Early warning of type II diabetes?

Early warning of Type II diabetes?

The Pima Indians of southern Arizona have the world's highest rate of Type II diabetes (SN: 6/2/90, p.350). More than 50 percent of Pimas aged 35 and older suffer from this non-insulin-dependent, adult-onset form of diabetes, which involves high blood sugar levels and causes such symptoms as blurry vision, numbness and drowsiness.

Now, evidence indicates that an early warning of Type II diabetes may appear among Pima children decades before the full-blown disease strikes.

In the new study, healthy, nondiabetic Pima youngsters showed significant levels of insulin resistance, a condition in which cells respond sluggishly to insulin's sugaar-uptake message (SN: 6/23/90, p.389). This finding fits with the notion that many people with insulin resistance eventually go on to develop full-fledged Type II diabetes, says Peter H. Bennett, who heads the Phoenix-based clinical research branch of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

David J. Pettitt of NIDDK's Phoenix branch compared 439 nondiabetic Pima children and young adults, aged 6 to 19, with 449 age-matched nondiabetic Caucasians living in Rochester, Minn. He and his colleagues discovered that, on average, the Pima youths had blood insulin levels 15 to 20 percent higher than their Caucasian peers. The finding, they say, suggests that Pima children are prone to insulin resistance.

"Already at this young age, [Pima] don't handle glucose as well," Pettitt told SCIENCE NEWS.

The new research raises the question of whether large numbers of Pimas are born with insulin resistance, Bennett says. The researchers plan to test Pima newborns to see if they have higher blood insulin levels than Caucasian infants, he adds.

The results also support the belief that some people inherit a predisposition to insulin resistance, comments diabetes researcher Jay S. Skyler of the University of Miami. If scientists can come up with drugs to combat insulin resistance, he says, they may be able to protect Pima children -- and others with the disorder -- from progressing to Type II diabetes.

Some scientists have suggested that Pimas might help strave off Type II diabetes by returning to their traditional low-fat, high-carbohydrate diet. Pettitt maintains that Pimas, both adults and children, can lower their diabetes risk by staying physically fit and lean. Adults who develop insulin resistance can sometimes reverse the condition through exercise or weight loss, Bennett says.

But other new findings suggest that weight control alone may not shield adult Pimas from Type II diabetes.

Marie A. Charles, who also works at NIDDK's Phoenix branch, reports that adult Pimas can develop moderately elevated blood sugar without gaining weight. Such elevations, although not technically considered diabetic, increase a person's risk of developing the disease within a few years.

Charles and her colleagues studied 309 non-obese Pima men and women, aged 18 to 77, who had normal blood sugar levels at the study's start. About seven years later, the researchers found that 51 (16.5 percent) of these individuals had developed moderately elevated, but still nondiabetic, blood sugar levels. OF that group, 21 had not gained weight since the study began. This discovery suggests that some people begin their slide toward Type II diabetes without putting on extra pounds, Charles says.

She and her co-workers suggest that other factors -- such as aging, physical inactivity or certain drugs -- may tip the balance in people who are genetically predisposed to insulin resistance, raising their blood sugar levels and eventually leading to full-fledged Type II diabetes.