Background Evidence that a vegetarian diet rich in antioxidants contributes to cardiovascular health are growing, however, the underlying molecular mechanisms remain unknown. HO-1 (heme-oxygenase-1), a marker of adaptive response, is protective against oxidative stress and has shown cardioprotective effects. Therefore, we evaluated circulating HO-1 levels and the effect of plasma from omnivorous and vegetarians in endothelial cells (human umbilical vein endothelial cells) on modulating NRF2 (nuclear factor erythroid 2-like 2)/HO-1 and nitric oxide production. Methods and Results From 745 participants initially recruited, 44 omnivorous and 44 vegetarian men matched by age and absence of cardiovascular risk factors and diseases were included in this study. Circulating HO-1 was measured using ELISA and human umbilical vein endothelial cells were incubated with plasma from omnivorous and vegetarians. Higher circulating HO-1 concentrations were found in omnivorous compared with vegetarians. Plasma from omnivorous and not from vegetarians induced NRF2/HO-1 and nitric oxide production in human umbilical vein endothelial cells, and increased reactive oxygen species production and caspase activity after incubation with stressor stimulus. Conclusions We suggest that HO-1 induction in omnivorous may indicate a pro-oxidative status since HO-1 is activated under oxidative stress a state not seen in vegetarians.
Keywords: antioxidant; diet; vascular endothelium.