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ObjectiveTo establish a more accurate and sensitive liquid chromatography-ultraviolet (LC-UV) method for the determination of uric acid in rat serum, and compare the results with those of commercial kits, providing a new method for the accurate determination of uric acid in the rat hyperuricemia model induced by potassium oxonate. Methods A hyperuricemia model was established by intraperitoneal injection of potassium oxonate (300 mg/kg) into SPF-grade male SD rats, and the control group was administered an equal amount of 0.5% sodium carboxymethylcellulose solution. Blood samples were collected from the posterior orbital venous plexus and centrifuged to obtain serum samples. After precipitation with 0.1% trifluoroacetic acid-acetonitrile (containing the internal standard 3,4-dihydroxybenzylamine hydrobromide), the supernatant was injected for analysis. Uric acid was separated on a Waters XBridge HILIC column (150 mm×4.6 mm, 3.5 μm) using acetonitrile (containing 0.5% formic acid and 2 mmol/mL ammonium formate) as the organic phase and methanol solution (methanol∶water=1∶1, containing 0.5% formic acid with 2 mmol/L ammonium formate) as the aqueous phase for isocratic elution and detection at 290 nm. Serum samples treated with activated carbon were used as substitute matrices for the methodological verification. Serum uric acid levels in rats with potassium oxonate-induced hyperuricemia were measured using the established LC-UV method and commercially available kits (uricase and phosphotungstic acid methods), and the accuracies of the three methods were compared. Results Serum uric acid showed a good linear relationship (R>0.999) at mass concentration of 10–200 μg/mL in rats, the lower limit of quantification was 10 μg/mL, the accuracy ranged from -2.17% to 2.21%, the intra-batch precision ranged from 0.52% to 1.95%, the inter-batch precision ranged from 3.04% to 4.90%, and the extraction recovery ranged from 83.12% to 89.91%. In the rat model, the results obtained using the commercially available phosphotungstic acid method kit were significantly higher than those of the LC-UV method, and those obtained using the commercially available uricase method kit were significantly lower than those of the LC-UV method, but the LC-UV method showed the best recovery of the spiked sample (95.90%–99.96%). Conclusion The LC-UV method developed in this study can determine the concentration of uric acid in rat serum with higher accuracy than commercially available kits and is recommended for the determination of serum uric acid in the rat model of hyperuricemia induced by potassium oxonate.

Bile acid homeostasis is crucial for the normal physiological functioning of the liver. Disruptions in bile acid profiles are closely linked to the occurrence of cholestatic liver injury. As part of our diagnostic and therapeutic approach, we aimed to investigate the disturbance in bile acid profiles during cholestasis and its correlation with cholestatic liver injury. Before the occurrence of liver injury, alterations in bile acid profiles were detected in both plasma and liver between 8 and 16 h, persisting up to 96 h. TCA, TCDCA, and TUDCA in the plasma, as well as TCA, TUDCA, TCDCA, TDCA, TLCA, and THDCA in the liver, emerged as early sensitive and potential markers for diagnosing ANIT‐induced cholestasis at 8–16 h. The distinguishing features of ANIT‐induced liver injury were as follows: T‐BAs exceeding G‐BAs and serum biochemical indicators surpassing free bile acids. Notably, plasma T‐BAs, particularly TCA, exhibited higher sensitivity to cholestatic hepatotoxicity compared with serum enzyme activity and liver histopathology. Further investigation revealed that TCA exacerbated ANIT‐induced liver injury by elevating liver function enzyme activity, inflammation, and bile duct proliferation and promoting the migration of bile duct epithelial cell. Nevertheless, no morphological changes or alterations in transaminase activity indicative of liver damage were observed in the rats treated with TCA alone. Additionally, there were no changes in bile acid profiles or inflammatory responses under physiological conditions with maintained bile acid homeostasis. In summary, our findings suggest that taurine‐conjugated bile acids in both plasma and liver, particularly TCA, can serve as early and sensitive markers for predicting intrahepatic cholestatic drugs and can act as potent exacerbators of cholestatic liver injury progression. However, exogenous TCA does not induce liver injury under physiological conditions where bile acid homeostasis is maintained. Maintaining bile acid balance is important for liver health, with cholestatic liver injury often linked to bile acid profile disruptions. We investigated these disturbances and their correlation with liver damage post‐ANIT treatment. The alteration of bile acid profiles in plasma and liver occurred at 8–16 h before injury, persisting for up to 96 h. Certain bile acids emerged as early markers for diagnosing cholestasis. TCA in plasma, especially, showed high sensitivity to ANIT‐induced liver damage, exacerbating its progression. [ABSTRACT FROM AUTHOR]

Bile acids are synthesized from cholesterol in the liver. Dysregulation of bile acid homeostasis, characterized by excessive accumulation in the liver, gallbladder and blood, can lead to hepatocellular damage and the development of cholestatic liver disease. Nuclear receptors play a crucial role in the control of bile acid metabolism by efficiently regulating bile acid synthesis and transport in the liver. Among these receptors, peroxisome proliferator‐activated receptor (PPAR), a ligand‐activated transcription factor belonging to the nuclear hormone receptor superfamily, controls the expression of genes involved in adipogenesis, lipid metabolism, inflammation and glucose homeostasis and has emerged as a potential therapeutic target for the treatment of the metabolic syndrome in the past two decades. Emerging evidence suggests that PPAR activation holds promise as a therapeutic target for cholestatic liver disease, as it affects both bile acid production and transport. This review provides a comprehensive overview of recent advances in elucidating the role of PPAR in the regulation of bile acid metabolism, highlighting the current position of PPAR agonists in the treatment of primary biliary cholangitis. By summarizing the specific regulatory effects of PPAR on bile acids, this review contributes to the exploration of novel therapeutic strategies for cholestatic liver diseases. [ABSTRACT FROM AUTHOR]