Interplay between Elevated Bile Acids and Reduced Vitamin D Levels in Fontan Circulation: A Double-Edged Sword

Area of Science:

• Cardiology
• Endocrinology
• Hepatology

Background:

• The Fontan procedure for single-ventricle congenital heart disease causes multisystem complications.
• Altered bile acid metabolism and low vitamin D3 are common in these patients.
• A potential harmful relationship exists between bile acids and vitamin D3.

Purpose of the Study:

• To examine the interplay between bile acids and vitamin D3 in Fontan-associated complications.
• To explore the therapeutic relevance of targeting this relationship.

Main Methods:

• Literature review of studies on bile acid metabolism and vitamin D in Fontan patients.
• Analysis of the bidirectional relationship and its impact on organ systems.

Main Results:

• Altered bile acid metabolism, linked to liver disease and gut dysbiosis, increases secondary bile acids.
• Elevated bile acids impair cardiovascular, hepatic, musculoskeletal, and immune functions.
• Bile acid accumulation hinders vitamin D absorption and metabolism, while vitamin D deficiency worsens inflammation and fibrosis.

Conclusions:

• A vicious cycle between dysregulated bile acid and vitamin D pathways contributes to multisystem dysfunction after the Fontan procedure.
• Targeting this axis with vitamin D supplementation or bile acid modulation may mitigate organ injury.
• Interventions offer potential for improved long-term outcomes in high-risk Fontan patients.