Zishen Qingre Tongluo Formula Improves Renal Fatty Acid Oxidation and Alleviated Fibrosis via the Regulation of the TGF-β1/Smad3 Signaling Pathway in Hyperuricemic Nephrology Rats

Paeonia × suffruticosa Andrews leaf extract and its main component apigenin 7-O-glucoside ameliorate hyperuricemia by inhibiting xanthine oxidase activity and regulating renal urate transporters

BACKGROUND

Hyperuricemia is an important pathological basis of gout and a distinct hazard factor for metabolic syndromes and cardiovascular and chronic renal disease, but lacks safe and effective treatments currently. Paeonia × suffruticosa Andrews leaf effectively reduced serum uric acid in gout patients; however, the material foundation and the mechanism remain unclear.

PURPOSE

To determine the primary active components and mechanism of P. suffruticosa leaf in hyperuricemic mice.

METHODS

The chemical constituents of P. suffruticosa leaf was identified using high-performance liquid chromatographic analysis. The anti-hyperuricemic activity of P. suffruticosa leaf extract (12.5, 25, 50, 100, and 200 mg/kg) and its components was evaluated in hyperuricemic mice induced by a high purine diet for 14 days. Then, the urate-lowering effects of apigenin 7-O-glucoside (0.09, 0.18, and 0.36 mg/kg) were assessed in another hyperuricemic mice model built by administrating potassium oxonate and adenine for 4 weeks. The inhibitory effect of apigenin 7-O-glucoside on uric acid production was elucidated by investigating xanthine oxidase activity in vitro and in serum and the liver and through molecular docking. Immunofluorescence and western blot analyses of the expression of renal urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), organic anion transporters 1 (OAT1), and ATP-binding cassette G member 2 (ABCG2) proteins elucidated how apigenin 7-O-glucoside promoted uric acid excretion.

RESULTS

Six compounds were identified in P. suffruticosa leaf: gallic acid, methyl gallate, oxypaeoniflorin, paeoniflorin, galloylpaeoniflorin, and apigenin 7-O-glucoside. P. suffruticosa leaf extract significantly attenuated increased serum uric acid, creatinine, and xanthine oxidase activity in hyperuricemic mice. Apigenin 7-O-glucoside from P. suffruticosa leaf reduced uric acid, creatinine, and malondialdehyde serum levels, increased superoxide dismutase activity, and partially restored the spleen coefficient in hyperuricemic mice. Apigenin 7-O-glucoside inhibited xanthine oxidase activity in vitro and decreased serum and liver xanthine oxidase activity and liver xanthine oxidase protein expression in hyperuricemic mice. Molecular docking revealed that apigenin 7-O-glucoside bound to xanthine oxidase. Apigenin 7-O-glucoside facilitated uric acid excretion by modulating the renal urate transporters URAT1, GLUT9, OAT1, and ABCG2. Apigenin 7-O-glucoside protected against renal damage and oxidative stress caused by hyperuricemia by reducing serum creatinine, blood urea nitrogen, malondialdehyde, and renal reactive oxygen species levels; increasing serum and renal superoxide dismutase activity; restoring the renal coefficient; and reducing renal pathological injury.

CONCLUSION

Apigenin 7-O-glucoside is the main urate-lowering active component of P. suffruticosa leaf extract in the hyperuricemic mice. It suppressed liver xanthine oxidase activity to decrease uric acid synthesis and modulated renal urate transporters to stimulate uric acid excretion, alleviating kidney damage caused by hyperuricemia.

Advances in energy metabolism in renal fibrosis

Renal fibrosis is a common pathway toward chronic kidney disease (CKD) and is the main pathological predecessor for end-stage renal disease; thus, preventing progressive CKD and renal fibrosis is essential to reducing their consequential morbidity and mortality. Emerging evidence has connected renal fibrosis to metabolic reprogramming; abnormalities in energy metabolism pathways, such as glycolysis, the tricarboxylic acid cycle, and lipid metabolism, are known to cause diseases of diverse etiologies. Cytokine interventions in affected metabolic pathways may significantly reduce the degree of fibrosis, highlighting therapeutic targets for drug development for renal fibrosis. Here, we discuss the relationship between glycolysis, lipid metabolism, mitochondrial and peroxisome dysfunction, and renal fibrosis in detail and propose that targeted therapies for specific metabolic pathways are expected to represent the next generation of treatments for renal fibrosis.