INS and obesity due to melanocortin 4 receptor deficiency: A detailed study by Kobayashi et al. (2009) demonstrated that obesity in ob/ob mice is associated with a significant decrease of cellular GPX activity (GPX1, -4, and -7), as well as increased glutamate-cysteine ligase, catalytic subunit (γ-GCS), whereas inhibition of GPX activity is associated with impaired insulin signaling in 3T3-L1 adipocytes [170].