Gene test foretells Type I diabetes risk.

Gene test foretells Type I diabetes risk

Scientists have developed a genetic test to predict a person's risk of developing Type I diabetes, the disorder's most serious form. The new test may help identify children with an inherited tendency to develop the disease.

Developed by Massimo Trucco and his colleagues at the University of Pittsburgh School of Medicine, the test may eventually permit doctors to intervene before damage occurs. As yet there is no cure for the disease, but researchers hope to perfect some type of immunosuppressive drug therapy in the fugure. Type I diabetes is thought to arise when immune cells mistakenly attack and destory pancreatic beta cells. Beta cells produce insulin, the hormone needed to utilize sugar.

Trucco's test, unveiled this week at the meeting of the American Diabetes Association in Detroit, involves analyzing DNA taken from white blood cells. It doesn't diagnose Type I diabetes but picks out individuals who are likely to get the disease if they encounter a triggering factor. Scientists believe people inherit a tendency to develop Type I diabetes but that the actual disease must be set off by exposure to a virus or some other factor in the environment.

Confirmation of the test's accuracy should enable physicians to determine whether children in families with a history of Type I diabetes have a high risk of the disease, says Charles M. Clark Jr. of the Indiana University School of Medicine in Indianapolis. This knowledge could alert doctors and parents to watch for early signs of the disease, which often mimic the flu, he notes. Many children now are rushed to the emergency room in a diabetic coma because their symptoms went unrecognized, Trucco adds.

In the future, the test might enable physicians to begin immunosuppressive therapy early, Trucco says.

An antibody test developed last year detects the disease after beta-cell destruction has begun but before overt symptoms appear (SN: 6/18/88, p.389). Trucco's test predicts a person's risk before cell destruction takes place.

His work builds on research showing Type I diabetics have a genetic flaw resulting in the substitution of an amino acid occupying a specific position in a type of human leukocyte antigen protein (SN: 10/17/87, p.247). Researchers believe this amino acid, aspartic acid, protects against Type I diabetes by preventing immune cells from attaching to beta cells.

Trucco looks at a portion of the gene that codes for aspartic acid. People who have a specific alteration of the gene, he says, are 107 times more likely than others to develop Type I diabetes.