The Antioxidant System of the Elephant Seal during their Natural Prolonged Fast

Elephant seals experience up to three months of absolute food and water deprivation (fasting) as a natural component of their life history. In terrestrial mammals prolonged fasting increases reactive oxygen species production, oxidative damage and inflammation. To test the hypothesis that prolonged fasting in elephant seals does not increase oxidative damage or inflammation, blood and muscle biopsies were collected from early (2–3 wk) and late (7–8 wk) postweaned elephant seals. Muscle and plasma levels of oxidative damage and inflammation markers, red blood cell (RBC) levels of antioxidant enzymes and glutathione (GSH), and muscle activity and protein expression of pro‐oxidant (Nox4) and antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase, glutathione reductase, glutathione‐S transferase, 1‐cys peroxiredoxin and glutamate‐cysteine ligase) were compared between early and late fasting periods. Fasting induced a 2‐fold increase in Nox4 and a 70% increase in NADPH oxidase activity suggesting that prolonged fasting increases pro‐oxidant conditions. However, neither tissue nor systemic indices of oxidative damage or inflammation were increased. Furthermore, muscle and RBC antioxidant enzymes increased 40–60% and GSH content increased 2‐ to 4‐fold suggesting that an increase in the antioxidant system contributes to the prevention oxidative damage and inflammation in prolong‐fasted seals. The present study highlights the importance of antioxidants in mammals during chronic periods of stress to help avoid deleterious systemic consequences. Funded by NHLBI R01‐HL091767.