Intrabdominal fat is related to metabolic risk factors in Hispanic Americans, African Americans, and in girls

The alarming rise in the prevalence of obesity among the pediatric population has become one of the most serious and urgent public health problems. Many of the metabolic complications associated with obesity are already present during childhood and are closely linked to risk for the development of type 2 diabetes and cardiovascular disease. Excess adiposity is strongly associated with reduced insulin sensitivity, impaired glucose tolerance, adverse lipid profiles and elevated blood pressure in both adult (1–3) and pediatric (4–8) populations. However, the location of the excess body fat may differentially influence the severity of metabolic complications. Intra-abdominal adipose tissue (IAAT), in particular, has been shown to be strongly correlated with insulin dynamics and lipid metabolism in adults (1;9;10). Studies in adult humans as well as in animal models indicate that compared to the subcutaneous fat depot, IAAT is a greater contributor to adverse cardiometabolic outcomes (1;9;10). Information on the adverse effects of IAAT in children, especially early pubertal children, is limited. Adipose tissue is preferentially deposited subcutaneously in early pubertal children and IAAT is relatively low among this group (6;11). However, it has been hypothesized that beginning in childhood, as excess fat begins to accumulate, lipid overflow leads to increasing fat deposition into the IAAT compartment that may initiate cardiometabolic complications (5;12). The regional distribution of adipose tissue appears to influence cardiometabolic outcomes, specifically glucose and lipid metabolism and blood pressure (1). It is not clear if specific fat depots contribute to cardiometabolic outcomes differently in children, particularly children of diverse racial/ethnic backgrounds. It has been clearly demonstrated that Hispanic and African Americans of every age group are disproportionately affected by cardiovascular disease and type 2 diabetes relative to their European American counterparts (13–15). Part of this ethnic discrepancy in disease risk may derive from ethnic differences in fat distribution. Racial/ethnic differences in body fat distribution as well as in metabolic risk factors have been identified in both adults and children. Hispanic American adults (5;16) and children (5) reportedly have greater IAAT than European Americans even when matched for total adiposity. More adverse cardiometabolic outcomes observed in Hispanic Americans relative to European Americans appears to be reflective of greater fat accumulation, particularly in the intra-abdominal compartment. Unlike Hispanics, African American adults and children have been consistently shown to have less IAAT than European Americans for a given total body fat (1;3;11;17;18). Further, greater risk for type 2 diabetes among African Americans vs. European Americans is independent of BMI (14). Taken together, these observations suggest that either there are factors unrelated to adiposity underlying metabolic risk, or that the threshold for an effect of a given adipose tissue depot on metabolic risk may be lower among African Americans. Few studies (4;6;11;19) have investigated the associations among fat depots and metabolic outcomes in children. To our knowledge no study has investigated these variables using robust measures of metabolism and body composition in a multi-ethnic cohort of early pubertal children. The aim of this study was to examine the associations of individual adipose depots with metabolic outcomes, and whether these associations vary by race/ethnicity or sex.