Background: Astragalus polysaccharide (APS) is a major bioactive component of the Chinese herb astragalus, with well-established protective effects on the kidney. However, the effect of APS on diabetic nephropathy (DN) is unclear.
Methods: Long non-coding RNA (lncRNA) expression profiles in kidney samples from control, db/db, and APS-treated db/db mice were evaluated using RNA high-throughput sequencing techniques. Additionally, rat renal tubular epithelial (NRK-52E) cells were cultured in high glucose (HG) media. We inhibited the expression of Gm41268 and prolactin receptor (PRLR) by transfecting NRK-52E cells with Gm41268-targeting antisense oligonucleotides and PRLR siRNA.
Results: We found that APS treatment reduced 24-h urinary protein levels and fasting blood glucose and improved glucose intolerance and pathological renal damage in db/db mice. Furthermore, APS treatment enhanced autophagy and alleviated fibrosis in the db/db mice. We identified a novel lncRNA, Gm41268, which was differentially expressed in the three groups, and the cis-regulatory target gene PRLR. APS treatment induced autophagy by reducing p62 and p-mammalian target of rapamycin (mTOR) protein levels and increasing the LC3 II/I ratio. Furthermore, APS alleviated fibrosis by downregulating fibronectin (FN), transforming growth factor-β (TGF-β), and collagen IV levels. In addition, APS reversed the HG-induced overexpression of Gm41268 and PRLR. Reduction of Gm41268 decreased PRLR expression, restored autophagy, and ameliorated renal fibrosis in vitro. Inhibition of PRLR could enhance the protective effect of APS.
Conclusions: In summary, we demonstrated that the therapeutic effect of APS on DN is mediated via the Gm41268/PRLR pathway. This information contributes to the exploration of bioactive constituents in Chinese herbs as potential treatments for DN.
Keywords: Astragalus polysaccharide; LncRNA; autophagy; diabetic nephropathy; prolactin receptor.