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Hypergravity modulates vitamin D receptor target gene mRNA expression in mice
Michiyasu Ishizawa1, Ken-Ichi Iwasaki, Shigeaki Kato
1Division of Biochemistry, Dept. of Biomedical Sciences, Nihon Univ. School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan.
Summary
Long-term space travel poses risks to calcium metabolism. Hypergravity exposure alters vitamin D gene expression, impacting calcium homeostasis. Mice showed changes in Cyp24a1 and Cyp27b1, suggesting direct effects on vitamin D metabolism.
Area of Science:
- Space biology
- Nutritional science
- Physiology
Background:
- Long-term space travel can disrupt calcium metabolism.
- Vitamin D is crucial for maintaining calcium homeostasis.
- Understanding how altered gravity affects vitamin D metabolism is vital for astronaut health.
Purpose of the Study:
- To investigate the effects of hypergravity on genes involved in vitamin D and calcium metabolism.
- To determine if hypergravity directly influences vitamin D metabolic gene expression.
- To assess potential adaptations to hypergravity stress.
Main Methods:
- Exposure of ICR mice to 2G hypergravity for 2 and 14 days.
- Analysis of mRNA expression for renal Cyp24a1 and Cyp27b1.
- Measurement of plasma 1alpha,25-dihydroxyvitamin D(3) levels.
- Treatment with 1alpha-hydroxyvitamin D(3) and assessment of VDR target genes.
- Examination of VDR-null mice under hypergravity conditions.
Main Results:
- Hypergravity increased renal Cyp24a1 and decreased Cyp27b1 expression in ICR mice.
- These changes were independent of starvation-induced gene expression.
- Plasma 1alpha,25-dihydroxyvitamin D(3) levels decreased under hypergravity.
- 1alpha-hydroxyvitamin D(3) treatment increased intestinal Cyp24a1 expression.
- Hypergravity-induced gene expression changes diminished after 14 days, suggesting adaptation.
- Similar effects on Cyp24a1 were observed in C57BL/6J mice.
- VDR-null mice showed decreased renal Cyp27b1 expression under hypergravity.
Conclusions:
- Hypergravity directly alters the expression of key genes in vitamin D metabolism.
- These alterations can lead to reduced active vitamin D levels.
- Mice may adapt to prolonged hypergravity stress.
- Vitamin D receptor signaling is involved in hypergravity's effects on vitamin D metabolism.
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