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Gene Affects the Risk of Type 2 Diabetes
Researchers have confirmed that a previously-discovered gene variant increases
susceptibility to type 2 diabetes. The good news is that even people with the
highest genetic risk benefited from healthy lifestyle changes.
 Earlier
this year, the deCode Genetics company published a statistical study linking
a variant in a gene called TCF7L2 to type 2 diabetes. Dr. Jose Florez of Massachusetts
General Hospital (MGH) and his colleagues set out to look at this gene in a group
of people that reflect the racial and ethnic diversity typical of the U.S. population
with diabetes. They turned to the Diabetes Prevention Program (DPP), a large
clinical trial comparing approaches for preventing diabetes in over 3,000 adults
at increased risk for developing type 2 diabetes.
The new study was published in the July 20, 2006, issue of the New England
Journal of Medicine. The researchers found one copy of the risk variant
in 40% of DPP participants, and two copies in 10%. For the 10% who inherited
two copies of the variant, the risk of developing diabetes was about 80% higher
than for non-carriers.
The hallmarks of type 2 diabetes are insulin resistance — the inability
to respond to insulin — and a gradual failure of beta cells to produce
enough insulin. "This variant of TCF7L2 is associated with decreased insulin
production, but not with any increase in insulin resistance," said DPP study
chair Dr. David M. Nathan of MGH.
The analysis showed that lifestyle intervention reduced risk even in those who
carried both copies of the risk variant. Florez said, "This finding emphasizes
that people at risk of diabetes, whether they're overweight, have elevated blood
glucose levels or have this particular genetic variant, can benefit greatly by
implementing a healthy lifestyle."
In the future, a genetic test for this gene variant may help doctors plan prevention
strategies for type 2 diabetes. However, how this risk factor relates to other
recognized risk factors — such as being age 45 and older, overweight, inactive
and having a history of gestational diabetes — isn't yet known. These relationships
will become clearer as researchers learn more about this gene. A better understanding
of the gene may also one day lead to new treatment approaches for people with
diabetes or those at risk.
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