Studies on dehydrogenases of the glucuronate-xylulose cycle in the livers of diabetic mice and rats.

In view of reports that accessory pathways of glucose oxidation are enhanced in the diabetic state, we have determined the levels of key enzymes of the glucuronate-xylulose cycle in the livers of diabetic mice and rats. Genetically diabetic mice (db/db) were found to have increased levels of two NADP-linked enzymes of this cycle [NADP-xylitol dehydrogenase and NADP-L-hexonate dehydrogenase (aldehyde reductase II)], whereas other NAD- and NADP-linked dehydrogenase activities of the pathway were not changed. On the other hand, the livers of streptozotocin-diabetic mice and rats showed normal levels of all these enzymes. In the course of this study, evidence was obtained for the presence in db/db mouse liver of low molecular weight material inhibitory for glucose 6-phosphate dehydrogenase. The use of these animal models in diabetes research is briefly discussed.