Metformin also enhances neurogenesis, upregulating Dcx and Ki67 transcription in the hippocampus from AlCl3-induced AD mice [173], and upregulates neurotrophic factors CREB (cAMP-response element binding protein), BDNF and glial cell line-derived neurotrophic factor in scopolamine-induced AD rats [177, 178]. Here, GDNF is linked to Alzheimer disease.