In the downregulated group, several significantly enriched pathways included taurine and hypotaurine metabolism, ascorbate and aldarate metabolism, porphyrin metabolism, PPAR signaling pathway, drug metabolism-cytochrome P450, ribosome, fat digestion and absorption, glycine, serine and threonine metabolism, and cocaine addiction, among others (Figure 1C). The gene discussed is PPARA; the disease is cocaine dependence.