Written by: Leah Solberg Woods, PhD
Do you know someone with Type 2 diabetes? There’s a good chance you answered yes as Type 2 diabetes is the most common form of the metabolic disease. Leah Solberg Woods, PhD, an Associate Professor of Pediatrics at Medical College of Wisconsin, takes an in-depth look at Type 2 diabetes and explains how a greater understanding of genetics will ultimately help us identify a more personalized approach in treating the disease.
What is Type 2 diabetes?
Type 2 diabetes (T2D) is a cardiovascular disease characterized by a malfunctioning hormone known as insulin. Insulin is released after eating a meal and allows glucose from the blood to be absorbed by cells to be used for energy or to be stored in fat cells. It is difficult for our bodies to extract energy from our food when insulin is not working properly. When the cells no longer respond to insulin, or when there is no longer enough insulin produced, glucose builds up within the blood. Increased glucose within the blood is toxic, leading to damage of many different organs within the body. In fact, T2D is a leading cause of kidney failure, blindness and limb amputation and a major risk factor for heart disease and stroke.
How many people have Type 2 diabetes?
Type 2 diabetes (T2D) affects more than 170 million people worldwide; this number is expected to double or triple within the next 30 years. In the United States, approximately 9 percent of the population is living with this disease, with the potential of increasing to 30 percent of the by 2050.
What causes Type 2 diabetes?
We know that both the environment and genetics play a role in the development of T2D. The most significant environmental factors are diet and exercise. If you eat well and exercise, your chances of developing T2D are decreased. However, the environment is not the only contributor. Family studies, and studies within different racial and ethnic groups have shown a large genetic component of T2D; meaning that some people who eat well and exercise still have a chance of developing the disease. Conversely, it also indicates that some people can live an unhealthy lifestyle and never develop the disease.
There also exists a strong interaction between the environment and genetics. One of the most telling examples of this relationship is the Pima Indians. Pima Indians in Arizona have one of the highest incidences of diabetes in the United States (up to 50 percent). There is relatively low diabetes prevalence, however, in Pima Indians from Mexico. Despite similar genetic make-up, the Pima Indians from Mexico have a healthier diet (with complex carbohydrates and less animal fat) and increased physical labor from working in the fields, relative to Pima Indians in the United States who have adopted a “Western” sedentary lifestyle with a diet high in fats and sugars. This example illustrates how genetic predisposition, along with unhealthy diet and sedentary lifestyle work together to lead to development of diabetes.
Type 2 diabetes and genetics
In addition to interactions with the environment, we know that diabetes is not caused by one single gene. In fact, it is likely that hundreds of genes play a role in susceptibility to diabetes. Genes are encoded within our DNA by four different nucleotides (the basic structural units of DNA): A, C, T, G. Each gene is made up of a different combination of these nucleotides, essentially providing an instruction booklet for our cells and forming what is known as the genome.
As humans, each of our genomes differ from each other by about 0.1 percent. Many of these differences make us who we are as individuals, including susceptibility to disease. Over the past several years, scientists have been able to identify genes containing genetic variants contributing to increased vulnerability to T2D. Despite identifying over 60 genes for diabetes, scientists still have yet to identify all of the genes involved with the disease. As scientists continue to uncover more genes involved in predisposition to T2D, we expect that this work will lead to a greater understanding of the disease as well as a more personalized approach in treating the disease.