Specnuezhenide Ameliorates Diabetic Nephropathy in db/db Mice via Nrf2, A20/NF-κB, and Gut Microbiota Regulation

The pathogenesis of diabetic nephropathy (DN) is multifactorial, involving inflammation, oxidative stress, and the gut-kidney axis. Specnuezhenide is the main active component of Ligustri Lucidi Fructus and exhibits antineoplastic, antioxidant, and anti-inflammatory activities. However, the molecular mechanisms underlying its effects on DN need to be further studied. This study, therefore, aims to investigate the molecular mechanisms of Specnuezhenide on DN. A DN mouse model was established using db/db mice, and they were administered Specnuezhenide for 8 weeks. The effects of Specnuezhenide on these mice were assessed through serum glucose and renal function evaluations. Histopathological alterations were evaluated using hematoxylin and eosin staining. An enzyme-linked immunosorbent assay was employed to quantify inflammatory cytokine levels. The Nrf2 pathway and A20/NF-κB pathways were analyzed via western blotting (WB), while the expression of intestinal tight junction proteins was assessed using WB and immunofluorescence. Alterations in the gut microbiota were examined through high-throughput 16S rRNA sequencing. Compared with the model control, Specnuezhenide improved renal function in db/db mice, reducing blood glucose (from 37.13 mmol/L to 28.96 mmol/L), blood urea nitrogen (from 18.27 mmol/L to 15.15 mmol/L), and urinary protein (from 28.5 mg to 20.41 mg) in the high-dose group. Meanwhile, gut microbiota analysis showed increased microbial abundance and decreased lipopolysaccharide levels following Specnuezhenide administration. Meanwhile, Specnuezhenide can upregulate the expression of intestinal tight junction proteins, thereby enhancing the integrity of the intestinal barrier. Specnuezhenide can upregulate the expression of Nrf2 and A20, and downregulate the expression of NF-κB. Furthermore, Specnuezhenide can ameliorate renal functional injury while regulating the Nrf2 and A20/NF-κB pathways.