Developing a model for estimating the activity of colonic microbes after intestinal surgeries

Area of Science:

• Gastroenterology
• Microbiology
• Mathematical Modeling

Background:

• The large intestine plays a crucial role in energy recovery, especially after surgical interventions affecting nutrient absorption in the upper gastrointestinal tract.
• The contribution of colonic microorganisms to energy recovery following small intestine resection requires further quantification.

Purpose of the Study:

• To develop a mathematical model quantifying nutrient absorption and energy recovery in the upper and lower gastrointestinal tracts.
• To assess the compensatory role of the colon's microbial activity after small intestine resection.

Main Methods:

• A two-step mathematical model was developed to link nutrient absorption in the small and large intestines.
• Model parameters were derived using least-squares regression analysis on clinical data from individuals with normal physiology and those post-small intestine resection.
• The model describes the impact of small intestine resection on ileocecal output and subsequent energy recovery by colonic microbes via short-chain fatty acid (SCFA) production.

Main Results:

• The model accurately predicted metabolizable energy in subjects with intact intestines, aligning with Atwater coefficients.
• Small intestine resection led to decreased physiological absorption efficiency and reduced metabolizable energy.
• Colonic microorganisms compensated for energy loss by producing SCFAs from proteins and carbohydrates, recovering over half of the gross energy intake in cases of complete small intestine removal.
• Microbe-derived SCFAs became the predominant form of absorbed energy post-resection.

Conclusions:

• The developed mathematical model offers a valuable framework for understanding the impact of clinical interventions on colonic microorganisms.
• This model can aid in quantifying the compensatory energy recovery role of the large intestine in patients with altered gastrointestinal anatomy.