High carbohydrate availability increases LCFA uptake and decreases LCFA oxidation in perfused muscle.

To determine whether changes in long-chain fatty acid (LCFA) oxidative metabolism induced by elevated intracellular carbohydrate availability are due to changes in LCFA uptake or in mitochondrial transport capacity, rat hindquarters were perfused with 500 microM palmitate and [1-14C]palmitate or [1-14C]octanoate as well as with either low (LG) or high (HG) carbohydrate availability. Glucose uptake was higher in the HG vs. LG group (23.

Increased fatty acid uptake and altered fatty acid metabolism in insulin-resistant muscle of obese Zucker rats.

Altered muscle fatty acid (FA) metabolism may contribute to the presence of muscle insulin resistance in the genetically obese Zucker rat. To determine whether FA uptake and disposal are altered in insulin-resistant muscle, we measured palmitate uptake, oxidation, and incorporation into di- and triglycerides in isolated rat hindquarters, as well as muscle plasma membrane fatty acid-binding protein (FABP(PM)) content of lean (n = 16, fa/+) and obese (n = 15, fa/fa) Zucker rats (12 weeks of age). Hindquarters were perfused with 7 mmol/l glucose, 1,000 micromol/l albumin-bound palmitate, and albumin-bound [1-(14)C]palmitate at rest (no insulin).

Muscle palmitate uptake and binding are saturable and inhibited by antibodies to FABP(PM).

Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABP(PM)) may be a component of this system. To test the hypothesis that FABP(PM) is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABP(PM). Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated Vmax values of 10.

Training-induced elevation in FABP(PM) is associated with increased palmitate use in contracting muscle.

To evaluate the effects of endurance training in rats on fatty acid metabolism, we measured the uptake and oxidation of palmitate in isolated rat hindquarters as well as the content of fatty acid-binding proteins in the plasma membranes (FABP(PM)) of red and white muscles from 16 trained (T) and 18 untrained (UT) rats. Hindquarters were perfused with 6 mM glucose, 1,800 microM palmitate, and [1-(14)C]palmitate at rest and during electrical stimulation (ES) for 25 min. FABP(PM) content was 43-226% higher in red than in white muscles and was increased by 55% in red muscles after training.