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

Primary Fuel Source for Enterocytes

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

Evidence Supporting Glutamine as Primary Enterocyte Fuel

The evidence strongly supports glutamine as the primary energy source for enterocytes:

• According to the European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines, glutamine serves as the primary energy substrate for intestinal epithelial cells, while also regulating intestinal barrier structure/function and supporting intestinal immune function 1

• Glutamine supplementation has been shown to:

  • Restore enterocyte function
  • Prevent bacterial-induced tissue injury
  • Maintain intestinal barrier integrity
  • Enhance nitric oxide production at the intestinal villi microvascular compartment 1, 2

• The Sports Medicine position statement confirms glutamine's role as "a primary fuel source for epithelial enterocytes" 2

Role of Other Nutrients in Enterocyte Metabolism

While glutamine is the primary fuel source, other nutrients play supporting roles:

• Short-chain fatty acids (SCFAs): While important for colonocytes (cells of the large intestine), SCFAs are not the primary fuel for enterocytes (small intestine cells) 2

• Glucose: While glucose serves as the main metabolic fuel for the brain, peripheral nerves, renal medulla, and certain blood cells, it is not the primary energy source for enterocytes 1

• Triglycerides: Not identified as a significant energy source for enterocytes in any of the guidelines 1

• Lactulose: Functions primarily as a prebiotic and laxative, not as a direct fuel source for enterocytes 1

Physiological Significance

The importance of glutamine for enterocyte function is highlighted by several studies:

• Glutamine deprivation leads to:

  • Reduced expression of digestive enzymes
  • Decreased Na+/K+-ATPase activity
  • Increased bacterial translocation across intestinal barriers
  • Reduced transepithelial resistance 3

• Bidirectional supply of glutamine (both luminal and serosal) has been shown to be most effective in maintaining ATP levels in enterocytes, suggesting the critical importance of this amino acid for intestinal energy metabolism 4

• In clinical contexts, glutamine supplementation has been shown to protect intestinal mucosa, maintain normal intestinal barrier function, reduce bacterial translocation, and enhance intestinal immune function, particularly in critically ill patients such as those with severe burns 5

Therefore, based on the most recent and highest quality evidence, glutamine (option e) is the primary fuel source for enterocytes.