Corticoadrenal activity in rat regulates betaine-homocysteine S-methyltransferase expression with opposite effects in liver and kidney.
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Date
2012-03
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Abstract
Betaine-homocysteine S-methyltransferase (BHMT) is an enzyme that converts homocysteine (Hcy) to methionine
using betaine as a methyl donor. Betaine also acts as osmolyte in kidney medulla, protecting cells from high
extracellular osmolarity. Hepatic BHMT expression is regulated by salt intake. Hormones, particularly corticosteroids,
also regulate BHMT expression in rat liver. We investigated to know whether the corticoadrenal activity
plays a role in kidney BHMT expression. BHMT activity in rat kidneys is several orders of magnitude lower than in
rat livers and only restricted to the renal cortex. This study confirms that corticosteroids stimulate BHMT activity in
the liver and, for the first time in an animal model, also up-regulate the BHMT gene expression. Besides, unlike the
liver, corticosteroids in rat kidney down-regulate BHMT expression and activity. Given that the classical effect of
adrenocortical activity on the kidney is associated with sodium and water re-absorption by the distal tubule leading to
volume expansion, by promoting lesser use of betaine as a methyl donor, corticosteroids would preserve betaine for
its other role as osmoprotectant against changes in the extracellular osmotic conditions. We conclude that
corticosteroids are, at least in part, responsible for the inhibition of BHMT expression and activity in rat kidneys.
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Keywords
Betaine, homocysteine, methylation, osmolyte
Citation
Fridman Osvaldo, Morales AnalÃa V, Bortoni Laura E, Turk-Noceto Paula C, Prieto Elio A. Corticoadrenal activity in rat regulates betaine-homocysteine S-methyltransferase expression with opposite effects in liver and kidney. Journal of Biosciences. 2012 Mar; 37 (1): 115-123.