title: Sex-associated differences in free fatty acid flux of obese adolescents.
abstract: BACKGROUND
  In obesity, increases in free fatty acid (FFA) flux can predict development of insulin resistance. Adult women release more FFA relative to resting energy expenditure (REE) and have greater FFA clearance rates than men. In adolescents, it is unknown whether sex differences in FFA flux occur.
  
  
  OBJECTIVE
  Our objective was to determine the associations of sex, REE, and body composition with FFA kinetics in obese adolescents.
  
  
  METHODS
  Participants were from a convenience sample of 112 non-Hispanic white and black adolescents (31% male; age range, 12-18 years; body mass index SD score range, 1.6-3.1) studied before initiating obesity treatment.
  
  
  METHODS
  Glucose, insulin, and FFA were measured during insulin-modified frequently sampled iv glucose tolerance tests. Minimal models for glucose and FFA calculated insulin sensitivity index (SI) and FFA kinetics, including maximum (l0 + l2) and insulin-suppressed (l2) lipolysis rates, clearance rate constant (cf), and insulin concentration for 50% lipolysis suppression (ED50). Relationships of FFA measures to sex, REE, fat mass (FM), lean body mass (LBM) and visceral adipose tissue (VAT) were examined.
  
  
  RESULTS
  In models accounting for age, race, pubertal status, height, FM, and LBM, we found sex, pubertal status, age, and REE independently contributed to the prediction of l2 and l0 + l2 (P < .05). Sex and REE independently predicted ED50 (P < .05). Sex, FM/VAT, and LBM were independent predictors of cf. Girls had greater l2, l0 + l2 and ED50 (P < .05, adjusted for REE) and greater cf (P < .05, adjusted for FM or VAT) than boys.
  
  
  CONCLUSIONS
  Independent of the effects of REE and FM, FFA kinetics differ significantly in obese adolescent girls and boys, suggesting greater FFA flux among girls.
authors: Section on Growth and Obesity, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1103, USA.
authors: Diane C
authors: DC
authors: Adler-Wailes
authors: Vipul
authors: V
authors: Periwal
authors: Asem H
authors: AH
authors: Ali
authors: Sheila M
authors: SM
authors: Brady
authors: Jennifer R
authors: JR
authors: McDuffie
authors: Gabriel I
authors: GI
authors: Uwaifo
authors: Marian
authors: M
authors: Tanofsky-Kraff
authors: Christine G
authors: CG
authors: Salaita
authors: Van S
authors: VS
authors: Hubbard
authors: James C
authors: JC
authors: Reynolds
authors: Carson C
authors: CC
authors: Chow
authors: Anne E
authors: AE
authors: Sumner
authors: Jack A
authors: JA
authors: Yanovski
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001823:Body Composition / Q000502:physiology; D002648:Child; D004734:Energy Metabolism / Q000502:physiology; D005006:Ethnicity / Q000706:statistics & numerical data; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D005951:Glucose Tolerance Test / Q000379:methods; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism; D008297:Male; D009765:Obesity / Q000097:blood / Q000453:epidemiology / Q000208:ethnology / Q000378:metabolism*; D012727:Sex Characteristics
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose