January 15, 2006

Iceland study finds important diabetes gene

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - A single genetic change could
predispose close to 40 percent of the population to type-2
diabetes, researchers said on Sunday.

The gene, identified in a study of Iceland's comprehensive
genetic records, is carried by 38 percent of the Northern
European populations studied, and is also common among
African-Americans, the researchers said.

Writing in the journal Nature Genetics, Kari Stefansson of
DeCode Genetics and colleagues said their finding could help in
the development of an easy test for diabetes risk and might
also lead to better drugs for the disease, which affects nearly
200 million people worldwide and 18 million people in the
United States alone.

"If you have one copy of this variant, which 38 percent of
people do, your risk of developing type-2 diabetes is increased
by 40 percent," Stefansson, who is chief executive officer of
DeCode, said in a telephone interview.

"Seven percent have two copies and have a 140 percent
increase in risk. If you would remove this variant out of the
population, you would remove basically 20 percent of the type-2
diabetes cases from our society."

Type-2 diabetes was once known as adult-onset diabetes, and
differs from type-1, or juvenile, diabetes. With an inability
to use and produce insulin properly, sufferers end up with too
much glucose in their blood and have high rates of heart
disease, blindness, nerve damage and limb loss.

Type-2 diabetes is associated with obesity, overweight and
a lack of exercise and is being found in children more commonly

"It is a disease that occurs at the interface of genes and
environment," Stefansson said.

The variant his team found, called TCF7L2, is associated
with a younger onset of the condition, and sufferers appear to
be thinner than the average type-2 diabetes patient.


"This discovery sheds new light on the biological causes of
the disease. Importantly, virtually all of this risk can be
captured by looking at a single-letter change in DNA -- ideal
for the development of a genetic test for assessing individual
risk and developing more personalized and effective prevention
strategies," Stefansson said.

"This is also an exciting starting point for the discovery
of new drugs, and we are actively pursuing the development of
both diagnostic and therapeutic products to better prevent and
treat T2D," he added.

While his team studied mostly northern Europeans --
Icelanders, Danes and U.S. citizens -- Stefansson said he also
saw other variants that are found in people around the world
that also confer diabetes risk.

Iceland-based DeCode specializes in trolling the country's
DNA database for information. Virtually the entire population
of Iceland, a highly inbred group, has voluntarily donated DNA
to be sequenced, analyzed and published.

The DeCode team found the gene first in Icelanders with
diabetes, and then looked in 228 Danish women with type-2
diabetes and 539 who did not have the condition.

They also looked at 361 American diabetics of European
descent and 530 similar people without diabetes.

They said the TCF7L2 gene can be found on chromosome 10q.
It is a transcription factor, a gene that controls another
gene, in this case the well-known Wnt signaling pathway. Wnt is
involved in key developmental and growth regulatory mechanisms
of cells.