Excess Lactate Production Research Articles

The noncanonical function of borealin, a component of chromosome passenger complex, promotes glycolysis via stabilization of survivin in squamous cell carcinoma cells

The chromosome passenger complex (CPC) is a kinase complex formed by Aurora B, borealin, survivin and inner centromere protein (INCENP). The CPC is active during mitosis and contributes to proper chromosome segregation via the phosphorylation of various substrates. Overexpression of each CPC component has been reported in most cancers. However, its significance remains unclear, as only survivin is known to confer chemoresistance. This study showed that the overexpression of borealin, a CPC component, stabilized survivin protein depending on its interaction with survivin. Unexpectedly, the accumulation of survivin by borealin overexpression did not affect the well-characterized functions of survivin, such as chemoresistance and cell proliferation. Interestingly, the overexpression of borealin promoted lactate production but not the overexpression of the deletion mutant that lacks the ability to bind to survivin. Consistent with these findings, the expression levels of glycolysis-related genes were enhanced in borealin-overexpressing cancer cells. Meanwhile, the overexpression of survivin alone did not promote lactate production. Overall, the accumulation of the borealin–survivin complex promoted glycolysis in squamous cell carcinoma cells. This mechanism may contribute to cancer progression via excessive lactate production.

Trimetazidine, a metabolic modulator, attenuates silica-induced pulmonary fibrosis and decreases lactate levels and LDH activity in rats.

Pulmonary fibrosis has been recently linked to metabolic dysregulation. Silica-induced pulmonary fibrosis in rats was employed by the current study to explore the effects of trimetazidine (a metabolic modulator-antianginal drug; TMZ) on silica-induced pulmonary fibrosis. Pulmonary fibrosis was induced by intranasal instillation of silica (50 mg/100 µl/rat) in TMZ versus vehicle-treated rats. Body weights of rats, weights of lungs, and wet-to-dry lung weights were determined. Various parameters were also measured in serum, bronchoalveolar lavage fluid (BALF) in addition to lung tissue homogenates. Moreover, histopathological examination of sectioned lungs for lesion score and distribution and histochemical detection of myeloperoxidase (MPO) in lung tissues were also performed. No significant differences were observed in body weight gains, lung coefficients, lung weights, and wet-to-dry lung weight in silica versus control rats. Elevated lactate levels in serum and lung homogenates were significantly attenuated by TMZ. In addition, lactate dehydrogenase activity, transforming growth factor-β, and total proteins in BALF were significantly normalized with TMZ. Moreover, TMZ significantly increased reduced glutathione and adenosine triphosphate levels and decreased nitrate/nitrite and hydroxyproline content in lungs of silica-treated rats. Histopathological examination of lungs revealed more than 56% reduction in lesion score and distribution by TMZ. MPO expression in lungs of silica-treated rats was also significantly attenuated by TMZ. TMZ attenuates silica-induced pulmonary fibrosis, an effect that could be mediated by suppressing anaerobic glycolysis-induced excessive lactate production. Regulation of oxidative stress could also play a role in TMZ-promoted protective effects.

Attenuation of glutamine synthetase selection marker improves product titer and reduces glutamine overflow in Chinese hamster ovary cells.

The glutamine synthetase (GS) expression system is commonly used to ensure stable transgene integration and amplification in Chinese hamster ovary (CHO) host lines. Transfected cell populations are typically grown in the presence of the GS inhibitor, methionine sulfoximine (MSX), to further select for increased transgene copy number. However, high levels of GS activity produce excess glutamine. We hypothesized that attenuating the GS promoter while keeping the strong IgG promoter on the GS-IgG expression vector would result in a more efficient cellular metabolic phenotype. Herein, we characterized CHO cell lines expressing GS from either an attenuated promoter or an SV40 promoter and selected with/without MSX. CHO cells with the attenuated GS promoter had higher IgG specific productivity and lower glutamine production compared to cells with SV40-driven GS expression. Selection with MSX increased both specific productivity and glutamine production, regardless of GS promoter strength. 13 C metabolic flux analysis (MFA) was performed to further assess metabolic differences between these cell lines. Interestingly, central carbon metabolism was unaltered by the attenuated GS promoter while the fate of glutamate and glutamine varied depending on promoter strength and selection conditions. This study highlights the ability to optimize the GS expression system to improve IgG production and reduce wasteful glutamine overflow, without significantly altering central metabolism. Additionally, a detailed supplementary analysis of two "lactate runaway" reactors provides insight into the poorly understood phenomenon of excess lactate production by some CHO cell cultures.

The Triangle Relationship Between Long Noncoding RNA, RIG-I-like Receptor Signaling Pathway, and Glycolysis.

Long noncoding RNA (LncRNA), a noncoding RNA over 200nt in length, can regulate glycolysis through metabolic pathways, glucose metabolizing enzymes, and epigenetic reprogramming. Upon viral infection, increased aerobic glycolysis providzes material and energy for viral replication. Mitochondrial antiviral signaling protein (MAVS) is the only protein-specified downstream of retinoic acid-inducible gene I (RIG-I) that bridges the gap between antiviral immunity and glycolysis. MAVS binding to RIG-I inhibits MAVS binding to Hexokinase (HK2), thereby impairing glycolysis, while excess lactate production inhibits MAVS and the downstream antiviral immune response, facilitating viral replication. LncRNAs can also regulate antiviral innate immunity by interacting with RIG-I and downstream signaling pathways and by regulating the expression of interferons and interferon-stimulated genes (ISGs). Altogether, we summarize the relationship between glycolysis, antiviral immunity, and lncRNAs and propose that lncRNAs interact with glycolysis and antiviral pathways, providing a new perspective for the future treatment against virus infection, including SARS-CoV-2.

Pharmacological Inhibition of MCT4 Reduces 4-Hydroxytamoxifen Sensitivity by Increasing HIF-1α Protein Expression in ER-Positive MCF-7 Breast Cancer Cells.

The rate of glycolysis in cancer cells is higher than that of normal cells owing to high energy demands, which results in the production of excess lactate. Monocarboxylate transporters (MCTs), especially MCT1 and MCT4, play a critical role in maintaining an appropriate pH environment through lactate transport, and their high expression is associated with poor prognosis in breast cancer. Thus, we hypothesized that inhibition of MCTs is a promising therapeutic target for adjuvant breast cancer treatment. We investigated the effect of MCT inhibition in combination with 4-hydroxytamoxifen (4-OHT), an active metabolite of tamoxifen, using two estrogen receptor (ER)-positive breast cancer cell lines, MCF-7 and T47D. Lactate transport was investigated in cellular uptake studies. The cytotoxicity of 4-OHT was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In both cell lines evaluated, MCT1 and MCT4 were constitutively expressed at the mRNA and protein levels. [14C]-L-lactate uptake by both cells was significantly inhibited by bindarit, a selective MCT4 inhibitor, but weakly affected by 5-oxoploline (5-OP), a selective MCT1 inhibitor. The results of the MTT assay showed that combination with bindarit, but not 5-OP, decreased 4-OHT sensitivity. Bindarit significantly increased the levels of hypoxia-inducible factor-1α (HIF-1α) in MCF-7 cells. Moreover, HIF-1α knockdown significantly increased 4-OHT sensitivity, whereas induction of HIF-1α by hypoxia decreased 4-OHT sensitivity in MCF-7 cells. In conclusion, pharmacological MCT4 inhibition confers resistance to 4-OHT rather than sensitivity, by increasing HIF-1α protein levels. In addition, HIF-1α inhibition represents a potential therapeutic strategy for enhancing 4-OHT sensitivity.

Nicotinamide as a Foundation for Treating Neurodegenerative Disease and Metabolic Disorders.

Neurodegenerative disorders impact more than one billion individuals worldwide and are intimately tied to metabolic disease that can affect another nine hundred individuals throughout the globe. Nicotinamide is a critical agent that may offer fruitful prospects for neurodegenerative diseases and metabolic disorders, such as diabetes mellitus. Nicotinamide protects against multiple toxic environments that include reactive oxygen species exposure, anoxia, excitotoxicity, ethanolinduced neuronal injury, amyloid (Aß) toxicity, age-related vascular disease, mitochondrial dysfunction, insulin resistance, excess lactate production, and loss of glucose homeostasis with pancreatic β-cell dysfunction. However, nicotinamide offers cellular protection in a specific concentration range, with dosing outside of this range leading to detrimental effects. The underlying biological pathways of nicotinamide that involve the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), and mammalian forkhead transcription factors (FoxOs) may offer insight for the clinical translation of nicotinamide into a safe and efficacious therapy through the modulation of oxidative stress, apoptosis, and autophagy. Nicotinamide is a highly promising target for the development of innovative strategies for neurodegenerative disorders and metabolic disease, but the benefits of this foundation depend greatly on gaining a further understanding of nicotinamide's complex biology.

Juvenile social isolation leads to schizophrenia-like behaviors via excess lactate production by astrocytes

Repeated early environmental deprivation is regarded as a typical paradigm to mimic the behavioral abnormalities and brain dysfunction that occur in psychiatric disorders. Previously, we reported that social isolation could disrupt prepulse inhibition (PPI) in Sprague-Dawley (SD) rats, producing the typical characteristics of a schizophrenia animal model. Based on further analysis of previous proteomic and transcriptomic data, a disrupted balance of glucose metabolism was found in the prefrontal cortex (PFC) of isolated rats. Subsequently, in the first experiment of this study, we investigated the effects of juvenile social isolation (postnatal days (PND) 21–34) on PPI and lactate levels in PND56 rats. Compared with the social rearing group, rats in the isolated rearing group showed disrupted PPI and increased lactate levels in the PFC. In the second experiment, at PND55, the model rats were acutely injected with a glycogen phosphorylase inhibitor (4-dideoxy-1,4-imino-darabinitol, DAB) or control saline in the bilateral PFC. Our data showed that acute DAB administration (50 pmol, 0.5 μl) significantly improved the disrupted PPI and decreased the levels of oxidative phosphorylation (OXPHOS)-related mRNAs as well as lactate. In summary, our results suggested that excess astrocytic lactate production was involved in the impairment of auditory sensory gating of isolated rats, which may contribute to the metabolic pathogenesis of schizophrenia.

From Glucose to Lactate and Transiting Intermediates Through Mitochondria, Bypassing Pyruvate Kinase: Considerations for Cells Exhibiting Dimeric PKM2 or Otherwise Inhibited Kinase Activity.

A metabolic hallmark of many cancers is the increase in glucose consumption coupled to excessive lactate production. Mindful that L-lactate originates only from pyruvate, the question arises as to how can this be sustained in those tissues where pyruvate kinase activity is reduced due to dimerization of PKM2 isoform or inhibited by oxidative/nitrosative stress, posttranslational modifications or mutations, all widely reported findings in the very same cells. Hereby 17 pathways connecting glucose to lactate bypassing pyruvate kinase are reviewed, some of which transit through the mitochondrial matrix. An additional 69 converging pathways leading to pyruvate and lactate, but not commencing from glucose, are also examined. The minor production of pyruvate and lactate by glutaminolysis is scrutinized separately. The present review aims to highlight the ways through which L-lactate can still be produced from pyruvate using carbon atoms originating from glucose or other substrates in cells with kinetically impaired pyruvate kinase and underscore the importance of mitochondria in cancer metabolism irrespective of oxidative phosphorylation.

Induction of ketosis as a potential therapeutic option to limit hyperglycemia and prevent cytokine storm in COVID-19

The severe form of coronavirus disease 19 (COVID-19) is characterized by cytokine storm syndrome (CSS) and disseminated intravascular coagulation (DIC). Diabetes, obesity, and hypertension have, as minor common denominators, chronic low-grade inflammation and high plasma myeloperoxidase levels, which could be linked to pulmonary phagocytic hyperactivation and CSS. The hyperactivation of M1 macrophages with a proinflammatory phenotype, which is linked to aerobic glycolysis, leads to the recruitment of monocytes, neutrophils, and platelets from circulating blood and plays a crucial role in thrombo-inflammation (as recently demonstrated in COVID-19) through the formation of neutrophil extracellular traps and monocyte-platelet aggregates, which could be responsible for DIC. The modulation of glucose availability for activated M1 macrophages by means of a eucaloric ketogenic diet (EKD) could represent a possible metabolic tool for reducing adenosine triphosphate production from aerobic glycolysis in the M1 macrophage phenotype during the exudative phase. This approach could reduce the overproduction of cytokines and, consequently, the accumulation of neutrophils, monocytes, and platelets from the blood. Second, an EKD could be advantageous for the metabolism of anti-inflammatory M2 macrophages because these cells predominantly express oxidative phosphorylation enzymes and are best fed by the oxidation of fatty acids in the mitochondria. An EKD could guarantee the availability of free fatty acids, which are an optimal fuel supply for these cells. Third, an EKD, which could reduce high lactate formation by macrophages due to glycolysis, could favor the production of interferon type I, which are inhibited by excessive lactate production. From a practical point of view, the hypothesis, in addition to being proven in clinical studies, must obviously take into account the contraindications of an EKD, particularly type 1 or 2 diabetes treated with drugs that can cause hypoglycemia, to avoid the risk for side effects of the diet.

SAT-131 Asymptomatic Severe Hypoglycemia with Lactic Acidosis in a Case of Non-Hodgkin’s Lymphoma - an Unusual Phenomenon of Hyper-Warburgism

INTRODUCTIONHypoglycemia in malignancy is well known with several etiologies; impaired liver function, insulin receptor autoantibodies, production of insulin-like substance by malignant cells or large tumor burden. Another possible mechanism is the Warburg effect where metabolism shifts towards glycolytic pathways over oxidative phosphorylation even under aerobic conditions leading to excess lactate production. This leads to glucose consumption due to shunting of glucose away from normal cells to cancer cells. Very few cases of lactic acidosis and severe hypoglycemia in Non-Hodgkin’s Lymphoma have been described in the literature. We report such an unusual case here.CASE DISCUSSIONA 52-year-old, African-American male was admitted for severe malnutrition with 80 lb. weight loss, severe hypoglycemia and progressively increasing right chest wall mass. On arrival, he had no classic symptoms of hypoglycemia. Physical exam revealed persistent tachycardia, white patches on oral mucosa and posterior tongue, and an indurated mass on right chest wall with extensive swelling of right upper limb. Lab work was significant for blood glucose (BG) of 41 mg/dL (60–100), lactate 16 mmol/L (0.5 to 2), anion gap 26 mEq/L (3–10), albumin 2.3 g/dL (3.4 to 5.4) and normal renal and liver function tests. Fingerstick sugar readings were persistently in the 20s with no response to multiple boluses of dextrose and glucagon. He was started on dextrose 5% (D5) drip and intravenous solumedrol. Solumedrol was weaned off and D5 titrated down to investigate causes of hypoglycemia. BG dropped to 39 and corresponding labs showed insulin level of < 2 mcUnit/mL (2–20), C-peptide of 0.2 ng/mL (0.8–6.0) and ketone level of 0.2 mmol/L (<0.4). IGF-1 and IGF-2 were both low at 26 ng/mL (61–200) and 113 ng/mL (333–967) respectively. A CT torso with contrast showed bilateral pleural effusions, moderate pericardial effusions and a large ill-defined heterogeneous mass along anterior chest wall. He underwent ultrasound guided biopsy of the chest wall mass and diagnosed with diffuse large B-cell lymphoma. He also tested positive for HIV/AIDS and Hepatitis C. PET scan showed diffuse FDG (fluorodeoxyglucose) uptake consistent with advanced disease. He was started on chemotherapy and lactate and BG normalized soon after 1st cycle.CONCLUSIONIn our case; suppressed insulin, low C-peptide and IGF-2 levels indicate non-insulin mediated hypoglycemia due to rapid glucose utilization by cancer cells. Severe hypoglycemia with lack of neuroglycopenic symptoms suggests use of lactate (rather than glucose) as an alternative metabolic fuel for brain, thus preserving its function. Our patient presented with an exaggerated Warburg effect (hyper-Warburgism) as evident by extreme glucose consumption, severe lactic acidosis and large tumor burden on FDG/PET. Chemotherapy must be instituted timely to correct these abnormalities.

Impact of Sirtuin Enzymes on the Altered Metabolic Phenotype of Malignantly Transformed Cells.

Sirtuins compose a unique collection of histone deacetylase enzymes that have a wide variety of enzymatic activities and regulate diverse cell functions such as cellular metabolism, longevity and energy homeostasis, mitochondrial function, and biogenesis. Impaired sirtuin functions or alterations of their expression levels may result in several pathological conditions and contribute to the altered metabolic phenotype of malignantly transformed cells in a significant manner. In the twenty-first century, principles of personalized anticancer treatment need to involve not only the evaluation of changes of the genetic material, but also the mapping of epigenetic and metabolic alterations, to both of which the contribution of sirtuin enzymes is fundamental. Since sirtuins are central players in the maintenance of cellular energy and metabolic homeostasis, they are key elements in the development of metabolic transformation of cancer cells referred to as the Warburg effect. Although its most well-known features are enhanced glycolysis and excessive lactate production, Warburg effect has several aspects involving both carbohydrate, lipid, and amino acid metabolism, among which different tumor types have different preferences. Therefore, energy supply of cancer cells can be impaired by a growing number of antimetabolite agents, for which appropriate vectors are strongly needed. However, data are controversial about their tumor suppressor or oncogenic properties, the biological effects of sirtuin enzymes strongly depend on the tissue microenvironment (TME) in which they are expressed. Immune cells are regarded as key players of TME. Sirtuins regulate the survival, activation, metabolism, and mitochondrial function of these cells, therefore, they are not only single elements, but key regulators of the network that determines anticancer immunity. Altered metabolism of tumor cells induces changes in the gene expression pattern of cells in TME, due to altered concentrations of metabolite cofactors of epigenetic modifiers including sirtuins. In summary, epigenetic and metabolic alterations in malignant diseases are influenced by sirtuins in a significant manner, and should be treated in a personalized approach. Since they often develop in early stages of cancer, broad examination of these alterations is required at time of the diagnosis in order to provide a personalized combination of distinct therapeutic agents.

Type B Lactic Acidosis in Adults with Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare syndrome that can present with variable clinical and laboratory manifestations, and some distinct features are seen in adults. Type B lactic acidosis, which occurs in the absence of tissue hypoxia, has been reported in a few adult patients with HLH. We report a case of HLH presenting with type B lactic acidosis, with a literature review of this association. A 48-year-old Saudi woman with a past medical history of hypertension, dyslipidemia, and morbid obesity, presented with a 1-month history of intermittent high-grade fever up to 39°C daily. The patient was admitted for further evaluation of fever and was in our hospital for 70 days. Initial laboratory investigations revealed normocytic hypochromic anemia (102 g/L [normal 120-160]), lactic acidosis (2.36 mmol/L [0.5-2.2]), mild transaminitis, and elevated levels of lactate dehydrogenase (1761 U/L [125-220]), erythrocyte sedimentation rate (95 mm/hr [0-20]), and ferritin (1090.5 μg/L [4.6-204.0]). Further investigations failed to reveal any autoimmune or rheumatologic disease and extensive septic workup was negative. Lymphocyte subset by flow cytometry showed a low percentage of absolute natural killer cells (5% [10-20%]). Abdominal CT revealed splenomegaly with a span of 16.5 cm. Positron emission tomography-CT scan showed diffuse prominence of splenic activity, with a standardized uptake value of 4.5, and bone marrow activity throughout the axial skeleton. Liver biopsy and bone marrow aspiration were unremarkable. A month after admission, her anemia worsened with the hemoglobin level gradually dropping to 63 g/L prompting multiple transfusions. Lactic acid levels remained persistently elevated throughout this period [Figure 1]. A trial of intravenous steroids and immunoglobulins failed to decrease the lactic acid level [Figure 1; A to B]. The hospital course was complicated by Acinetobacter baumannii pneumonia requiring antibiotics [Figure 1; C to E]. Two months after the initial presentation, she developed pancytopenia, and repeated bone marrow aspiration and biopsy showed hemophagocytosis. Repeated ferritin level was more than 40,000 μg/L with hypertriglyceridemia (2.92 mmol/L [&lt;1.7]), and hypofibrinogenemia (0.9 g/L [1.5-4.1]). HLH-94 protocol with etoposide (150 mg/m2twice weekly) and dexamethasone (10 mg/m2) was commenced; however, the patient continued to deteriorate prompting elective intubation. She then developed acute acalculous cholecystitis and brain CT revealed a large central pontine hypodensity. Nine days after initiation, the patient was switched from the HLH-94 protocol to alemtuzumab, however, the patient arrested and passed away. To our knowledge, this is the first report of HLH presenting with persistent lactic acidosis lasting several weeks. Although no cause was found, this patient likely had HLH that was not detected early. We searched the PubMed and EMBASE databases for English-language reports describing adult patients (&gt;18 years) with HLH and lactic acidosis. Patients with type A lactic acidosis, associated with tissue hypoxia, were excluded. Five case reports describing patients with variable underlying diagnosis causing HLH and type B lactic acidosis were identified (Table I). Lactic acidosis started before HLH was diagnosed in all patients except one, in whom lactic acidosis developed two days after diagnosis. All patients had neither sepsis nor hypotension at the time of lactic acidosis. The mechanism of type B lactic acidosis in HLH is poorly understood and is likely multifactorial. As HLH in adults is more likely to be secondary to malignancies, Warburg effect, a high rate of glycolysis exhibited by tumor cells, has been proposed as the cause in these cases. Alternatively, acute cytokine hyperactivation in inflammatory states can enhance lactate dehydrogenase activity leading to excess lactic acid production. Inflammation, infection, or tumor cells can also induce stress and accelerate aerobic glycolysis-which does not depend on hypoxia-resulting in excess lactate production. Finally, acute hepatic dysfunction, a common finding in adult-onset HLH, can impair lactate clearance and further elevate levels. This report suggests that type B lactic acidosis may be a manifestation of HLH. Analyses of large HLH registries can better clarify the diagnostic and prognostic value of type B lactic acidosis in adult-onset HLH. Disclosures No relevant conflicts of interest to declare.

Forecasting and control of lactate bifurcation in Chinese hamster ovary cell culture processes.

Biomanufacturing exhibits inherent variability that can lead to variation in performance attributes and batch failure. To help ensure process consistency and product quality the development of predictive models and integrated control strategies is a promising approach. In this study, a feedback controller was developed to limit excessive lactate production, a widespread metabolic phenomenon that is negatively associated with culture performance and product quality. The controller was developed by applying machine learning strategies to historical process development data, resulting in a forecast model that could identify whether a run would result in lactate consumption or accumulation. In addition, this exercise identified a correlation between increased amino acid consumption and low observed lactate production leading to the mechanistic hypothesis that there is a deficiency in the link between glycolysis and the tricarboxylic acid cycle. Using the correlative process parameters to build mechanistic insight and applying this to predictive models of lactate concentration, a dynamic model predictive controller (MPC) for lactate was designed. This MPC was implemented experimentally on a process known to exhibit high lactate accumulation and successfully drove the cell cultures towards a lactate consuming state. In addition, an increase in specific titer productivity was observed when compared with non‐MPC controlled reactors.

Lactate and cancer: spinal metastases and potential therapeutic targets (part 2)

Metastatic spine disease is a heterogeneous clinical condition commonly requiring surgical intervention. Despite this heterogeneity, all cases share the common theme of altered tumor metabolism, characterized by aerobic glycolysis and high lactate production. Here we review the existing literature on lactate metabolism as it pertains to tumor progression, metastasis, and the formation of painful bone lesions. We included articles from the English literature addressing the role of lactate metabolism in the following: (I) primary tumor aggressiveness, (II) local tissue invasion, (III) metastasis formation, and (IV) generation of oncologic pain. We also report current investigations into restoring normal lactate metabolism as a means of impeding tumor growth and the formation of bony metastases. Both in vivo and in vitro experiments suggest that high lactate levels may be necessary for tumor cell growth, as small molecules inhibitors of lactate dehydrogenase (LDH5/LDHA) decrease both the rate of tumor growth and formation of metastases. Additionally, in vitro evidence strongly implicates lactate in tumor cell migration by driving the amoeboid movements of these cells. Acidification of the local bony tissue by excess lactate production activates CGRP+ neurons in the bone marrow and periosteum to generate oncologic bone pain. High lactate may also increase expression of acid sensing receptors in these neurons to generate the neuropathic pain seen in some patients with metastatic disease. Lastly, investigation into lactate-directed therapeutics is still early in development. Initial preclinical trials looking at LDH5/LDHA inhibitors as well as inhibitors of lactate transporters (MCT1) have demonstrated promise, but clinical work has been restricted to a single phase I trial. Lactate appears to play a crucial role in the pathogenesis of metastatic spine disease. Efforts are ongoing to identify small molecules inhibitors of targets in the lactogenic pathway capable of preventing the formation of osseous metastatic disease.

Lactate Activates the E2F Pathway to Promote Cell Motility by Up-Regulating Microtubule Modulating Genes.

Excess lactate production due to enhanced aerobic glycolysis is characteristic of malignant cancers, which is also intimately associated with poor cancer prognoses. Although tumor-associated lactate contributes to all major steps in carcinogenesis, its action mechanism remains obscure. To understand the molecular mechanism of the lactate-induced tumor metastatic process, we identified an array of lactate-responsive genes via transcriptome analysis of a metformin-induced hyper-glycolytic liver cancer model. Gene set enrichment analysis suggested E2F-RB pathway as the dominant regulator of the lactate-induced gene expression. We experimentally verified that lactate indeed activates E2F-mediated transcription by promoting E2F1 protein accumulation through a posttranscriptional mechanism. Literature-based analysis of target pathways potentially modulated by 136 top-ranked genes indicated that genes functioning in cell-cell or cell-matrix communications dominate the lactate-induced gene expression. Especially, those regulating microtubule functions, including a group of kinesin family members, were significantly up-regulated in lactate- and E2F1-dependent manners. Depletion of E2F1 or kinesins (KIF2C, KIF18B, KIF20A) led to deformation of microtubule structures, impairing cell motility as much as the deficit in lactate production. These results indicate that E2F pathway activation by tumor-associated lactate and subsequent transcriptional activation of microtubule functions play crucial roles in tumor metastasis, providing mechanistic clues to cell motility-directed anti-cancer strategies.

The food additive BHA modifies energy metabolism in the perfused rat liver

A study of the effects of butylated hydroxyanisole (BHA) on the hepatic metabolism was conducted with emphasis on parameters linked to energy metabolism and mitochondrial reactive oxygen species production. The experimental systems were the isolated perfused rat liver and isolated mitochondria. It was found that BHA inhibits biosynthetic pathways (gluconeogenesis) and ammonia detoxification, which are dependent on ATP generated within the mitochondria. Conversely, the compound stimulated glycolysis and fructolysis, which are compensatory phenomena for an inhibited mitochondrial ATP generation. Furthermore, BHA diminished the cellular ATP content under conditions where the mitochondrial respiratory chain was the only source of this compound. Inhibition of gluconeogenesis started at the concentration of 50 μM and was generally pronounced at concentrations under 200 μM. Several effects, however, were prominent only at the concentrations of 500 and 750 μM. BHA can be considered, thus, a mild metabolic agent that becomes toxic only at high doses. An aggravating factor could be the observation that BHA exerts a net stimulating action on reactive oxygen species (ROS) production in isolated mitochondria, an observation that contradicts the general notion that the compound acts primarily as an antioxidant. Considerable time was required for the reversion of most effects after removal of the compound from the circulation. In toxicological terms, besides the lack of circulating glucose, one can expect metabolic acidosis due to excess lactate production, impairment of ammonia detoxification and cell damage due to a deficient maintenance of its homeostasis and possible excessive ROS production.

The metabolic effects of diuron in the rat liver

A systematic study on the effects of diuron on the hepatic metabolism was conducted with emphasis on parameters linked to energy metabolism. The experimental system was the isolated perfused rat liver. The results demonstrate that diuron inhibited biosynthesis (gluconeogenesis) and ammonia detoxification, which are dependent of ATP generated within the mitochondria. Conversely, it stimulated glycolysis and fructolysis, which are compensatory phenomena for an inhibited mitochondrial ATP generation. Furthermore, diuron diminished the cellular ATP content under conditions where the mitochondrial respiratory chain was the only source of this compound. Besides the lack of circulating glucose due to gluconeogenesis inhibition, one can expect metabolic acidosis due to excess lactate production, impairment of ammonia detoxification and cell damage due to a deficient maintenance of its homeostasis. Some of the general signs of toxicity that were observed in diuron-treated rats can be attributed, partly at least, to the effects of the herbicide on energy metabolism.

Hyaluronan production and molecular weight is enhanced in pathway-engineered strains of lactate dehydrogenase-deficient Lactococcus lactis

The potential advantages of hyaluronic acid (HA) production by metabolically-engineered Lactococcus lactis is constrained by the lower molecular weight and yield of HA obtained in these strains, compared to natural producers. Earlier studies have correlated lower HA yield with excessive lactate production in L. lactis cultures (Chauhan et al., 2014). In the present study, a three-fold increase was observed in the amount as well as molecular weight of HA produced by recombinant ldh-mutant L. lactis strains. The diversion from lactate production in the ldh-mutant strains resulted in excess ethanol and acetoin production and higher NAD+/NADH ratio in these cultures. The initial NAD+/NADH ratio showed a positive correlation with HA molecular weight as well as with the HA-precursor ratio (UDP-GlcUA/UDP-GlcNAc). The influence of NAD+/NADH ratio on regulation of the concerned metabolic pathways was assessed by transcriptional analysis of key genes having putative binding sites of the NADH-binding transcriptional factor, Rex.

Enzyme Functionalized Metal Nanostructures for Enhanced Electrochemical Detection of Lactate

Lactate is a key molecule in the anaerobic energy system of humans, primarily considered as the biomarker for tissue oxidative stress. Heavy workout, sepsis, trauma and cancer cause excess lactate production in bio-fluids including sweat. Therefore, lactate measurement is integral for clinical emergencies, sports and general medicine. An enzymatic electrochemical biosensor comprising lactate oxidase immobilized on metal nanostructures is developed here for continuous monitoring of lactate. The sensing mechanism entails detection of H2O2 produced during enzymatic oxidation of lactate. Three kinds of metal nanostructures, viz. gold, copper, and platinum were tested as catalysts for electrochemical oxidation of H2O2to increase the electro-activity and detection sensitivity. Scanning electron microcopy and cyclic voltametry were used to characterize the nano-structured biosensors. Results show that the platinum nanoflakes decorated electrode provides a better sensitivity and detection limit towards lactate detection by providing favorable microenvironment to retain the bioactivity of the enzyme.

Ionizing radiation induces myofibroblast differentiation via lactate dehydrogenase.

Pulmonary fibrosis is a common and dose-limiting side-effect of ionizing radiation used to treat cancers of the thoracic region. Few effective therapies are available for this disease. Pulmonary fibrosis is characterized by an accumulation of myofibroblasts and excess deposition of extracellular matrix proteins. Although prior studies have reported that ionizing radiation induces fibroblast to myofibroblast differentiation and collagen production, the mechanism remains unclear. Transforming growth factor-β (TGF-β) is a key profibrotic cytokine that drives myofibroblast differentiation and extracellular matrix production. However, its activation and precise role in radiation-induced fibrosis are poorly understood. Recently, we reported that lactate activates latent TGF-β through a pH-dependent mechanism. Here, we wanted to test the hypothesis that ionizing radiation leads to excessive lactate production via expression of the enzyme lactate dehydrogenase-A (LDHA) to promote myofibroblast differentiation. We found that LDHA expression is increased in human and animal lung tissue exposed to ionizing radiation. We demonstrate that ionizing radiation induces LDHA, lactate production, and extracellular acidification in primary human lung fibroblasts in a dose-dependent manner. We also demonstrate that genetic and pharmacologic inhibition of LDHA protects against radiation-induced myofibroblast differentiation. Furthermore, LDHA inhibition protects from radiation-induced activation of TGF-β. We propose a profibrotic feed forward loop, in which radiation induces LDHA expression and lactate production, which can lead to further activation of TGF-β to drive the fibrotic process. These studies support the concept of LDHA as an important therapeutic target in radiation-induced pulmonary fibrosis.