Hepatic uptake and biliary secretion of bile acids in the perfused rat liver

Metabolism of bile acids in the post-prandial state

The modulation of energy expenditure by dietary administration of cholic acid in mice promoted interest in studying bile acid(s) (BA) as adjuvants in the treatment of metabolic diseases such as obesity and diabetes. Bile acids can modulate intermediary metabolism by acting directly on nuclear as well as G-protein-coupled receptors or indirectly through changes in gut microbiota. Despite the potential of BA to affect intermediary metabolism, plasma kinetics and changes in individual BA in blood in the post-prandial state have been neglected for a long time. Minutes after ingestion of a meal (or a glucose challenge), the plasma BA concentration increases as a result of the secretion of bile into the duodenum, followed by intestinal absorption and a systemic circulation spillover. A large inter-individual variability of post-prandial kinetics of plasma BA is documented. Factors such as gender, diet composition, circadian oscillations, and individual capacities for the synthesis and transport of BA play important roles in determining this variability and are discussed in the present short review in light of new findings.

Tauroursodeoxycholate increases rat liver ursodeoxycholate levels and limits lithocholate formation better than ursodeoxycholate

BACKGROUND & AIMS

To explain the greater hepatoprotective effect of tauroursodeoxycholic acid vs. ursodeoxycholic acid, the absorption, hepatic enrichment, and biotransformation of these bile acids (250 mg/day) were compared in rats.

METHODS

Bile acids were determined in intestinal contents, feces, urine, plasma, and liver by gas chromatography-mass spectrometry.

RESULTS

The concentration of ursodeoxycholate in the liver of animals administered tauroursodeoxycholic acid (175 +/- 29 nmol/g) was greater (P < 0.05) than in animals administered ursodeoxycholic acid (79 +/- 19 nmol/g). Hepatic lithocholate was substantially higher after ursodeoxycholic acid administration (21 +/- 10 nmol/g) than after tauroursodeoxycholic acid administration (12 +/- 1 nmol/g). A concomitant reduction in the proportion of hydrophobic bile acids occurred that was greatest during tauroursodeoxycholic acid administration. In the intestinal tract, the mass of ursodeoxycholate and its specific metabolites was greater in rats administered tauroursodeoxycholic acid (27.2 mg) than those administered ursodeoxycholic acid (13.2 mg). In feces, the proportion of lithocholate was 21.9% +/- 4.9% and 5.4% +/- 4.0% after ursodeoxycholic acid and tauroursodeoxycholic acid administration, respectively.

CONCLUSIONS

Compared with ursodeoxycholic acid, tauroursodeoxycholic acid induces a greater decrease in the percent composition of more hydrophobic bile acids within the pool, limits lithocholate formation, and increases hepatic ursodeoxycholate concentration. These differences are explained by increased hepatic extraction and reduced intestinal biotransformation and not by enhanced absorption of the amidated species.