By Suzanne Rostler

NEW YORK, Nov 27 (Reuters Health) - Babies weighing less than 5.5 pounds (2.5 kilograms) at birth may be more likely to develop insulin resistance, a precursor to type 2 diabetes and heart disease, researchers report.

Their study found that insulin resistance syndrome (IRS), a condition marked by elevated levels of insulin in the blood, low HDL ("good") cholesterol, obesity and elevated blood fats, was more common among these low birth weight (LBW) babies by the time they reached the ages of 8 to 14. The association was even stronger for black children, according to the report in the December issue of Diabetes Care.

The findings suggest that fetal malnutrition can lead to permanent alterations of the beta cells, the insulin-producing cells of the pancreas. The results also underscore the importance of proper nutrition during pregnancy, report Dr. Chaoyang Li and colleagues from the University of Southern California in Los Angeles.

In an interview with Reuters Health, study author Dr. Michael J. Goran said the findings suggest another risk factor for type 2 diabetes.

"Screening for type 2 diabetes is important for children and adolescents, especially if they are overweight, have a positive family history of type 2 diabetes and are African American, Native American or Hispanic," Goran said. "On top of these risk factors we can now add low birth weight, especially for African-American children."

It is not clear why LBW was more strongly associated with insulin resistance among black children, but Goran suggested that an interaction between genetic and environmental factors may be at work. Alternatively, African Americans have been shown to have higher insulin secretion in general, and respond to insulin resistance by secreting even more insulin.

"Over-secretion may wear down the beta cells quicker," he said.

Researchers have long known that LBW boosts the risk of IRS, type 2 diabetes and heart disease among adults, but the association between birth weight and insulin resistance in children is unclear. To investigate, Goran and colleagues measured blood fats, blood sugar and insulin levels after an overnight fast in 139 children at four different times.

LBW was associated with higher fasting insulin, lower HDL cholesterol and increased abdominal fat among all children and significantly associated with these traits among African-American children.

"The findings suggest that hyperinsulinemia, decreased beta-cell function, (elevated blood fats) and central obesity, which are associated with LBW, might be the first components of IRS during childhood," the study authors conclude.

Although the study did not investigate how fetal malnutrition may contribute to insulin resistance, the findings indicate that impaired growth of the liver during pregnancy can contribute to a lifetime of problems metabolizing fat.

Goran recommends that future studies track normal birth weight and low birth weight children beyond puberty to determine whether the risk of developing type 2 diabetes persists. Studies examining the effects of weight loss and exercise on insulin sensitivity are also needed, he said in an interview.

SOURCE: Diabetes Care 2001;24:2035-2042.

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