(The FASEB Journal. 2008;22:948.3)
© 2008 FASEB
(The FASEB Journal. 2008;22:948.3.)
© 2008 FASEB
Quantification of muscle lipid kinetics in obese and lean rabbits
Xiao-jun Zhang1,
David L Chinkes1,
Asle Aarsland2,
David N Herndon3 and
Robert R Wolfe4
1 Metabolism/Surgery
2 Metabolism/Anesthesiology
3 Surgery, Shriners Hospital for Children and University of Texas Medical Branch, Galveston, TX
4 Geriatrics, University of Arkansas Medical School, Little Rock, AR
ABSTRACT
We compared lipid kinetics in obese and lean muscle in rabbits. A novel mathematical model was used to quantify muscle lipid kinetics by infusing U-13C16-palmitate and using palmitoyl-carnitine as the precursor for lipid synthesis and oxidation, as we previously found that the palmitoyl-carnitine enrichment is in equilibrium with that of palmitoyl-CoA. Young rabbits were fed either a high-fat diet (n = 6) or restricted food (n = 4). After 10-weeks feeding the obese rabbits had greater body weight than the lean counterparts (5.3 ± 0.1 vs. 3.9 ± 0.2 kg, p<0.001). The tracer was infused for 8 h under general anesthesia; blood and leg muscle were sampled. Triglyceride (TG) content was greater in obese than in lean muscle (36.2 ± 2.8 vs. 8.8 ± 4.0 µmol /g, p<0.01), whereas muscle phospholipid (PL) contents were similar (2.1 ± 0.9 vs. 1.7 ± 0.7 µmol/g, p = 0.21). TG synthesis and oxidation rates in obese muscle were 0.0529 ± 0.0416 and 0.0582 ± 0.0345 µmol/g/h, which were greater (p<0.01) than the corresponding values of 0.0114 ± 0.0083 and 0.0098 ± 0.0039 µmol/g/h in lean muscle. In contrast, the synthetic rates of muscle PL were close (0.0141 ± 0.0058 vs. 0.0109 ± 0.0036 µmol/g/h, p = 0.22). In summary, the obese muscle contained more TG and comparable PL in comparison with lean muscle. The obese muscle had faster rates of TG synthesis and oxidation, suggesting that it consumed more lipid. This new model could be useful in the study of obesity.
