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Monocarboxylate transporters (MCTs) shuttle molecules, including L-lactate, involved in metabolism and cell signaling of the central nervous system. Astrocyte-specific MCT4 is a key component of the astrocyte-neuron lactate shuttle (ANLS) and is important for neuroplasticity and learning of the hippocampus. However, the importance of astrocyte-specific MCT4 in neuroplasticity of the M1 primary motor cortex remains unknown. In this study, we investigated astrocyte-specific MCT4 in motor learning and neuroplasticity of the M1 primary motor cortex using a cell-type specific shRNA knockdown of MCT4. Knockdown of astrocyte-specific MCT4 resulted in impaired motor performance and learning on the accelerating rotarod. In addition, MCT4 knockdown was associated with a reduction of neuronal dendritic spine density and spine width and decreased protein expression of PSD95, Arc, and cFos. Using near-infrared-conjugated 2-deoxyglucose uptake as a surrogate marker for neuronal activity, MCT4 knockdown was also associated with decreased neuronal activity in the M1 primary motor cortex and associated motor regions including the dorsal striatum and ventral thalamus. Our study supports a potential role for astrocyte-specific MCT4 and the ANLS in the neuroplasticity of the M1 primary motor cortex. Targeting MCT4 may serve to enhance neuroplasticity and motor repair in several neurological disorders, including Parkinson's disease and stroke.

We combined game activity analyses with skeletal muscle phenotypes and comprehensive physiological testing to elucidate factors of importance for physical performance in elite women's football. GPS-data from an experimental game, sprint and endurance testing, and muscle tissue analysis of metabolic enzyme activity, protein expression and fiber type composition were completed for international top-level women players (n = 20; age; 23 ± 4 yrs, height; 166 ± 10 cm, weight; 60 ± 8 kg; VO2max ; 51 ± 6 ml/min/kg). Muscle monocarboxylate transporter 4 (MCT4) protein expression explained 46% of the variance in total game distance, while the ability to maintain high-intensity running (HIR) during the final 15 min of the game correlated to myosin heavy chain 1 (MHCI) and Na+-K+ ATPase β1, FXYD1 (phospholemman) and superoxide dismutase 2 (SOD2) protein expression (range: r = 0.51-0.71; all p < 0.05). Total HIR distance correlated with (MHCIIa) protein expression (r = 0.51; p < 0.05), while muscle Na+/H+ exchanger 1 (NHE1) protein explained 36% of the variance in game sprint distance (p < 0.05). Total game accelerations (actions >4 m/s2) correlated with platelet endothelial cell adhesion molecule (PECAM-1) protein expression (r = 0.51; p < 0.05), while concentric knee flexor strength explained 42-62% of the variance in intense decelerations (>4 m/s2). In conclusion, for elite women players' game endurance performance and resistance to end-game fatigue were affected by monocarboxylate transporter expression and myosin heavy chain profile. HIR was also correlated to ion transporter expression and muscle antioxidative capacity. Finally, the importance of functional strength and measures of muscle vascularization in relation to total game decelerations and accelerations, respectively, illustrates the complex physiological demands in elite women's football.

BACKGROUND Glucose transporters (GLUTs) and oxidant metabolism are associated with the mechanism of infertility. This study evaluated the impact of hyperglycemia on glucose and oxidant metabolisms of Sertoli cells (SCs). METHODS This study was an animal study to investigate the expression of messenger RNA monocarboxylate transporter 4 (MCT4), GLUT1, GLUT3, nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione peroxidase, catalase (CAT), and lactate dehydrogenase A (LDHA) of Wistar rats testes that were induced hyperglycemia. Reverse transcription polymerase chain reaction analysis was used. Hyperglycemic state in the Wistar rats was induced by streptozotocin. 24 rats were divided into 3 groups: non-hyperglycemia (control), 2-week, and 4-week hyperglycemic state. All data were collected and analyzed using SPSS version 15.0 (IBM Corp., USA). RESULTS The expression of glucose transporter (GLUT1 and GLUT3), lactate transporter (MCT4), and cellular defense protein against oxidant (Nrf2 and CAT) was significantly increased in the 2-week and 4-week hyperglycemic state groups with p

Tumor cells exhibit higher glycolysis and rely on abnormal energy metabolism to produce ATP, which is essential for cell proliferation and migration. Abnormal energy metabolism inhibition is considered a promising tumor treatment strategy. Xanthatin is an active sesquiterpene lactone isolated from Xanthium strumarium L. This study evaluated the effect of xanthatin on the energy metabolism of human colon cancer cells. The results showed that xanthatin significantly inhibited the migration and invasion of human HT-29 and HCT-116 colon cancer cells. We found that xanthatin effectively reduced the production of ATP and promoted the accumulation of lactate. Xanthatin inhibited glycolysis which may be related to the reduction of glucose transporter 1 (Glut1) and monocarboxylate transporter 4 (MCT4) mRNA and protein levels. Concomitantly, xanthatin promoted complex II activity and oxidative phosphorylation (OXPHOS), resulting in mitochondrial damage and cell death in HT-29 cells. Furthermore, xanthatin inhibited the phosphorylation of mTOR, the phosphorylation of 4E-binding protein 1 (4E-BP1) and c-myc in HT-29 cells. Moreover, rapamycin, a mTOR inhibitor, could enhance the cytotoxicity effect in xanthatin treated HT-29 cells. Additionally, HT-29 cells transfected with si-mTOR aggravated xanthatin induced cell viability inhibition. Based on these results, we observed that the effect of xanthatin on energy metabolism may be related to its inhibition of the mTOR signaling pathway. Collectively, this study provides important insights into xanthatin's anticancer effect, which occurs by regulation of the energy metabolism of human colon cancer cells, and suggest that xanthatin has potential as a botanical drug against abnormal tumor energy metabolism.

Sudden death syndrome (SDS) is an economically important disorder in broiler chickens with unknown aetiology. The aim of the present study was to evaluate the metabolic and molecular alterations related to hypoxia in the myocardium of broiler chickens with SDS. Samples from the cardiac muscle of internal control broiler chickens (ICs) (n = 36) and chickens having died of SDS (n = 36) were obtained during the rearing period. The activities of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) and the concentration of lactate were measured in the cardiac tissue using available commercial kits. The expression of hypoxia-inducing factor 1α (HIF1α), glucose transporter 1 (GLUT1), pyruvate dehydrogenase kinase 4 (PDHK4) and monocarboxylate transporter 4 (MCT4) genes was determined in the myocardium by real-time PCR analysis. The results showed the elevation of lactate level and activities of LDH and CPK in the cardiac muscle of SDS-affected chickens compared with the IC birds (P < 0.05). The cardiac muscle expression of HIF1α, MCT4 and GLUT1 genes was increased, while the PDHK4 mRNA level was decreased in the SDS-affected group compared to those in the IC chickens (P < 0.05). Our results showed that metabolic remodelling associated with hypoxia in the cardiac tissues may have an important role in the pathogenesis of cardiac insufficiency and SDS in broiler chickens.

Glycolysis markers including glucose transporter 1 (GLUT1), monocarboxylate transporter 4 (MCT4), hexokinase 2 (HK2), pyruvate kinase M2 (PKM2) and glucose transporter 4 (GLUT4) play vital roles in head and neck squamous cell carcinoma (HNSCC). However, their prognostic value in HNSCC is still controversial. In this meta-analysis, we searched the PubMed, Web of Science and Cochrane Library databases and included thirty-seven studies (3272 patients) that met the inclusion criteria. Higher expression levels of the glycolysis markers in tumor tissues correlated with poorer overall survival (OS; P < 0.001), disease-free survival (DFS; P = 0.03) and recurrence-free survival (RFS; P < 0.001) of HNSCC patients. Subgroup and sensitivity analyses demonstrated that higher expression levels of GLUT1 (P < 0.001), MCT4 (P = 0.002), HK2 (P = 0.002) and PKM2 (P < 0.001) correlated with poorer OS among HNSCC patients. Higher expression of MCT4 (P < 0.001) and PKM2 (P = 0.008) predicted poorer DFS among HNSCC patients. However, GLUT4 expression levels did not associate with clinical outcomes in HNSCC patients. These results demonstrate that glycolysis markers, such as GLUT1, MCT4, HK2 and PKM2, are potential prognostic predictors and therapeutic targets in HNSCC.

Background: Colorectal cancer (CRC) is currently the third most common cancer type in males and the second most occurring in females. The role of microRNA (miRNA) in the development of colorectal cancer is not fully elucidated. Therefore, understanding the mechanistic interaction between miRNA and their target oncogenes may hold great importance as a possible target for interventional anticancer therapy. Aims: To identify miRNAs that are part of the regulating pathway of Monocarboxylate Transporter-4 (MCT4) and Vascular Endothelial Growth Factor (VEGF) oncogenes. Study Design: We used publicly available prediction tools (e.g. TargetScan, MicroCosm, PicTar, and DIANA-microT-CDS) to identify the possible miRNA that target the two oncogenes. Methodology: We used the GeneMania database to visualize the network and verify gene names and remove ambiguity and duplications. Furthermore, we used miRTarBase database to identify experimentally validated targets which we used to further confirm miRNA-oncogene relationships. Finally, we utilized miR-Mfold web-tool to further visualize the circular structures and the simulated miR-1 and miR-206 targeting arrangements. Results: We found two putative miRNA (miR-1 and miR-206) that may downregulate MCT4 coded by SLC16A3 gene and VEGF which is coded by VEGF gene. We found relationships between the validated target genes of miR-1 and miR-206 through GeneMania which we extracted from the literature. And we elucidated the proposed structure of these two miRNAs through miR-Mfold web-tool. Conclusion: Our results elucidated a novel regulation pathway in CRC cells and may suggest a potential therapeutic approach for CRC therapy. MiR-1 and miR-206 may help cells go to apoptosis and inhibit the angiogenesis of colorectal cancer cells by down-regulation of MCT4 and VEGF proteins in tumor tissues.

Caveolin‐1 (Cav‐1) is the principal structural component of caveolae, and its dysregulation occurs in cancer. However, the role of Cav‐1 in pancreatic cancer (PDAC) tumorigenesis and metabolism is largely unknown. In this study, we aimed to investigate the effect of pancreatic stellate cell (PSC) Cav‐1 on PDAC metabolism and aggression. We found that Cav‐1 is expressed at low levels in PDAC stroma and that the loss of stromal Cav‐1 is associated with poor survival. In PSCs, knockdown of Cav‐1 promoted the production of reactive oxygen species (ROS), while ROS production further reduced the expression of Cav‐1. Positive feedback occurs in Cav‐1‐ROS signalling in PSCs, which promotes PDAC growth and induces stroma‐tumour metabolic coupling in PDAC. In PSCs, positive feedback in Cav‐1‐ROS signalling induced a shift in energy metabolism to glycolysis, with up‐regulated expression of glycolytic enzymes (hexokinase 2 (HK‐2), 6‐phosphofructokinase (PFKP) and pyruvate kinase isozyme type M2 (PKM2)) and transporter (Glut1) expression and down‐regulated expression of oxidative phosphorylation (OXPHOS) enzymes (translocase of outer mitochondrial membrane 20 (TOMM20) and NAD(P)H dehydrogenase [quinone] 1 (NQO1)). These events resulted in high levels of glycolysis products such as lactate, which was secreted by up‐regulated monocarboxylate transporter 4 (MCT4) in PSCs. Simultaneously, PDAC cells took up these glycolysis products (lactate) through up‐regulated MCT1 to undergo OXPHOS, with down‐regulated expression of glycolytic enzymes (HK‐2, PFKP and PKM2) and up‐regulated expression of OXPHOS enzymes (TOMM20 and NQO1). Interrupting the metabolic coupling between the stroma and tumour cells may be an effective method for tumour therapy.

The Warburg effect explains the large amount of lactic acid that tumour cells produce to establish and maintain the acidic characteristics of the tumour microenvironment, which contributes to the migration, invasion and angiogenesis of tumour cells. Monocarboxylate transporter 4 (MCT-4) is a key marker of tumour glycolysis and lactic acid production; however, the role of MCT-4 in breast cancer remains unclear. In the present study, immunohistochemistry (IHC) was used to detect the expression levels of MCT-4 in tissue microarrays of 145 patients diagnosed with invasive ductal breast cancer. The IHC score was used to assess the intensity of staining and the proportion of positive cells. Western blotting and reverse transcription-quantitative PCR were also performed to detect the expression levels of MCT-4 in 30 pairs of breast cancer tissues and adjacent normal tissues. In vitro experiments (EdU incoporation and Cell Counting Kit-8) were performed to examine the role of MCT-4 in the breast cancer MCF-7 cell line. The results of the present study indicated that high MCT-4 expression was associated with pT status (P=0.018), oestrogen receptor (ER) status (P=0.001), progesterone receptor (PR) status (P=0.024), Ki67 index (P=0.043) and androgen receptor (AR) status (P=0.033). In addition, an association between MCT-4 expression and pathological grade was observed (P=0.030). Furthermore, univariate (P=0.027) and multivariate (P=0.001) survival analysis revealed that MCT-4 expression and lymph node involvement were significant independent predictors of breast cancer prognosis. In addition, silencing MCT-4 expression attenuated breast cancer cell viability. Therefore, MCT-4 may be used as a potential predictor of invasive breast cancer.

Background Metabolic reprogramming and altered gene expression mediated by hypoxia-inducible factors play crucial roles during tumour growth and progression. Nevertheless, studies analysing the expression of hypoxia-inducible factor-1α and its downstream targets in Merkel cell carcinoma (MCC) are lacking but are warranted to shed more light on MCC pathogenesis and to potentially provide new therapeutic options. Objectives To analyse the immunohistochemical expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor-A (referred to as VEGF throughout the manuscript), VEGF receptor-2 (VEGFR-2), VEGF receptor-3 (VEGFR-3), glucose transporter-1 (Glut-1), monocarboxylate transporter 4 (MCT4) and carbonic anhydrase IX (CAIX) in primary cutaneous MCC. Methods The 16 paraffin-embedded primary cutaneous MCCs (Merkel cell polyomavirus (McPyV) positive/negative: 11/5) were analysed by immunohistochemistry, namely HIF-1α, VEGF, VEGFR-2 (KDR), VEGFR-3 (FLT4), Glut-1, MCT4 and CAIX. An established quantification score (QS) was applied to quantitate the protein expression by considering the percentage of positive tumour cells (0: 0%; 1: up to 1%; 2: 2-10%; 3: 11-50%; 4: >50%) in relation to the staining intensity (0: negative; 1: low; 2: medium; 3: strong). Results HIF-1α was expressed in all MCCs and predominantly found at the invading edges of tumour margins. The HIF-1α downstream factors Glut-1, MCT4 and CAIX were expressed in 13 of 16 MCC (81%), 14 of 16 MCC (88%) and 16 of 16 MCC (100%), respectively. Interestingly, VEGF and VEGFR-2 were not expressed in tumour cells, whereas VEGFR-3 was expressed in all MCCs. HIF-1α was expressed significantly stronger in McPyV+ tumours (QS: 10.36 ± 2.41) than in McPyV- tumours (QS: 5.40 ± 1.34; P = 0.002). Similarly, VEGFR-3 was also expressed significantly stronger in McPyV+ tumours (QS: 10.00 ± 2.52) than in McPyV- tumours (QS: 5.40 ± 3.43, P = 0.019). Conclusions Our data provide first evidence for a role of HIF-1α in induced metabolic reprogramming contributing to MCC pathogenesis. The metabolic signatures of McPyV+ and McPyV- tumours seem to show relevant differences.

Targeting metabolic reprogramming is an emerging strategy in cancer therapy. However, clinical attempts to target metabolic reprogramming have been proved to be challenging, with metabolic heterogeneity of cancer being one of many reasons that causes treatment failure. Here, we stratified non-small cell lung cancer (NSCLC) cells, mainly lung adenocarcinoma, based on their metabolic phenotypes and demonstrated that the aerobic glycolysis-preference NSCLC cell subtype was resistant to the OXPHOS-targeting inhibitors. We identified that monocarboxylate transporter 4 (MCT4), a lactate transporter, was highly expressed in the aerobic glycolysis-preference subtype with function supporting the proliferation of these cells. Glucose could induce the expression of MCT4 in these cells through a ΔNp63α and Sp1-dependent pathway. Next, we showed that knockdown of MCT4 increased intracellular lactate concentration and induced a reactive oxygen species (ROS)-dependent cellular apoptosis in the aerobic glycolysis-preference NSCLC cell subtype. By scanning a panel of monoclonal antibodies with MCT4 neutralizing activity, we further identified a MCT4 immunoglobulin M (IgM) monoclonal antibody showing capable anti-proliferation efficacy on the aerobic glycolysis-preference NSCLC cell subtype. Our findings indicate that the metabolic heterogeneity is a critical factor for NSCLC therapy and manipulating the expression or function of MCT4 can be an effective strategy in targeting the aerobic glycolysis-preference NSCLC cell subtype., Graphical Abstract, Yang and colleagues stratified NSCLC cells based on their metabolic phenotypes and identified that monocarboxylate transporter 4 (MCT4) was highly expressed in the aerobic glycolysis-preference subtype with function supporting the proliferation of these cells. Additionally, they discovered a MCT4-neutralizing antibody with cell-inhibitory activity on this aerobic glycolysis-preference NSCLC cell subtype.

Monocarboxylate transporter 4 (MCT4) is a high‑capacity lactate transporter in cells and the alteration in MCT4 expression harms cellular survival. The present study investigated whether hypothermia affects tumor necrosis factor‑α (TNF‑α) and MCT4 immunoreactivity in the subfield cornu ammonis 1 (CA1) following cerebral ischemia/reperfusion (IR) in gerbils. Hypothermia was induced for 30 min before and during ischemia. It was found that IR‑induced death of pyramidal neurons was markedly augmented and occurred faster under hyperthermia than under normothermia. TNF‑α immunoreactivity in the pyramidal cells started to increase at 3 h after IR and peaked at 1 day after IR under normothermia. However, in hyperthermic control and sham operated gerbils, TNF‑α immunoreactivity was significantly increased compared with the normothermic gerbils, and IR under hyperthermia caused a more rapid and significant increase in TNF‑α immunoreactivity in pyramidal neurons than under normothermia. In addition, in the normothermic gerbils, MCT4 immunoreactivity began to decrease in pyramidal neurons from 3 h after IR and markedly increased at 1 and 2 days after IR. On the other hand, MCT4 immunoreactivity in pyramidal neurons of the hyperthermic gerbils was significantly increased from 3 h after IR, maintained until 1 day after IR and markedly decreased at 2 days after IR. These results indicate that acceleration of IR‑induced neuronal death under hyperthermia might be closely associated with early alteration of TNF‑α and MCT4 protein expression in the gerbil hippocampus after IR.

Dysregulation of cellular pH is frequent in solid tumours and provides potential opportunities for therapeutic intervention. The acidic microenvironment within a tumour can promote migration, invasion and metastasis of cancer cells through a variety of mechanisms. Pathways associated with the control of intracellular pH that are under consideration for intervention include carbonic anhydrase IX (CAIX), the monocarboxylate transporters (MCT1 and MCT4), the vacuolar-type H+-ATPase proton pump (V-ATPase), and the sodium-hydrogen exchanger 1 (NHE1). This review will describe progress in the development of inhibitors to these targets.

It may be considered that the duration of intervals of high-intensity interval exercise (HIIE) can affect skeletal muscle biochemical and physiological responses. Also, sex-based differences in muscle biochemistry and physiology play a role in different responses to exercise. The aim of this study was to investigate the effects of sex differences on biochemical parameters involved in muscle glycolysis in response to HIIE protocols with short and long-term intervals. Forty male and female Wistar rats (aged 8 weeks, mean weighting 270 g and 225 g, respectively) were divided into HIIE with short-term interval (HIIESh), HIIE with long-term interval (HIIEL), and control groups. The phosphofructokinase (PFK), glycogen synthase 1 (GYS1), monocarboxylate transporter 4 (MCT4), and lactate dehydrogenase (LDH) levels were evaluated in gastrocnemius muscle after a single bout of exercise. The PFK, GYS1, and MCT4 levels were lower in HIIESh and HIIEL groups compared to the control group. However, there was no significant difference between sexes (P

MicroRNAs (miRNAs or miRs) are small noncoding RNAs derived from genome to control target gene expression. Recently we have developed a novel platform permitting high-yield production of bioengineered miRNA agents (BERA). This study is to produce and utilize novel fully-humanized BERA/miR-328-3p molecule (hBERA/miR-328) to delineate the role of miR-328-3p in controlling nutrient uptake essential for cell metabolism. We first demonstrated successful high-level expression of hBERA/miR-328 in bacteria and purification to high degree of homogeneity (>98%). Biologic miR-328-3p prodrug was selectively processed to miR-328-3p to suppress the growth of highly-proliferative human osteosarcoma (OS) cells. Besides glucose transporter protein type 1, gene symbol solute carrier family 2 member 1 (GLUT1/SLC2A1), we identified and verified large neutral amino acid transporter 1, gene symbol solute carrier family 7 member 5 (LAT1/SLC7A5) as a direct target for miR-328-3p. While reduction of LAT1 protein levels by miR-328-3p did not alter homeostasis of amino acids within OS cells, suppression of GLUT1 led to a significantly lower glucose uptake and decline in intracellular levels of glucose and glycolytic metabolite lactate. Moreover, combination treatment with hBERA/miR-328 and cisplatin or doxorubicin exerted a strong synergism in the inhibition of OS cell proliferation. These findings support the utility of novel bioengineered RNA molecules and establish an important role of miR-328-3p in the control of nutrient transport and homeostasis behind cancer metabolism., Graphical abstract Fully-humanized, bioengineered miR-328-3p agent reduces glycolysis through the suppression of protein levels of targeted transporters GLUT1 and LAT1 in human osteosarcoma cells, leading to synergistic antiproliferative effects when combined with chemotherapeutic drugs.Image 1

BackgroundBladder cancer is the 10th most common cancer and most common urothelial malignancy worldwide. Prognostic biomarkers for bladder cancer patients are required for individualized treatment. Monocarboxylate transporter 4 (MCT4), encoded by SLC16A3 gene, is a potential biomarker for bladder cancer because of its crucial role in the lactate efflux in the aerobic glycolysis process. We aimed to study the association between MCT4 expression and the overall survival (OS) of bladder cancer patients.MethodsThe published single-cell RNA sequencing data of 49,869 bladder cancer cells and 15,827 normal bladder mucosa cells and The Cancer Genome Atlas (TCGA) bladder cancer cohort data were used to explore the mRNA expression of SLC16A3 in bladder cancer. Eighty-nine consecutive bladder cancer patients who had undergone radical cystectomy were enrolled as a validation cohort. The expression of MCT4 proteins in bladder cancer specimens was detected using immunohistochemistry staining. The Kaplan–Meier survival analysis and Cox regression were performed to analyze the association between MCT4 protein expression and OS in bladder cancer patients.ResultsSLC16A3 mRNA was upregulated in bladder cancer cells. The upregulated genes in SLC16A3-positive epithelial cells were enriched in the glycolysis process pathway and monocarboxylic acid metabolic process pathway. Patients with high SLC16A3 mRNA expression showed significantly poor OS (p = 0.016). High MCT4 protein expression was also found to be an independent predictor for poor OS in bladder cancer patients (HR: 2.462; 95% CI: 1.202~5.042, p = 0.014). A nomogram was built based on the results of the multivariate Cox analysis.ConclusionBladder cancer with high SLC16A3 mRNA expression has a poor OS. High MCT4 protein expression is an independent prognostic factor for bladder cancer patients who had undergone radical cystectomy.

Simple Summary Subacute rumen acidosis (SARA) often causes significant losses on commercial farms. SARA is mainly caused by endotoxin (LPS) produced by the lysis of Gram-negative bacteria, which causes an inflammatory response. To alleviate the inflammatory response mediated by LPS, it is important to improve animal production performance. Tea tree oil (TTO) is a plant extract that possesses good bactericidal and anti-inflammatory effects. According to this study, LPS can significantly induce inflammatory responses in goat rumen epithelial cells (GRECs), while the addition of TTO could markedly mitigate inflammatory responses mediated by LPS in GRECs. Therefore, it may be useful for the treatment of SARA. Abstract In subacute rumen acidosis (SARA), the rumen epithelium is frequently attacked by endotoxin (LPS), which is caused by the lysis of dead Gram-negative bacteria. However, the rumen epithelium innate immune system can actively respond to the infection. Previous studies have demonstrated that tea tree oil (TTO) has good bactericidal and anti-inflammatory effects. Therefore, the aim of this study was to investigate the effect of TTO on the expression of genes involved in the inflammatory cytokines in goat rumen epithelial cells (GRECs) triggered by LPS. Our study shows that rumen epithelial cells isolated from goat rumen tissue can be cultured in vitro in 0.25% trypsin for a long time. These cells were identified as epithelial cells by the expression of cytokeratin 18, monocarboxylate transporter 4 (MCT4), Na[+]/H[+] hydrogen exchanger 1 (NHE1), putative anion transporter 1 (PAT1), vH+ ATPase B subunit (vH+ ATPase), and anion exchanger 2 (AE2). The mRNA expression of IL-1β, IL-6, TNF-α, TLR-2, NF-κB, CXCL6 and CXCL8 genes was significantly increased when LPS was used compared to untreated controls. In addition, mRNA expression of IL-1β, IL-6, TNF-α, TLR-2, NF-κB, CXCL8, CXCL6 and interferon-induced protein with tetratricopeptide repeats 3 (IFIT3) genes was also significantly higher in the LPS group compared to the 0.05% TTO group. However, the expression of IL-1β, IL-6, TNF-α, TLR-2, CXCL6 and IFIT3 genes was significantly lower in the LPS and 0.05% TTO group compared to the 1 μg/mL LPS group. These results suggest that TTO can inhibit LPS-induced inflammatory cytokines expression in GRECs.

Due to increased lactate production during glucose metabolism, tumor cells heavily rely on efficient lactate transport to avoid intracellular lactate accumulation and acidification. Monocarboxylate transporter 4 (MCT4/SLC16A3) is a lactate transporter that plays a central role in tumor pH modulation. The discovery and optimization of a novel class of MCT4 inhibitors (hit 9a), identified by a cellular screening in MDA-MB-231, is described. Direct target interaction of the optimized compound 18n with the cytosolic domain of MCT4 was shown after solubilization of the GFP-tagged transporter by fluorescence cross-correlation spectroscopy and microscopic studies. In vitro treatment with 18n resulted in lactate efflux inhibition and reduction of cellular viability in MCT4 high expressing cells. Moreover, pharmacokinetic properties of 18n allowed assessment of lactate modulation and antitumor activity in a mouse tumor model. Thus, 18n represents a valuable tool for investigating selective MCT4 inhibition and its effect on tumor biology.

Monocarboxylate transporters (MCTs) shuttle molecules, including L-lactate, involved in metabolism and cell signaling of the central nervous system. Astrocyte-specific MCT4 is a key component of the astrocyte-neuron lactate shuttle (ANLS) and is important for neuroplasticity and learning of the hippocampus. However, the importance of astrocyte-specific MCT4 in neuroplasticity of the M1 primary motor cortex remains unknown. In this study, we investigated astrocyte-specific MCT4 in motor learning and neuroplasticity of the M1 primary motor cortex using a cell-type specific shRNA knockdown of MCT4. Knockdown of astrocyte-specific MCT4 resulted in impaired motor performance and learning on the accelerating rotarod. In addition, MCT4 knockdown was associated with a reduction of neuronal dendritic spine density and spine width and decreased protein expression of PSD95 and Arc. Using near-infrared-conjugated 2-deoxyglucose uptake as a surrogate marker for neuronal activity, MCT4 knockdown was also associated with decreased neuronal activity in the M1 primary motor cortex and associated motor regions including the dorsal striatum and ventral thalamus. Our study supports a potential role for astrocyte-specific MCT4 and the ANLS in the neuroplasticity of the M1 primary motor cortex. Targeting MCT4 may serve to enhance neuroplasticity and motor repair in several neurological disorders, including Parkinson’s disease and stroke.

Pathogenic mitochondrial NADH dehydrogenase (ND) gene mutations enhance the invasion and metastasis of various cancer cells, and they are associated with metastasis in human non-small cell lung cancer (NSCLC). Moreover, monocarboxylate transporter 4 (MCT4) is overexpressed in solid cancers and plays a role in cancer cell proliferation and survival. Here, we report that MCT4 is exclusively expressed in mouse transmitochondrial cybrids with metastasis-enhancing pathogenic ND6 mutations. A high level of MCT4 is also detected in human NSCLC cell lines and tissues predicted to carry pathogenic ND mutations and is associated with poor prognosis in NSCLC patients. MCT4 expression in the cell lines is suppressed by N-acetyl-L-cysteine. Phosphatidylinositol-3 kinase (PI3K), AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) are involved in the regulation of MCT4 expression in the transmitochondrial cybrid cells. An MCT1/4 inhibitor effectively kills NSCLC cells with predicted pathogenic ND mutations, but an MCT1/2 inhibitor does not have the same effect. Thus, MCT4 expression is augmented by pathogenic ND mutations and could be a biomarker and a therapeutic target in pathogenic ND mutation-harbouring metastatic tumours.

Radix Rehmanniae and Cornus Officinalis (RR-CO) have been widely used as “nourishing Yin and tonifying kidney” herb pairs for the treatment of diabetes mellitus (DM) and its complications in traditional Chinese medicine (TCM). Based on the theory of “kidney governing reproduction” in TCM, the aim of this study was to investigate the therapeutic effects of RR-CO on DM-induced reproduction damage through regulating testicular glycolysis. Moreover, the regulation of AGEs/RAGE/HIF-1α axis on the testicular glycolysis process has also been studied. Spontaneous DM model KK-Ay mice were used to investigate the protective effect of RR, CO, RR-CO on DM-induced reproductive disturbances. RR, CO, RR-CO improved DM-induced renal and testicular morphology damages. Moreover, the impaired spermatogenesis, germ cell apoptosis and motility in testis induced upon DM were also attenuated by RR, CO or RR-CO, accompanied by an increased level of glycolysis metabolomics such as l-lactate, d-Fructose 1,6-bisphosphate, etc. Meanwhile, glucose membrane transporters (GLUT1, GLUT3), monocarboxylate transporter 4 (MCT4) expression, lactate dehydrogenase (LDH) activity, HIF-1α were upregulated by RR, CO and RR-CO treatment compared with the model group, whereas AGE level and RAGE expression were decreased with the drug administration. The RR-CO group was associated with superior protective effects in comparison to RR, CO use only. Aminoguanidine (Ami) and FPS-ZM1, the AGEs and RAGE inhibitors, were used as a tool drug to study the mechanism, showing different degrees of protection against DM-induced reproductive damage. This work preliminarily sheds light on the herb pair RR-CO exhibited favorable effects against DM-induced reproductive disturbances through enhancing testicular glycolysis, which might be mediated by AGEs/RAGE/HIF-1α axis.

Chronic pancreatitis (CP) is a precancerous condition associated with pancreatic ductal adenocarcinoma (PDAC), but its evolutionary mechanism is unclear. Pancreatic stellate cells (PSCs) are closely related to the occurrence and development of CP and PDAC, but it is not clear whether PSCs play a key role in this “inflammation-cancer transition”. Our research found that co-culture with activated PSCs promoted the proliferation, migration and invasion of normal pancreatic duct epithelial cells and pancreatic cancer cells. At the same time, activated PSCs had a significant effect on the expression of the glycolysis markers (pyruvate kinase M2, lactate dehydrogenase A, glucose transporter 1, hexokinase-II and monocarboxylate transporter 4; PKM2, LDHA, GLUT1, HK2 and MCT4) in normal pancreatic duct epithelial cells and pancreatic cancer cells and increased lactic acid production and glucose consumption in these two cells. In vivo experiments showed that the expression of the glycolysis markers in pancreatic duct epithelial cells and the marker protein (α-SMA) of activated PSCs in the pancreatic duct peripancreatic interstitium were higher in pancreatic cancer tissues and chronic pancreatitis tissues than in normal pancreatic tissues in both animals and humans. In addition, analysis of human tissue specimens showed that there is a correlation between the expression of glycolysis markers and α-SMA. These findings indicate that activated PSCs play an important role in the development and progression of chronic pancreatitis into pancreatic cancer by regulating and promoting aerobic glycolysis. Our research provides a new theoretical basis for further understanding the mechanism of CP malignancy and the selection of targets for reversing CP malignancy.

Alterations in cellular metabolism may contribute to tumor proliferation and survival. Upregulation of the facilitative glucose transporter (GLUT) plays a key role in promoting cancer. GLUT5 mediates modulation of fructose utilization, and its overexpression has been associated with poor prognosis in several cancers. However, its metabolic regulation remains poorly understood. Here, we demonstrated elevated GLUT5 expression in human cholangiocarcinoma (CCA), using RNA sequencing data from samples of human tissues and cell lines, as compared to normal liver tissues or a cholangiocyte cell line. Cells exhibiting high-expression of GLUT5 showed increased rates of cell proliferation and ATP production, particularly in a fructose-supplemented medium. In contrast, GLUT5 silencing attenuated cell proliferation, ATP production, cell migration/invasion, and improved epithelial–mesenchymal transition (EMT) balance. Correspondingly, fructose consumption increased tumor growth in a nude mouse xenograft model, and GLUT5 silencing suppressed growth, supporting the tumor-inhibitory effect of GLUT5 downregulation. Furthermore, in the metabolic pathways of fructolysis-Warburg effect, the expression levels of relative downstream genes, including ketohexokinase (KHK), aldolase B (ALDOB), lactate dehydrogenase A (LDHA), and monocarboxylate transporter 4 (MCT4), as well as hypoxia-inducible factor 1 alpha (HIF1A), were altered in a GLUT5 expression-dependent manner. Taken together, these findings indicate that GLUT5 could be a potential target for CCA therapeutic approach via metabolic regulation.

Context Lactate is the preferred energy substrate for developing testicular germ cells. Diabetes is associated with impaired testicular lactate transport/utilisation, and poor sexual behaviour. Objective To examine the effects of metformin on parameters involved in testicular lactate production, transport/utilisation, and sexual behaviour in diabetic state. Methods Male Sprague-Dawley rats were assigned into normal control (NC), diabetic control (DC), and metformin-treated diabetic group (n = 6/group). Metformin (300 mg/kg b.w./day) was administrated orally for 4 weeks. Results Intra-testicular glucose and lactate levels, and lactate dehydrogenase (LDH) activity increased, while the mRNA transcript levels of genes responsible for testicular glucose and lactate transport/utilisation (glucose transporter 3, monocarboxylate transporter 4 (MCT4), MCT2, and LDH type C) decreased in DC group. Furthermore, penile nitric oxide increased, while cyclic guanosine monophosphate decreased, with impaired sexual behaviour in DC group. Treatment with metformin improved these parameters. Conclusions Metformin increases testicular lactate transport/utilisation and improves sexual behaviour in diabetic state.

To study adaptation of largemouth bass (Micropterus salmoides) to hypoxic stress, we investigated physiological responses and lactate metabolism of the fish under acute hypoxia. The objectives of this study were to (a) observe changes in glucose, glycogen, and lactate content; (b) detect the activity of lactate dehydrogenase (LDH) in serum, brain, heart, and liver tissues; and (c) quantify the dynamic gene expression of AMP activated protein kinase alpha (AMPKα), hypoxia-inducible factor-1 alpha (HIF-1α), monocarboxylate transporter 1 (MCT1), monocarboxylate transporter 4 (MCT4), and lactate dehydrogenase-a (LDHa) following exposure to hypoxia. The fish were subjected to two hypoxia stresses (dissolved oxygen [DO] 1.20 ± 0.2 mg/L and 3.50 ± 0.3 mg/L, respectively) for 24 h. Our results showed that hypoxic stress significantly increased the decomposition of liver glycogen and significantly increased the concentration of blood glucose; however, the muscle glycogen content was not significantly decreased, which indicates that liver glycogen was the main energy source under acute hypoxia. Moreover, hypoxia led to accumulation of a large amount of lactic acid in tissues, possibly due to the activity of lactic acid dehydrogenase, but this process was delayed in the heart and brain relative to the liver. Additionally, hypoxia induced the expression of AMPKα, HIF-1α, MCT1, MCT4, and LDHa, suggesting that glycometabolism had switched from aerobic to anaerobic. Our results contribute to a better understanding of the molecular mechanisms of the response to hypoxia in largemouth bass.

Introduction Thyroid cancer (TC) is an important common endocrine malignancy, and its incidence has increased in the past decades. The current TC diagnosis and classification tools are fine-needle aspiration (FNA) and histological examination following thyroidectomy. The metabolite profile alterations of thyroid cells (oncometabolites) can be considered for current TC diagnosis and management protocols. Methods This systematic review focuses on metabolite alterations within the plasma, FNA specimens, and tissue of malignant TC contrary to benign, goiter, or healthy TC samples. A systematic search of MEDLINE (PubMed), Scopus, Embase, and Web of Science databases was conducted, and the final 31 studies investigating metabolite biomarkers of TC were included. Results A total of 15 targeted studies and 16 untargeted studies revealed several potential metabolite signatures of TC such as glucose, fructose, galactose, mannose, 2-keto-d-gluconic acid and rhamnose, malonic acid and inosine, cholesterol and arachidonic acid, glycosylation (immunoglobulin G [IgG] Fc-glycosylation), outer mitochondrial membrane 20 (TOMM20), monocarboxylate transporter 4 (MCT4), choline, choline derivatives, myo-/scyllo-inositol, lactate, fatty acids, several amino acids, cell membrane phospholipids, estrogen metabolites such as 16 alpha-OH E1/2-OH E1 and catechol estrogens (2-OH E1), and purine and pyrimidine metabolites, which were suggested as the TC oncometabolite. Conclusion Citrate was suggested as the first most significant biomarker and lactate as the second one. Further research is needed to confirm these biomarkers as the TC diagnostic oncometabolite.

Apelin is the endogenous ligand for the G protein-coupled receptor APJ. Both apelin and APJ receptor are distributed in vascular smooth muscle cells (VSMCs) and play important roles in the cardiovascular system. Our previous reports have indicated that apelin-13 promoted the proliferation of VSMCs, but its exact mechanism remains to be further explored. The results of the present study demonstrated that the Warburg effect plays a pivotal role in apelin-13-induced human aortic vascular smooth muscle cells (HA-VSMCs) proliferation. Apelin-13 promoted the expression of glucose transporter type 1 (GLUT1), pyruvate kinase 2 (PKM2), lactate dehydrogenase A (LDHA), monocarboxylate transporter 1 (MCT1), and monocarboxylate transporter 4 (MCT4) in a dose- and time-dependent manner. Moreover, apelin-13 increased the extracellular, intracellular lactate level, and decreased adenosine triphosphate level in HA-VSMCs. Furthermore, siRNA-PKM2 reversed extracellular and intracellular lactate generation and inhibited the proliferation of HA-VSMCs induced by apelin-13. Downregulation of LDHA also significantly prevented extracellular and intracellular lactate generation and inhibited the proliferation of HA-VSMCs induced by apelin-13. Taken together, our results demonstrated a novel mechanism for HA-VSMCs proliferation induced by apelin-13 via Warburg effect.