It has been known for a long time that there is a complicated interaction between hormones, guts, and mental health. However, determining the most significant links inside the bodily systems has proven difficult.
But researchers recently identified a single enzyme in a new study that connects all three, Science Alert reported. Researchers said that its presence might be responsible for depression in certain women during their reproductive years.
Depression Linked to an Enzyme Which Explains Why It Is Twice as Common in Women Than Men
Why are Women Twice Likely to Experience Depression Than Men?
Di Li, a medical researcher at Wuhan University, and colleagues analyzed the blood serum of 91 women aged 18 to 45 years with depression and 98 without. Surprisingly, those suffering from depression had nearly half the serum levels of estradiol - the key type of estrogen our bodies use during our reproductive years.
The hypothesis that estradiol is linked to sadness in those with female reproductive hormones has existed for over a century. Natural estradiol decreases throughout menopause and after pregnancy are well-known to be associated with unfavorable mood changes.
Other conditions that can cause low estradiol and depression include polycystic ovary syndrome, in which the ovaries produce higher than normal levels of the androgens, causing reproductive hormones to become unbalanced, and congenital adrenal hyperplasia, which is a group of genetic disorders in which the body lacks one of the enzymes required to make specific hormones.
Depression's relationship to estradiol likely explains why it affects women twice as much as men. Estradiol is produced in the ovaries, processed in the liver, and transported into the stomach after performing its functions in our bodies, including regulating menstrual cycles. The hormone is partially reabsorbed back into the bloodstream to help sustain estrogen levels in the blood.
READ ALSO: Parental Stress Links Mother's Major Depressive Disorder With Child's Mental Health, Depression
Estradiol in the Gut
In the research titled "Gut-microbiome-expressed 3β-hydroxysteroid dehydrogenase degrades estradiol and is linked to depression in premenopausal females," published in Cell Metabolism, researchers looked into the actions of estradiol in the gut.
They found that the hormone was 78% degraded within 2 hours of being added to fecal microbiota samples from women with depression. However, the tube containing microbiome samples from women who did not have depression showed only a 20% decrease in hormone levels.
Scientists also transplanted the gut microbiota of five depressed women into mice, who demonstrated a 25% fall in estradiol levels in their blood serum compared to the mice control group. The enhanced breakdown of this hormone within the digestive tract appears to result from a gut bacterium.
The team isolated the bacteria by putting samples of the microbiome from depressed women onto an agar plate and feeding them just estrogen. Around 60% of the estradiol was metabolized into estrone two hours later.
Using mass spectrometry, they identified the microbe called Klebsiella aerogenes TS2020, which is characterized as white lumps with smooth, hazy borders. But as My UNI reported, the team thinks the gut bacterium is not the only one that can produce the enzyme. Other bacteria also include Bacteroides thetaiotaomicron and Clostridia bacterium.
They noted that the focus of their research has been on estrogen replacement therapy as a possible treatment for depression in women, but if the enzyme is produced, then it could lead to a relapse. Therefore, better treatment options are needed by understanding the connection between the brain, gut, and hormones.
RELATED ARTICLE: Irregular Sleep Pattern Can Increase Risk of Depression, Study
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