Three in 10 pre-teens in the University of Southern California Study of Latinos at Risk (SOLAR) Diabetes Project have the metabolic syndrome, a clustering of risk factors for type 2 diabetes and cardiovascular disease, according to investigators from the Keck School of Medicine of USC. Results appear in the January 2004 issue of the Journal of Clinical Endocrinology & Metabolism.
The metabolic syndrome comprises numerous risk factors: high blood pressure, low levels of high-density lipoprotein (HDL, the so-called "good" cholesterol), central obesity, elevated triglycerides (another fat linked to heart disease) and impaired glucose tolerance (abnormally high blood sugar levels, also called pre-diabetes). The syndrome significantly increases risk of developing type 2 diabetes and cardiovascular disease.
Researchers suspect that this is because obesity is particularly common among Latinos-35 percent of young Latinos are overweight, about twice the proportion a decade ago. Obesity, in turn, is associated with insulin resistance, which is linked to metabolic changes and heightened disease risk.
"Obesity is now a critical, common nutritional problem in children," says Michael I. Goran, Ph.D., professor of preventive medicine and physiology and biophysics at the Keck School and a study author. "These studies show that the likely common pathway linking obesity to increased risk for type 2 diabetes and cardiovascular disease is insulin resistance. Our results show that this link is established early in life."
Researchers examined 126 overweight Latino boys and girls ages 8 to 13 with a family history of type 2 diabetes who were enrolled in SOLAR, a long-term study exploring risk factors for development of type 2 diabetes in at-risk adolescents.
Type 2 diabetes is a metabolic problem that results when the body cannot make enough insulin or its cells become less sensitive to insulin or resistant to it. Insulin is a hormone the body uses to bring glucose, or sugar, from the blood into tissues to be used as an energy source.
The researchers found that as children's sensitivity to insulin decreased, the number of components of the metabolic syndrome increased. Higher insulin sensitivity was tied to higher HDL, and lower insulin sensitivity was linked to higher triglyceride levels and blood pressure. Interestingly this was independent of degree of fatness. In other words, decreased insulin sensitivity is driving the metabolic disorders observed in overweight children. Therefore, increasing insulin sensitivity in these children, researchers suggest, appears to be crucial for preventing chronic disease.
In the same issue of the journal, the researchers also report how close many Latino pre-teens already are to developing type 2 diabetes.
Nearly three in ten of the children in SOLAR-about 28 percent-already has impaired glucose tolerance, or what is now termed pre-diabetes. Although such blood sugar levels are not high enough to denote diabetes, they indicate a heightened risk for developing type 2 diabetes.
The children with pre-diabetes tended to have poor beta-cell function, which showed signs of deterioration with age. Beta cells are special cells in the pancreas that create insulin. Scientists believe that when these cells work too hard over time, as they do in insulin resistance, they may wear out.
Diabetes is characterized by beta cell failure, but the research suggests that beta cell function starts declining significantly before diabetes is diagnosed. Therefore, Goran says, "Developing screening tools of beta-cell function in high-risk children may be important to identify those children at greatest risk."
Impaired glucose tolerance was especially common among children whose mothers developed type 2 diabetes during pregnancy, also called gestational diabetes. Children of mothers with gestational diabetes may face high exposures to insulin in utero.
SOLAR is supported by a grant from National Institute of Diabetes and Digestive and Kidney Diseases.
Martha L. Cruz, Marc J. Weigensberg, Terry T.-K. Huang, Geoff Ball, Gabriel Q. Shaibi and Michael I. Goran, "The Metabolic Syndrome in Overweight Hispanic Youth and the Role of Insulin Sensitivity," Journal of Clinical Endocrinology & Metabolism. January 2004, Vol. 89, No. 1.
Michael I. Goran, Richard N. Bergman, Quintilia Avila, Michael Watkins, Geoff D.C. Ball, Gabriel Q. Shaibi, Marc J. Weigensberg and Martha L. Cruz, "Impaired Glucose Tolerance and Reduced (-Cell Function in Overweight Latino Children with a Positive Family History for Type 2 Diabetes," Journal of Clinical Endocrinology & Metabolism. January 2004, Vol. 89, No. 1.