Testosterone represses urinary excretion of the alpha-tocopherol metabolite alpha-carboxymethylhydroxychroman in rats

摘要

In rats, plasma and tissue concentrations of alpha-tocopherol, a predominant form of vitamin E in mammals, are known to differ between the sexes. In order to examine sex differences in alpha-tocopherol metabolism, we investigated urinary excretion of the alpha-tocopherol metabolite alpha-carboxymethylhydroxychroman (alpha-CEHC) using Wistar rats. First, we measured alpha-CEHC in urine of 9 -week-old male and female rats in basal and alpha-tocopherol-administered conditions. We observed that female rats excrete significantly more alpha-CEHC than male rats via urine. This sex difference was observed in matured 9 -week-old rats but not in premature 3 -week-old rats, suggesting that the difference may relate to sex hormones. In order to confirm this, we examined the effect of ovariectomy and orchiectomy on female and male rats, respectively. The results of castration clearly demonstrated that orchiectomy enhanced urinary excretion of alpha-CEHC, supporting the hypothesis that testosterone repressed alpha-tocopherol metabolism. We then administered testosterone propionate to orchiectomized rats and observed down -regulation of alpha-CEHC excretion. Taken together, these results indicate that testosterone represses the metabolism and urinary excretion of alpha-tocopherol in rats. This is the first report to show a sex -dependent difference in urinary excretion rate of an alpha-tocopherol metabolite and contributes to the understanding of vitamin E metabolism. (C) 2018 Elsevier Inc. All rights reserved.