Journal of Biochemistry vol:115 issue:1 pages:87-92
A pyranoid polyol, 1,5-anhydroglucitol (AG), generally occurs in the human body as a humoral component. The plasma AG concentration in healthy individuals is maintained at a constant level, but it is markedly decreased in diabetes mellitus. This is due to hyperglycemia-dependent abolishment of renal AG retention. Hence, the plasma AG concentration has been established as a clinical marker for duration of hyperglycemia and since 1991 it has been practically applied to diabetic care in Japan. However, the details of the metabolism of AG and its physiological significance generally remain to be studied. In this study, we confirmed AG synthesis in cultured cells of a rat hepatoma line, Reuber H-35, in which AG was found to be derived from glucose, with retention of all six carbon atoms in the pyranoid structure. The fraction of the total glucose consumed by the cells, which was converted to AG (conversion efficiency) was at most 5 X 10(-6). The conversion efficiency increased at higher glucose concentrations (mM orders) where the glucose consumption rate was saturated. Since the rate of the hexokinase reaction, one of the rate-limiting steps in glucose consumption, has been estimated to be saturated at muM orders of glucose concentration, this observation was interpreted as indicating that AG is synthesized through a pathway which does not share the hexokinase reaction with glucose utilization. The presence of precursors other than glucose was also indicated in the time-course study of AG synthesis. Further, the amount of AG synthesized daily in humans is significant in comparison with the amount obtained from the diet.