Acute methionine loading does not alter arterial stiffness in humans

Hyperhomocystinemia is a risk factor for cardiovascular disease, and acute elevation of plasma homocysteine after methionine loading impairs endotheli al function in healthy subjects. Interestingly, pretreatment with vitamin C can ameliorate this effect. We have already shown that acute oral vitamin C administration reduces arterial stiffness in healthy subjects, and the ai m of the present study was to investigate the effect of methionine loading on arterial stiffness with and without concomitant vitamin C using the noni nvasive technique of pulse wave analysis. Eight healthy male subjects (mean age, 29 years; range, 2032 years) were studied on three occasions at weekl y intervals. In a double-blind, double-dummy, randomized order they receive d orally either 100 mg/kg methionine, 100 mg/kg methionine plus 2 g of vita min C, or matching placebos. Peripheral and central blood pressure, heart r ate-cardiac index, arterial stiffness, and plasma homocysteine levels were assessed at baseline and 6 hours after dosing. Compared with placebo, there was no significant change in any of the hemodynamic parameters, including arterial stiffness, after oral methionine, although plasma homocysteine did in crease from 11.5 +/- 1.6 to 28.7 +/- 4.4 muM (mean +/- SEM; p < 0.001). Combined methionine and vitamin C led to a similar increase in plasma homo cysteine but significantly reduced augmentation index by 10.5 <plus/minus> 3.2% (p = 0.02). Acute hyperhomocystinemia does not significantly alter art erial stiffness, as assessed by pulse wave analysis, whereas a combination of methionine and vitamin C leads to a similar reduction in augmentation in dex to that previously described after vitamin C alone. These data reinforc e evidence that vitamin C reduces arterial stiffness but do not indicate an y important interaction with oral methionine.