Mercury exposure and a shift toward oxidative stress in avid seafood consumers

Mechanisms of mercury (Hg) toxicity at low doses from seafood consumption, the most common exposure route, are not well understood. We tested the hypothesis that seafood Hg exposure is related to a shift in redox status, indicated by a decrease in the ratio of reduced to oxidized glutathione (GSH:GSSG) in blood, or increase in redox potential (E_h). We also examined whether key seafood nutrients (selenium (Se), omega-3 fatty acids) confound or modify this shift. We measured blood concentrations of total Hg, Se, GSH, GSSG, and the Omega-3 Index (% omega-3s of total fatty acids in red blood cell membranes) in seafood consumers in Long Island, NY. We examined relationships between Hg, GSH:GSSG ratio and E_h. Elevated blood Hg (>5.8μgL^-1) was associated with lower GSH:GSSG (β=-116.73, p=0.01), with no evidence of confounding by Se or Omega-3 Index. However, in models stratified by Omega-3 Index levels, Hg-GSH:GSSG associations were weakened among those with high Omega-3 Index levels (>6% of fatty acids, β=-63.46, p=0.28), and heightened among those with low Omega-3 Index (β=-182.53, p<0.01). We observed comparable patterns for E_h in relation to Hg. These results support the hypothesis that Hg exposure from seafood is linked to a shift in redox status toward oxidative stress, modified by omega-3 fatty acids in this population. Further work should examine the role of different seafood nutrients and Hg-induced shifts in redox status in the diverse health effects associated with elevated Hg exposure.