models investigating kidney-specific transcriptional enhancer modules. They examined how enhancers located in the introns of adjacent Mettl1 and Mettl21b genes regulate renal Cyp27b1, how distinct enhancers control Cyp24a1, and how parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), 1,25(OH)2D3, and lipopolysaccharide (LPS) modulate these regulatory regions.
What was found
The abstract describes qualitative mechanistic findings and provides no numerical data. Combined deletion of the M1 and M21 enhancer submodules in mice completely eliminated basal renal Cyp27b1 expression, producing severe skeletal abnormalities, 1,25(OH)2D3 depletion, elevated PTH, and reduced Cyp24a1. In contrast, extrarenal Cyp27b1 expression and its upregulation by LPS remained intact. Dietary normalization of calcium, phosphate, PTH, and FGF23 rescued the skeletal phenotype. Unique enhancers regulating Cyp24a1 expression in response to 1,25(OH)2D3, FGF23, and PTH were also demonstrated.
Why it matters
This review outlines the precise distal genomic enhancers that reciprocally regulate renal vitamin D activation and catabolism, showing how systemic mineral homeostasis is maintained without disrupting local immune regulation of vitamin D.
Limits
The findings are derived entirely from preclinical mouse knockout models without human validation. The abstract reports no quantitative values, sample sizes, or variance metrics.
Cited by
- supports A substantial portion of active vitamin D is synthesized by the kidneys.