Differential Incorporation of 13C Label from Dietary Glucose into Neutral Sugars of Rat Intestine Macromolecules

Using gas chromatography-isotope ratio mass spectrometry, the detection, with a good reproducibility and in a single step, of the 13C content of glycoprotein neutral sugars, glycogen glucose, and ribonucleic acid ribose allowed us to trace incorporation into intestinal macromolecules of sugars derived from dietary glucose, labeled either naturally (as corn starch) or artificially. The 13C enrichment of glycoprotein neutral sugars was strong and rapid and plateaued up to the end of the experiment, whereas the 13C content of ribose increased linearly with time. By contrast, with artificially enriched dietary glucose, no significant 13C enrichment was detected in glycogen, suggesting that this macromolecule does not directly derive from dietary glucose. These results suggest differential control of sugars involved in the synthesis of intestinal macromolecules and demonstrate that this technique would be sensitive and reliable enough to be applied in man for serum glycoprotein sugar determinations.