Services like 23 and me and AncestryDNA can provide us with our personal genetic blueprints. How much can we learn from these services? Can we do anything about our fate if we have “bad” genetics? In short, our genetics certainly are important, but here I will argue for the “Nurture” side of the Nature-Nurture discussion.
Genotype and phenotype
First, to orient us, our DNA (deoxyribonucleic acids) is our genetic instructions, or genotype. When the body needs, say a new blood cell, the genetic instructions are read and expressed, the body reads the genetic instructions and builds all the proteins necessary to make a new cell.
In a nutshell, your genotype contains information for every possible protein you can build (proteins have important jobs for life processes). Your phenotype represents the noticeable characteristics, or observable expression of genes. Think eye color, hair color, etc.
The good news
Authors on a 2010 study shared, “although some genotypes may be associated with certain phenotypes, the overall physiological significance is multifactorial and the result of interactions between the genome, the epigenome, and the environment, widely vary on an individual basis.” The take away message is basically even though you may not have been dealt a perfect (genetic) hand, there is much to improve upon from your environment and lifestyle because of epigenetics. †
There are many factors that affect our epigenetics (factors that cause our DNA to be expressed or not), such as diet habits, exposure to pollution, and physical activity habits. Epigenetics can be a confusing concept to understand, so let’s dig into it a bit more.
In the photo below, there is a chromosome (top left, large purple “X”) being “unwound” to expose DNA strands (bottom left, classic double-helix structure). On the bottom right, the pink area of the purple strand represents a “protein coding” gene (of which, there are about 20 thousand protein coding genes within our entire genome).
To express a certain gene, it must be accessible. Different chemicals (methyl groups, acetyl groups) can act to wind or unwind different portions of our genome. Methyl groups may also block protein building completely. Also, epigenetic factors can be added to the histone tails to effect gene expression. These adjustments result in some genes becoming “hidden”.
As in the photo above, these chemical changes can be the difference between a gene (pink) being accessible (and active) or not accessible (and inactive). Quick animation of this process here.
The next question is what controls our epigenetics? And what exactly that means for how our body operates?
Given the same diet and exercise training, identical twins have similar changes in body fat, even where that fat loss primarily occurred. However, if you peek at the photo below of a pair of identical twins, the effects of different health behaviors are very apparent.
Clearly, how we interact with our environment is important. We can see our muscles grow after resistance training, but there is much happening below the surface of what we can see.
Brain health and blood sugar
In rats, exercise improves memory formation and stress coping. A 2017 review looked at the evidence from several animal studies, and suggested exercise to alter epigenetics and to increase the expression of brain-derived neurotrophic factor (BDNF). BDNF promotes mental health and helps protect against neurological disorders, like Alzheimer’s. Another win for exercise.
For humans, a study in identical twins reported that greater physical activity levels were associated with better blood sugar control and changes in brain structure. This suggests that given the same genes, staying active can still be protective of future type 2 diabetes risk. Remember, progress not perfection is the goal.
The telling telomeres
Telomere length is related to age, shortening over time. Telomeres are the protective caps at the end of our genes (pink in the photo below). Think of a telomere as a punch ticket at an amusement park. Every time you go on a ride one of your tickets are punched. After each ticket gets punched a certain number of times it becomes no longer useable.
Telomeres, and genes, have a set amount of times they can be used to help a cell repair itself or to make a new cell. When a cell cannot replicate, things can go downhill fast.
Does exercise prevent some of this telomere shorting?
A recent review describes how exercise maintains telomere length. This includes reduced chemical (oxidative) stress and inflammation. And also increased satellite cells (can develop into any cell type that is needed) and telomerase (an enzyme for telomere activity) activity. While there appears to be many beneficial effects of exercise on telomeres, this area of research is in its infancy and more research is coming.
Interestingly, they do sell telomerase creams on Amazon. Although, I would examine the research on the specific compounds in each concoction prior to ordering. Check the health claims against the peer-reviewed scientific literature. This is the largest online medical library in the world.
We are born with a set genetic code. How we interact with our environment determines how we apply our genetic instructions. Genetics research is helping us explore the limits of sports performance, but more importantly helping us understand how to improve health. As an exercise scientist, I think about how this new information can be used to help promote physical activity, but I am also excited as genetics research could provide new prevention and treatment targets for disease. Aside from lifestyle changes we can adopt, a new gene editing technique is being developed to edit our genetic code (CRISPR*).
I’m looking forward to hearing back about my 23andme results (no affiliation/royalties). Everyone who gets their DNA tested can find out how dietary saturated fat affects their blood cholesterol levels or how caffeine intake affects their sleep quality. But, importantly, these services will collect a massive amount of data that can be used to learn a whole lot about genetic disorders.
With that said, I strongly acknowledge the value of lifestyle to positively affect our health. Further, I believe the direction we should be heading is one that identifies and knocks down barriers that prevent these positive health behaviors.
As always, feel free to share your thoughts, comments, and questions.
Thanks for reading.
Editor(s): Joe Perucci, BS; Austin Robinson, PhD
Curious to learn more? Check out these related resources.
† For more on the interesting topic of genetics and sports performance I highly recommend The Sports Gene by David Epstein. Check out his TED talk here. (I have no affiliation with author/publisher)
* CRISPR, the acronym for the mouthful “Clustered Regularly Interspaced Short Palindromic Repeats”, is the technique being refined to fix gene mutations by targeting “bad” genes and removing them completely or replacing them with “good” genes. New clinical research trials in the U.S. are getting underway, specifically in the areas of blood disorders (beta thalassemia, sickle-cell disease, plasma cell cancer), connective tissue cancer, and skin cancer.
“Those who do not find time for exercise will have to find time for illness” -Edward Stanley
High-fat feeding in individuals with obesity increased methylation (or hiding) of the leptin gene. This meant less leptin gene expression, which is not ideal as leptin is important for inhibiting feelings of hunger.
Smoking, not surprisingly, affects epigenetics in a negative way. The more worrisome recent observations suggest that smoking not only harms the current health and epigenetic regulation of the mother but also may negatively impact the genetics of the offspring.
Case study of identical twins removing sugar or fat from their diets.