['To study whether rosiglitazone prevents the development of diabetic nephropathy through reduction of reactive oxygen species and its downstream signal transduction pathways.', 'The rats were intraperitoneally injected with streptozotocin to induce diabetes, meanwhile the rats in the therapeutic groups were given rosiglitazone (5 or 20 mg/kg/day) for 4 weeks by intragastric administration. Blood glucose, serum lipid and creatinine, urinary albumin excretion were measured. Malondialdehyde content, the activities of nuclear factor-kappaB (NF-kappaB), antioxidant enzymes including Cu-Zn SOD and GSH-Px in kidney were also measured. In addition, the mRNA and protein expression of MCP-1 were semiquantitatively determined with PT-PCR and immunohistochemical staining respectively.', 'No significant difference of blood glucose and lipid were found between diabetic rats and rosiglitazone treatment groups. The renal histopathology was improved significantly. The expressions of MCP-1 mRNA and protein, malondialdehyde level and the activity of NF-kappaB were decreased markedly in rats treated with high-dose rosiglitazone, but the activities of renal Cu-Zn SOD and GSH-Px increased significantly.'] Does rosiglitazone ameliorate diabetic nephropathy by inhibiting reactive oxygen species and its downstream-signaling pathways?