Monocarboxylate Transporter Research Articles

Maternal Limosilactobacillus reuteri rescues social and emotional recognition behavior in an environmental mouse model of autism

Introduction: Polybrominated diphenyl ethers (PBDEs) are thyroid disrupting chemicals with adverse neurodevelopmental effects in children. Our group has previously shown that PBDEs produce autism (ASD)-like traits (Kozlova et al. 2022 Arch Tox; PMID: 34687351) in combination with reduced hypothalamic oxytocin expression in developmentally exposed female mice offspring. Limosilactobacillus reuteri (LR) is a beneficial probiotic that can increase oxytocin and thyroid hormones (THs) in other ASD mouse models. Therefore, we hypothesized that LR would ameliorate PBDE-induced deficits in social behavior, oxytocin and thyroid status. Methods: C57BL/6N dams (n=8/group) were dosed with a commercial mixture of PBDE congeners, DE-71, at 0.1 mg/kg/d (DE-71), or corn oil vehicle control (VEH/CON) during preconception, gestation and lactation). Dams were gavaged with L. reuteri (LR) ATCC-PTA-6475 at 107-108 CFU/mL (gift of Biogaia, Sweden). Cohort 1 pups (C1) received LR via dam until weaning (PND 21). Cohort 2 pups (C2) continued to receive gavage of LR post-weaning, daily, through 6 mo of age. Results: Fecal microbiome analysis confirmed colonization of LR in dams after 25 doses and their offspring at postnatal day 22 and 40. Beta diversity PCoA using unweighted Unifrac revealed differences in microbial communities in 6 month old female (p<.05-.01) and male offspring (apparent) between DE-71 and VEH/CON (C2). LR treatment normalized DE-71-induced abnormal social novelty preference (30 min retention) in adult male (p<.01) and females (p<.05) and long-term social recognition memory (24 h retention) in adult C2 females (p<.001). Using an emotional recognition task DE-71-exposed C2 male and female offspring were unable to distinguish between emotional state of stimulus mice but LR supplementation normalized the DE-71-induced deficits in C2 males (p<.01) and females (p<.05). On a marble burying test DE-71 exposed offspring showed abnormally elevated scores compared to VEH/CON, which were normalized by LR treatment only in C1 females (p<.05). In females, maternal LR treatment ameliorated DE-71-induced locomotor hyperactivity in C1. Since social behavior involves discrimination between social odors we also investigated the effects of DE-71 and LR treatment on olfactory discrimination ability. LR treatment ameliorated DE-71 effects compared to VEH/CON, i.e., reduced dishabituation from social odor 1 to 2 in males and female (p<.0001). Single molecule in situ hybridization performed on paraventricular hypothalamic nucleus (PVN) sections revealed upregulation of thyroid hormone transporter monocarboxylate transporter 8 (Mct8) and downregulation of iodothyronine deiodinase 3 (Dio3) on oxytocin-positive neurons in DE-71 vs VEH/CON in C2 females. Dio3 expression was normalized in DE-71+LR. Conclusions: These results indicate that early life exposure to PBDEs alters thyroid hormone system genes in PVN neurons that express oxytocin, suggesting that PBDEs may alter ASD-relevant behavior via brain thyroid signaling. In addition, maternal LR supplementation provides normalization in a sex-dependent manner. This work is supported by a Danone North America Gut Microbiome, Yogurt and Probiotics Fellowship Grant and a University of California President's Pre-Professoriate Fellowship to E.V.K and an NIH/NIGMS R35GM124724 to A.H. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Lactate-induced metabolic remodeling and myofiber type transitions via activation of the Ca2+-NFATC1 signaling pathway.

Lactate can serve as both an energy substrate and a signaling molecule, exerting diverse effects on skeletal muscle physiology. Due to the apparently positive effects, it would be interesting to consider it as a sports supplement. However, the mechanism behind these effects are yet to be comprehensively understood. In this study, we observed that lactate administration could improve the ability of antifatigue, and we further found that lactate upregulated the expression of myosin heavy chain (MYHC I) and MYHC IIa, while downregulating the expression of MYHC IIb. Besides, transcriptomics and metabolomics revealed significant changes in the metabolic profile of gastrocnemius muscle following lactate administration. Furthermore, lactate enhanced the activities of metabolic enzymes, including HK, LDHB, IDH, SDM, and MDH, and promoted the expression of lactate transport-related proteins MCT1 and CD147, thereby improving the transport and utilization of lactate in both vivo and vitro. More importantly, lactate administration increased cellular Ca2+ concentration and facilitated nuclear translocation of nuclear factor of activated T cells (NFATC1) in myotubes, whereas inhibition of NFATC1 significantly attenuated the effects of lactate treatment on NFATC1 nuclear translocation and MyHC expression. Our results elucidate the ability of lactate to induce metabolic remodeling in skeletal muscle and promote myofiber-type transitions by activating the Ca2+-NFATC1 signaling pathway. This study is useful in exploring the potential of lactate as a nutritional supplement for skeletal muscle adaptation and contributing to a mechanistic understanding of the central role of lactate in exercise physiology.

Microencapsulated Lactobacillus plantarum promotes intestinal development through gut colonization of layer chicks

The effects of Lactobacillus plantarum in microencapsulation (LPM) on intestinal development in layer chicks were investigated in this study, as well as the colonization of L. plantarum in the gut. A total of 480 healthy Hy-Line Brown layer chicks at 0 d old were randomly divided into 4 groups (8 replicates each treatment), and the diets of these birds were supplemented with nothing (control), L. plantarum (0.02 g/kg feed; 109 CFU/kg feed), LPM (1.0 g/kg feed; 109 CFU/kg feed) and wall material of LPM (WM; 0.98 g/kg feed), respectively. Compared to control, LPM improved growth performance and intestinal development of layer chicks, evidenced by significantly increased body weight, average daily gain, average daily feed intake, villus height, villus height/crypt depth, as well as weight and length of the duodenum, jejunum and ileum (P < 0.05). These results could be attributed to the increased colonization of L. plantarum in the gut, which was verified by significant increases in lactic acid content, viable counts in chyme and mucosa (P < 0.05), as well as a visible rise in number of strains labeled with fluorescein isothiocyanate. Meanwhile, the relative abundances of Lactobacillus and Bifidobacterium significantly increased in response to microencapsulated L. plantarum supplementation (P < 0.05), accompanied by the significant up-regulation of colonization related genes (P < 0.05), encoding solute carrier family, monocarboxylate transporter, activin A receptor, succinate receptor and secretogranin II. To sum up, microencapsulated L. plantarum supplementation promoted intestinal development, which could be attributed to the enhancement of L. plantarum colonization in the intestine through the mutual assistance of Bifidobacterium and interactions with colonization related transmembrane proteins.

The ketone body β-Hydroxybutyrate as a fuel source of chondrosarcoma cells

Chondrosarcoma (CS) is a malignant bone tumor arising from cartilage-producing cells. The conventional subtype of CS typically develops within a dense cartilaginous matrix, creating an environment deficient in oxygen and nutrients, necessitating metabolic adaptation to ensure proliferation under stress conditions. Although ketone bodies (KBs) are oxidized by extrahepatic tissue cells such as the heart and brain, specific cancer cells, including CS cells, can undergo ketolysis. In this study, we found that KBs catabolism is activated in CS cells under nutrition-deprivation conditions. Interestingly, cytosolic β-hydroxybutyrate dehydrogenase 2 (BDH2), rather than mitochondrial BDH1, is expressed in these cells, indicating a specific metabolic adaptation for ketolysis in this bone tumor. The addition of the KB, β-Hydroxybutyrate (β-HB) in serum-starved CS cells re-induced the expression of BDH2, along with the key ketolytic enzyme 3-oxoacid CoA-transferase 1 (OXCT1) and monocarboxylate transporter-1 (MCT1). Additionally, internal β-HB production was quantified in supplied and starved cells, suggesting that CS cells are also capable of ketogenesis alongside ketolysis. These findings unveil a novel metabolic adaptation wherein nutrition-deprived CS cells utilize KBs for energy supply and proliferation.

Adaptive Metabolic Responses Facilitate Blood-Brain Barrier Repair in Ischemic Stroke via BHB-Mediated Epigenetic Modification of ZO-1 Expression.

Adaptive metabolic responses and innate metabolites hold promising therapeutic potential for stroke, while targeted interventions require a thorough understanding of underlying mechanisms. Adiposity is a noted modifiable metabolic risk factor for stroke, and recent research suggests that it benefits neurological rehabilitation. During the early phase of experimental stroke, the lipidomic results showed that fat depots underwent pronounced lipolysis and released fatty acids (FAs) that feed into consequent hepatic FA oxidation and ketogenesis. Systemic supplementation with the predominant ketone beta-hydroxybutyrate (BHB) is found to exert discernible effects on preserving blood-brain barrier (BBB) integrity and facilitating neuroinflammation resolution. Meanwhile, blocking FAO-ketogenesis processes by administration of CPT1α antagonist or shRNA targeting HMGCS2 exacerbated endothelial damage and aggravated stroke severity, whereas BHB supplementation blunted these injuries. Mechanistically, it is unveiled that BHB infusion is taken up by monocarboxylic acid transporter 1 (MCT1) specifically expressed in cerebral endothelium and upregulated the expression of tight junction protein ZO-1 by enhancing local β-hydroxybutyrylation of H3K9 at the promoter of TJP1 gene. Conclusively, an adaptive metabolic mechanism is elucidated by which acute lipolysis stimulates FAO-ketogenesis processes to restore BBB integrity after stroke. Ketogenesis functions as an early metabolic responder to restrain stroke progression, providing novel prospectives for clinical translation.

MCT4 knockdown by tumor microenvironment-responsive nanoparticles remodels the cytokine profile and eradicates aggressive breast cancer cells

Breast cancer is a wide-spread threat to the women’s health. The drawbacks of conventional treatments necessitate the development of alternative strategies, where gene therapy has regained hope in achieving an efficient eradication of aggressive tumors. Monocarboxylate transporter 4 (MCT4) plays pivotal roles in the growth and survival of various tumors, which offers a promising target for treatment. In the present study, pH-responsive lipid nanoparticles (LNPs) based on the ionizable lipid,1,2-dioleoyl-3-dimethylammonium propane (DODAP), were designed for the delivery of siRNA targeting MCT4 gene to the breast cancer cells. Following multiple steps of characterization and optimization, the anticancer activities of the LNPs were assessed against an aggressive breast cancer cell line, 4T1, in comparison with a normal cell line, LX-2. The selection of the helper phospholipid to be incorporated into the LNPs had a dramatic impact on their gene delivery performance. The optimized LNPs enabled a powerful MCT4 silencing by ∼90 % at low siRNA concentrations, with a subsequent ∼80 % cytotoxicity to 4T1 cells. Meanwhile, the LNPs demonstrated a 5-fold higher affinity to the breast cancer cells versus the normal cells, in which they had a minimum effect. Moreover, the MCT4 knockdown by the treatment remodeled the cytokine profile in 4T1 cells, as evidenced by 90 % and ∼64 % reduction in the levels of TNF-α and IL-6; respectively. The findings of this study are promising for potential clinical applications. Furthermore, the simple and scalable delivery vector developed herein can serve as a breast cancer-targeting platform for the delivery of other RNA therapeutics.

Enhanced oral and pulmonary delivery of biomacromolecules via amplified transporter targeting

Ligand-modified nanocarriers can promote oral or inhalative administration of macromolecular drugs across the intestinal or pulmonary mucosa. However, enhancing the unidirectional transport of the nanocarriers through “apical uptake→intracellular transport→basolateral exocytosis” route remains a hot topic and challenge in current research. Forskolin is a naturally occurring diterpenoid compound extracted from the roots of C. forskohlii. In our studies, we found that forskolin could increase the transcellular transport of butyrate-modified nanoparticles by 1.67-fold and 1.20-fold in Caco-2 intestinal epithelial cell models and Calu-3 lung epithelial cell models, respectively. Further mechanistic studies revealed that forskolin, on the one hand, promoted the cellular uptake of butyrate-modified nanoparticles by upregulating the expression of monocarboxylic acid transporter-1 (MCT-1) on the apical membrane. On the other hand, forskolin facilitated the binding of MCT-1 to caveolae, thereby mediating butyrate-modified nanoparticles hijacking caveolae to promote the basolateral exocytosis of butyrate-modified nanoparticles. Studies in normal mice model showed that forskolin could promote the transmucosal absorption of butyrate-modified nanoparticles by >2-fold, regardless of oral or inhalative administration. Using semaglutide as the model drug, both oral and inhalation delivery approaches demonstrated significant hypoglycemic effects in type 2 diabetes mice model, in which inhalative administration was more effective than oral administration. This study optimized the strategies aimed at enhancing the transmucosal absorption of ligand-modified nanocarriers in the intestinal or pulmonary mucosa.

Distinct contribution of monocarboxylate transporter 2 to infantile epileptic spasms syndrome

Infantile epileptic spasms syndrome (IESS) is the most common refractory epileptic encephalopathy in early brain development, its pathogenesis remains elusive. In the adult brain, glucose serves as the predominant metabolic fuel. However, ketone bodies and lactate are more important in neural energy metabolism during early development. This has been further provided by the effectiveness of ketogenic diet (KD) therapy in IESS. When the circulatory pool of ketone bodies is increased by KD, the brain utilizes ketone bodies preferentially to meet the high energy demand of neurons which is beneficial to mitigate seizure activity and promote prognosis for children with IESS. Neuronal monocarboxylate transporter 2 (MCT2) is crucial in this process, transporting ketone bodies and lactate to mitochondria for adenosine triphosphate (ATP) generation for cellular energy. The inhibition of MCT2 has been linked to mitochondrial dysfunction and its reduction has been found in adult animal epilepsy models. The mitochondrial energy metabolism disorder is a recognized central pathological aspect of epileptogenesis. Therefore, we hypothesize that neuronal MCT2, an essential gatekeeper of energy metabolism, may play a critical role in the genesis and propagation of spasms in IESS by markedly affecting brain metabolic homeostasis and mitochondrial function. We propose to conduct animal studies and clinical studies to investigate the relationship among MCT2, severity of IESS, susceptibility of IESS, and mitochondrial dysfunction from a metabolic perspective.

Unique features of β-cell metabolism are lost in type 2 diabetes.

Pancreatic β cells play an essential role in the control of systemic glucose homeostasis as they sense blood glucose levels and respond by secreting insulin. Upon stimulating glucose uptake in insulin-sensitive tissues post-prandially, this anabolic hormone restores blood glucose levels to pre-prandial levels. Maintaining physiological glucose levels thus relies on proper β-cell function. To fulfill this highly specialized nutrient sensor role, β cells have evolved a unique genetic program that shapes its distinct cellular metabolism. In this review, the unique genetic and metabolic features of β cells will be outlined, including their alterations in type 2 diabetes (T2D). β cells selectively express a set of genes in a cell type-specific manner; for instance, the glucose activating hexokinase IV enzyme or Glucokinase (GCK), whereas other genes are selectively "disallowed", including lactate dehydrogenase A (LDHA) and monocarboxylate transporter 1 (MCT1). This selective gene program equips β cells with a unique metabolic apparatus to ensure that nutrient metabolism is coupled to appropriate insulin secretion, thereby avoiding hyperglycemia, as well as life-threatening hypoglycemia. Unlike most cell types, β cells exhibit specialized bioenergetic features, including supply-driven rather than demand-driven metabolism and a high basal mitochondrial proton leak respiration. The understanding of these unique genetically programmed metabolic features and their alterations that lead to β-cell dysfunction is crucial for a comprehensive understanding of T2D pathophysiology and the development of innovative therapeutic approaches for T2D patients.

Spatiotemporal expression of thyroid hormone transporter MCT8 and THRA mRNA in human cerebral organoids recapitulating first trimester cortex development

Thyroid hormones (TH) play critical roles during nervous system development and patients carrying coding variants of MCT8 (monocarboxylate transporter 8) or THRA (thyroid hormone receptor alpha) present a spectrum of neurological phenotypes resulting from perturbed local TH action during early brain development. Recently, human cerebral organoids (hCOs) emerged as powerful in vitro tools for disease modelling recapitulating key aspects of early human cortex development. To begin exploring prospects of this model for thyroid research, we performed a detailed characterization of the spatiotemporal expression of MCT8 and THRA in developing hCOs. Immunostaining showed MCT8 membrane expression in neuronal progenitor cell types including early neuroepithelial cells, radial glia cells (RGCs), intermediate progenitors and outer RGCs. In addition, we detected robust MCT8 protein expression in deep layer and upper layer neurons. Spatiotemporal SLC16A2 mRNA expression, detected by fluorescent in situ hybridization (FISH), was highly concordant with MCT8 protein expression across cortical cell layers. FISH detected THRA mRNA expression already in neuroepithelium before the onset of neurogenesis. THRA mRNA expression remained low in the ventricular zone, increased in the subventricular zone whereas strong THRA expression was observed in excitatory neurons. In combination with a robust up-regulation of known T3 response genes following T3 treatment, these observations show that hCOs provide a promising and experimentally tractable model to probe local TH action during human cortical neurogenesis and eventually to model the consequences of impaired TH function for early cortex development.

A multi-hierarchical approach reveals d-serine as a hidden substrate of sodium-coupled monocarboxylate transporters

Transporter research primarily relies on the canonical substrates of well-established transporters. This approach has limitations when studying transporters for the low-abundant micromolecules, such as micronutrients, and may not reveal physiological functions of the transporters. While d-serine, a trace enantiomer of serine in the circulation, was discovered as an emerging biomarker of kidney function, its transport mechanisms in the periphery remain unknown. Here, using a multi-hierarchical approach from body fluids to molecules, combining multi-omics, cell-free synthetic biochemistry, and ex vivo transport analyses, we have identified two types of renal d-serine transport systems. We revealed that the small amino acid transporter ASCT2 serves as a d-serine transporter previously uncharacterized in the kidney and discovered d-serine as a non-canonical substrate of the sodium-coupled monocarboxylate transporters (SMCTs). These two systems are physiologically complementary, but ASCT2 dominates the role in the pathological condition. Our findings not only shed light on renal d-serine transport, but also clarify the importance of non-canonical substrate transport. This study provides a framework for investigating multiple transport systems of various trace micromolecules under physiological conditions and in multifactorial diseases.

The Effect of Different Exercise Modalities on Sertoli-germ Cells Metabolic Interactions in High-fat Diet-induced Obesity Rat Models: Implication on Glucose and Lactate Transport, Igf1, and Igf1R-dependent Pathways.

The study aimed to uncover a unique aspect of obesity-related metabolic disorders in the testicles induced by a high-fat diet (HFD) and explored the potential mitigating effects of exercise modalities on male fertility. Thirty mature male Wistar rats were randomly assigned to control, HFD-sole, moderate-intensity exercise with HFD (HFD+MICT), high-intensity continuous exercise with HFD (HFD+HICT), and high-intensity interval exercise with HFD (HFD+HIIT) groups (n=6/group). Intracytoplasmic carbohydrate (ICC) storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and testicular lactate and lactate dehydrogenase (LDH) levels were assessed. ICC storage significantly decreased in HFD-sole rats, along with decreased mRNA and protein levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R. The HFD-sole group exhibited a notable reduction in testicular lactate and LDH levels (p<0.05). Conversely, exercise, particularly HIIT, upregulated ICC storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and enhanced testicular lactate and LDH levels. These results confirm that exercise, especially HIIT, has the potential to mitigate the adverse effects of HFD-induced obesity on testicular metabolism and male fertility. The upregulation of metabolite transporters, LDH, lactate levels, Igf1, and Igf1R expression may contribute to maintaining metabolic interactions and improving the glucose/lactate conversion process. These findings underscore the potential benefits of exercise in preventing and managing obesity-related male fertility issues.

A prognostic risk model based on lactate metabolism and transport-related lncRNAs for gastric adenocarcinoma

Background Increased lactate levels and metastasis in tumours are strongly associated with dismal outcomes. But prognostic value of lactate metabolism and transport-related lncRNAs in gastric adenocarcinoma (GA) patients remains unaddressed. Methods Gene expression data of GA were provided by The Cancer Genome Atlas. Lactate metabolism and transport-related gene data were accessed from GSEA. LncRNAs related to lactate metabolism and transport were identified by correlation analysis. A prognostic model was built by regression analysis. Validity of prognostic model was confirmed through survival analysis and receiver operating characteristic (ROC) curve. Immunity of each risk group was evaluated by immune correlation analysis .LncRNA-mRNA network was built by correlation analysis using Cytoscape software. Results A 12-gene prognostic model based on lactate metabolism and transport-related lncRNAs was built in GA. Median riskscore was utilized to classify GA samples into high- and low-risk groups. Survival analysis and ROC curves demonstrated validity of prognostic model. Most immune checkpoint molecules and TIDE scores were lower in the low-risk group. LINC01303 and LINC01545 may be the key prognostic factors in patients with GA. Conclusion This study successfully built a prognostic model of lactate metabolism and transport-related lncRNAs in GA. The findings guide prognostic management of GA patients.

Fasting upregulates the monocarboxylate transporter MCT1 at the rat blood-brain barrier through PPAR δ activation

BackgroundThe blood-brain barrier (BBB) is pivotal for the maintenance of brain homeostasis and it strictly regulates the cerebral transport of a wide range of endogenous compounds and drugs. While fasting is increasingly recognized as a potential therapeutic intervention in neurology and psychiatry, its impact upon the BBB has not been studied. This study was designed to assess the global impact of fasting upon the repertoire of BBB transporters.MethodsWe used a combination of in vivo and in vitro experiments to assess the response of the brain endothelium in male rats that were fed ad libitum or fasted for one to three days. Brain endothelial cells were acutely purified and transcriptionaly profiled using RNA-Seq. Isolated brain microvessels were used to assess the protein expression of selected BBB transporters through western blot. The molecular mechanisms involved in the adaptation to fasting were investigated in primary cultured rat brain endothelial cells. MCT1 activity was probed by in situ brain perfusion.ResultsFasting did not change the expression of the main drug efflux ATP-binding cassette transporters or P-glycoprotein activity at the BBB but modulated a restrictive set of solute carrier transporters. These included the ketone bodies transporter MCT1, which is pivotal for the brain adaptation to fasting. Our findings in vivo suggested that PPAR δ, a major lipid sensor, was selectively activated in brain endothelial cells in response to fasting. This was confirmed in vitro where pharmacological agonists and free fatty acids selectively activated PPAR δ, resulting in the upregulation of MCT1 expression. Moreover, dosing rats with a specific PPAR δ antagonist blocked the upregulation of MCT1 expression and activity induced by fasting.ConclusionsAltogether, our study shows that fasting affects a selected set of BBB transporters which does not include the main drug efflux transporters. Moreover, we describe a previously unknown selective adaptive response of the brain vasculature to fasting which involves PPAR δ and is responsible for the up-regulation of MCT1 expression and activity. Our study opens new perspectives for the metabolic manipulation of the BBB in the healthy or diseased brain.

Abstract LB026: Exploring MCT4 inhibitor Ful-23 and cytarabine synergy in acute myeloid leukemia therapeutics

Abstract In the ongoing pursuit of addressing the formidable challenge presented by Acute Myeloid Leukemia (AML) treatment, this comprehensive study delves into the intricate antileukemic effects of Ful-23, our newly developed Monocarboxylate Transporter 4 (MCT4) inhibitor. Positioned as a promising candidate, Ful-23's unique mechanisms and potential synergies with established chemotherapeutic agents, such as Cytarabine, are elucidated in this research. Intracellular alkalinization stands as a crucial factor contributing to the evasion of chemotherapy by cancer cells. It serves as the primary determinant for the heightened resistance exhibited by cancer cells against chemotherapy interventions. The investigation reveals the multifaceted impact of Ful-23 on AML cells, showcasing its capacity to induce intracellular lactate accumulation and acidification. These metabolic alterations correlate with a substantial inhibition of proliferation, as evidenced by an IC50 of approximately 0.55 μM, and a marked induction of apoptosis, particularly notable in the MV411 AML cell line. These findings underscore Ful-23's potential as a potent antileukemic agent with distinct cellular effects. A collaborative approach involves the combination of low concentrations of Ful-23 (0.312 μM) with Cytarabine (0.312 μM), revealing a significant enhancement in cytarabine-induced proliferation inhibition and apoptosis when Ful-23 is introduced concurrently. Importantly, the translational impact of these findings extends to a zebrafish model, utilizing both MV411 cells and transplanted primary AML patient-derived bone marrow cells. In the zebrafish AML model, the combination treatment of Ful-23 and Cytarabine demonstrates a significant enhancement in their respective antitumor effects compared to monotherapy, indicating a pronounced synergistic effect. This additional validation strengthens the clinical relevance of the observed synergistic antileukemic interactions between Ful-23 and Cytarabine. Essentially, this investigation advances our understanding of AML treatment dynamics, emphasizing the crucial role of MCT4 inhibition and elucidating the mechanism by which it leads to intracellular acidification in synergistic therapeutic approaches for this intricate and formidable disease. Citation Format: Yong Wu, Ke Wu, Jay Vadgama. Exploring MCT4 inhibitor Ful-23 and cytarabine synergy in acute myeloid leukemia therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB026.

Monocarboxylate Transporters 1 and 2 Are Responsible for L-Lactate Uptake in Differentiated Human Neuroblastoma SH-SY5Y Cells.

L-Lactate transport via monocarboxylate transporters (MCTs) in the central nervous system, represented by the astrocyte-neuron lactate shuttle (ANLS), is crucial for the maintenance of brain functions, including memory formation. Previously, we have reported that MCT1 contributes to L-lactate transport in normal human astrocytes. Therefore, in this study, we aimed to identify transporters that contribute to L-lactate transport in human neurons. SH-SY5Y cells, which are used as a model for human neurons, were differentiated using all-trans-retinoic acid. L-Lactate uptake was measured using radiolabeled L-lactate, and the expression of MCT proteins was confirmed Western blotting. L-Lactate transport was pH-dependent and saturated at high concentrations. Kinetic analysis suggested that L-lactate uptake was biphasic. Furthermore, MCT1, 2 selective inhibitors inhibited L-lactate transport. In addition, the expression of MCT1 and 2 proteins, but not MCT4, was confirmed. In this study, we demonstrated that MCT1 and 2 are major contributors to L-lactate transport in differentiated human neuroblastoma SH-SY5Y cells from the viewpoint of kinetic analysis. These results lead to a better understanding of ANLS in humans, and further exploration of the factors that can promote MCT1 and 2 functions is required.

Neuroprotective role of lactate in a human in vitro model of the ischemic penumbra

In patients suffering from cerebral ischemic stroke, there is an urgent need for treatments to protect stressed yet viable brain cells. Recently, treatment strategies that induce neuronal activity have been shown to be neuroprotective. Here, we hypothesized that neuronal activation might maintain or trigger the astrocyte-to-neuron lactate shuttle (ANLS), whereby lactate is released from astrocytes to support the energy requirements of ATP-starved hypoxic neurons, and this leads to the observed neuroprotection. We tested this by using a human cell based in vitro model of the ischemic penumbra and investigating whether lactate might be neuroprotective in this setting. We found that lactate transporters are involved in the neuroprotective effect mediated by neuronal activation. Furthermore, we showed that lactate exogenously administered before hypoxia correlated with neuroprotection in our cellular model. In addition, stimulation of astrocyte with consequent endogenous production of lactate resulted in neuroprotection. To conclude, here we presented evidence that lactate transport into neurons contributes to neuroprotection during hypoxia providing a potential basis for therapeutic approaches in ischemic stroke.

Lactate transporter MCT1 in hepatic stellate cells promotes fibrotic collagen expression in nonalcoholic steatohepatitis.

Circulating lactate is a fuel source for liver metabolism but may exacerbate metabolic diseases such as nonalcoholic steatohepatitis (NASH). Indeed, haploinsufficiency of lactate transporter monocarboxylate transporter 1 (MCT1) in mice reportedly promotes resistance to hepatic steatosis and inflammation. Here, we used adeno-associated virus (AAV) vectors to deliver thyroxin binding globulin (TBG)-Cre or lecithin-retinol acyltransferase (Lrat)-Cre to MCT1fl/fl mice on a choline-deficient, high-fat NASH diet to deplete hepatocyte or stellate cell MCT1, respectively. Stellate cell MCT1KO (AAV-Lrat-Cre) attenuated liver type 1 collagen protein expression and caused a downward trend in trichrome staining. MCT1 depletion in cultured human LX2 stellate cells also diminished collagen 1 protein expression. Tetra-ethylenglycol-cholesterol (Chol)-conjugated siRNAs, which enter all hepatic cell types, and hepatocyte-selective tri-N-acetyl galactosamine (GN)-conjugated siRNAs were then used to evaluate MCT1 function in a genetically obese NASH mouse model. MCT1 silencing by Chol-siRNA decreased liver collagen 1 levels, while hepatocyte-selective MCT1 depletion by AAV-TBG-Cre or by GN-siRNA unexpectedly increased collagen 1 and total fibrosis without effect on triglyceride accumulation. These findings demonstrate that stellate cell lactate transporter MCT1 significantly contributes to liver fibrosis through increased collagen 1 protein expression in vitro and in vivo, while hepatocyte MCT1 appears not to be an attractive therapeutic target for NASH.

Lactate transporter MCT1 in hepatic stellate cells promotes fibrotic collagen expression in nonalcoholic steatohepatitis

Circulating lactate is a fuel source for liver metabolism but may exacerbate metabolic diseases such as nonalcoholic steatohepatitis (NASH). Indeed, haploinsufficiency of lactate transporter monocarboxylate transporter 1 (MCT1) in mice reportedly promotes resistance to hepatic steatosis and inflammation. Here, we used adeno-associated virus (AAV) vectors to deliver thyroxin binding globulin (TBG)-Cre or lecithin-retinol acyltransferase (Lrat)-Cre to MCT1fl/fl mice on a choline-deficient, high-fat NASH diet to deplete hepatocyte or stellate cell MCT1, respectively. Stellate cell MCT1KO (AAV-Lrat-Cre) attenuated liver type 1 collagen protein expression and caused a downward trend in trichrome staining. MCT1 depletion in cultured human LX2 stellate cells also diminished collagen 1 protein expression. Tetra-ethylenglycol-cholesterol (Chol)-conjugated siRNAs, which enter all hepatic cell types, and hepatocyte-selective tri-N-acetyl galactosamine (GN)-conjugated siRNAs were then used to evaluate MCT1 function in a genetically obese NASH mouse model. MCT1 silencing by Chol-siRNA decreased liver collagen 1 levels, while hepatocyte-selective MCT1 depletion by AAV-TBG-Cre or by GN-siRNA unexpectedly increased collagen 1 and total fibrosis without effect on triglyceride accumulation. These findings demonstrate that stellate cell lactate transporter MCT1 significantly contributes to liver fibrosis through increased collagen 1 protein expression in vitro and in vivo, while hepatocyte MCT1 appears not to be an attractive therapeutic target for NASH.

Clinical relevance of glycosylation in triple negative breast cancer: a review.

Glycosylation alterations in TNBC have significant implications for tumor behavior, diagnosis, prognosis, and therapeutic strategies. Dysregulated glycosylation affects cell adhesion, signaling, immune recognition, and response to therapy in TNBC. Different types of glycosylation, including N-linked glycosylation, O-linked glycosylation, glycosphingolipid glycosylation, mucin-type glycosylation, and sialylation, play distinct roles in TNBC. The "barcoding" method based on glycosylation sites of the membrane type mannose receptor (MR) shows promise in accurately distinguishing breast cancer subtypes, including TNBC. Alpha-L-fucosidase 1 (FUCA1) and Monocarboxylate transporter 4 (MCT4) have been identified as potential diagnostic and prognostic markers for TNBC. The glycosylation status of PD-L1 impacts the response to immune checkpoint blockade therapy in TNBC. Inhibiting fucosylation of B7H3 enhances immune responses and improves anti-tumor effects. Targeting glycosylated B7H4 and modulating estrogen metabolism through glycosylation-related mechanisms are potential therapeutic strategies for TNBC. Understanding the role of glycosylation in TNBC provides insights into disease mechanisms, diagnosis, and potential therapeutic targets. Further research in this field may lead to personalized treatment approaches and improved outcomes for TNBC patients.