A new study on mice shows once again why it is important for scientists to include both male and female subjects in tests.
Metformin, a common drug antidiabetic believed to have brain repair properties can improve cognitive processes only in children and adult women.
The drug is called metformin, and since the 50s it has been one of the most used solutions to help people with type 2 diabetes lower their blood sugar levels. Recently, however, several laboratory tests have shown the ability to repair faster the brain after neurological damage that can lead to dementia or cognitive retardation.
According to biologist Cindi Morshead of the University of Toronto, metformin stimulates the growth of stem cells in the brain. If the thesis proves correct, the substance could be an extraordinary support for all sorts of brain damage or disorders.
“When we think about repairing the brain, one of the most promising approaches is to 'awaken' the stem cells that are already inside it. Once in action, they will take care of replacing the lost cells and repairing all or part of the damage."
The laboratory results
The Morshead team performed remarkably well in mouse experiments. In those who suffered brain damage from a heart attack, the results were encouraging enough to extend the tests to mice of different age groups.
When younger specimens and adult males were included the effect weakened, to the point where there was no improvement. In-depth analysis showed the existence of a strong gender difference. Female specimens responded much better to metformin.
Does it depend on sex?
The theory put forward is that the neural effects of the drug depend on the presence of larger doses of estradiol, a form of estrogen. Estradiol apparently enables this activity in the brain while testosterone inhibits it.
In other words, says the Morshead, these hormones “alter the 'microenvironment' of stem cells and therefore their behavior”.
Newborn mice of both sexes immediately receive an estrogen boom, while growing they differ: this explains the metformin reactivity for small and adult females, but not for males.
The study, published yesterday in the journal Science Advances, had a long gestation. No later than May, the scientist Rebecca Shansky Northeastern University stressed the need to carefully monitor gender differences in reactions to scientific tests.
Women also discriminated against in the laboratory
In some cases there are not enough female subjects among the research volunteers: in at least one recent case, that of the Ambien sleeping pill, this error has led to a drug with potentially dangerous effects on women.
“This study shows how considering the sex of volunteers is an opportunity in research,” says the Morshead. “If we had combined the two sexes and drawn conclusions, the beneficial effects of metformin would not have emerged.”
“Human studies are complicated on many levels, and considering the sex of the examinees separately adds further difficulty, but this work highlights its importance.”
