This is a review of the article "Sex and Gender Issues in Multiple Sclerosis" which can be read here.
Article Summary
In recent decades the ratio of women to men that contract multiple sclerosis has increase from 2.3:1 to 3.5:1. The prevalence of autoimmune disorders like MS has been increasing in women significantly more than it has in men. This article investigates some of the effects of sex on multiple sclerosis symptoms and treatment effectiveness in an effort to begin to understand why so women are more likely to have the disease.
Certain genetic markers have be shown to correspond to higher risk for multiple sclerosis, including the HLA marker discussed in the previous post. After reviewing various GWAS (genome wide association studies) the researchers of this article claim that there is no real variation between men and women with regard to these genetic markers. As the article claims though, "our methods are constantly improving" differences in genetic expression of MS between men and women could be identified in the future.
The scientists also analyzed regions of DNA other than the HLA loci that are tied to sex differences. They hypothesized that how men and women react to sun exposure and vitamin D intake could be different and cause different levels of risk for the disease. Other scientists have theorized that the X chromosome is related to immune function. Women, with incorrect X chromosome inactivation, may get incorrect doses of immune genes which could explain a higher prevalence of autoimmune diseases in women.
Certain genetic markers have be shown to correspond to higher risk for multiple sclerosis, including the HLA marker discussed in the previous post. After reviewing various GWAS (genome wide association studies) the researchers of this article claim that there is no real variation between men and women with regard to these genetic markers. As the article claims though, "our methods are constantly improving" differences in genetic expression of MS between men and women could be identified in the future.
The scientists also analyzed regions of DNA other than the HLA loci that are tied to sex differences. They hypothesized that how men and women react to sun exposure and vitamin D intake could be different and cause different levels of risk for the disease. Other scientists have theorized that the X chromosome is related to immune function. Women, with incorrect X chromosome inactivation, may get incorrect doses of immune genes which could explain a higher prevalence of autoimmune diseases in women.
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| A woman has two chromosomes in each cell. Usually one X chromosome is inactivated to ensure that she receives the correct dosage of each gene |
Sex hormones have also been analyzed as a potential culprit for the differences in men and women. Pregnant women, with high levels of the hormone oestriol, have fewer relapses of neurological symptoms. Not much is known for certain about the effect of sex hormones, but the scientists mention a trial taking place at the time of the article's publication (2013) that is studying the use of oestriol as a treatment for MS.
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| Women are much more likely to develop autoimmune diseases though scientists don't always know why. |
In studying EAE (experimental autoimmune encephalomyelitis or, animals with and induced MS-like disease), scientists have found that testosterone may serve as a mild protection against autoimmune disease. Furthermore, these studies have indicated a difference in how vitamin D alleviates MS symptoms in male and female mice with female mice responding to vitamin D treatment more.
Multiple sclerosis experts have had varying views on pregnancy. While it was once thought to be dangerous for women with the disease, scientists have found that MS relapses decrease during pregnancy. This is thought to be because a woman's immune system is suppressed so as not to attack the fetus. As suppressed immune system would lead to fewer symptoms of an autoimmune disorder. It should be noted that after pregnancy, relapse can still and often does occur.
There are multiple other suspected relationships between MS and pregnancy and breastfeeding but the current research is too sparse for any real conclusions to be made. The authors suggest that further studies must be done to better understand autoimmune disparity between the sexes.
My Thoughts
The article did an excellent job of providing future questions for research and indicating what gaps in our knowledge of MS we need to fill. I agree that more large studies must be conducted to better understand the higher prevalence of the disease in women. I would further be interested to research more about how the X chromosome could be related to autoimmune diseases. Perhaps this course of action would not only explain the growing ratio of women to men, but also provide a better understanding of how to treat and/or cure autoimmune disorders.
References:
Harbo, H. F., Gold, R., & Tintoré, M. (2013). Sex and gender issues in multiple sclerosis. Therapeutic Advances in Neurological Disorders, 6(4), 237–248. http://doi.org/10.1177/1756285613488434
Image Sources (in order of appearance):
https://3c1703fe8d.site.internapcdn.net/newman/csz/news/800/2015/whenextraxch.jpg
http://www.clipartkid.com/images/563/light-pink-female-symbol-clip-art-at-clker-com-vector-clip-art-KxPUzf-clipart.png
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