Lactate Utilization Research Articles

A reproducible extended ex-vivo normothermic machine liver perfusion protocol utilising improved nutrition and targeted vascular flows

BackgroundNormothermic machine perfusion of donor livers has become standard practice in the field of transplantation, allowing the assessment of organs and safe extension of preservation times. Alongside its clinical uses, there has been expanding interest in extended normothermic machine perfusion (eNMP) of livers as a potential vehicle for medical research. Reproducible extended normothermic machine perfusion has remained elusive due to its increased complexity and monitoring requirements. We set out to develop a reproducible protocol for the extended normothermic machine perfusion of whole human livers.MethodsHuman livers declined for transplantation were perfused using a blood-based perfusate at 36 °C using the Liver Assist device (XVIVO, Sweden), with continuous veno-venous haemofiltration in-parallel. We developed the protocol in a stepwise fashion.ResultsPerfusion techniques utilised included: targeted physiological vascular flows, phosphate replacement (to prevent hypophosphataemia), N-acetylcysteine (to prevent methaemoglobin accumulation), and the utilisation of sodium lactate as both a nutritional source and real-time measure of hepatocyte function. All five human livers perfused with the developed protocol showed preserved function with a median perfusion time of 168 h (range 120–184 h), with preserved viability throughout.ConclusionsLivers can be reproducibly perfused in excess of 120 (range 121–184) hours with evidence of preserved hepatocyte and cholangiocyte function.

Thermodynamics-driven metabolic and microbial preference for lactate methanization at different operational temperatures

Lactate-dominant organic acids released from acidified feedstocks inhibit anaerobic digestion processes, which can result in decreased biomethane (CH4) yield or even complete process failure. Herein, this study focus on exploring the effects of temperature (35 °C, 38 °C, 41 °C, 44 °C, 47 °C, 50 °C, and 55 °C) on the thermodynamics of microbial communities to assess the thermodynamics or microbial flora in driving the concurrent bioreactions involved in organic acid degradation. The findings revealed a prevalence of species such as Syntrophaceticus schinkii, DTU014, and Methanosarcina at 38 °C-44 °C. These species are known for their abilities in propionate and butyrate degradations, acetate oxidation, and methanation, respectively. Conversely, at thermophilic temperatures (47 °C, 50 °C, and 55 °C), this study observed higher abundance of thermophilic microorganisms like Defluviitoga and Methanoculleus, although these organisms are adapted to higher temperatures, their lactate utilization and methane production were less efficient than mesophilic species. Despite higher ΔG values for lactate, propionate, and butyrate degradation at 38 °C–44 °C compared with thermophilic temperatures, the relative abundance of functional enzymes (specifically, propionate and butyrate degrading enzymes) was found to be marginally higher than 47 °C–55 °C. As a result, 41 °C–44 °C induced remarkable thermodynamic effects that not only facilitated organic acid degradation but also promoted subsequent methanation, indicating the suitability of these temperatures for the methanation of biowaste acidified by lactate. Overall, this study provides insight into the temperature-dependent response of organic acid degradation, specifically focusing on the mechanisms involved in overcoming energy barriers, shaping the microbial flora, and ultimately improving the efficiency and stability of anaerobic digestion, especially for lactate-acidified feedstock.

LDHB-deficient brain exhibits resistance to ischemic neuronal cell death due to increased vasodilation

Ischemic stroke triggers a cascade of metabolic and inflammatory events leading to neuronal death, particularly in the hippocampus. Here, we investigate the role of lactate metabolism in ischemic resistance using LDHB-deficient mice, which exhibit impaired lactate utilization. Contrary to expectations of severe neuronal damage due to metabolic defects, LDHB-deficient mice displayed significantly increased neuronal survival following ischemic insult. Magnetic resonance spectroscopy revealed elevated lactate levels in LDHB-deficient brains, which correlated with enhanced vasodilation of the posterior communicating artery (PComA) and increased extracellular PGE2 levels. These findings suggest that elevated lactate inhibits PGE2 reabsorption, promoting vasodilation and neuronal protection. Our results highlight lactate's potential role in neuroprotection and its therapeutic promise for ischemic stroke.

Defining metabolic flexibility in hair follicle stem cell induced squamous cell carcinoma.

We previously showed that inhibition of glycolysis in cutaneous squamous cell carcinoma (SCC)-initiating cells had no effect on tumorigenesis, despite the perceived requirement of the Warburg effect, which was thought to drive carcinogenesis. Instead, these SCCs were metabolically flexible and sustained growth through glutaminolysis, another metabolic process frequently implicated to fuel tumorigenesis in various cancers. Here, we focused on glutaminolysis and genetically blocked this process through glutaminase (GLS) deletion in SCC cells of origin. Genetic deletion of GLS had little effect on tumorigenesis due to the up-regulated lactate consumption and utilization for the TCA cycle, providing further evidence of metabolic flexibility. We went on to show that posttranscriptional regulation of nutrient transporters appears to mediate metabolic flexibility in this SCC model. To define the limits of this flexibility, we genetically blocked both glycolysis and glutaminolysis simultaneously and found the abrogation of both of these carbon utilization pathways was enough to prevent both papilloma and frank carcinoma.

A novel PDHK inhibitor restored cognitive dysfunction and limited neurodegeneration without affecting amyloid pathology in 5xFAD mouse, a model of Alzheimer’s disease

BackgroundAlzheimer’s disease (AD) is the most common form of dementia. Although drugs focusing on reducing amyloid β slow progression, they fail to improve cognitive function. Deficits in glucose metabolism are reflected in FDG-PET and parallel the neurodegeneration and synaptic marker loss closely preceding cognitive decline, but the role of metabolic deficits as a cause or consequence of neurodegeneration is unclear. Pyruvate dehydrogenase (PDH) is lost in AD and an important enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle by converting pyruvate into acetyl-CoA. It is negatively regulated by pyruvate dehydrogenase kinase (PDHK) through phosphorylation.MethodsIn the present study, we assessed the in vitro/ in vivo pharmacological profile of the novel PDHK inhibitor that we discovered, Compound A. We also assessed the effects of Compound A on AD-related phenotypes including neuron loss and cognitive impairment using 5xFAD model mice.ResultsCompound A inhibited human PDHK1, 2 and 3 but had no inhibitory activity on PDHK4. In primary neurons, Compound A enhanced pyruvate and lactate utilization, but did not change glucose levels. In contrast, in primary astrocytes, Compound A enhanced pyruvate and glucose utilization and enhanced lactate production. In an efficacy study using 5xFAD mice, Compound A ameliorated the cognitive dysfunction in the novel object recognition test and Morris water maze. Moreover, Compound A prevented neuron loss in the hippocampus and cerebral cortex of 5xFAD without affecting amyloid β deposits.ConclusionsThese results suggest ameliorating metabolic deficits by activating PDH by Compound A can limit neurodegeneration and is a promising therapeutic strategy for treating AD.

Origin of biogeographically distinct ecotypes during laboratory evolution

Resource partitioning is central to the incredible productivity of microbial communities, including gigatons in annual methane emissions through syntrophic interactions. Previous work revealed how a sulfate reducer (Desulfovibrio vulgaris, Dv) and a methanogen (Methanococcus maripaludis, Mm) underwent evolutionary diversification in a planktonic context, improving stability, cooperativity, and productivity within 300–1000 generations. Here, we show that mutations in just 15 Dv and 7 Mm genes within a minimal assemblage of this evolved community gave rise to co-existing ecotypes that were spatially enriched within a few days of culturing in a fluidized bed reactor. The spatially segregated communities partitioned resources in the simulated subsurface environment, with greater lactate utilization by attached Dv but partial utilization of resulting H2 by low affinity hydrogenases of Mm in the same phase. The unutilized H2 was scavenged by high affinity hydrogenases of planktonic Mm, producing copious amounts of methane. Our findings show how a few mutations can drive resource partitioning amongst niche-differentiated ecotypes, whose interplay synergistically improves productivity of the entire mutualistic community.

Evaluating Lactate and D-Dimer as Mortality Predictors of Paediatric Multiple Organ Dysfunction Syndrome: A Prospective Study in a Low-Middle Income Country.

Multiple Organ Dysfunction Syndrome (MODS) is a complex medical condition characterised by dysfunction across multiple organs. With limited information available on mortality prediction in the paediatric population, particularly in low-middle income countries, this study evaluates the mortality predicting capabilities of lactate, D-dimer, and their combination. This prospective study involved paediatric patients admitted to the paediatric intensive care unit (PICU) of the largest central children's hospital in the Mekong Delta region, Vietnam, from 2019 to 2021. The discriminative ability and calibration of both individual and combined tests were assessed using the receiver operating characteristic (ROC) curves and the Hosmer-Lemeshow goodness-of-fit test. Among the patients studied, 63.1% did not survive. Lactate and D-dimer concentrations were significantly higher in the non-survivor group (P < 0.001). The area under the curve (AUC) values for lactate, D-dimer and the combined lactate-D-dimer test were 0.742, 0.775 and 0.804, respectively, with the combination showing the highest AUC value, though without statistical significance. Specific thresholds for lactate, D-dimer and the combination yielded sensitivities of 75.5%, 71.7%, and 66.0%, respectively. All three tests showed no statistically significant differences between observed and predicted mortality in the Hosmer-Lemeshow test (all P-values > 0.05). Lactate and D-dimer levels showed a significant association with mortality, along with good discrimination and calibration abilities. These results highlight the utility of lactate and D-dimer as effective predictors in paediatric MODS, particularly in resource-limited settings, and their role in improving patient outcomes.

Determining lactate concentrations in Korean indigenous calves and evaluating its role as a predictor for acidemia in calf diarrhea

BackgroundCalf diarrhea leads to high mortality rates and decreases in growth and productivity, causing negative effects on the livestock industry. Lactate is closely associated with metabolic acidosis in diarrheic calves. However, there have been no reports on lactate concentrations in Korean indigenous (Hanwoo) calves, especially those with diarrhea. This study aimed to determine the reference range of L-lactate and D-lactate concentrations in Hanwoo calves and to better understand the utility of lactate as predictive factors for acidemia in diarrheic calves.ResultsL-lactate and D-lactate concentrations were measured in healthy (n = 44) and diarrheic (n = 93) calves, and blood gas analysis was performed on diarrheic calves. The reference range in healthy calves was 0.2–2.25 mmol/L for L-lactate and 0.42–1.38 mmol/L for D-lactate. Diarrheic calves had higher concentrations of L-lactate and D-lactate than healthy calves. In diarrheic calves, L-lactate and D-lactate each had weak negative correlation with pH (r = − 0.31 and r = − 0.35). In diarrheic calves with hyper-L-lactatemia, the combined concentrations of L-lactate and D-lactate had moderate correlation with pH (r = − 0.51) and anion gap (r = 0.55). Receiver operating characteristic analysis showed D-lactate had fair predictive performance (AUC = 0.74) for severe acidemia, with an optimal cut-off value of > 1.43 mmol/L. The combined concentrations of L-lactate and D-lactate showed fair predictive performance for predicting acidemia (AUC = 0.74) and severe acidemia (AUC = 0.72), with cut-off values of > 6.05 mmol/L and > 5.95 mmol/L.ConclusionsThe determined reference ranges for L-lactate and D-lactate in Hanwoo calves enable the identification of hyper-L-lactatemia and hyper-D-lactatemia. Diarrheic calves exhibited increased lactate concentrations correlated with acid-base parameters. While the concentrations of L-lactate and D-lactate have limitations as single diagnostic biomarkers for predicting acidemia or severe acidemia, their measurement remains important, and L-lactate has the advantage of being measurable at the point-of-care. Assessing lactate concentrations should be considered by clinicians, especially when used alongside other clinical indicators and diagnostic tests. This approach can improve calf diarrhea management, contributing positively to animal welfare and providing economic benefits to farms.

Ex-Vivo 13C NMR Spectroscopy of Rodent Brain: TNF Restricts Neuronal Utilization of Astrocyte-Derived Metabolites.

Tumor necrosis factor (TNF) has well-established roles in neuroinflammatory disorders, but the effect of TNF on the biochemistry of brain cells remains poorly understood. Here, we microinjected TNF into the brain to study its impact on glial and neuronal metabolism (glycolysis, pentose phosphate pathway, citric acid cycle, pyruvate dehydrogenase, and pyruvate carboxylase pathways) using 13C NMR spectroscopy on brain extracts following intravenous [1,2-13C]-glucose (to probe glia and neuron metabolism), [2-13C]-acetate (probing astrocyte-specific metabolites), or [3-13C]-lactate. An increase in [4,5-13C]-glutamine and [2,3-13C]-lactate coupled with a decrease in [4,5-13C]-glutamate was observed in the [1,2-13C]-glucose-infused animals treated with TNF. As glutamine is produced from glutamate by astrocyte-specific glutamine synthetase the increase in [4,5-13C]-glutamine reflects increased production of glutamine by astrocytes. This was confirmed by infusion with astrocyte substrate [2-13C]-acetate. As lactate is metabolized in the brain to produce glutamate, the simultaneous increase in [2,3-13C]-lactate and decrease in [4,5-13C]-glutamate suggests decreased lactate utilization, which was confirmed using [3-13C]-lactate as a metabolic precursor. These results suggest that TNF rearranges the metabolic network, disrupting the energy supply chain perturbing the glutamine-glutamate shuttle between astrocytes and the neurons. These insights pave the way for developing astrocyte-targeted therapeutic strategies aimed at modulating effects of TNF to restore metabolic homeostasis in neuroinflammatory disorders.

MCT1-dependent lactate recycling is a metabolic vulnerability in colorectal cancer cells upon acquired resistance to anti-EGFR targeted therapy

Despite the implementation of personalized medicine, patients with metastatic CRC (mCRC) still have a dismal overall survival due to the frequent occurrence of acquired resistance mechanisms thereby leading to clinical relapse. Understanding molecular mechanisms that support acquired resistance to anti-EGFR targeted therapy in mCRC is therefore clinically relevant and key to improving patient outcomes. Here, we observe distinct metabolic changes between cetuximab-resistant CRC cell populations, with in particular an increased glycolytic activity in KRAS-mutant cetuximab-resistant CRC cells (LIM1215 and OXCO2) but not in KRAS-amplified resistant DiFi cells. We show that cetuximab-resistant LIM1215 and OXCO2 cells have the capacity to recycle glycolysis-derived lactate to sustain their growth capacity. This is associated with an upregulation of the lactate importer MCT1 at both transcript and protein levels. Pharmacological inhibition of MCT1, with AR-C155858, reduces the uptake and oxidation of lactate and impairs growth capacity in cetuximab-resistant LIM1215 cells both in vitro and in vivo. This study identifies MCT1-dependent lactate utilization as a clinically actionable, metabolic vulnerability to overcome KRAS-mutant-mediated acquired resistance to anti-EGFR therapy in CRC.

Thermophilic fermentation of sugarcane vinasse: Process flexibility explained through characterizing microbial community and predicting metabolic functions

This study unravels some of the complex microbial interactions established in the fermentation of sugarcane vinasse. The microbial communities of four thermophilic (55 °C) fixed-bed vinasse-fed reactors were analyzed by 16S rRNA gene amplicon sequencing and the marker gene data were aligned with reference genomes to predict metabolic functions of the microorganisms. The production (by Lactobacillus) and utilization (mainly by Thermoanaerobacterium and Caproiciproducens) of lactate explain the primary pathways associated with substrate fermentation towards biohydrogen, whilst only a single genus (Desulfotomaculum) and very low abundances of the enzymes involved in sulfate reduction were found. Although the abundant microbes in the inocula failed to grow during the continuous operation in all reactors, these fermentative consortia behave like microbial pantries containing bacteria that will grow according to the operating conditions, shaping lactate-accumulating (pH < 5.0) or lactate-consuming (pH > 5.0) and eventually sulfate-reducing (pH > 6.0) microbial communities in vinasse thermophilic fermentation.

Blocking the utilization of carbon sources via two pathways to induce tumor starvation for cancer treatment

Glucose oxidase (GOx) is often used to starvation therapy. However, only consuming glucose cannot completely block the energy metabolism of tumor cells. Lactate can support tumor cell survival in the absence of glucose. Here, we constructed a nanoplatform (Met@HMnO2-GOx/HA) that can deplete glucose while inhibiting the compensatory use of lactate by cells to enhance the effect of tumor starvation therapy. GOx can catalyze glucose into gluconic acid and H2O2, and then HMnO2 catalyzes H2O2 into O2 to compensate for the oxygen consumed by GOx, allowing the reaction to proceed sustainably. Furthermore, metformin (Met) can inhibit the conversion of lactate to pyruvate in a redox-dependent manner and reduce the utilization of lactate by tumor cells. Met@HMnO2-GOx/HA nanoparticles maximize the efficacy of tumor starvation therapy by simultaneously inhibiting cellular utilization of two carbon sources. Therefore, this platform is expected to provide new strategies for tumor treatment.

Modelling and assessment of glucose-lactate kinetics in youth withoverweight, obesityand metabolic dysfunction-associated steatotic liver disease: A pilot study.

In this study, we investigated glucose and lactate kinetics during a 75 g oral glucose tolerance test (OGTT) in 23 overweight and obese adolescents and assessed putative differences among participants with and without metabolic dysfunction-associated steatotic liver disease (MASLD). We enrolled 23 young people (six girls) with obesity [body mass index 33 (29-37)]. Glucose-lactate kinetics parameters (disposal glucose insulin sensitivity, SID; fraction of glucose converted into lactate, fr; fractional lactate clearance rate, kL) and lactate production rate (LPR) were estimated using the oral glucose-lactate minimal model. MASLD presence was assessed using the proton density fat fraction. We analysed glucose, lactate and LPR time to peak, peak values and area under the curve and evaluated differences using the Wilcoxon test. MASLD and no-MASLD participants were compared using the Mann-Whitney test. Correlations between parameters were assessed using the Spearman correlation coefficient (ρ). We also tested the performance of two (4 or 3 h OGTT) protocols in estimating oral glucose-lactate minimal model and LPR parameters. Glucose peaks 30 min earlier than lactate (p = .0019). This pattern was present in the no-MASLD group (p < .001). LPR peaks 30 min later in the MASLD group (p = .02). LPR and kL were higher in MASLD, suggesting higher glycolysis and lactate utilization. SID and fr correlate significantly (ρ = -0.55, p = .008). SID and fr were also correlated with the body mass index, (ρ = -0.45, p = .04; and ρ = 0.45; p = .03). The protocol duration did not influence the estimates of the parameters. Youth with MASLD showed a delayed glucose metabolism, possibly because of greater utilization of the underlying substrates. A 3-h OGTT may be used to assess lactate metabolism effectively.

Effect of lactate supplementation to skeletal muscle cells on fiber type transition and cellular bioenergetics

It is well-known that lactate (LAC) is the primary cellular end-product of glycolysis. However, during intense exercise and transient hypoxic conditions, the intracellular LAC levels are significantly elevated. Recently, our in vitro biochemical and biophysical studies have revealed that LAC avidly binds to oxy-myoglobin (oxy-Mb) in acidic conditions and rapidly releases oxygen (O2). Based on these results, we hypothesize that LAC plays a significant role in tissue O2 management combating hypoxic conditions in high demanding exercising tissues, such as Mb rich skeletal muscles type I oxidative fibers. Here, we have investigated three types of mouse C2C12 cell line models, i.e. Wild-type (WT) cells, Mb knock-out (MbKO) cells, and Empty vector (EV) cells. 5-day old differentiated C2C12 cells were supplemented with varying concentrations (3 mM, 5 mM and 8 mM) of sodium lactate added to the DMEM growth medium. Thereafter, cells were incubated in temperature regulated CO2 incubator for varying time periods (3 h, 6 h, and 24 h) to evaluate the early and prolonged effect on tissue fiber type transition and cellular bioenergetics. Metabolic assays such as hexokinase activity, LAC dehydrogenase (LDH) activity, and glucose uptake were performed using the intracellular cell lysate whereas extracellular LAC levels were measured using LAC assay kit. Seahorse experiments were conducted to measure the cellular glycolytic and mitochondrial ATP production rates. Our findings revealed that, there was no significant difference in myotube width in C2C12 cells either with or without LAC supplementation across all the test conditions. Intriguingly, at lower LAC supplementation (1.8 mM) conditions, the extracellular LAC levels were found to be significantly increased in WT cells compared to MbKO cells. However, at mimicking hyperlactatemia (5 mM LAC) and lactic acidosis (8 mM LAC) conditions, distinct extracellular LAC levels were recorded with WT and MbKO cells. Our results clearly suggests that Mb containing cells effciently utilize LAC for cellular bioenergetics and other biochemical processes. Similarly, in response to increasing LAC supplementation levels, LDH activity was also found to higher in WT cells compared to MbKO cells. Furthermore, glucose uptake in MbKO cells was significantly decreased. Finally, significantly lower rates of glycolytic ATP production was observed when compared to mitochondrial ATP production in WT cells with similar overall ATP production rates in all treatment conditions and incubation periods. However, marginal decrease in both glycolytic and mitochondrial ATP production rates were observed in MbKO cells. Overall, this study clearly demonstrated that external supplementation of LAC to C2C12 cells had no significant effect on fiber type transition but reveals that Mb plays a significant role in LAC utilization. USDA-ARS project 6026-51000-012-06S, Sturgis Foundation Pilot Grant G1-54750-01 and ACRI-ABI Investigator Initiated Grant Award GR037175-4450S ABI. 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.

Urinary metabolites indicative of the administration of hypoxen monitored by liquid chromatography-high resolution/accurate mass tandem mass spectrometry.

Hypoxen, a poly(dihydroxyphenylene) thiosulfonate-based drug, has been investigated concerning its effect on mitochondrial respiration and the utilization of lactate, especially in the context of strenuous exercise. Since 2023, patterns of use regarding hypoxen amongst the athletic population are monitored by the World Anti-Doping Agency (WADA) and its accredited anti-doping laboratories, necessitating information on suitable urinary markers indicative of the administration of hypoxen. In this exploratory study, urine samples collected post-administration of 1.5 and 2.0g of hypoxen were analyzed by means of liquid chromatography-high resolution/high mass accuracy (tandem) mass spectrometry, which allowed for the identification of eight analytes that were plausibly attributable to metabolites of hypoxen. The identified species were assigned to the unconjugated species of S-(2,2',5,5'-tetrahydroxy-[1,1'-biphenyl]-3-yl) sulfurothioate and its glucuronide and additional tentatively identified analytes comprising a mercaptobenzene core structure. Including the identified markers into routine doping control analytical procedures enabled the detection of hypoxen use in athletes' doping control samples, thus contributing relevant information to WADA's monitoring program.

Whole genome sequencing analysis of Komagataeibacter nataicola reveals its potential in food waste valorisation for cellulose production.

Komagataeibacter nataicola (K. nataicola) is a gram-negative acetic acid bacterium that produces natural bacterial cellulose (BC) as a fermentation product under acidic conditions. The goal of this work was to study the complete genome of K. nataicola and gain insight into the functional genes in K. nataicola that are responsible for BC synthesis in acidic environments. The pure culture of K. nataicola was obtained from yeast-glucose-calcium carbonate (YGC) agar, followed by genomic DNA extraction, and subjected to whole genome sequencing on a Nanopore flongle flow cell. The genome of K. nataicola consists of a 3,767,936bp chromosome with six contigs and 4,557 protein coding sequences. The maximum likelihood phylogenetic tree and average nucleotide identity analysis confirmed that the bacterial isolate was K. nataicola. The gene annotation via RAST server discovered the presence of cellulose synthase, along with three genes associated with lactate utilization and eight genes involved in lactate fermentation that could potentially contribute to the increase in acid concentration during BC synthesis. A more comprehensive genome study of K. nataicola may shed light into biological pathway in BC productivity as well as benefit the analysis of metabolites generated and understanding of biological and chemical interactions in BC production later.

Biological significance and clinical utility of lactate in sepsis.

Sepsis is a global health problem; progression to septic shock is associated with a marked increase in morbidity and mortality. In this setting, increased plasma lactate levels demonstrated to be an indicator of severity and a predictor of mortality, and are usually interpreted almost exclusively as a marker of low tissue perfusion. However, a recent paradigm shift has occurred in the exegesis of lactate metabolism and its biological properties. Indeed, metabolic adaptation to stress, even with an adequate oxygen supply, may account for high circulating lactate levels. Likewise, other pathophysiological consequences of sepsis, such as mitochondrial dysfunction, are associated with the development of hyperlactatemia, which is not necessarily accompanied by low tissue perfusion. Interpreting the origin and function of lactate may be of great clinical utility in sepsis, especially when circulating lactate levels are the basis for resuscitative measures.

Targeting Metabolic Dependencies Fueling the TCA Cycle to Circumvent Therapy Resistance in Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is one of the most prevalent blood cancers, characterized by a dismal survival rate. This poor outcome is largely attributed to AML cells that persist despite treatment and eventually result in relapse. Relapse-initiating cells exhibit diverse resistance mechanisms, encompassing genetic factors and, more recently discovered, nongenetic factors such as metabolic adaptations. Leukemic stem cells (LSC) rely on mitochondrial metabolism for their survival, whereas hematopoietic stem cells primarily depend on glycolysis. Furthermore, following treatments such as cytarabine, a standard in AML treatment for over four decades, drug-persisting leukemic cells exhibit an enhanced reliance on mitochondrial metabolism. In this issue of Cancer Research, two studies investigated dependencies of AML cells on two respiratory substrates, α-ketoglutarate and lactate-derived pyruvate, that support mitochondrial oxidative phosphorylation (OXPHOS) following treatment with the imipridone ONC-213 and the BET inhibitor INCB054329, respectively. Targeting lactate utilization by interfering with monocarboxylate transporter 1 (MCT1 or SLC16A1) or lactate dehydrogenase effectively sensitized cells to BET inhibition in vitro and in vivo. In addition, ONC-213 affected αKGDH, a pivotal NADH-producing enzyme of the TCA cycle, to induce a mitochondrial stress response through ATF4 activation that diminished the expression of the antiapoptotic protein MCL1, consequently promoting apoptosis of AML cells. In summary, targeting these mitochondrial dependencies might be a promising strategy to kill therapy-naïve and treatment-resistant OXPHOS-reliant LSCs and to delay or prevent relapse. See related articles by Monteith et al., p. 1101 and Su et al., p. 1084.

Abstract 4450: MYC upregulates MCT4 expression and promotes metabolic reprogramming and enhanced lactate utilization in LKB1-deficient NSCLC

Abstract STK11, which encodes the serine/threonine kinase LKB1, is the second most commonly altered tumor suppressor in non-small cell lung cancer (NSCLC). LKB1 loss is frequently co-mutated with KRAS and associated with primary resistance to immunotherapy, which is partially due to MCT4-dependent lactate secretion. However, the mechanisms driving MCT4 elevation and metabolic reprogramming remains unclear. We hypothesized that increased MYC expression, which is associated with LKB1 loss, plays a pivotal role in metabolic alterations, promoting lactate incorporation and maintaining redox homeostasis. To explore the impact of lactate on tumor cells with LKB1 loss, we performed metabolic profiling on KRAS mutant (K) murine lung cancer cells with or without LKB1 knockout (KL) treated with either glucose or lactate as the carbon source. PLS analysis indicated that there was no notable difference between K and KL cells after glucose treatment. However, we observed significant changes in metabolites between K and KL cells when treated with lactate. Differentially altered metabolites included TCA-related components such as acetyl-CoA and glutamate, indicating enhanced lactate utilization in KL tumor cells. We also noticed that KL cells showed increased oxidative phosphorylation (OXPHOS) with the addition of lactate, with increased GSH/GSSH and NADPH/NADP+ ratios, suggesting that, as compared to LKB1-intact cells, LKB1-deficient cells had an enhanced ability to utilize OXPHOS and maintain redox homeostasis with lower levels of ROS generation when utilizing lactate as an energy source. However, in KL cells, MYC knockout (KO) or MCT4 KO partially abolished the lactate-induced OXPHOS and increased ROS. Moreover, [U-13C]lactate tracing revealed that isotopologues were significantly enriched in TCA components in KL cells, and this was reversed by either MYC KO or MCT4 KO, suggesting that MYC and MCT4 were critical for lactate reutilization in KL tumor cells. We observed that MYC could directly bind to the promoter region and transcriptionally activate MCT4 expression, and restoring MCT4 in MYC KO cells enhanced lactate incorporation and decreased ROS levels. Finally, we injected KL murine tumor cells with or without MYC/MCT4 KO into mice and infused [U-13C]lactate to detect the isotopologues distribution in vivo. KL tumors showed significantly enhanced lactate incorporation as compared to K tumors, while MYC KO or MCT4 KO reversed these phenotypes. Collectively, our data indicates that in LKB1-deficient tumors, upregulation of MYC promotes MCT4 expression and increases lactate incorporation and utilization, and that can be inhibited by targeting MYC or MCT4. These findings provide insight into the mechanisms driving the metabolic reprogramming and aggressive phenotype of KRAS-mutant LKB1-deficient tumors and identify a novel therapeutic strategy for this recalcitrant subgroup. Citation Format: Yu Qian, David Molkentine, Yifan Kong, Qian Huang, Chendong Yang, Alissa Poteete, Alvaro P. Guimaraes, Peixin Jiang, Ferdinandos Skoulidis, Alexandre Reuben, John D. Minna, Ralph J. DeBerardinis, John V. Heymach. MYC upregulates MCT4 expression and promotes metabolic reprogramming and enhanced lactate utilization in LKB1-deficient NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4450.