Effects of dietary xylitol on redox state and gluconeogenesis in the rat liver.

Rats fed a 20% xylitol diet were compared to rats fed for 6 weeks a diet of either 20% glucose, cornstarch or sucrose (plus 45% cornstarch), or the AIN-76TM diet (basal diet). There were no differences between the rats (diarrhea-free) fed xylitol and those fed the other carbohydrate sources in the lactate/pyruvate ratio in freeze clamped livers. Gluconeogenesis was measured from 10 mM of various precursors in isolated hepatocytes. Rats fed xylitol had: a) a lower rate of glucose production from lactate compared to rats fed the sucrose, glucose or basal diet; b) a lower rate of gluconeogenesis from xylitol than in rats fed either the basal or glucose diets, and c) equal capacity to produce glucose from pyruvate, glycerol, dihydroxyacetone or alanine as rats fed the other diets. Ethanol added to isolated hepatocyte incubations did not have a greater inhibitory effect on gluconeogenesis in xylitol-fed animals than in those fed the other carbohydrates. Results of this study indicate that dietary xylitol has little effect on the hepatic cytosolic redox state or on the ability of the rat liver to produce glucose in the presence of ethanol, but may have an effect on the rate of glucose production from some precursors.