Can microbial bile acid deconjugation and low biliary phospholipid availability reduce mixed micelle formation and impair triglyceride handling?

Efficient lipid absorption relies on the seamless assembly of mixed micelles to solubilize dietary fats. When this process is disrupted, it triggers a cascade of mucosal irritation and malabsorption.

Mechanistic pathways of micellar disruption

• Bile Acid Deconjugation: Bacterial species expressing bile salt hydrolase (BSH) deconjugate bile salts into free bile acids. These unconjugated forms have altered amphipathic properties, reducing their detergent effectiveness and directly preventing mixed micelle assembly.
• Phospholipid Depletion: Insufficient biliary phosphatidylcholine depletes the essential structural components required to emulsify and solubilize lipids within the intestinal lumen.
• Impaired Micelle Assembly: The combination of deconjugated bile acids and phospholipid deficiency prevents mixed micelle formation, directly causing triglyceride malabsorption.

Pathophysiological feedback loops

• Mucosal Damage: Free, deconjugated bile acids act as direct mucosal irritants that damage enterocytes and alter host immune gene expression, driving mucosal inflammation.
• Enterocyte Dysfunction: Inflammation degrades enterocyte membrane function and barrier integrity, compromising the cellular machinery needed for triglyceride uptake.
• Self-Reinforcing Loop: Unabsorbed luminal lipids accumulate and undergo bacterial fermentation or hydroxylation. This increases mucosal irritation and inflammation, further impairing the gut's lipid-handling capacity.

Bottom line

• Bacterial bile acid deconjugation and depleted biliary phospholipids cooperatively disrupt mixed micelle assembly. This drives triglyceride malabsorption and generates cytotoxic free bile acids, establishing a self-reinforcing cycle of mucosal inflammation and chronic lipid malabsorption.