Abstract
Topographical variations of metabolite concentrations have been reported in the duodenum, jejunum and ileum of the small intestine, and in human intestinal tumours from those regions, but there are no published metabolite concentrations measurements correlated with linear position in the mouse small intestine or intestinal tumours. Since DNA methylation dynamics are influenced by metabolite concentrations, they too could show linear anatomical variation. We measured metabolites by HR-MAS 1H NMR spectroscopy and DNA cytosine modifications by LC/MS, in normal small intestines of C57BL/6J wild-type mice, and in normal and tumour samples from ApcMin/+ mice. Wild-type mouse intestines showed approximately linear, negative concentration gradations from the pylorus (i.e. the junction with the stomach) of alanine, choline compounds, creatine, leucine and valine. ApcMin/+ mouse tumours showed negative choline and valine gradients, but a positive glycine gradient. 5-Hydroxymethylcytosine showed a positive gradient in the tumours. The linear gradients we found along the length of the mouse small intestine and in tumours contrast with previous reports of discrete concentration changes in the duodenum, jejunum and ileum. To our knowledge, this is also the first report of a systematic measurement of global levels of DNA cytosine modification in wild-type and ApcMin/+ mouse small intestine.
Highlights
Several recent studies have shown topographical variations of metabolite concentrations in the intestines of normal humans1, rats[2,3] and m ice[4], and in human tumours arising in different intestinal regions[5]
We performed HR-MAS 1H NMR on biopsies taken along the length of the small intestines from wild-type C57BL/6J mice and ApcMin/+ littermates
HR-MAS 1H NMR is less sensitive than mass spectrometry but it has the advantage that metabolites are assayed in the original sample, with no errors due to extraction, derivatisation or ionisation; the sample is unaffected by the spectroscopic procedure, so the metabolite data can be paired to data from additional analyses
Summary
Several recent studies have shown topographical variations of metabolite concentrations in the intestines of normal humans1, rats[2,3] and m ice[4], and in human tumours arising in different intestinal regions[5] These reports led us to investigate whether mouse intestinal cancer metabolism may depend on the anatomical location of the tumour in the small intestine of the ApcMin/+ mouse, a widely-used model of gut tumorigenesis that spontaneously develops adenomas in the small and large intestines[6] which can be sampled from precise anatomical locations. Because epigenetic changes associate with gene activity[8], cellular proliferation[9,10] and cancer cell m etabolism[11] we measured cytosine methylation and hydroxymethylation in DNA extracted from the tissue biopsies that had been used for the metabolite analysis
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