Gut bacteria that breaks down oestrogen linked to depression in women

A type of gut bacteria that destroys a type of estrogen may contribute to depression in premenopausal women. Future therapies targeting this microbe may help treat the condition.

Depression is about twice as common in women than men. Although it is not clear why, previous research has suggested that the difference may be due to changes in oestradiol – a form of estrogen that has been shown to be associated with positive mood.

Gaohua WanMr at the Renmin Hospital of Wuhan University in China and his colleagues measured estradiol levels in blood samples from 189 premenopausal women, 91 of whom had depression. They found that, on average, estradiol levels were about 43 percent lower in those with the condition than in those without it.

The researchers then took gut microbes from the participants’ fecal samples and mixed them in a solution with estradiol. Gut bacteria from women with depression broke down estradiol faster than bacteria from women without the condition, suggesting that differences in the gut microbiome contribute to lower estradiol levels in depression.

The team identified the oestradiol-destroying microbe as Klebsiella aerogenes, which was 14 times more prevalent in stool samples from participants with depression than those without. Fed by female rats K. aerogenes within four weeks had lower estradiol levels and showed more symptoms of depression, such as less fixation, than female mice that were not given the bacterium. Together, these findings suggest that K. aerogenes lowers estradiol levels, which may contribute to depression in women.

Timothy Sampson at Emory University in Atlanta, Georgia, this study represents the next stages of microbiome research where findings can guide the development of new drugs that target specific microbes and their metabolic processes. However, it is not clear how significant an effect is K. aerogenes people have a mood, he said. It may be so small that future treatments will not improve depressive symptoms in women.