Berberine ameliorates renal injury in diabetic C57BL/6 mice: Involvement of suppression of SphK–S1P signaling pathway

Berberine (BBR) was previously found to have beneficial effects on renal injury in experimental diabetic rats. However, the mechanisms underlying the effects are not fully understood. Sphingosine kinase–Sphingosine 1-phosphate (SphK–S1P) signaling pathway has been implicated in the pathogenesis of diabetic nephropathy (DN). The aim of this study was to investigate the effects of BBR on renal injury and the activation of SphK–S1P signaling pathway in alloxan-induced diabetic mice with nephropathy. Alloxan-induced diabetic mice were treated orally with BBR (300 mg/kg/day) or vehicle for 12 weeks. BBR inhibited the increases in fasting blood glucose, kidney/body weight ratio, blood urea nitrogen, serum creatinine and 24-h albuminuria in diabetic mice. It also prevented renal hypertrophy, TGF-β1 synthesis, FN and Col IV accumulation. Moreover, BBR down-regulated the elevated staining, activity and levels of mRNA and protein of SphK1, and S1P production as well. These findings suggest that the inhibitory effect of BBR on the activation of SphK–S1P signaling pathway in diabetic mouse kidney is a novel mechanism by which BBR partly exerts renoprotective effects on DN.