Is Asthma Always Hereditary?
As far back as 400 B.C. Hippocrates observed that asthma tends to run in families. Starting in the 1990s scientists started discovering various genes that were proven to predispose a carrier to developing diseases such as asthma, allergies and eczema. So it took nearly 2,400 years for Hippocrates to be proven right.
According to Lawrence Berkely National Laboratory (lbl.gov), "Asthma Linked Genes Discovered at Berkely Labs," two such genes called IL4 and IL13 were discovered on chromosome 5 in 1999.
IL4 and IL13 are believed to play a role in interleukins, which "play a role in regulating the immune system and in particular modulating the inflammatory response. Evolutionarily IL4 and IL13 are thought to prevent parasitic infection by generating localized inflammation."
In 2002 BBC News reported the discovery of the gene ADAM33 on chromosome 20 that was believed to play a "crucial role in making the airways of the lungs over-sensitive, thus increasing the risk of asthma." This discovery, I think, was neat because scientists believe it could one day result in a childhood test that could determine what kids are most at risk for developing asthma, as well as new treatment options.
Likewise, according to the BBC post, "The scientists estimate that the gene (ADAM33) could play a significant role in 40% of all cases of asthma."
According to the Wellcome Trust Centre for Human Genetics at the University of Oxford (wellcome.ac.uk), "Asthma susceptibility gene discovered,"a gene called PHF 11 was discovered on chromosome 13 in 2003. This "gene appears to regulate the blood B cells that produce Immunoglobulin E, the allergic antibody. Although new treatments take years to develop, the gene potentially provides a target for drugs that could turn off Immunoglobulin E and prevent allergic disease."
The post notes that scientists believe there are ten asthma genes, five of which were discovered as of 2003. Since then more have been discovered.
In 2007 sciencedaily.com "Gene Linked With Childhood Asthma Is Identified, Giving Hope For New Therapies," reported on the discovery of a gene called ORMDL3 on chromosome 17. Studies show this gene is more prevalent in children with asthma, and having the gene increases the risk of asthma by 60-70 percent. Once again the researchers believe this may lead to newer treatment options.
In 2008 news-medical.net, "Variation in CHI3L1 gene increases risk of asthma," reported the discovery of a gene variant on CHI3L1 increases blood levels of a biomarker for asthma called YKL-40. Another variant of the same gene lowers YKL-40 and protects against asthma.
According to the same article, YKL-40 "belongs to a family of enzymes called chitinases. These enzymes are part of the innate immune system's response to chitin, a common biologic polymer found especially in insects – including dust mites and cockroaches, which have been associated with asthma – as well as in certain disease-causing organisms, including fungi and parasitic worms. The chitinases help break down chitin. They also trigger inflammation, which is a central component of asthma.
In 2010 Medical Breakthroughs Reported by Ivanhoe (ivanhoe.com), "Gene Found for Childhood Asthma," a gene called DENND1B was discovered to express a protein of the same name "which is active in immune cell subtypes that regulate the body’s response to foreign bodies such as viruses, bacteria and allergens. The researchers found the same gene for asthma susceptibility in children of European and African-American ancestries."
DENND1B is involved in the release of cytokines that tell the body how to respond to foreign particles. In the case of asthma, this would cause the immune system to have an inappropriate response to foreign particles that are known as your common allergens, such as dust mites, molds, etc. This ultimately results in your over-reactive immune response, causing inflammation of the respiratory tract. Researchers hope to find a way to "intervene" with this pathway to treat asthma.
I could go and list more asthma genetic research, but I think you get the point: Bad genes cause asthma.
However, I would like to note here that while genetics may increase your risk for developing asthma, not everyone with the asthma gene will develop the disease. Is the asthma gene like a light switch that can be turned on and off? Perhaps?
If so, once we learn what triggers the switch we may find our causes and cures for asthma. (Stay tuned, because I have an upcoming post where I list 19 probable causes of asthma, many of which I've written about in the past year, such as Tylenol, lack of vitamin D, and mold).
Likewise, there have been many studies that show you don't necessarily need to be an asthma gene carrier to get asthma and/ or allergies. Exposure to anything that causes inflammation in your respiratory tract can lead to the development of these diseases, even if you don't have the gene.
Examples of non-genetic forms of asthma are (click links for further reading):
- Too much exercise
- Acid reflux (GERD)
- Chemical exposure
- Premature birth
- High fat foods
- Imbalance of microbes in your gut caused by antibiotics and modern diet
- Lack of exposure to germs caused by our modern way of life
- Lack of H. Pylori in your gut
So you can see that asthma can be hereditary as Hippocrates suggested so many years ago, yet it can also be developed by so many other means. In order to find an eventual cure, scientists have to continue research in all these areas.