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1
Bonen, Arend, Miriam Heynen, and Hideo Hatta. "Distribution of monocarboxylate transporters MCT1-MCT8 in rat tissues and human skeletal muscle." Applied Physiology, Nutrition, and Metabolism 31, no. 1 (February 1, 2006): 31–39. http://dx.doi.org/10.1139/h05-002.
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In the past decade, a family of monocarboxylate transporters (MCTs) have been identified that can potentially transport lactate, pyruvate, ketone bodies, and branched-chain ketoacids. Currently, 14 such MCTs are known. However, many orphan transporters exist that have transport capacities that remain to be determined. In addition, the tissue distribution of many of these MCTs is not well defined. Such a cataloging can, at times, begin to suggest the metabolic role of a particular MCT. Recently, a number of antibodies against selected MCTs (MCT1, -2, -4, and -5 to -8) have become commercially available. Therefore, we examined the protein expression of these MCTs in a large number of rat tissues (heart, skeletal muscle, skin, brain, testes, vas deferens, adipose tissue, liver, kidney, spleen, and pancreas), as well as in human skeletal muscle. Unexpectedly, many tissues coexpressed 4-5 MCTs. In particular, in rat skeletal muscle MCT1, MCT2, MCT4, MCT5, and MCT6 were observed. In human muscle, these same MCTs were present. We also observed a pronounced MCT7 signal in human muscle, whereas a very faint signal occurred for MCT8. In rat heart, which is an important metabolic sink for lactate, we confirmed that MCT1 and -2 were expressed. In addition, MCT6 and -8 were also prominently expressed in this tissue, although it is known that MCT8 does not transport aromatic amino acids or lactate. This catalog of MCTs in skeletal muscle and other tissues has revealed an unexpected complexity of coexpression, which makes it difficult to associate changes in monocarboxylate transport with the expression of a particular MCT. The differences in transport kinetics for lactate and pyruvate are only known for MCT1, -2 and -4. Transport kinetics remain to be established for many other MCTs. In conclusion, this study suggests that in skeletal muscle, as well as other tissues, lactate and pyruvate transport rates may not only involve MCT1 and -4, as other monocarboxylate transporters are also expressed in rat (MCT2, -5, -6) and human skeletal muscle (MCT2, -5, -6, -7).Key words: muscle, lactate, pyruvate, human, rat.
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PRICE, T. Nigel, N. Vicky JACKSON, and P. Andrew HALESTRAP. "Cloning and sequencing of four new mammalian monocarboxylate transporter (MCT) homologues confirms the existence of a transporter family with an ancient past." Biochemical Journal 329, no. 2 (January 15, 1998): 321–28. http://dx.doi.org/10.1042/bj3290321.
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Measurement of monocarboxylate transport kinetics in a range of cell types has provided strong circumstantial evidence for a family of monocarboxylate transporters (MCTs). Two mammalian MCT isoforms (MCT1 and MCT2) and a chicken isoform (REMP or MCT3) have already been cloned, sequenced and expressed, and another MCT-like sequence (XPCT) has been identified. Here we report the identification of new human MCT homologues in the database of expression sequence tags and the cloning and sequencing of four new full-length MCT-like sequences from human cDNA libraries, which we have denoted MCT3, MCT4, MCT5 and MCT6. Northern blotting revealed a unique tissue distribution for the expression of mRNA for each of the seven putative MCT isoforms (MCT1-MCT6 and XPCT). All sequences were predicted to have 12 transmembrane (TM) helical domains with a large intracellular loop between TM6 and TM7. Multiple sequence alignments showed identities ranging from 20% to 55%, with the greatest conservation in the predicted TM regions and more variation in the C-terminal than the N-terminal region. Searching of additional sequence databases identified candidate MCT homologues from the yeast Saccharomyces cerevisiae, the nematode worm Caenorhabditis elegans and the archaebacterium Sulfolobus solfataricus. Together these sequences constitute a new family of transporters with some strongly conserved sequence motifs, the possible functions of which are discussed.
3
Becker, Helen M., Nilufar Mohebbi, Angelica Perna, Vadivel Ganapathy, Giovambattista Capasso, and Carsten A. Wagner. "Localization of members of MCT monocarboxylate transporter family Slc16 in the kidney and regulation during metabolic acidosis." American Journal of Physiology-Renal Physiology 299, no. 1 (July 2010): F141—F154. http://dx.doi.org/10.1152/ajprenal.00488.2009.
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The monocarboxylate transporter family (MCT) comprises 14 members with distinct transport properties and tissue distribution. The kidney expresses several members of the MCT family, but only little is known about their exact distribution and function. Here, we investigated selected members of the MCT family in the mouse kidney. MCT1, MCT2, MCT7, and MCT8 localized to basolateral membranes of the epithelial cells lining the nephron. MCT1 and MCT8 were detected in proximal tubule cells whereas MCT7 and MCT2 were located in the thick ascending limb and the distal tubule. CD147, a β-subunit of MCT1 and MCT4, showed partially overlapping expression with MCT1 and MCT2. However, CD147 was also found in intercalated cells. We also detected SMCT1 and SMCT2, two Na+-dependent monocarboxylate cotransporters, on the luminal membrane of type A intercalated cells. Moreover, mice were given an acid load for 2 and 7 days. Acidotic animals showed a marked but transient increase in urinary lactate excretion. During acidosis, a downregulation of MCT1, MCT8, and SMCT2 was observed at the mRNA level, whereas MCT7 and SMCT1 showed increased mRNA abundance. Only MCT7 showed lower protein abundance whereas all other transporters remained unchanged. In summary, we describe for the first time the localization of various MCT transporters in mammalian kidney and demonstrate that metabolic acidosis induces a transient increase in urinary lactate excretion paralleled by lower MCT7 protein expression.
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Chidlow, Glyn, John P. M. Wood, Mark Graham, and Neville N. Osborne. "Expression of monocarboxylate transporters in rat ocular tissues." American Journal of Physiology-Cell Physiology 288, no. 2 (February 2005): C416—C428. http://dx.doi.org/10.1152/ajpcell.00037.2004.
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The aim of the present study was to determine the distribution of monocarboxylate transporter (MCT) subtypes 1-4 in the various structures of the rat eye by using a combination of conventional and real-time RT-PCR, immunoblotting, and immunohistochemistry. Retinal samples expressed mRNAs encoding all four MCTs. MCT1 immunoreactivity was observed in photoreceptor inner segments, Müller cells, retinal capillaries, and the two plexiform layers. MCT2 labeling was concentrated in the inner and outer plexiform layers. MCT4 immunolabeling was present only in the inner retina, particularly in putative Müller cells, and the plexiform layers. No MCT3 labeling could be observed. The retinal pigment epithelium (RPE)/choroid expressed high levels of MCT1 and MCT3 mRNAs but lower levels of MCT2 and MCT4 mRNAs. MCT1 was localized to the apical and MCT3 to the basal membrane of the RPE, whereas MCT2 staining was faint. Although MCT1-MCT4 mRNAs were all detectable in iris and ciliary body samples, only MCT1 and MCT2 proteins were expressed. These were present in the iris epithelium and the nonpigmented epithelium of the ciliary processes. MCT4 was localized to the smooth muscle lining of large vessels in the iris-ciliary body and choroid. In the cornea, MCT1 and MCT2 mRNAs and proteins were detectable in the epithelium and endothelium, whereas evidence was found for the presence of MCT4 and, to a lesser extent, MCT1 in the lens epithelium. The unique distribution of MCT subtypes in the eye is indicative of the pivotal role that these transporters play in the maintenance of ocular function.
5
Pinheiro, Céline, Rui M. Reis, Sara Ricardo, Adhemar Longatto-Filho, Fernando Schmitt, and Fátima Baltazar. "Expression of Monocarboxylate Transporters 1, 2, and 4 in Human Tumours and Their Association with CD147 and CD44." Journal of Biomedicine and Biotechnology 2010 (2010): 1–7. http://dx.doi.org/10.1155/2010/427694.
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Monocarboxylate transporters (MCTs) are important cellular pH regulators in cancer cells; however, the value of MCT expression in cancer is still poorly understood. In the present study, we analysed MCT1, MCT2, and MCT4 protein expression in breast, colon, lung, and ovary neoplasms, as well as CD147 and CD44. MCT expression frequency was high and heterogeneous among the different tumours. Comparing with normal tissues, there was an increase in MCT1 and MCT4 expressions in breast carcinoma and a decrease in MCT4 plasma membrane expression in lung cancer. There were associations between CD147 and MCT1 expressions in ovarian cancer as well as between CD147 and MCT4 in both breast and lung cancers. CD44 was only associated with MCT1 plasma membrane expression in lung cancer. An important number of MCT1 positive cases are negative for both chaperones, suggesting that MCT plasma membrane expression in tumours may depend on a yet nonidentified regulatory protein.
6
HALESTRAP, Andrew P., and Nigel T. PRICE. "The proton-linked monocarboxylate transporter (MCT) family: structure, function and regulation." Biochemical Journal 343, no. 2 (October 8, 1999): 281–99. http://dx.doi.org/10.1042/bj3430281.
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Monocarboxylates such as lactate and pyruvate play a central role in cellular metabolism and metabolic communication between tissues. Essential to these roles is their rapid transport across the plasma membrane, which is catalysed by a recently identified family of proton-linked monocarboxylate transporters(MCTs). Nine MCT-related sequences have so far been identified in mammals, each having a different tissue distribution, whereas six related proteins can be recognized in Caenorhabditis elegansand 4 in Saccharomyces cerevisiae. Direct demonstration of proton-linked lactate and pyruvate transport has been demonstrated for mammalian MCT1-MCT4, but only for MCT1 and MCT2 have detailed analyses of substrate and inhibitor kinetics been described following heterologous expression in Xenopusoocytes. MCT1 is ubiquitously expressed, but is especially prominent in heart and red muscle, where it is up-regulated in response to increased work, suggesting a special role in lactic acid oxidation. By contrast, MCT4 is most evident in white muscle and other cells with a high glycolytic rate, such as tumour cells and white blood cells, suggesting it is expressed where lactic acid efflux predominates. MCT2 has a ten-fold higher affinity for substrates than MCT1 and MCT4 and is found in cells where rapid uptake at low substrate concentrations may be required, including the proximal kidney tubules, neurons and sperm tails. MCT3 is uniquely expressed in the retinal pigment epithelium. The mechanisms involved in regulating the expression of different MCT isoforms remain to be established. However, there is evidence for alternative splicing of the 5′- and 3′-untranslated regions and the use of alternative promoters for some isoforms. In addition, MCT1 and MCT4 have been shown to interact specifically with OX-47 (CD147), a member of the immunoglobulin superfamily with a single transmembrane helix. This interaction appears to assist MCT expression at the cell surface. There is still much work to be done to characterize the properties of the different isoforms and their regulation, which may have wide-ranging implications for health and disease. In the future it will be interesting to explore the linkage of genetic diseases to particular MCTs through their chromosomal location.
7
Ovens, Matthew J., Christine Manoharan, Marieangela C. Wilson, Clarey M. Murray, and Andrew P. Halestrap. "The inhibition of monocarboxylate transporter 2 (MCT2) by AR-C155858 is modulated by the associated ancillary protein." Biochemical Journal 431, no. 2 (September 28, 2010): 217–25. http://dx.doi.org/10.1042/bj20100890.
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In mammalian cells, MCTs (monocarboxylate transporters) require association with an ancillary protein to enable plasma membrane expression of the active transporter. Basigin is the preferred binding partner for MCT1, MCT3 and MCT4, and embigin for MCT2. In rat and rabbit erythrocytes, MCT1 is associated with embigin and basigin respectively, but its sensitivity to inhibition by AR-C155858 was found to be identical. Using RT (reverse transcription)–PCR, we have shown that Xenopus laevis oocytes contain endogenous basigin, but not embigin. Co-expression of exogenous embigin was without effect on either the expression of MCT1 or its inhibition by AR-C155858. In contrast, expression of active MCT2 at the plasma membrane of oocytes was significantly enhanced by co-expression of exogenous embigin. This additional transport activity was insensitive to inhibition by AR-C155858 unlike that by MCT2 expressed with endogenous basigin that was potently inhibited by AR-C155858. Chimaeras and C-terminal truncations of MCT1 and MCT2 were also expressed in oocytes in the presence and absence of exogenous embigin. L-Lactate Km values for these constructs were determined and revealed that the TM (transmembrane) domains of an MCT, most probably TM7–TM12, but not the C-terminus, are the major determinants of L-lactate affinity, whereas the associated ancillary protein has little or no effect. Inhibitor titrations of lactate transport by these constructs indicated that embigin modulates MCT2 sensitivity to AR-C155858 through interactions with both the intracellular C-terminus and TMs 3 and 6 of MCT2. The C-terminus of MCT2 was found to be essential for its expression with endogenous basigin.
8
Shrestha, Pawan, Amy E. Whelchel, Sarah E. Nicholas, Wentao Liang, Jian-Xing Ma, and Dimitrios Karamichos. "Monocarboxylate Transporters: Role and Regulation in Corneal Diabetes." Analytical Cellular Pathology 2022 (October 26, 2022): 1–10. http://dx.doi.org/10.1155/2022/6718566.
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Diabetes mellitus (DM) is a group of metabolic diseases that is known to cause structural and functional ocular complications. In the human cornea, DM-related complications affect the epithelium, stroma, and nerves. Monocarboxylate transporters (MCTs) are a family of proton-linked plasma membrane transporters that carry monocarboxylates across plasma membranes. In the context of corneal health and disease, their role, presence, and function are largely undetermined and solely focused on the most common MCT isoforms, 1 through 4. In this study, we investigated the regulation of MCT1, 2, 4, 5, 8, and 10, in corneal DM, using established 3D self-assembled extracellular matrix (ECM) in vitro models. Primary stromal corneal fibroblasts were isolated from healthy (HCFs), type I (T1DMs), and type II (T2DMs) DM donors. Monoculture 3D constructs were created by stimulating stromal cells on transwells with stable vitamin C for two or four weeks. Coculture 3D constructs were created by adding SH-SY5Y neurons at two different densities, 12 k and 500 k, on top of the monocultures. Our data showed significant upregulation of MCT1 at 4 weeks for HCF, T1DM, and T2DM monocultures, as well as the 500 k nerve cocultures. MCT8 was significantly upregulated in HCF and T1DM monocultures and all of the 500 k nerve cocultures. Further, MCT10 was only expressed at 4 weeks for all cocultures and was limited to HCFs and T1DMs in monocultures. Immunofluorescence analysis showed cytoplasmic MCT expression for all cell types and significant downregulation of both MCT2 and MCT4 in HCFs, when compared to T1DMs and T2DMs. Herein, we reveal the existence and modulation of MCTs in the human diabetic cornea in vitro. Changes appeared dependent on neuronal density, suggesting that MCTs are very likely critical to the neuronal defects observed in diabetic keratopathy/neuropathy. Further studies are warranted in order to fully delineate the role of MCTs in corneal diabetes.
9
Takimoto, Masaki, and Taku Hamada. "Acute exercise increases brain region-specific expression of MCT1, MCT2, MCT4, GLUT1, and COX IV proteins." Journal of Applied Physiology 116, no. 9 (May 1, 2014): 1238–50. http://dx.doi.org/10.1152/japplphysiol.01288.2013.
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The brain is capable of oxidizing lactate and ketone bodies through monocarboxylate transporters (MCTs). We examined the protein expression of MCT1, MCT2, MCT4, glucose transporter 1 (GLUT1), and cytochrome- c oxidase subunit IV (COX IV) in the rat brain within 24 h after a single exercise session. Brain samples were obtained from sedentary controls and treadmill-exercised rats (20 m/min, 8% grade). Acute exercise resulted in an increase in lactate in the cortex, hippocampus, and hypothalamus, but not the brainstem, and an increase in β-hydroxybutyrate in the cortex alone. After a 2-h exercise session MCT1 increased in the cortex and hippocampus 5 h postexercise, and the effect lasted in the cortex for 24 h postexercise. MCT2 increased in the cortex and hypothalamus 5–24 h postexercise, whereas MCT2 increased in the hippocampus immediately after exercise, and remained elevated for 10 h postexercise. Regional upregulation of MCT2 after exercise was associated with increases in brain-derived neurotrophic factor and tyrosine-related kinase B proteins, but not insulin-like growth factor 1. MCT4 increased 5–10 h postexercise only in the hypothalamus, and was associated with increased hypoxia-inducible factor-1α expression. However, none of the MCT isoforms in the brainstem was affected by exercise. Whereas GLUT 1 in the cortex increased only at 18 h postexercise, COX IV in the hippocampus increased 10 h after exercise and remained elevated for 24 h postexercise. These results suggest that acute prolonged exercise induces the brain region-specific upregulation of MCT1, MCT2, MCT4, GLUT1, and COX IV proteins.
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Hadjiagapiou, Christos, Larry Schmidt, Pradeep K. Dudeja, Thomas J. Layden, and Krishnamurthy Ramaswamy. "Mechanism(s) of butyrate transport in Caco-2 cells: role of monocarboxylate transporter 1." American Journal of Physiology-Gastrointestinal and Liver Physiology 279, no. 4 (October 1, 2000): G775—G780. http://dx.doi.org/10.1152/ajpgi.2000.279.4.g775.
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The short-chain fatty acid butyrate was readily taken up by Caco-2 cells. Transport exhibited saturation kinetics, was enhanced by low extracellular pH, and was Na+independent. Butyrate uptake was unaffected by DIDS; however, α-cyano-4-hydroxycinnamate and the butyrate analogs propionate and l-lactate significantly inhibited uptake. These results suggest that butyrate transport by Caco-2 cells is mediated by a transporter belonging to the monocarboxylate transporter family. We identified five isoforms of this transporter, MCT1, MCT3, MCT4, MCT5, and MCT6, in Caco-2 cells by PCR, and MCT1 was found to be the most abundant isoform by RNase protection assay. Transient transfection of MCT1, in the antisense orientation, resulted in significant inhibition of butyrate uptake. The cells fully recovered from this inhibition by 5 days after transfection. In conclusion, our data showed that the MCT1 transporter may play a major role in the transport of butyrate into Caco-2 cells.
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Hérubel, François, Saïd El Mouatassim, Pierre Guérin, René Frydman, and Yves Ménézo. "Genetic expression of monocarboxylate transporters during human and murine oocyte maturation and early embryonic development." Zygote 10, no. 2 (May 2002): 175–81. http://dx.doi.org/10.1017/s096719940200223x.
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During the early preimplantation stages of human embryos, pyruvate and lactate, but not glucose, are the preferred energy substrates. Transport of these monocarboxylates is mediated, in mammalian cells, by a family of transporters, designated as monocarboxylate transporters (MCTs). Human and mouse genetic expression of MCT members 1, 2, 3, 4 and basigin, a chaperone protein of MCT1 and MCT4, was qualitatively analysed using the reverse transcription nested polymerase chain reaction (RT-nested PCR) in immature oocytes (germinal vesicle stage; GV), in non-fertilised metaphase II (MII) oocytes and in embryos from 2-cell stage to blastocysts. Transcripts encoding for MCT1 and MCT2 were present, under a polyadenylated form, in the majority of the human and mouse oocytes and early embryos. MCT3 transcripts were not detected in either human or mouse. MCT4 mRNA was not detected in human oocytes and embryos, but was present in mouse oocytes and embryos. This fact could imply differences in lactate transport and regulation of intracellular pH between human and murine early embryos. Basigin transcripts were present in mouse and human MII oocytes and preimplantation embryos, but were not detected at GV stage. However, using 3' end-specific primers in the RT reaction instead of Oligo(dT)12-18 primers, transcripts encoding for this protein were then detected at GV stage in both species. This result suggests that a regulated polyadenylation process occurs during oocyte maturation for these transcripts. Thus, basigin mRNA can be considered as a marker of oocyte cytoplasmic maturation in human and mouse species.
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Wang, Yuxiang, Mio Tonouchi, Dragana Miskovic, Hideo Hatta, and Arend Bonen. "T3 increases lactate transport and the expression of MCT4, but not MCT1, in rat skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 285, no. 3 (September 2003): E622—E628. http://dx.doi.org/10.1152/ajpendo.00069.2003.
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Triiodothyronine (T3) regulates the expression of genes involved in muscle metabolism. Therefore, we examined the effects of a 7-day T3 treatment on the monocarboxylate transporters (MCT)1 and MCT4 in heart and in red (RG) and white gastrocnemius muscle (WG). We also examined rates of lactate transport into giant sarcolemmal vesicles and the plasmalemmal MCT1 and MCT4 in these vesicles. Ingestion of T3 markedly increased circulating serum T3 ( P < 0.05) and reduced weight gain ( P < 0.05). T3 upregulated MCT1 mRNA (RG +77, WG +49, heart +114%, P < 0.05) and MCT4 mRNA (RG +300, WG +40%). However, only MCT4 protein expression was increased (RG +43, WG +49%), not MCT1 protein expression. No changes in MCT1 protein were observed in any tissue. T3 treatment doubled the rate of lactate transport when vesicles were exposed to 1 mM lactate ( P < 0.05). However, plasmalemmal MCT4 was only modestly increased (+13%, P < 0.05). We conclude that T3 1) regulates MCT4, but not MCT1, protein expression and 2) increases lactate transport rates. This latter effect is difficult to explain by the modest changes in plasmalemmal MCT4. We speculate that either the activity of sarcolemmal MCTs has been altered or else other MCTs in muscle may have been upregulated.
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Hussien, Rajaa, and George A. Brooks. "Mitochondrial and plasma membrane lactate transporter and lactate dehydrogenase isoform expression in breast cancer cell lines." Physiological Genomics 43, no. 5 (March 2011): 255–64. http://dx.doi.org/10.1152/physiolgenomics.00177.2010.
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We hypothesized that dysregulation of lactate/pyruvate (monocarboxylate) transporters (MCT) and lactate dehydrogenase (LDH) isoforms contribute to the Warburg effect in cancer. Therefore, we assayed for the expression levels and the localizations of MCT ( 1 , 2 , and 4 ), and LDH (A and B) isoforms in breast cancer cell lines MCF-7 and MDA-MB-231 and compared results with those from a control, untransformed primary breast cell line, HMEC 184. Remarkably, MCT1 is not expressed in MDA-MB-231, but MCT1 is expressed in MCF-7 cells, where its abundance is less than in control HMEC 184 cells. When present in HMEC 184 and MCF-7 cells, MCT1 is localized to the plasma membrane. MCT2 and MCT4 were expressed in all the cell lines studied. MCT4 expression was higher in MDA-MB-231 compared with MCF-7 and HMEC 184 cells, whereas MCT2 abundance was higher in MCF-7 compared with MDA-MB-231 and HMEC 184 cells. Unlike MCT1, MCT2 and MCT4 were localized in mitochondria in addition to the plasma membrane. LDHA and LDHB were expressed in all the cell-lines, but abundances were higher in the two cancer cell lines than in the control cells. MCF-7 cells expressed mainly LDHB, while MDA-MB-231 and control cells expressed mainly LDHA. LDH isoforms were localized in mitochondria in addition to the cytosol. These localization patterns were the same in cancerous and control cell lines. In conclusion, MCT and LDH isoforms have distinct expression patterns in two breast cancer cell lines. These differences may contribute to divergent lactate dynamics and oxidative capacities in these cells, and offer possibilities for targeting cancer cells.
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Koehler-Stec, E. M., I. A. Simpson, S. J. Vannucci, K. T. Landschulz, and W. H. Landschulz. "Monocarboxylate transporter expression in mouse brain." American Journal of Physiology-Endocrinology and Metabolism 275, no. 3 (September 1, 1998): E516—E524. http://dx.doi.org/10.1152/ajpendo.1998.275.3.e516.
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Although glucose is the major metabolic fuel needed for normal brain function, monocarboxylic acids, i.e., lactate, pyruvate, and ketone bodies, can also be utilized by the brain as alternative energy substrates. In most mammalian cells, these substrates are transported either into or out of the cell by a family of monocarboxylate transporters (MCTs), first cloned and sequenced in the hamster. We have recently cloned two MCT isoforms (MCT1 and MCT2) from a mouse kidney cDNA library. Northern blot analysis revealed that MCT1 mRNA is ubiquitous and can be detected in most tissues at a relatively constant level. MCT2 expression is more limited, with high levels of expression confined to testes, kidney, stomach, and liver and lower levels in lung, brain, and epididymal fat. Both MCT1 mRNA and MCT2 mRNA are detected in mouse brain using antisense riboprobes and in situ hybridization. MCT1 mRNA is found throughout the cortex, with higher levels of hybridization in hippocampus and cerebellum. MCT2 mRNA was detected in the same areas, but the pattern of expression was more specific. In addition, MCT1 mRNA, but not MCT2, is localized to the choroid plexus, ependyma, microvessels, and white matter structures such as the corpus callosum. These results suggest a differential expression of the two MCTs at the cellular level.
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Pereira-Vieira, Joana, João Azevedo-Silva, Ana Preto, Margarida Casal, and Odília Queirós. "MCT1, MCT4 and CD147 expression and 3-bromopyruvate toxicity in colorectal cancer cells are modulated by the extracellular conditions." Biological Chemistry 400, no. 6 (June 26, 2019): 787–99. http://dx.doi.org/10.1515/hsz-2018-0411.
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Abstract Monocarboxylate transporters (MCTs) inhibition leads to disruption in glycolysis, induces cell death and decreases cell invasion, revealing the importance of MCT activity in intracellular pH homeostasis and tumor aggressiveness. 3-Bromopyruvate (3BP) is an anti-tumor agent, whose uptake occurs via MCTs. It was the aim of this work to unravel the importance of extracellular conditions on the regulation of MCTs and in 3BP activity. HCT-15 was found to be the most sensitive cell line, and also the one that presented the highest basal expression of both MCT1 and of its chaperone CD147. Glucose starvation and hypoxia induced an increased resistance to 3BP in HCT-15 cells, in contrast to what happens with an extracellular acidic pH, where no alterations in 3BP cytotoxicity was observed. However, no association with MCT1, MCT4 and CD147 expression was observed, except for glucose starvation, where a decrease in CD147 (but not of MCT1 and MCT4) was detected. These results show that 3BP cytotoxicity might include other factors beyond MCTs. Nevertheless, treatment with short-chain fatty acids (SCFAs) increased the expression of MCT4 and CD147 as well as the sensitivity of HCT-15 cells to 3BP. The overall results suggest that MCTs influence the 3BP effect, although they are not the only players in its mechanism of action.
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Moreira, Tiago JTP, Karin Pierre, Fumihiko Maekawa, Cendrine Repond, Aleta Cebere, Sture Liljequist, and Luc Pellerin. "Enhanced Cerebral Expression of MCT1 and MCT2 in a Rat Ischemia Model Occurs in Activated Microglial Cells." Journal of Cerebral Blood Flow & Metabolism 29, no. 7 (April 29, 2009): 1273–83. http://dx.doi.org/10.1038/jcbfm.2009.50.
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Monocarboxylate transporters (MCTs) are essential for the use of lactate, an energy substrate known to be overproduced in brain during an ischemic episode. The expression of MCT1 and MCT2 was investigated at 48 h of reperfusion from focal ischemia induced by unilateral extradural compression in Wistar rats. Increased MCT1 mRNA expression was detected in the injured cortex and hippocampus of compressed animals compared to sham controls. In the contralateral, uncompressed hemisphere, increases in MCT1 mRNA level in the cortex and MCT2 mRNA level in the hippocampus were noted. Interestingly, strong MCT1 and MCT2 protein expression was found in peri-lesional macrophages/microglia and in an isolectin B4+/S100β+ cell population in the corpus callosum. In vitro, MCT1 and MCT2 protein expression was observed in the N11 microglial cell line, whereas an enhancement of MCT1 expression by tumor necrosis factor-α (TNF-α) was shown in these cells. Modulation of MCT expression in microglia suggests that these transporters may help sustain microglial functions during recovery from focal brain ischemia. Overall, our study indicates that changes in MCT expression around and also away from the ischemic area, both at the mRNA and protein levels, are a part of the metabolic adaptations taking place in the brain after ischemia.
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Omlin, Teye, and Jean-Michel Weber. "Exhausting exercise and tissue-specific expression of monocarboxylate transporters in rainbow trout." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 304, no. 11 (June 1, 2013): R1036—R1043. http://dx.doi.org/10.1152/ajpregu.00516.2012.
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Transmembrane lactate movements are mediated by monocarboxylate transporters (MCTs), but these proteins have never been characterized in rainbow trout. Our goals were to clone potential trout MCTs, determine tissue distribution, and quantify the effects of exhausting exercise on MCT expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention ” seen in trout white muscle after intense exercise. Four isoforms were identified and partially characterized in rainbow trout: MCT1a, MCT1b, MCT2, and MCT4. MCT1b was the most abundant in heart and red muscle but poorly expressed in the gill and brain where MCT1a and MCT2 were prevalent. MCT expression was strongly stimulated by exhausting exercise in brain (MCT2: +260%) and heart (MCT1a: +90% and MCT1b: +50%), possibly to increase capacity for lactate uptake in these highly oxidative tissues. By contrast, the MCTs of gill, liver, and muscle remained unaffected by exercise. This study provides a possible functional explanation for postexercise “lactate retention” in trout white muscle. Rainbow trout may be unable to release large lactate loads rapidly during recovery because: 1) they only poorly express MCT4, the main lactate exporter found in mammalian glycolytic muscles; 2) the combined expression of all trout MCTs is much lower in white muscle than in any other tissue; and 3) exhausting exercise fails to upregulate white muscle MCT expression. In this tissue, carbohydrates act as an “energy spring” that alternates between explosive power release during intense swimming (glycogen to lactate) and recoil during protracted recovery (slow glycogen resynthesis from local lactate).
18
Pinheiro, Céline, Adhemar Longatto-Filho, Sônia Maria Miranda Pereira, Daniela Etlinger, Marise A. R. Moreira, Luiz Fernando Jubé, Geraldo Silva Queiroz, Fernando Schmitt, and Fátima Baltazar. "Monocarboxylate Transporters 1 and 4 Are Associated with CD147 in Cervical Carcinoma." Disease Markers 26, no. 3 (2009): 97–103. http://dx.doi.org/10.1155/2009/169678.
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Due to the highly glycolytic metabolism of solid tumours, there is an increased acid production, however, cells are able to maintain physiological pH through plasma membrane efflux of the accumulating protons. Acid efflux through MCTs (monocarboxylate transporters) constitutes one of the most important mechanisms involved in tumour intracellular pH maintenance. Still, the molecular mechanisms underlying the regulation of these proteins are not fully understood. We aimed to evaluate the association between CD147 (MCT1 and MCT4 chaperone) and MCT expression in cervical cancer lesions and the clinico-pathological significance of CD147 expression, alone and in combination with MCTs. The series included 83 biopsy samples of precursor lesions and surgical specimens of 126 invasive carcinomas. Analysis of CD147 expression was performed by immunohistochemistry. CD147 expression was higher in squamous and adenocarcinoma tissues than in the non-neoplastic counterparts and, importantly, both MCT1 and MCT4 were more frequently expressed in CD147 positive cases. Additionally, co-expression of CD147 with MCT1 was associated with lymph-node and/or distant metastases in adenocarcinomas. Our results show a close association between CD147 and MCT1 and MCT4 expressions in human cervical cancer and provided evidence for a prognostic value of CD147 and MCT1 co-expression.
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Jansen, S., M. Pantaleon, and P. Kaye. "236.Differential expression of monocarboxylate cotransporter proteins in preimplantation embryos." Reproduction, Fertility and Development 16, no. 9 (2004): 236. http://dx.doi.org/10.1071/srb04abs236.
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During preimplantation development mouse embryos demonstrate a switch in substrate preference. Pyruvate consumption, high during the first few cleavage stages, declines as the morula develops to a blastocyst, when glucose becomes the preferred substrate. Whilst pyruvate utilisation has been well characterised, changes in the function and expression of pyruvate transporters during this crucial period remain unclear. Pyruvate, lactate and other monocarboxylates are transported across mammalian cell membranes via a specific H+-monocarboxylate cotransporter (MCT). Fourteen members of this family have been identified of which MCT1, MCT2 and MCT4 are well characterised. Although mRNA expression profiles are known during early mouse development (1,2), the specific roles of each protein isoform are unknown. In order to understand these, the expression pattern for each isoform and their cellular localisation during preimplantation development have been determined. Mouse embryos were freshly collected from superovulated Quackenbush mice at 24, 48, 72 and 96 h post-hCG and expression of MCT1, MCT2 and MCT4 analysed by confocal laser scanning immunohistochemistry. Our results confirm that all three MCT proteins are expressed in preimplantation embryos. Immunoreactivity for MCT1 and MCT2 appears diffuse throughout the cytoplasm of cleavage stage embryos. As development proceeds, MCT1 localised to the basolateral membranes of morulae and blastocysts, whilst stronger MCT2 expression was found on the apical trophectoderm as well as the inner cell mass. MCT4 immunoreactivity on the other hand is apparent at cell-cell contact sites in cleavage stage embryos and morulae, but it is not apparent in the blastocyst. The demonstration of different expression patterns for MCT1, MCT2 and MCT4 in mouse embryos implies specific functional roles for each in the critical regulation of H+, pyruvate and lactate transport during preimplantation development. (1) Harding EA, Day ML, Gibb CA, Johnson MH, Cook DI (1999) The activity of the H+-monocarboxylate cotransporter during pre-implantation development in the mouse. Eur. J. Physiol. 438, 397–404. (2) H�rubel F, El Mouatassim S, Gu�rin P, Frydman R, M�n�zo Y (2002) Genetic expression of monocarboxylate transporters during human and murine oocyte maturation and early embryonic development. Zygote 10, 175–181.
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Cao, Jieyun, Michael Ng, and Melanie A. Felmlee. "Sex Hormones Regulate Rat Hepatic Monocarboxylate Transporter Expression and Membrane Trafficking." Journal of Pharmacy & Pharmaceutical Sciences 20, no. 1 (December 15, 2017): 435. http://dx.doi.org/10.18433/j3ch29.
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Purpose: Monocarboxylate transporters (MCTs) are involved in the transport of monocarboxylates such as ketone bodies, lactate, and pharmaceutical agents. CD147 functions as an ancillary protein for MCT1 and MCT4 for plasma membrane trafficking. Sex differences in MCT1 and MCT4 have been observed in muscle and reproductive tissues; however, there is a paucity of information on MCT sex differences in tissues involved in drug disposition. The objective of the present study was to quantify hepatic MCT1, MCT4 and CD147 mRNA, total cellular and membrane protein expression in males, over the estrous cycle in females and in ovariectomized (OVX) females. Method: Liver samples were collected from females at the four estrous cycle stages (proestrus, estrus, metestrus, diestrus), OVX females and male Sprague-Dawley rats (N = 3 – 5). Estrus cycle stage of females was determined by vaginal lavage. mRNA and protein (total and membrane) expression of MCT1, MCT4 and CD147 was evaluated by qPCR and western blot analysis. Results: MCT1 mRNA and membrane protein expression varied with estrous cycle stage, with OVX females having higher expression than males, indicating that female sex hormones may play a role in MCT1 regulation. MCT4 membrane expression varied with estrous cycle stage with expression significantly lower than males. MCT4 membrane expression in OVX females was also lower than males, suggesting that androgens play a role in membrane expression of MCT4. Males had higher membrane CD147 expression, whereas there was no difference in whole cell protein and mRNA levels suggesting that androgens are involved in regulating CD147 membrane localization. Conclusions: This study demonstrates hepatic expression and membrane localization of MCT1, MCT4 and CD147 are regulated by sex hormones. Sex differences in hepatic MCT expression may lead to altered drug disposition, so it is critical to elucidate the underlying mechanisms in the sex hormone-dependent regulation of MCT expression. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.
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Lai, Y. L., J. W. Olson, and M. N. Gillespie. "Ventilatory dysfunction precedes pulmonary vascular changes in monocrotaline-treated rats." Journal of Applied Physiology 70, no. 2 (February 1, 1991): 561–66. http://dx.doi.org/10.1152/jappl.1991.70.2.561.
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Rats with established monocrotaline (MCT)-induced pulmonary hypertension also exhibit a profound increase in lung resistance (RL) and a decrease in lung compliance. Because airway/lung dysfunction could precede and influence the evolution of MCT-induced pulmonary vascular disease, it is important to establish the temporal relationship between development of pulmonary hypertension and altered ventilatory function in MCT-treated rats. To resolve this issue, we segregated 47 young Sprague-Dawley rats into four groups: control (n = 13), MCT1 (n = 9), MCT2 (n = 11), and MCT3 (n = 14). Each MCT rat received a single subcutaneous injection of MCT (60 mg/kg) 1 MCT1), 2 (MCT2), or 3 (MCT3) wk before the functional study. At 1 wk after MCT, significant increases in RL and alveolar wall thickness were observed, as was a significant decrease in carbon monoxide diffusing capacity (DLCO). Medial thickness of pulmonary arteries (50-100 microns OD) and right ventricular hypertrophy were not observed until 2 and 3 wk post-MCT, respectively. Coincident with the right ventricular hypertrophy at 3 wk post-MCT were decreased DLCO and increased alveolar wall thickness and lung dry weight. Pressure-volume curves of air-filled and saline-filled lungs showed marked rightward shifts during the 1st and 2nd wk after MCT administration and then decreased at the 3rd wk. These data suggest that MCT-induced alterations in airway/lung function preceded those of pulmonary vasculature and, therefore, implicate airway/lung dysfunctions as potentially contributing to the later development of pulmonary vascular abnormalities.
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Pilegaard, Henriette, Gerasimos Terzis, Andrew Halestrap, and Carsten Juel. "Distribution of the lactate/H+ transporter isoforms MCT1 and MCT4 in human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 276, no. 5 (May 1, 1999): E843—E848. http://dx.doi.org/10.1152/ajpendo.1999.276.5.e843.
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The profiles of the lactate/H+ transporter isoforms [monocarboxylate transporter isoforms (MCT)] MCT1 and MCT4 (formerly MCT3 of Price, N. T., V. N. Jackson, and A. P. Halestrap. Biochem. J. 329: 321–328, 1998) were studied in the soleus, triceps brachii, and vastus lateralis muscles of six male subjects. The fiber-type compositions of the muscles were evaluated from the occurrence of the myosin heavy chain isoforms, and the fibers were classified as type I, IIA, or IIX. The total content of MCT1 and MCT4 was determined in muscle homogenates by Western blotting, and MCT1 and MCT4 were visualized on cross-sectional muscle sections by immunofluorescence microscopy. The Western blotting revealed a positive, linear relationship between the MCT1 content and the occurrence of type I fibers in the muscle, but no significant relation was found between MCT4 content and fiber type. Moreover, the interindividual variation in MCT4 content was much larger than the interindividual variation in MCT1 content in homogenate samples. The immunofluorescence microscopy showed that within a given muscle section, the MCT4 isoform was clearly more abundant in type II fibers than in type I fibers, whereas only minor differences existed in the occurrence of the MCT1 isoform between type I and II fibers. Together the present results indicate that the content of MCT1 in a muscle varies between different muscles, whereas fiber-type differences in MCT1 content are minor within a given muscle section. In contrast, the content of MCT4 is clearly fiber-type specific but apparently quite similar in various muscles.
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Gill, Ravinder K., Seema Saksena, Waddah A. Alrefai, Zaheer Sarwar, Jay L. Goldstein, Robert E. Carroll, Krishnamurthy Ramaswamy, and Pradeep K. Dudeja. "Expression and membrane localization of MCT isoforms along the length of the human intestine." American Journal of Physiology-Cell Physiology 289, no. 4 (October 2005): C846—C852. http://dx.doi.org/10.1152/ajpcell.00112.2005.
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Recent studies from our laboratory and others have demonstrated the involvement of monocarboxylate transporter (MCT)1 in the luminal uptake of short-chain fatty acids (SCFAs) in the human intestine. Functional studies from our laboratory previously demonstrated kinetically distinct SCFA transporters on the apical and basolateral membranes of human colonocytes. Although apical SCFA uptake is mediated by the MCT1 isoform, the molecular identity of the basolateral membrane SCFA transporter(s) and whether this transporter is encoded by another MCT isoform is not known. The present studies were designed to assess the expression and membrane localization of different MCT isoforms in human small intestine and colon. Immunoblotting was performed with the purified apical and basolateral membranes from human intestinal mucosa obtained from organ donor intestine. Immunohistochemistry studies were done on paraffin-embedded sections of human colonic biopsy samples. Immunoblotting studies detected a protein band of ∼39 kDa for MCT1, predominantly in the apical membranes. The relative abundance of MCT1 mRNA and protein increased along the length of the human intestine. MCT4 (54 kDa) and MCT5 (54 kDa) isoforms showed basolateral localization and were highly expressed in the distal colon. Immunohistochemical studies confirmed that human MCT1 antibody labeling was confined to the apical membranes, whereas MCT5 antibody staining was restricted to the basolateral membranes of the colonocytes. We speculate that distinct MCT isoforms may be involved in SCFA transport across the apical or basolateral membranes in polarized colonic epithelial cells.
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Gallagher, Shannon M., John J. Castorino, and Nancy J. Philp. "Interaction of monocarboxylate transporter 4 with β1-integrin and its role in cell migration." American Journal of Physiology-Cell Physiology 296, no. 3 (March 2009): C414—C421. http://dx.doi.org/10.1152/ajpcell.00430.2008.
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Monocarboxylate transporter (MCT) 4 is a heteromeric proton-coupled lactate transporter that is noncovalently linked to the extracellular matrix metalloproteinase inducer CD147 and is typically expressed in glycolytic tissues. There is increasing evidence to suggest that ion transporters are part of macromolecular complexes involved in regulating β1-integrin adhesion and cell movement. In the present study we examined whether MCTs play a role in cell migration through their interaction with β1-integrin. Using reciprocal coimmunoprecipitation assays, we found that β1-integrin selectively associated with MCT4 in ARPE-19 and MDCK cells, two epithelial cell lines that express both MCT1 and MCT4. In polarized monolayers of ARPE-19 cells, MCT4 and β1-integrin colocalized to the basolateral membrane, while both proteins were found in the leading edge lamellapodia of migrating cells. In scratch-wound assays, MCT4 knockdown slowed migration and increased focal adhesion size. In contrast, silencing MCT1 did not alter the rate of cell migration or focal adhesion size. Taken together, our findings suggest that the specific interaction of MCT4 with β1-integrin may regulate cell migration through modulation of focal adhesions.
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Vannucci, Susan J., and Ian A. Simpson. "Developmental switch in brain nutrient transporter expression in the rat." American Journal of Physiology-Endocrinology and Metabolism 285, no. 5 (November 2003): E1127—E1134. http://dx.doi.org/10.1152/ajpendo.00187.2003.
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Normal development of both human and rat brain is associated with a switch in metabolic fuel from a combination of glucose and ketone bodies in the immature brain to a nearly total reliance on glucose in the adult. The delivery of glucose, lactate, and ketone bodies from the blood to the brain requires specific transporter proteins, glucose and monocarboxylic acid transporter proteins (GLUTs and MCTs), respectively. Developmental expression of the GLUTs in rat brain, i.e., 55-kDa GLUT1 in the blood-brain barrier (BBB), 45-kDa GLUT1 and GLUT3 in vascular-free brain, corresponds to maturational increases in cerebral glucose uptake and utilization. It has been suggested that MCT expression peaks during suckling and sharply declines thereafter, although a comparable detailed study has not been done. This study investigated the temporal and regional expression of MCT1 and MCT2 mRNA and protein in the BBB and the nonvascular brain during postnatal development in the rat. The results confirmed maximal MCT1 mRNA and protein expression in the BBB during suckling and a decline with maturation, coincident with the switch to glucose as the predominant cerebral fuel. However, nonvascular MCT1 and MCT2 levels do not reflect changes in cerebral energy metabolism, suggesting a more complex regulation. Although MCT1 assumes a predominantly glial expression in postweanling brain, the concentration remains fairly constant, as does that of MCT2 in neurons. The maintenance of nonvascular MCT levels in the adult brain implies a major role for these proteins, in concert with the GLUTs in both neurons and astrocytes, to transfer glycolytic intermediates during cerebral energy metabolism.
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Kubelt, Carolin, Sönke Peters, Hajrullah Ahmeti, Monika Huhndorf, Lukas Huber, Gesa Cohrs, Jan-Bernd Hövener, Olav Jansen, Michael Synowitz, and Janka Held-Feindt. "Intratumoral Distribution of Lactate and the Monocarboxylate Transporters 1 and 4 in Human Glioblastoma Multiforme and Their Relationships to Tumor Progression-Associated Markers." International Journal of Molecular Sciences 21, no. 17 (August 29, 2020): 6254. http://dx.doi.org/10.3390/ijms21176254.
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(1) Background: Metabolic reprogramming has been postulated to be one of the hallmarks of cancer, thus representing a promising therapeutic target also in glioblastoma multiforme (GBM). Hypoxic tumor cells produce lactate, and monocarboxylate transporters (MCTs) play an important role in its distribution; (2) Methods: We examined the distribution of lactate by multi voxel magnetic resonance spectroscopic imaging and ELISA in glioblastoma multiforme (GBM) patients. In addition, we investigated the expression and cellular localization of MCT1, MCT4, and of several markers connected to tumor progression by quantitative PCR and immunofluorescence double-staining in human GBM ex vivo tissues; (3) Results: The highest lactate concentration was found at the center of the vital parts of the tumor. Three main GBM groups could be distinguished according to their regional gene expression differences of the investigated genes. MCT1 and MCT4 were found on cells undergoing epithelial to mesenchymal transition and on tumor stem-like cells. GBM cells revealing an expression of cellular dormancy markers, showed positive staining for MCT4; (4) Conclusion: Our findings indicate the existence of individual differences in the regional distribution of MCT1 and MCT4 and suggest that both transporters have distinct connections to GBM progression processes, which could contribute to the drug resistance of MCT-inhibitors.
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Papakonstantinou, Eleni, Dimitrios Vlachakis, Trias Thireou, Panayiotis G. Vlachoyiannopoulos, and Elias Eliopoulos. "A Holistic Evolutionary and 3D Pharmacophore Modelling Study Provides Insights into the Metabolism, Function, and Substrate Selectivity of the Human Monocarboxylate Transporter 4 (hMCT4)." International Journal of Molecular Sciences 22, no. 6 (March 13, 2021): 2918. http://dx.doi.org/10.3390/ijms22062918.
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Monocarboxylate transporters (MCTs) are of great research interest for their role in cancer cell metabolism and their potential ability to transport pharmacologically relevant compounds across the membrane. Each member of the MCT family could potentially provide novel therapeutic approaches to various diseases. The major differences among MCTs are related to each of their specific metabolic roles, their relative substrate and inhibitor affinities, the regulation of their expression, their intracellular localization, and their tissue distribution. MCT4 is the main mediator for the efflux of L-lactate produced in the cell. Thus, MCT4 maintains the glycolytic phenotype of the cancer cell by supplying the molecular resources for tumor cell proliferation and promotes the acidification of the extracellular microenvironment from the co-transport of protons. A promising therapeutic strategy in anti-cancer drug design is the selective inhibition of MCT4 for the glycolytic suppression of solid tumors. A small number of studies indicate molecules for dual inhibition of MCT1 and MCT4; however, no selective inhibitor with high-affinity for MCT4 has been identified. In this study, we attempt to approach the structural characteristics of MCT4 through an in silico pipeline for molecular modelling and pharmacophore elucidation towards the identification of specific inhibitors as a novel anti-cancer strategy.
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Hatta, Hideo, Mio Tonouchi, Dragana Miskovic, Yuxiang Wang, John J. Heikkila, and Arend Bonen. "Tissue-specific and isoform-specific changes in MCT1 and MCT4 in heart and soleus muscle during a 1-yr period." American Journal of Physiology-Endocrinology and Metabolism 281, no. 4 (October 1, 2001): E749—E756. http://dx.doi.org/10.1152/ajpendo.2001.281.4.e749.
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We examined the postnatal changes ( days 10, 36, 84, 160, 365) of monocarboxylate transporters (MCT)1 and MCT4 in rat heart and soleus muscle. In the heart, MCT1 protein and mRNA remained unaltered from day 10 until 1 yr of age. Both MCT4 protein and mRNA in the heart were detected at 10 days of age, but the MCT4 protein and transcript were not detected thereafter. In the soleus muscle, MCT1 protein (+38%) and mRNA (+136%) increased during the first 84 days and remained stable until 1 yr of age. In contrast, soleus MCT4 protein decreased by 90% over the course of 1 yr, with the most rapid decrease (−60%) occurring by day 84 ( P < 0.05). At the same time, MCT4 mRNA was increased by 74% from days 10to 84 ( P < 0.05), remaining stable thereafter. In conclusion, developmental changes in MCT transport proteins are tissue specific and isoform specific. Furthermore, it appears that MCT1 expression in the heart and MCT1 and MCT4 expression in the soleus are regulated by pretranslational processes, whereas posttranscriptional processes regulate MCT4 expression in the soleus muscle.
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Thomas, Claire, David J. Bishop, Karen Lambert, Jacques Mercier, and George A. Brooks. "Effects of acute and chronic exercise on sarcolemmal MCT1 and MCT4 contents in human skeletal muscles: current status." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 302, no. 1 (January 2012): R1—R14. http://dx.doi.org/10.1152/ajpregu.00250.2011.
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Two lactate/proton cotransporter isoforms (monocarboxylate transporters, MCT1 and MCT4) are present in the plasma (sarcolemmal) membranes of skeletal muscle. Both isoforms are symports and are involved in both muscle pH and lactate regulation. Accordingly, sarcolemmal MCT isoform expression may play an important role in exercise performance. Acute exercise alters human MCT content, within the first 24 h from the onset of exercise. The regulation of MCT protein expression is complex after acute exercise, since there is not a simple concordance between changes in mRNA abundance and protein levels. In general, exercise produces greater increases in MCT1 than in MCT4 content. Chronic exercise also affects MCT1 and MCT4 content, regardless of the initial fitness of subjects. On the basis of cross-sectional studies, intensity would appear to be the most important factor regulating exercise-induced changes in MCT content. Regulation of skeletal muscle MCT1 and MCT4 content by a variety of stimuli inducing an elevation of lactate level (exercise, hypoxia, nutrition, metabolic perturbations) has been demonstrated. Dissociation between the regulation of MCT content and lactate transport activity has been reported in a number of studies, and changes in MCT content are more common in response to contractile activity, whereas changes in lactate transport capacity typically occur in response to changes in metabolic pathways. Muscle MCT expression is involved in, but is not the sole determinant of, muscle H+and lactate anion exchange during physical activity.
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Benton, Carley R., Yuko Yoshida, James Lally, Xiao-Xia Han, Hideo Hatta, and Arend Bonen. "PGC-1α increases skeletal muscle lactate uptake by increasing the expression of MCT1 but not MCT2 or MCT4." Physiological Genomics 35, no. 1 (September 2008): 45–54. http://dx.doi.org/10.1152/physiolgenomics.90217.2008.
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We examined the relationship between PGC-1α protein; the monocarboxylate transporters MCT1, 2, and 4; and CD147 1) among six metabolically heterogeneous rat muscles, 2) in chronically stimulated red (RTA) and white tibialis (WTA) muscles (7 days), and 3) in RTA and WTA muscles transfected with PGC-1α-pcDNA plasmid in vivo. Among rat hindlimb muscles, there was a strong positive association between PGC-1α and MCT1 and CD147, and between MCT1 and CD147. A negative association was found between PGC-1α and MCT4, and CD147 and MCT4, while there was no relationship between PGC-1α or CD147 and MCT2. Transfecting PGC-1α-pcDNA plasmid into muscle increased PGC-1α protein (RTA +23%; WTA +25%) and induced the expression of MCT1 (RTA +16%; WTA +28%), but not MCT2 and MCT4. As a result of the PGC-1α-induced upregulation of MCT1 and its chaperone CD147 (+29%), there was a concomitant increase in the rate of lactate uptake (+20%). In chronically stimulated muscles, the following proteins were upregulated, PGC-1α in RTA (+26%) and WTA (+86%), MCT1 in RTA (+61%) and WTA (+180%), and CD147 in WTA (+106%). In contrast, MCT4 protein expression was not altered in either RTA or WTA muscles, while MCT2 protein expression was reduced in both RTA (−14%) and WTA (−10%). In these studies, whether comparing oxidative capacities among muscles or increasing their oxidative capacities by PGC-1α transfection and chronic muscle stimulation, there was a strong relationship between the expression of PGC-1α and MCT1, and PGC-1α and CD147 proteins. Thus, MCT1 and CD147 belong to the family of metabolic genes whose expression is regulated by PGC-1α in skeletal muscle.
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Hiltunen, Niko, Jukka Rintala, Juha P. Väyrynen, Jan Böhm, Tuomo J. Karttunen, Heikki Huhta, and Olli Helminen. "Monocarboxylate Transporters 1 and 4 and Prognosis in Small Bowel Neuroendocrine Tumors." Cancers 14, no. 10 (May 22, 2022): 2552. http://dx.doi.org/10.3390/cancers14102552.
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Monocarboxylate transporters (MCTs) are cell membrane proteins transporting lactate, pyruvate, and ketone bodies across the plasma membrane. The prognostic role of MCTs in neuroendocrine tumors is unknown. We aimed to analyze MCT1 and MCT4 expression in small bowel neuroendocrine tumors (SB-NETs). The cohort included 109 SB-NETs and 61 SB-NET lymph node metastases from two Finnish hospitals. Tumor samples were immunohistochemically stained with MCT1 and MCT4 monoclonal antibodies. The staining intensity, percentage of positive cells, and stromal staining were assessed. MCT1 and MCT4 scores (0, 1 or 2) were composed based on the staining intensity and the percentage of positive cells. Survival analyses were performed with the Kaplan–Meier method and Cox regression, adjusted for confounders. The primary outcome was disease-specific survival (DSS). A high MCT4 intensity in SB-NETs was associated with better DSS when compared to low intensity (85.7 vs. 56.6%, p = 0.020). A high MCT4 percentage of positive cells resulted in better DSS when compared to a low percentage (77.4 vs. 49.1%, p = 0.059). MCT4 scores 0, 1, and 2 showed DSS of 52.8 vs. 58.8 vs. 100% (p = 0.025), respectively. After adjusting for confounders, the mortality hazard was lowest in the patients with a high MCT4 score. MCT1 showed no association with survival. According to our study, a high MCT4 expression is associated with an improved prognosis in SB-NETs.
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Ahanger, Mohsin Ahmad, and Ghulam Jeelani. "Deformation Kinematics of Main Central Thrust Zone (MCTZ) in the Western Himalayas." Journal of Earth Science 33, no. 2 (April 2022): 452–61. http://dx.doi.org/10.1007/s12583-020-1059-6.
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Bonen, Arend, Dragana Miskovic, Mio Tonouchi, Kathleen Lemieux, Marieangela C. Wilson, André Marette, and Andrew P. Halestrap. "Abundance and subcellular distribution of MCT1 and MCT4 in heart and fast-twitch skeletal muscles." American Journal of Physiology-Endocrinology and Metabolism 278, no. 6 (June 1, 2000): E1067—E1077. http://dx.doi.org/10.1152/ajpendo.2000.278.6.e1067.
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The expression of two monocarboxylate transporters (MCTs) was examined in muscle and heart. MCT1 and MCT4 proteins are coexpressed in rat skeletal muscles, but only MCT1 is expressed in rat hearts. Among six rat fast-twitch muscles (red and white gastrocnemius, plantaris, extensor digitorum longus, red and white tibialis anterior) there was an inverse relationship between MCT1 and MCT4 ( r = −0.94). MCT1 protein was correlated with MCT1 mRNA ( r = 0.94). There was no relationship between MCT4 mRNA and MCT4 protein. MCT1 ( r = −0.97) and MCT4 ( r = 0.88) protein contents were correlated with percent fast-twitch glycolytic fiber. When normalized for their mRNAs, MCT1 but not MCT4 was still correlated with the percent fast-twitch glycolytic fiber composition of rat muscles ( r = −0.98). MCT1 and MCT4 were also measured in plasma membranes (PM), triads (TR), T tubules (TT), sarcoplasmic reticulum (SR), and intracellular membranes (IM). There was an intracellular pool of MCT4 but not of MCT1. The MCT1 subcellular distribution was as follows: PM (100%) > TR (31.6%) > SR (15%) = TT (14%) > IM (1.7%). The MCT4 subcellular distribution was considerably different [PM (100%) > TR (66.5%) > TT (36%) = SR (43%) > IM (24%)]. These studies have shown that 1) the mechanisms regulating the expression of MCT1 (transcriptional and posttranscriptional) and MCT4 (posttranscriptional) are different and 2) differences in MCT1 and MCT4 expression among muscles, as well as in their subcellular locations, suggest that they may have different roles in muscle.
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Bishop, David, Johann Edge, Claire Thomas, and Jacques Mercier. "High-intensity exercise acutely decreases the membrane content of MCT1 and MCT4 and buffer capacity in human skeletal muscle." Journal of Applied Physiology 102, no. 2 (February 2007): 616–21. http://dx.doi.org/10.1152/japplphysiol.00590.2006.
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The regulation of intracellular pH during intense muscle contractions occurs via a number of different transport systems [e.g., monocarboxylate transporters (MCTs)] and via intracellular buffering (βmin vitro). The aim of this study was to investigate the effects of an acute bout of high-intensity exercise on both MCT relative abundance and βmin vitro in humans. Six active women volunteered for this study. Biopsies of the vastus lateralis were obtained at rest and immediately after 45 s of exercise at 200% of maximum O2 uptake. βmin vitro was determined by titration, and MCT relative abundance was determined in membrane preparations by Western blots. High-intensity exercise was associated with a significant decrease in both MCT1 (−24%) and MCT4 (−26%) and a decrease in βmin vitro (−11%; 135 ± 3 to 120 ± 2 μmol H+·g dry muscle−1·pH−1; P < 0.05). These changes were consistently observed in all subjects, and there was a significant correlation between changes in MCT1 and MCT4 relative abundance ( R2 = 0.92; P < 0.05). In conclusion, a single bout of high-intensity exercise decreased both MCT relative abundance in membrane preparations and βmin vitro. Until the time course of these changes has been established, researchers should consider the possibility that observed training-induced changes in MCT and βmin vitro may be influenced by the acute effects of the last exercise bout, if the biopsy is taken soon after the completion of the training program. The implications that these findings have for lactate (and H+) transport following acute, exhaustive exercise warrant further investigation.
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Dubouchaud, Hervé, Gail E. Butterfield, Eugene E. Wolfel, Bryan C. Bergman, and George A. Brooks. "Endurance training, expression, and physiology of LDH, MCT1, and MCT4 in human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 278, no. 4 (April 1, 2000): E571—E579. http://dx.doi.org/10.1152/ajpendo.2000.278.4.e571.
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To evaluate the effects of endurance training on the expression of monocarboxylate transporters (MCT) in human vastus lateralis muscle, we compared the amounts of MCT1 and MCT4 in total muscle preparations (MU) and sarcolemma-enriched (SL) and mitochondria-enriched (MI) fractions before and after training. To determine if changes in muscle lactate release and oxidation were associated with training-induced changes in MCT expression, we correlated band densities in Western blots to lactate kinetics determined in vivo. Nine weeks of leg cycle endurance training [75% peak oxygen consumption (V˙o 2 peak)] increased muscle citrate synthase activity (+75%, P < 0.05) and percentage of type I myosin heavy chain (+50%, P < 0.05); percentage of MU lactate dehydrogenase-5 (M4) isozyme decreased (−12%, P < 0.05). MCT1 was detected in SL and MI fractions, and MCT4 was localized to the SL. Muscle MCT1 contents were consistent among subjects both before and after training; in contrast, MCT4 contents showed large interindividual variations. MCT1 amounts significantly increased in MU, SL, and MI after training (+90%, +60%, and +78%, respectively), whereas SL but not MU MCT4 content increased after training (+47%, P < 0.05). Mitochondrial MCT1 content was negatively correlated to net leg lactate release at rest ( r = −0.85, P < 0.02). Sarcolemmal MCT1 and MCT4 contents correlated positively to net leg lactate release at 5 min of exercise at 65%V˙o 2 peak ( r = 0.76, P < 0.03 and r = 0.86, P < 0.01, respectively). Results support the conclusions that 1) endurance training increases expression of MCT1 in muscle because of insertion of MCT1 into both sarcolemmal and mitochondrial membranes, 2) training has variable effects on sarcolemmal MCT4, and 3) both MCT1 and MCT4 participate in the cell-cell lactate shuttle, whereas MCT1 facilitates operation of the intracellular lactate shuttle.
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Ng, Michael, Justin Louie, Jieyun Cao, and Melanie A. Felmlee. "Developmental Expression of Monocarboxylate Transporter 1 and 4 in Rat Liver." Journal of Pharmacy & Pharmaceutical Sciences 22 (July 30, 2019): 376–87. http://dx.doi.org/10.18433/jpps30537.
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Purpose: Monocarboxylate transporters (MCT) are proton-coupled integral membrane proteins that control the influx and efflux of endogenous monocarboxylates such as lactate, acetate and pyruvate. They also transport and mediate the clearance of drugs such as valproate and gamma-hydroxybutyrate. CD147 functions as ancillary protein that chaperones MCT1 and MCT4 to the cell membrane. There is limited data on the maturation of MCT and CD147 expression in tissues related to drug distribution and clearance. The objective of the present study was to quantify hepatic MCT1, MCT4, and CD147 mRNA, whole cell and membrane protein expression from birth to sexual maturity. Methods: Liver tissues were collected from male and female Sprague Dawley rats at postnatal days (PND) 1, 3, 5, 7, 10, 14, 18, 21, 28, 35, and 42 (n = 3 - 5). Hepatic mRNA, total and membrane protein expression of MCT1, MCT4, and CD147 was evaluated via qPCR and western blot. Results: MCT1 mRNA and protein demonstrated nonlinear maturation patterns. MCT1 and CD147 membrane protein exhibited low expression at birth, with expression increasing three-fold by PND14, followed by a decline in expression at sexual maturity. MCT4 mRNA had highest expression at PND 1, with decreasing expression towards sexual maturity. In contrast, MCT4 membrane protein exhibited minimal expression from birth through weaning before a 10-fold surge at PND35, whereupon there was a sharp decline in expression at PND42. There was a significant positive correlation between MCT1 and CD147 whole cell and membrane expression, while MCT4 membrane expression demonstrated a weak negative correlation with CD147. Conclusion: Our study elucidates the transcriptional and translational maturation patterns of MCT1, MCT4 and CD147 expression, with isoform-dependent differences in the liver. Changes in transporter expression during development may greatly influence drug distribution and clearance in pediatric populations.
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Tonouchi, Mio, Hideo Hatta, and Arend Bonen. "Muscle contraction increases lactate transport while reducing sarcolemmal MCT4, but not MCT1." American Journal of Physiology-Endocrinology and Metabolism 282, no. 5 (May 1, 2002): E1062—E1069. http://dx.doi.org/10.1152/ajpendo.00358.2001.
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Rates of lactate uptake into giant sarcolemmal vesicles were determined in vesicles collected from rat muscles at rest and immediately after 10 min of intense muscle contraction. This contraction period reduced muscle glycogen rapidly by 37–82% in all muscles examined ( P < 0.05) except the soleus muscle (no change P > 0.05). At an external lactate concentration of 1 mM lactate, uptake into giant sarcolemmal vesicles was not altered ( P > 0.05), whereas at an external lactate concentration of 20 mM, the rate of lactate uptake was increased by 64% ( P < 0.05). Concomitantly, the plasma membrane content of monocarboxylate transporter (MCT)1 was reduced slightly (−10%, P < 0.05), and the plasma membrane content of MCT4 was reduced further (−25%, P < 0.05). In additional studies, the 10-min contraction period increased the plasma membrane GLUT4 ( P < 0.05) while again reducing MCT4 (−20%, P < 0.05) but not MCT1 ( P > 0.05). These studies have shown that intense muscle contraction can increase the initial rates of lactate uptake, but only when the external lactate concentrations are high (20 mM). We speculate that muscle contraction increases the intrinsic activity of the plasma membrane MCTs, because the increase in lactate uptake occurred while plasma membrane MCT4 was decreased and plasma membrane MCT1 was reduced only minimally, or not at all.
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Bonen, Arend, Mio Tonouchi, Dragana Miskovic, Catherine Heddle, John J. Heikkila, and Andrew P. Halestrap. "Isoform-specific regulation of the lactate transporters MCT1 and MCT4 by contractile activity." American Journal of Physiology-Endocrinology and Metabolism 279, no. 5 (November 1, 2000): E1131—E1138. http://dx.doi.org/10.1152/ajpendo.2000.279.5.e1131.
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We examined the isoform-specific regulation of monocarboxylate transporter (MCT)1 and MCT4 expression by contractile activity in red and white tibialis anterior muscles. After 1 and 3 wk of chronic muscle stimulation (24 h/day), MCT1 protein expression was increased in the red muscles (+78%, P< 0.05). In the white muscles, MCT1 was increased after 1 wk (+191%) and then was decreased after 3 wk. In the red muscle, MCT1 mRNA accumulation was increased only after 3 wk (+21%; P < 0.05). In the white muscle, MCT1 mRNA was increased after 1 wk (+30%; P < 0.05) and 3 wk (+15%; P < 0.05). MCT4 protein was not altered in either the red or white muscles after 1 or 3 wk. MCT4 mRNA was transiently lowered (∼15%) in both muscles in the 1st wk, but MCT4 mRNA levels were back to control levels after 3 wk. In conclusion, chronic contractile activity induces the expression of MCT1 but not MCT4. This increase in MCT1 alone was sufficient to increase lactate uptake from the circulation.
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DIMMER, Kai-Stefan, Björn FRIEDRICH, Florian LANG, Joachim W. DEITMER, and Stefan BRÖER. "The low-affinity monocarboxylate transporter MCT4 is adapted to the export of lactate in highly glycolytic cells." Biochemical Journal 350, no. 1 (August 9, 2000): 219–27. http://dx.doi.org/10.1042/bj3500219.
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Transport of lactate and other monocarboxylates in mammalian cells is mediated by a family of transporters, designated monocarboxylate transporters (MCTs). The MCT4 member of this family has recently been identified as the major isoform of white muscle cells, mediating lactate efflux out of glycolytically active myocytes [Wilson, Jackson, Heddle, Price, Pilegaard, Juel, Bonen, Montgomery, Hutter and Halestrap (1998) J. Biol. Chem. 273, 15920–15926]. To analyse the functional properties of this transporter, rat MCT4 was expressed in Xenopus laevis oocytes and transport activity was monitored by flux measurements with radioactive tracers and by changes of the cytosolic pH using pH-sensitive microelectrodes. Similar to other members of this family, monocarboxylate transport via MCT4 is accompanied by the transport of H+ across the plasma membrane. Uptake of lactate strongly increased with decreasing extracellular pH, which resulted from a concomitant drop in the Km value. MCT4 could be distinguished from the other isoforms mainly in two respects. First, MCT4 is a low-affinity MCT: for l-lactate Km values of 17±3mM (pH-electrode) and 34±5mM (flux measurements with l-[U-14C]lactate) were determined. Secondly, lactate is the preferred substrate of MCT4. Km values of other monocarboxylates were either similar to the Km value for lactate (pyruvate, 2-oxoisohexanoate, 2-oxoisopentanoate, acetoacetate) or displayed much lower affinity for the transporter (β-hydroxybutyrate and short-chain fatty acids). Under physiological conditions, rat MCT will therefore preferentially transport lactate. Monocarboxylate transport via MCT4 could be competitively inhibited by α-cyano-4-hydroxycinnamate, phloretin and partly by 4,4´-di-isothiocyanostilbene-2,2´-disulphonic acid. Similar to MCT1, monocarboxylate transport via MCT4 was sensitive to inhibition by the thiol reagent p-chloromercuribenzoesulphonic acid.
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Chou, Chung-Hsien, Chun-Yu Fan Chiang, Cheng-Chieh Yang, Ying-Chieh Liu, Sih-Rou Chang, Kuo-Wei Chang, and Shu-Chun Lin. "miR-31-NUMB Cascade Modulates Monocarboxylate Transporters to Increase Oncogenicity and Lactate Production of Oral Carcinoma Cells." International Journal of Molecular Sciences 22, no. 21 (October 29, 2021): 11731. http://dx.doi.org/10.3390/ijms222111731.
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Oral squamous cell carcinoma (OSCC) is among the leading causes of cancer-associated death worldwide. miR-31 is an oncogenic miRNA in OSCC. NUMB is an adaptor protein capable of suppressing malignant transformation. Disruption of the miR-31-NUMB regulatory axis has been demonstrated in malignancies. Mitochondrial dysfunction and adaptation to glycolytic respiration are frequent events in malignancies. Monocarboxylate transporters (MCTs) function to facilitate lactate flux in highly glycolytic cells. Upregulation of MCT1 and MCT4 has been shown to be a prognostic factor of OSCC. Here, we reported that miR-31-NUMB can modulate glycolysis in OSCC. Using the CRISPR/Cas9 gene editing strategy, we identified increases in oncogenic phenotypes, MCT1 and MCT4 expression, lactate production, and glycolytic respiration in NUMB-deleted OSCC subclones. Transfection of the Numb1 or Numb4 isoform reversed the oncogenic induction elicited by NUMB deletion. This study also showed, for the first time, that NUMB4 binds MCT1 and MCT4 and that this binding increases their ubiquitination, which may decrease their abundance in cell lysates. The disruptions in oncogenicity and metabolism associated with miR-31 deletion and NUMB deletion were partially rescued by MCT1/MCT4 expression or knockdown. This study demonstrated that NUMB is a novel binding partner of MCT1 and MCT4 and that the miR-31-NUMB-MCT1/MCT4 regulatory cascade is present in oral carcinoma.
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Moore, Nigel P., Catherine A. Picut, and Jeffrey H. Charlap. "Localisation of Lactate Transporters in Rat and Rabbit Placentae." International Journal of Cell Biology 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/2084252.
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The distribution of monocarboxylate transporter (MCT) isoforms 1 and 4, which mediate the plasmalemmal transport of l-lactic and pyruvic acids, has been identified in the placentae of rats and rabbits at different ages of gestation. Groups of three pregnant Sprague-Dawley rats and New Zealand White rabbits were sacrificed on gestation days (GD) 11, 14, 18, or 20 and on GD 13, 18, or 28, respectively. Placentae were removed and processed for immunohistochemical detection of MCT1 and MCT4. In the rat, staining for MCT1 was associated with lakes and blood vessels containing enucleated red blood cells (maternal vessels) while staining for MCT4 was associated with vessels containing nucleated red blood cells (embryofoetal vessels). In the rabbit, staining for MCT1 was associated with blood vessels containing nucleated red blood cells while staining for MCT4 was associated with vessels containing enucleated red blood cells. Strength of staining for MCT1 decreased during gestation in both species, but that for MCT4 was stronger than that for MCT1 and was consistent between gestation days. The results imply an opposite polarity of MCT1 and MCT4 across the trophoblast between rat and rabbit.
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Bergersen, Linda Hildegard. "Lactate Transport and Signaling in the Brain: Potential Therapeutic Targets and Roles in Body—Brain Interaction." Journal of Cerebral Blood Flow & Metabolism 35, no. 2 (November 26, 2014): 176–85. http://dx.doi.org/10.1038/jcbfm.2014.206.
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Lactate acts as a ‘buffer’ between glycolysis and oxidative metabolism. In addition to being exchanged as a fuel by the monocarboxylate transporters (MCTs) between cells and tissues with different glycolytic and oxidative rates, lactate may be a ‘volume transmitter’ of brain signals. According to some, lactate is a preferred fuel for brain metabolism. Immediately after brain activation, the rate of glycolysis exceeds oxidation, leading to net production of lactate. At physical rest, there is a net efflux of lactate from the brain into the blood stream. But when blood lactate levels rise, such as in physical exercise, there is net influx of lactate from blood to brain, where the lactate is used for energy production and myelin formation. Lactate binds to the lactate receptor GPR81 aka hydroxycarboxylic acid receptor (HCAR1) on brain cells and cerebral blood vessels, and regulates the levels of cAMP. The localization and function of HCAR1 and the three MCTs (MCT1, MCT2, and MCT4) expressed in brain constitute the focus of this review. They are possible targets for new therapeutic drugs and interventions. The author proposes that lactate actions in the brain through MCTs and the lactate receptor underlie part of the favorable effects on the brain resulting from physical exercise.
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Fanelli, Albertina, Evelyn F. Grollman, Dian Wang, and Nancy J. Philp. "MCT1 and its accessory protein CD147 are differentially regulated by TSH in rat thyroid cells." American Journal of Physiology-Endocrinology and Metabolism 285, no. 6 (December 2003): E1223—E1229. http://dx.doi.org/10.1152/ajpendo.00172.2003.
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In thyroid cells, basal and TSH-stimulated glycolysis is associated with lactic acid efflux. In this report, we address whether monocarboxylate transporters (MCTs) are present in thyroid tissue for exporting excess lactic acid generated by aerobic glycolysis. Using immunostaining techniques, we show that MCT4 localizes with its accessory protein CD147 in the basolateral membrane of rat thyroid follicular cells. In cultured rat thyroid (FRTL-5) cells, MCT1 rather than MCT4 is expressed. CD147 colocalizes and coimmunoprecipitates with MCT1. TSH upregulates MCT1/CD147 expression as a function of time through a cAMP-dependent mechanism as forskolin reproduces the effect of TSH. TSH enhances protein expression of both MCT1 and CD147 in FRTL-5 cells. Whereas MCT1 protein expression is controlled at the level of transcription, CD147 protein expression is regulated by a posttranscriptional mechanism. Results of these studies suggest that hormone stimulation of lactate transport is mediated by regulating MCT1 transcription.
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Jansen, Sarah, Tahereh Esmaeilpour, Marie Pantaleon, and Peter L. Kaye. "Glucose affects monocarboxylate cotransporter (MCT) 1 expression during mouse preimplantation development." Reproduction 131, no. 3 (March 2006): 469–79. http://dx.doi.org/10.1530/rep.1.00953.
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Cleavage-stage embryos have an absolute requirement for pyruvate and lactate, but as the morula compacts, it switches to glucose as the preferred energy source to fuel glycolysis. Substrates such as glucose, amino acids, and lactate are moved into and out of cells by facilitated diffusion. In the case of lactate and pyruvate, this occurs via H+-monocarboxylate cotransporter (MCT) proteins. To clarify the role of MCT in development, transport characteristics fordl-lactate were examined, as were mRNA expression and protein localisation for MCT1 and MCT3, using confocal laser scanning immunofluorescence in freshly collected and cultured embryos. Blastocysts demonstrated significantly higher affinity fordl-lactate than zygotes (Km20 ± 10 vs 87 ± 35 mmol lactate/l;P= 0.03 by linear regression) but was similar for all stages. For embryos derivedin vivoand those cultured with glucose, MCT1 mRNA was present throughout preimplantation development, protein immunoreactivity appearing diffuse throughout the cytoplasm with brightest intensity in the outer cortical region of blastomeres. In expanding blastocysts, MCT1 became more prominent in the cytoplasmic cortex of blastomeres, with brightest intensity in the polar trophectoderm. Without glucose, MCT1 mRNA was not expressed, and immunoreactivity dramatically reduced in intensity as morulae died. MCT3 mRNA and immunoreactivity were not detected in early embryos. The differential expression of MCT1 in the presence or absence of glucose demonstrates that it is important in the critical regulation of pH and monocarboxylate transport during preimplantation development, and implies a role for glucose in the control of MCT1, but not MCT3, expression.
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Bovenzi, Cory D., James Hamilton, Patrick Tassone, Jennifer Johnson, David M. Cognetti, Adam Luginbuhl, William M. Keane, et al. "Prognostic Indications of Elevated MCT4 and CD147 across Cancer Types: A Meta-Analysis." BioMed Research International 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/242437.
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Background. Metabolism in the tumor microenvironment can play a critical role in tumorigenesis and tumor aggression. Metabolic coupling may occur between tumor compartments; this phenomenon can be prognostically significant and may be conserved across tumor types. Monocarboxylate transporters (MCTs) play an integral role in cellular metabolism via lactate transport and have been implicated in metabolic synergy in tumors. The transporters MCT1 and MCT4 are regulated via expression of their chaperone, CD147.Methods. We conducted a meta-analysis of existing publications on the relationship between MCT1, MCT4, and CD147 expression and overall survival and disease-free survival in cancer, using hazard ratios derived via multivariate Cox regression analyses.Results. Increased MCT4 expressions in the tumor microenvironment, cancer cells, or stromal cells were all associated with decreased overall survival and decreased disease-free survival (p<0.001for all analyses). Increased CD147 expression in cancer cells was associated with decreased overall survival and disease-free survival (p<0.0001for both analyses). Few studies were available on MCT1 expression; MCT1 expression was not clearly associated with overall or disease-free survival.Conclusion. MCT4 and CD147 expression correlate with worse prognosis across many cancer types. These results warrant further investigation of these associations.
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Metz, Lore, Jacques Mercier, Angelo Tremblay, Natalie Alméras, and Denis R. Joanisse. "Effect of weight loss on lactate transporter expression in skeletal muscle of obese subjects." Journal of Applied Physiology 104, no. 3 (March 2008): 633–38. http://dx.doi.org/10.1152/japplphysiol.00681.2007.
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The effects of weight loss on skeletal muscle lactate transporter [monocarboxylate transporter (MCT)] expression in obese subjects were investigated to better understand how lactate transporter metabolism is regulated in insulin-resistant states. Ten obese subjects underwent non-macronutrient-specific energy restriction for 15 wk. Anthropometric measurements and a needle biopsy of the vastus lateralis muscle before and after the weight loss program were performed. Enzymatic activity, fiber type distribution, and skeletal muscle MCT protein expression were measured. Muscle from nonobese control subjects was used for comparison of MCT levels. The program induced a weight loss of 9.2 ± 1.6 kg. Compared with controls, muscle from obese subjects showed a strong tendency ( P = 0.06) for elevated MCT4 expression (+69%) before the weight loss program. MCT4 expression decreased (−7%) following weight loss to reach levels that were not statistically different from control levels. There were no differences in MCT1 expression between controls and obese subjects before and after weight loss. A highly predictive regression model ( R2 = 0.93), including waist circumference, citrate synthase activity, and percentage of type 1 fibers, was found to explain the highly variable MCT1 response to weight loss in the obese group. Therefore, in obesity, MCT1 expression appears linked both to changes in oxidative parameters and to changes in visceral adipose tissue content. The strong tendency for elevated expression of muscle MCT4 could reflect the need to release greater amounts of muscle lactate in the obese state, a situation that would be normalized with weight loss as indicated by decreased MCT4 levels.
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Sepponen, K., N. Koho, E. Puolanne, M. Ruusunen, and A. R. Pösö. "Distribution of monocarboxylate transporter isoforms MCT1, MCT2 and MCT4 in porcine muscles." Acta Physiologica Scandinavica 177, no. 1 (December 19, 2002): 79–86. http://dx.doi.org/10.1046/j.1365-201x.2003.01051.x.
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Hashimoto, Takeshi, Shinya Masuda, Sadayoshi Taguchi, and George A. Brooks. "Immunohistochemical analysis of MCT1, MCT2 and MCT4 expression in rat plantaris muscle." Journal of Physiology 567, no. 1 (August 2005): 121–29. http://dx.doi.org/10.1113/jphysiol.2005.087411.
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Bonglack, Emmanuela N., Joshua E. Messinger, Jana M. Cable, James Ch’ng, K. Mark Parnell, Nicolás M. Reinoso-Vizcaíno, Ashley P. Barry, et al. "Monocarboxylate transporter antagonism reveals metabolic vulnerabilities of viral-driven lymphomas." Proceedings of the National Academy of Sciences 118, no. 25 (June 14, 2021): e2022495118. http://dx.doi.org/10.1073/pnas.2022495118.
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Epstein–Barr virus (EBV) is a ubiquitous herpesvirus that typically causes asymptomatic infection but can promote B lymphoid tumors in the immune suppressed. In vitro, EBV infection of primary B cells stimulates glycolysis during immortalization into lymphoblastoid cell lines (LCLs). Lactate export during glycolysis is crucial for continued proliferation of many cancer cells—part of a phenomenon known as the “Warburg effect”— and is mediated by monocarboxylate transporters (MCTs). However, the role of MCTs has yet to be studied in EBV-associated malignancies, which display Warburg-like metabolism in vitro. Here, we show that EBV infection of B lymphocytes directly promotes temporal induction of MCT1 and MCT4 through the viral proteins EBNA2 and LMP1, respectively. Functionally, MCT1 was required for early B cell proliferation, and MCT4 up-regulation promoted acquired resistance to MCT1 antagonism in LCLs. However, dual MCT1/4 inhibition led to LCL growth arrest and lactate buildup. Metabolic profiling in LCLs revealed significantly reduced oxygen consumption rates (OCRs) and NAD+/NADH ratios, contrary to previous observations of increased OCR and unaltered NAD+/NADH ratios in MCT1/4-inhibited cancer cells. Furthermore, U-13C6–glucose labeling of MCT1/4-inhibited LCLs revealed depleted glutathione pools that correlated with elevated reactive oxygen species. Finally, we found that dual MCT1/4 inhibition also sensitized LCLs to killing by the electron transport chain complex I inhibitors phenformin and metformin. These findings were extended to viral lymphomas associated with EBV and the related gammaherpesvirus KSHV, pointing at a therapeutic approach for targeting both viral lymphomas.
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Brauchi, Sebastian, Maria C. Rauch, Ivan E. Alfaro, Christian Cea, Ilona I. Concha, Dale J. Benos, and Juan G. Reyes. "Kinetics, molecular basis, and differentiation of l-lactate transport in spermatogenic cells." American Journal of Physiology-Cell Physiology 288, no. 3 (March 2005): C523—C534. http://dx.doi.org/10.1152/ajpcell.00448.2003.
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Round spermatid energy metabolism is closely dependent on the presence of l-lactate in the external medium. This l-lactate has been proposed to be supplied by Sertoli cells in the seminiferous tubules. l-Lactate, in conjunction with glucose, modulates intracellular Ca2+ concentration in round spermatids and pachytene spermatocytes. In spite of this central role of l-lactate in spermatogenic cell physiology, the mechanism of l-lactate transport, as well as possible differentiation during spermatogenesis, has not been studied in these cells. By measuring radioactive l-lactate transport and intracellular pH (pHi) changes with pHi fluorescent probes, we show that these cells transport l-lactate using monocarboxylate-H+ transport (MCT) systems. RT-PCR, in situ mRNA hybridization, and immunocyto- and immunohistochemistry data show that pachytene spermatocytes express mainly the MCT1 and MCT4 isoforms of the transporter (intermediate- and low-affinity transporters, respectively), while round spermatids, besides MCT1 and MCT4, also show expression of the MCT2 isoform (high-affinity transporter). These molecular data are consistent with the kinetic data of l-lactate transport in these cells demonstrating at least two transport components for l-lactate. These separate transport components reflect the ability of these cells to switch between the generation of glycolytic l-lactate in the presence of external glucose and the use of l-lactate when this substrate is available in the external environment. The supply of these substrates is regulated by the hormonal control of Sertoli cell glycolytic activity.