title: Interethnic differences in muscle, liver and abdominal fat partitioning in obese adolescents.
abstract: The prevalence of insulin resistance and type 2 diabetes (T2D) in obese youth is rapidly increasing, especially in Hispanics and African Americans compared to Caucasians. Insulin resistance is known to be associated with increases in intramyocellular (IMCL) and hepatic fat content. We determined if there are ethnic differences in IMCL and hepatic fat content in a multiethnic cohort of 55 obese adolescents. We used (1)H magnetic resonance spectroscopy (MRS) to quantify IMCL levels in the soleus muscle, oral glucose tolerance testing to estimate insulin sensitivity, magnetic resonance imaging (MRI) to measure abdominal fat distribution. Liver fat content was measured by fast-MRI. Despite similar age and % total body fat among the groups, IMCL was significantly higher in the Hispanics (1.71% [1.43%, 2.0%]) than in the African-Americans (1.04% [0.75%, 1.34%], p = 0.013) and the Caucasians (1.2% [0.94%, 1.5%], p = 0.04). Liver fat content was undetectable in the African Americans whereas it was two fold higher than normal in both Caucasians and Hispanics. Visceral fat was significantly lower in African Americans (41.5 cm(2) [34.6, 49.6]) and was similar in Caucasians (65.2 cm(2) [55.9, 76.0]) and Hispanics (70.5 cm(2) [59.9, 83.1]). In a multiple regression analysis, we found that ethnicity independent of age, gender and % body fat accounts for 10% of the difference in IMCL. Our study indicates that obese Hispanic adolescents have a greater IMCL lipid content than both Caucasians and African Americans, of comparable weight, age and gender. Excessive accumulation of fat in the liver was found in both Caucasian and Hispanic groups as opposed to virtually undetectable levels in the African Americans. Thus, irrespective of obesity, there seem to be some clear ethnic differences in the amount of lipid accumulated in skeletal muscle, liver and abdominal cavity.
authors.affiliation: Department of Pediatrics, Internal Medicine, the Howard Hughes Institute, and the General Clinical Research Center of the Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Liska
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dufour
authors.forename: Tosca L
authors.initials: TL
authors.lastname: Zern
authors.forename: Sara
authors.initials: S
authors.lastname: Taksali
authors.forename: Anna M G
authors.initials: AM
authors.lastname: Calí
authors.forename: James
authors.initials: J
authors.lastname: Dziura
authors.forename: Gerald I
authors.initials: GI
authors.lastname: Shulman
authors.forename: Bridget M
authors.initials: BM
authors.lastname: Pierpont
authors.forename: Sonia
authors.initials: S
authors.lastname: Caprio
mesh_terms: D050153:Abdominal Fat / Q000378:metabolism*; D000293:Adolescent; D044383:Black People / Q000208:ethnology; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D005951:Glucose Tolerance Test; D006630:Hispanic or Latino / Q000208:ethnology; D006801:Humans; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000208:ethnology* / Q000503:physiopathology*; D014280:Triglycerides / Q000378:metabolism; D044465:White People / Q000208:ethnology; D001741:Black or African American
chemical_list: D014280:Triglycerides