Abstract
Objective
To investigate the effect of acute hyperinsulinemia and the resulting decrease in
plasma free fatty acid (FFA) concentrations on intramuscular TG synthesis.
Materials/Methods
U-13C16-palmitate was infused for 3 h in anesthetized rabbits after overnight food deprivation.
Arterial blood and leg muscle were sampled during the tracer infusion. Plasma samples
were analyzed for free and TG-bound palmitate enrichments and concentrations. The
enrichments and concentrations of palmitoyl-CoA and palmitoyl-carnitine as well as
the enrichment of palmitate bound to TG were measured in muscle samples. Fractional
synthetic rate (FSR) of intramuscular TG was calculated using the tracer incorporation
method. The rabbits were divided into a control group and a hyperinsulinemic euglycemic
clamp group. Insulin infusion decreased the rate of appearance of plasma free palmitate
(2.00±0.15 vs 0.68±0.20 μmol⋅kg−1⋅min−1; P<.001), decreased plasma FFA concentration (327±61 vs 72±25 nmol/mL; P<.01), decreased the total concentration of intramuscular fatty acyl-CoA plus fatty
acyl-carnitine (12.1±1.6 vs 7.0±0.7 nmol/g; P<.05), and decreased intramuscular TG FSR (0.48±0.05 vs 0.21±0.06%/h; P<.01) in comparison with the control group. Intramuscular TG FSR was correlated (P<.01) with both plasma FFA concentrations and intramuscular fatty acyl-CoA concentrations.
Conclusions
Fatty acid availability is a determinant of intramuscular TG synthesis. Insulin infusion
decreases plasma and intramuscular fatty acid availability and thereby decreases TG
synthesis.
Abbreviations:
IM (intramuscular), TG (triglyceride), FFA (free fatty acid(s)), CoA (coenzyme A), PalCoA (palmitoyl-CoA), PalCn (palmitoyl-carnitine), PL (phospholipids(s)), FSR (fractional synthetic rate(s)), GC-MS (gas chromatograph-mass spectrometer)Keywords
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Article info
Publication history
Published online: August 14, 2012
Accepted:
June 5,
2012
Received:
March 2,
2012
Identification
Copyright
© 2013 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
