BDNF and insulin-resistant diabetes mellitus: In db/db mice, an insulin-resistant diabetes model, the reduction in BDNF levels in the hippocampus and the density of dendritic spines on secondary and tertiary dendrites of DG granule neurons could be partially restored by CR, and in wild-type mice, CR showed an additive effect on the elevation of BDNF levels in the hippocampus [172].