Hyperhomocysteinemia Evoked by Folate Depletion

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Abstract
High circulating concentrations of homocysteine (ie, hyperhomocysteinemia [Hhcy]) impair the vascular function of peripheral conduit arteries and arterioles perfusing splanchnic and skeletal muscle regions. The effects of HHcy on coronary resistance vessel function and other indexes of vascular function, ie, arterial permeability and stiffening, are unclear. We tested the hypotheses that HHcy impairs coronary resistance vessel reactivity; increases carotid arterial permeability; and initiates arterial stiffening. Male rats that consumed folate-replete (CON, n=44) or folate-deplete (HHcy, n=48) chow for 4 to 5 weeks had total plasma homocysteine concentrations of 7±2 or 58±4 μmol/L, respectively. Maximal acetylcholine-evoked relaxation (≈40% vs ≈60%) and tension development from baseline in response to nitric oxide synthase inhibition (≈20% vs ≈40%) were lower (both P P P P <0.05) in arterial tissue from HHcy versus CON rats. These findings suggest that moderately severe HHcy evoked by folate-depletion impairs endothelium-dependent relaxation of coronary resistance vessels, increases carotid arterial permeability, and initiates arterial stiffening. HHcy may produce these effects by a mechanism associated with increased oxidative and glycoxidative stress.