Magnitude of functional adaptation after intestinal resection

Abstract

Intestinal adaptation after resection has been much studied, but rarely examined in an integrative context. Hence we assessed the effects of resection and subsequent adaptation on the quantitative relationship between dietary glucose load and gut capacity to transport glucose. The ratio of capacity to load is termed the “safety factor.” Our objectives were to determine 1) the time course of intestinal adaptation after resection, 2) whether adaptation is quantitatively complete, 3) whether survival requires maintaining a safety factor of at least 1.0 for glucose transport, 4) the effect of altered energy demands on adaptation, and 5) the relationship between the amount of tissue removed and the magnitude of functional adaptation. We performed 80% resection of the small intestine on Sprague-Dawley rats and measured small intestinal glucose uptake capacity, dietary glucose load, and gut gross morphology at 1, 5, and 10 wk postsurgery. Nearly all aspects of adaptation were complete by 1 wk postsurgery. After resection, remnant small intestine mass increased by over fivefold within 1 wk, to reach 50–70% of its preresection value. However, mass-specific glucose uptake activity was reduced, so that intestinal regeneration restored uptake capacity to only 33% of control values. Increased energetic demands had only modest effects on intestinal adaptation. Although the safety factor for small intestinal glucose uptake remained <1.0 (i.e., capacity < load) after adaptation to resection, nearly all rats survived. Hindgut fermentation of nonabsorbed nutrients appeared to contribute to that survival, despite inadequate small intestinal capacity. After less massive resection surgeries (25, 50, and 75% resections), the percent increase in glucose uptake capacity increased with the amount of tissue removed.