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Type 2 Diabetes Has More Genetic Links Than Previously Thought |
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Written by Theresa Maher
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Saturday, 28 April 2007 |
Type 2 diabetes is the most common of the so-called lifestyle diseases that affect modern man. It is linked to obesity and is caused when the body does not produce enough insulin or when the cells are unable to utilize it.
Three genes were identified as being responsible for the condition as well, but this component was thought to play a minimal role in the eventual development of diabetes.
Now researchers are reporting many more gene variants as having the ability to increase the risk of type 2 diabetes. Three groups of researchers have identified seven new genes as being crucial in the development of diabetes. This takes the total number of genes identified as risk factors for diabetes to 10. The rise in the number of genetic links to type 2 diabetes is a direct result of the success of the human genome project.
Type 2 diabetes is the most common form of diabetes, according to the American Diabetes Association. It is estimated that 170 million people worldwide suffer from this disease. Around 20 million in the United States are diabetics. The disease is characterized by failure of the pancreatic beta cells to adequately respond to the increased demands for insulin that occur as a result of obesity-related insulin resistance. This raises the blood sugar levels beyond control.
Diabetes is the sixth leading cause of death by disease in the United States. It costs approximately $132 billion per year in direct and indirect medical expenses. Bringing some changes into routine lifestyle practices is very helpful in managing the condition.
However failure to control blood sugar levels leads to many complications including heart disease, blindness, nerve damage and kidney damage.
Genetics was thought to play some role in the development of type 2 diabetes, but the identification of three genes was thought to be accidental rather than being the main cause of diabetes. The current studies reported in Nature Genetics and Science burst open this myth and propose more genetic links than previously thought.
The first study was a large survey in Iceland, which identified a new genetic risk factor for type 2 diabetes. The research team led by Dr. Kari Stefansson, CEO of deCODE Genetics, reports the presence of CDKAL1 gene as a risk factor for type 2 diabetes.
The researchers mapped this gene variant by comparing several hundred thousand common genetic variants in healthy people against those found in diabetics. "It affects the secretion of insulin," Stefansson said. "So people with this variant secrete less insulin in response to glucose than people in the general population."
People having two copies of the risk variant had a 50 percent greater chance of developing type 2 diabetes as compared to people with one copy of the risk variant. The variant appears to increase the risk for type 2 diabetes by reducing insulin production because people having two variants produce 20 percent less insulin than people with one copy.
In the Science papers, three groups of researchers were able to identify three new gene regions associated with type 2 diabetes. Researchers from the Broad Institute of Harvard and MIT, Lund University in Sweden said two new regions CDKN2A and CDKN2B on chromosome 9 and IGF2BP2 on chromosome 3 increase risk of type 2 diabetes.
Leading drug company Novartis was also involved in the study. "These genes are not telling the entire genetic story of type 2 diabetes," said Michael Boehnke, a co-author of one of the Science studies. "This is a small part of the overall picture, which includes environment and behavioral factors." However, knowing the genetics of type 2 diabetes could lead to new targeted therapies."
The discovery of these new genes may lead to tests that make it possible for doctors to predict one's risk for developing type 2 diabetes. If identified early, possible patients might be able to institute minor lifestyle changes and thus control one of the devastating modern diseases.
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