The presence of a protein expressed by the liver which inhibits insulin action may identify individuals more likely to develop type 2 diabetes, according to a new study released Tuesday by the Journal of the American Medical Association.

Researchers led by Joachim Ix at University of California, San Diego, found that higher serum levels of a protein called fetuin-A, produced by liver cells, was associated with type 2 diabetes in humans, independent of other risk factors.

"Higher fetuin-A was associated with a 1.7-fold increased risk of diabetes, when adjusted for other factors," said Ix. Despite compelling laboratory and animal data of the protein's role in insulin resistance, until now the association of fetuin-A with new development of type 2 diabetes had not been evaluated in humans, according to Ix. "On the basis of this study, fetuin-A might be considered as a novel therapeutic target for prevention or treatment of insulin resistance," he said.

Type 2 diabetes is a metabolic disorder characterized by insulin resistance that has become a global epidemic. The increased prevalence of obesity is a major contributing factor; however diabetes does not develop in all obese individuals, and reasons why one individual develops type 2 diabetes while another dose not are largely unknown.

Recent research shows that proteins from fat tissue called adipocytokines regulate the metabolism of blood sugar or glucose, and may ultimately prove to be a target for new diabetes therapies. In contrast, fetuin-A is produced in liver cells, and is secreted into blood. In laboratory studies, fetuin-A binds to the insulin receptor found in muscle and fat, resulting in insulin resistance - - the hallmark of diabetes. Preliminary data from a separate study of participants without diabetes had shown an association between fetuin-A and insulin resistance.

In this study, the researchers measured levels of fetuin-A in 519 diabetes-free individuals aged 70 to 79 years, and followed them for development of diabetes for six years. Participants with the highest levels of fetuin-A showed a higher risk of developing diabetes, when compared to those with low levels. The association was not affected by levels of adipocytokines.

The researchers note that further studies should evaluate whether the results prove true in middle-aged individuals in whom the incidence rate of type 2 diabetes is highest.

(Xinhua News Agency July 9, 2008)