Sensitivity of markers of DNA stability and DNA repair activity to folate supplementation in healthy volunteers.

We have previously reported that supplementation with folic acid (1.2 mg day(-1) for 12 week) elicited a significant improvement in the folate status of 61 healthy volunteers. We have examined effects of this supplement on markers of genomic stability. Little is known about the effect of folate supplementation on DNA stability in a cohort, which is not folate deficient. Preintervention, there was a significant inverse association between uracil misincorporation in lymphocyte DNA and red cell folate (P < 0.05). In contrast, there were no associations between folate status and DNA strand breakage, global DNA methylation or DNA base excision repair (measured as the capacity of the lymphocyte extract to repair 8-oxoGua ex vivo). Folate supplementation elicited a significant reduction in uracil misincorporation (P < 0.05), while DNA strand breakage and global DNA methylation remained unchanged. Increasing folate status significantly decreased the base excision repair capacity in those volunteers with the lowest preintervention folate status (P < 0.05). Uracil misincorporation was more sensitive to changes in folate status than other measures of DNA stability and therefore could be considered a specific and functional marker of folate status, which may also be relevant to cancer risk in healthy people.

Downstream effects on human low density lipoprotein of homocysteine exported from endothelial cells in an in vitro system.

A model system is presented using human umbilical vein endothelial cells (HUVECs) to investigate the role of homocysteine (Hcy) in atherosclerosis. HUVECs are shown to export Hcy at a rate determined by the flux through the methionine/Hcy pathway. Additional methionine increases intracellular methionine, decreases intracellular folate, and increases Hcy export, whereas additional folate inhibits export. An inverse relationship exists between intracellular folate and Hcy export. Hcy export may be regulated by intracellular S-adenosyl methionine rather than by Hcy. Human LDLs exposed to HUVECs exporting Hcy undergo time-related lipid oxidation, a process inhibited by the thiol trap dithionitrobenzoate. This is likely to be related to the generation of hydroxyl radicals, which we show are associated with Hcy export. Although Hcy is the major oxidant, cysteine also contributes, as shown by the effect of glutamate. Finally, the LDL oxidized in this system showed a time-dependent increase in uptake by human macrophages, implying an upregulation of the scavenger receptor. These results suggest that continuous export of Hcy from endothelial cells contributes to the generation of extracellular hydroxyl radicals, with associated oxidative modification of LDL and incorporation into macrophages, a key step in atherosclerosis. Factors that regulate intracellular Hcy metabolism modulate these effects.

Reduction in plasma total homocysteine through increasing folate intake in healthy individuals is not associated with changes in measures of antioxidant activity or oxidant damage.

BACKGROUND: Various mechanisms have been proposed to explain the association between plasma total homocysteine (tHcy) and risk of cardiovascular disease, including oxidative activity of homocysteine. OBJECTIVE: To explore the putative role of reactive oxygen species in the association between plasma tHcy and risk of cardiovascular disease in healthy individuals. DESIGN: A double-blind, placebo-controlled crossover intervention to increase folate intake through diet (increased consumption of folate-rich foods) and supplement (400 micro g folic acid) was carried out in 126 healthy men and women. Measurements were made of antioxidant activity in red blood cells and plasma, and products of oxidant damage in plasma. RESULTS: Diet and supplement-based interventions led to an increase in measures of folate status and a reduction in plasma tHcy. This was not associated with any significant change in measures of antioxidant activity (plasma and red blood cell glutathione peroxidase activity and red blood cell superoxide dismutase activity) or oxidant damage (plasma malondialdehyde), although an improvement in plasma total antioxidant capacity just failed to reach significance. CONCLUSIONS: In healthy individuals lowering plasma tHcy does not have any functional implications regarding oxidative damage.

Passive constriction of the upper airway during central apneas: fiberoptic and EMG investigations.

We studied five adult male patients with central sleep apnea syndrome (> 75% of the monitored events being central) during sleep using a fiberoptic scope and EMG monitoring of the superior and middle constrictors of the pharynx and the genioglossus and geniohyoid muscles. The fiberoptic investigation revealed a spontaneous decrease in the size of the airway during central apneas, without negative intrathoracic pressure or activation of the superior and middle pharyngeal constrictor muscles. We found a mean maximum decrease of 71 +/- 7% in the cross-sectional area of the airway and an absence of superior-middle pharyngeal constrictor EMG discharge. We did not observe any complete collapses of the airway.

Amphetamine challenge test, response to treatment, and lateral ventricle size in schizophrenia.

The hypothesis of two independent pathologies in schizophrenia proposed by Crow (1980) were tested. Two dimensions of the dopamine variable, namely, the behavioral response during the Amphetamine Challenge Test (ACT) and the response to neuroleptic treatment, were studied in a cohort of 19 subjects with a research diagnosis of schizophrenia (n = 18) or schizoaffective disorder (n = 1) in an acute inpatient setting. The size of the lateral ventricle was assessed by mesauring the ventricle-brain ratio (VBR) on the computerized tomographic brain scan. Patients who had greater symptom reduction with the neuroleptic treatment worsened more in their positive psychotic symptoms during the ACT. Those with larger VBRs showed less treatment responsiveness and no worsening during the ACT. The findings are supportive of Crow's hypothesis. The ACT has the potential to be an index of both Type I and Type II pathologies.