LOS ANGELES - December 2002 - Black and Hispanic children face higher risk than white children for insulin resistance-a stepping-stone to type 2 diabetes-regardless of whether they are heavy or thin, according to researchers at the Keck School of Medicine of USC.
Findings by Michael I. Goran, Ph.D., professor of preventive medicine, and his USC colleagues appear in the December issue of Diabetes Care, a journal of the American Diabetes Association. Besides finding that black and Hispanic children tend to be more insulin-resistant, they also discovered that black children compensate for that resistance differently from Hispanic children.
The study focuses renewed attention on the role that genetics, in concert with environmental factors such as diet and exercise, plays in the development of diabetes.
"This has potential implications for treatment," says Goran, associate director of the USC Institute for Prevention Research and specialist in childhood and adolescent obesity. "The bottom line is that there is no 'one-size-fits-all' approach to prevention and treatment for everyone."
When someone is resistant to insulin, that means that the tissues of his or her body become less sensitive to the action of insulin. Insulin is a natural hormone the body uses to bring glucose, or sugar, from the blood into its tissues to be used as an energy source.
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Unique cells in the pancreas, called beta cells, create that insulin. Scientists have shown that when someone becomes resistant to insulin-less efficient at using it-the body tries to compensate by putting more insulin into the blood stream.
Over time, insulin resistance can worsen and unused glucose can build up in the bloodstream-the disease process known as type 2 diabetes.
In the past, type 2 diabetes was primarily considered an adult disease. But physicians have noted that more teenagers and young adults are being diagnosed with type 2 diabetes.
The American Diabetes Association reports that this type of diabetes is twice as common in Hispanics and blacks as in non-Hispanic whites. About 1.2 million Mexican-Americans, or 10.6 percent of this population, and 2.8 million blacks, or 13 percent of this population, have the disease.
Goran and his colleagues looked at 57 healthy white children, Hispanic children and black children in Los Angeles and tested them for how efficiently their bodies' tissues responded to insulin. They also analyzed their body fat using a scanner (dual energy x-ray absorptionmetry, or DEXA).
Even after adjusting for body fat, both black and Hispanic children were more insulin-resistant than whites, but their bodies coped with the resistance differently, the team found.
Hispanic children tended to have more insulin circulating in their bloodstream because their bodies responded to resistance by pumping out lots of insulin, Goran says. But in black children, researchers found elevated insulin levels because the children's livers were removing less of the insulin from circulation in the body.
"This implies a potentially different disease mechanism," Goran says. Hispanics with insulin resistance may eventually develop diabetes because secreting too much insulin over time eventually exhausts their beta cells.
But among blacks, the liver appears to help keep insulin levels high in the blood by clearing less insulin from the body. As a result, the beta cells do not have to create more insulin. That means that blacks who end up with diabetes may develop it in a different way.
The study was part of a $3.5 million investigation funded by the National Institute of Diabetes and Digestive and Kidney Diseases into insulin resistance and diabetes development among Hispanic children as they mature.
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Michael I. Goran, Richard N. Bergman, Martha L. Cruz and Richard Watanabe, "Insulin Resistance and Associated Compensatory Responses in African-American and Hispanic Children," Diabetes Care. December 2002, Vol. 25, No. 12, pp. 2184-2190.
Source: University of Southern California