Epigenetics: Are obese mother's to blame for childhood obesity?
I am not trying to scare my readership off with this title but this is a real question that is gaining traction in the scientific community and beyond. In fact as the picture for this article demonstrates, mainstream media has grabbed hold of the topic as well.
The concept here involves “Epigenetics”. This is a blossoming field and in basic terms means that our DNA carries certain coding to produce an effect but only if there is an external stimulation that kick-start the process. Alberta Health Services has published a wonderful video explaining in lay terminology the concept which can be found here http://www.albertafamilywellness.org/resources/video/science-seconds-epigenetics
Take for example maternal smoking in pregnancy. I could ask anyone on the street including smokers whether smoking is a good thing for a pregnant woman to do and in every case other than satisfying their nicotine addiction the answer would be no. Smoking in fact has been linked to neonatal outcomes including reduced newborn weight, altered neurodevelopment amongst other things. What is now known though is that something is happening at the DNA level in those kids who are born to these mothers. In the case of smoking the DNA experiences increased methylation and the expression of microRNA becomes dysregulated. As a medical student I simply thought that the effect was all related to poor placental blood flow from the nicotine and other toxins in the smoke but what is happening clearly in addition to such effects are actual changes at a microscopic level. For a complete discussion of the effect of smoking click on the following link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3581096/
Another example of this phenomenon is in allergic disease. It is well-known that a major risk factor for asthma, eczema, food allergy and allergic rhinitis is a family history of one of these such conditions. Curiously though if you have a grandparent or parent that lived on a farm that association is weakened. Think about that for a moment. You didn’t live on the farm, your mother or your grandmother did. Something about the farm affected their DNA and because of it even though your father had bad eczema as a child you don’t. For a thorough review of this topic click here.
What about the title of this article? Are mother’s really to blame for the widespread epidemic of childhood obesity? There is no doubt that dietary choices by the children themselves and access to sugary drinks and soft drinks must take some of the responsibility but a paper from the Mayo clinic has ignited a bonfire of controversy on the internet by claiming that maternal obesity leads to in utero programming that condemns your children to obesity in adolescence. The controversial paper can be found here: http://www.ncbi.nlm.nih.gov/pubmed/?term=25440888 and a discussion in the Globe and Mail here http://www.theglobeandmail.com/life/health-and-fitness/health/studying-obesity-through-maternal-health-before-and-during-pregnancy/article21834086/
In essence one of the most common expressions of my childhood was wrong. It really isn’t “you are what you eat” but rather ” You are what your mother or your grandmother ate”! Beyond that, it is turning on its head the concept that many people have before they start a family. How many times when you were a young person did you smoke, consume excessive alcohol, eat too much fatty food, experiment with illicit drugs or travel to destinations with poor sanitation and perhaps even acquire a tropical infection. In each of these instances you thought, it’s my life and no one is at risk except for myself. It turns out we may have been very wrong! These decisions might not have caused you any serious harm but they may have implications for your children or grandchildren or great-grandchildren who happen to acquired a gene that is sensitive to these past exposures!
I am not an expert in the field by any stretch of the imagination but I wanted to publish this more as a resource for people to become aware of this exploding field of science. It is turning traditional genetics on its head and unravelling such things as why two people with the same genetic mutation have such different manifestations of a condition.
If you are interested further in this topic I would refer you to some incredible videos that explain this extremely well by the BBC program Horizon. You can find this program on YouTube at the following URL and there you will find the rest of the videos in this 5 part series. Get ready to have your world turned upside down!