IRS1 and diabetes mellitus: Treatment with exendin-4, a GLP-1 analog approved for the treatment of diabetes mellitus, reduces Aβ oligomer-induced JNK activation, IRS-1 serine phosphorylation, and impairment of axonal transport, and improves insulin signaling (by increasing IRS-1 tyrosine phosphorylation) in cultured hippocampal neurons and in the brains of 14-month old, male APPswe/PS1ΔE9 mice [74].