Alstonia scholaris (L.) R. Br. ameliorated diabetic nephropathy through PPAR-δ pathway

Alstonia scholaris was utilized as a medicinal herb for the management of diabetes traditionally, with diabetic nephropathy (DN) was one of its major complications. However, the effect of A. scholaris on DN have yet to be explored.

To investigate the effect and mechanism of A. scholaris in treating DN.

The high glucose (HG)-induced renal podocyte (MPC5) injury model was conducted in vitro, and DN mice induced by high fat diet and combined with streptozotocin (HFD + STZ) was employed to evaluate bioactivity in vivo. Transcriptome analysis was conducted to explore the potential targets of vallesamine, with findings further validated by RT-qPCR and WB analysis. Furthermore, the binding affinity of vallesamine to its potential target was investigated through molecular docking and dynamics simulation.

Four major alkaloids of A. scholaris demonstrated significant efficacy in mitigating HG-induced MPC5 cell damage, and they also restored oxidation balance while reducing the release of nitric oxide and lactate dehydrogenase. Oral administration of the total alkaloids and the four compounds for 6 weeks, respectively, could ameliorate proteinuria, urinary protein-to-creatinine ratio, hyperglycemia and hyperlipidemia significantly, and as well elevate serum levels of total protein and albumin concurrently in HFD + STZ induced mice. Moreover, renal injury and matrix hyperplasia were also improved after the treatment. Notably, vallesamine (5 mg/kg) exerted a pronounced effect on DN through upregulating Ppar-δ, Fads2, Me1, Ehhadh, Lpl, Scd1, Acsl1, and downregulating Hmgcs5, Slc27a1, Dbil5 and Plin5 gene expressions of PPAR pathway. Meanwhile, proteins related to lipid metabolism (PPAR-δ and ACSL1, HMGCS2) as well as the associated with renal inflammation (PODOCIN, BCL-2, and IL-6) were regulated by vallesamine intervention. In addition, vallesamine-PPAR-δ complexes maintained structural integrity, with the binding free energy of -25.84 kJ/mol, indicating a particularly high affinity between the ligand and the receptor in molecular dynamics and docking.

Total alkaloids from A. scholaris and its main components vallesamine alleviated kidney injury induced by HFD + STZ through modulation the PPAR-δ pathway, providing a potential strategy for the development of new botanical drug to treat DN.