A species of gut bacteria that breaks down a form of estrogen may contribute to depression in premenopausal women. Future therapies targeting this microbe could help treat the condition.
depression is treated twice as common in women than in men. While it is not clear why, previous research has suggested that the difference could be due to changes in estradiol – a form of estrogen that has been found to be linked to positive mood.
gaohua-wangram at Wuhan University Renmin Hospital in China and colleagues measured estradiol levels in blood samples from 189 premenopausal women, 91 of whom had depression. They found that, on average, estradiol levels were nearly 43 percent lower in people with the condition than in those without it.
The researchers then extracted the gut microbes from the participants’ fecal samples and mixed them in an estradiol-laced solution. Gut bacteria from women with depression break down estradiol more rapidly 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 microbe that degrades estradiol as Klebsiella aerogenes, which was 14 times more common in stool samples from participants with depression than in those without. female mice fed K. aerogenes for four weeks they had lower estradiol levels and showed more depressive symptoms, such as less grooming, than female mice not given the bacteria. Together, these findings indicate that K. aerogenes reduces estradiol levels, which could contribute to depression in women.
timothy sampson at Emory University in Atlanta, Georgia, says this study represents the next stages of microbiome research where the findings could guide the development of new drugs that target specific microbes and their metabolic processes. However, it is not clear how significant of an effect K. aerogenes has on the mood in humans, he says. It may be so small that future treatments do not improve depressive symptoms in women.