There are so many papers relevant to stable isotope researches, and yet increase all the more. In this article, we describe separation and concentration techniques of stable isotope, application of 13C-labeled compounds in the biosynthesis of vitamin B12 researches from the 1970s to the present, and the development of 13C-urea breath test as 13C-medical application.
We introduced our studies on the possible clinical use of 13C-phynylalanine breath test and 13C-tryptophan breath test in psychiatric disorders. By the phenylalanine test, we detected decreased metabolism of phenylalanine in patients with schizophrenia. In the tryptophan test, on the other hand, we obtained evidence supporting the enhanced metabolism of the tryptophan-kynurenine pathway in patients with major depressive disorder. Collectively, these 13C-labelled breath tests may be useful in the diagnosis and subtyping psychiatric disorders such as schizophrenia and depressive disorder.
Fasting 13C-glucose breath test (FGBT) was newly developed as a fast diagnostic method for liver insulin resistance. It is a test to evaluate liver insulin resistance from glucose metabolism in liver, especially balance of gluconeogenesis and glycolysis system. In general, liver insulin resistance often evaluates the condition after hyperinsulinemia. FGBT can evaluate liver insulin resistance before becoming hyperinsulinemia and can contribute to the prevention of diabetes through its early diagnosis.
Nihon University School of Medicine has incorporated a 13C breath test into its pharmacological training since 2016. In the training, (i) 13C-urease, (ii) 13C-phenylalanine (L-[1-13C] phenylalanine), and (iii) 13C-leucine (L-[1-13C] leucine) breath tests are conducted. Introducing a 13C breath test into student training can collateralize the activity of the basic educational principle and the association with the clinical medicine. Unlike radioactive isotopes, the stable isotope 13CO2 requires no special facility and can be simply handled with measuring equipment. Introducing a 13C breath test into student training poses problems, such as the initial cost of measuring equipment and the use of expensive reagents, but should enhance the association between basic and clinical medical education.