Saturday, January 26, 2013

Why the heart is different between men and women

Men and women are different at heart; not figuratively, but literally. It is known that there are functional differences between the physiology of the heart between men and women, This can be observed by looking at the prevalence of certain heart diseases: some are more frequent in men, while others are more frequent in women. Geneticists from the Washington University in St. Louis have found an explanation for such phenomenon.

It is not easy to study the human heart, as we need it ourselves to stay alive, and can therefore not simply donate it to science. Using hearts of the deceased has the downside that the tissue is no longer functional, which means its physiology is hard to study. The scientists from the Washington University had the opportunity to acquire hearts that had failed a transplantation procedure, and hearts that were deemed unsuitable for transplantation. They managed to acquire a total of 34 human hearts, and performed experiments that helped us to uncover why there are gender disparities.

A total of 89 genes were analyzed by the scientists, and each one of them is known to play a role in the electric conductivity of the heart. Because of synchronized contraction of the heart muscles, it is possible to pump blood all the way into our lower extremities. The heart pumps in synchronized fashion because the signals for contraction are conducted by electricity. There are two 'nodes' in the heart at which the electrical signals are bundled, in order to disperse them into the entire heart, ensuring synchronicity.

Analysis of these 89 genes revealed a rather big difference between men and women. It appears that men have higher activity in nearly all of the genes responsible for conduction of electrical signals in the heart. This may partly explain the difference in the occurrence of various heart diseases in men and women, but according to the scientists there are additional factors that are of importance. For example, women produce more of the sex hormone estrogen, which also affects heart physiology. It goes to show that this study does not necessarily solve why heart diseases have a different prevalence between men and women, but it does open up a range of new studies to dive into the underlying physiology.

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