Ascorbic acid synthesis and breakdown were investigated in isolated hepatocytes prepared from fasted mice. Stimulation of gluconeogenesis by alanine or xylitol led to ascorbate synthesis. On the other hand, ascorbate or dehydroascorbate addition resulted in concentration-dependent glucose production and elevation of the pentose phosphate pathway intermediate xylulose 5-phosphate. Stimulation of ascorbate oxidation and/or the inhibition of dehydroascorbate reduction increased glucose formation. Inhibition of the pentose phosphate pathway decreased glucose production from dehydroascorbate with increased accumulation of xylulose 5-phosphate. These results suggest that ascorbate can be recycled by a novel way involving intermediates of the pentose phosphate pathway, gluconeogenesis and hexuronic acid pathway.
