LDH-B Activity Research Articles

Targeting Lactate Dehydrogenase-B as a Strategy to Fight Cancer: Identification of Potential Inhibitors by In Silico Analysis and In Vitro Screening.

Lactate dehydrogenase (LDH) is an enzyme that catalyzes the reversible conversion of lactate to pyruvate while reducing NAD+ to NADH (or oxidizing NADH to NAD+). Due to its central role in the Warburg effect, LDH-A isoform has been considered a promising target for treating several types of cancer. However, research on inhibitors targeting LDH-B isoform is still limited, despite the enzyme's implication in the development of specific cancer types such as breast and lung cancer. This study aimed to identify small-molecule compounds that specifically inhibit LDH-B. Our in silico analysis identified eight commercially available compounds that may affect LDH-B activity. The best five candidates, namely tucatinib, capmatinib, moxidectin, rifampicin, and acetyldigoxin, were evaluated further in vitro. Our results revealed that two compounds, viz., tucatinib and capmatinib, currently used for treating breast and lung cancer, respectively, could also act as inhibitors of LDH-B. Both compounds inhibited LDH-B activity through an uncompetitive mechanism, as observed in in vitro experiments. Molecular dynamics studies further support these findings. Together, our results suggest that two known drugs currently being used to treat specific cancer types may have a dual effect and target more than one enzyme that facilitates the development of these types of cancers. Furthermore, the results of this study could be used as a new starting point for identifying more potent and specific LDH-B inhibitors.

Nrf2 Activation Enhances Muscular MCT1 Expression and Hypoxic Exercise Capacity.

Skeletal muscle is the major producing and metabolizing site of lactic acid. A family of monocarboxylate transporter (MCT) proteins, especially MCT1 and MCT4, are involved in the lactate-pyruvate exchange and metabolism. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a pivotal coordinator of antioxidant response and energy metabolism, and has been reported to associate with the physiological functions of the skeletal muscle. In this study, C57BL/6 J mice were administrated with an Nrf2 activator, sulforaphane (SFN) before taking incremental treadmill exercise to exhaustion under hypoxia; then the effects of SFN on exercise endurance and molecular/biochemical makers of the skeletal muscle were evaluated. The results indicated that SFN pretreatment enhanced the exercise endurance under hypoxia. SFN not only increased the expressions of antioxidant genes and activity of antioxidant enzymes, but also significantly increased the mRNA and protein levels of MCT1 and CD147, but not MCT4. Moreover, the expressions of LDH-B and LDH activity of converting lactate into pyruvate, as well as citrate synthase activity were significantly higher, whereas the LDH activity of converting pyruvate into lactate and blood lactate level were remarkably lower in the SFN-exercise mice than those of the phosphate-buffered saline-exercise group. Furthermore, Atf3Δzip2 (the alternatively spliced isoform of activating transcription factor-3) mRNA was increased by the exercise and further potentiated by SFN. These results show, for the first time, that SFN increases MCT1 expression in the skeletal muscle under acute hypoxic exercise and suggest that Nrf2 activation is a promising strategy to enhance exercise performance under hypoxia.

Meat Color Stability of Ovine Muscles Is Related to Glycolytic Dehydrogenase Activities.

The relationship between glycolytic dehydrogenase, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH), lactic dehydrogenase (LDH), and meat color stability was studied in this study using ovine muscle. Three different ovine muscles, including M. longissimus lumborum (LL), M. semimembranosus (SM), and M. psoas major (PM), were obtained (n = 10, respectively), and then displayed for 7 days at 4 °C. The LL and SM muscle had higher surface redness, higher (P < 0.05) GAPDH activity, nicotinamide adenine dinucleotide (NADH) content, and lower (P < 0.05) LDH-B activity than PM muscles during display. The PM muscle had the worst color stability and lowest NADH content. These results suggest that variation in color stability of physiologically different muscles may be affected by glycolysis dehydrogenases. Comparatively, our data showed that GAPDH may play a more important role than LDH-B to maintain meat color stability.

Age related rise in lactate and its correlation with lactate dehydrogenase (LDH) status in post-mitochondrial fractions isolated from different regions of brain in mice

Rise in brain lactate is the hallmark of ageing. Separate studies report that ageing is associated with elevation of lactate level and alterations of lactate dehydrogenase (LDH)-A/B mRNA-expression-ratio in cerebral cortex and hippocampus. However, age related lactate rise in brain and its association with LDH status and their brain regional variations are still elusive. In the present study, level of lactate, LDH (A and B) activity and LDH-A expression were evaluated in post-mitochondrial fraction of tissues isolated from four different brain regions (cerebral cortex, hippocampus, substantia nigra and cerebellum) of young and aged mice. Lactate levels elevated in four brain regions with maximum rise in substantia nigra of aged mice. LDH-A protein expression and its activity decreased in cerebral cortex, hippocampus and substantia nigra without any changes of these parameters in cerebellum of aged mice. LDH-B activity decreased in hippocampus, substantia nigra and cerebellum whereas its activity remains unaltered in cerebral cortex of aged mice. Accordingly, the ratio of LDH-A/LDH-B-activity remains unaltered in hippocampus and substantia nigra, decreased in cerebral cortex and increased in cerebellum. Therefore, rise of lactate in three brain regions (cerebral cortex, hippocampus, substantia nigra) appeared to be not correlated with the alterations of its regulatory enzymes activities in these three brain regions, rather it supports the fact of involvement of other mechanisms, like lactate transport and/or aerobic/anaerobic metabolism as the possible cause(s) of lactate rise in these three brain regions. The increase in LDH-A/LDH-B-activity-ratio appeared to be positively correlated with elevated lactate level in cerebellum of aged mice. Overall, the present study indicates that the mechanism of rise in lactate in brain varies with brain regions where LDH status plays an important role during ageing.

H2S-induced S-sulfhydration of lactate dehydrogenase a (LDHA) stimulates cellular bioenergetics in HCT116 colon cancer cells

Cystathionine-β-synthase (CBS) is upregulated and hydrogen sulfide (H2S) production is increased in colon cancer cells. The functional consequence of this response is stimulation of cellular bioenergetics and tumor growth and proliferation. Lactate dehydrogenase A (LDHA) is also upregulated in various colon cancer cells and has been previously implicated in tumor cell bioenergetics and proliferation. In the present study, we sought to determine the potential interaction between the H2S pathway and LDH activity in the control of bioenergetics and proliferation of colon cancer, using the colon cancer line HCT116. Low concentrations of GYY4137 (a slow-releasing H2S donor) enhanced mitochondrial function (oxygen consumption, ATP production, and spare respiratory capacity) and glycolysis in HCT116 cells. SiRNA-mediated transient silencing of LDHA attenuated the GYY4137-induced stimulation of mitochondrial respiration, but not of glycolysis. H2S induced the S-sulfhydration of Cys163 in recombinant LDHA, and stimulated LDHA activity. The H2S-induced stimulation of LDHA activity was absent in C163A LDHA. As shown in HCT116 cell whole extracts, in addition to LDHA activation, GYY4137 also stimulated LDHB activity, although to a smaller extent. Total cellular lactate and pyruvate measurements showed that in HCT116 cells LDHA catalyzes the conversion of pyruvate to lactate. Total cellular lactate levels were increased by GYY4137 in wild-type cells (but not in cells with LDHA silencing). LDHA silencing sensitized HCT116 cells to glucose oxidase (GOx)-induced oxidative stress; this was further exacerbated with GYY4137 treatment. Treatment with low concentrations of GYY4137 (0.3mM) or GOx (0.01U/ml) significantly increased the proliferation rate of HCT116 cells; the effect of GOx, but not the effect of GYY4137 was attenuated by LDHA silencing. The current report points to the involvement of LDHA in the stimulatory effect of H2S on mitochondrial respiration in colon cancer cells and characterizes some of the functional interactions between LDHA and H2S-stimulated bioenergetics under resting conditions, as well as during oxidative stress.

Lactate dehydrogenase regulation in aged skeletal muscle: Regulation by anabolic steroids and functional overload

Aging alters the skeletal muscle response to overload-induced growth. The onset of functional overload is characterized by increased myoblast proliferation and an altered muscle metabolic profile. The onset of functional overload is associated with increased energy demands that are met through the interconversion of lactate and pyruvate via the activity of lactate dehydrogenase (LDH). Testosterone targets many of the processes activated at the onset of functional overload. However, the effect of aging on this metabolic plasticity at the onset of functional overload and how anabolic steroid administration modulates this response is not well understood. The purpose of this study was to determine if aging would alter overload-induced LDH activity and expression at the onset of functional overload and whether anabolic steroid administration would modulate this response. Five-month and 25-month male Fischer 344xF1 BRN were given nandrolone decanoate (ND) or sham injections for 14days and then the plantaris was functionally overloaded (OV) for 3days by synergist ablation. Aging reduced muscle LDH-A & LDH-B activity 70% (p<0.05). Aging also reduced LDH-A mRNA abundance, however there was no age effect on LDH-B mRNA abundance. In 5-month muscle, both ND and OV decreased LDH-A and LDH-B activity. However, there was no synergistic or additive effect. In 5-month muscle, ND and OV decreased LDH-A mRNA expression with no change in LDH-B expression. In 25-month muscle, ND and OV increased LDH-A and LDH-B activity. LDH-A mRNA expression was not altered by ND or OV in aged muscle. However, there was a main effect of OV to decrease LDH-B mRNA expression. There was also an age-induced LDH isoform shift. ND and OV treatment increased the “fast” LDH isoforms in aged muscle, whereas ND and OV increased the “slow” isoforms in young muscle. Our study provides evidence that aging alters aspects of skeletal muscle metabolic plasticity normally induced by overload and anabolic steroid administration.

Cited2 Is Required for the Maintenance of Glycolytic Metabolism in Adult Hematopoietic Stem Cells

Mammalian adult hematopoietic stem cells (HSCs) reside in the hypoxic bone marrow microenvironment and display a distinct metabolic phenotype compared with their progenitors. It has been proposed that HSCs generate energy mainly through anaerobic glycolysis in a pyruvate dehydrogenase kinase (Pdk)-dependent manner. Cited2 is an essential regulator for HSC quiescence, apoptosis, and function. Herein, we show that conditional deletion of Cited2 in murine HSCs results in elevated levels of reactive oxygen species, decreased cellular glutathione content, increased mitochondrial activity, and decreased glycolysis. At the molecular level, Cited2 deficiency significantly reduced the expression of genes involved in metabolism, such as Pdk2, Pdk4, and lactate dehydrogenases B and D (LDHB and LDHD). Cited2-deficient HSCs also exhibited increased Akt signaling, concomitant with elevated mTORC1 activity and phosphorylation of FoxOs. Further, inhibition of PI3/Akt, but not mTORC1, partially rescued the repression of Pdk4 caused by deletion of Cited2. Altogether, our results suggest that Cited2 is required for the maintenance of adult HSC glycolytic metabolism likely through regulating Pdk2, Pdk4, LDHB, LDHD, and Akt activity.

Role of lactate dehydrogenase in metmyoglobin reduction and color stability of different bovine muscles

The role of lactate dehydrogenase (LDH) in metmyoglobin reducing activity (MRA) and color stability of different bovine muscles was studied in two consecutive experiments. In experiment 1, three different bovine muscles – M. longissimus lumborum (LL), M. semimembranosus (SM), and M. psoas major (PM) – were obtained ( n = 7, respectively), cut into steaks, PVC packaged, and then displayed for 7 days at 1 °C. The LL was the most red over display time and had more ( P < 0.05) LDH-B activity (catalyzing toward NADH generation), LDH1 isoform expression, NADH, and higher ( P < 0.05) MRA than the other two muscles studied. The PM had the least color stability and lowest MRA. In experiment 2, LL steaks ( n = 8) were cut in half, one side syringe-injected with oxamate, and the other injected with distilled water. Inclusion of oxamate decreased ( P < 0.05) LDH-B activity, NADH, and a* values after 10 days display at 1 °C. These results suggest that variation in color stability of physiologically different muscles is regulated by different replenishment rates of NADH via different LDH isozymes.

Lactate dehydrogenase expression at the onset of altered loading in rat soleus muscle.

Both functional overload and hindlimb disuse induce significant energy-dependent remodeling of skeletal muscle. Lactate dehydrogenase (LDH), an important enzyme involved in anaerobic glycolysis, catalyzes the interconversion of lactate and pyruvate critical for meeting rapid high-energy demands. The purpose of this study was to determine rat soleus LDH-A and -B isoform expression, mRNA abundance, and enzymatic activity at the onset of increased or decreased loading in the rat soleus muscle. The soleus muscles from male Sprague-Dawley rats were functionally overloaded for up to 3 days by a modified synergist ablation or subjected to disuse by hindlimb suspension for 3 days. LDH mRNA concentration was determined by Northern blotting, LDH protein isoenzyme composition was determined by zymogram analysis, and LDH enzymatic activity was determined spectrophotometrically. LDH-A mRNA abundance increased by 372%, and LDH-B mRNA abundance decreased by 43 and 31% after 24 h and 3 days of functional overload, respectively, compared with that in control rats. LDH protein expression demonstrated a shift by decreasing LDH-B isoforms and increasing LDH-A isoforms. LDH-B activity decreased 80% after 3 days of functional overload. Additionally, LDH-A activity increased by 234% following 3 days of hindlimb suspension. However, neither LDH-A or LDH-B mRNA abundance was affected following 3 days of hindlimb suspension. In summary, the onset of altered loading induced a differential expression of LDH-A and -B in the rat soleus muscle, favoring rapid energy production. Long-term altered loading is associated with myofiber conversion; however, the rapid changes in LDH at the onset of altered loading may be involved in other physiological processes.

Nandrolone Deconate??s Effect on Lactate Dehydrogenase Expression in Aged Fast-Type Skeletal Muscle

1399 Aging is associated with a decreased plantaris muscle mass and glycolytic and oxidative enzyme activity. Lactate Dehydrogenase (LDH) is an important regulatory enzyme involved in anaerobic glycolysis, and catalyzes the interconversion of lactate to pyruvate. The mechanisms inducing differential LDH expression with advanced age are not well understood. PURPOSE: This study's purpose was to examine aging and anabolic steroid administrations effect on LDH activity and expression in fast-type skeletal muscle. METHODS: Eight 25-month old male Fischer 344XF1 Brown Norway rats were used in this study. Four rats were administered nandrolone deconate (ND), an anabolic steroid with a long biological half-life, every seven days and sacrificed at the end of 4 weeks. RESULTS: LDH-A and LDH-B activity was 71% (p< .001) and 69% (p< .001) lower in aged plantaris muscle compared to young plantaris muscle. LDH-A and LDH-B activity increased 31% (p< .01) and 33% (p< .01) respectively following ND administration when compared to age-matched controls not receiving steroid. LDH protein expression shifted towards the faster LDH isoforms following ND administration in aged plantaris muscle when compared to age-matched controls not receiving ND. CONCLUSIONS: In summary, age induced differential expression of LDH A&B in the rat plantaris muscle, which is partially reversed by ND administration. Supported by a grant from NSF/EPSCOR and NIH/BRIN

Nandrolone Deconateʼs Effect on Lactate Dehydrogenase Expression in Aged Fast-Type Skeletal Muscle

1399 Aging is associated with a decreased plantaris muscle mass and glycolytic and oxidative enzyme activity. Lactate Dehydrogenase (LDH) is an important regulatory enzyme involved in anaerobic glycolysis, and catalyzes the interconversion of lactate to pyruvate. The mechanisms inducing differential LDH expression with advanced age are not well understood. PURPOSE: This study's purpose was to examine aging and anabolic steroid administrations effect on LDH activity and expression in fast-type skeletal muscle. METHODS: Eight 25-month old male Fischer 344XF1 Brown Norway rats were used in this study. Four rats were administered nandrolone deconate (ND), an anabolic steroid with a long biological half-life, every seven days and sacrificed at the end of 4 weeks. RESULTS: LDH-A and LDH-B activity was 71% (p< .001) and 69% (p< .001) lower in aged plantaris muscle compared to young plantaris muscle. LDH-A and LDH-B activity increased 31% (p< .01) and 33% (p< .01) respectively following ND administration when compared to age-matched controls not receiving steroid. LDH protein expression shifted towards the faster LDH isoforms following ND administration in aged plantaris muscle when compared to age-matched controls not receiving ND. CONCLUSIONS: In summary, age induced differential expression of LDH A&B in the rat plantaris muscle, which is partially reversed by ND administration. Supported by a grant from NSF/EPSCOR and NIH/BRIN

The Developmental Expression of Taxon-specific Crystallins in the Duck Lens

The three crystallins, αB-crystallin, τ-crystallin/α-enolase and ε-crystallin/lactate dehydrogenase B are all stress induced proteins and may thus share common regulatory elements. However, no evidence was found for coordinate expression of these three genes during duck lens development. The αB- and α-enolase/τ-crystallin mRNAs accumulate with similar kinetics between day 12 and day 24 of embryonic development but differ in their epithelial versus fibre cell location; the LDH-B/ε-crystallin transcript shares its preferential location in the fibre cell with αB-crystallin but differs in its developmental pattern of expression. The accumulation of LDH-B/ε-crystallin mRNA in heart and lens followed a similar developmental pattern. In contrast, the α-enolase/τ-crystallin mRNA level in heart decreases while the level in lens rises. The LDH-B gene is used as a crystallin gene in duck but not in chicken. This species-specific difference may correlate with the difference in LDH-B activity between various chicken and duck tissues: the retina and pancreas in duck have significantly higher LDH-B activity than in chick, while heart, muscle, stomach, liver, intestine and kidney all have much higher LDH-B activity in chicken than in duck.

Developmental regulation of γ-crystallin gene expression in the lens

The role of lactate dehydrogenase (LDH) in metmyoglobin reducing activity (MRA) and color stability of different bovine muscles was studied in two consecutive experiments. In experiment 1, three different bovine muscles – M. longissimus lumborum (LL), M. semimembranosus (SM), and M. psoas major (PM) – were obtained (n = 7, respectively), cut into steaks, PVC packaged, and then displayed for 7 days at 1 °C. The LL was the most red over display time and had more (P < 0.05) LDH-B activity (catalyzing toward NADH generation), LDH1 isoform expression, NADH, and higher (P < 0.05) MRA than the other two muscles studied. The PM had the least color stability and lowest MRA. In experiment 2, LL steaks (n = 8) were cut in half, one side syringe-injected with oxamate, and the other injected with distilled water. Inclusion of oxamate decreased (P < 0.05) LDH-B activity, NADH, and a* values after 10 days display at 1 °C. These results suggest that variation in color stability of physiologically different muscles is regulated by different replenishment rates of NADH via different LDH isozymes.

Isozymes of l(+) LDH in Hymenolepis diminuta

1. 1. Two isozymes of l(+) lactate dehydrogenase in the parasitic helminth Hymenolepis diminuta (Cestoda) are demonstrated by starch-gel electrophoresis. 2. 2. LDH patterns exhibit tissue specificity and ontogenetic changes. LDH-A activity occurs in all tissues of the adult worm, but LDH-B activity is restricted to ovarian tissues.