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What is Metabolic bone disease is caused by excess intake of which vitamin? and explain in detail?
Metabolic bone disease is caused by excess intake of vitamin -A.Retinoic acid has a role in the regulation of gene expression and differentiation of tissues. All-trans-retinoic acid and 9-cis retinoic acid act like steroid hormones. They bind to nuclear receptors; retinoic acid along with the receptor binds to the response elements of DNA. Retinoic acid receptors (RAR) bind all-trans-retinoic acid, while retinoic x receptors (RXR) bind to 9-cis-retinoic acid. RXRs form dimers with vitamin D-receptor also. This explains why deficiency of vitamin A impairs vitamin D function; when there is lack of 9-cis-retinoic acid to receptor dimers, vitamin D function is not optimal.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 382,383