American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the primary fuel for small bowel enterocytes?

1. Glucose

2. Fructose

3. Glutamine

4. Lactate

The correct answer is: Glutamine

The primary fuel for small bowel enterocytes is glutamine. This amino acid plays a crucial role in the metabolism of enterocytes, which are the cells lining the small intestine. Glutamine is absorbed from dietary proteins and is particularly important during periods of stress, injury, or illness when the demand for enterocyte energy increases. Enterocytes utilize glutamine for several vital functions. It serves as a key substrate in the synthesis of nucleotides and proteins, which are essential for cell proliferation and repair. Additionally, glutamine contributes to maintaining the integrity of the intestinal barrier, as it influences tight junction formation and the growth of intestinal mucosal cells. While glucose is a significant source of energy for many cells in the body, particularly in the context of the gastrointestinal tract, enterocytes predominantly rely on glutamine as their primary fuel source for optimal function, especially under conditions of metabolic stress. Other substrates like fructose and lactate may be used under specific circumstances, but they do not serve as the main energy source for the small intestine's enterocytes like glutamine does.