Interdigestive fluctuations of plasma bile acid concentration: relation to interdigestive motility pattern

Area of Science:

• Gastroenterology
• Digestive Physiology

Background:

• Bile acid delivery to the duodenum is linked to the interdigestive migrating motor complex (MMC) in fasting states.
• Bile acid reabsorption occurs in the ileum after transport through the small intestine.

Purpose of the Study:

• To investigate the relationship between plasma bile acid and motilin concentrations and small intestinal motility in humans.
• To understand the cyclical nature of bile acid transport and absorption in the human digestive system.

Main Methods:

• Manometric recording of antral and upper small bowel motility in 5 human volunteers.
• Serial blood sampling every 10 minutes for radioimmunoassay of motilin and conjugated bile acids.
• Correlation analysis of motor activity, motilin, and bile acid levels throughout the migrating motor complex cycle.

Main Results:

• Motilin levels showed fluctuations that correlated with the migrating motor complex (MMC) cycle.
• Plasma bile acid levels also fluctuated, with peaks occurring around phase 3 activity of the MMC.
• Time lags between bile acid peaks, motilin peaks, and phase 3 activity were minimal, suggesting ileal reabsorption of previously secreted bile acids.

Conclusions:

• Plasma bile acid peaks are likely due to ileal arrival and absorption of bile acids secreted during preceding phase 2 and transported by phase 3 of the MMC.
• Variability in bile acid transport and absorption may explain the poor correlation between individual plasma bile acid and motilin peaks.