Effect of glucagon on the xylitol-induced increase in the plasma concentration and urinary excretion of purine bases

Abstract 

To investigate whether glucagon affects the xylitol-induced increase in the production of purine bases (hypoxanthine, xanthine, and uric acid), the present study was performed with five healthy subjects. Intravenous administration of 300 mL 10% xylitol increased the plasma concentration and urinary excretion of purine bases, erythrocyte concentrations of adenosine monophosphate (AMP) and adenosine diphosphate (ADP), and blood concentrations of glyceraldehyde-3-phosphate (GA3P) + dihydroxyacetone phosphate (DHAP), fructose-1,6-bisphosphate (FBP), and lactic acid; it decreased the blood concentration of pyruvic acid and the plasma concentration and urinary excretion of inorganic phosphate. However, intravenous administration of 1 mg glucagon together with xylitol reduced the xylitol-induced changes in oxypurines, pyruvic acid, GABP + DHAP, and FBP, whereas it promoted the xylitol-induced increase in the urinary excretion of total purine bases and did not affect the xylitol-induced increase in the plasma concentration of total purine bases. In addition, in vitro study demonstrated that sodium pyruvate prevented the xylitol-induced degradation of adenine nucleotides in erythrocytes. These results suggested that gluconeogenesis due to glucagon increased the production of pyruvic acid, accelerated the conversion of NADH to NAD, and thereby prevented both the xylitol-induced degradation of adenine nucleotides in organs similar to erythrocytes and the inhibition of xanthine dehydrogenase in the liver and small intestine, resulting in decreases in the plasma concentration and urinary excretion of oxypurines. However, it was also suggested that in the liver storing glycogen, glucagon-induced glycogenolysis accumulated sugar phosphates, resulting in purine degradation, since the xylitol-induced increase in the ratio partially blocked glycolysis at the level of GABP dehydrogenase. Therefore, administration of glucagon together with xylitol may synergistically increase purine degradation more than xylitol alone, despite decreases in the plasma concentration and urinary excretion of oxypurines.

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