GCG and Alzheimer disease: To further improve the efficacy of transplantation followed by AD cure, these stem cells were genetically modified to encode neurotrophic factor genes [76,77,78,79] or pretreated with neurotrophic factors [76] insulin-like growth factor-I (IGF-I) [77], Vascular Endothelial Growth Factor (VEGF) [78], or Glucagon-Like Peptide-1 (GLP-1) [79].