Abstract
Objective
To explain the predisposition for insulin resistance among African American (AA) adolescents,
this study aimed to: 1) examine changes in intramyocellular lipid content (IMCL),
and insulin sensitivity with intralipid (IL) infusion; and 2) determine whether the
increase in IMCL is comparable between AA and Caucasian adolescents.
Materials and Methods
Thirteen AA and 15 Caucasian normal-weight adolescents (BMI <85th) underwent a 3-h hyperinsulinemic–euglycemic clamp, on two occasions in random
order, after an overnight 12-h infusion of: 1) 20% IL and 2) normal saline (NS). IMCL
was quantified by 1H magnetic resonance spectroscopy in tibialis anterior muscle before and after IL
infusion.
Results
During IL infusion, plasma TG, glycerol, FFA and fat oxidation increased significantly,
with no race differences. Hepatic insulin sensitivity decreased with IL infusion with
no difference between the groups. IL infusion was associated with a significant increase
in IMCL, which was comparable between AA (Δ 105%; NS: 1.9±0.8 vs. IL: 3.9±1.6 mmol/kg wet weight) and Caucasian (Δ 86%; NS: 2.8±2.1 vs. IL: 5.2±2.4 mmol/kg wet weight), with similar reductions (P<0.01) in insulin sensitivity between the groups (Δ −44%: NS: 9.1±3.3 vs. IL: 5.1±1.8 mg/kg/min per μU/ml in AA) and (Δ −39%: NS: 12.9±6.0 vs. IL: 7.9±3.8 mg/kg/min per μU/ml in Caucasian) adolescents.
Conclusions
In healthy adolescents, an acute elevation in plasma FFA with IL infusion is accompanied
by significant increases in IMCL and reductions in insulin sensitivity with no race
differential. Our findings suggest that AA normal-weight adolescents are not more
susceptible than Caucasians to FFA-induced IMCL accumulation and insulin resistance.
Abbreviations:
AA (African American), C (Caucasian), IL (Intralipid), NS (Normal saline), IMCL (Intramyocellular lipid), TG (Triglyceride), FFA (Free fatty acids)Keywords
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Article info
Publication history
Published online: November 05, 2012
Accepted:
September 11,
2012
Received:
June 13,
2012
Identification
Copyright
© 2013 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
