Two types of studies were performed – an in vitro human cell study and a prospective clinical trial.
The in vitro study involved incubating human coronary artery endothelial cells with different doses of different selenium compounds, including sodium selenite, Se-methylselenocysteine hydrochloride, and seleno-L-methionine. The first two types of selenium were associated with increases in GPx-1 protein activity in a dose-dependent manner.
In the human study, 465 patients with CAD were randomly assigned to receive daily sodium selenite supplements (200 and 500 micrograms) or placebo for 12 weeks. While the higher dose was associated with an increase in the GPx-1 activity during the first half of the study, as well as higher selenium levels in the blood, both doses led to a plateau of GPx-1 activity after 12 weeks.
No effects on endothelial function were observed.
"Our in vitro and in vivo findings consistently demonstrate that sodium selenite supplementation induces an increase in the activity of GPx-1, a selenoprotein prominent in antioxidant defense and cardiovascular protection," wrote the researchers.
"These data should spur further investigations to elucidate whether enhanced GPx-1 activity achieved by selenium supplementation has a protective role in cardiovascular disease during long-term follow-up,” they concluded.
Source: American Heart Journal
December 2008, Volume 156, Issue 6, Pages 1201.e1-1201.e11
"Selenium supplementation improves antioxidant capacity in vitro and in vivo in patients with coronary artery disease: The SElenium Therapy in Coronary Artery disease Patients (SETCAP) Study" Authors: R. Schnabel, E. Lubos, C.M. Messow, C.R. Sinning, T. Zeller, P.S. Wild, D. Peetz, D.E. Handy, T. Munzel, J. Loscalzo, K.J. Lackner, S. Blankenberg