Dietary ratio of protein to carbohydrate induces plastic responses in the gastrointestinal tract of mice |
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Authors: | Allan Sørensen David Mayntz Stephen James Simpson David Raubenheimer |
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Institution: | 1. Department of Ecology and Genetics, University of Aarhus, ?rhus, Denmark 2. Department of Genetics and Biotechnology, Research Centre Foulum, University of Aarhus, ?rhus, Denmark 3. School of Biological Sciences, University of Sydney, Sydney, Australia 4. Institute of Natural Sciences and New Zealand Institute for Advanced Study, Massey University, Albany, New Zealand
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Abstract: | Some vertebrates change the size of their digestive system in response to quantity and fibre content of ingested food, but
the effects of dietary nutrients on gut structure remain poorly understood. Here we investigate how the protein to carbohydrate
ratio of diets affects the mass of the gastrointestinal tract in mice. We fed 6-week-old male mice one of five isocaloric
diets differing only in protein to carbohydrate ratio (the “no-choice” treatments), while a further four treatment groups
received nutritionally complementary food pairings from which they could self-select a diet (the “choice” treatments). After
32 days, we measured the resulting dry mass of stomachs, intestines, caeca and colons. In the no-choice treatments, the stomachs
were heavier in the mice fed diets containing more protein and less carbohydrate, indicating that larger stomachs may be needed
for efficient digestion of the protein-rich food. In contrast, intestines, caeca and colons were heavier when diets contained
more carbohydrates and less protein. This response may function to increase the digestive rate of carbohydrates when the dietary
content of this macronutrient increases, but it may also indicate a compensatory response to increase amino acid uptake from
a protein-deficient food. Mice in the choice treatments self-selected a diet with a protein to carbohydrate ratio of 0.46,
and had gut dimensions similar to the expectation derived from no-choice treatments for this diet composition. Our results
provide an example of plasticity in the differential allocation of resources to organ function, which is triggered by variation
in resource quality. |
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