Acylcarnitine ester utilization by the hindlimb of warmblood horses at rest and following low intensity exercise and carnitine supplementation

Abstract

Background: Acylcarnitines play an important role in fuel metabolism in skeletal muscle. Objective: To assess acylcarnitine ester utilization by the hindlimb of horses at rest and following low intensity exercise and carnitine supplementation. Animals and methods: Acylcarnitine ester uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 § 3 (SD) years and weighing 538 § 39 kg) was collected simultaneously from the transverse facial artery and from the caudal vena cava. Food was withheld for 12 hours prior to exercise. Exercise comprised a standardized treadmill protocol consisting of 5 minutes of walk, 20 minutes of trot and thereafter another 5 minutes of walk. At the end of the first exercise day, three horses were given carnitine supplementation (100 mg/kg bodyweight), whereas the other horses received saline. The next day the exercise was repeated and blood samples collected similarly. Free carnitine and acylcarnitines were analyzed as their butyl ester derivatives in heparinized plasma by electrospray tandem mass spectrometry. Statistical analysis was performed using a general linear mixed model. Results: C3-carnitine, C6-carnitine and C14:1-carnitine showed the largest average extraction by the hindlimb at rest and C3-carnitine, C5:1-carnitine and C16-carnitine immediately after low-intensity exercise. Carnitine supplementation significantly increased free carnitine, C5-carnitine and C8-carnitine extraction. Conclusion: Carnitine supplementation altered the extraction of acylcarnitines by the hindlimb in horses exercising at low intensity. Clinical importance: Findings might aid in optimizing performance and myopathy prevention of the equine athlete.

Effect of Oral Supplementation with L-Carnitine on Performance Time in a 5000 m Race and Responses of Free Fatty Acid and Carnitine Concentrations in Trained-Endurance Athletes

“…It has been reported that elevation in plasma fatty acid availability prior to exercise could reduce utilization of muscle glycogen (Brass & Hiatt, 1998;Smith et al, 2008), which promotes an important pathway to spare glycogen stores (Wall et al, 2013;Brass & Hiatt, 1998;Kashef & Saei, 2017) and subsequent improvement in endurance capacity. However, the fatty acid oxidation ratio is decreased when an exercise intensity exceeds 70% VO 2max (Wall et al, 2013), and glycolysis is increased (Peters et al, 2015;Wall al., 2013). This results in depletion of glycogen stores and subsequent exercise cessation.…”

“…This results in depletion of glycogen stores and subsequent exercise cessation. In-line, L -carnitine is an indispensable compound for mitochondrial energy source by transporting long-chain fatty acids across the mitochondrial inner membrane as acyl-carnitine esters (Peters et al, 2015;Siddiqui et al, 2015), by regulating COA homeostasis (Miklos et al, 2016), by buffering toxic acyl-COA (Broad et al, 2006;Peters et al, 2015), by serving as a source of acetyl-L -carnitine, acetylcholine, and L -glutamate, in which they contribute to energy-producing reactions (Zhang et al, 2012), and by stimulating nitric oxide production (Miklos et al, 2016), in which it enhances pulmonary gas exchange and acts as a vasodilator and therefore increased blood flow (Verges, Flore, Favri-Juvin, Lévy, & Wuyam, 2005).…”

“…Oral supplementation with L -carnitine is used by endurance athletes to increase its content in skeletal muscle, increase fatty acid oxidation during exercise (Brass, & Hiatt, 1998), decrease toxic acyl groups (Peters et al, 2015;Stumpf et al, 1985), maintain the activity of pyruvate dehydrogenase (Brass, & Hiatt, 1998), preserve muscle glycogen, and delay muscular fatigue (Brass, & Hiatt, 1998;Smith, Fry, Tschume, & Bloomer, 2008;Wall et al, 2013). The increased use of fatty acids for energy production during prolonged exercise is beneficial to runners because it reduces muscle glycogen and thus increases aerobic capacity.…”