Differential metabolism of androst-5-ene-3β,17β-diol between rats, canines, monkeys and humans

The potent anti-inflammatory activity of exogenous dehydroepiandrosterone (DHEA) in rodents has not translated to humans. This disparity in pharmacological effects has been attributed to factors such as differences in expression and function of molecular targets and differential metabolism. Hepatocytes from rats, dogs, monkeys, and humans were used to measure species-specific metabolism of a related compound, androst-5-ene-3β,17β-diol (5-AED) using reversed-phase radio-HPLC, to explore the metabolic contribution to this interspecies disparity. We found that rat hepatocytes transformed 5-AED predominantly into an array of highly oxidized metabolites. Canine metabolites overlapped with rat, but contained a greater abundance of less hydrophilic species. Monkey and human metabolites were strikingly less hydrophilic, dominated by 5-AED and DHEA conjugates. From the accumulating evidence indicating that the DHEA anti-inflammatory activity may actually reside in its more highly oxidized metabolites, we advance a hypothesis that the virtual absence of these metabolites in humans is central to the failure of exogenous DHEA to produce a potent pharmacological effect in clinical investigations. Accordingly, emulation of its anti-inflammatory activity in humans will require administration of an active native metabolite or a synthetic pharmaceutical derivative.