To uncover the role of NORAD in the progression of diabetic nephropathy (DN) and the underlying mechanism. Relative levels of NORAD and TLR4 in db/m mice and db/db mice were tested. Meanwhile, their levels in glomerular mesangial cells undergoing high-level (H-MC group) or low-level (L-MC) glucose treatment were determined. Regulatory effects of NORAD and TLR4 on proliferative ability and apoptosis in SV40-MES-13 cells were assessed. The interaction in the regulatory loop NORAD/miR-520h/ TLR4 was verified through dual-luciferase reporter gene assay, determination of subcellular distribution and RIP (RNA Immunoprecipitation) assay. At last, potential role of the regulatory loop NORAD/miR-520h/TLR4 in regulating DN was clarified. NORAD and TLR4 were upregulated in db/db mice and SV40-MES-13 cells in H-MC group. Overexpression of them promoted proliferative ability and inhibited apoptosis in SV40-MES-13 cells. MiR-520h was confirmed to bind NORAD and TLR4. NORAD, miR-520h and TLR4 were mainly distributed in cytoplasm, which were enriched in anti-Agog. The regulatory loop NORAD/miR-520h/TLR4 has been demonstrated to promote the progression of DN. The regulatory loop NORAD/miR-520h/TLR4 promotes the proliferative ability and inhibits apoptosis in glomerular mesangial cells, thus aggravating the progression of DN. (C) 2019 Elsevier Inc. All rights reserved.