Body composition and metabolic changes associated with massive intestinal resection in mice

Background: The specific changes in body composition and metabolism during the adaptation response to massive intestinal loss are presently unclear. The present study was designed to determine alterations in these parameters using an established mouse model. Methods: Male C57/Bl6 mice underwent either 50% small bowel resection (SBR) or transection with reanastomosis (Sham) operation. Oxygen consumption per unit time, carbon dioxide production per unit time, respiratory quotient, and energy expenditure were measured by indirect calorimetry along with body composition determination by nuclear magnetic resonance at postoperative days 1, 3, 7, 14, 21, and 28. Results: The mice that underwent SBR had lower rates of metabolism as measured by decreased energy expenditure, carbon dioxide production per unit time and oxygen consumption per unit time when compared with the Sham group throughout the study period. During adaptation, SBR mice had restoration of body fat at two weeks after the operation while the lean mass and body weight remained lower throughout. Conclusion: Without supplemental parenteral nutrition, the adaptation response to massive SBR is characterized by reduced energy metabolism and an inappropriate replenishment of fat stores over lean mass. Futures studies will be needed to determine the metabolic effects of various growth factors designed to enhance structural features of adaptation.