title: Levels of free fatty acids (FFA) are associated with insulin resistance but do not explain the relationship between adiposity and insulin resistance in Hispanic Americans: the IRAS Family Study.
abstract: OBJECTIVE
  We investigated whether free fatty acids (FFA) mediate the association between adiposity and insulin resistance in the Hispanic-American families of the Insulin Resistance Atherosclerosis Family Study.
  
  
  METHODS
  In 815 Hispanic individuals in the Insulin Resistance Atherosclerosis Family Study, we tested for association between the following: 1) levels of adiposity [body mass index (BMI), visceral and sc adipose tissue area (VAT and SAT)] and circulating levels of FFA; 2) levels of circulating FFA and insulin sensitivity (S(I)); and 3) levels of adiposity and S(I), additionally testing to see whether levels of FFA mediated or modified the relationship between adiposity and S(I.)
  
  
  RESULTS
  After adjusting for age, sex, clinic site, and admixture, increasing levels of BMI, VAT, and SAT were weakly associated with increasing levels of circulating FFA (BMI: P = 0.024; VAT: P = 2.33 × 10(-3); SAT: P = 0.018; percent variation explained: ∼1.00%). Increasing levels of circulating FFA were associated with decreasing S(I) (P = 8.10 × 10(-11)). Increasing BMI, VAT, and SAT were also associated with decreasing S(I) (BMI: P = 4.98 × 10(-71); VAT: P = 1.48 × 10(-64); SAT: P = 4.21 × 10(-62)), but this relationship was not significantly mediated by FFA. VAT, but not BMI or SAT, interacts with levels of FFA to influence S(I) (P = 0.021).
  
  
  CONCLUSIONS
  Although levels of circulating FFA are associated both with increasing adiposity and decreasing S(I), they do not appear to mediate the association between levels of adiposity and S(I) in this large cohort of Hispanic-Americans. These results may indicate that FFA contribute to insulin resistance independent of adiposity.
authors: Department of Epidemiology, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado 80045, USA.
authors: Melissa R
authors: MR
authors: Miller
authors: Rocio I
authors: RI
authors: Pereira
authors: Carl D
authors: CD
authors: Langefeld
authors: Carlos
authors: C
authors: Lorenzo
authors: Jerome I
authors: JI
authors: Rotter
authors: Yii-Der Ida
authors: YD
authors: Chen
authors: Richard N
authors: RN
authors: Bergman
authors: Lynne E
authors: LE
authors: Wagenknecht
authors: Jill M
authors: JM
authors: Norris
authors: Tasha E
authors: TE
authors: Fingerlin
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D050154:Adiposity / Q000235:genetics / Q000502:physiology*; D000328:Adult; D001786:Blood Glucose / Q000502:physiology; D015992:Body Mass Index; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D005838:Genotype; D006630:Hispanic or Latino / Q000235:genetics / Q000706:statistics & numerical data*; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000235:genetics / Q000502:physiology*; D016013:Likelihood Functions; D008055:Lipids / Q000097:blood; D008297:Male; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D013781:Texas / Q000453:epidemiology; D014057:Tomography, X-Ray Computed
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008055:Lipids