Drug screening assays useful in the discovery of pharmaceutically active compounds for use in the treatment of diseases involving abnormal lipid metabolism including diabetic neuropathy are taught. In particular, the control region of delta-5-desaturase gene is taught as a target for the drug screening methods, which serve to identify nucleotides, proteins, compounds and/or other pharmacological agents, which modulate the activity of desaturase enzymes or regulate the level of expression of the desaturase genes. Cell-based and cell lysate assays are taught for detecting components that interact with the desaturase enzymes and modify fatty acid profiles. In addition, cell-based and cell lysate assays are used to identify functional and regulatory elements controlling expression of the desaturase genes as well as to screen for components that modulate the transcriptional activity of the desaturase genes. Also taught is the gene for rat delta-5-desaturase.