OBJECTIVE: To investigate whether linagliptin improves diabetic kidney disease (DKD) by promoting mitochondrial biosynthesis activating adenosine monophosphate activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1/mitochondrial transcription factor A (AMPK/PGC-1/TFAM) pathway. METHODS: With 6 male SD rats feeding normal chow as the control group, 16 SD rat models of DKD induced by intraperitoneal injection of 45 mg/kg STZ and high-fat and high-glucose feeding for 4 weeks were randomized into DKD model group and linagliptin treatment group. The rats in the latter two groups were subjected to daily intragastric administration of vehicle or 5 mg/kg linagliptin (dissolved in 5 g/L sodium carboxymethylcellulose, final concentration of 2 mg/mL) for 12 weeks with further high-fat and high-glucose feeding. After the treatments, the rats were sacrificed and blood samples from the abdominal aorta and kidney tissues were collected for testing blood glucose, liver function and lipid metabolism; HE, PAS, Masson, Sirius red staining and electron microscopy were used to observe renal tissue damage. Renal expressions of transforming growth factor β1 (TGF-β1), fibronectin (FN) and collagen I (Col I) were detected by immunohistochemistry, and the changes in membrane potential (ΔψM) and ATP enzyme content were analyzed to assess mitochondrial damage; The expressions of AMPK/PGC-1/TFAM pathway proteins were detected using Western blotting. RESULTS: Compared with DKD model rats, the rats receiving linagliptin treatment showed significantly decreased blood glucose level ( < 0.01) and improved proteinuria ( < 0.05) with obviously alleviated renal ultrastructural damage and fibrosis, increased ATPase content and ΔψM ( < 0.0001), and enhanced renal expressions of P-AMPK/AMPK, PGC-1 and TFAM ( < 0.05). CONCLUSIONS: Linagliptin improves proteinuria and renal fibrosis in rat models of DKD possibly by activating the AMPK/PGC-1/TFAM pathway to promote mitochondrial biosynthesis.