What is the primary energy source for enterocytes (intestinal epithelial cells)?

Enterocytes' Energy Source

Glutamine is the primary energy source for enterocytes (intestinal epithelial cells). 1

Evidence for Glutamine as Primary Enterocyte Fuel

Glutamine serves as the principal fuel source for intestinal epithelial cells through several mechanisms:

• The ESPEN guidelines specifically identify glutamine as "a primary fuel source for epithelial enterocytes" 1
• Glutamine provides energy substrate to intestinal epithelial cells, regulates intestinal barrier structure and function, and supports intestinal immune function 1
• Studies demonstrate that both acute and prolonged glutamine supplementation enhances nitric oxide production at the intestinal villi microvascular compartment, supporting enterocyte energy metabolism 1

Physiological Mechanisms

Glutamine's role as the primary energy source for enterocytes is supported by several physiological mechanisms:

• Enterocytes preferentially utilize glutamine over other amino acids or glucose for energy production
• Glutamine is metabolized within enterocytes to provide ATP through:
  • Direct oxidation in the mitochondria
  • Conversion to other metabolites that enter the TCA cycle
• Bidirectional supply of glutamine (both luminal and serosal) maintains optimal ATP levels in enterocytes 2

Clinical Implications

The role of glutamine as the primary energy source for enterocytes has important clinical implications:

• Glutamine deprivation leads to:

  • Diminished intestinal function
  • Mucosal atrophy
  • Increased bacterial translocation 3
  • Reduced expression of disaccharidases and Na+/K+-ATPase 3
  • Decreased transepithelial resistance 3

• Glutamine supplementation:

  • Restores enterocyte function
  • Prevents bacterial-induced tissue injury
  • Maintains intestinal barrier integrity 3

Comparison with Other Potential Energy Sources

While other amino acids have been studied:

• Glutamine: Primary energy source for enterocytes 1, 3
• Arginine: Contributes to nitric oxide production but is not the primary energy source 1
• Alanine: Not identified as a significant energy source for enterocytes
• Glycine: Not identified as a significant energy source for enterocytes

Conclusion

Based on the most recent and highest quality evidence, glutamine is definitively the primary energy source for enterocytes. The ESPEN guidelines clearly identify glutamine as "a primary fuel source for epithelial enterocytes" 1, and multiple studies confirm its critical role in maintaining enterocyte energy metabolism, structure, and function.