The carnitine status does not affect the contractile and metabolic phenotype of skeletal muscle in pigs

Abstract

BackgroundRecently, supplementation of L-carnitine to obese rats was found to improve the carnitine status and to counteract an obesity-induced muscle fiber transition from type I to type II. However, it has not been resolved if the change of muscle fiber distribution induced in obese rats and the restoration of the “normal” muscle fiber distribution, which is found in lean rats, in obese rats by supplemental L-carnitine is causally linked with the carnitine status. In the present study we hypothesized that fiber type distribution in skeletal muscle is dependent on carnitine status.MethodsTo test this, an experiment with 48 piglets which were randomly allocated to four groups (n = 12) was performed. All piglets were given orally either 60 mg sodium bicarbonate/kg body weight (group CON), 20 mg L-carnitine and 60 mg sodium bicarbonate/kg body weight (group CARN), 30 mg pivalate (dissolved in sodium bicarbonate)/kg body weight (group PIV) or 20 mg L-carnitine and 30 mg pivalate/kg body weight (group CARN + PIV) each day for a period of 4 weeks.ResultsConcentrations of total carnitine in plasma, liver and longissimus dorsi and biceps femoris muscles were 2.0–2.7 fold higher in group CARN than in group CON, whereas these concentrations were 1.9–2.5-fold lower in group PIV than in group CON. The concentrations of total carnitine in these tissues did not statistically differ between group CARN + PIV and group CON. Fiber type distribution of longissimus dorsi and biceps femoris muscles, mRNA and protein levels of molecular regulators of fiber distribution in longissimus dorsi and biceps femoris muscles and mRNA levels of genes reflecting the metabolic phenotype of longissimus dorsi and biceps femoris muscles did not differ between groups.ConclusionChanges in the systemic carnitine status and the muscle carnitine concentration induced by either supplementing L-carnitine or administering pivalate have no impact on the contractile and metabolic phenotype of skeletal muscles in pigs.

Effect of lifelong carnitine supplementation on plasma and tissue carnitine status, hepatic lipid metabolism and stress signalling pathways and skeletal muscle transcriptome in mice at advanced age

“…Nonetheless, species differences exist with regard to the effect of exogenous carnitine on muscle carnitine content. In pigs, feeding the same dose of supplemental carnitine as in the present study for only 3-4 weeks increased the concentration of free carnitine and acetylcarnitine in skeletal muscle by greater than 2•5-fold (47,48) . Although the exact reason for these species differences is unknown, it could be speculated that pig muscle has a higher capacity for carnitine uptake from plasma due to higher expression level of Octn2 in skeletal muscle than in rodents and humans.…”

Basic mechanisms of the regulation of L‐carnitine status in monogastrics and efficacy of L‐carnitine as a feed additive in pigs and poultry

“…After a 20‐day‐feeding period, the concentration of total L‐carnitine in plasma of the pigs was dose dependently increased up to 5.1‐fold at the highest level of supplemental L‐carnitine in the diet (1000 mg/kg diet; Fischer, Varady et al., ). Apart from plasma L‐carnitine, tissue L‐carnitine concentrations show a marked response to supplementation of dietary L‐carnitine in pigs (Doberenz, Birkenfeld, Kluge, & Eder, ; Fischer, Varady et al., ; Kaup et al., ; Keller et al., ; Ramanau et al., ). For instance, in the above‐mentioned study with growing pigs (Fischer, Varady et al., ), the concentration of total L‐carnitine in skeletal muscle, liver, kidney and heart was increased with increasing level of supplemental L‐carnitine and reached the 3.6–5.6 fold of that of non‐supplemented control pigs at a L‐carnitine concentration of 1000 mg/kg diet.…”

“…This should be taken into account, because it is well‐known from certain species, such as rats and humans, that even high doses of supplemental L‐carnitine cause either no or only a slight increase of muscle L‐carnitine concentration (Barnett et al., ; Ringseis, Lüdi et al., ). In contrast, in pigs the muscle L‐carnitine concentration shows a marked response to supplemental L‐carnitine (Fischer, Varady et al., ; Kaup et al., ; Keller et al., ). Future studies have to clarify if broiler chickens are “hyper”‐ (e.g., pigs)—or “hypo”‐responders (e.g., rats, humans) to supplemental L‐carnitine.…”

Nicotinic Acid Improves Endurance Performance of Mice Subjected to Treadmill Exercise

“…The GN muscle of all mice was crosscut in the middle of the muscle belly into two halves and one half was embedded in Tissue Tek optimal cutting temperature (O.C.T.) compound (Sakura Finetek Germany GmbH, Staufen, Germany), frozen in liquid nitrogen and cut into serial 10 µm thick cross-sections with a microtome (Microm HM 500, Microm International, Walldorf, Germany) maintained at −20 • C. Fiber typing was carried out based on myosin heavy chain (MHC) distribution using multicolor immunofluorescence analysis as described recently by our group [29]. Two sequential cross-sections of each muscle sample were stained with two different primary antibody cocktails (1 and 2) in order to discriminate the four fiber types.…”

“…Cross-sections were washed again with 1x PBS, and then mounted in Aqua Polymount (Polyscience, Niles, Illinois) and covered with coverslips. Visualization of slides was carried out with a DM 5500 B fluorescence microscope from Leica (Wetzlar, Germany) equipped with appropriate red, green and blue filters [29], a Leica DFC340FX camera and the Leica LAS AF microscope software. Individual images were taken from the slides with each filter and a composite image was assembled automatically from the images taken with the three filters.…”