INS and nicotine dependence: In the GSE4412 group, the KEGG analysis revealed that the differential genes were primarily enriched in “GABAergic synapse,” “Morphine addiction,” “Nicotine addiction,” “Glutamatergic synapse,” “Synaptic vesicle cycle,” “Type I diabetes mellitus,” “Phagosome,” “Insulin secretion,” “Retrograde endocannabinoid signaling,” “Neuroactive ligand-receptor interaction” (Figures 4B,D,F).