SOD1 and obesity due to melanocortin 4 receptor deficiency: Regarding antioxidant defense, obesity induction for 14 weeks increased the expression of the antioxidant response transcription factor Nrf2 (Fig 2F), although this was not reflected in increased activity of antioxidant targets, such as superoxide dismutase (SOD) (Fig 2G), catalase (CAT) (Fig 3H) or glutathione peroxidase (GPx) (Fig 2I).