The biosynthesis of arginine, unsaturated fatty acids, and amino acids, bile secretion, butanoate metabolism, beta-alanine metabolism, fatty acid degradation, lysine degradation, valine, leucine and isoleucine degradation, as well as the PPAR signaling pathway, may be underlying factors contributing to the onset and progression of diabetic nephropathy DN. The gene discussed is PPARA; the disease is diabetic kidney disease.