Fig. (5).

Role of insulin in neuroprotection. Insulin helps in halting Aβ degradation by increasing neprilysin secretion and expression of insulin-degrading enzyme in astrocytes via the activation of the ERK-mediated pathway. However, impaired Biliverdin reductase-A, increased mTOR activity, and Aβ accumulation in the brain result in impaired insulin regulation and downregulation of plasma membrane insulin receptors, respectively. Insulin resistance and impaired insulin regulation also result in overactivation of GSK-3β, which ultimately takes part in the hyperphosphorylation of tau protein and generation of NFTs. (A higher resolution / colour version of this figure is available in the electronic copy of the article).