Features of bile acid metabolism in fish and their biological significance (review)

Bile acids in fish, as in other vertebrates, represent a complex metabolic system the composition of which depends on species, age, diet, and environmental conditions. Their ratio is closely associated with enterohepatic circulation—a continuous cycle of bile acid synthesis, transport, utilization, and reabsorption that maintains their optimal concentration in the body. This process involves the liver, bile ducts, gallbladder, and intestine. Disruptions of enterohepatic circulation caused by impaired bile acid synthesis or reduced intestinal reabsorption may lead to gastrointestinal pathologies in fish manifested by digestive disorders and inflammatory processes, which is especially relevant under intensive aquaculture conditions. The aim of the research was to analyze scientific publications focused on bile acid metabolism in fish and their biological significance, following the methodological recommendations for writing review articles proposed by H. Snyder. The literature analysis revealed that fish exhibit a significantly greater diversity of bile acids compared to other vertebrates. Their metabolism includes the synthesis of primary bile acids from cholesterol in the liver, their subsequent conjugation, participation in lipid emulsification in the intestine, and reabsorption. A portion of bile acids undergoes microbial transformation in the intestine, resulting in the formation of secondary and tertiary bile acids, whose roles are not yet fully understood. A comprehensive understanding of bile acid metabolism in fish is essential for the development of effective strategies for disease prevention, improvement of aquaculture efficiency, and the study of adaptive and evolutionary mechanisms in different fish species.