Dietary cystine restriction increases the proliferative capacity of the small intestine of mice
Cysteine is a semi-essential amino acid provided by dietary intake of mainly meat, eggs and whole grains or via the amino acid methionine. The majority of dietary cystine is absorbed in the small intestine and can be used for protein synthesis or converted to taurine and glutathione. Since there is a trend towards adopting a vegetarian/vegan diet, which is low in cysteine, in this study, we investigate the effect of dietary cystine restriction on intestinal epithelial layer function. Mice (8/group) received a normal diet or a diet low in cystine for 2 weeks. We observed no changes in plasma methionine, cysteine, taurine or glutathione levels after 2 weeks. Stem cell markers as well as the proliferation marker Ki67 were or tended to be increased upon cystine restriction. Gene set enrichment analysis reveals enrichment of Wnt signaling in the small intestine of mice on the low cystine diet. These proliferative effects were not observed in the colon, and are thus specific for the small intestine. In the colon, we observed that dietary cystine restriction results in an increase in the number of goblet cells but no significant changes in the thickness of the mucus barrier or in its protective capacity. There was no difference in the microbiome between the normal and low cystine diet. Overall, we cannot conclude if dietary cystine restriction is beneficial, since increased proliferation and goblet cells can indicate a potential for damage repair, nevertheless hyperproliferation has the potential to induce cancer as well. Overall design: To identify whether dietary cystine restriction would induce differences in gene expression in small intestine, RNA was isolated from tissue and send for sequencing. 3 mice for low cysteine and 4 mice for ctrl/normal cysteine were used.