Diabetes is one of the most widespread health issues today, as it globally impacts more than 500 million people. Although lifestyle choices, such as one’s diet and exercise levels, are a major component of the development of this chronic condition, genetics also have a powerful influence in the progression of diabetes, especially when it comes to determining who is more at risk. In order to predict, prevent and manage diabetes, it’s vital to understand one’s genetics.
The Two Main Types of Diabetes and Their Genetic Links
Both types of diabetes (Type 1 and Type 2) include issues with the hormone that aids in regulating blood sugar, known as insulin. However these two versions of diabetes contrast greatly, as they develop differently and have different genetic foundations.
To begin, Type 1 diabetes is an autoimmune disorder, where the body attacks its own cells that produce insulin in the pancreas. Genetics have a strong role in this type of diabetes. Specific genes on chromosome 6 of the human leukocyte antigen complex (HLA for short), will increase the risk of developing Type 1 diabetes, as these genes influence the immune system’s ability to differentiate between body cells and foreign invaders.
For instance, those with certain combinations of the HLA-DQ and HLA-DR genes have a higher chance of developing Type 1 diabetes. However, not everyone with such specific genetic combinations develops this chronic condition, which proves that although genes play a major role in the development of diabetes, including Type 1 diabetes, there are other important factors at play. This includes environmental triggers, such as viral infections that can activate the disease.
On the other hand, although genetics still play an important role in type 2 diabetes, Type 2 diabetes is more so influenced by lifestyle factors. This type of diabetes is caused by insulin resistance and a consequent gradual loss of insulin production. Circling back to genetic factors, scientists have identified over 150 genetic variants associated with an increased risk of Type 2 diabetes. One key gene that affects how the body uses insulin as well as how it regulates blood sugar levels is gene TCF7L2. People who carry certain variants of this gene can have up to an 80% higher risk of developing Type 2 diabetes.
Inheritance Patterns and Family History
Moreover, having a family member with diabetes significantly increases your own risk. In terms of Type 1 diabetes, if one parent has it, the child has about a 5%–8% chance of also developing it. And if both parents have it, the risk increases to 30%. Type 2 diabetes is even more strongly inherited: If one parent has it, the child’s risk is about 40%, and if both parents have it, the risk rises to around 70%, which is much greater compared to the Type 1 diabetes circumstance.
However, diabetes does not follow a simple pattern of inheritance like some single-gene disorders, such as cystic fibrosis. Instead, as diabetes involves multiple genes that contribute to the risk, along with environmental and behavioral factors, it is considered a polygenic condition. Therefore predicting who will develop diabetes is more complex, but there are also more opportunities for early intervention.
The Role of Epigenetics
There has been recent research in the studies of how behaviors and environment can change the way genes work, known as epigenetics, which has added more data and depth to understanding diabetes. For instance, poor diet or high stress may trigger chemical changes in one’s DNA, which affects how certain genes are turned on or off. These changes can sometimes be passed down to future generations. Therefore even if someone inherits a diabetes-related gene, healthy habits have the ability to reduce their risk of developing the disease.
One study from the National Institutes of Health showed that children of mothers who had diabetes during pregnancy were more likely to develop insulin resistance as teenagers. And this is not solely due to genetics, but also to the environment in the mother’s womb, which proves how genetic and environmental influences are closely connected in overriding one another to initiate or halt the development of diabetes.
How Genetic Testing Helps
An increasingly common method to care for diabetes is genetic testing, where those with a family history of diabetes can get tested for the certain gene variants to learn more about their own risk. For example, Maturity-Onset Diabetes of the Young, MODY for short, is a form of diabetes that is very rare and inherited, is caused by a single gene mutation and fortunately can be identified with genetic screening.
Moreover, knowing your genetic risk can motivate early lifestyle changes, such as improved diet, regular exercise, and more frequent medical checkups. For some individuals, genetic testing can also lead to more personalized treatments. And in the future, as scientists learn more about the genetic basis of diabetes, it may even be possible to “switch off” harmful genes through gene therapy.
Works Cited
Atkinson, Mark A., and George S. Eisenbarth. “Type 1 Diabetes: New Perspectives on Disease Pathogenesis and Treatment.” The Lancet, vol. 358, no. 9277, 2001, pp. 221–229. ScienceDirect, https://doi.org/10.1016/S0140-6736(01)05415-0.
Centers for Disease Control and Prevention. “Diabetes and Genetics.” CDC, 11 May 2022, https://www.cdc.gov/genomics/resources/diseases/diabetes.htm.
Florez, Jose C. “Genetics of Diabetes: What Have We Learned and What’s Next?” Current Diabetes Reports, vol. 16, no. 7, 2016, pp. 1–9. Springer, https://doi.org/10.1007/s11892-016-0755-4.
Sanghera, Dharambir K., and Rasheed Ahmad. “Impact of Genetics and Epigenetics on the Pathogenesis of Type 2 Diabetes Mellitus.” Journal of Diabetes Research, vol. 2019, Article ID 3012645, 2019, https://doi.org/10.1155/2019/3012645.
Simmons, Rebecca A. “Epigenetics and Maternal Nutrition: Nature vs. Nurture.” The Journal of Clinical Investigation, vol. 121, no. 9, 2011, pp. 3489–3491. https://doi.org/10.1172/JCI59902.
Sparsø, Tine, et al. “The Genetic Architecture of Type 2 Diabetes.” Current Opinion in Genetics & Development, vol. 18, no. 3, 2008, pp. 283–289. https://doi.org/10.1016/j.gde.2008.07.004.