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Editorial |
Department of Cell Biology, FF4-07, The Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, Fax (216) 445-5480, E-mail jacobsd@cesmtp.ccf.org
The etiology and clinical significance of hyperhomocysteinemia are under intense investigation. Although non-genetic (1) and genetic (2)(3)(4) factors influence plasma homocysteine concentrations, the etiology of moderate to intermediate hyperhomocysteinemia (1550 µmol/L), commonly found in patients with coronary artery disease, cerebrovascular disease, peripheral vascular disease, and in patients with end-stage renal disease, is often unclear. The causes are likely to be multifactorial, involving both acquired and genetic components. There is strong evidence that hyperhomocysteinemia is an independent risk factor for cardiovascular disease (1)(5)(6)(7), but there are conflicting reports as well (8)(9)(10). Some individuals cannot afford to wait the several years it may take before definitive results are available from intervention studies. These include patients with end-stage renal disease, renal transplant recipients, and heart transplant recipients. Immediate treatment of their hyperhomocysteinemia may be more prudent.
Homocysteine is an easily modifiable risk factor that responds well to
benign intervention strategies using water-soluble B complex vitamins
(11)(12)(13). It is derived from methionine in a three-step
pathway (14). Homocysteine may be cytotoxic, and low
intracellular steady-state concentrations are maintained by
remethylation back to methionine (to complete the cycle), conversion to
cystathionine in the transsulfuration pathway, and export to the
circulation. The transsulfuration pathway appears to be highly
organ-specific (14), and the betaine-dependent remethylation
pathway is found only in the liver and kidneys (15
Footnotes
References
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