Stimulation Of Lactate Production Research Articles

Effects of 12 Weeks of Moderate-intensity Continuous Exercise and High-intensity Interval Exercise on Cognitive Function in Elderly Subjects

OBJECTIVES This study analyzed the possibility of brain function activation after exercise training of high-intensity interval exercise and moderate-intensity continuous exercise in elderly people.METHODS The subjects of the study were elderly female people aged 65 years or older and were divided into three groups : control group, moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT). Changes of body composition, physical fitness, cognitive function, and cognitive function-related blood variables were compared between before and after 12 weeks of exercise training.RESULTS Body weight, BMI (body mass index), and WHR (waist hip ratio) of body composition in HIIT group decreased significantly (p<0.05) after exercise training, and there was no significant difference in MICT group and the control group. HIIT group significantly (p<0.05) improved in grip strength, muscular endurance, flexibility, balance, cardiorespiratory endurance, and walking ability after exercise training, while MICT group showed significant (p<0.05) improvements only in flexibility, balance, and cardiorespiratory endurance. Regarding blood variables, HIIT group showed significant (p<0.05) differences in BDNF (brain-derived neurotrophic factor), irisin, and β-amyloid after exercise training, MICT group showed significant (p<0.05) differences only in β-amyloid. Cognitive function in HIIT group and MICT group significantly (p<0.05) improved in terms of temporal and spatial orientation, memory, and total scores after exercise training. During the recovery phase after one session of high-intensity interval exercise, blood lactic acid concentration increased significantly.CONCLUSIONS This study was confirmed the possibility of giving that high-intensity interval exercise for the elderly not only produces positive changes in body composition and improves physical fitness and cognitive function, but also frequently stimulates lactate production, helping to activate brain function through changes in BDNF and irisin in the blood.

Perilipin 5 deficiency aggravates cardiac hypertrophy by stimulating lactate production in leptin-deficient mice

BackgroundPerilipin 5 (Plin5) is well known to maintain the stability of intracellular lipid droplets (LDs) and regulate fatty acid metabolism in oxidative tissues. It is highly expressed in the heart, but its roles have yet to be fully elucidated.MethodsPlin5-deficient mice and Plin5/leptin-double-knockout mice were produced, and their histological structures and myocardial functions were observed. Critical proteins related to fatty acid and glucose metabolism were measured in heart tissues, neonatal mouse cardiomyocytes and Plin5-overexpressing H9C2 cells. 2-NBDG was employed to detect glucose uptake. The mitochondria and lipid contents were observed by MitoTracker and BODIPY 493/503 staining in neonatal mouse cardiomyocytes.ResultsPlin5 deficiency impaired glucose utilization and caused insulin resistance in mouse cardiomyocytes, particularly in the presence of fatty acids (FAs). Additionally, Plin5 deficiency increased the NADH content and elevated the expression of lactate dehydrogenase (LDHA) in cardiomyocytes, which resulted in increased lactate production. Moreover, when fatty acid oxidation was blocked by etomoxir or LDHA was inhibited by GSK2837808A in Plin5-deficient cardiomyocytes, glucose utilization was improved. Leptin-deficient mice exhibited myocardial hypertrophy, insulin resistance and altered substrate utilization, and Plin5 deficiency exacerbated myocardial hypertrophy in leptin-deficient mice.ConclusionOur results demonstrated that Plin5 plays a critical role in coordinating fatty acid and glucose oxidation in cardiomyocytes, providing a potential target for the treatment of metabolic disorders in the heart.Graphic abstract

Exploring the effect of a microencapsulated citrus essential oil on in vitro fermentation kinetics of pig gut microbiota.

Essential oils (EOs) have emerged as a potential alternative to antibiotics in pig breeding due to their antimicrobial properties. Citrus EOs, a common by-product of the orange juice industry, can be an interesting alternative from a financial perspective due to their huge offer in the global market. Thus, the effect of a citrus EO, and specifically different formulations of Brazilian Orange Terpenes (BOT), on pig gut microbiota was evaluated by means of an in vitro fermentation model simulating different sections of the pig gut (stomach, ileum, and colon). Treatments consisted in: BOT in its unprotected form (BOT, 1.85 and 3.70 mg/mL), microencapsulated BOT (MBOT, 3.50 and 7.00 mg/mL), colistin (2 μg/mL), and a control. BOT and MBOT altered in a similar way the total bacterial 16S rRNA gene copies in the stomach only from 18 h of incubation onwards, and no metabolite production in terms of short-chain fatty acids (SCFAs) was detected. In ileal and colonic fermentations, BOT and MBOT affected ileal and colonic microbiota in terms of total bacterial 16S rRNA gene copies, reduced phylogenetic diversity, and altered composition (p < 0.05) as evidenced by the significant reduction of certain bacterial taxa. However, more pronounced effects were found for MBOT, indicating its higher antimicrobial effects compared to the unprotected BOT, and suggesting that the antibacterial efficiency of the unprotected BOT was probably enhanced by microencapsulation. Furthermore, MBOT stimulated lactate production in ileal fermentations and greatly stimulated overall SCFA production in colonic fermentations. This indicates that besides the shifts in ileal and colonic microbiota by the delivered EO (BOT), the wall material of microcapsules (chitosan/modified starch) might have worked as an additional carbon source with prebiotic functioning, stimulating growth and metabolic activity (SCFAs) of colonic bacteria.

The metabolic addiction of cancer stem cells

Cancer stem cells (CSC) are the minor population of cancer originating cells that have the capacity of self-renewal, differentiation, and tumorigenicity (when transplanted into an immunocompromised animal). These low-copy number cell populations are believed to be resistant to conventional chemo and radiotherapy. It was reported that metabolic adaptation of these elusive cell populations is to a large extent responsible for their survival and distant metastasis. Warburg effect is a hallmark of most cancer in which the cancer cells prefer to metabolize glucose anaerobically, even under normoxic conditions. Warburg’s aerobic glycolysis produces ATP efficiently promoting cell proliferation by reprogramming metabolism to increase glucose uptake and stimulating lactate production. This metabolic adaptation also seems to contribute to chemoresistance and immune evasion, a prerequisite for cancer cell survival and proliferation. Though we know a lot about metabolic fine-tuning in cancer, what is still in shadow is the identity of upstream regulators that orchestrates this process. Epigenetic modification of key metabolic enzymes seems to play a decisive role in this. By altering the metabolic flux, cancer cells polarize the biochemical reactions to selectively generate “onco-metabolites” that provide an added advantage for cell proliferation and survival. In this review, we explored the metabolic-epigenetic circuity in relation to cancer growth and proliferation and establish the fact how cancer cells may be addicted to specific metabolic pathways to meet their needs. Interestingly, even the immune system is re-calibrated to adapt to this altered scenario. Knowing the details is crucial for selective targeting of cancer stem cells by choking the rate-limiting stems and crucial branch points, preventing the formation of onco-metabolites.

Potential use of lactate for the treatment of neonatal hypoxic-ischemic encephalopathy.

Potential use of lactate for the treatment of neonatal hypoxic-ischemic encephalopathy.

Matrix Stiffness Modulates Metabolic Interaction between Human Stromal and Breast Cancer Cells to Stimulate Epithelial Motility.

Breast tumors belong to the type of desmoplastic lesion in which a stiffer tissue structure is a determinant of breast cancer progression and constitutes a risk factor for breast cancer development. It has been proposed that cancer-associated stromal cells (responsible for this fibrotic phenomenon) are able to metabolize glucose via lactate production, which supports the catabolic metabolism of cancer cells. The aim of this work was to investigate the possible functional link between these two processes. To measure the effect of matrix rigidity on metabolic determinations, we used compliant elastic polyacrylamide gels as a substrate material, to which matrix molecules were covalently linked. We evaluated metabolite transport in stromal cells using two different FRET (Fluorescence Resonance Energy Transfer) nanosensors specific for glucose and lactate. Cell migration/invasion was evaluated using Transwell devices. We show that increased stiffness stimulates lactate production and glucose uptake by mammary fibroblasts. This response was correlated with the expression of stromal glucose transporter Glut1 and monocarboxylate transporters MCT4. Moreover, mammary stromal cells cultured on stiff matrices generated soluble factors that stimulated epithelial breast migration in a stiffness-dependent manner. Using a normal breast stromal cell line, we found that a stiffer extracellular matrix favors the acquisition mechanistical properties that promote metabolic reprograming and also constitute a stimulus for epithelial motility. This new knowledge will help us to better understand the complex relationship between fibrosis, metabolic reprogramming, and cancer malignancy.

Offset of apparent hyperpolarized 13 C lactate flux by the use of adjuvant metformin in ionizing radiation therapy in vivo.

An increase in hyperpolarized (HP) [1‐13C]lactate production has been suggested as a biomarker for cancer occurrence as well as for response monitoring of cancer treatment. Recently, the use of metformin has been suggested as an anticancer or adjuvant treatment. By regulating the cytosolic NAD+/NADH redox state, metformin stimulates lactate production and increases the HP [1‐13C]lactate conversion rate in the kidney, liver, and heart. In general, increased HP [1‐13C]lactate is regarded as a sign of cancer occurrence or tumor growth. Thus, the relationship between the tumor suppression effect of metformin and the change in metabolism monitored by HP [1‐13C]pyruvate MRS in cancer treatment needs to be investigated. The present study was performed using a brain metastasis animal model with MDA‐MB‐231(BR)‐Luc breast cancer cells. HP [1‐13C]pyruvate MRS, T 2‐weighted MRI, and bioluminescence imaging were performed in groups treated with metformin or adjuvant metformin and radiation therapy. Metformin treatment alone did not display a tumor suppression effect, and the HP [1‐13C]lactate conversion rate increased. In radiation therapy, the HP [1‐13C]lactate conversion rate decreased with tumor suppression, with a p‐value of 0.028. In the adjuvant metformin and radiation treatment, the tumor suppression effect increased, with a p‐value of 0.001. However, the apparent HP [1‐13C]lactate conversion rate (K pl) was observed to be offset by two opposite effects: a decrease on radiation therapy and an increase caused by metformin treatment. Although HP [1‐13C]pyruvate MRS could not evaluate the tumor suppression effect of adjuvant metformin and radiation therapy due to the offset phenomenon, metabolic changes following only metformin pre‐treatment could be monitored. Therefore, our results indicate that the interpretation of HP [1‐13C]pyruvate MRS for response monitoring of cancer treatment should be carried out with caution when metformin is used as an adjuvant cancer therapy.

Hydrogen sulfide induces Ca2+ release from intracellular Ca2+ stores and stimulates lactate production in spinal cord astrocytes

Hydrogen sulfide (H2S) is a well-known inhibitor of the mitochondrial electron transport chain (ETC). H2S also increases intracellular Ca2+ levels in astrocytes, which are glial cells and that supply lactate as an energy substrate to neurons. Here, we examined the relationship between H2S-induced metabolic changes and Ca2+ responses in spinal cord astrocytes. Na2S (150 μM), an H2S donor, increased the intracellular Ca2+ concentration, which was inhibited by an ETC inhibitor and an uncoupler of mitochondrial oxidative phosphorylation. Na2S also increased the accumulation of extracellular lactate. Na2S alone did not change intracellular ATP content, but decreased it when glycolysis was inhibited. The Na2S-induced Ca2+ increase and accumulation of extracellular lactate were inhibited by emetine, an inhibitor of translocon complex, which mediates Ca2+ leak from the endoplasmic reticulum (ER). Furthermore, an inhibitor of the Ca2+-sensitive NADH shuttle decreased Na2S-mediated accumulation of lactate. We conclude that inhibition of the mitochondrial ETC by H2S induces Ca2+ release from mitochondria and the ER in spinal cord astrocytes, which increases lactate production. H2S may promote glycolysis by activating the Ca2+-sensitive NADH shuttle and facilitating the supply of lactate from astrocytes to neurons.

Lactate induces synapse-specific potentiation on CA3 pyramidal cells of rat hippocampus.

Neuronal activity within the physiologic range stimulates lactate production that, via metabolic pathways or operating through an array of G-protein-coupled receptors, regulates intrinsic excitability and synaptic transmission. The recent discovery that lactate exerts a tight control of ion channels, neurotransmitter release, and synaptic plasticity-related intracellular signaling cascades opens up the possibility that lactate regulates synaptic potentiation at central synapses. Here, we demonstrate that extracellular lactate (1-2 mM) induces glutamatergic potentiation on the recurrent collateral synapses of hippocampal CA3 pyramidal cells. This potentiation is independent of lactate transport and further metabolism, but requires activation of NMDA receptors, postsynaptic calcium accumulation, and activation of a G-protein-coupled receptor sensitive to cholera toxin. Furthermore, perfusion of 3,5- dihydroxybenzoic acid, a lactate receptor agonist, mimics this form of synaptic potentiation. The transduction mechanism underlying this novel form of synaptic plasticity requires G-protein βγ subunits, inositol-1,4,5-trisphosphate 3-kinase, PKC, and CaMKII. Activation of these signaling cascades is compartmentalized in a synapse-specific manner since lactate does not induce potentiation at the mossy fiber synapses of CA3 pyramidal cells. Consistent with this synapse-specific potentiation, lactate increases the output discharge of CA3 neurons when recurrent collaterals are repeatedly activated during lactate perfusion. This study provides new insights into the cellular mechanisms by which lactate, acting via a membrane receptor, contributes to the memory formation process.

The Protective Effect of Melatonin Against Age-Associated, Sarcopenia-Dependent Tubular Aggregate Formation, Lactate Depletion, and Mitochondrial Changes.

To gain insight into the mechanism of sarcopenia and the protective effect of melatonin, the gastrocnemius muscles of young (3-4 months), early-aged (12 months), and old-aged (24 months) wild-type C57BL/6J female mice were examined by magnetic resonance and microscopy. Locomotor activity, lactate production, and nuclear apoptosis were also assessed. The results support the early onset of sarcopenia at 12 months of age, with reduction of muscle fiber number, muscle weight/body weight ratio, lactate, and locomotor activity. Lipid droplet infiltration and autophagosomes were also detected. These changes driven little effects on the early-aged muscle, but they got worse in old-aged animals by the progressive damage of the muscle. Old-aged muscle showed a reduction of the mitochondrial number, a destruction of the mitochondrial cristae, and swelling. Tubular aggregates and nucleic acid fragmentation were the most striking findings in old-aged muscle, reflecting a broad damage with loss of autophagy efficacy. Oral melatonin administration conserved the normal muscular architecture, weight, muscle fiber number, and activity in the old age; it stimulated lactate production, prevented mitochondrial damage and tubular aggregates, and reduced the percentage of apoptotic nuclei in aged muscles. Altogether, gastrocnemius muscle showed age-mediated signs of sarcopenia that were reduced by melatonin treatment.

Bcl-2 or Bcl-xL Overexpresssion Affects Both Lactic Fermentation and Mitochondrial Metabolism in Growing Pro-Lymphocytes

It is now well established that shifts in energy metabolism are associated with cancer development and progression. The most studied of these phenomena is the Warburg effect, which corresponds to an increase of anaerobic glycolysis vs mitochondrial oxidative phosphorylation to produce energy for cellular processes. However, the mechanisms related to these metabolic switches are still a matter of debate. Bcl-2 family proteins contain both pro- (e.g. Bax), and anti-apoptotic (e.g. Bcl-2 and Bcl-xL) members which are respectively encoded by tumor suppressors and proto-oncogenes. Up-regulation of the anti-apoptotic proteins Bcl-2 and Bcl-xL have been associated with Non-Hodgkin's lymphoma; and certain studies indicate that Bcl-2 family proteins play a role in the regulation of energy metabolism. However, the metabolic phenotypes associated directly with an overexpression of Bcl-2 or Bcl-xL (Bcl-2/xL) remain to be defined at the whole cell level. We recently applied a 1H- and 13C-NMR-based approach on growing Bcl-2/xL-overexpressing pro-lymphocyte B cell lines to determine their respective metabolic trends. The comparison of 1H-NMR spectra obtained from whole cell metabolites extractions indicate that significant metabolic changes are induced by Bcl-2/xL-overexpression; more particularly at the level of the intracellular fumarate pool. Also, both lactate production and glucose consumption fluxes are stimulated by Bcl-2/xL overexpression. This phenomenon is associated with an increase of glycolytic/fermentative (LDH and GAPDH enzyme activity) and mitochondrial (Citrate synthase activity) markers; but only when Bcl-xL (and not Bcl-2) is overexpressed. These data suggest that Bcl-2 and Bcl-xL expression levels may play an active role in the stimulation of lactic fermentation commonly observed in blood cancer cells; and that Bcl-2 and Bcl-xL-mediated stimulation of lactate production are the results of different molecular transduction mechanisms.

IL-1/inhibitory κB kinase ε–induced glycolysis augment epithelial effector function and promote allergic airways disease

Emerging studies suggest that enhanced glycolysis accompanies inflammatory responses. Virtually nothing is known about the relevance of glycolysis in patients with allergic asthma. We sought to determine whether glycolysis is altered in patients with allergic asthma and to address its importance in the pathogenesis of allergic asthma. We examined alterations in glycolysis in sputum samples from asthmatic patients and primary human nasal cells and used murine models of allergic asthma, as well as primary mouse tracheal epithelial cells, to evaluate the relevance of glycolysis. In a murine model of allergic asthma, glycolysis was induced in the lungs in an IL-1-dependent manner. Furthermore, administration of IL-1β into the airways stimulated lactate production and expression of glycolytic enzymes, with notable expression of lactate dehydrogenase Aoccurring in the airway epithelium. Indeed, exposure of mouse tracheal epithelial cells to IL-1β or IL-1α resulted in increased glycolytic flux, glucose use, expression of glycolysis genes, and lactate production. Enhanced glycolysis was required for IL-1β- or IL-1α-mediated proinflammatory responses and the stimulatory effects of IL-1β on house dust mite (HDM)-induced release of thymic stromal lymphopoietin and GM-CSF from tracheal epithelial cells. Inhibitor of κB kinase ε was downstream of HDM or IL-1β and required for HDM-induced glycolysis and pathogenesis of allergic airways disease. Small interfering RNA ablation of lactate dehydrogenase Aattenuated HDM-induced increases in lactate levels and attenuated HDM-induced disease. Primary nasal epithelial cells from asthmatic patients intrinsically produced more lactate compared with cells from healthy subjects. Lactate content was significantly higher in sputum supernatants from asthmatic patients, notably those with greater than 61% neutrophils. Apositive correlation was observed between sputum lactate and IL-1β levels, and lactate content correlated negatively with lung function. Collectively, these findings demonstrate that IL-1β/inhibitory κB kinase ε signaling plays an important role in HDM-induced glycolysis and pathogenesis of allergic airways disease.

Bcl-2 or Bcl-xL Overexpression Stimulates Lactic Fermentation without Affecting Whole Cell Respiration

It is now well established that shifts in energy metabolism are associated with cancer development and progression. The most studied of these phenomena is the Warburg effect, which corresponds to an increase of anaerobic glycolysis vs mitochondrial oxidative phosphorylation to produce energy for cellular processes. However, the mechanisms related to these metabolic switches are still a matter of debate. Bcl-2 family proteins contain both pro- (e.g. Bax), and anti-apoptotic (e.g. Bcl-2 and Bcl-xL) members which are respectively encoded by tumor suppressors and proto-oncogenes. Up-regulation of the anti-apoptotic proteins Bcl-2 and Bcl-xL have been associated with Non-Hodgkin's lymphoma; and certain studies indicate that Bcl-2 family proteins play a role in the regulation of energy metabolism. However, the molecular players involved in this regulation are still to be defined. We recently observed that Bcl-2 or Bcl-xL (Bcl-2/xL) overexpression led to a significant increase of lactate production rates in a mouse pro-lymphocyte B cell line. However, both lactate production and glucose consumption fluxes are stimulated by Bcl-2/xL overexpression. Also, basal, uncoupled and non-coupled whole cell respiration remain similar in the 3 cell lines. Taken together, these results suggest that the fermentative component, but not the oxidative component, of carbohydrate metabolism is stimulated in these genetic contexts. This phenomenon is associated with an increase of glycolytic/fermentative (LDH and GAPDH enzyme activity) and mitochondrial (Citrate synthase activity) markers; but only when Bcl-xL (and not Bcl-2) is overexpressed. These data suggest that Bcl-2 and Bcl-xL expression levels may play an active role in the stimulation of lactic fermentation commonly observed in blood cancer cells; and that Bcl-2 and Bcl-xL-mediated stimulation of lactate production are the results of different molecular mechanisms.

Shikonin regulates C-MYC and GLUT1 expression through the MST1-YAP1-TEAD1 axis

The general mechanism underlying the tumor suppressor activity of the Hippo signaling pathway remains unclear. In this study, we explore the molecular mechanisms connecting the Hippo signaling pathway with glucose metabolism. We have found that two key regulators of glycolysis, C-MYC and GLUT1, are targets of the Hippo signaling pathway in human leukemia cells.Our results revealed that activation of MST1 by the natural compound shikonin inhibited the expression of GLUT1 and C-MYC. Furthermore, RNAi experiments confirmed the regulation of GLUT1 and C-MYC expression via the MST1-YAP1-TEAD1 axis. Surprisingly, YAP1 was found to positively regulate C-MYC mRNA levels in complex with TEAD1, while it negatively regulates C-MYC levels in cooperation with MST1. Hence, YAP1 serves as a rheostat for C-MYC, which is regulated by MST1. In addition, depletion of MST1 stimulates lactate production, whereas the specific depletion of TEAD1 has an opposite effect. The inhibition of lactate production and cellular proliferation induced by shikonin also depends on the Hippo pathway activity. Finally, a bioinformatic analysis revealed conserved TEAD-binding motifs in the C-MYC and GLUT1 promoters providing another molecular data supporting our observations.In summary, regulation of glucose metabolism could serve as a new tumor suppressor mechanism orchestrated by the Hippo signaling pathway.

Cerebral Lactate Metabolism After Traumatic Brain Injury.

Cerebral energy dysfunction has emerged as an important determinant of prognosis following traumatic brain injury (TBI). A number of studies using cerebral microdialysis, positron emission tomography, and jugular bulb oximetry to explore cerebral metabolism in patients with TBI have demonstrated a critical decrease in the availability of the main energy substrate of brain cells (i.e., glucose). Energy dysfunction induces adaptations of cerebral metabolism that include the utilization of alternative energy resources that the brain constitutively has, such as lactate. Two decades of experimental and human investigations have convincingly shown that lactate stands as a major actor of cerebral metabolism. Glutamate-induced activation of glycolysis stimulates lactate production from glucose in astrocytes, with subsequent lactate transfer to neurons (astrocyte-neuron lactate shuttle). Lactate is not only used as an extra energy substrate but also acts as a signaling molecule and regulator of systemic and brain glucose use in the cerebral circulation. In animal models of brain injury (e.g., TBI, stroke), supplementation with exogenous lactate exerts significant neuroprotection. Here, we summarize the main clinical studies showing the pivotal role of lactate and cerebral lactate metabolism after TBI. We also review pilot interventional studies that examined exogenous lactate supplementation in patients with TBI and found hypertonic lactate infusions had several beneficial properties on the injured brain, including decrease of brain edema, improvement of neuroenergetics via a "cerebral glucose-sparing effect," and increase of cerebral blood flow. Hypertonic lactate represents a promising area of therapeutic investigation; however, larger studies are needed to further examine mechanisms of action and impact on outcome.

Bcl-2 OR Bcl-xL Overexpression Stimulates both Oxidative and Fermentative Components of Carbohydrate Metabolism

It is now well established that shifts in energy metabolism are associated with cancer development and progression. The most studied of these phenomena is the Warburg effect, which corresponds to an increase of anaerobic glycolysis vs mitochondrial oxidative phosphorylation to produce energy for cellular processes. However, the mechanisms related to these metabolic switches are still a matter of debate. Bcl-2 family proteins contain both pro- (e.g. Bax), and anti-apoptotic (e.g. Bcl-2 and Bcl-xL) members which are respectively encoded by tumor suppressors and proto-oncogenes. Up-regulation of the anti-apoptotic proteins Bcl-2 and Bcl-xL have been associated with Non-Hodgkin's lymphoma; and certain studies indicate that Bcl-2 family proteins play a role in the regulation of energy metabolism. However, the molecular players involved in this regulation are still to be defined. We recently observed that Bcl-2 or Bcl-xL (Bcl-2/xL) overexpression led to a significant increase lactate production rates in a mouse pro-lymphocyte B cell line. However, both lactate production and glucose consumption fluxes are stimulated by Bcl-2/xL overexpression: suggesting that both oxidative and fermentative carbohydrate metabolism are stimulated in these genetic contexts. This phenomenon was associated with a stimulation of the lactate dehydrogenase (LDH) enzyme specific activity; but only when Bcl-xL (and not Bcl-2) was overexpressed. These data suggest that Bcl-2 and Bcl-xL expression levels may play an active role in the stimulation of lactic fermentation commonly observed in blood cancer cells; and that Bcl-2 and Bcl-xL-mediated stimulation of lactate production are the results of different molecular mechanisms.

IL-1β irreversibly inhibits tenogenic differentiation and alters metabolism in injured tendon-derived progenitor cells in vitro

Tendon injuries are common, and the damaged tendon often turns into scar tissue and never completely regains the original biomechanical properties. Previous studies have reported that the mRNA levels of inflammatory cytokines such as IL-1β are remarkably up-regulated in injured tendons. To examine how IL-1β impacts tendon repair process, we isolated the injured tendon-derived progenitor cells (inTPCs) from mouse injured Achilles tendons and studied the effects of IL-1β on the inTPCs in vitro. IL-1β treatment strongly reduced expression of tendon cell markers such as scleraxis and tenomodulin, and also down-regulated gene expression of collagen 1, collagen 3, biglycan and fibromodulin in inTPCs. Interestingly, IL-1β stimulated lactate production with increases in hexokinase II and lactate dehydrogenase expression and a decrease in pyruvate dehydrogenase. Inhibition of lactate production restored IL-1β-induced down-regulation of collagen1 and scleraxis expression. Furthermore, IL-1β significantly inhibited adipogenic, chondrogenic and osteogenic differentiation of inTPCs. Interestingly, inhibition of tenogenic and adipogenic differentiation was not recovered after removal of IL-1β while chondrogenic and osteogenic differentiation abilities were not affected. These findings indicate that IL-1β strongly and irreversibly impairs tenogenic potential and alters glucose metabolism in tendon progenitors appearing in injured tendons. Inhibition of IL-1β may be beneficial for maintaining function of tendon progenitor cells during the tendon repair process.

The effect of lysophosphatidic acid during in vitro maturation of bovine cumulus-oocyte complexes: cumulus expansion, glucose metabolism and expression of genes involved in the ovulatory cascade, oocyte and blastocyst competence.

BackgroundIn the cow, lysophosphatidic acid (LPA) acts as an auto-/paracrine factor, through its receptors LPAR1-4, on oocytes and cumulus cells during in vitro maturation (IVM). The aim of the present work was to determine the effect of LPA during IVM of bovine oocytes on: 1) oocyte maturation; 2) apoptosis of COCs; 3) expression of genes involved in developmental competence and apoptosis in bovine oocytes and subsequent blastocysts; 4) cumulus expansion and expression of genes involved in the ovulatory cascade in cumulus cells; 5) glucose metabolism and expression of genes involved in glucose utilization in cumulus cells; 6) cleavage and blastocyst rates on Day 2 and Day 7 of in vitro culture, respectively.MethodsCumulus-oocyte complexes (COCs) were matured in vitro in the presence or absence of LPA (10−5M) for 24h. Following maturation, we determined: oocyte maturation stage, cumulus expansion, COCs apoptosis and glucose and lactate levels in the maturation medium. Moreover, COCs were either used for gene expression analysis or fertilized in vitro. The embryos were cultured until Day 7 to assess cleavage and blastocyst rates. Oocytes, cumulus cells and blastocysts were used for gene expression analysis.ResultsSupplementation of the maturation medium with LPA enhanced oocyte maturation rates and stimulated the expression of developmental competence-related factors (OCT4, SOX2, IGF2R) in oocytes and subsequent blastocysts. Moreover, LPA reduced the occurrence of apoptosis in COCs and promoted an antiapoptotic balance in the transcription of genes involved in apoptosis (BAX and BCL2) either in oocytes or blastocysts. LPA increased glucose uptake by COCs via augmentation of GLUT1 expression in cumulus cells as well as stimulating lactate production via the enhancement of PFKP expression in cumulus cells. LPA did not affect cumulus expansion as visually assessed, however, it stimulated upstream genes of cumulus expansion cascade, AREG and EREG.ConclusionsSupplementation of the maturation medium with LPA improves oocyte maturation rates, decreases extent of apoptosis in COCs and sustains the expression of developmental competence related factors during oocyte maturation and subsequently affects gene expression profile at the blastocyst stage. We also demonstrate that LPA directs glucose metabolism toward the glycolytic pathway during IVM.

Dose-dependent effects of caffeine in human Sertoli cells metabolism and oxidative profile: relevance for male fertility.

Caffeine is a widely consumed substance present in several beverages. There is an increasing consumption of energetic drinks, rich in caffeine, among young individuals in reproductive age. Caffeine has been described as a modulator of cellular metabolism. Hence, we hypothesized that it alters human Sertoli cells (hSCs) metabolism and oxidative profile, which are essential for spermatogenesis. For that purpose, hSCs were cultured with increasing doses of caffeine (5, 50, 500 μM). Caffeine at the lowest concentrations (5 and 50 μM) stimulated lactate production, but only hSCs exposed to 50 μM showed increased expression of glucose transporters (GLUTs). At the highest concentration (500 μM), caffeine stimulated LDH activity to sustain lactate production. Notably, the antioxidant capacity of hSCs decreased in a dose-dependent manner and SCs exposed to 500 μM caffeine presented a pro-oxidant potential, with a concurrent increase of protein oxidative damage. Hence, moderate consumption of caffeine appears to be safe to male reproductive health since it stimulates lactate production by SCs, which can promote germ cells survival. Nevertheless, caution should be taken by heavy consumers of energetic beverages and food supplemented with caffeine to avoid deleterious effects in hSCs functioning and thus, abnormal spermatogenesis.

Perifornical hypothalamic orexin and serotonin modulate the counterregulatory response to hypoglycemic and glucoprivic stimuli.

Previous reports suggested an important role for serotonin (5-hydroxytryptamine [5-HT]) in enhancing the counterregulatory response (CRR) to hypoglycemia. To elucidate the sites of action mediating this effect, we initially found that insulin-induced hypoglycemia stimulates 5-HT release in widespread forebrain regions, including the perifornical hypothalamus (PFH; 30%), ventromedial hypothalamus (34%), paraventricular hypothalamus (34%), paraventricular thalamic nucleus (64%), and cerebral cortex (63%). Of these, we focused on the PFH because of its known modulation of diverse neurohumoral and behavioral responses. In awake, behaving rats, bilateral PFH glucoprivation with 5-thioglucose stimulated adrenal medullary epinephrine (Epi) release (3,153%) and feeding (400%), while clamping PFH glucose at postprandial brain levels blunted the Epi response to hypoglycemia by 30%. The PFH contained both glucose-excited (GE) and glucose-inhibited (GI) neurons; GE neurons were primarily excited, while GI neurons were equally excited or inhibited by 5-HT at hypoglycemic glucose levels in vitro. Also, 5-HT stimulated lactate production by cultured hypothalamic astrocytes. Depleting PFH 5-HT blunted the Epi (but not feeding) response to focal PFH (69%) and systemic glucoprivation (39%), while increasing PFH 5-HT levels amplified the Epi response to hypoglycemia by 32%. Finally, the orexin 1 receptor antagonist SB334867A attenuated both the Epi (65%) and feeding (47%) responses to focal PFH glucoprivation. Thus we have identified the PFH as a glucoregulatory region where both 5-HT and orexin modulate the CRR and feeding responses to glucoprivation.