A 13CO2 breath test for liver glycogen oxidation

In conclusion we developed a model to monitor the oxidation of liver glycogen. Our studies showed that it was possible to label the liver glycogen with naturally 13C-enriched carbohydrate and to monitor its oxidation. 13C-enriched muscle glycogen did not interfere with the test within the test conditions. The test design and the tests results were confirmed by using the inverse test set-up in persons who were used to a habitual diet of 13C-enriched carbohydrates. The test was reasonably reproducible within the same persons, though the study group was small. Extending the dietary 13C-enrichment from one to three days did alter the test results. These alterations were small and possibly of no clinical importance. A pilot study showed that the test indeed is capable of detecting differences in glycogen oxidation between cirrhotics and healthy individuals. The clinical application of the test needs further validation by comparing it with other techniques such as the NMR. The studies described in this thesis demonstrate the feasibility of using naturally isotope enriched products for metabolic studies. This breath test is relatively simple to perform as a bedside test and makes use of inexpensive substrates. For a metabolic test to evaluate a complex process, it is reasonably reproducible.