The gut microbiota has a role in modifying host steroids, but the exact nature of this interaction has been unclear. New research shows that certain organisms in the gut microbiota produce the neurosteroid allopregnanolone (a derivative of progesterone), and also identified the mechanisms of this production.

“Steroids are exquisitely potent signalling molecules, but that also means they’re found in low levels in blood and tissues, making them hard to detect and quantify,” explains author Sloan Devlin. Using mass spectrometry techniques and faecal samples from healthy women, Devlin and colleagues identified that 21-dehydroxylation was dependent on the presence of certain bacteria (Eggerthella lenta and Gordonibacter pamelaeae). They also used comparative genomics to identify the bacterial gene cluster that was involved in 21-dehyroxylation. Hydrogen gas (in this instance produced by Escherichia coli) was found to be required, as the hydrogen promoted 21-dehydroxylation. “In other words, allopregnanolone production is an example of cooperative metabolism by gut bacteria: some bacteria make hydrogen gas, which promotes allopregnanolone production in other gut bacteria,” says Devlin.

肠道微生物群在改变宿主类固醇方面发挥着作用，但这种相互作用的确切性质尚不清楚。新的研究表明，肠道微生物群中的某些生物体会产生神经类固醇四氢孕酮（黄体酮的衍生物），并确定了这种产生的机制。

“类固醇是非常有效的信号分子，但这也意味着它们在血液和组织中的含量很低，因此很难检测和量化，”作者 Sloan Devlin 解释道。 Devlin 及其同事利用质谱技术和健康女性的粪便样本，发现 21-脱羟基依赖于某些细菌（ Eggerthella lenta和Gordonibacter pamelaeae ）的存在。他们还使用比较基因组学来鉴定参与 21-脱羟基化的细菌基因簇。发现需要氢气（在这种情况下由大肠杆菌产生），因为氢气促进 21-脱羟基化。 “换句话说，四氢孕酮的产生是肠道细菌协同代谢的一个例子：一些细菌产生氢气，从而促进其他肠道细菌产生四氢孕酮，”德夫林说。