Relationship between skeletal muscle MCT1 and accumulated exercise during voluntary wheel running

Abstract

. Relationship between skeletal muscle MCT1 and accumulated exercise during voluntary wheel running. J Appl Physiol 97: 527-534, 2004. First published April 23, 2004 10.1152/japplphysiol.01347.2003.-We examined whether the quantity of exercise performed influences the expression of monocarboxylate transporter (MCT) 1 and MCT4 in mouse skeletal muscles (plantaris, tibialis anterior, soleus) and heart. Wheel running exercise (1, 3, and 6 wk) was used, which results in marked variations in self-selected running activity. Differences in muscle MCT1 and MCT4 among animals, before the initiation of running, were not related to the quantity of exercise performed on the first day of wheel running. No changes in MCT4 were observed over the course of the study (P Ͼ 0.05). After 6 wk of running, were there significant increases in heart (50%; P Ͻ 0.05) and muscle MCT1 (31-60%; P Ͻ 0.05) but not after 1 and 3 wk (P Ͼ 0.05). Because skeletal muscle MCT1 and running distances varied considerably, we examined the relationship between these two parameters. Within the first week of training, MCT1 was negatively correlated with the accumulated running distance (r ϭ Ϫ0.70, P Ͻ 0.05). On further analysis, it appears that, in the first week, excessive running (Ͼ20 km/wk) represses MCT1 (Ϫ16.1%; P Ͻ 0.05), whereas more modest amounts of running (Ͻ20 km/wk) increase MCT1 (ϩ37%; P Ͻ 0.05). After 3 wk of running, a positive relationship was observed between MCT1 and running distance (r ϭ ϩ0.76), although there is a threshold that must be exceeded before an increase over the control animals occurs. Finally, in week 6, when MCT1 was increased in the tibialis anterior and plantaris muscles, there were no correlations with the accumulated running distances. These studies have shown that mild exercise training fails to increase MCT4 and that changes in MCT1 are complex, depending not only the accumulated exercise but also on the stage of training. lactate; plantaris; soleus; tibialis anterior; heart; distance; monocarboxylate transporter LACTATE IS NOT ONLY AN END product of glycolysis but also an oxidizable substrate. This monocarboxylate is produced primarily in fast-twitch skeletal muscle fibers, and it is oxidized in the heart and in oxidative muscle fibers. The productionoxidation cycle of lactate requires exchange of this substrate between muscle fibers and other muscles (2, 5, 49), as well as other tissues, including heart (4, 27, 28), liver (8), kidney (18,26,44), and adipose tissue (20), where lactate can be metabolized. The extrusion of lactate from the muscle cell and its uptake by other muscle cells occur via a facilitated transport system involving monocarboxylate transport (MCT) proteins. It is now confirmed that there is a family of eight or more MCTs (21). MCT isoforms are expressed in a tissue-specific manner (2, 5, 15-18, 20, 26, 28, 36, 38 -40, 42, 47, 49), and MCTs are also coexpressed within the same tissue (2,4,5,16,29,42,47,49). These latter observations suggest that MCTs may have different roles and/or transport capa...

Negligible direct lactate oxidation in subsarcolemmal and intermyofibrillar mitochondria obtained from red and white rat skeletal muscle

“…Antibodies against MCT2 were obtained from Chemicon International (Temecula, CA, USA). All of these MCT antibodies have been used in our previous work (Bonen et al 2000 b , 2006; Yoshida et al 2004). The monoclonal antibody MO25 (Matsuno et al 1996) was used to detect fatty acid translocase (FAT)/CD36.…”

Expression of monocarboxylate transporter (MCT) 1 and MCT4 in overloaded mice plantaris muscle

“…Proteins from muscles were separated using SDS-PAGE, and then MCT1 and MCT4 proteins were detected using western blotting as previously described [8,13]. Protein concentrations of homogenate samples were measured using a BCA protein assay kit (Pierce, Pittsburgh, PA, USA).…”

“…Protein concentrations of homogenate samples were measured using a BCA protein assay kit (Pierce, Pittsburgh, PA, USA). Antibodies against MCT1 and MCT4 were raised in rabbits against the oligopeptide corresponding to the C-terminal region of the respective MCT (Qiagen, Japan) and have been used in previous studies [8,13]. Total AMPK-a, phospho-AMPK-a (Thr172) antibodies were obtained from Cell Signaling.…”

“…As part of the lactate shuttle, MCT1 facilitates lactate uptake, while MCT4 facilitates lactate extrusion [2,6]. MCT1 protein content, but not MCT4, was shown to increase by chronic muscle stimulation [7] or voluntary wheel running [8], while high-intensity interval training [9] and strength training [10] are known to increase MCT4 protein expression. Therefore, the intensity of muscle stimulus appears to be important for the regulation of MCT4 in skeletal muscle.…”

Inward Flux of Lactate- through Monocarboxylate Transporters Contributes to Regulatory Volume Increase in Mouse Muscle Fibres

“…Intact, isolated single muscle fibres from mouse EDL and peroneus muscles were used [5], [26], [27]. These hindlimb skeletal muscles express NKCC1 [23], MCT1 and MCT4 [14], [24].…”