17-ketosteroids and 6-phosphogluconic-acid

Liver metabolites and in vitro enzyme activities were measured in Sprague-Dawley rats pair-fed the standard NIH diet with or without 0.6% (wt/wt) dehydroepiandrosterone (DHEA) for 16 d. Absorption of DHEA from the gut was confirmed by a 300-fold increase in urine 17-ketosteroids in DHEA-treated animals. Of the liver metabolites measured only 6-phosphogluconate was significantly changed, increasing by less than a factor of two in the DHEA-treated animals, 38.7 +/- 2.2 nmol/g, above the value in the pair-fed controls, 22.5 +/- 2.5 nmol/g. Contrary to the in vitro findings that DHEA inhibits glucose-6-phosphate dehydrogenase (EC 1.1.1.49), thus leading to the hypothesis that DHEA inhibits fat synthesis by diminishing the availability of NADPH, the [NADP+]/[NADPH] ratios calculated from the 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42) and malic enzyme (EC 1.1.1.40) redox couples were no more oxidized in the DHEA-treated animals than in the control animals. Malic enzyme and isocitrate dehydrogenase activities were 620 and 25% higher in DHEA-treated animals than in pair-fed controls. There was no change in the measured activity of glucose-6-phosphate dehydrogenase or 6-phosphogluconate dehydrogenase. These data give no support to the hypothesis that administration of DHEA per os results in decreased cytoplasmic NADPH in liver.

Topics: 17-Ketosteroids; Animals; Body Weight; Dehydroepiandrosterone; Diet; Food; Gluconates; Glucosephosphate Dehydrogenase; Isocitrate Dehydrogenase; Liver; Malate Dehydrogenase; Male; NADP; Pentose Phosphate Pathway; Phosphogluconate Dehydrogenase; Rats; Rats, Inbred Strains