ATLANTA — Although there are no formal criteria defining metabolic syndrome in children, African American and white children show important differences in some of the components, Dr. Silva A. Arslanian said at the annual meeting of the International Society on Hypertension in Blacks.
A series of studies by Dr. Arslanian of the University of Pittsburgh and her colleagues have demonstrated that black children have lower insulin sensitivity and higher insulin secretion than do their white peers. Black children are more prone to fat accretion because of lower rates of lipolysis. And they have a limited capacity to increase insulin secretion in response to decreased insulin sensitivity.
Moreover, obese black adolescents are worse off than their white peers with respect to their diabetogenic risk profile, but better off with respect to their atherogenic risk profile.
Dr. Arslanian's research strategy is to recruit black and white children, match them on the basis of various demographic and physiologic factors, and admit them overnight to the children's research center one or more times for measurement of insulin secretion, insulin sensitivity, and other factors.
In one study, she compared 22 black with 22 white 10-year-olds with matching body mass indexes, fat composition, and visceral adipose tissue. Their average BMIs were about 18 kg/m
The product of insulin sensitivity multiplied by first-phase insulin is known as the glucose disposition index (GDI), and in most populations the GDI is constant. But the black children had a significantly higher average GDI than the white children, suggesting an inherent hypersecretion of insulin. It is not clear whether this is the result of genetic differences between the populations, environmental differences, or both.
In a more recent study, Dr. Arslanian and colleagues compared adiponectin levels and body composition in 83 African American and 78 white children, aged 8–17 years, with BMIs ranging from 14 to 50 (Diabetes Care 2006;29:51–6). Adipo- nectin levels were lower in the African American children even after controlling for Tanner stage, sex, abdominal subcutaneous and visceral adipose tissue, and leptin levels. African American children also had lower amounts of visceral fat.
In agreement with previous studies, the African Americans had lower average insulin sensitivity than the whites, but this difference disappeared after the investigators controlled for adiponectin levels. Together these findings suggest that adiponectin level is a strong marker of insulin sensitivity, and that the lower adiponectin level in African American youth may predispose them to a greater risk of insulin resistance despite lower visceral fat.