Michael Garratt, Kim A. Lagerborg, Yi‐Miau Tsai, Andrzej Galecki, Mohit Jain, Richard A. Miller

Longevity in mammals is influenced by sex, and lifespan extension in response to anti-aging interventions is often sex-specific, although the mechanisms underlying these sexual dimorphisms are largely unknown. Treatment of mice with 17-α estradiol (17aE2) results in sex-specific lifespan extension, with an increase in median survival in males of 19% and no survival effect in females. Given the links between lifespan extension and metabolism, we performed untargeted metabolomics analysis of liver, skeletal muscle and plasma from male and female mice treated with 17aE2 for eight months. We find that 17aE2 generates distinct sex-specific changes in the metabolomic profile of liver and plasma. In males, 17aE2 treatment raised the abundance of several amino acids in the liver, and this was further associated with elevations in metabolites involved in urea cycling, suggesting altered amino acid metabolism. In females, amino acids and urea cycling metabolites were unaffected by 17aE2. 17aE2 also results in male-specific elevations in a second estrogenic steroid-estriol-3-sulfate-suggesting different metabolism of this drug in males and females. To understand the underlying endocrine causes for these sexual dimorphisms, we castrated males and ovariectomized females prior to 17aE2 treatment, and found that virtually all the male-specific metabolite responses to 17aE2 are inhibited or reduced by male castration. These results suggest novel metabolic pathways linked to male-specific lifespan extension and show that the male-specific metabolomic response to 17aE2 depends on the production of testicular hormones in adult life.