31.2 Thursday, Jan. 5 Mice increase reliance on paracellular intestinal absorption in response to increased energy demand PRICE, E.R.*; RUFF, L.; GUERRA, A.; KARASOV, W.H.; University of Wisconsin - Madison; University of Wisconsin - Madison; University of Wisconsin - Madison; University of Wisconsin - Madison email@example.com
Intestinal absorption of nutrients has traditionally been thought of as a primarily active (transcellular) process, with the passive (paracellular) pathway playing only a minor role. However, recent studies of birds and bats demonstrate high passive absorption of nutrients, indicating that some species make use of this mode of absorption extensively. We hypothesized that a species with low paracellular absorption (mice) could increase absorption transiently in response to increased energy demand. Specifically, we predicted that mice exposed to cold would increase intestinal size to meet the increased thermogenic energy demand, but in the short term these mice would increase paracellular absorption as a stopgap measure before gut size can be increased. We transferred mice from 21 to 5 °C and assessed paracellular absorption of radiolabeled L-arabinose at 3 timepoints: prior to cold exposure; after 1 day of cold exposure; and after 2 weeks in the cold. Mean gut size increased over the 2 week exposure, and this was accompanied by an increase in food consumption. Absorption of an L-arabinose dose nearly doubled from 16.7% (prior to exposure) to 30.1% after 1 day in the cold, and dropped to 18.7% after 2 weeks exposure. These results suggest that mice can adjust tight junction “leakiness” to meet short-term absorptive capacity needs. Supported by NSF Award 1025886.