英语文摘:Brain protein may explain depression in pre-menopausal women

WASHINGTON, June 4 (Xinhua) -- Women nearing menopause have higher levels of a brain protein linked to depression than both younger and menopausal women, according to a study published in the U.S. journal JAMA Psychiatry Wednesday.

The findings may explain the high rates of first-time depression seen among women in this transitional stage of life known as perimenopause, said the study by researchers at Canada's Center for Addiction and Mental Health.

"This is the first time that a biological change in the brain has been identified in perimenopause which is also associated with clinical depression," senior author Jeffrey Meyer of the center said in a statement.

During perimenopause, a common symptom is mood changes such as crying. Rates of first-time clinical depression among this group reach 16 to 17 percent, and a similar number get milder depressive symptoms.

Meyer has previously linked high levels of a protein called monoamine oxidase-A (MAO-A) to major depressive disorder, depressed mood related to alcohol dependence and smoking cessation, and the period immediately after childbirth.

According to Meyer's research team, MAO-A is an enzyme that is a pro-oxidant and breaks down brain chemicals such as serotonin, norepinephrine and dopamine, which help to maintain normal mood.

To investigate if MAO-A levels may explain the mood changes during perimenopause, his research team conducted brain scans of three groups of women using a brain imaging technique called positron emission tomography (PET).

Among the three groups of women, 19 were of reproductive age, 27 were in perimenopause, and 12 were in menopause.

On average, levels of MAO-A were 34 percent higher in women with perimenopause than in the younger women, and 16 percent higher than those in menopause, the team said.

The women in perimenopause also reported a higher tendency to cry, based on a questionnaire called the Adult Crying Inventory, and this was associated with high MAO-A levels in the front part of the brain, the prefrontal cortex, it said.

The researchers had also predicted that MAO-A levels would drop during menopause, once fluctuating levels of estrogen stabilized, and this also proved to be the case.

The results suggested new opportunities for prevention. "Using PET imaging, we can test treatments to see if they can prevent this elevation of MAO-A, and potentially prevent clinical depression," Meyer said.

One approach may be a dietary supplement, which he is currently investigating in another study of women after childbirth, to prevent post-partum depression.

Another approach may be to offer hormone replacement therapy at an earlier stage to prevent the fluctuation of estrogen levels, which is also linked to higher amounts of MAO-A, he added.