For the past year, researchers have been puzzled by results from a multicenter study that contradicted the conventional wisdom that hormone replacement therapy protects against heart disease in postmenopausal women (JAMA. 1998;280:605-613). But a new study indicates that the puzzle's solution, in a word, may be methylation.
Researchers at Johns Hopkins University School of Medicine have reported that methylation of genes that direct estrogen receptor production in coronary blood vessels may be implicated in heart disease among women taking replacement estrogen. Methylation blocks the promoter region of genes, halting their function. In an examination of blood vessels and heart tissue removed from patients during coronary bypass surgery or atherectomy, the researchers found that in healthy vessels, 4% to 5% of estrogen receptor genes were methylated, but in clogged vessels, about 11% of the genes were methylated.
Voelker R. Estrogen and Heart Disease. JAMA. 1999;282(12):1121. doi:10.1001/jama.282.12.1121-JQU90007-2-1