Enzyme that digests vitamin A also may regulate testosterone levels

Scientists at the University of Illinois explored the impact of the enzyme Bco1 on testosterone levels and testosterone-sensitive tissues such as the prostate by comparing the prostatic function and testosterone metabolism of mice that lacked functional copies of the Bco1 gene with mice in the control group.

In the body, Bco1 splits one molecule of beta carotene — the pigment responsible for the orange color of carrots, pumpkins and other plants — to form two molecules of vitamin A. Scientists have hypothesized that Bco1 might be involved in other biological processes as well, but the current study is among the first to explore Bco1’s activities beyond splitting carotenoids.

“Previous studies have shown that mice lacking the Bco1 gene cannot cleave beta carotene, and we also know that a lot of people carry genetic variations in Bco1 that can affect their ability to metabolize carotenoids,” said the paper’s lead author, Joshua W. Smith, who conducted the research during his doctoral studies in nutritional sciences at the U. of I.

“Similarly, it is possible that men with variations in their Bco1 gene may have altered testosterone levels, as we saw in the mice that lacked Bco1,” said Smith, currently a postdoctoral fellow at the Johns Hopkins Bloomberg School of Public Health.

Both groups of mice were fed a diet free of beta carotene and other carotenoids but which provided vitamin A to maintain normal levels of that nutrient in their blood and livers.

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