BDNF and diabetes mellitus: Based on our summarized findings, we propose a hypothesized diagram Figure 6 that exercise training not only enhanced neural BDNF/TrkB survival signaling (including the MEK/MAPK/ERK, PI3K/AKT, and Bcl2-family prosurvival pathways), but also prevented diabetes-induced neural Fas/FasL-mediated and mitochondria-initiated apoptotic pathways.