Total proteins from cultured DRG neurons were isolated on DIV6 according to published protocols [25 (link), 27 (link)]. Total protein from DRG, sciatic nerve and foot pad tissues of db/db and db/m mice were extracted using the same methods. In vitro samples from 4 individual microfluidic chambers were pooled for one Western blot. The protein concentration was measured using a bicinchoninic acid protein assay kit (Thermo Fisher Scientific). Western blot was performed according to previously described methods [25 (link), 27 (link)]. Briefly, equal amounts of proteins were loaded. Primary antibodies were rabbit anti-ADAM10 (a disintegrin and metalloproteinase domain-containing protein 10, 1:1000, Abcam, Cambridge, UK), rabbit anti-DCX (doublecortin, 1:500, Abcam), rabbit anti-c-MET (tyrosine-protein kinase met, 1:500, Abcam), rabbit anti-FOXP2 (1:1000, Abcam), goat anti-NOTCH1 (1:1000, Santa Cruz), rabbit anti-ROCK1 (Rho associated coiled-coil containing protein kinase 1, 1:500, Abcam), rabbit anti-SYNJ1 (Synaptojanin 1, 1:1000, Sigma-Aldrich), rabbit anti-VAMP2 (vesicle-associated membrane protein 2, 1:1000, Cell Signaling Technology, Danvers, MA, USA), goat anti-VAT1 (1:1000, Santa Cruz), and mouse anti-β-actin (1:10000; Abcam). The optical density of protein bands was measured and calculated by means of Fluorchem E instrument (ProteinSimple, San Jose, CA, USA).