Comparative analysis of bile acid composition and metabolism in the liver of Bufo gargarizans aquatic larvae and terrestrial adults

Bile acids are crucial for lipid metabolism and their composition and metabolism differ among species. However, there have been no data on the differences in the composition and metabolism of bile acids between aquatic larvae and terrestrial adults of amphibians. This study explored the differences in composition and metabolism of bile acid between Bufo gargarizans larvae and adults. The results demonstrated that adult liver had a lower total bile acid level and a higher conjugated/total bile acid ratio than larval liver. Meanwhile, histological analysis revealed that the larvae showed a larger cross-sectional area of bile canaliculi lumen compared with the adults. The transcriptomic analysis showed that B. gargarizans larvae synthesized bile acids through both the alternative and the 24-hydroxylase pathway, while adults only synthesized bile acids through the 24-hydroxylase pathway. Moreover, bile acid regulator-related genes FXR and RXRα were highly expressed in adult, whereas genes involved in bile acid synthesis (CYP27A1 and CYP46A1) were highly expressed in larvae. The present study will provide valuable insights into understanding metabolic disorders and exploring novel bile acid-based therapeutics.